Metathesis of olefins is a process that is defined as the redistribution of alkylidene aoieties in a nixture of olefins to yield other olefins. A βtuple βxanple of olefin aetathesiβ is shown in equation I.

2 RHC-CHR'→ 'HC-CHR' + RHC-CHR Eq. I

The reaction proceeds by addition of an olefin to a catalyst having a aetal-carbon double bond. Three of the aost active aβtals used in classical olefin aetathesis are aolybdenua, tungsten and rheniua.

(Ivin, K.J., 01efin_Metathβ£ le, Acadeaic Press, London, 1983; Crubbs, R.H. in Ch'Siβ ry., Wilkinson, G. et _^ aL. (Eds.), Vol. 8, Fergaoon: Hew York (1982); Dragutan, V. et al.. Olefin

Olefins, 2nd Ed., Viley-Interscience: Hew York (1985); Leconte, M. et al. In Reactions,of.Coordinated Ligands. Brateraan, P.R. (Ed.), Plenua: Mew York (1986).)

Exaaples of aolybdenun (VI) alkylidene complexes (Murdzek, J.S. and R.R. Schrock, Organometalllcs 6_:1373 (1987); Kazan, G. et al. , Polymer.Cpnnun. 30;258 (1989)) and tungsten (VI) alkylidene coaplexes have been previously described (Schrock, R.R. et al. , J. Am. Chea. Soc. 110:1423 (1988); Feldaan, J. et_al. in Advances In Metal Carbene Chemistry, Schubert, U. (Ed.), Kluwer Aeadeaic Publishers, Boston: 1989, page ^' 323; Schrock, R.R. et al.. Macroaolecules 20:1169 (1987); Ginsburg, E.J. et al. , J. Aa. Chen. Soc.

111:7621 (1989); Swager, T.M. et_al. , J. An, _, Chen. Soc. 111:4413 (1989); Knoll, K. and R.R. Schrock, J. An. Chen__Soc_ 111:7989 (1989); Schlund, R. βt_al. , J__Am_ Chen. Soc. 111:8004 (1989)). Several of these coapounds have been shown to catalyze the aetathesls of olefins with an activity that can be controlled through the choice of the alkoxide ligand. For axanple, tungsten and aolybdenua catalysts reported by Schrock, R.R. (U.S. Patent Noβ. 4,681,956 and 4,727,215) have been shown to hoaogeneously aetathesize at least 250 equivalents of aethyl oleate. Though the reported nolybdenun and tungsten catalysts can aetathesize ordinary olefins (hydrocarbon chains) in good yield, they are limited in their usefulness as aetathesls catalyst for functionalized olefins due to their reactivity with the functional groups.

Several rhenium alkylidene complexes have also been reported (Edwards, D.S. et_al.. Organome allies 2:1505 (1983); Edwards, D.S., "Synthesis and Reactivity of Rhenium (VII) Neopentylidene and Neopentylidyne

Complexes", MIT Doctoral Thesis (1983); Horton, A.D. et *!• _» Organonetalllcs 6:893 (1987); Horton, A.D. and R.R. Schrock, Polyhedron 7:1841 (1988); Cai, S. et al. , J. An. Chea. Coaaun. , 1489 (1988). In particular, the Edwards references describe three rheniun conplexes represented by the fornula Re(C-t-Bu)(CH-t-Bu)(R), where R is a t-butoxide, triaethylsiloxide or neopentyl moiety. However, none of the previously reported rheniun coapounds showed any conflraable aetathesls activity in the absence of a co-catalyst or activator compound, even toward strained cyclic olefins, such as norbornene.

Heterogeneous rheniun catalysts (Re.O- deposited on silica and/or alunina mixtures) have been shown to metathesize aethyl oleate but for a limited duration before becoming inactive.

It would, therefore, be desirable to provide a homogeneous rhenlua catalyst for aetathesizlng olefins, particularly functionalized olefins, at a aolecular level which would be highly active, longer-lived than heterogeneous rheniua catalysts and tolerant of olefin functionalities.

