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Title:
NITROGEN-CONTAINING AROMATIC HETEROCYCLIC LIGAND-METAL COMPLEXES AND THEIR USE FOR THE ACTIVATION OF HYDROGEN PEROXIDE AND DIOXYGEN IN THE REACTION OF ORGANIC COMPOUNDS
Document Type and Number:
WIPO Patent Application WO/1991/010634
Kind Code:
A1
Abstract:
Nitrogen-containing aromatic heterocyclic ligand-metal complexes and their use for the activation of hydrogen peroxide and dioxygen are disclosed. Processes whereby activated hydrogen peroxide or dioxygen are used to transform various organic substrates are also disclosed. In particular, processes for the conversion of methylenic carbons to carbonyls, for the dioxygenation of aryl olefins, acetylenes and aryl-$g(a)-diols, for the oxidation of alcohols and aldehydes and for the removal of mercaptans from gaseous streams and for the removal of hydrogen sulfide and/or mercaptans from liquid streams are disclosed.

Inventors:
SAWYER DONALD T (US)
SHEU CESHING (US)
SOBKOWIAK ANDRZEJ (US)
TUNG HUI-CHAN (US)
Application Number:
PCT/US1991/000147
Publication Date:
July 25, 1991
Filing Date:
January 08, 1991
Export Citation:
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Assignee:
TEXAS A & M UNIV SYS (US)
International Classes:
B01D53/14; C07C37/60; C07C45/28; C07C45/29; C07C45/33; C07C45/34; C07C45/36; C07C45/38; C07C45/39; C07C46/06; C07C51/16; C07C51/285; C07C245/08; C07C409/16; C07C409/18; C07D303/04; (IPC1-7): C07C45/34; C07C45/35; C07C45/36
Foreign References:
US4259527A1981-03-31
EP0266283A11988-05-04
Other References:
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol. 111, May 1989, D.H.R. BARTON, "Functionalization of Saturated Hydrocarbons", pages 7144-48.
NOUVEAU JOURNAL DECHIMIE, Vol. 10, July 1986, D.H.R. BARTON, "Functionalization of Saturated hydrocarbons", pages 387-398.
Attorney, Agent or Firm:
Evans, Barry (Morris & Safford 530 Fifth Avenu, New York NY, US)
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Claims:
WE CLAIM:
1. A process for the activation of dioxygen or hydrogen peroxide which comprises contacting dioxygen or hydrogen peroxide with a complex of formula (L)lM(0M)m(L,)n(A)p wherein: L and L' are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono or polysubstituted by C02", C02H, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono or polysubstituted by C02", C02H, alkyl or cycloalkyl; M is a transition metal cation; A is an anion; 1 is 1, 2, 3 or 4; m is 0 or 1; n is O, 1, 2, 3 or 4; and p is 0, 1, 2 or 3; under conditions suitable for said activation to take place, provided: (a) if dioxygen is to be activated (i) M is in its reduced state and L is at least monosubstituted by C02' or CO^ when M is Fe, and (ii) L is not quinolinolate or quinolinol when M is Fe and L is not pieolinate or picolinic acid when M is Mn or Co; and (b) if hydrogen peroxide is to be activated, L is not pyridine, bipyridine, quinolinolate or quinolinol when M is Fe and L is not picolinic acid or pieolinate when M is Mn or Co.
2. A process as recited in claim 1 wherein L and L' are the same or different and each is a ligand of formula wherein: R1 is hydrogen, C02* or C02H; R2 is hydrogen or alkyl; R3 is hydrogen, C02", C02H or pyridinyl; E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; and A is an anion of an organic or mineral acid or is a halogen anion.
3. A process as recited in claim 2 wherein L and L' are selected from the group consisting of pyrazine, imidazole, pieolinate, 2,6pyridine dicarboxylate, 2pyrazine carboxylate, 2,6pyrazine dicarboxylate, 2imidazole carboxylate and 2,5 imidazole dicarboxylate.
4. A process as recited in claim 3 wherein said complex is selected from the group consisting of and .
5. A process for the dioxygenation of an organic compound which comprises contacting said organic compound with a complex of formula (Dj fOMJ L'j AJp wherein: L and L1 are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono or polysubstituted by C02*, COjH, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono or polysubstituted by C02", COjH, alkyl or cycloalkyl; M is a transition metal cation; A is an anion; 1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, l, 2, 3 or 4; and p is 0, 1, 2 or 3; in the presence of dioxygen or hydrogen peroxide under conditions suitable for said dioxygenation to take place, provided: (a) if said contact is made in the presence of dioxygen, (i) M is in its reduced state and L is at least monosubstituted by CO,' or COjH when M is Fe, and (ii) L is not quinolinolate or quinolinol when M is Fe and L is not pieolinate or picolinic acid when M is Mn or Co; and (b) if said contact is made in the presence of hydrogen peroxide, L is not pyridine, bipyridine, quinolinolate or quinolinol when M is Fe and L is not picolinic acid or pieolinate when M is Mn or Co.
6. A process as recited in claim 5 wherein L and L* are the same or different and each is a ligand of formula wherein: R1 is hydrogen, C02" or C02H; R2 is hydrogen or alkyl; R3 is hydrogen, C02", COjH or pyridinyl; E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; and A is an anion of an organic or mineral acid or is a halogen anion.
7. A process for the oxygenation of an organic compound which comprises contacting said organic compound with a complex of formula (L)lM(OM)ll(L,)n(A) wherein: L and L1 are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono or polysubstituted by C02", COgH, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono or polysubstituted by C02", COjH, alkyl or cycloalkyl; M is a transition metal cation; A is an anion; 1 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1, 2 or 3; in the presence of dioxygen or hydrogen peroxide under conditions suitable for said oxygenation to take place, provided: (a) if said contact is made in the presence of dioxygen, (i) M is in its reduced state and L is at least monosubstituted by C02* or C02H when M is Fe, and (ii) L is not quinolinolate or quinolinol when M is Fe and L is not pieolinate or picolinic acid when M is Mn or Co; and (b) if said contact is made in the presence of hydrogen peroxide, L is not pyridine, bipyridine, quinolinolate or quinolinol when M is Fe and L is not picolinic acid or pieolinate when M is Mn or Co.
8. A process as recited in claim 7, wherein a methylenic carbon contained in said organic compound is converted to a carbonyl.
9. A process as recited in claim 7 wherein L and L' are the same or different and each is a ligand of formula wherein: R1 is hydrogen, C02" or COjH; R2 is hydrogen or alkyl; R3 is hydrogen, C02", C02H or pyridinyl; or E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; and A is an anion of an organic or mineral acid or is a halogen anion.
10. A process as recited in claim 9, wherein said organic compound is benzene which is oxygenated to phenol, said complex is Coπ(bpy)22+, said contact is made in the presence of hydrogen peroxide and said oxygenation is carried out in a solvent matrix comprising a 4:1 (molratio) acetonitrile/pyridine mixture.
11. A process for the conversion of an acetylene to an αdicarbonyl which comprises contacting said acetylene with a complex of ormula (L) iK(OK) m(L') n(h) p wherein: L and L* are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono or polysubstituted by C02", C02H, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono or polysubstituted by C02", COjH, alkyl or cycloalkyl; M is a transition metal cation; A is an anion; 1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, l, 2 or 3; in the presence of dioxygen or hydrogen peroxide under conditions suitable for said conversion to take place, provided: (a) if said contact is made in the presence of dioxygen, (i) M is in its reduced state and L is at least monosubstituted by C02* or CO^R when M is Fe, and (ii) L is not quinolinolate or quinolinol when M is Fe and L is not pieolinate or picolinic acid when M is Mn or Co; and (b) if said contact is made in the presence of hydrogen peroxide, L is not pyridine, bipyridine, quinolinolate or quinolinol when M is Fe and L is not picolinic acid or pieolinate when M is Mn or Co.
12. A process as recited in claim 11 wherein L and L' are the same or different and each is a ligand of formula wherein: R1 is hydrogen, C02* or COjH; R2 is hydrogen or alkyl; R3 is hydrogen, C02", COjH or pyridinyl; or E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; and A is an anion of an organic or mineral acid or is a halogen anion.
13. A process for the conversion of an aryl olefin to an aldehyde or a ketone which comprises contacting said olefin with a complex of formula (l.) lK(aa)m(L, ) n(k) p wherein: L and L' are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono or polysubstituted by C02", COjH, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono or polysubstituted by C02", COgH, alkyl or cycloalkyl; M is a transition metal cation; A is an anion or a molecule of solvation; 1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1, 2 or 3; in the presence of dioxygen or hydrogen peroxide under conditions suitable for said conversion to take place, provided: (a) if said contact is made in the presence of dioxygen, (i) M is in its reduced state and L is at least monosubstituted by C02" or COjH when M is Fe, and (ii) L is not quinolinolate or quinolinol when M is Fe and L is not pieolinate or picolinic acid when M is Mn or Co; and (b) if said contact is made in the presence of hydrogen peroxide, L is not pyridine, bipyridine, quinolinolate or quinolinol when M is Fe and L is not picolinic acid or pieolinate when M is Mn or Co.
14. A process as recited in claim 13 wherein L and L' are the same or different and each is a ligand of formula wherein: R1 is hydrogen, C02" or COgH; R2 is hydrogen or alkyl; R3 is hydrogen, C02 CO^H or pyridinyl; or E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and £ is NH; and A is an anion of an organic or mineral acid or is a halogen anion.
15. A process for the conversion of an aryl αdiol to a carboxylic acid, a dicarboxylic acid or a dicarboxylic acid anhydride which comprises contacting said arylαdiol with a complex of formula (L)lM(OM)BI(L,)n(A)p wherein: L and L' are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono or polysubstituted by C02", COjH, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono or polysubstituted by C02', COjH, alkyl or cycloalkyl; M is a transition metal cation; A is an anion; 1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1, 2 or 3; in the presence of dioxygen or hydrogen peroxide under conditions suitable for said conversion to take place, provided: (a) if said contact is made in the presence of dioxygen, (i) M is in its reduced state and L is at least monosubstituted by C02* or C02H when M is Fe, and (ii) L is not quinolinolate or quinolinol when M is Fe and L is not pieolinate or picolinic acid when M is Mn or Co; and (b) if said contact is made in the presence of hydrogen peroxide, L is not pyridine, bipyridine, quinolinolate or quinolinol when M is Fe and L is not picolinic acid or pieolinate when M is Mn or Co.
16. A process as recited in claim 15 wherein L and L* are the same or different and each is a ligand of formula wherein: R1 is hydrogen, C02" or COjH; R2 is hydrogen or alkyl; R3 is hydrogen, C02*, COgH or pyridinyl; or E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; and A is an anion of an organic or mineral acid or is a halogen anion.
17. A process as recited in claim 8, wherein said organic compound is a compound of formula I CH (I) wherein R5 and R6 are the same or different and each is hydrogen, hydroxyl, alkyl or is aryl which is unsubstituted or mono or polysubstituted by halogen, N02, OH, loweralkyl or loweralkoxy, or R5 and R6 taken together form a CjC13 saturated or unsaturated ring, provided R5 and R6 are not both hydrogen and are not both hydroxyl, and is converted to a carbonyl compound of formula II K (II) wherein R5 and R6 are as defined above, wherein in said complex: L and L1 are the same or different and each is a ligand of formula wherein: R is hydrogen, C02" or C02H; R2 is hydrogen or alkyl; R3 is hydrogen, C02", C02H or pyridinyl; E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; M is a transition metal cation; A is an anion of an organic or mineral acid or a halogen anion; 1 is 1, 2, 3 or 4; m is 0 or 1; and n is 0, 1, 2, 3 or 4; p is 0, 1 or 2; provided that if said contact is made in the presence of dioxygen, then R1 and R3 are the same or different and each is C02* or COjH when M is Fe.
18. A process as claimed in claim 17, wherein said contact is made in the presence of dioxygen, R and R3 are the same or different and each is C02* or COjH and R5 and R6 are the same or different and each is alkyl or aryl.
19. A process as recited in claim 18, wherein said compound of formula I is cyclohexane, ethylbenzene, 2methylbutane or cyclohexene and said complex is Fen(DPAH)2.
20. A process as claimed in claim 17, wherein said compound of formula I is cyclohexane, said complex is Fe(PA)2, (PA)2FeOFe(PA)2, Fe(DPA) or (DPA)FeOFe(DPA) , said contact is made in the presence of hydrogen peroxide and said conversion is carried out in a solvent matrix comprising a 2:1 (molratio) pyridine/acetic acid mixture.
21. A process as claimed in claim 17 wherein said compound of formula I is nhexane, ethylbenzene, diphenylmethane, 2methylbutane, toluene, adamantane, cyclododecane or cyclohexene, said complex is Fe(PA)2, said contact is made in the presence of hydrogen peroxide and said conversion is carried out in a solvent matrix comprising a 2:1 (molratio) pyridine/acetic acid mixture.
22. A process as claimed in claim 17, wherein said compound of formula I is cyclohexane, 2 methylbutane, ethylbenzene, toluene, cyclohexene, cyclohenanol or benzyl alcohol, said contact is made in the presence of hydrogen peroxide, said complex is Con(bpy)22* and said conversion is carried out in a solvent matrix comprising a 4:1 (molratio) acetoni trile/pyridine mixture.
