This invention relates to the field of polymerization catalysts and particularly refers to a catalyst and its uses as defined in the claims.

Background prior art

Nowadays a high amount of plastics that are produced are petrol-based. Since petrol is a nonrenewable resource, production of polymers from other raw materials is essential for a more sustainable future. Furthermore, the increasing levels of released C0 ₂ make it an excellent candidate as C1 building block for the production of polymers. Polycarbonates are attractive materials with a wide range of applications and, indeed, the potential for C0 ₂ capture and storage in them reaches 30 wt% and 50 wt% for the copolymers with cyclohexene oxide and ethylene oxide, respectively. In the last decades, great efforts have been devoted to the catalytic copoiymerization of C0 ₂ with epoxides to form polycarbonates, since the initial discovery by Inoue et al. in 1969. However, activating C0 ₂ is still a challenge. Ring-opening- polymerization proved to be a suitable strategy for which various promising catalysts have already been developed. Although some proved to be active at the most desirable pressure of one atmosphere in C0 ₂ , they have several different limitations. These include a low chemoselectivity for the target polycarbonate, especially at low pressures, the use of toxic metals and additives, low TON and TOF values, and low catalyst isolation yields.

For example, Ding et al. (Chem. - A Eur. J. 2005, 11 (12), 3668-3678) disclose a dinuclear zinc catalyst which is based on phenol-bridged bis(a.a-diarylprolinol) ligands. Therein, the ligands are fixed by the phenol-moiety. Similar ligands are disclosed in CN1786004A and CN100358902C.

Nozaki et al. (J. Am. Chem. Soc, 2003, 125 (18), pp 5501-5510 and Pure and Applied Chemistry 2004, 76, 541-546) disclose a diaryl(pyrrolidin-2-yl) ligand for preparing a dimeric zinc complex. Two zinc centers were bridged by oxygen atoms to form a Zn ₂ 0 ₂ four-membered ring with a syn relationship between the two ethyl groups on the zinc centers. The dimeric zinc complex was an active catalyst (yield of 95% of an alternating copolymer with 80% ee) for asymmetric alternating copoiymerization of cyclohexene oxide and C0 ₂ . Nozaki et al. further disclose Zn-imine oxazoline ligand complexes as catalysts, wherein improved enantioseiectivity of 80% was achieved by using a dimeric zinc complex in which one of the two zinc atoms is attached to an ethoxy group while the other is to an ethyl group (Pure and Applied Chemistry 2004, 76, 541-546). Rieger et al. (Coordination Chemistry Reviews 2011 , 255, 1460-1479) started from the Nozaki et al. catalysts and assumed that the enantiomerica!ly pure ligand dissociates from the active metal site and the chiral information around the zinc center is lost. To overcome this problem, ethanol was added to the reaction mixture, which lead to the formation of new Zn-OR moieties. These new Zn-alkoxide groups could initiate the copolymerization, whereas ethyl groups were unable to initiate the reaction.

WO2009130470 discloses a bimetallic catalyst with macrocyclic fixed ligands based on the Trost catalysts'. Coates et al. (Chem. Rev. 2016, 116, 15167-15197), Yeung et al. (Polym. Chem. 2014, 5, 3949-3962), Lu et al., (Macromolecules 2015, 48 (19), 6941-6947), Trott et al. (Philos. Trans. A. Math. Phys. Eng. Sci. 2016 , 374 (2061 ), 20150085) and Konno et al. (Green Chemistry, 2003, 5, 497-507) provide some background regarding ring-opening copolymerization of epoxides and cyclic anhydrides and carbon dioxide-epoxide copolymerization.

Cohen et al. (Dalton Trans. 2006, 1, 237-249) discloses Salen-based Co(lll) complexes for copolymerization of cyclohexene oxide and carbon dioxide.

Accordingly, desirable attributes for such catalysts are high copolymerization activity at low CCy-pressure, as well as chemo- and stereo-control over the formed polymer. Of course it is also important that the catalysts are stable, and easy and cheap to prepare.

Though some catalysts for C0 ₂ /epoxide copolymerization are available, they suffer from deficiencies, and it is an object of the present invention to provide catalysts that overcome at least one of the above problems.

Summary of the invention

The present invention refers to novel proline-derived zinc complexes capable of e.g., copolymerizing C0 ₂ and epoxides. The catalysts may achieve a high chemoselectivity even at low pressures of C0 ₂ with high TONs and TOFs. The zinc complexes may address the issue of stereoselectivity and give an isotactically-enriched secondary structure of the polymer. By way of example, zinc complex 1 can be prepared in just three steps with 97 % overall yield from commercially available chemicals. Accordingly, the zinc complexes described herein may be easier, thus cheaper, to prepare than the prior art catalysts (see e.g., preparation of complex 1 in Figure 1 ).

It has unexpectedly been found that the Nozaki catalyst (see above citations) can be improved if an alkoxide as part of the ligand, e.g., ethanolat (EtO-) is brought in vicinity of the metal or coordinates with the metal. This nucleophile group improves the polymerization, in particular helps starting the polymerization. One advantage which is provided by the catalysts described herein is that the alkoxy-group of the ligand arm, which is attached to the proline N-atom (see e.g., catalyst 1 in Figure 1 ), can coordinate with the metal, but can, additionally, act as a nucleophile in the polymerization, i.e. can participate in the different transition states or intermediates of the polymerization, which may contribute to an improved efficiency of the catalyst. This is achieved by the flexible ligand arm and is in contrast with the rigid prior art catalysts described above, where e.g., a phenol-OH group in the ligand bridge merely serves as a chelate but has no nucleophilic activity. Without wishing to be bound to this theory, it is considered that this flexible nucleophile arm ensures that all claimed catalysts provide desired properties. In contrast, prior art catalysts require the addition of a nucleophile such as ethanolate for coordination or as an additional solvent or reactant to start/enable the polymerization.

As shown for the zinc catalyst 1 , the complexes described herein may improve stereo selectivity. In addition, the complexes may require no or low C0 ₂ overpressure (preferably 1 bar in C0 ₂ (wherein the pressure is preferably set by evacuation of the reaction vessel and then filling it with C0 ₂ until the desired pressure is reached). The catalysts described herein may not require high pressures, as it is the case for the Nozaki catalyst (30 atm).

Accordingly, the catalysts may produce polycarbonates selectively from neat cyclohexene oxide under 1 bar of C0 ₂ pressure at temperatures above 50°C. Surprisingly, at 80 °C reaction temperature, TONs of 1684 and TOFs up to 149 h ^"1 were achieved, while producing an isotactic-enriched polycarbonate with a probability P _m of 65 % for the formation of a meso diad. Accordingly, the catalysts may provide quantitative polymerizations with high TONs and TOFs values (TON = molar number monomer units consumed divided by the molar number of catalysts, assuming an active L ¹ ₂ Zn ₂ unit, TOF = TON/t, with t being the considered period of the experiment). The catalysts may be used for various different polymerization and or co-polymerization reactions and are not limited to epoxide copolymerization. In particular, the catalysts can be used for direct polycarbonate synthesis or polyurethane synthesis as well as for performing the first step in the polycarbonate synthesis to perform an intermediate by using C0 ₂ with atmospheric pressure and without using toxic phosgene. Lower reaction temperatures and gas pressures make the polymerization cheaper. The catalysts can be used in the chemical industry as well as in plastics industry, in particular for preparing polycarbonates and polyurethanes. It can be used for binding C0 ₂ . Advantageously, waste C0 ₂ from other processes can be used, such as from ethylene oxide synthesis in PET production.

Description of the Fipures

Figure 1. Synthesis of the proline derived zinc catalyst 1 ; different isomers of L ¹ ₂ Zn ₂ are possible.

Figure 2. Molecular structures of complex 1 in solid state (different isomers of [L ¹ ₂ Zn ₂ ] ₂ are possible). Hydrogen atoms are omitted for clarity.

Figure 3. ¹ H NMR spectrum in CDCI ₃ of the (S)-3-(2-(hydroxydiphenylmethyl)pyrrolidin-1- yl)propan-1 -ol.

Figure 4. ¹³ C NMR spectrum in CDCI ₃ of (S)-3-(2-(hydroxydiphenylmethyl)pyrrolidin-1 - yl)propan-1 -ol.

Figure 5. Averaged PCHC concentration vs. time of the copolymerization of CHO and C0 ₂ at 80°C applying zinc catalyst 1 (entries 1 -3 of Table 1 ). Samples were taken from the reaction solution.