Summary of the Invention

This invention pertains to four-coordinate rheniua (VII) compounds and to aethods for synthesizing such compounds. The rhenium compounds comprise a rhenium (VII) atom centrally linked to an alkylidene ligand, an alkylidyne ligand and two other ligands of which at least one ligand is sufficiently electron withdrawing

to render the rhenium atom electrophillc enough for metathesis reactions. Preferably, the electron with¬ drawing ligands are alkoxide groups.

These four-coordinate coapounds are well-defined, homogeneous and isolable and can be used to catalyze the aetathesls of ordinary (hydrocarbon chain) and functionalized olefins in the absence of a co-catalyst or "activator compound. The homogenous coapounds can also catalyze the polymerization of acetylenes and ring-opening oligomerlzation or polynerization of cyclic olefins, such as norbornene. The conpounds can also be used to make other metathesis catalysts that would otherwise be difficult to synthesize.

Detailed Description _. of _r the.Invention Four-coordinate rhenium (VII) compounds of this invention can be represented by Formula I:

tRe(CR ¹ )(CHR ² )(R ³ )(R )] _n I

wherein R is selected from the group consisting of an alkyl having 1 to 20 carbon atoms , an aryl having 6 to 20 carbon atoms , an aralkyl having 7 to 30 carbon atoms , halogen substituted derivative of each and

2 silicon-containing analogs of each ; R is selected from the group consisting of R or is a aubstituent re-

2 suiting froa the reaction of the Re-CHR moiety of the compound with an olefin that is being netathesized; R and R are individually selected froa groups consisting of R , a halogen , triflate , and concatenated coabi- nations of R 3 and R 4 , wherein R 3 and R 4 individually nay contain alkoxide oxygen atoms which are bound to

the rheniua aton; n is a positive integer (preferably one or two); and provided that when R 1 and R2 are t-butyl and R 3 and R4 are the same, then R3 and R4 are groupa other than t-butoxide, trinethylsiloxide, nβo- pentyl or a halogen.

Rheniua coapounds of the above foraula are four coordinate coapounds having a rheniua (VII) aton which is centrally linked to four coordinating ligands. Centrally linked is intended to aean that the rhenium atom is central to and attached to each of these ligands. The four-coordinate coapounds are characterized as having both alkylidyne (Re«CR ) and alkylidene ( β-CHR ² ) ligands. The alkylidyne ligand is relatively inactive while the alkylidene ligand plays an integral role in the aetathesls reaction and will be described in aore detail below. Exaaples of R 1 and R2 include but are not Halted to phenyl, t-butyl,

1-aethyl-l-phenyl-ethyl, triaethylsilyl, triphenyl- nethyl, triphenylsilyl, tri-t-butyl, tri-t-butylsilyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl and.

2,6-dimethylphenyl. The renaining two ligands (R 3 and R4) can be any substituent which is sufficiently electron withdrawing enough to render the conplex active (i.e., render the rheniun aton sufficiently alectrophilic) for aetathesls reactions. While it is preferable that both ligands are electron withdrawing, the coapounds of this invention aay contain only one electron withdrawing ligand which is sufficiently strong enough to render the complex active for aetathesls. A aetathesls catalyst having significant aetathesls activity is one

that can effect the metathesis of an ordinary or functionallzed olefin at room temperature at a rate of at least one turnover per hour, in the absence of a co-catalyst or activator coapound.

The activity of the catalyst can be regulated by the nature of the electron withdrawing ligands. For instance, an increase in catalytic activity can be achieved using a ligand which is strongly electron withdrawing. Preferably, R 3 and R4 are both alkoxide ligands in which the alcohol corresponding to the electron withdrawing alkoxide ligands should have a pKa of about 9 or below. Suitable electron withdrawing ligands which fall within this range Include phenoxide, hexafluoro-t-butoxide and diisopropylphenoxide. Other exaaples of preferred electron withdrawing ligands include alkoxides containing 2,6-diaethylphenyl, 2,4,6- trinethylphenyl, 2,6-diisopropylphenyl, pentafluoro- phenyl, 1-aethyl-l-phenyl-ethyl, 2,6-dlchlorophenyl, perchlorophenyl, trlphenylnethyl, triphenylsilyl, tri-t-butylsilyl, perfluoro-2-aethyl-2-pentyl, tri- fluoro-t-butyl (CF ₃ (CH,) ₂ C) , hexafluoro-t-butyl

((CF-),CH-C) and perfluoro-t-butyl. Examples of con- catenated R 3 and R4 groups are pinacolate,

2,6-diaethyl-2,6-heptanedlolate and propan-1,3-diolate. Rheniun conpounds of Fornula I are typically

■onoaers. However, they can fora diaers, oligoners or polymers if the R 3 and/or R4 substituents are small enough to permit bridging of two or more aetal centers.

