Heterodinuclear complexes featuring Zn(ii) and M = Al(iii), Ga(iii) or In(iii) for cyclohexene oxide and CO₂ copolymerisation

Abstract

A series of heterodinuclear zinc(ii)-Group 13 catalysts are synthesised by a sequential metalation procedure. They are active catalysts for the ring opening copolymerisation of cyclohexene oxide and CO2.

Recent Developments in Ring-Opening Copolymerization of Epoxides With CO2 and Cyclic Anhydrides for Biomedical Applications

“…Over the last decade, a series of heterodinuclear metallic catalysts have emerged with excellent catalytic performance due to the synergetic effect between metal centers. Detailed kinetic, mechanistic, and theoretical studies suggest a "chain shuttling" mechanism where the rate-limiting step is metalcarbonate attack on a coordinated epoxide; thus, shuttle and activation of monomers at different metal centers can improve catalyst performance (Trott et al, 2019;Deacy et al, 2020a). Moreover, these studies demonstrated that heterodinuclear metal complexes may have better thermodynamic stability than the homodinuclear analogs (Deacy et al, 2018;Trott et al, 2019).…”

“…Since the metals from Group 1 or 2 are highly Lewis acidic, considering this feature may enhance the coordination of epoxides, and it is possible to generate unstable metal-carbonate bonds to lead a faster catalytic rate. A series of heterodinuclear combinations, featuring Zn(II)/M (Deacy et al, 2018(Deacy et al, , 2020a, were chelated by the macrocyclic ligand (Figure 7). For ROCOP of CHO/CO 2 , the most active and selective catalyst feature was Mg(II)/Zn(II), while all other heterodinuclear combinations showed a weaker activity.…”

“…Compared with petroleum derivative monomers, bio-based monomers usually have more functional groups, and it is difficult to achieve highly selective polymerization through traditional polymerization methods (Stadler et al, 2019). For ring-opening copolymerization (ROCOP) of epoxide with CO 2 or cyclic anhydrides, many efficient metal-based catalysts have been developed to produce alternating polycarbonates or polyesters (Paul et al, 2015b;Longo et al, 2016;Xia and Zhao, 2018;Liang et al, 2021), including zinc (Deacy et al, 2018(Deacy et al, , 2020aDenk et al, 2020), cobalt (Li et al, 2017a;Ambrose et al, 2019), aluminum (Sanford et al, 2018), or nickel (Huang et al, 2017;Li et al, 2017a) complexes with different ligands. These organometallic catalysts exhibit excellent catalytic SCHEME 1 | Ring-opening copolymerization of epoxides with CO 2 and cyclic anhydrides and post-polymerization modification for biomedical applications.…”

Heterodinuclear catalysts Zn(ii)/M and Mg(ii)/M, where M = Na(i), Ca(ii) or Cd(ii), for phthalic anhydride/cyclohexene oxide ring opening copolymerisation

“…In fact, a similar observation was made for another series of heterodinuclear catalysis for carbon dioxide/CHO ROCOP where a macrocyclic ancillary ligand was coordinated with Zn(II)M, where M = Li(I), Na(I), K(I), Ca(II), Al(III), Ga(III) and In(III); all combinations were less active than the di-Zn(II) catalyst. 35,38 Thus, the Zn(II)Mg(II) combination is somewhat special amongst the set of metals in providing heterodinuclear synergy. To target this desirable combination, attempts were made to prepare Zn(II)Mg(II) complexes from the precursors (3) and (8).…”

“…17,27 Furthermore, metals from groups 1, 2 and 12 are attractive targets due to their lack of colour, low toxicity and low cost. [35][36][37][38] Dinuclear catalysts based on both Zn(II) and Mg(II) are well known in the ROCOP of CO 2 /epoxide, [39][40][41] but are much less explored for the ROCOP of anhydride/epoxide ( Fig. S1IV and V †).…”