23. A process as recited in claim 12, wherein said acetylene is a compound of formula III K7 C≡≡≡C KB (III) wherein R7 and R8 are the same or different and each is H, halogen, alkyl or aryl which is unsubstituted or mono or polysubstituted by halogen, N02, OH, loweralkyl or loweralkoxy, and is converted to a compound of formula IV 0 0 R7 C — C RB (IV) wherein R7 and RB are defined as above, and wherein if said contact is made in the presence of dioxygen, then in said complex, R1 and R3 are the same or different and each is C02" or COjH when M is Fe.
24. A process as recited in claim 14, wherein said aryl olefin is a compound of formula V R10 R11 R9—C C—R i 2 ( V ) wherein RR12 are the same or not all the same and each is H, alkyl or is aryl which is unsubstituted or mono or polysubstituted by halogen, N02, OH, loweralkyl or loweralkoxy provided at least one of R9 R12 is aryl or substituted aryl, and is converted to compounds of formulae VI and VII C R 10 (VI) 11 C R 12 (VII) wherein R9R12 are defined as above, and wherein if siad contact is made in the presence of dioxygen, then in said complex, R and R3 are the same or different and each is C02* or C02H when M is Fe.
25. A process as recited in claim 16, wherein said arylαdiol is: (a) a compound of formula VIII wherein R13R16 are the same or not all the same and each is H, halogen, N02, CH, or is loweralkyl, aryl, arylloweralkyl, loweralkoxy or arylloweralkoxy each of which is unsubstituted or mono or polysubstituted by halogen, N02, OH, loweralkyl, loweralkoxy or NR17R18 wherein R17 and R18 are the same or different and each is H or loweralkyl, and is converted to compounds of formulae IX and X 1 3 1 * 1 5 1 6 H O C C O H ( I X ) wherein R13R16 are defined as above; or (b) a compound of formula XI OH OH R19 C C R20 (XI) wherein R19 and R20 are the same or different and each is aryl which is unsubstituted or mono or polysubstituted by halogen, N02, OH, loweralkyl, loweralkoxy or NRUR18 wherein R,r and R18 are the same or different and each is H or loweralkyl, and is converted to a compound of formulae XII, XIII or XIV 0 0 R 11 99 C " O H ( X I I ) H O I C' R 22 0D ( X I I I ) R 1 9 C 0 C R 2 0 ( X I V ) wherein R19 and R20 are defined as above, and wherein if said contact is made in the presence of dioxygen, then in said complex, R1 and R3 are the same or different and each is C02* or COgH when M is Fe.
26. A process for the oxidation of an alcohol or aldehyde which comprises contacting said alcohol or aldehyde with a complex of formula (L)1M(0M)|R(L')n(A)p wherein: L and L' are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono or polysubstituted by C02", COgH, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono or polysubstituted by C02*, COgH, alkyl or cycloalkyl; M is a transition metal cation; A is an anion or a molecule of solvation; 1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1, 2 or 3; in the presence of hydrogen peroxide or dioxygen under conditions suitable for said oxidation to take place, provided (a) if said contact is made in the presence of dioxygen, (i) M is in its reduced state and L is at least monosubstituted by C02* or C02H when M is Fe, and (ii) L is not quinolinolate or quinolinol when M is Fe and L is not pieolinate or picolinic acid when M is Mn or Co; and (b) if said contact is made in the presence of hydrogen peroxide, L is not pyridine, bipyridine, quinolinolate or quinolinol when M is Fe and L is not picolinic acid or pieolinate when M is Mn or Co.
27. A process as recited in claim 26, wherein said alcohol is: (a) a compound of formula XV wherein R21 and R23 are the same or different and each is loweralkyl and R22 is OH, and is converted to a compound of formula XVII wherein R21 and R23 are defined as above; or (b) a compound of the formula XVIII OH R24 CH ,24 (XVIII) wherein R24 and R25 are the same or different and each is hydrogen, alkyl or aryl which is unsubstituted or mono or polysubstituted by halogen, N02, loweralkyl or loweralkoxy, or R5 and R6 taken together form a C3C13 saturated or unsaturated ring provided R24 and R25 are not both hydrogen, can be converted to a compound of formula XIX R24 C i i R25 (XIX) wherein R24 and R25 are as defined above, wherein in said complex: L and L' are the same or different and each is a ligand of formula wherein: R is hydrogen, C02" or COjH; R2 is hydrogen or alkyl; R3 is hydrogen, C02*, C02H or pyridinyl; E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; M is a transition metal cation; A is an anion of an organic or mineral acid or a halogen anion; 1 is 1, 2, 3 or 4; m is 0 or 1; and n is 0, 1, 2, 3 or 4; p is 0, 1, 2 or 3, provided if said contact is made in the presence of dioxygen, R1 and R3 are the same or different and each is C02' or CO^H when M is Fe.
28. A process as claimed in claim 23, wherein said compound of formula III is diphenylacetylene, said complex is Fe(PA)2, said contact is made in the presence of hydrogen peroxide and said conversion is carried out in a solvent matrix comprising a 2:1 (molratio) pyridine/acetic acid mixture.
29. A process as claimed in claim 24, wherein said compound of formula V is cisstilbene, styrene or methylstyrene, said complex is Fe(PA)2, said contact is made in the presence of hydrogen peroxide and said conversion is carried out in a solvent matrix comprising a 2:1 (molratio) pyridine/acetic acid mixture.
30. A process as claimed in claim 25, wherein said compound of formula VIII is catechol, said compound of formula XI is the enol tautometer of benzoin, said complex is Fen(DPAH)2, said contact is made in the presence of dioxygen and said conversion is carried out in a solvent matrix comprising a 1.8:1 (molratio) pyridine/acetic acid mixture.
31. A process as claimed in claim 23, wherein said compound of formula III is diphenyl acetylene, said complex is Coπ(bpy)22*, said contact is made in the presence of hydrogen peroxide and said conversion is carried out in a solvent matrix comprising a 4:1 (molratio) acetonitrile/pyridine mixture.
32. A process as claimed in claim 24, wherein said compound of formula V is cisstilbene, said complex is Coπ(bpy)22+, said contact is made in the presence of hydrogen peroxide and said conversion is carried out in a solvent matrix comprising a 4:1 (mol ratio) acetonitrile/pyridine mixture.
33. A process as claimed in claim 27, wherein said compound of formula XV is 2,6 dimethylphenol, said compound of formula XVIII is cyclohexanol or benzyl alcohol, said complex is Cou(bpy)22+, said contact is made in the presence of hydrogen peroxide and said dioxygenation is carried out in a solvent matrix comprising a 4:1 (molratio) acetonitrile/pyridine mixture.
34. A process as recited in claim 26, wherein said aldehyde is a compound of formula XX R25 C(=0) H (XX) wherein R25 is aryl which is unsubstituted or mono or polysubstituted by halogen, N02, OH, loweralkyl or loweralkoxy, and is oxidized to a compound of formula XXI R25 C(0) OH (XXI) wherein Rj is defined as above and wherein in said complex L and L' are the same or different and each is a ligand of formula wherein: R1 is hydrogen, C02* or COjH; R2 is hydrogen or alkyl; R3 is hydrogen, C02", COgH or pyridinyl; or E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; and A is an anion of an organic or mineral acid or is a halogen anion.
35. A process as claimed in claim 34, wherein said compound of formula XX is benzaldehyde and is contacted with Con(bpy)22* in the presence of hydrogen peroxide and in a solvent matrix comprising a 4:1 (molratio) acetonitrile/pyridine mixture.
36. A process as recited in claim 23, wherein said contact is made in the presence of dioxygen, said compound of formula III is diphenylacetylene, said complex is Feπ(DPAH)2, and said conversion is carried out in a solvent matrix comprising a 1.8:1 (molratio) pyridine/acetic acid mixture.
37. A process as recited in claim 24, wherein said contact is made in the presence of dioxygen, said compound of formula V is cisstilbene, said complex is Feπ(DPAH)2, and said conversion is carried out in a solvent matrix comprising a 1.8:1 (molratio) pyridine/acetic acid mixture.
38. A process as claimed in claim 27, wherein said compound of formula XV is 2,6 dimethylphenol and is contacted with Co'^bpyjj2* in the presence of hydrogen peroxide and in a solvent matrix comprising a 4:1 (molratio) acetonitrite/pyridine mixture.
39. A process as claimed in claim 1, wherein M in said complex is Fe and said contact is made in a solvent matrix comprising a mixture of an aromatic heterocyclic solvent having at least one nitrogen atom and an organic or mineral acid wherein the ratio of said aromatic heterocyclic solvent to said acid in said mixture ranges from about 1:1 to about 4:1.
40. A process as claimed in claim 1, wherein M in said complex is Co and said contact is made in a solvent matrix comprising a mixture of a polar, aprotic, nonbasic solvent and an aromatic heterocyclic solvent having at least one nitrogen atom wherein the ratio of said polar, aprotic, nonbasic solvent to said aromatic heterocyclic solvent in said mixture ranges from about 6:1 to about 1:1.
41. A process as recited in claim 39, wherein said aromatic solvent is selected from the group consisting of pyridine, substituted pyridine, pyrazine, substituted pyrazine, pyrimidine, substituted pyrimidine, imidazole and substituted imidazole and said acid is selected from the group consisting of acetic acid, perchloric acid, hydrochloric acid and sulfuric acid.
42. A process as recited in claim 39, wherein said solvent matrix comprises a mixture of pyridine and acetic acid and wherein the ratio of pyridine to acetic acid in said mixture is about 2:1.
43. A process as recited in claim 40, wherein said solvent matrix comprises a mixture of acetonitrile and pyridine and wherein the ratio of acetonitrile to pyridine in said mixture is about 4:1.
44. A process as recited in claim 1, wherein said dioxygen is activated in the presence of a reductant.
45. A process as recited in claim 17, wherein said contact is made in the presence of dioxygen and a reductant.
46. A process as recited in claim 45, wherein said reductant is selected from the group consisting of hydrazine, 1,2diphenylhydrazine, benzyl mercaptan, hydrogen sulfide and cyclohexadiene.
47. A process as recited in claim 46, wherein said compound of formula I is cyclohexane, ethylbenzene or 2methylbutane, said complex is Feu(DPAH)2, said reductant is 1,2diphenylhydrazine and said contact is made in a solvent matrix comprising a 1.8:1 (molratio) pyridine/acetic acid mixture.
48. A process for removing a mercaptan from a gas stream or hydrogen sulfide or a mercaptan from a liquid stream which comprises contacting a gas stream containing a mercaptan or a liquid stream containing hydrogen sulfide or a mercaptan with a complex of formula (L)lM(QM)il(L,)ll(A)p wherein: L and L' are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono or polysubstituted by C02', COjH, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono or polysubstituted by C02", COgH, alkyl or cycloalkyl; M is a transition metal cation; A is an anion; 1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1, 2 or 3; in the presence of dioxygen under conditions suitable for the conversion of said hydrogen sulfide or said mercaptan to elemental sulfur or dialkyl disulfide, provided M in said complex is in its reduced state and L is at least monosubstituted by C02" or COgH when M is Fe.
49. A process as recited in claim 48 wherein L and L1 are the same or different and each is a ligand of formula wherein: R1 is C02" or COjH; R2 is hydrogen or alkyl; R3 is hydrogen, C02", CO^ or pyridinyl; E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R is attached are joined directly and E is NH; and A is an anion of an organic or mineral acid or a halogen anion.
50. The process as recited in claim 48, wherein said mercaptan is of formula RSH wherein R is loweralkyl, aryl or arylloweralkyl.
51. A complex of formula (L)lM(OM)1|(L«)n(A)p wherein: L and L' are the same or different and each is a ligand of formula wherein: R1 is hydrogen, C02* or C02H; R2 is hydrogen or alkyl; R3 is hydrogen, C02", CO^ or pyridinyl; E is CH, N, NH or CR4 wherein R4 is alkyl; Q is CK; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R1 is attached are joined directly and E is NH; M is a transition metal cation; A is an anion of an organic or mineral acid or a halogen anion; 1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1 or 2; excluding complexes wherein: L is pieolinate, M is Fe, 1 is 3 and m«n«p«=0; and L is pieolinate and M is Mn or Co.
52. A complex as recited in claim 51 wherein L and L* are selected from the group consisting of pyrazine, imidazole, pieolinate, 2,6pyridine dicarboxylate, 2pyrazine carboxylate, 2,6pyrazine dicarboxylate, 2imidazole carboxylate and 2,5 imidazole dicarboxylate.
53. A complex as recited in claim 51 wherein said transition metal is selected from the group consisting of Fe, Mn, Co, Ni, Cu or Ru.
54. A complex as recited in claim 51 wherein A is selected from the group consisting of C104", AcO', N03', F", Cl*, Br", I' or MeCN.
55. A complex as recited in claim 51 which is selected from the group consisting of H02C and.
Description:
NITROGM-CONTAINING AROMATIC HETEROCYCLIC LIGAND-METAL COMPLEXES AM ) THEIR USE FOR THE ACTIVATION OF HYDROGEN PEROXIDE AND DIOXYGEN IN THE REACTION OF ORGANIC COMPOUNDS

FIELD OF THE INVENTION This invention was made with government and private support, including the National Science Foundation under Grant CHE-8516247 , a Graduate Fellowship by the Welch Foundation under Grant A-1042 , and a Fellowship from the U. S . Air Force Institute of Technology Civilian Institute Program.