Figure 6. Jordi Bures plot of the performed polymerizations using zinc catalyst 1 while assuming a L ¹ ₂ Zn ₂ species. Samples were taken from the reaction solution. Polynomial fit second order.

Figure 7. PCHC formation by using zinc catalyst 1 monitored by in situ IR measurement at the increase of the band at 1750 cm ^'1 and correlated with the samples taken from the reaction solution. [CHO]:[cat] = 1500, 1 bar C0 ₂ , 80 °C. Reactions with different content of water in the reaction vial.

Figure 8. [PCHC] against time (n=0), [CHO]:[cat.]=1 : 1500. Product formation against time of the copolymerization of CHO and C0 ₂ applying zinc catalyst 1 . Samples were taken from the reaction solution. Entries marked with TMS were performed with TMS protected glass ware. Figure 9. [PCHC] against time (n=0), [CH0]:[cat.]=1 : 1000. Product formation against time of the copolymerization of CHO and C0 ₂ applying zinc catalyst 1. Samples were taken from the reaction solution. Entries marked with TMS were performed with TMS protected glass ware. Figure 10. [PCHC] against time (n=0), [CHO]:[cat.]=1 :2000. Product formation against time of the copolymerization of CHO and C0 ₂ applying zinc catalyst 1. Samples were taken from the reaction solution. Entries were performed with TMS protected glass ware.

Figure 11. Selected region of the ¹³ C NMR spectrum in CDCI ₃ of the polycarbonate obtained from the polymerization of entry 1 of table "Performed polymerizations in TMS protected glass ware".

Figure 12. Molar mass distribution of entry 1 of table "Performed polymerizations in TMS protected glass ware" obtained by GPC in THF with toluene as internal standard. Μ _π : 2.344E+3 g/mol. M _w : 2.907E+3 g/mol. D: 1.240.

Figure 3. Table regarding performed polymerizations with zinc catalyst 1 without TMS protected glass ware. IR in situ measurement was performed.

Figure 14A. Part 1 of the table regarding performed polymerizations with zinc catalyst 1 in TMS protected glass ware.

Figure 14B. Part 2 of the table regarding performed polymerizations with zinc catalyst 1 in TMS protected glass ware.

Figure 14C. Part 3 of the table regarding performed polymerizations with zinc catalyst 1 in TMS protected glass ware.

Figure 15. Cobalt complex in solid state, which was synthesized using KH and CoBr ₂ of Example 6.

Figure 16. Molecular structure of a nickel(ll) complex in solid state of Example 7.

Figure 17A. ¹ H NMR spectrum of dissolved crystalline material of L ¹ ₂ Ni ₂ in CDCI ₃ of Example 7. Figure 17B. ¹³ C NMR spectrum of dissolved crystalline material of L ¹ ₂ Ni ₂ in CDCI ₃ of Example 7.

Figure 8A. Preparation of the ligand of Example 8.

Figure 18B. Scheme for the preparation of a zinc catalyst according to Example 10.

Figure 19. ¹ H NMR spectrum of the ligand material obtained in Example 10.

Figure 20A. Synthesis of compounds A and B of Example 1 1.

Figure 20B. ¹ H NMRs of compounds A and B of Example 1 1.

Figure 21 A. Possible further route for preparing ligands (Example 12).

Figure 21 B. CF ₃ -substituted ligand of Example 13.

Figure 22. ¹ H NMR spectrum of [L ¹ Mg] _n of Example 14 in CDCI ₃ . Figure 23. ¹ H NMR spectrum from the polymer obtained by the L ¹ ₂ Zn ₂ complex (at 1 bar) in Example 4.

Figure 24A. ¹ H NMR spectrum of [L ¹ Zn] ₂ (4), [L ¹ Mg] _n (3), [L ¹ Ni] _n (2) and [L ^x Zn] _n in CDCI ₃ , wherein L ^x is shown in Figure 24B and wherein L ¹ = (S)-3-(2-(hydroxydiphenylmethyl)pyrrolidin- 1 -yl)propan-1 -ol.

Figure 24B. H ₂ L ^X of Figure 24A.

Figure 25. ¹ H NMR spectrum of L ² of Example 8 in CDCI ₃ .

Figure 26. ¹ H NMR spectrum from the polymer obtained by the [L ¹ Co] _n complex (at 50 bar) in Example 6.

Detailed description _.

The present invention refers to the following embodiments: 1. Catalyst, in solid or dissolved state/form, having the formula L _X M _X , wherein

M is selected from the group consisting of Zn(ll), Cr(ll), Co(ll), Mn(ll), Fe(ll), Ni(ll), Cu(ll), Cr(lll), Co(lll), Mn(lll), Fe(l!l), Al(lll) and Mg(ll), and

L is according to the following formula I or II

wherein the substituents are defined as follows: Embodiment 1 : Ri , and R _a , / Rio, and Ri _0a :

each of R and each of R _1a /each of R ₁₀ and each of R1 _0a is independently selected from the group consisting of H, substituted or unsubstituted C4- ₁ 2 aryl, substituted or unsubstituted C _1-10 alkyl, halogen (in particular F, CI, Br, I), substituted or unsubstituted C _1-10 heteroalkyl, substituted or unsubstituted C ₃ . ₇ cycloalkyl, substituted or unsubstituted C ₃ . ₇ heterocycloalkyl, substituted or unsubstituted C _4-12 heteroaryl groups (e.g., furan, pyrrole, pyridine), CF ₃ , CN, SR ^k , S(0)R ^k , S(0) ₂ R ^k , OR ^k , SiR ^k R ^L R ^m , C(0)R ^k , C(0)OR ^k , C(0)N(R ^L )R ^k , OC(0)R ^k , OC(0)OR ^k , OC(0)N(R ^k )R ^L , NHR, and NH ₂ , N0 ₂ ;

In addition to the above definition in embodiment 1 , preferably at least one of and R _1a is a substituted or unsubstituted C ₄ . ₁₂ aryl (Embodiment R l).

In addition to the above definition in embodiment 1 , preferably at least one of Ri, and R _1a adjacent to the OH-group is a substituted or unsubstituted C ₄ . ₁₂ aryl (Embodiment R ll).

- In addition to the above definition in embodiment 1 , preferably at least one of R ₁₀ , and R _10a is a substituted or unsubstituted C ₄ .i ₂ aryl (Embodiment R ₁₀ -l).

- In addition to the above definition in embodiment 1 , preferably at least one of R ₁₀ , and R _10a adjacent to the OH-group is a substituted or unsubstituted C ₄ . ₁₂ aryl (Embodiment

- Preferably Ri, and Ri _a , / R ₁₀ , and R _1Ca are at least one substituted or unsubstituted C ₄ . ₁₂ aryl, and optionally one or more substituted or unsubstituted d.™ alkyl, preferably the substituents at the aryl and alkyl are selected from CN, N0 ₂ , NH ₂ , halogen, a silyl ether group, an acetylide group, MeO, halogenated C . ₁₀ alkyl such as CF ₃ , unsubstituted C ₄ . ₁₂ aryl, halogenated C . ₁₂ aryl, or C . ₁₂ aryl substituted with CF ₃ , CN, N0 ₂ , NH ₂ , halogen (Embodiment R _1/10 -i).

- Preferably at least one of Ri, and R _1a , / R ₀ , and R _10a is a substituted or unsubstituted C ₄ . ₁₂ aryl, and the remaining R^ and R _1a , / R ₁₀ , and R _10a are substituted or unsubstituted C _1-10 alkyl, wherein the substituents at the aryl and alkyl are selected from CN, NH ₂ , halogen, SiOMe, MeO, halogenated C _1-3 alkyl such as CF ₃ (Embodiment R _{1 10} -ll);

- Preferably all Ri, and R _1a , / R ₁₀ , and R _10a are substituted or unsubstituted C ₄ . ₁₂ aryl (Embodiment R _1/10 -lll).

- In addition to the above definition in embodiment 1 , preferably at least one of R-i, and R _1a , / R ₁₀ , and R _10a is a substituted or unsubstituted phenyl, in particular phenyl, optionally substituted in para and meta positions (Embodiment Ri _/10 -IV).

