Cobalt catalysts for the coupling of CO₂and epoxides to provide polycarbonates and cyclic carbonates

Abstract

This comprehensive tutorial review focuses on well-defined cobalt complexes that serve as homogeneous catalysts for the production of polycarbonates and cyclic carbonates from the coupling of carbon dioxide and epoxides. Special considerations are given to the mechanistic pathways involved in these processes.

Aliphatic-aromatic poly(ester-carbonate)s obtained from simple carbonate esters, α,ω-aliphatic diols and dimethyl terephthalate

“…BMC4 4 were placed. The reaction was carried out at 180-190°C for 8 h under atmospheric pressure with a nitrogen flow, until no methanol was observed in the distillate (the refractive index was measured).…”

“…The procedure was described by us earlier [10]. Ti(OBu) 4 (0.1 mol.%) was used as a catalyst. BMC means alkylene bis(methyl carbonate) and the number after signifies the length of hydrocarbon chain in the α,ω-diol, for example BMC4 means tetramethylene bis(methylcarbonate).…”

“…In a 1000 cm 3 three-neck round-bottomed flask equipped with a magnetic stirrer, thermometer, distilling condenser and nitrogen supply system, 22.96 g (0.2546 mol) of 1,4-butanediol, 37.33 g (0.1697 mol) of BMC4 and 0.09 g (0.2 mmol) of Ti(OBu) 4 were placed. The reaction was carried out at 165-180°C for 6 h under atmospheric pressure with a nitrogen flow, until no methanol was observed in the distillate (the refractive index was measured).…”

“…In a 250 cm 3 three-neck round-bottomed flask equipped with a magnetic stirrer, thermometer, DeanStark distilling trap, reflux condenser and nitrogen supply system, 78.75 g (0.8750 mol) of 1,4-butanediol, 38.28 g (0.3750 mol) of propylene carbonate and 0.09 g (0.25 mmol) of Ti(OBu) 4 were placed. The reaction was carried out for 6 h at 165-170°C under atmospheric pressure with continuously removal of 1,2-propylene glycol by co-distillation with n-heptane, until no 1,2-propylene glycol was observed in the distillate.…”

“…However, it has been difficult to find wide commercial application for polycarbonates obtained according to this process due to their low glass transition temperature and relatively poor mechanical properties. Recently, new catalysts such as cobalt complexes [4,5], zinc adipate [6,7] or a double metal cyanide complex [8] were investigated to improve the efficiency of copolymerization CO 2 with oxiranes. The main advantage of aliphatic polycarbonates similarly to aliphatic polyesters is theirs biodegradability.…”