This invention pertains generally to organic ligand-metal complexes and their use in chemical reactions and more particularly to nitrogen-containing aromatic heterocyclic ligand-transition metal complexes and their use for the activation of dioxygen and/ or hydrogen peroxide for the ketonization of methylenic carbons, and the dioxygenation of acetylenes, olefins and α-aryldiols , and for the removal of mercaptans from gaseous streams and for the removal of hydrogen sulfide and/or mercaptans from liquid streams.

Several publications are referenced in this application by Arabic numerals within parentheses. Full citations for these references are found at the end of the specification immediately preceding the claims. The disclosures of these publications are incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.

BACKGROUND OF THE INVENTION

The conversion of methylenic carbons to ketones, e.g., the conversion of cyclohexane to cyclohexanone, is important in the manufacture of

useful synthetic materials. Indeed, cyclohexanone is the principal starting material in the synthesis of adipic acid which in turn is used to make nylon and dacron. In addition, the ability to dioxygenate organic substrates would afford numerous alternatives in the total synthesis of pharmaceuticals and biomolecules, e.g., antibiotics, steroids, hormones and the like. Thus, the utility and desirability of efficient and inexpensive methods for the conversion of methylenic carbons to ketones and for the dioxygenation of organic substrates are manifest.

Several reports (1-5) have described the selective transformation of methylenic groups (>CH 2 ) to ketones via four heterogeneous iron-dioxygen systems; (a) iron powder/sodium sulfide/0 2 , (b) Fe 3 0(OAc) 6 * 3.5 pyridine(py)/zinc dust/0 2 , (c) (py)«FeCl 2 /K0 2 (s), and (d) (py)<FeCl 2 /(0 2 + e' → 0 2 " ) in 4:1 pyridine/acetic acid. These systems are postulated to contain σ-bonded iron-carbon intermediates (6) with superoxide ion (0 2 ' * ) as the active form of reduced oxygen, which oxidizes the iron catalyst within the catalytic cycle. Pyridine is believed to be essential to the system as a trap for hydroxyl radical, thereby preventing Fenton chemistry. Acetic acid serves as a proton source to transform superoxide ion to hydroperoxyl radical (HOO * ) . However, these heterogeneous iron-dioxygen systems proved to be inefficient and resulted in the indirect production of hydrogen peroxide from superoxide ion. Other experiments with other iron complexes, or other solvent matrices, are reported to yield a spectrum of products that are characteristic of Fenton chemistry (OH) (4). In addition, it has been reported (7) that [Fe(MeCN) (C10<) 2 n anhydrous acetonitrile

activates excess HOOH for the dioxygenation of diphenylisobenzofuran, rubrene, acetylenes, cis- stilbene, and methyIsty ene. However, the system is essentially unreactive with saturated hydrocarbons, and the presence of basic ligands (H 2 0 or pyridine) causes the system to promote Fenton chemistry [Fe(II) + HOOH → Fe OH + "OH] (8) .

OBJECTS. FEATURES AND ADVANTAGES OF THE INVENTION It is therefore a general object of the invention to overcome the disadvantages described above by providing herein an efficient process ^or the activation of hydrogen peroxide or dioxygen.

It is another object of the invention to provide a process for the dioxygenation of an organic compound by activation of hydrogen peroxide or dioxygen.

It is a further object of the invention to provide a process for the ketonization of methylenic carbons in organic compounds, the oxidation of alcohols and aldehydes and the dioxygenation of acetylenes, olefins, arylolefins, acetylenes and aryl-α-diols by the activation of hydrogen peroxide.

It is another object of the invention to provide a process for the ketonization of methylenic carbons in organic compounds and the dioxygenation of acetylenes, olefins and aryl-α-diols by activation of dioxygen.

It is another object of the invention to provide a process for the removal of mercaptans from gaseous streams.

It is another object of the invention to provide a process for the removal of hydrogen sulfide and/or mercaptans from liquid streams.

It is yet another object of the invention to provide novel aromatic heterocyclic ligand-metal complexes for the activation of hydrogen peroxide and dioxygen. These and other objects, features and advantages of the invention will become apparent from the following description of the invention.

SUMMARY OF THE INVENTION The invention is broadly directed to a process for the activation of hydrogen peroxide or dioxygen which comprises contacting dioxygen or hydrogen peroxide with a complex of formula

( ) l M(O ) B ( , ) n (A) p wherein:

L and L' are the same or different and each is a 5 to 10 member aromatic heterocyclic ligand containing at least one nitrogen atom which heterocyclic ligand is unsubstituted or mono- or polysubstituted by C0 2 ", CO-^H, O", OH, alkyl, cycloalkyl or aryl which in turn is unsubstituted or mono- or polysubstituted by C0 2 ", CO j H, 0", OH, alkyl or cycloalkyl;

M is a transition metal cation; A is an anion;

1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1, 2 or 3; under conditions suitable for the activation to take place, provided that if dioxygen is to be activated, L is at least monosubstituted by C0 2 * or CO j H when M is Fe. In particular, L and L' are the same or different and each is a ligand of formula

wherein:

R 1 is hydrogen, C0 2 * or CO j H;

R 2 is hydrogen or alkyl;

R 3 is hydrogen, C0 2 ", CO j H or pyridinyl; or R 2 and R 3 joined together and taken with the other atoms in the ring form a quinoline ring which is unsubstituted or substituted in the 8-position by 0 " ;

E is CH, N, NH or CR 4 wherein R 4 is alkyl;

Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, £ and the carbon atom to which R 1 is attached are joined directly and E is NH;

H is a transition metal cation;

A is anion of an organic or mineral acid or is a halogen anion;

1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1 or 2; under conditions suitable for the activation to take place, provided that when dioxygen is to be activated, M in the complex is in its reduced state and R 1 and R 3 are the same or different and each is C0 2 " or CO j H when M is Fe.

The invention is also directed to a process for the dioxygenation of an organic compound which comprises contacting the organic compound with a complex of the formula described above in the presence of hydrogen peroxide or dioxygen under conditions suitable for the dioxygenation to take place, provided

that if the contact is made in the presence of dioxygen, then M in the complex is in its reduced state and L is at least monosubstituted by C0 2 * or CO g H when M is Fe. In another aspect, the invention is directed to a process for the oxygenation of an organic compound which comprises contacting the organic compound with a complex of the formula described above in the presence of hydrogen peroxide or dioxygen under conditions suitable for the oxygenation to take place, provided that if contact is made in the presence of dioxygen, then M in the complex is in its reduced state and L is at least monosubstituted by C0 2 " or CO j H when M is Fe. In one embodiment, a methylenic carbon contained in an organic compound, in particular a hydrocarbon, is converted to a ketone. In another embodiment, an aromatic hydrocarbon is converted to an alcohol.

The invention is also directed to a process for the conversion of an acetylene to an α-dicarbonyl which comprises contacting the acetylene with a complex of the formula described above in the presence of hydrogen peroxide or dioxygen tinder conditions suitable for the conversion to take place, provided that if the contact is made in the presence of dioxygen, then M in the complex is in its reduced state and L is at least monosubstituted by C0 2 * or CO j H when M is Fe.

In still another aspect, the invention is directed to a process for the conversion of an olefin to an aldehyde and/or a ketone which comprises contacting the olefin with a complex of the formula described above in the presence of hydrogen peroxide or dioxygen under conditions suitable for the conversion to take place, provided that if the contact is made in the presence of dioxygen, then M in the complex is in

its reduced state and L is at least monosubstituted by C0 2 * or CO j H when M is Fe.

In another specific embodiment, the invention is directed to a process for the conversion of an aryl- α-diol to a carboxylic acid, a dicarboxy ic acid or dicarboxylic acid anhydride which comprises contacting the aryl-α-diol with a complex of the formula described above in the presence of hydrogen peroxide or dioxygen under conditions suitable for the conversion to take place, provided that if the contact is in the presence of dioxygen, then M in the complex is in its reduced state and L is at least monosubstituted by C0 2 " or C0 2 H when M is Fe.

Another embodiment of the invention is directed to a process for the oxidation of an alcohol or aldehyde which comprises contacting an alcohol or an aldehyde with a complex of the formula described above in the presence of hydrogen peroxide or dioxygen under conditions suitable for the oxidation to take place, provided that if the contact is made in the presence of dioxygen, M is in its reduced state and L is at least monosubstituted by C0 2 * or CO j H when M is Fe.

In still another embodiment, the invention is directed to a process for removing a mercaptan from gas streams or for removing hydrogen sulfide or a mercaptan from liquid streams which comprises contacting a gas stream containing a mercaptan or a liquid stream containing hydrogen sulfide or a mercaptan with a complex of the formula as described above in the presence of dioxygen under conditions suitable for the conversion of the hydrogen sulfide or the mercaptan to elemental sulfur, provided M in the complex is in its reduced state and L is at least monosubstituted by C0 2 " or CO j H when M is Fe.

In another aspect, the invention is directed to novel complexes of formula

wherein:

L and L 1 are the same or different and each is a ligand of formula

wherein R 1 is hydrogen, C0 2 * or CO j H; R 2 is hydrogen;

R 3 is hydrogen, C0 2 ", CO j H or pyridinyl; or R 2 and R 3 joined together and taken with the other atoms in the ring form a quinoline ring which is unsubstituted or substituted in the 8-position by 0"; E is CH, N, NH or CR 4 wherein R 4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R 1 is attached are joined directly and E is NH; H is a transition metal cation; A is an anion of an organic or mineral acid or is a halogen anion;

1 is 1, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2 , 3 or 4; and p is 0, 1 or 2; excluding complexes wherein: L is pyridine, M is Cu or Mn, A is Cl', Br',

Cl ' CIO, " or NO,", 1 is 2, m«n«0 and p is 1;

L is pyridine, M is Fe, A is Cl * , 1 is 4, m«n«=0 and p is 2;

L is 2,2•-bipyridine, M is Cu or Mn, A is Cl", Br ' , I " , Cl " , C10 4 " or N0 3 ", 1 is 1, m=n=0 and p is l;

L is 2,2•-bipyridine , M is Ru, 1 is 3 and m=n=p=0; L is picolinate, M is Fe, 1 is 3 and m=n=p=θ; and

L is 8-quinolinolate, M is Cu, Ni, Co or Fe, 1 is 2 or 3 and m^n-p^O.

The invention will be understood more clearly and fully from the following description of certain preferred embodiments.

DETAILED DESCRIPTION OF THE INVENTION Broadly, the invention relates to a process for the activation of hydrogen peroxide (HOOH) or dioxygen (0 2 ) which comprises contacting hydrogen peroxide or dioxygen with a complex of the formulae shown above under conditions suitable for the activation to take place. Hydrogen peroxide and dioxygen are molecules which, by themselves, do not react with a substrate. Thus, the term "activation" as used herein means imparting to hydrogen peroxide or dioxygen the ability to transform an organic substrate to some new molecule. In accordance with the invention, hydrogen peroxide and dioxygen are activated by contact with a complex according to the invention. Upon contact, hydrogen peroxide and dioxygen, in association with the complex, form species which in turn transform the substrate into a new molecule. Hydrogen peroxide is activated to species lb shown in equation (2) below. Dioxygen is activated to species 7 shown in equation (12) below. It is to be noted that in species 7, the bond between the two oxygen atoms of dioxygen is not broken. In other words, activation of

dioxygen in accordance with the invention involves the ormation of an activated species which incorporates dioxygen in such a way that the bond between the two oxygen atoms of dioxygen is preserved.