- In the context of the present invention, 'substituted' means: halogen, CF ₃ , CN, N0 ₂ , NH ₂ , Ci- ₅ alkyl, unsubstituted CM ₀ alkyl, halogenated CMQ alkyl, unsubstituted C ₄ -12 aryl, C ₄ -i ₂ aryl substituted with CF ₃ , CN, N0 ₂ , NH ₂ , halogen, OR ^k ;

- In the context of the present invention, 'substituted' preferably means: halogen, CF ₃ , CN,

N0 ₂ , NH ₂ , C _1-5 alkyl, unsubstituted C _1-10 aikyl, halogenated C _1-10 alkyl, phenyl, phenyl substituted with CF ₃ , CN, N0 ₂ , NH ₂ , halogen, COOH, OH, OR ^k ;

- In the context of the present invention, 'substituted' further preferred means: CF ₃ Embodiment 1 : R ₂ is selected from the group consisting of H, substituted and unsubstituted a Iky I and aryl, CF ₃ , CN, preferably R ₂ is H;

Embodiment 1 : R3, R _3a , R ₄ , R a. R5, Rs _a > Rei R6a R7. R7a _> R ₄ o. R ₄ oa ^: are independently selected from the group consisting of H, substituted or unsubstituted C ₄ . ₁₂ aryl, substituted or unsubstituted C _1-10 alkyl, halogen (in particular F, CI, Br, I), substituted or unsubstituted C _1-10 heteroalkyl, substituted or unsubstituted C ₃ . ₇ cycloalkyl, substituted or unsubstituted C ₃ . ₇ heterocycloalkyl, substituted or unsubstituted C ₄ , ₁₂ heteroaryl groups, CF ₃ , CN, C(0)NH ₂ , C(0)H, C(0)OH, SR ^k , S(0)R ^k , S(0) ₂ R ^k , SiR ^k R ^L R ^m , C(0)R ^k , C(0)OR ^k , C(0)N(R ^L )R ^k , OC(0)R ^k , OC(0)OR ^k , OC(0)N(R )R ^L , NHR, and NH ₂ ,

N0 ₂ ; and wherein R-substituents at adjacent C-atoms can together form one or two double, preferably one, bonds; - In addition to the above definition in embodiment 1 , preferably substituted or unsubstituted C -i ₂ aryl, and substituted or unsubstituted C,. ₁₀ alkyl, preferably the substituents at the aryl and alkyl are selected from CN, N0 ₂ , NH ₂ , halogen, COOH, OH, a silyl ether group, an acetylide group, MeO, halogenated C _-10 alkyl such as CF ₃ , unsubstituted C ₄ .i ₂ aryl, halogenated C ₄ . ₁₂ aryl, or C ₄ . ₁₂ aryl substituted with CF ₃ , CN, N0 ₂ , NH ₂ , halogen, COOH, OH (Embodiment R ₃ . _7/40 -l).

Embodiment 1 : R ₂₀ , R _2Ca , Rao^ are independently selected from the group consisting of H, substituted or unsubstituted C ₄ . ₁₂ aryl, substituted or unsubstituted C _1-10 alkyl, halogen (in particular F, CI, Br, I), substituted or unsubstituted C _1-10 heteroalkyl, substituted or unsubstituted C ₃ . ₇ cycloalkyl, substituted or unsubstituted C ₃ . ₇ heterocycloalkyl, substituted or unsubstituted C . ₁₂ heteroaryl groups, CF ₃ , CN, C(0)NH ₂ , C(0)H, C(0)OH, SR ^k , S(0)R ^k , S(0) ₂ R ^k , SiR ^k R ^L R ^m , C(0)R ^k , C(0)OR ^k , C(0)N(R ^L )R ^k , OC(0)R ^k , OC(0)OR ^k , OC(0)N(R ^k )R ^L , NHR, and NH ₂ ,

N0 ₂ ; and wherein R _20a and R ₃₀ together can represent a bond in order to provide a cis- conformation at the imine-moiety;

- In addition to the above definition in embodiment 1 , R ₂₀ , R _20a , R ₃₀ : are preferably substituted or unsubstituted C ₄ . ₁₂ aryl, and substituted or unsubstituted d. ₁₀ alkyl, preferably the substituents at the aryl and alkyl are selected from CN, N0 ₂ , NH ₂ , halogen,

COOH, OH, a silyl ether group, an acetylide group, MeO, halogenated Ci. ₁₀ alkyl such as CF ₃ , unsubsiituted C . ₁₂ aryl, halogenated C ₄ . ₁₂ aryl, or C ₄ . ₁₂ aryl substituted with CF ₃ , CN, N0 ₂ , NH ₂ , halogen, COOH, OH (Embodiment R ₂₀ /3o-l)-

Embodiment 1 : a, d is 0-2, preferably 0, wherein each pair of Ri/R ₁₀ , and R _1a /R _10a , can independently be selected from the groups as specified above, if a/d is 1 or 2.

Embodiment 1 : b is 0 or 1 , preferably 0.

Embodiment 1 : c, e is 0-2, preferably 2, wherein each pair of R ₇ /R ₄₀ , and R _a R4o _a , can independently be selected from the groups as specified above, if c/e is 1 or 2.

Embodiment 1 : X, in dissolved state/form, is 2-12, preferably 2-8, preferably 2 or 4.

Embodiment 1 : in all above groups, R, R ^k , R ^L , and R ^m are independently selected from the group consisting of H and optionally substituted C _1-4 alkyl, preferably CH ₃ ; C _-4 heteroalkyl, C ₃ . ₇ cycloalkyl, C ₃ . ₇ heterocycloalkyl, C ₄ . ₂ aryl, or C . ₁₂ heteroaryl groups, wherein two or more of R ^k , R ^L und R ^m may form, together with each other, one or more optionally substituted aliphatic or aromatic carbon cycles or heterocycles. - In addition to the above definition in embodiment 1 , R, R ^k , R ^L , and R ^m are independently selected from the group consisting of H and optionally substituted Ci _-4 alkyl, preferably CH ₃ (Embodiment R _k . _L .m-l)-

Herein, a, and d can be selected to be 0 or 1 , or 2. Furthermore, b can be selected to be 0 or 1. Further, c, and e can be selected to be 0 or 1 , or 2. In embodiments where one or more of a, b, c, d and e are different from 0, there is more than one pair of Ri, and R _1a , R ₁₀ , and R _10a , Re, and R _6a , R ₇ , and R _a , and/or R ₄₀ , and R _0a . Unless otherwise defined, it is understood that each pair of substituents at the same C-atom (e.g., R^ and R _1a ) as well as each substituent at the same C-atom (e.g., R, , and R _a ) of said pair can be independently selected as desired. In other words, if there are more than one Rrsubstituents in one compound, these R substituents can be the same or different.

One synthetic approach for preparing the claimed ligands it the use of Aza-Michael reactions, which are well-known in the art.

In solid state, the catalyst may be present in agglomerated form of LM/LxMx-complex moieties (as evidenced by the crystal structure of complex 1 ). 2. The catalyst according to embodiment 1 , wherein the substituents are as follows:

Formula I:

Ri , and R _{1 a} = Embodiment R l

R ₂ is selected from the group consisting of H, substituted and unsubstituted alkyl and aryl, CF ₃ , CN, preferably R ₂ is H;

R ₃ , R _3a , R ₄ , R _4a , Rs, Rsa, Re, R _6a , R?, R ₇ a= Embodiment R3.7/40-I

a is 0-2, preferably 0, wherein each pair of R _{1 T} and R _1A and each of Ri , and R _{1 a} in each pair, can independently be selected from the groups as specified above, if a is 1 or 2;

b is 0 or 1 , preferably 0;

c is 0-2, preferably 2, wherein each pair of R ₇ , and R _7a and each R ₇ , and R _7a in each pair, can independently be selected from the groups as specified above, if c is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R\ R ^l , and R ^m = Embodiment R _{k L} ,m-l; and wherein 'substituted' has the meaning as defined above.