This is commonly observed when the ligands are halogen atoms or small alkoxides. These compounds can be converted to aonomeric rhenium compounds by substi¬ tuting the bridging ligands with alkoxide or alkyl ligands. The substituted alkoxide or alkyl ligands should be of a sufficient size to cause the bridge between two or aore rheniua coapounds to break. Some examples of these rhenium compounds include the following where t-Bu represents t-butyl:

[Re(C-t-Bu)(CH-t-Bu)Cl ₂ ] ₂

[Re(C-t-Bu)(CH-t-Bu)(2,6-dimethylaniline)Cl ₂ ] ₂

[Re(C-t-Bu)(CH-t-Bu)I ₂ ] ₂ .

Complexes of this invention can optionally have one or aore (preferably one or two) electron donor ligands bound to the rheniua atoa. The donor ligands can be ethers (e.g. diethyl ether, tetrahydrofuran, 1,2-diaethoxyethane, 1,4-dioxane) , nitrogen-containing bases (e.g. pyridine, quinuclidlne, t-butylaaine, 2,6-diaethylaniline) , and phosphorus-containing bases (e.g. triphenylphosphine, diaethylphenylphosphlne) .

The resulting complex is often isolable in the crystal¬ line state. In solution, however, aost donor ligands are lost spontaneously, or are displaced readily by one or aore olefins that are being netathesized and, therefore, do not prevent the aetathesls reaction.

In a preferred eabodiaent, the compounds of the invention are represented by Formula II:

Re(CR ¹ )(CHR ² )(OR ³ ) ₂ II

where R1, R2 and R3 are defined above. Examples of some particularly preferred bis-alkoxide rhenium compounds of Foraula II include the following where t-Bu represents t-butyl:

Re(C-t-Bu) (CH-t-Bu) (2,6-diisopropylphenoxide) ₂ Re(C-t-Bu)(CH-t-Bu)(ortho-t-butylphenoxide) ₂ Re(C-t-Bu)(CH-t-Bu)(trifluoro-t-butoxide) ₂ Re(C-t-Bu) (CH-t-Bu) (hexafluoro- -butoxide). Re(C-t-Bu) (CH-t-Bu)(2,6-diaethylphenoxide) ₂ .

The rheniua compounds of this invention can be used as catalysts for the aetathesls of ordinary olefins (hydrocarbon chain) and functionallzed olefins in a hoaogeneous phase. They can be utilized as homogeneous catalysts or can be attached covalently to inorganic (e.g. silica) or organic (e.g. polystyrene) supports to yield analogous heterogeneous catalysts. They can also function as catalysts for polyaerization of acetylenes and ring-opening aetathesls oligoaeri- zation or polyaerization of cyclic olefins, such as norbornene. Since they are readily active compounds, they can catalyze aetathesls of olefins in the absence of a co-catalyst or activator compound, such as Me.Sil or Lewis acids.

According to the invention, an olefin can be netathesized by contacting it with a hoaogeneous rheniun aetathesls catalyst in a suitable solvent, under conditions sufficient to aetathesize the olefin and produce one or aore aetathesls products. The products can then be recovered using known separation techniques or can be further aetathesized.

The aetathesls reaction proceeds by addition of an

2 olefin to the rheniua-carbon double bond (Re-CHR , a rheniua-alkylidene aoiety) to fora a aetallacyclobutane ring (as shown below) vhich then releases an olefin to fora a new aetal-alkylidene aoiety derived froa the

2 olefin. Since the Re-CHR aoiety of the coaplex is

2 intiaately involved in the catalytic reaction, the CHR ligand is replaced by any other alkylidene fragaent froa the olefins that are being aetathesized. As a result of this exchange in the alkylidene group, one can use the aethods of this invention to produce rheniua catalysts having alkylidene groups which are otherwise difficult to synthesize.