The complex is an aromatic, heterocyclic ligand (L, L")-metal(M) complex. Advantageously, L and L* are the same or different and each is a ligand of formula

wherein R 1 is hydrogen, C0 2 * or CO j H;

R 2 is hydrogen;

R 3 is hydrogen, C0 2 ' , CO j H or pyridinyl; or R 2 and R 3 joined together and taken with the other atoms in the ring form a quinoline ring which is unsubstituted or substituted in the 8-position by 0';

E is CH, N, NH or CR 4 wherein R 4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no Q substituent, E and the carbon atom to which R 1 is attached are joined directly and E is NH;

M is a transition metal cation; A is an anion of an organic or mineral acid; 1 is l, 2, 3 or 4; m is 0 or 1; n is 0, 1, 2, 3 or 4; and p is 0, 1 or 2. More advantageously, L and L* are selected from the group consisting of pyridine, 2,2'-bipyridine, pyrazine, imidazole, quinoline, 8-quinolate,

picolinate, 2,6-pyridine dicarboxylate, 2-pyrazine carboxylate, 2,6-pyrazine dicarboxylate, 2-imidazole carboxylate and 2,5-imidazole dicarboxylate.

M is a transition metal cation. Transition metals include elements 21-29, 39-47, 57-79 and all known elements from 89 on of the Periodic Table. Advantageously, M is selected from the group consisting of Fe, Mn, Co, Ni, Cu and Ru.

A is an anion and advantageously is an anion of an organic or mineral acid or is a halogen ion. More advantageously, A is selected from the group consisting of C10 4 , AcO ' , N0 3 " , F " , Cl ' , Br * and I". The following are preferred complexes in accordance with the invention:

E

More advantageously, complexes according to the invention are selected from the group consisting of bis(picolinato)-iron(II) [Fe(PA) 2 ] , (2,6-dicarboxylato- pyridine)-iron(II) [Fe(DPA) ] , bis(2,6-carboxylato- carboxyl-pyridine)iron(II) [Fe(DPAH) 2 ], the μ-oxo dimers thereof, i.e., (PA) 2 FeOFe(PA) 2 , (DPA)FeOFe(DPA) and (DPAH) 2 FeOFe(DPAH) 2 and bis(bipyridine)- cobalt(II) [CO π (bpy) 2 2 *].

Hydrogen peroxide or dioxygen so activated by the complexes described above can be used to transform a variety of organic compounds. In general, an organic compound is contacted with a complex described above in the presence of hydrogen peroxide or dioxygen under conditions suitable for the transformation (e.g., ketonization of methylenic carbons or dioxygenation) to

take place, provided that if the contact is made in the presence of dioxygen, then M in the complex is in its reduced state (e.g., Fe 11 , Cu 1 , etc.) and R 1 and R 3 are the same or different and each is C0 2 " or CO j H when M is Fe.

Thus, a methylenic carbon contained in an organic compound can be converted to a carbonyl by contacting the organic compound with a complex as described above in the presence of hydrogen peroxide or dioxygen under conditions suitable for the conversion to take place, provided that if the contact is made in the presence of dioxygen, then M in the complex is in its reduced state and R 1 and R 3 are the same or different and each is C0 2 " or C0 2 H when M is Fe. In one embodiment, the organic compound containing the methylenic carbon has formula I

R 5 - CH 2 - R 6 (I)

wherein

R 5 and R 6 are the same or different and each is hydrogen, hydroxyl, alkyl or is aryl which is unsubstituted or mono- or polysubstituted by halogen, N0 2 , OH, loweralkyl or loweralkoxy, or R 5 and R 6 taken together form a C j -C^ saturated or unsaturated ring, provided R 5 and R 6 are not both hydrogen, which is converted to a compound of formula II

0

(II)

wherein R 5 and R 6 are defined as above. In a preferred embodiment, R 5 and R 6 are the same or different and each is alkyl or aryl.

As used with reference to formulae I and II above, as well as throughout the specification and appended claims, the term alkyl N refers to a straight or branched chain hydrocarbon radical containing no unsaturation such as, e.g., methyl, ethyl, l-propyl, 2- propyl, 2-methylpropyl, 1-pentyl, 2-pentyl, 3-hexyl, 4- heptyl, 2-octyl, and the like. The term "alkenyl" refers to a straight or branched chain hydrocarbon radical containing one or more double bonds such as, e.g. ,propenyl, pentenyl, hexenyl, and the like. The term "alkoxy" refers to a compound formed by the combination of an alkyl group and an oxy group and includes, e.g., methoxy, ethoxy, propoxy, butoxy, and the like. The term "lower" as applied to any of the aforementioned groups refers to a group having a carbon skeleton containing up to and including 6 carbon atoms. The term "halogen" refers to a member of the family consisting of fluorine, chlorine, bromine and iodine. The term "aryl" refers to an organic radical derived from an aromatic or heteroaromatic hydrocarbon by the removal of one hydrogen atom, such as, e.g., phenyl, naphthyl, tolyl, βalicyl, pyridinyl, etc. The terms "arylloweralkyl" and "arylloweralkoxy" refer to an aryl radical which is mono- or polysubstituted by loweralkyl or loweralkoxy. The term "polysubstituted" as used herein refers to a molecule which is di- or higher substituted, the degree of substitution being determined by the available sites on the molecule.

Thus, methylenic carbons contained in, e.g., cyclohexane, n-hexane, ethylbenzene, diphenylmethane, 2-methyl-butane, toluene, adamantane, cyclododecane, cyclohexene and 1,4-cyclohexadiene can be converted to carbonyls to yield, respectively, cyclohexanoane, 3- hexanone and 2-hexanone, acetophenone, benzophenone, 3-

methyl-2-butanone, benzaldehyde, 2-adamantanone, cyclododecanone, 2-cyclohexene-l-one and 1,4- cyclohexadiene-3-one (which spontaneously converts to phenol) . In another embodiment of the invention, dioxygen or hydrogen peroxide is activated by a complex described above to convert an acetylene to an α-dicarbony compound. The acetylene is contacted with the complex in the presence of hydrogen peroxide or dioxygen under conditions suitable for the conversion to take place, provided that if the contact is made in the presence of dioxygen, then M in the complex is in its reduced state and R 1 and R 3 are the same or different and each is C0 2 * or CO j H when M is Fe. In particular, an acetylene of formula III

R 7 _ Γ==Γ - E B (III)

wherein R 7 and R 8 are the same or different and each is H, halogen, alkyl or is aryl which is unsubstituted or mono- or polysubstituted by halogen, N0 2 , OH, loweralkyl or loweralkoxy, can be converted to a compound of formula IV

0 0 c (IV)

wherein R 7 and R 8 are defined as above. In a preferred embodiment, both R 7 and R 8 are aryl. For example, in accordance with this embodiment of the invention, diphenylacetylene is converted to benzil.

In still another embodiment of the invention, hydrogen peroxide or dioxygen is activated by a complex described above to convert an aryl olefin to an

aldehyde or a ketone. The olefin is contacted with the complex in the presence of hydrogen peroxide or dioxygen under conditions suitable for the conversion to take place, provided that if the contact is made in the presence of dioxygen, then M in the complex is in its reduced state and R 1 and R 3 are the same or different and each is C0 2 ' or CO j H when M is Fe. In particular, an olefin of formula V

10 n ll

R y —c r.—R (V) wherein R 9 -R 12 are the same or not all the same and each is H, alkyl or is aryl which is unsubstituted or mono- or polysubstituted by halogen, N0 2 , OH, loweralkyl or loweralkoxy provided at least one of R 9 -R 12 is aryl or substituted aryl, can be converted to compounds of formulae VI and VII

0 0

,10 (VI) 11 12 (VII)

wherein R 9 -R 12 are as defined above. In a preferred embodiment, R 9 , R 10 , R 11 and R 12 are the same or not all the same and each is H, alkyl or aryl. Thus, for example, cis-stilbene, styrene or methylstyrene can all be converted in accordance with the invention to benzaldehyde (and additionally formaldehyde and acetaldehyde, respectively) .

Another embodiment of the invention involves the activation of hydrogen peroxide or dioxygen by a complex described above to convert an aryl-o-diol to a carboxylic acid, a dicarboxylic acid or a dicarboxylic acid anhydride. The aryl-α-diol is contacted with a complex described above in the presence of dioxygen

under conditions suitable for the conversion to take place, provided M in the complex is in its reduced state and R 1 and R 3 are the same or different and each is C0 2 " or CO g H when M is Fe. Thus, an aryl-α-diol of formula VIII

wherein R 13 -R 16 are the same or not all the same and eac is H, halogen, N0 2 , CH, or is loweralkyl, aryl, arylloweralkyl, loweralkoxy or arylloweralkoxy each of which is unsubstituted or mono- or polysubstituted by halogen, N0 2 , OH, loweralkyl, loweralkoxy or NR 17 R 18 wherein R 17 and R 18 are the same or different and each i H or loweralkyl, can be converted to compounds of formulae IX and X

13 14 15 R 16

HO C - "C - C - OH (IX)

(X)

wherein R 3 -R 16 are defined as above. In addition an aryl-o-diol of formula XI

O H O H

R 1 9 - C z=C - R 2 0 ( X I )

wherein R 19 and R 20 are the same or different and each is aryl which is unsubstituted or mono- or polysubstituted by halogen, N0 2 , OH, loweralkyl, loweralkoxy or NR 17 R 18 wherein R 7 and R 18 are defined as above, can be converted to compounds of formulae XII, XIII and XIV:

19 - C - OH (XII) HO C - S 20 (XIII)

R 19 - C - 0 - C - R 20 (XIV)

wherein R 19 and R 20 are defined as above. For example, in accordance with the invention, catechol and benzoin can be converted to muconic acid (and its anhydride) and benzoic acid (and its anhydride) , respectively. One skilled in the art will recognize that benzoin exhibits enol-keto tautomerism and the enol tautomer is an aryl-o-diol.

Still another embodiment of the invention involves the activation of hydrogen peroxide by a complex described above to oxidize an alcohol or an aldehyde. Thus, an alcohol of formula XV

wherein R 21 and R 23 are the same or different and each is loweralkyl and R 22 is OH, can be oxidized to a compound of formula XVII

wherein R 21 and R 23 are defined as above, or an alcohol of formula XVIII

OH

R 24 - CH - R 24 (XVIII)

wherein R 24 and R 25 are the same or different and each is hydrogen, alkyl or aryl which is unsubstituted or mono- or poly-substituted by halogen, N0 2 , loweralkyl or loweralkoxy, or R 5 and R 6 taken together form a C j -C^ saturated or unsaturated ring provided R 24 and R 25 are not both hydrogen, can be converted to a compound of formula XIX

O || ^ - C - R 25 (XIX)

wherein R 24 and R 25 are as defined above. In addition, an aldehyde of formula XX

R 25 - C(«0) - H (XX)

wherein R 25 is aryl which is unsubstituted or mono- or polysubstituted by halogen, N0 2 , OH, loweralkyl or loweralkoxy, can be oxidized to a compound of formula XXI R 25 - C(=0) - OH (XXI) wherein R j is defined as above. For example, in accordance with this embodiment of the invention, 2,6- dimethylphenol, cyclohexanol, benzyl alcohol and benzaldehyde can be oxidized to 2-6-dimethyl-para- benzoquinone, cyclohexanone, benzaldehyde and benzoic acid, respectively.

In yet another embodiment of the invention, a mercaptan can be removed from gas streams and hydrogen sulfide or a mercaptan can be removed from liquid streams by contacting a gas stream containing a mercaptan or a liquid stream containing hydrogen sulfide or a mercaptan with a complex described above in the presence of dioxygen under conditions suitable for the conversion of hydrogen sulfide or the mercaptan to elemental sulphur, provided that M in the complex is in its reduced state and R and R 3 are the same or different and each is C0 2 * or CO j H when M is Fe. In general, mercaptan as used herein refers to any organic compound containing the radical-SH. In particular, the mercaptan will have the formula RSH wherein R is alkyl, aryl or arylloweralkyl.

The processes according to the invention are generally carried out in a solvent matrix comprising a an aromatic heterocyclic solvent having at least one nitrogen atom in admixture with (1) an organic or mineral acid or (2) a polar, aprotic, non-basic organic solvent wherein the ratio of the aromatic heterocyclic solvent to the acid or organic solvent in the mixture ranges from about 1-6:6-1. Aromatic heterocyclic

solvents include, e.g., pyridine, pyrazine and imidazole and substituted derivatives thereof; organic acids include those which do not contain a methylenic carbon, e.g., acetic acid; mineral acids include, e.g., perchloric acid and hydrochloric acid; and polar, aprotic, non-basic organic solvents include, e.g., acetonitrile (MeCN) , benzonitrile and methylene chloride. In the processes of the invention wherein M in the complex is Fe, the solvent matrix advantageously comprises a mixture of pyridine and acetic acid wherein the ratio of pyridine to acetic acid in the mixture is about 2:1. In the processes of the invention wherein M in the complex is Co, the solvent matrix advantageously comprises a mixture of acetonitrile and pyridine wherein the ratio of acetonitrile to pyridine is about 4:1.