In another embodiment, the substituents are as follows:

RL and R _{1 a} = Embodiment R ll

R ₂ is selected from the group consisting of H, substituted and unsubstituted alkyl and aryl, CF ₃ , CN, preferably R ₂ is H;

R ₃ , R _3a , R , R _4a , R ₅ , R _5a , Re, R _6a , R7, Embodiment R ₃ . _7/40 -l

a is 0-2, preferably 0, wherein each pair of R _{1 F} and R _{1 a} and each of R _{1 (} and R _{1 a} in each pair, can independently be selected from the groups as specified above, if a is 1 or 2;

b is 0 or 1 , preferably 0;

c is 0-2, preferably 2, wherein each pair of R ₇ , and R _7a and each R ₇ , and R _7a in each pair, can independently be selected from the groups as specified above, if c is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R ^k , R ^L , and R ^m = Embodiment R _{k L} ,m-l; and wherein 'substituted' has the meaning as defined above. In another embodiment, the substituents are as follows:

Ri , and R _{1 a} = Embodiment R1/10-I

R ₂ is selected from the group consisting of H, substituted and unsubstituted alkyl and aryl, CF ₃ , CN, preferably R ₂ is H;

R ₃ , R _3a , R ₄ , R _4a , Rs, sa, Re, R _6a , R ₇ , Embodiment R ₃ . _7/4 o-l

a is 0-2, preferably 0, wherein each pair of R^ and R _{1 A} and each of R _{1 ;} and R _{1 a} in each pair, can independently be selected from the groups as specified above, if a is 1 or 2; b is 0 or 1 , preferably 0;

c is 0-2, preferably 2, wherein each pair of R ₇ , and R _7a and each R ₇ , and R _7a in each pair, can independently be selected from the groups as specified above, if c is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R\ R ^l , and R ^m = Embodiment R _k . _L ,m-l; and wherein 'substituted' has the meaning as defined above.

In another embodiment, the substituents are as follows:

Ri , and R _{1 a} = Embodiment R ₁₀ -l I

R ₂ is selected from the group consisting of H, substituted and unsubstituted alkyl and aryl, CF ₃ , CN, preferably R ₂ is H;

R ₃ , R _3a , , a, R5, Rsa, Re, Re _a . R ₇ , Rja ^" Embodiment R _3-7/4 o-l

a is 0-2, preferably 0, wherein each pair of Ri , and R _{1 a} and each of Ri , and Ri _a in each pair, can independently be selected from the groups as specified above, if a is 1 or 2;

b is 0 or 1 , preferably 0;

c is 0-2, preferably 2, wherein each pair of R ₇ , and R _7a and each R ₇ , and R _7a in each pair, can independently be selected from the groups as specified above, if c is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R ^k , R ^L , and R ^m = Embodiment R _{k L m} -l; and wherein 'substituted' has the meaning as defined above.

In another embodiment, the substituents are as follows:

Ri , and R _{1 a} = Embodiment R1/10-NI

R ₂ is selected from the group consisting of H, substituted and unsubstituted alkyl and aryl, CF ₃ , CN, preferably R ₂ is H;

R ₃ , R _3a . 4, R4a, R ₅ , R _5a , Re, R _6a , R ₇ , R _7a = Embodiment R ₃ . _7M o-l

a is 0-2, preferably 0, wherein each pair of R-i , and R _{1 a} and each of Ri , and R _{1 a} in each pair, can independently be selected from the groups as specified above, if a is 1 or 2;

b is 0 or 1 , preferably 0;

c is 0-2, preferably 2, wherein each pair of R ₇ , and R _7a and each R ₇ , and R _7a in each pair, can independently be selected from the groups as specified above, if c is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R ^k , R ^L , and R ^m = Embodiment R _k,L,m -l; and wherein 'substituted' has the meaning as defined above. In another embodiment, the substituents are as follows:

Ri , and R _1a = Embodiment Ri _/10 -IV

R ₂ is selected from the group consisting of H, substituted and unsubstituted alkyl and aryl, CF ₃ , CN, preferably R ₂ is H;

R ₃ , R _3a , R ₄ , R _4a , R ₅ , R _5a , Re, Rea, R/, Embodiment R3.7/40-I

a is 0-2, preferably 0, wherein each pair of R^ and R _{1 a} and each of Ri , and R _{1 a} in each pair, can independently be selected from the groups as specified above, if a is 1 or 2;

b is 0 or 1 , preferably 0;

c is 0-2, preferably 2, wherein each pair of R ₇ , and R _7a and each R ₇ , and R _7a in each pair, can independently be selected from the groups as specified above, if c is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R\ R ^l , and R ^m = Embodiment R _k , _L , _m -l; and wherein 'substituted' has the meaning as defined above.

Formula II:

R ₁₀ , and R _10a = Embodiment R ₁₀ -i

R ₄ o, Embodiment R ₃ . _7M0 -I

R20, R2oa, R3o= Embodiment R20/30-I

d is 0-2, preferably 0, wherein each pair of R ₁₀ , and R _10a , can independently be selected from the groups as specified above, if d is 1 or 2;

e is 0-2, preferably 2, wherein each pair of R ₄₀ , and R _40a , can independently be selected from the groups as specified above, if e is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R ^k , R ^L , and R ^m = Embodiment Rki.m-I; and wherein 'substituted' has the meaning as defined above.

In another embodiment, the substituents are as follows:

R ₁₀ , and R _10a = Embodiment R ₁₀ -ll

R ₄₀ , Embodiment R ₃ . ₇ / ₄₀ -l

R20, 2oa, R30- Embodiment R20/30-I

d is 0-2, preferably 0, wherein each pair of R ₁₀ , and R _0a , can independently be selected from the groups as specified above, if d is 1 or 2;

e is 0-2, preferably 2, wherein each pair of R ₄₀ , and R _40a , can independently be selected from the groups as specified above, if e is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4; R, R ^K , R ^l , and R ^m - Embodiment R _k ,L,m-l; and wherein 'substituted' has the meaning as defined

In another embodiment, the substituents are as follows:

R ₁₀ , and R _10a = Embodiment R _{1 10} -l

R ₄₀ , R ₄ oa= Embodiment R3.7/40-I

R20, R2oa, R3o= Embodiment R20/30-I

d is 0-2, preferably 0, wherein each pair of R ₁₀ , and R _10a , can independently be selected from the groups as specified above, if d is 1 or 2;

e is 0-2, preferably 2, wherein each pair of R ₄₀ , and R _40a , can independently be selected from the groups as specified above, if e is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R ^k , R ^L , and R ^m = Embodiment R _k L m-l; and wherein 'substituted' has the meaning as defined above.

In another embodiment, the substituents are as follows:

R ₁₀ , and R _10a = Embodiment R _1/10 -ll

R ₄ o, Embodiment R3-7/40-I

R20, R20a _> R30- Embodiment R20/30-I

d is 0-2, preferably 0, wherein each pair of R ₁₀ , and R _10a , can independently be selected from the groups as specified above, if d is 1 or 2;

e is 0-2, preferably 2, wherein each pair of R ₄₀ , and R _0a , can independently be selected from the groups as specified above, if e is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R\ R ^L , and R ^m = Embodiment Rk,L m-l! and wherein 'substituted' has the meaning as defined above.

In another embodiment, the substituents are as follows:

R ₁₀ , and R _10a = Embodiment R _{1 10} -NI

R ₀ , R _0a = Embodiment R _3- 7/4o-l

R ₂₀ , R2oa, Embodiment R ₂₀ /3o-l

d is 0-2, preferably 0, wherein each pair of R ₁₀ , and R _10a , can independently be selected from the groups as specified above, if d is 1 or 2;

e is 0-2, preferably 2, wherein each pair of R ₄₀ , and R _0a , can independently be selected from the groups as specified above, if e is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4; R, R ^K , R ^L , and R ^m = Embodiment R _k , _L ,m-l; and wherein 'substituted' has the meaning as defined above.

In another embodiment, the substituents are as follows:

Rio, and Embodiment R _{1 10} -IV

R ₀ , R ₄₀ a= Embodiment R3-7/40-I

R20, R2oa, R ₃₀ = Embodiment R ₂₀ / ₃ o-l

d is 0-2, preferably 0, wherein each pair of R ₁₀ , and R _10a , can independently be selected from the groups as specified above, if d is 1 or 2;

e is 0-2, preferably 2, wherein each pair of R ₄₀ , and R _40a , can independently be selected from the groups as specified above, if e is 1 or 2; and

X is 2-12, preferably 2-8, preferably 2 or 4;

R, R ^k , R ^L , and R ^m = Embodiment Rk,L,m-l; and wherein 'substituted' has the meaning as defined above.

In the context of the present invention a 'catalyst' is a substance which is suitable for enhancing C0 ₂ /epoxide copolymerization under 1 bar of C0 ₂ pressure, at 80°C and with 0.05-1.00 mol% catalyst loading, wherein the result of the copolymerization is detected via NMR and wherein a successful copolymerization shows oligomeric and/or polymeric products.