Metallacyclobutane complexes which are interaediates in the aetathesls reaction can also be utilized as aetathesls catalysts and as catalysts for the oligoaerization of acetylenes. The siaplest aetallacyclobutane interaediate is represented by Foraula III.

(R ³ 0) 2,(R ¹ C)ReCH2„CH2,CH 4, III

During a aetathesls reaction, the interaediates are in equilibriun with the alkylidene complex and the free olefin as depicted in Equation 2.

(R ³ 0) ₂ (R ¹ C)ReCH ₂ CH ₂ CH ₂ ^(R ³ 0) ₂ (R ¹ C)Re-CH ₂ + H ₂ C-CH ₂ Eq. 2

The position of the equilibrium in Equation 2 will depend upon the donor ability of the solvent aedium,

and in the aore general case where alkyl or function¬ allzed substituentβ are present in the aetallacyclo¬ butane and alkylidene coaplexes, upon the electronic and steric properties of those substituents. The rheniua coapounds of this invention can be synthesized by reacting a coapound of the foraula Re(MAr) ₂ (CH ₂ R ¹ )(CHR ² ) where Ar is selected froa the group consisting of 2,6-diae hylphenyl, 2,6-dichloro- phenyl and diisopropylphenyl, with HC1 in a suitable solvent under conditions sufficient to produce lRe(CR ¹ )(CHR ² )(H ₂ NAr)Cl ₂ ] ₂ . However, when Ar is diisopropylphenyl, the product of this reaction is a aonoaer. When R 1 and R2 are both t-butyl, the starting compound can be prepared by the sequence of reactions as described in the literature (Horton, A.D. and R.R. Schrock. Polyhedron 7:1841 (1988)). Other βtarting materials can be synthesized according to the aethods described in Exaaples 1-3. The resulting coapound is then reacted with a rigid chelating diaaine in a suitable solvent under conditions sufficient to produce Re(CR ¹ )(CHR ² )(Y)Cl ₂ , where Y represents the diamine. Preferably, the diamine is phenylenediamine or 1,8-diaminonaphthalene. However, any rigid chelating diaaine will react with the rhenium complex to produce the desired product. The product is then reacted with HC1 gas under conditions sufficient to yield [Re(CR ¹ )(CHR ² )Cl ₂ ] _n . This complex is further reacted with a sodiua, lithiua or potassiua salt of an alkoxide under conditions sufficient to produce the rheniua catalyst. The electron withdrawing nature of the alkoxide should be sufficient enough to render the rheniua atom active for metathesis.

An alternative method for synthesizing several rhenium compounds of this invention can be performed by reacting compounds of Formula II with excess HC1 or HI to produce the dlhalide, [Re(CR ¹ )(CHR ² ) ₂ l _n , where X represents a halogen atoa, such as chlorine or iodine. The resulting coapound can be used as a precusor coapound for preparing other rheniua coapounds of Forauϊa II by reacting the dlhalide with a sodiua, lithiua or potassiua salt of an alkoxide under conditions sufficient to produce the desired rhenium catalyst. Preferably, the starting rhenium compounds

3 have OR ligands, such as t-butoxide and triaethylslloxide. When neophyl analogs are used, the reaction can be perforaed in diaethoxyethane (dme) to fora the product Re(CR ¹ )(CHR )X ₂ (dae) which can subsequently be used to produce the desired rhenium coapound as previously described.

A typical synthesis is illustrated by the sequence of reactions shown in Equations 3, 7-9. An alternative synthesis is represented by Equations 3-6. These reactions can be perforaed in suitable solvents (e.g., dimethoxyethane, methylene chloride, pentane, toluene, tetrahydrofuran (THF) , or dichloromethane) and at a temperature range of froa about -78*C to about 25*C. The synthesized products are recovered by filtering the reaction aixture and removing all solvents and readily volatile products froa the filtrate _.n vacuo.