In accordance with the invention, the processes are carried out at a temperature from about - 30°C to 80°C, advantageously from about 25°C to 60°C and more advantageously from about 20°C to 25°C. Where the process involves the activation of hydrogen peroxide, the concentration of the substrate broadly ranges from about 0.5 to 5.0 M, advantageously from about 0.5 to 1.0 M. The concentration of the complex ranges from about 1 to 100 mM. Hydrogen peroxide is used in excess. Generally, the amount of hydrogen peroxide to be used is related to the amount of metal present in the complex and typically the ratio of hydrogen peroxide to metal is about 20:1. Thus, the concentration of hydrogen peroxide can range from about 56 M to about 1 M, advantageously, from about 56 mM to 100 mM for a substrate concentration of IM.

Where the activation of dioxygen is involved, the complex can be added to the point of saturation

since the reaction rate is linear with the concentration of complex (catalyst) . Typically, the concentration of catalyst ranges from about 1 to 100 mM. The source of dioxygen can be either pure dioxygen or air. If the source of dioxygen is pure dioxygen, the pressure used is generally limited by the vessel being used but nevertheless can range from about 1 atmosphere to 100 atmospheres. Typically, a pressure of 1 atmosphere provides 3.4 mM dioxygen. In contrast, l atmosphere air provides 0.68 mM dioxygen.

Accordingly, reactions using pure dioxygen are approximately 5 times as fast as reactions using air.

In the processes of the invention which involve the activation of dioxygen, a reductant is advantageously used. Generally, the reductant is hydrogen sulfide, a mercaptan, a hydrazine or cyclohexadiene (1,3- and 1,4-). Advantageously, the reductant is selected from the group consisting of hydrazine, 1,2-diphenylhydrazine, benzyl mercaptan and hydrogen sulfide. There is no limit on the amount of reductant that can be used and generally the more used, the better. Typically, the concentration of the reductant ranges from about 10 mM to 100 M for a substrate concentration of about IM. Another embodiment of the invention is directed to novel complexes of formula

(L) 1 M(OM) > (L « ) B <A) p wherein:

L and L* are the same or different and each is a ligand of formula

wherein R 1 is hydrogen, C0 2 " or C0 2 H; R 2 is hydrogen;

R 3 is hydrogen, C0 2 " , CO^ or pyridinyl; or R 2 and R 3 joined together and taken with the other atoms in the ring form a quinoline ring which is unsubstituted or substituted in the 8-position by 0"; E is CH, N, NH or CR 4 wherein R 4 is alkyl; Q is CH; q is 0 or 1 provided that when q is 0, there is no substituent, E and the carbon atom to which R is attached are joined directly and E is NH; M is a transition metal cation; A is an anion of an organic or mineral acid; 1 is 1, 2, 3 or 4; m is 0 or l; n is 0, 1, 2, 3 or 4; and p is 0, 1 or 2; excluding complexes wherein: L is pyridine, M is Cu or Mn, A is Cl * , Br", I " , Cl " , C10 A " or N0 3 ", 1 is 2, m«n=0 and p is 1;

L is pyridine, M is Fe, A is Cl", 1 is 4, m«n«0 and p is 2;

L is 2,2'-bipyridine, M is Cu or Mn, A is Cl " Br " , I", Cl", C10 4 * or N0 3 " » 1 is l, m=n«0 and p is 1; L is 2,2'-bipyridine, M is Ru, 1 is 3 and m«n«p«0;

L is picolinate, M is Fe, 1 is 3 and m«n«p=0; and

L is 8-quinolinolate, M is Cu, Ni, Co or Fe, 1 is 2 or 3 and m-n-p-0.

Futher details concerning the various substituents and certain preferred embodiments of the complexes are given above with regard to process

embodiments of the invention and therefore will not be repeated here.

The invention will be more fully described and understood with reference to the following examples which are given by way of illustration and to Schemes I, II and III below. In the examples, the reaction products were separated and identified with a Hewlett- Packard 5880A Series gas chromatograph equipped with a HP-1 capillary column (cross-linked methyl silicone gum phase, 12 m x 0.2 mm i.d.) and by gas chromatography- mass spectrometry (Hewlett-Packard 5790A Series gas chromatograph with mass-selective detector) . Reference samples were used to confirm product identification. The quantities of products were calculated from standard curves for authentic samples. Direct injections of the product solution (1-2 μL) were made.

Cyclic voltammetry was accomplished with a Bioanalytical Systems Model CV-27 voltammograph and a Houston Instruments Model 200 XY recorder. Controiled- potential electrolysis was performed with a three- electrode potentiostat (Princeton Applied Research Model 173 potentiostat/galvanostat, Model 175 universal programmer, and Model 179 digital coulometer) . A Vacuum Atmospheres inert-atmosphere glovebox was used for storage, preparation, and addition of the superoxide species.

The UV/viε spectrophotometric measurements were performed on a Hewlett-Packard Model 8450 diode- array spectrophotometer. Infrared spectra were recorded with an IBM IR/44 (IR/ 0S Spectrometer with IR/30S upgrade unit) FTIR instrument. Solid-state samples were made using a KBr pellet press. Solid magnetic suceptibility measurements were performed with

a Johnson Matthey Model MSB1 Magnetic Susceptibility Balance.

Singlet dioxygen production was detected by measurement of its characteristic 1268-nm chemiluminescence. The chemiluminescence spectrometer that was used for these measurements has been described (9). Singlet oxygen-quenching constants for the iron complexes were derived from ^-phosphorescence measurements as previously described in the literature (10).

The solvents for the syntheses and analyses were the highest purity commercially available and were used without further purification. Burdick and Jackson "distilled in glass" grade acetonitrile (MeCN, 0.004% H 2 0) , dimethylformamide (DMF, 0.011%, H 2 0) , pyridine (py, 0.014% H 2 0) , and glacial acetic acid (HOAc, ACS grade, Fisher Chemical Co.) were used as solvents. The magnetic susceptibility measurements made use of d 7 -DMF that contained 1% tetramethylsilane (TMS, Aldrich Chemical Co.). High purity argon gas was used to deaerate the solutions. All compounds were dried in vacuo over CaS0 4 for 24 hours prior to use.

Bold face Arabic numerals which may or may not be followed by a bold face, lower case letter and which are in parenthesis refer to compounds shown in Schemes I, II and III below.

gxample J

Preparation of Reaσents A. Synthesis of Concentrated Hvdroσen Peroxide

Water was carefully removed from 10 mL of 50% HOOH at O'C via high-vacuum evaporation to give 1.5-3 mL of almost pure hydrogen peroxide (HOOH) (7) . This was quickly dissolved in dry acetonitrile (25 mL) . The resulting solutions were assayed by iodometric titration, and found to be 1.6 M (94% HOOH) and 3.6 M (82% HOOH) .

B. Synttesis of Tetramithylammoni a Pieolinate And Tetramethvlammonium Dioicolinatβ

Tetramethylammonium pieolinate [(Me 4 N)PA] and bis(tetramethylammonium) 2,6-dicarboxylato-pyridine

[ ( e^Nj PA] were prepared by the neutralization of picolinic acid (PAH) and 2,6-pyridinedicarboxylic acid (DPAH 2 ) , respectively, with tetramethylammonium hydroxide in methanol solution (Aldrich) . (Me 4 N)PA was recrystallized from acetonitrile and (Me^NJ g DPA from 95% MeCN/5% MeOH. The hydroscopic products were stored under vacuum, and were used to prepare 50 mM stock solutions in the appropriate solvent mixture.

C. Synth sis 9f rr»(MeCN) (gJ t Q 2 The [Fe(MeCN) (C10 2 complex was prepared by multiple recrystallizations of [Fe(H 0) 6 ] (C10 4 ) 2 (G.F. Smith Chemicals) from MeCN.

D. Preparation of Iron Pieolinate And Iron Dicicolinatβ Solutions

Solutions of Fe(PA) 2 , Fe(PA) 3 , Fe(DPA), and

Fe(DPAH) 2 were prepared in situ by mixing [Fe(MeCN)<] (C10<) 2 or Fe(C10 4 ) s (anhydrous) with various ratios of the ligand anion. Fe(PA) 2 has a single absorption band [DMF; λ —x , 462 nm (e 1200 cm "1 M *1 ) and in

2Py/H0Ac; λ mχ t 402 nm (c 2480 cm' 1 M *1 )], which shifts to a longer wavelength with excess ligand [Fe(PA) 3 * in DMF; ^, 496 nm (e 1670 cm *1 M' 1 )]. Likewise, Fe(DPA) has a single absorption band [DMF; 1>ax , 484 nm (c 620 cm^M' 1 ) and in 2py/H0Ac; ^, 395 cm (€ 1950 cm^M' 1 ) with two shoulders [480 nm (ε 1280 cm" 1 M '1 ) and 500 nm (e 840 cm' 1 M '1 )]. The band shifts with the addition of excess ligand [(Fe(DPA) 2 2' in DMF; λ x , 552 nm (c 540 cm *1 M' 1 )].

E. Syntheses of n Fe(PA) 2 '', [(PAJJβfOH)] 2 (la in Scheme I below), [(PA) 2 FeOF«(PA) 2 ] (lb in Scheme I below). 'FefDPA)" and rfDPAlFafosn.. The nominal complexes "Fe(PA) 2 " and "Fe(DPA)" were prepared by mixing [(Fe(MeCN) 4 ] (C10 4 ) 2 and the stoichiometric amount of the tetramethylammonium salt of the ligand (in acetonitrile under argon) , which yielded a brick-red precipitate. The isolated powder gradually turned light brown upon exposure to air.

This brown powder ["Fe(PA) 2 "], when dissolved in DMF, exhibited a broad absorption band [λ MX , 348 nm (e 1400 cm" 1 M *1 ) and the solid had infrared bands at 695, 708, 761, 950, 1025, and 1049 cm' 1 with a strong, broad band at 1092 cm '1 . The ligand, (Me 4 N)PA, exhibited bands at 689, 774, and 834 cm' 1 with a broad band at 981 cm' 1 and small bands at 1034 and 1077 cm' 1 ) . The precipitate obtained for "Fe(DPA)" was an orange-brown powder that became light brown upon exposure to air. Dissolution of "Fe(PA) 2 " and "Fe(DPA)" in DMF and electrochemical

characterization confirmed that the materials were each about 2/3 in their reduced states [Fe(PA) 2 and Fe(DPA)].

Exposure of MeCN solutions of Fe(PA) 2 to air resulted in the precipitation of a pale green powder, [(PA) 2 Fe(OH)] 2 (la), which in py/HOAc solution exhibited an absorption edge below 400 nm [λ MX , 350 nm (e 2260 cm" 1 M '1 )]. The solid had infrared bands at 694, 708, 760, 857, 1020, and 1047 cm' 1 , and a magnetic moment, μ t , of 7.0 B.M. per dimer molecule (or 4.9 B.M. per Fe) . In DMF, la had a magnetic moment (Evan's method) (11) of 3.6 0.3 B.M. per dimer (2.5 B.M. per Fe) , an irreversible reduction at -0.65 V vs SCE., and a strong UV absorption band [λ mχ l 350 nm (e 3100 cm ' *1 )]. The elemental analysis of the pale green powder, [(PA) 2 Fe(0H)] 2 (la), was performed by Galbraith Laboratories, Inc. (Anal. Calcd for C 24 H 1g N 4 O l0 Fe 2 :C, 45.46; H, 2.86; N, 8.84; 0, 25.23; Fe, 17.61; Found: C, 45.17; H, 3.08; N, 8.80, O, 25.31; Fe, 16.93). The 1:1 combination of Fe(PA) 3 and

(Me 4 N)0H"5H 2 0 in DMF gave a golden-brown solution of a product species, (PA) 2 FeOFe(PA) 2 (lb) , with a magnetic moment of 3.110.2 B.M. per dimer (2.2 B.M. per Fe) , an irreversible reduction potential at -0.85 V vs SCE, and a strong UV absorption band [λ mx , 350 nm (e 3300 cm *1 M "1 ) .

T. Synthesis of r(Pb 3 PO) t FeθOFe(Q?Ph 3 ) t (Clθ) x The synthesis and characterization of this complex has been described in the literature (12) . Tetramethylammonium superoxide [(Me A N)0 2 ] was prepared by combination of K0 2 (Aldrich) and (Me 4 N)0H'5H 2 0 (Fluka) (13, 14). The (py) 4 FeCl 2 complex was prepared

by multiple recrystallizations of FeCl 2 ' 4H 2 0 (Mallinckrodt) in dry pyridine. Combination of (py) FeCl 2 and AgOAc (Strem) in dry pyridine gave a white AgCl precipitate, which was removed prior to the evaporation of the filtrate to give (py) 4 Fe(OAc) 2 . The [Fe(OPPh 3 ) 4 ] (C10 2 complex was synthesized from [Fe(MeCN) 4 ] (C10 4 ) 2 and triphenylphosphine oxide (15).