In the catalysts described herein, R-substituents at adjacent C-atoms can together form double bonds. Double bond formation preferably occurs between R _3a , and R _4a ; R _5a , and R _6a ; R _20a and R ₃₀ . While it is contemplated that it is generally possible to have a conjugated ring system in the heterocyclic ring of formula I, this is less preferable due to a reduced stability of the resulting compound. Accordingly, it is preferred to have only one or two double bonds in Formula I, while the absence of double bonds is particularly preferred.

3. The catalyst according to any preceding embodiment, wherein L is according to the following formula l-a or ll-a.

4. The catalyst according to any preceding embodiment, wherein L is according to the following formula l-b:

I-b , wherein the substituents are defined as in the preceding embodiments.

5. The catalyst according to any preceding embodiment, wherein L is according to the following formula l-c:

I-c , wherein the substituents are defined as in the preceding embodiments, and wherein c is preferably 2.

6. The catalyst according to any preceding embodiment, wherein L is according to the following formula l-d:

I-d , wherein the substituents are defined as in the preceding embodiments.

7. The catalyst according to any preceding embodiment, wherein L is according to the following formula l-e:

I- ^e , wherein the substituents are defined as in the preceding embodiments, and where c is preferably 2.

8. The catalyst according to any preceding embodiment, wherein L is according to the following formula l-f and ll-b:

I-f H"b , wherein the substituents are defined as in the preceding embodiments, preferably, wherein at least one of R20 R40 contains an aliphatic chain such as substituted or unsubstituted CMO alkyl. 9. The catalyst according to any preceding embodiment, wherein L is according to the following formula l-g:

embodiments.

12. The catalyst according to any preceding embodiment, wherein L is according to the following formulas':

H ₂ L ¹ H ₂ L ² H ₂ L ³ H ₂ L ⁴ .

13. The catalyst according to any preceding embodiment, wherein M is selected from the group consisting of Zn(ll), Cr(ll), Co(ll), Mn(ll), Fe(ll), Ni(ll), Cu(ll), Cr(lll), Co(lll), Mn(lll), Fe(lll), Al(lll) and Mg(ll), preferably Ni(ll), Zn(ll), Co (II), and Al (III), Mg(ll), preferably Zn(ll), Co (II), and Mg(ll), particularly preferred Zn(ll).

14. The catalyst according to any preceding embodiment, which is a catalyst for polymerization/copolymerization of epoxides, in particular for copolymerization of C0 ₂ /epoxide.

15. Use of the catalyst of any preceding embodiment in polymerization reactions.

16. Use of the catalyst of any preceding embodiment for binding C0 ₂ .

17. The use of embodiment 16, wherein the polymerization reactions are selected from epoxide copolymerization/polymerization, in particular C0 ₂ /epoxide copolymerization, preferably applying cyclohexene oxide, oxirane, propylene oxide, limonene oxide, styrene oxide, cyclopentene oxide.

18. Process for polymerization of C0 ₂ /epoxide copolymerization, wherein the catalyst as defined in any of embodiments 1-14 is brought in contact C0 ₂ and epoxide.

19. The process of embodiment 18, wherein the C0 ₂ pressure is 0.8-100 bar, preferably 0.8-3 bar or 0.8-1.5 bar, preferably about 1 bar. 20. The process of embodiment 18 or 19, which is performed at a reaction temperature of above 50°C, preferably 80°C.

21. The process of any of embodiments 18-20, which produces an isotactic-enriched polycarbonate with a probability P _m of at least 50%, preferably at least 60%, further preferred at least 65 % for the formation of a meso diad as determined from the relative tetrade concentration by ¹³ C NMR spectroscopy of the carbonyle region (see Cohen, et al. Dalton Trans. 2006, 1, 237-249; Liu et al. Macromolecules 2015, 48, 6941-6947; Nozaki et al. J. Am. Chem. Soc. 1999, 121, 1 1008-1 1009; Nakano et al. Macromolecules 2001 , 34, 6325-6332). 22. Process for preparing the catalyst of any of embodiments 1 -14, by reacting H ₂ L with M(bis[bis(trimethylsilyl)amide]), M(NR ₂ ) ₂ , M(alkyl) ₂ , M(OAc) ₂ , M(OR) ₂ , M(X) ₂ + KH (NaOR or other bases, X=F, CI, Br, I), (depending on the oxidation state of the metal adapt the number of anions accordingly) or in general M(base) ₂ , or by reacting (lll) and a protonated ligand according to the following scheme:

+ base

H ₃ L + M ³⁺ [LM] _N ^N+

- 2 baseH ⁺

23. Catalyst obtainable or obtained by the process of embodiment 22.

Methods

General Experimental Procedures

Reactions that require water and oxygen free conditions were performed in Schlenk flasks that were heated while vacuum was applied and flushed with nitrogen using standard Schlenk techniques. The hydrophobic Schlenk vials were prepared by putting the hot glass ware 3 times times into an TMS-CI atmosphere (ca. 50 mbar). If not mentioned otherwise all chemicals were acquired from commercial sources (Acros, Sigma Aldrich, ABCR, Deutero, Merck) and used without further purification. Filtrations and extractions under inert conditions were performed with a glass microfiber filter Whatmann GF / B (25 mm). Solvents were transferred with Norm- Ject syringes, B. Braun cannulas and septa. The NMR spectra were measured on an Avance III 300, HD 400 or HD 500 spectrometer from Bruker. The chemical shifts are displayed as δ- values in units of ppm, using the residual protons of the deuterated solvent as internal standard (CD ₂ CI ₂ , δ 5.32 for ¹ H and 53.8 for ¹³ C; CDCI ₃ , δ 7.26 for ¹ H and 77.2 for ¹³ C). If not mentioned different CDCI ₃ was used as solvent. For the multiplicity of the signals the following abbreviations were used: s (singlet), d (doublet), t (triplet), q (quartet), quin (quintet), sex (sextet), sep (septet), m (multiplet). All spectra were measured at room temperature if not mentioned otherwise. For measuring the mass spectra, the following spectrometer were used: Applied Biosystems API 2000 (ESI), Finnigan MAT 8200 (El, 70 eV). The exact masses as well as isotopic distributions were calculated with CambridgeSoft ChemBioDraw 14. Elemental analyses were performed by the "Analytisches Labor" of the Institute of Inorganic Chemistry of the University of Gottingen. Samples that are sensitive to moisture were prepared in a N ₂ -glove box. The IR spectra were measured on an ATR Jasco FT/IR-4100, while the polymerizations were monitored in situ using a Mettler-Toledo ReactIR 10. DCM and cyclohexene oxide were dried over CaH ₂ , toluene and THF were dried over Sodium. The dry solvents were deoxygenated with nitrogen or argon and stored under it as well. Chemicals, if not mentioned otherwise were acquired from commercial sources (Acros, Sigma Aldrich, ABCR, Deutero, Merck) and used without further purification. Carbon dioxide (Airgas, 99.999% purity, with 120 bar of Helium) was dried over phosphorous pentoxide. X-ray diffraction experiments were performed on a STOE IPDS II diffractometer (graphite monochromated Mo-K _a radiation, λ = 0.71073 A, ω scans) at -140 °C. The refinement method was Full-matrix least-squares on F ² using all reflections with SHELXS-97 and SHELXL-97. ¹ ' ²

GPC analysis was performed on a GPC-SEC Analysis Systems 1260 Infinity.

Gas chromatography (GC) analyses were performed on a Trace GC Ultra equipped with a CP 9012 VF-5ms (30m) column.

Chiral GC analysis was performed on an Agilent Technologies 7890A equipped with a CP- Chirasil-Dex CB column. Examples

The following examples describe the present invention in detail, but they are not to be construed to be in any way limiting for the present invention. Example 1 : Synthesis of (S)-3-(2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)propan-1-ol (H ₂ L ¹ )

H ₂ L

(S)-diphenyl(pyrrolidin-2-yl)methanol (1 .00 g, 3.95 mmol, 1 eq.) and methyl acrylate (3.6 mL, 39.7 mmol, 10 eq.) were dissolved in 150 mL ethanol and heated to reflux for 3 h. All volatile substrates were removed under vacuum and the obtained methyl-(S)-3-(2- (hydroxydiphenylmethyl)pyrrolidin-1 -yl)propanoate (1.28 g, 3.95 mmol) was transferred into a Schlenk tube, dissolved in dry diethyl ether (30 mL) and cooled to 0 °C. Slowly 1.64 mL of a 2.4 M solution of LiAIH ₄ in THF were added under vigorous stirring. The reaction solution was allowed to warm to room temperature and left to stir for 3 h. 1 mL of water was added forming a colorless precipitate. All volatile substrates were removed under vacuum and the remaining solid was extracted with dichloromethane (60 mL, 30 mL, 20 mL). The dichloromethane suspensions were each treated with ultrasound for 5 min. before filtration. The dichloromethane was evaporated yielding the product (1.19 g, 97 %). Single crystals were obtained by slow evaporation of the DCM solution.