In the following equations below, t-Bu-t-butyl,

Me-methyl, Ar-2,6-dimethylphenyl, 0Tf-0S0 ₉ CF,, pda-

3 1,2-phenylenediamine and R is previously defined.

2 (ArN) ₂ Re(CH-t-Bu)(CH ₂ -t-Bu) + 6HCl(g) -♦ Eq. 3

2 ArNH ₃ Cl + [Re(C-t-Bu) (CH-t-Bu) H ₂ NAr)Cl ₂ J ₂

0.5[Re(C-t-Bu) (CH-t-Bu)(H ₂ NAr)Cl ₂ ] ₂ +2 H _j N-t-Bu -♦ Eq. 4 ArNH ₂ + Re(C-t-Bu) (CH-t-Bu) (H ₂ N-t-Bu) ₂ Cl ₂

Re(C-t-Bu)(CH-t-Bu)(H ₂ N-t-Bu) ₂ Cl ₂ + 2 LiOR ³ -» Eq. 5 2 LiCl + H ₂ N-t-Bu + Re(C-t-Bu)(CH-t-Bu)- (0R ³ ) ₂ (H ₂ N-t-Bu)

Re(C-t-Bu)(CH-t-Bu)(0R ³ ) ₂ (H ₂ N-t-Bu) + MeOTf - Eq. 6 t-Bu-NH ₂ MeOTf + Re(C-t-Bu) (CH-t-Bu) (0R ³ ) ₂

0.5[Re(C-t-Bu)(CH-t-Bu)(H ₂ NAr)Cl ₂ ] ₂ + pda ^■ * Eq. 7 ArNH ₂ + Re(C-t-Bu)(CH-t-Bu)(pda)Cl ₂

Re(C-t-Bu)(CH-t-Bu)(pda)Cl ₂ + 2HCl(g) -♦ Eq. 8 pda ^* 2HCl + [Re(C-t-Bu) (CH-t-Bu)Cl ₂ ] _n

[Re(C-t-Bu)(CH-t-Bu)Cl ₂ ] + 2L10R ³ - Eq. 9 Re(C-t-Bu)(CH-t-Bu)(OR ³ ) ₂ + 2L1C1

This invention is further illustrated by the following non-limiting examples.

In order to avoid the presence of oxygen and aoisture, the latter being especially destructive, the following examples were carried out in an ataosphere of dry aolecular nitrogen using dry, pure solvents. Several of the pure, isolated products, however, are stable to oxygen and water for extended periods (several weeks).

In the exaapleβ below, t-Bu-t-butyl, Me-aethyl, Ar-2,6-diaethylphenyl, OAr'-2,6-diisopropylphenoxide, pda-l,2-phenylenediamine, py-pyridine and 0Tf-0S0 ₂ CF ₃ .

Example 1 Preparation of Re(HAr) ₂ Cl.py

To a stirring suspension of Re ₂ °7 * ^1,0 S» ² - ⁰⁷ amol) in 50 al aethylene chloride was added sequen¬ tially 2,6-diaethylaniline (1.84 al, 12.4 aaol) and pyridine (3.05 al, 78 aaol) resulting in a dark red solution. Chlorotriaethylsilane (4.8 al, 38 amol) was then added, the solution darkened and all solids dissolved after 20 ainutes. The reaction was stirred at rooa teaperature two hours and then the dark green solution was reduced to dryness. The solids were extracted with boiling benzene and filtered through Celite* (hydrated diatoaaceous aaorphous silica). Concentration of the filtrate and addition of pentane afforded Re(HAr) ₂ Cl.py as a dark green crystalline solid (2.2 g, 86%) whose ^X H NMR was identical to a compound previously reported by Horton, A.D. and R.R. Schrock, Polyhedron 7:1841 (1988).

A siailar aethod can be used to produce Re(2,6- dilsopropylaniline) ₂ Cl-py where 2,6-dϋsopropyliaido is added in place of 2,6-diaethylaniline.