G. Synthesis of Cowboy). 2 * The nominal complex Co π (bpy) 2 2+ was prepared by mixing two equivalents of bipyridine and one equivalent of cobalt perchlorate in a stock solution of acetonitrile in argon. The resulting precipitate was filtered and dried.

Example II

Hydrogen Peroxide Activation By Various Iron Complexes For The Conversion Of Various Substrates For activation of HOOH by the various iron complexes, solutions that contained 0.5-1.0 M substrate and 1-20 mM iron complex in 3.5 mL of a pyridine/acetic acid mixture were used. Hydrogen peroxide (56 mM or 100 mM) was injected as an anhydrous solution in MeCN or as undiluted 50% HOOH in water. After 4 h with constant stirring at room temperature (2212*C) , samples of the reaction solution were injected into a capillary-column gas chromatograph for analysis. In some cases the reaction was quenched with water, and the product solution was extracted with diethyl ether. Product species were characterized by GC-MS. Reference samples were used to confirm product identifications, and to produce standard curves for quantitative assays of the product species.

A. Conversion of Cvclohexane

Hydrogen peroxide (HOOH) was added to pyridine/acetic acid solutions that contained several iron-picolinate (PA), iron-(2,6-dicarboxylato- pyridine) (DPA) , and iron-(B-quinolinolate) (8-Q) complexes, resulting in the catalyzed transformation of c-C 6 H 12 to cyclohexanone [c-C 6 H 10 (O) ] . The substrate and each of the complexes were combined in 3.5 mL of pyridine/acetic acid solvent (2:1 mol-ratio) , followed by the slow addition over a period of one to two minutes of 13 μl of 17.3 M HOOH (49%) in water to give 56mM - 96mM HOOH. The reactions were stirred at 20° to 24°C for 4 to 15 hours. The product solutions were analyzed by capillary gas chromatography and GC-MS, either by direct injection of the product solution or by quenching with water and extracting with diethyl ether. Table IA summarizes the conversion efficiencies (c-C 6 H 12 oxidized per two HOOH) and product yields for the catalyzed oxygenation of cyclohexane by HOOH and compares the various complexes in terms of catalytic efficiency, turnover and product selectivity in a pyridine/acetic acid solution matrix. An efficiency of 100% represents one substrate oxygenation per two HOOH molecules added; the remainder of the HOOH was unreacted or consumed via slow 0 2 evolution and Fenton Chemistry to produce [py(OH)] n . Catalyst turnover was calculated as moles of substrate oxygenated per mole of catalyst (complex) . No reactions occurred when [Fe(MeCN) 4 ] (C10 2 , (py) 4 Fe(OAc) 2 , and Fe(acac) 2 were used as catalysts. In addition, (py) 4 FeCl 2 , (bpy) 3 Fe(C10 4 ) 2 and FeCl 3 gave reaction efficiencies of less than 15%, with cyclohexanol as the major product. The effects of the solvent matrix on the yields of the

c-C 6 H 12 /HOOH/Fe(PA) 2 reaction system are summarized in Table IB.

Table I. Products and Conversion Effeciencies for the Iron-Catalyzed Ketonization of Cyclohexanβ by HOOH in Various Solvents.

Table I (continued)

B. Cyclohexene (IM); 3.5 mM Fe(PA) 2 ; 56 mM HOOH

Solvent reactn produc s efficiency, %(±3) cyclohexanone, %(±4) cyclohexanol, %(±4)

pyridine (py) 6 93 7 py/HOAc (4.5:1 mol-ratio) 65 93 7 py/HOAc (1.9:1 mol-ratio) 72 93 7 py/HOAc (1.0:1 mol-ratio) 66 93 7 py/HOAc (0.6:1 mol-ratio) 58 93 7

MeCN 9 40 60

MeCN/HOAc (3.6:1 mol-ratio) 11 73 27

The presence of substantial amounts of water (100 mM) reduced the reaction efficiency (especially for low

Fe(PA) 2 concentrations) , but did not reduce the selectivity for ketone formation. The use of acetonitrile in place of the pyridine/HOAc solvent system greatly reduced the reaction efficiency and eliminated any selectivity. With pure pyridine as the solvent, there was no reactivity. In the absence of substrate the Fe(PA) 2 /HOOH/(py 2 /HOAc) system slowly decomposed to give 0 2 , H 2 0, and [py(OH) ] n (half-life >6 h).

B. Conversion of Hydrocarbons with

Methvlenie Carbons. Acetylenes and Olefins

Table II summarizes the conversion efficiencies and product yields for the oxygenation by the

HOOH/Fe(PA) 2 combination of several organic substrates (hydrocarbons with methylenic carbons, acetylenes, and arylolefins) . The substrate and Fe(PA) 2 were combined in 3.5 mL of pyridine/acetic acid solvent (2:1 mol- ratio) , followed by the slow addition over a one to two minute period of 13 μL of 17.3 M hydrogen peroxide (49%) in water or 60 μL of 1.6 - 3.8 M hydrogen peroxide (92%) in MeCN to give 56 mM hydrogen peroxide. The mixture was stirred for four hours at 20° to 24°C. The product solution was analyzed by capillary gas chromatography and GC-MS, either by direct injection of the product or by quenching with water and extracting with diethyl ether. Catalyst turnovers (moles of substrate oxygenated per mole of catalyst) are also tabulated. 100% reaction efficiency represents one substrate oxygenation per two HOOH molecules added; the remainder of the HOOH was either unreacted or consumed via slow 0 2 evaluation and Fenton Chemistry to produce l/n[py(0H) n ]-

Table II. Products and Conversion Efficiences for the Fe(PA) 2 -catalyzed (3.5 mM)

Ketonization of Methylenic Carbon and the Dioxygenation of Acetylenes and Arylolθfins by HOOH (56 mM) in Pyridine/HOAc (2:1 mol-ratio).

reactn catalyst substrate (1 M) efficiency, %(±3) turnovers products

cyclohexanone (97%) , cyclohexanol (3%)

3-hexanone (53%), 2-hexanone (46%), 1-hexanol (<2%)

5 PhC(0)CH 3 (>96%) 3 PhC(0)Ph(>96%)

<1 PhCH(O) (>96%) 3 3-methyl-2-butanone(>95%) , 2-methyl- l-butanol(<2%) ada antane (0.1 M) 32 2-adamantanone (43%) , 1-adamantanol (29%), 1-pyridinyl-adamantane (two isomers, 18% and 10%) cyclododecane (0.5 M) 70 cyclododecanone (90%) , cyclododecanol (10%) cyclohexene 59 5 2-cyclohexene-l-one(>95%)

1,3-cyclohexadiene 33 5 PhH(>95%)

1,4-cyclohexadiene 30[70] 3(11] Ph0H(17%)[PhH](83%) cyclohexanone 0

Table II (Cont.) reactn catalyst substrate (1 M) efficiency, %(±3) turnovers products

4 cyclohexanone (>95%) 3 PhC(0)C(0)Ph(>97%) r θ |

4 PhCH(O) (75%) ,PhCHCHPh(25%) 4 PhCH(O) (63%) ,PhCHCHMe(16%) , two others (21%)

The relative reaction efficiencies for cyclohexane, n-hexane, cyclohexene, and 1,4- cyclohexadiene were roughly proportional to the number of (>CH 2 ) groups per molecule, 6, 4, 4, and 2, respectively, and the product for each is the ketone from the transformation of a single methylenic carbon. Addition of a second 56 mM increment of HOOH to a reacted cyclohexane system resulted in an additional ketonization (68% reaction efficiency). The conversion of 1,4- cyclohexadiene to phenol (via ketonization of a methylenic carbon) without any epoxide formation confirmed the selectivity of the reactive intermediate. Likewise, the ketonization of cyclohexene further supported the selective reactivity towards methylenic carbon. However, 1,3-cyclohexadiene was dehydrogenated to give benzene.

The lower reactivity of cyclohexanol relative to cyclohexane ("1/3) indicates that c-C^H^OH is not an intermediate for the ketonization of c-C 6 H 12 . This is further supported by the results for a combined substrate of 1 M c-C 6 H 12 and 1 M c-C^H^OH, which had a ketonization efficiency of 65% (in contrast to 72% for 1 M c-C 6 H 12 alone, Table II). Likewise, the presence of 1 M i-PrOH with 1 M c-C 6 H 12 caused a reduction in the conversion efficiency for c-C 6 H 12 to 56%, but no acetone. Analysis of the product solution during the course of the ketonization of 1 M c-C 6 H 12 gave a constant 19:1 c- C 6 H 10 (O)/c-C 6 H 11 OH ratio (0.1 to 1.0 fractional reaction). The reactive intermediate dioxygenateε acetylenes to give the α-dione as the sole product. With the Fe(PA) 2 /HOOH/(py 2 /HOAc) system, arylolefins were dioxygenated and epoxidized. Table IIIA provides a comparison of HOOH, m-ClPhC(0)OOH, and t-BuOOH as oxygenation agents for ciε-PhCH«CHPh and PhC»CPh. Hydrogen peroxide is uniquely effective with Fe(PA) 2 for the dioxygenation of these substrates.

Table III. Comparison of Hydroperoxides (ROOH) and Iron Catalysts for the Oxygenation of cis-βtilbene (cis-PhCH=CHPh), PhC≡CPh, and c-C 6 H 12 in Pyridinβ/Acetic Acid (2x1 mol-ratio) .

A. 56 M Hydroperoxide (RCOH); 3.5 M Fe(PA) 2

1. cis-PhCH=CHPh (1 M)

Table III. (Cont.)

B. cis-PhCH=CHPh(0.7 M); HOOH (15 M) products

O reactn / \ catalyst (15 mM) efficiency,%(±3) PhCH(O) ,% PhCH-CHPh,%

Fe(PA) 2 13 59 41 (PA) 2 FeOFe(PA) 2 18 52 48

C. C-C 6 H 12 (1 M); HOOH(19 mM) reactn produc s catalyst (19 mM) efficiency,%(±3) c-C,H 1n (Q),% (c-C A H„),,% py-c A H„,%

(PA) 2 Fe 53 20 14 66

(PA) 2 Fe(9 M) 85 34 3 63 (9 mM HOOH)

(PA) 2 Fe(catalyst added 67 36 10 54 to [S]/HOOH)

(PA) 2 FeOFe(PA) 2 39 30 13 57

example III

Activation of Dioxygen by Fe π (DPAH) 2 for the Ketonization Of Methylenic Carbons and the Dioxygenation of Acetylenes. Arylolefins and Catechols

For activation of dioxygen and conversion of various substrates, the substrate and Fe π (DPAH) 2 were combined in 3.5 mL pyridine/acetic acid solvent (2:1 mol- ratio) , followed by the addition of dioxygen (0 2 ) at one atmosphere (3.4 mM) , in a reaction cell having 6 L of head-space. The reaction was stirred at a temperature ranging from 20° to 24 for a period of four hours (12 hours for 32 mM Fe π (DPAH) 2 ) . Product solutions were analyzed by capillary gas chromatography and GC-MS, either by direct injection of the product solution or by quenching with water and extracting with diethyl ether. The reactions were monitored by UV-visible spectrophotometry and the apparent reaction orders and rate constant were determined from the initial rates of disappearance and appearance of Fe π (DPAH) 2 MX , 394 nm) . The products and reaction efficiencies for various concentrations of Fe M (DPAH) 2 and substrates are summarized in Table IV. In the table, a 100% reaction efficiency represents one substrate ketonization or dioxygenation per (DPAH) 2 FeOOFe(DPAH) 2 reactive intermediate.

Table IV. Ketonization of Methylenic Carbons, and Dioxygenation of Arylolefins,

Acetylenes and Catechols Via the Fe"(DPAH) 2 -Induced Activation of Dioxygen in 1.8:1 py/HOAc.

A. Cyclohexane (IM); Q ? (l tm, 3.4 mM)

[product],mM reactn [Fe"(DPAH) ? ], mM [reductant], mM c-C A H <n (Q) c-C^H^OH efficiency, %(±3)

8

32

83

32

32

3 3

32 16 (H 2 NNH 2 ) 6.7 32 32 (H 2 NNH 2 ) 9.1

Table IV. (Cont.)