¹ H NMR (300 MHz, CDCI ₃ ): δ 7.67-7.12 (m, 10H, Ph), 4.45 (s, 1 H, OH), 3.84 (dd, J = 9.2, 4.1 Hz, 1 H, CH), 3.33 (m, 2H, CH ₂ OH), 3.26 (m, 1 H, CH ₂ N ^pyrrolidine ), 2.37 (m, 1 H, CH ₂ N ^pyrrolidine ), 2.24 (m, 1 H, CH ₂ N), 2.08 (m, 1 H, CH ₂ N), 1 .88 (m, 1 H, 3-CH ₂ ^pyrroiidine ), 1 .70 (m, 3H, 4- CH ₂ ^pyrrolidine , 3-CH ₂ ^pyrrolidin8 ), 1.48 (m, 2H, CH ₂ CH ₂ OH). ¹³ C NMR (75 MHz, CDCI ₃ ): δ 148.1 (Ph), 146.4 (Ph), 128.3 (Ph), 128.2 (Ph), 126.5 (Ph), 126.4 (Ph), 125.8 (Ph), 125.7 (Ph), 78.2 (CPh ₂ ), 71.7 (CH), 60.9 (CH ₂ OH), 55.6 (CH ₂ N ^pyrrolidine ), 53.9 (CH ₂ N), 31.6 (CH ₂ CH ₂ OH), 29.6 (3- CH ₂ ^pyrrolidine ), 24.7 (4-CH ₂ ^pyrrolidine ). (see Figure 3 and Figure 4). ESI-MS in MeOH m/z = 312.2 [M+Hf Example 2: Synthesis of zinc complexes with H ₂ L ¹ :

(S)-3-(2-(hydroxydiphenylmethyi)pyrroiidin-1 -yl)propan-1 -ol (178.2 mg, 0.572 mmol) was dissolved in 7 mL dry dichloromethane and 231 μΙ_ of Zinc bis[bis(trimethylsilyl)amide] were added. The solution was sired overnight. All volatile substrates were removed under vacuum, yielding the desired product (214.5 mg, quant.) as a colorless solid. Single crystals could be obtained from diffusion of pentane or diethyl ether into a dichloromethane solution. ¹³ C NMR (126 MHz, THF): δ 156.41 , 155.75, 154.76, 154.63, 154.39, 154.26, 154.15, 153.08, 152.26, 151 .89, 129.87, 129.13, 128.93, 128.82, 128.76, 128.51 , 128.00, 127.74, 127.57, 127.48, 127.39, 127.31 , 127.25, 126.94, 126.79, 126.48, 126.35, 126.21 , 126.07, 125.91 , 125.76, 125.71 , 125.44, 125.33, 80.69, 79.39, 77.86, 77.65, 76.76, 76.40, 76.30, 75.40, 74.89, 70.72, 69.22, 68.82, 68.39, 68.10, 63.07, 60.73, 60.52, 60.09, 59.1 1 , 58.78, 58.19, 57.48, 33.74, 33.10, 32.41 , 32.18, 31.1 1 , 30.79, 29.87, 29.48, 29.21 , 27.87, 26.56, 25.98, 23.71 , 23.20, 22.84, 21.63, 14.88, 14.21.

Anal. Calcd for C ₈₈ H ₁₀₈ N ₄ O ₁₀ Zn ₄ : C 64.32, H 6.62, N 3.41. Found: C 64.19, H 6.62, N 3.52. LIFDI-MS (Toluene): m/z = 747 [L ¹ ₂ Zn ₂ +H] ⁺ .

Complex 1 was characterized both in solution and in solid state. Single crystals were obtained by diffusion of diethylether into a DCM solution (space group P 4 _{3 \} 2,) or by diffusion of pentane into a DCM solution (space group P 2^). Molecular structures obtained by X-ray diffraction are displayed in Figure 2. Both crystalline forms of complex 1 were found to contain tetranuclear entities in which zinc ions are linked by alkoxido bridges: a chain of four zinc(ll) ions with bis(alkoxido) bridges between neighboring metal ions in (Figure 2, left) or a chain of three bis(alkoxido) bridged zinc ions with a forth zinc ion capping one edge in 1 " (Figure 2, right).

LIFDI mass spectrometry of a toluene solution of neutral 1 showed a major signal around m/z = 747 with an isotopic pattern characteristic for the ion [L ¹ ₂ Zn ₂ +Hf, suggesting the presence of dinuclear species in that solvent. The ¹ H NMR spectrum of 1 at rt is complex likely because of the presence of several isomers with different alkoxido bridging mode. Upon cooling to 239 K the ¹ H NMR signals sharpen. Analysis of ¹ H- ¹ H-COSY experiments as well as of the ¹³ C NMR spectrum in the 151.9-156.4 ppm range for THF-d ⁸ and the 153.3-148.6 ppm range for CDCI ₃ suggest the presence of five majorly-present coordination motives of the ligand L ^2~ . DFT calculations allowed an estimation of the most probable coordination motives and is supported by experimental evidence. DOSY NMR experiments of zinc catalyst 1 showed that ail species have approximately the same size, and the addition of Si(SiMe ₃ ) as internal standard allowed for an estimation of the molecular weight of the complex in solution (Stalke et al., Chem. Sci. 2015, 6, 3354-3364) giving M = 766 g/mol which corresponds well with the presence of dinuclear complex L ¹ ₂ Zn ₂ (M = 749.6 g/mol) (assuming ellipsoid shape of the complex). The combined experimental evidence indicates that at the temperatures of catalysis (≥50°C) the species in solution have the composition L ¹ ₂ Zn ₂ .

DFT calculations regarding catalyst 1 :

In the ¹³ C NMR spectra of the complex, five sets of signals for the quaternary carbons of the phenyl substituents were observed. To explain these signals as well as to be able to have further insight of the structure in solution DFT calculations were performed. After modeling the possible configuration of the complex and geometry optimization using the universal force field assumption (performed by Avogadro V.1 .1.1 ) the DFT calculation for the optimization was run with RKS BP86 def2-tzvp def2-tzvp/j Rl OPT as operation command (performed by Orca V.3.0.3). The configurations and the resulting single point energies (SP) can be found in Table S 1.

Table S 1 : Results of the DFT calculations on the configurations of [L ¹ Zn] ₂ (L ¹

(hydroxydiphenylmethyl)pyrrolidin-l -yl)propan-1 -olate) (catalyst 1 )

rel. Zn--N A SP*

Bridge conf. ^† N* Zn* transf SP ^§ / kcal/mol kcal/mol

1 RR -3465398 4.3

RR

2 SS 20-tans-RR-RS

3 RR 20-cis-SS-SS

CIS SS

4 SS -3465393 10 5 RR 20-trans-RS-RS

20 RS

6 SS 20-trans-RS-RS

7 RR RS -3465396 7.1 8 SS RS 20-cis-SS-SS

trans

9 RS -3465403 0.0

RS

10 SR 20-trans-RS-RS

11 RR 20Ph-cis-RR-SS

RR

12 SS -3465387 16 13 RR -3465383 20

cis SS

14 SS decoorination

20Ph

15 RR -3465379 24

RS

16 SS OOPh-cis-SR-SS

17 RR RS -3465388 15

trans

18 SS RS decoorination* 19 RS -3465395 7.5

20 _ RS 20Ph-cis-RS-SR

21 RR ^SS OOPh-trans-RR-RS

22 RR OOPMrans-RR-RS

23 _ss RR OOPMrans-SS-SR

24 _c/s ^ss -3465386 17

25 _RS SS 20-trans-RS-RS

26 RR -3465383 20

27 _SR SS -3465395 7.7

28 RR OOPh-trans-SR-SR

OOPn ————— ' ^■ ' ———— ^; — ^; —— '— ^■

29 _RR ^RS -3465401 2.0

30 SR -3465384 19

31 ^ decoorination ⁴

32 , R -3465386 17

trans ¹

33 _RS ^R S decoorination*

34 SR -3465387 16

35 _SR SR -3465383 20

36 RS oOPh-cis-SR-SS

*: moieties of the ligands that bridge two L ¹ Zn ₁ units. O referring to the propanolyl moiety and OPh to the diphenylmethanolyl moiety.†: relative positioning of the N atoms towards the Zn ₂ 0 ₂ plain between two units.†: configuration at the N or Zn atoms. In case of a OOPh bridge does the first initial indicate the configuration at the OPh bridging L ¹ iZni unit. The configuration SR-SR would mean that the S configured N atom is coordinated to a S configured Zn atom. The determination of the configuration at the metal was done by the following priority; 1 : OPh > O, 2: 0(within the L ¹ ₁ Zn ₁ ) > 0(neighbouring L ¹ ₁ Zn ₁ ). J: found configuration after DFT optimization. §: single point energy (SP) in kcal/mol. $: ASP =SP-SP ₂ o trans- RS- S in kcal/mol. φ: decoordination of a ligand moiety after DFT optimization.