Example 2

Preparation of Re(N-t-Bu) ₂ Cl ₃

To a stirring suspension of fc* ₂ °7 (*<0 S> 8.26 amol) in aethylene chloride at 0*C was added chlorotriaethylsilane (14.8 al, 115 aaol) and then

t-butylaalne (17.4 al, 165 aaol) was added quickly dropwise. The solution instantly turned bright yellow and a white precipitate containing He.CNH^l foraed. After stirring the solution of crude Re(N-t-Bu) ₃ - (OSiMe.) for 20 ainuteβ at rooa teaperature, excess HCl(g) was bubbled through the solution. The resulting dark orange solution was then filtered and the filtrate reduced to dryness and extracted with ether. The ether extracts were then concentrated and cooled to afford large orange crystals of Re(N-t-Bu) ₂ Cl. (5.7 g, 79%) whose H MMR was identical with that previously re¬ ported by Edwards, D.S. β_ aL. , Organometallies 2:1505-1513 (1983).

Example_ 3 Preparation of fRe(C-t-Bu).t;CH-t-Bu) (H ₂ NAr)Cl ₂ l ₂

A solution of Re(NAr) ₂ (CH-t-Bu)(CH ₂ -t-Bu)(4.64 g, 8.2 aaol) (Horton, A.D. and R.R. Schrock, Polyhedron 2:1841 (1988)) in diaethoxyethane was cooled to 0*C and treated with HCl(g) (590 al, 26 aaol). The orange solution iamediately darkened and a white precipitate was observed. After stirring at 25*C for 2.5 hours, the solvent was reaoved JLn vacuo leaving a beige powder that was extracted away froa insoluble ArNH.Cl with benzene and filtered through a pad of Celite". The filtrate vas then reduced to dryness In vacuo and washed with pentane to yield a faintly orange powder (3.4g, 80% yield).

Anal. Calcd for Re ₂ C ₃₆ H ₆₍₎ Cl ₄ N ₂ : C, 41.77; H, 5.84; H, 2.71. Found: C, 42.11; H, 6.00; N, 2.50.

Partial H NMR (C,D ₆ ) (The compound exists as two isomers) S 14.49, 14.48 (β, 4, CHCMe ₃ ), 2.37, 2.32, 2.28, 2.17 (β, 6 each, 2,6-Me ₂ -C _fi H ₃ ) , 1.39, 1.38, 1.08, 1.01 (β, 18 each. CMe ₃ ). Partial ^Ϊ3 C(THF-dg, major isoaer) S 292.1 (CCMβ _j ) , 286.3 (CHCMβ _j , J _CH -130 Hz), 31.5, 28.5 (CMe ₃ ).

Exaaple 4

Preparation of Re(C-t-Bu)(CH-t-Bu)(HgN-t-Bu) ₂ Cl _£

To an orange solution of (Re(C-t-Bu) (CH-t-Bu) - (H ₂ NAr)Cl ₂ ] ₂ (0.5g, 0.48 aaol) in tetrahydrofuran was added t-butylaainβ (1.0 al). The reaction aixture was stirred for twelve hours at rooa teaperature. The solution was then reduced in voluae to 5 al and pentane was added, causing the product to crystallize froa the reaction aixture as fine silky needles. (0.49g, 93% yield) . The product aay also be prepared in the same fashion by adding t-butylaninβ directly to the crude reaction product in Example 3.

¹ H NMR (CD ₂ C1 ₂ ) S 14.52 (s, 1, CHCMe ₃ ), 4.63, 4,23 (d, 2 each, NH..CHe ₃ ), 1.40, 1.36 (s, each 9, CMe ₃ ),

1.18 (s, 18, H ₂ NCMe ₃ ). Partial ¹³ C NMR (CD _j Cl _j , -60*C) 6 298.6 (CHCMe ₃ , J _CH -131 Hz), 286.2 (CCMβ _j ) , 29.5 (NH ₂ CMe ₃ ), 28.8, 31.0 (CMβ _j ).