[product] ,mM reactn

[Fe"(DPAH),], mM [reductant], mM c-C A H ιn (0) c-C A H OH efficiency, %(±3)

32 32 (PhCH 2 SH) 8.6 <0.2 54 32 128 (PhCH 2 SH) 18.5 <0.2 116 (4 turnovers; each 23% efficient)

32 10 (H 2 S) 5.5 <0.1 34 (1 turnover; 7% efficient)

32 14

Table IV (Cont.)

B. FΘ"(DPAH) 2 (32 mM) ; o 2 (1 atm, 3.4 mM)

reactn substrate products (mM) efficiency,%(±3)

c-C 6 H 12 (IM) c-C 6 H 10 (O)(4.4) 28

PhCH 2 CH 3 (IM) PhC(0)CH } (3.5) 22 [+128 mMPhNHNHPh] M [18.9]

2-Me-butane (IM) Me 2 CHC(0)Me (1.0) [+128 mM] PhNHNHPh] [9.1] cyclohexene (IM) 2-cyclohexene-l-one (1.2) 7

PhC*CPh (0.6 M) PhCH(0)C(0)Ph (2.2) 14 c-PhCH=CHPh (1 M) PhCH(O) (3.1) 10 l,2-Ph(OH) 2 (1 M) HOC(O)CH=CH-CH=CHC(O)OH 13 (and its anhydride) (2.0)

PhCH(OH)C(0)Ph PhC(0)OH(5.2) 16 (0.3 M)

PhNHNHPh (100 mM) PhN=NPh (100) 667

PhCH 2 SH (128 mM) PhCH 2 SSCH 2 Ph (64) 800

H 2 S (128 mM) S β (16.0) 800

In absence of substrate, the active catalyst was rapidly autoxidized to (DPAH) 2 Fe0Fe(DPAH) 2 [4Fe π (DPAH) 2 per 0 2 ; the apparent second-order rate constant, k ox , had a value of 1.310.5 M ' V (k obs /4) ] . The oxidized catalyst [(DPAH) 2 FeOFe(DPAH) 2 ] was rapidly reduced to Fe π (DPAH) 2 by PhNHNHPh, H g NNH^ PhCH 2 SH, and H 2 S(k Ped ; 6.510.5 M' 1 s' 1 , 0.610.3 M"V\ 0.510.3 M ' V 1 and 2.810.5 respectively) to give PhN-NPh, N 2 , PhCH 2 SSCH 2 P , and elemental sulfur (S β ) , respectively. The PhNHNHPh reductant is an effective reaction mimic for the reduced flavin cofactors in xanthine oxidase and cytochrome P-450 reductase. (16)

Addition of PhNHNHPh, H 2 NNH 2 , PhCH 2 SH, or H 2 S to the reaction system [0 2 /Fe(DPAH) 2 /substrate in py 2 /HOAc] reduced the oxidized catalyst [ (DPAH) 2 FeOFe(DPAH) 2 ] and thereby recycled it for activation of 0 2 to the reactive intermediate (Table IVA and equation 2 below). Thus, without added reductant 32 mM (DPAH) z Fe π activated 0 2 to oxygenate c-C 6 H 12 to give 4.4 mM c-C 6 H 10 (O), but with 32 mM PhNHNHPh present, 9.9 mM c-C 6 -H 10 (O) was produced (and 32 mM PhN-NPh in two catalytic turnovers) . Similar results were obtained with other reductants. When 3 mM Fe π (DPAH) 2 was used in combination with 100 mM PhNHNHPh, the rate for the ketonization of c-C 6 H 12 was reduced by an order of magnitude, but each cycle remained about 21% efficient and there were about 67 catalytic turnovers within 12 h (Table IVA) .

The dioxygenation of unsaturated α-diols (catechol and benzoin. Table IVB) by the 0 2 /Fe π (DPAH) 2 system parallels that of the catechol dioxygenase enzymes, which are non-heme iron proteins (17) . Hence, the reactive intermediate of the Fe π (DPAH) 2 /0 2 reaction (eg. 1) may be a useful model and mimic for the activated complex of dioxygenase enzymes (18) .

This system also affords the means to the selective autoxidation (oxygenation) of hydrocarbon substrates (e.g., c-C 6 H 12 ) via the coprocessing of H 2 S (or RSH)-contaminated hydrocarbon streams. Thus, the combination of c-C 6 H 12 and H 2 S with Fe n (DPAH) 2 and 0 2 in a py 2 /H0Ac solvent matrix yielded c-C 6 H 10 (O) and S β , which are marketable products. The data of Table IV indicate that the approximate reaction εtoichiometry is 28 H 2 S molecules (or 8 PhCH 2 SH or 4 PhNHNHPh molecules) oxidized per c-C 6 H 12 ketonization

Fe n (DPAH), C-C 6 B 12 + 28H 2 S ♦ 150 2 ~> (1)

c-C 6 E 10 (0) + 7/2S e + 29H 2 0

In a flow-reactor for coprocessing hydrocarbon/H 2 S streams, the actual product yields will depend upon the hydrocarbon substrate and its concentration relative to that of H j S (or mercaptan) . The rate of the process is limited by the partial pressure of 0 2 , the concentration of substrate, the concentration of catalyst [Fe 11 (DPAH) 2 ] , and temperature.

Example IV

Activation of HOOH and t-BuOOH by Co"fbPVϊ./ » for the Oxvσenation of Hydrocarbons, the Oxidation of Alcohols and Aldehydes and the Dioxygenation of Arvlole ins and ctvYlenes For activation of HOOH and t-BuOOH and conversion of various substrates, the substrates (IM) and Co 1I (bpy) 2 2 * (20 mM) were combined in 7 mL of acetonitrile/pyridine (4:1 molar ratio) or 7 mL of acetonitrile, followed by the slow addition over a period of one to two minutes of either 100 μL of 17.6 M HOOH (50% in H 2 0) to give 200 mM HOOH, or 600 μL of 3.0

M t-BuOOH (in 2,2,4-trimethyl-pentane) to give 200 mM t-BuOOH. After six hours stirring at a temperature of 22 + or - 2°C, the reaction mixtures were analyzed by capillary gas chromatography and GC-MS, either by direct injection of the product solution, or by quenching with water and extracting with diethyl ether. The product concentrations obtained for a given concentration of substrate and oxident (either HOOH or t-BuOOH) are summarized in Table V.

Table V. Activation of HOOH and t-BuOOH by Co"(bpy) 2 2* for the Oxygenation of Hydrocarbons, the oxidation of Alcohols and Aldehydes, and the Dioxygenation of Arylolefins and Acetylenes in 4:1 MeCN/py.

substrate (1 M) oxidant products (mM) (0.2M)

C-C 6 H 10 (O) (61) ,c-C 6 H„OH(l) c-C 6 H 10 (O) (14) ,c-C 6 H OH(9)

C-C 6 H 1t OOBu-t(1.5)

C-C 6 H 10 (O) (15) ,C-C 6 H„OOBu-t(2) ,C-C 6 H OH(l)

Me 2 CHC(O)Me(12) ,Me 2 C(OH)CH j Me(5)

Me 2 C(OH CH 2 Me(9) ,Me 2 CHC(0)Me(l)

PhC (O) Me (30) , PhCH 2 CH 2 OH ( 11)

PhCH (O) (20) , PhCH 2 OH(17)

PhCH 2 OOBu-t (28) , PhCH(0) (12) c-C 6 H β -2-ene-l-one(50) , epoxide (β) ,c-C 6 H β -2-ene-l-ol (3)

R-OH(31) ,R-one (30) , epoxide (12) , R-R(1) R-OOBu-t(41) ,R-one(6) ,R-OH(3) ,R-R(1)

TABLE V (Continued)

products (mM)

PhOH(34)

C-C 6 H 10 (O)(28)

PhCH(O) (40)

PhC(O)OH(108)

PhCH(O) (87) ,epoxide(4)

PhC(0)C(0)Ph(24)

2 , 6- (Me) 2 -p-benzoquinone ( 5) , ROOR( 3 ) ROOR(9) 4

Example V

Characterization of Catalysts

The results of Table IA indicate that in the presence of excess HOOH, Fe(PA) 2 and (PA) 2 FeOFe(PA) 2 (1) [and Fe(DPA) and (DPA)FeOFe(DPA) (5) ] were equally effective. However, when the concentrations of catalyst and HOOH were the same, the efficiency of Fe(PA) 2 for the oxygenation of ciε- PhCH=CHPh was significantly less than with (PA) 2 FeOFe(PA) 2 (Table IIIB) . Addition of reduced amounts of HOOH (19 mM) to 19 mM Fe(PA) 2 or 19 mM (PA) 2 FeOFe(PA) 2 and 1 M c-C 6 H 12 in pyridine/HOAc resulted in major amounts of products [c-C^H^-py and (c-C 8 H^)^ from the production of c-C^,, radicals via Fenton chemistry (Table IIIC) . When Fe(PA) 2 was added to c- C 6 H 12 /HOOH, the reaction efficiency was enhanced as was the yield of c-C 6 H 10 (O). The apparent second-order rate constant for the 1:1 combination of Fe(PA) 2 /HOOH in py/HOAc was (2ll)xlθ 3 M" 1 s" 1 , but decreased to (21l)xlθ 2 M " V 1 when the Fe(PA) 2 /HOOH ratio was 1:200.

Spectrophotometric and cyclic voltammetric analysis indicated that in the absence of substrate, the combination of excess HOOH with two Fe(PA) 2 molecules (λ MX , 02nm) in the pyridine/HOAc solvent yielded (PA) 2 FeOFe(PA) 2 (1) (irreversible reduction at - 0.1 V vs SCE and UV-visible absorption at <400nm) and (PA) 2 Fe(OAc) (reversible cyclic voltammogram at +0.2 V vs SCE) in 2 * 1 pyridine/HOAc. As Table IA indicates, the use of the (PA) 2 FeOFe(PA) 2 (l) gave results that were equivalent to those of Fe(PA) 2 , and prompts the conclusion that the latter is transformed in situ to 1.

In the contrast to the py/HOAc solvent, addition of HOOH to a solution of species 1 in Me 2 S0 rapidly evolved dioxygen (l is insoluble in MeCN). The [2,6-

dicarboxylato-pyridine]iron(II) complex, Fe(DPA), appeared to be a slightly superior catalyst to Fe(PA) 2 , and paralleled the latter's transformation by HOOH to give the most active and selective catalyst, (DPA)FeOFe(DPA) (5) .

In dimethyIfor amide, the combination of two Fe(PA) 2 molecules with one HOOH resulted in the stoichiometric formation of [(PA) 2 Fe(OH)] 2 (la) ; the apparent second-order rate constant was 2.5 x lO^ ' V. The same process occurred in pyridine/acetic acid, at approximately the same rate (k, "l x IO'M ' V) . Likewise, Fe(DPA) was transformed by HOOH to [ (DPA)Fe(OH) ] 2 ; the rate of reaction is about an order of magnitude faster than for Fe(PA) 2 as determined by spectrophotometry and cyclic voltammetry.

When excess HOOH was added to [ (PA) 2 Fe(OH) ] 2 (la) or [(DPA) 2 Fe(OH)] 2 in DMF, it decomposed rapidly to dioxygen and water. In contrast, the same experiment in pyridine/acetic acid did not result in the rapid decomposition of HOOH, again.

A. Production of Binσlet Dioxvσen t o z ) Table VI summarizes the yields of singlet dioxygen from the addition of [(PA) 2 Fe(OH)] 2 (la) (in equilibrium with (PA) 2 FeOFe(PA) 2 (lb) shown in equation (2) below) to HOOH in dimethyIformamide (DMF) . The reaction of hydrogen peroxide with hypochlorus acid in deuterium oxide solvent was used as a 1 0 2 standard θ z lifetimes: 62 μs for deuterium oxide and 17 μs for DMF) . *o z spectral analysis of near-infrared emission; filter, nm (Signal): 1170 (0.01), 1268 (1.00), 1375 (0.59) and 1470 (0.11). The concentration of 1 0 2 generated was corrected for quenching by [(PA) 2 Fe(0H)] 2 (k , 6.0 x 10 9 M "1 ε *1 ) , where the total quenching at any reaction time

is given by k q# , [[(PA) 2 Fe(OH) ] 2 ] + k qb [ (PA) 2 FeOFe(PA) 2 ] . The rate constantε were evaluated in DMF via photochemical generation of 1 0 2 with rose bengal [bis(triethylammonium salt) ] . Because the apparent quenching constant for [ (PA) 2 Fe(OH) ] 2 decreased for concentrations above 250 μM, this correction method may overestimate the yield of 1 0 2 at the high concentrations indicated by as much as 20%.