The three configurations with the lowest calculated relative energies are 20-trans-RS-RS with ASP = 0 kcal/mol, OOPh-trans-RR-RS with ASP = 2.0 kcal/mol and 20-cis-RR-RR with ASP = 4.3 kcal/mol respectively. Within the crystal structures, due to a higher coordination number at the metals, the nomenclature of Table S 1 is not applicable. However, as far as it can be determined the configuration would correspond to OOPh-trans-RR and 20-cis-RR, which is the same ones as found from the DFT calculations. Further experimental evidence, that supports the computational results can be found in the ¹³ C NMR spectrum in the region of the quaternary carbons of the phenyl substituents (156-151 ppm). Here ten signals that correspond to five coordination environments can be observed and one of the sets has a lower abundance than the others. To form this pattern by dinuclear L ¹ ₂ Zn ₂ units two of them would have a d and one would have a C ₂ symmetry. Furthermore, the C ₂ symmetric unit would be expected to be higher in energy due to the lower abundance according to the ¹³ C NMR spectrum. Taking the configurations, obtained by the DFT calculation, under account allows to explain the found pattern of the ¹³ C NMR: OOPh-trans-RR-RS (d), 20-cis-RR-RR (d) and 20-trans-RS-RS (C ₂ , highes in energy)

Example 3: Polymerizations:

The catalyst 1 (20-29 mg) was transferred into a Schlenk flask equipped with a stirring bar and sealed with a septum inside of a glovebox. For selected reactions an in situ IR probe was inserted into the flask. Through the septum dried CHO (ca. 4 mL) was inserted and the catalyst was dissolved under stirring. After the atmosphere was filled with C0 ₂ (p _C02 = 1 bar), the reaction vial was inserted into a preheated oil bath (at the given experimental temperature) and time measurement was stared. After 1 , 3, 5, 8 and 24 h samples were taken from the reaction solution with a syringe. The mass of the sample was determined (CHO+cat.+PM) before removing the CHO under vacuum. The sample was dried to constant weight at 130 °C under vacuum (10 mbar).

Example 4: Catalytic activity

The catalytic activity of the complex 1 in C0 ₂ /CHO copolymerization was tested under 1 bar of C0 ₂ pressure, at 50°C and at 80°C and with 0.05-0.10 mol% catalyst loading (Table 1 ), using analytically pure crystalline material of 1. The chemoselectivity for the desired PCHC was found to be up to 99 %, according to H NMR measurement, and the highest TON and TOF values with respect to PCHC formation were 1684 and 149 h ^"1 , respectively. Interestingly, the TOF after 24 hours was found to be between 34 and 70 h ^"1 (Table 1 ), a value higher than the 18 h ^'1 of the benchmark zinc catalyst reported by Williams et al. in 2009, obtained for similar polymerization conditions. Furthermore, catalyst 1 differs from the so far known catalysts in that no additional ligands (such as acetate, HMDS or solvents) are coordinating in the precatalytic species. It was observed that splitting of the L ¹ ₄ Zn ₄ entities into two L ¹ ₂ Zn ₂ units occurs in solution, and that an external nucleophile or a temporary de-coordination and nucleophilic attack of a propanolate side arm may potentially initiate the polymerization. In Figure 5 the formation of PCHC is monitored over 24 h, showing an initiation phase for the catalyst of around 1 h, while the highest activity was observed between after around 3 h of catalysis. Using crystalline or bulk material of 1 resulted in similar activities, the same was observed when using ZnEt ₂ or Zn(HMDS) ₂ as metal source for the preparation of 1.

1 1008 24 >99 >98 1684 70 1 19 149

2 151 1 24 >99 >98 1461 61 72 104

3 2018 24 >99 >98 808 34 64 85

[a] Polymerizations were carried out in need CHO and 1 bar of C0 ₂ at 80 °C. All values in this table are average values from at least 2 runs. Reactions were performed in Schlenk tubes treated with TMS-CI. During all polymerizations samples were taken from the reaction solution after 1 , 3, 5 and 8 h and analysed. For entry 1 , reactions were equipped with a in situ-\R dip probe and monitored by IR spectroscopy, [b] % carbonate (carb.), % polycarbonate (p.c), determined by ¹ H NMR spectroscopy of the polymer in CDCI ₃ from the relative integrals of the signals at δ = 3.32 (homopolymer), 3.98 ppm (cyclic carbonate) and δ = 4.61 ppm (copolymer). [c] determined by molar number monomer units consumed divided by the molar number of catalysts, assuming an active L ¹ ₂ Zn ₂ unit, [d] TOF = TON / r, with f of the duration of the experiment, [e] TOFi. ₈ : the TOF observed between hour 1 and 8 of the reaction, [e] TOF _max : highest TOF observed between the samples after 3 h and 5 h. The polymer formed by 1 was found to have an average molecular weight of up to 2.7x10 ³ g/mol with PDIs in the range of 1.2-1.3 (see Table 2). To assess the effect of the catalyst on the secondary structure of the polymer, the probability of the formation of a racemo diad (P _r ) was calculated from a fit of the carbonyl region from quantitative ¹³ C NMR measurements (Coates et al. Dalton Trans. 2006, No. 1 , 237-249 and Lu et al., Macromolecules 2015, 48 (19), 6941- 6947), evidencing the formation of a polymer with enriched isotacticity (see Fig. S 19-24). However, chiral GC analysis of the hydrolyzed polymer did not show any enantiomeric excess within the diol. Apparently, the catalyst 1 does not distinguish between the two possible enantiomers of an isotactic polymer under the given polymerization conditions.

A Jordi Bures plot of the polymerization progress is displayed in Figure 6, suggesting that the catalysis is first order in L ¹ ₂ Zn ₂ (Bures, J. Angew. Chemie Int. Ed. 2016, 55 (6), 2028-2031). This implies that the catalytically active species is a dinuclear complex.

While performing the polymerization experiments it was observed that the catalytic activity is influenced by the presence of water (see Figure 7). Low concentrations of water (remains on the glass surface of the reaction vial) lead to a faster initiation but lower overall activity. During the propagation, the residual water could influence chain transfer reactions.

1 1008 24 2.72 1.28 36 %

2 151 1 24 2.44 1.22 36 %

3 2018 24 1.42 1.29 35 %

[a] see Table 1. [b] determined by GPC in THF with toluene as internal standard calibrated with polystyrene, [c] dispersity PDI = M _W IM _N . [d] probability of a racemo diad P _r determined from the relative tetrade concentration by quantitative ¹³ C NMR spectroscopy of the carbonyle region (see Coates et al. Dalton Trans. 2006, No. 1 , 237-249).

As a conclusion, the catalyst here presented is easily synthesized in extraordinarily high yields. The catalyst 1 is able to copolymerize C0 ₂ and epoxides forming an isotactic-enriched polymer chemoselectively. Moreover, it is able to do so with high activity even at 1 bar C0 ₂ . It could be determined that the most probable species in solution is an L ¹ ₂ Zn ₂ , thus demonstrating a new coordinative motive capable of the C0 ₂ /epoxide copolymerization.

An exemplary ¹ H NMR spectrum of the polymeric material in CDCI ₃ is shown in Figure 23.