Example 5 Preparation of Re C-t-Bu _CH÷t÷B^l_(0Ar_ ^• ) ₂ (H _; N-t-Bu) To a -40 ^# C solution of Re(C-t-Bu)(CH-t-Bu)(H _j N- t-Bu) ₂ Cl ₂ (2.0g, 3.7 aaol) in CH ₂ C1 ₂ was added solid lithiua 2,6-diisopropylphenoxlde aonoetherate (1.9g,

7.4 amol). The orange solution gradually became bright yellow and was stirred at room temperature for 40 ainutes. The volatilββ were then reaoved in vacuo and the solid residue extracted with pentane. The pentane extract was filtered through a pad of Celite". Concen¬ tration and cooling of the filtrate yielded large yellow cubes (2.0g, yield - 73%). Partial H NMR (C,D,, varies with concentration) • 11.15 (s, 1, CHCMe ₃ ), 3.41 (sept, 4 CHMe ₂ ) , 1.48, 0.56 (s, 9 each, CMe ₃ ). Partial ¹³ C NMR (CD _j Cl _j , -60'C) S 293.1

(CCMe ₃ ), 234.4 (CHCMβ _j , J _CH - 123 Hz), 51.6, 50.8, 43.9 (CHe ₃ ).

Example 6

Preparation o _^ Re^C^t^Bu)(CH-t-Bu) p r ) ₂ To a solution of Rβ(C-t-Bu) (OAr' ) ₂ (H ₂ N-t-Bu)

(25ag, 0.033 aaol) in C ₆ D ₆ (c.a. 700 μl ) was added (via syringe) aβth l triflate (3.8 pi, 0.033 aaol). A white precipitate foraed within a few ainutes and was reaoved by filtration. The H NMR indicated a quantitative yield of Re(CCMe ₃ ) (CHCMβg) (OAr* ₂ - This coaplex was stable in solution indefinitely, but was not stable in the solid state. This coaplex is typically generated in ϋtu for further reactions. Partial H (C-D,) S 10.72 (s, 1, CHCMe ₃ ), 3.56 (sept. 4, CHMβ _j ) , 1.19, 0.99 (s, 9 each, CMβ ₃ ). Partial ¹³ C(C _fi D ₆ ) S 293.6 (CCMe ₃ ) , 240.1 (CHCMe ₃ , J _CH - 125 Hz), 27.9, 23.6 (CMe. ₃ ).

Example.7

Preparation of Re(C-t-Bu CH^t^Bullp a Cl ₂

To a solution of fRβ(C-t-Bu)(CH-t-Bu)(H ₂ NAr)Cl ₂ ] ₂ (1.5g, 1.45 aaol) in tetrahydrofuran (THF) was added solid 1,2-phenylenediaaine (0.32g, 2.9 amol). The solution was stirred at rooa teaperature 25 ainutes and the solvent reaoved ^n vacuo. The solid residue was washed with pentane and then twice repreeipitated froa THF/pentane to remove residual aniline. A pale orange product was obtained in 95% yield (1.39g). Partial H

NMR (C,D,) 6 13.42 (β, 1, CHCMe,), 1.62, 1.36 (s, 9 each, CMe ⁶ ₃ ). Partial 1 ^A 3 ^J C (~CD _j Cl _j ) S 295.6 (CCMe ₃ )

292.0 (CHCMβ ₃ , _CH - 118 Hz), 31.2, 28.1 (CMβ _j ).

Example 8

-? _. -SEa£* _.- ^PP _, .P ^f _^ lRs CiJt ₂ u) CH^t-Bu Cl ₂ l

Addition of HCl(g) (98 al, 4.4 aol) via syringe to a dimethoxyethane solution of Re(C-t-Bu)(CH-t-Bu) (pda)- Cl. (l.Og, 1.98 aaol) resulted in the iaaediate for- aation of a white precipitate at rooa teaperature. After 20 ainutes, the precipitate was reaoved by filtration and the orange filtrate reduced to dryness. The resulting solid was washed with pentane to yield a pale orange powder (0.67g, 85%) that was insoluble in all but strongly coordinating solvents. H NMR

(THF-d _g ) i 13.26 (s, 1, CHCMe ₃ ), 1.35, 1.26 (s, 9, CMe ₃ ). Partial ¹³ C NMR (THF-d _g ) 6 239.9 (CCMβ _j ), 285.8 (CHCMe ₃ , J _CH - 125 Hz), 31.4, 28.4 (CMe ₃ ) .