Both [(PA) 2 Fe(OH)] 2 and its μ-oxo-form, (PA) 2 FeOFe(PA) 2 (lb) , quenched 1 0 2 with apparent second- order rate constants of 6.0 x 10 7 M * V 1 and 2.0 x 10 9 M *1 ε " , reεpectively. Because essentially stoichiometric yields of singlet dioxygen resulted (one 1 0 2 per la at high HOOH concentrations) , the transition-state complex most likely involves a dioxygen adduct from the combination of two HOOH molecules with la. In contrast, control experiments with Fe(MeCN) 4 (C10 4 ) 2 resulted in the stoichiometric decomposition of HOOH to 3 0 2 and H 2 0, but there was no detectable production of 1 0 2 .

Table VI.

'o^μM 'o^μM

[(PA) 2 Fe(OH)] 2 (la) ,μM HOOH,mM (uncorrected) (corrected)

20 50 100 250 500 1000 2000 2000 2000

•Mean value 1 standard error for 3 measurements. Other values are for single measurements.

B. Dioxygenation by f tPh j POΪ FeOOFe(OPPh j ϊ t ι ιci L ) f4 )

In pyridine/HOAc (mol-ratio, 2:1), a binuclear iron μ-dioxygen complex (4) reacted with excess PhCeCPh to give PhC(0)C(0)Ph exclusively (3% efficient in 15 min.; 0.6 M PhC*CPh and 56 mM 4) ; and with excesε cyclohexane to give cyclohexanone exclusively (3% efficient in 15 min.; IM c-C 6 H 12 and 56 mM 4). In MeCN, neither substrate reacted with 4; however, the addition of sufficient HC10 4 to make the solution 3.7 M caused

PhCsCPh to be transformed almost completely (one

PhC β CPh per 4) within 10 min. [yield 78% of

PhC(0)C(0)Ph and 14% PhC(0)OH].

Summary and Discussion of the Examples The results of Table I establish that the pyridine/HOAc (mol-ratio, 2:1) solvent system is optimal for the efficient and selective ketonization of methylenic carbons by the Fe(PA) 2 /HOOH system. On the basis of the relative reaction efficiencies for Fe(PA) 2 and (PA) 2 FeOFe(PA) 2 (Tables IA and III), the initial step when Fe(PA) 2 is used as the catalyst is its transformation to (PA) 2 FeOFe(PA) 2 (1). The spectrophotometric, electrochemical, and magnetic results for the combination of Fe(PA) 2 and HOOH in DMF confirm a 2:1 reaction stoichiometry to give a binuclear product (k 1# 2 x lO^^s" 1 )

2Fe(PA) 2 + HOOH (2)

OH

(PA) 2 Fe AFe(Pλ) 2 (Pλ) 2 FeOFe(PA) 2 + B 2 0 OH la l i

Electrochemical measurements established that (a) autoxidation of Fe(PA) 2 in MeCN yields a product that is a mixture of la and lb, and (b) the product from the 1:1 combination of Fe(PA) 3 and 'OH in DMF is mainly lb

2Fe(PA), + 2 * OH → (PA),FeOFe(PA) 2 + 2PA " + H,0 (3) lb

The addition of species la to excesε HOOH in DMF results in near stoichiometric production of 1 o 2 (Table IV) and yields species lb during catalytic turnover:

lb * I00E (Pλ) 2 FeOFe(Pλ) 2 E.O (4)

(BOOB) 2

l o, It

With low concentrations of HOOH as well as for reaction conditions with l:lFe(PA) 2 /HOOH, the Fenton process becomes dominant (Table IIIC)(14).

Fe(PA) 2 + HOOH → (PA) 2 Fe(OH) + OH (5a) OH + RH- R' (or h^z) + H 2 0 (5b)

OH + py → py [or l/n(pyOH) n ] + H 2 0 (5c) R- + py → R-py (5d)

For the conditions of the experiments that are summarized in Tables I and II (excesε HOOH added to catalyst/substrate) , the reaction sequence of eq. 2 and eq. 4 prevails to a major degree [with no evidence of Fenton chemistry (eq. 5) in the product profiles]. The results of Table II indicate that the relative

reactivity of species 3 with hydrocarbon substrates in the order CH 2 >PhCβCPh»ArCH«CHR»Ar-CH 3 » CH, which is completely at odds with radical processeε (19).

Referring to Scheme I below, the data of Tables I-III, together with what is known in the literature about the [Fe(MeCN) 4 ] (C10 2 /2HOOH system (7,20), prompt the formulation of reaction steps and pathways for the (PA) 2 FeOFe(PA) 2 /HOOH/(py/HOAc)/substrate system as shown in Scheme la. On the basis of the product profiles and reaction efficiencies (Tables I-III) when (PA) 2 FeOFe(PA) 2 (or its precurεor, Fe(PA) 2 , eg. 2) iε used as the catalyst, the initial step in the catalytic reaction cycle appears to be the formation of an HOOH adduct [(PA) 2 FeOFe(PA) 2 (HOOH) ] (2) . In the presence of >CH 2 or RCβCR groups, species 2 rapidly forms (with another HOOH) the activated complex (species 3, Scheme la). The pre-catalyst (species 2) reacts with selective substrates in a manner that is analogouε to that of other iron-HOOH adductε. Previous studies have demonstrated that similar iron-oxene species are formed from the 1:1 combination of HOOH and [Fe(MeCN) (C10<) 2 , (5,11), [(Ph 3 PO)<Fe](C10 2 (9), and FeCl 3 (21). Thus, for conditions that favor formation of species 2 (i.e., 1:1 (PA) 2 FeOFe(PA) 2 /HOOH, Table IIIB) epoxidation of c- PhCH«CHPh is enhanced, but for conditions that favor species 3 (i.e., 20:1 (PA) 2 FeOFe(PA) 2 /HOOH) dioxygenation is the dominant path (Table II) .

Scheme la.

(a) Reaction Paths

s lov

(PA) 2 FeOFe(PA ) 2 ♦ HOOH (Pλ) 2 Fe e(PA) 2 ππnn 1 + 0 2 ♦ 2H 2 0

Q00H 1 ^fl

Scheme lb.

(b) Proposed Mechanisms

* (PA) 2 feOFe(PA) 2

2Fe»(DPi)(DPAi)- ♦ 0 2 Pf B0AC » -(DPAI)(DPA)Ff00re(DPA)(DPAB)- 1 (7

C"C t l, » > c-C 6 B (0) » fl 2 0 * 2(6 )

2(6)

♦ 2(DPA)Ftθre(DPA) ♦ 4JPAM"

Species 3 transforms methylenic carbons ( CH 2 ) to carbonyls (C*0) and dioxygenates acetylenes and

1

2

2 , , - (Table II) probably is the result of selective

to result from a similar reactive intermediate [but Fe π (DPAH) 2 is one and one-half times as efficient as Fe n (DPA)]. With cyclohexane about one-fourth of the o 2 that is incorporated into the reactive intermediate reacts to give cyclohexanone as the only detectable product; the remainder oxidizes the excess Fe n (DPAH) 2 to give (DPAH) 2 FeOFe(DPAH) 2 , which is catalytically inert.

If the combination of Fe π (DPA) 2 and 0 2 results in the initial formation of the reactive intermediate [ (DPAH) 2 FeOOFe(DPAH) 2 ] via a rate-limiting step

2Fe ,1 α 1 i (, DPλH) 2 ♦ 0 2 (DPAH) 2 Fe00Fe(DPAH) 2 (7) 7

then, the results of Table IV indicate that K is less than unity. Thus, the yield of cyclohexanone increases linearly with Fe π (DPAH) 2 concentration. The apparent rate for the ketonization reaction is proportional to substrate concentration, Fe n (DPAH) 2 concentration, and 0 2 partial pressure, and increases with temperature (about ive times aster at 25 C than at 0 C) . Because the fraction of (7) that reacts with c-C 6 H 2 remains constant (-28%), the oxidation of excess Fe π (DPAH) 2 by (7) must be a parallel process. Given that the ratio of concentrations [c-C 6 H 12 /Fe π (DPAH) 2 ] is about 30:1 and the ratio of reactivities is 1:2.6, then the apparent relative rate constant for reaction of c-C 6 H 12 and Fe"(DPAH) 2 with (7) is about 0.02 k „ (assuming a stoichiometric factor of 2 for the latter) .

The results of Table IV and the close parallels of the product profiles to those for the

(PA) 2 FeOFe(PA) 2 /HOOH/(by/HOAc) system prompt the conclusion that the reactive intermediate for the Fe π (DPAH) 2 /0 2 combination is (DPAH) 2 FeOOFe(DPAH) 2 (7, eq. 7) , and are the basis for the reaction pathways outlined in Scheme II.

Scheme II . Activation of 0 2 by Fe,, (DPAH) 2 in py 2 /HOAc

Table V summarizes the product distributions or a series of substrates that result from the catalytic activation of HOOH or t-BuOOH by CO π (bpy) 2 2* . The product profiles indicate the oxidase (or monooxygenase) chemistry is favored in pure MeCN solvent (c-C 6 H 12 → c-C^^OH) , but the ketonization of methylenic carbon and dioxygenase chemistry are favored in MeCN/py(4:l molar ratio) [c-C 6 H 12 → c-C 6 H 10 (O); c- PhCH«CHPh → 2PhCH(0)]. The selective ketonization of cyclohexene in MeCN/py contrasts with its enhanced monooxygenation in pure MeCN (one/ol ratio; 16:1 vs. 1:1), and is compelling evidence for two reactive intermediates. The presence of 0 2 inhibits the reactivity of c-C 6 H 12 with HOOH by 10-20%. In pure MeCN Co π (bpy) 2+ catalyzes HOOH for the stoichiometric transformation of 1,4-cyclohexadiene to benzene. When t-BuOOH is the oxygen source the reactivity with substrates is about ten times greater in pure MeCN than in MeCN/py (Table V). With PhCH 3 , the dominant product is PhCH 2 OOBu-t, which requires two t- BuoOH molecules per substrate. When c-C 6 H 12 is the substrate, c-C 6 H 10 (O) and c-^H^OOBu-t are the major products (both require two t-BuOOH molecules per substrate) and the ketone probably results from the decomposition of c-C^H^OOBu-t. In contrast, with

(Me) 2 CHCH 2 Me the major product is (MeJ j CfOHJCH j e (one t- BuOOH per substrate) . The use of t-BuOOH precludes (or strongly suppresses) formation of the reactive intermediate for the direct ketonization of methylenic carbons.

The results of Table V and the close parallels of the product profiles to those for the Fe 11 (PA) 2 /HOOH/(py/HOAc) system prompt the conclusion that the combination of Co"(bpy) 2 *(l) and HOOH results

in the initial formation of an oxene intermediate [(bpy) 2* co ,n o-,2], which (in MeCN/py) rapidly reacts with a second HOOH to give a dioxygenase reactive intermediate [ (bpy) 2* CO OOCo (bpy)*\33 (Scheme III) .

Scheme III. Activation of HOOH and t-BuOOH by Co n (bpy) 2 2 a . HOOH (MeCN/py ) ; [ MeCN ]

1 M ■ »

— — I s * " — «- ■ 3 — -

• o i l •

O β β ■ + _

/ \ ^ S ^

* 5 - i *» i I

In pure MeCN, species l appears to activate HOOH and t-BuOOH via formation of 1:1 adducts [(bpy) 2 *CO n (HOOH),4 and (bpy) 2 *Co π (t-BuOOH) ,5] , which, when formed in the presence of substrates, act as monooxygenases (c-C 6 H 12 → c-^H^OH) .

As such, they are closely similar to the reactive intermediate from the combination of [Fe π (MeCN) A ] (C10 4 ) 2 and HOOH in MeCN. The formation of two reactive intermediates [4, favored in MeCN and 3, favored in MeCN/py] in combination with the product profiles of Table V is the basis for the proposed reaction pathways of Scheme III. Species 3 transforms methylenic carbons (>CH 2 ) to ketones (>O0) and dioxygenates arylolefins and acetylenes, and its precursor (species 2) epoxidizes aliphatic olefins. Combination of t-BuOOH and Co π (bpy) 2+ appears to form intermediates 5 and €; species 5 has similar reactivity to species 4, but species € is unique and necessary to account for the observed ROOBu-t products. In summary, the Co π (bpy) 2 */HOOH/(4:1 MeCN/py) system forms a reactive intermediate (3) that selectively ketonizes methylenic carbon, and as such is closely similar to the intermediate of the Fe n (PA) 2 /HOOH/(2:l py/HOAc) system and of related systems. We believe that the common feature is a stabilized-dioxygen intermediate rather than a hypervalent metal-centered carbon oxidant. The ability of Fe n (DPAH) 2 to activate 0 2 to an intermediate that has the same unique selectivity for hydrocarbon ketonization is further support for a common stabilized-dioxygen reactive complex. Several cobalt/dioxygen complexes exhibit oxygenase reactivity with organic substrates, which is consistent with the dioxygen formulation for species 3.

Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the foregoing specification or practice of the invention disclosed herein.

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