Example 5: Applying Zn(OAc) ₂ as metal source for H ₂ L ¹ : conver

m(cat) V(CHO) p(C02) / t* / I I m (CHO m(PM) sion / 10? I

/ mg CHO/cat / mL bar h °C removed) / g / mg % TON h

14 1012 3 1 4 80 2.837 283 7 107 26.7

14 1012 3 1 8 80 2.080 541 13 204 25.5

Example 6: Preparation of L ¹ CoOAc

Activity of the in situ prepared cobalt catalyst. 30 mg of (S)-3-(2- (hydroxydiphenylmethyl)pyrrolidin-l -yl)propan-1 -ol (H ₂ L ¹ ) and 17 mg of Co(OAc) ₂ were dissolved in dry DCM. After stirring for 2 days the solvent was removed and the catalyst was applied for a copolymerization experiment of CHO and 50 bar of C0 ₂ , yielding 206 mg polymeric product from 2.4669 g of reaction solution. The obtained molecular structure of a cobalt complex in solid state is shown in Figure 15, which was synthesized using KH and CoBr ₂ . The catalyst showed a moderate activity when tested at 50 bar. The ¹ H NMR spectrum of the obtained polymeric product is depicted in Figure 26

Example 7: Preparation of L ¹ Ni

The obtained molecular structure of a nickel(ll) complex in solid state is shown in Figure 16. The synthesized was performed by using KH and NiBr ₂ (dme). The ¹ H NMR spectrum of dissolved crystalline material of L ₂ Ni ₂ in CDC! ₃ is shown in Figure 17A. ¹³ C NMR spectrum of dissolved crystalline material of L ₂ Ni ₂ in CDCI ₃ is shown in Figure 17B. The catalyst showed a low activity when tested at 50 bar as visible in Figure 24A (No. 2).

Example 8: Preparation of a further ligand H ₂ L ² Methyl-(S)-3-(2-(hydroxydiphenylmethyl)pyrrolidin-1 -yl)propanoate (557 mg, see synthesis of (S)-3-(2-(hydroxydiphenylmethyl)pyrrolidin-1 -yl)propan-1 -ol and Figure 18A) was heated to reflux for 2 h in a solution of NaOH (0.8 g) in 30 mL of ethanol and 5 mL of water. The solvents were removed under reduced pressure. 10 mL of water were added and the pH was set to 7 by the addition of a HCI solution. DCM was added and the aqueous solution t

1H NMR (300 MHz, Chloroform-d) δ 7.69 - 7.12 (m, 10H), 4.45 (t, J = 7.6 Hz, 1 H), 3.58 - 3.47 (m, 1 H), 2.90 (dq, J = 14.6, 7.8 Hz, 3H), 2.55 - 2.34 (m, 2H), 2.23 - 1.96 (m, 2H), 1.85 (tt, J = 13.4, 6.6 Hz, 2H). ¹³ C NMR (75 MHz, CDCI ₃ ) δ 175.14, 145.45, 144.76, 128.64, 128.47, 127.49, 127.1 1 , 126.00, 125.81 , 78.29, 74.28, 54.59, 53.55, 52.80, 32.21 , 28.62, 23.30. Example 9: Determining the activity of [L ² Zn] _n

The ligand H ₂ L ² was reacted with one equivalent of Zn(HMDS) ₂ in dry DCM. All volatile compounds were removed under vacuum and the complex tested for catalytic activity:

Activity at 1 bar of C0 ₂ : m(cat) V(CHO p(C02 t* / Ί 1 V(CHO) m(PM) conversi TOF /

/ mg CHO/cat ) / ml ) / bar h °C / mL / mg on / % TON h ^"1

19.9 1009 2.6 1 1 80 2.29 29 0.9 3 2.5

21 .3 1015 2.8 1 3 80 2.40 53 1.5 8 2.7

19 1016 2.5 1 5 80 2.23 73 2.3 16 3.1

19.8 1014 2.6 1 8 80 1.04 90 5.8 20 2.4 Example 10: In situ preparation of a zinc catalyst

The activity of the in situ prepared zinc catalyst (see scheme in Figure 18B, last step) was determined. 16 mg of 4-((S)-2-(hydroxydiphenylmethyl)pyrrolidin-1 -yl)butan-2-ol and 49 pL of Et ₂ Zn (1 M in hexane) were dissolved in dry THF. After stirring for 30 min. the solvent was removed and the catalyst was applied for a copolymerization experiment of CHO and 1 bar of C0 ₂ , yielding 46 mg polymeric product from 2.105 g of reaction solution. However, due to a high water content of the CHO (37 ppm) this experiment is not a meaningful representation of this catalysts activity.

1H NMR spectrum of the obtained ligand material in CDCI ₃ is shown in Figure 19. Example 11 : Preparation of a further ligand

The synthesis of A as shown in the scheme of Figure 20A was successful (see ¹ H NMR spectrum in CDCI ₃ No. 1 in Figure 20B), however, to isolate B (see ¹ H NMR spectrum in CDCI ₃ . No. 2 in Figure 20B) further purification steps are necessary. Nevertheless, an introduction of the phenyl groups was successful. Furthermore, the integral of the aromatic signals compared to the aliphatic one shows the desired ratio. Example 12: Possible further route for preparing ligands

A possible further synthesis approach is outlined in Figure 21A.

Example 13: Preparation of CF ₃ -substituted ligands H ₂ L ⁴

CF ₃ -substituted ligands (see Figure 21 B), can, e.g., be prepared by applying an equivalent synthetic route as for (S)-3-(2-(hydroxydiphenylmethyl)pyrrolidin-1 -yl)propan-1 -ol (reflux time of 48 h for a quantitative aza-Michael reaction).

(S)-3-(2-(bis(3,5-bis(trifluoromethyl)phenyl)(hydroxy)methyl )pyrrolidin-1 -yl)propan-1-ol (98.7 mg) and methyl acrylate (0.2 ml_) were dissolved in 15 mL ethanol and heated to reflux for 48 h. All volatile substrates were removed under vacuum and the obtained compund was transferred into a Schlenk tube, dissolved in dry diethyl ether (7 mL) and cooled to 0 °C. Slowly 0.08 mL of a 2.4 M solution of LiAIH ₄ in THF were added under vigorous stirring. The reaction solution was allowed to warm to room temperature and left to stir for 8 h. 1 mL of water was added forming a colorless precipitate. All volatile substrates were removed under vacuum and the remaining solid was extracted with dichloromethane (6 mL, 6 mL, 6 mL). The dichloromethane was evaporated yielding the product (0.1 12 g) ¹ H NMR (300 MHz, Chloroform-of) δ 8.1 1 (s, 2H), 8.00 (s, 2H), 7.75 (s, 2H), 5.36 (s, 1 H), 3.90 (dd, J = 8.7, 5.4 Hz, 1 H), 3.37 (t, J = 6.1 Hz, 2H), 3.26 (ddd, J = 9.9, 6.2, 4.0 Hz, 1 H), 2.50 (id, J = 9.0, 7.0 Hz, 1 H), 2.27 (dt, J = 12.1 , 6.0 Hz, 1 H), 2.02 (dt, J = 12.4, 7.9 Hz, 1 H), 1.92 - 1.81 (m, 1 H), 1.78 - 1.62 (m, 3H), 1.57 - 1.43 (m, 3H). ¹³ C NMR (75 MHz, CDCI ₃ ) δ 149.76, 147.85, 132.69, 132.61 , 132.25, 132.16, 131.81 , 131.72, 131.37, 131.28, 128.78, 126.1 1 , 125.90, 125.17, 125.17, 121.55, 121.31 , 121.25, 1 17.94, 77.58, 77.16, 76.74, 71.21 , 60.55, 55.07, 53.05, 31.14, 29.78, 24.21. Catalytic testing with applying zinc showed the formation of mainly poly(cyclohexene oxide). Example 14: Preparation of [L Mg] _n

The [L ¹ Mg] _n complex was prepared from a THF solution of the ligand and 1 eq. of MgBu ₂ (1 M solution in Hexane) was added. The solvent was removed and the complex was applied without further purification.

¹ H NMR spectrum of [L ¹ Mg] _n in CDCI ₃ is shown in Figure 22. The broad signals originate from different stereoisomers, as found for the zinc complex of Example 2. The catalyst showed a low or moderate activity

When applied for copolymerization of CHO with 50 bar of C0 ₂ the ¹ H NMR spectrum (in CDCI ₃ ) as shown in Figure 24A (No. 3) can be obtained. The spectrum from the polymer obtained by the L ¹ ₂ Zn ₂ complex (at 1 bar) is also shown in the figure 24A (No. 4).

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