Example 9

Preparation of Re(C-t-Bu) (CH-t-Bu) (0C(CF ₃ 1 ₂ CH ₃ 2 ₂

To a -40*C THF solution of [Rβ(C-t-Bu) (CH-t-Bu)- Cl ₂ ] (250 ag, 0.63 aaol) was added solid potassium hexafluoro-t-butoxide (277 ag, 1.26 aaol). The orange solution darkened as it was stirred at rooa teaperature for 45 ainutes. The solvent was then reaoved in vacuo and the residue extracted with pentane and filtered through a pad of Celite ¹¹ . The resulting orange solution was reduced to dryness, quantitatively yielding Re(C-t-Bu)(CH-t-Bu) (0C(CF ₃ ) ₂ CH ₃ ) ₂ as an orange oil. Partial ^X H NMR (CgDg) e 11.08 (s, 1. 1.15. 1.13 (β, CMe ₃ ). Partial ^I3 C NMR (CgD .8 (CCMe ₃ ), 248.8 (CHCMβ _j , J _CH -127 Hz), 31.9, 29.9 (CMe_ ₃ ) .

Example 10

Metathesis of cls-2-pentene

To 35 ag Re(C-t-Bu)(CH-t-Bu)(0C(CF ₃ ) ₂ CH ₃ ) ₂ (0.05 aaol) in 5 al of benzene was added 100 equivalents of cis-2-pentene (546 μl , 5 aaol). After 150 ainutes, gas chroaatography (GC) analysis showed an approxiaately 1:2:1 aixture of 2-butenes, 2-pentenes and 3-hexenes. An additional 100 equivalents of cis-2-pentene (546 μl, 5 mmol) were then added and equilibriua was reestab¬ lished in less than 30 ainutes. A H NMR study of the reaction of Re(C-t-Bu) (CH-t-Bu) (0C(CF ₃ ) ₂ CH ₃ ) ₂ and 10 equivalents ciβ-2-pentene showed the presence of propagating ethylidene and propylidene species even after two days in solution.

Example 11

Metathesis of Methyl Oleate

To 20 ag [Re(C-t-Bu)(CH-t-Bu)Cl ₂ ] _n (0.05 aaol) as a suspension in 5 al CH.Cl. was added solid potassiua hexafluoro-t-butoxide (22 ag, 0.10 aaol). After 30 ainutes all the solids had dissolved to yield a yellow solution, and an internal standard of aesitylene and 50 equivalents of aethyl oleate (850 μl, 2.5 aaol) were added. After 12 hours, the equilibrium (-1:2:1) between Me(CH ₂ ) _? CH-CH(CH ₂ ) ₇ β, Me(CH ₂ ) ₇ CH-CH(CH ₂ ) ₇ C0 ₂ Me and Me0 ₂ C(CH ₂ ) ₇ CH-CH(CH ₂ ) ₇ C0 ₂ Mβ was established. The catalyst solution was then allowed to stand undisturbed for 24 hours and then an additional 50 equivalents aethyl oleate (850 μl, 2.5 aaol) were added. Equlli- briua was reestablished after 7.5 hours. The products of the aetathesls were identified by coaparison with authentic GC traces. The activity of this catalyst is at least 200 equivalents of aethyl oleate and the catalytic solutions are stable for at least three days.

Example 12

Metathesis of Methyl_01eate Accelerated by_Initial Reaction with 3^Hexene

To 15 ag [Re(C-t-Bu)(CH-t-Bu)Cl ₂ 3 _n (0.038 amol) as a suspension in 2 al CH-Cl, was added solid potassiua hexafluoro-t-butoxide (17 ag, 0.076 aaol). After 30 ainutes, the solution was clear yellow and 10 equiva¬ lents of cis-3-hexene (47 μl, 0.38 aaol) were added. After stirring for 7 hours, 3 al CH ₂ C1 ₂ , an internal standard of 1-phenyloctane and 50 equivalents of aethyl

oleate (640 μl, 1.9 amol) were added. Equilibrium was established after 150 ainutes, and then an additional 100 equivalents of aethyl oleate (1280 μl, 3.8 amol) were added. After six hours at rooa teaperature, equllibrlun (-1:2:1) vas again achieved.