Di-Zinc-Aryl Complexes: CO2 Insertions and Applications in Polymerisation Catalysis

Two new di-zinc-aryl complexes, [LZn2Ph2] and [LZn2(C6F5)(2)], coordinated by a diphenol tetraamine macrocyclic ligand have been prepared and fully characterised, including by single-crystal X-ray diffraction experiments. The complexes' reactivities with monomers including carbon dioxide, cyclohexene oxide, phthalic anhydride, isopropanol and phenol were investigated using both experimental studies and density functional theory calculations. In particular, [LZn2Ph2] readily inserts carbon dioxide to form a carboxylate, at 1 bar pressure, whereas [LZn2(C6F5)(2)] does not react. Under these conditions [LZn2Ph2] shows moderate activity in the ring-opening copolymerisation of cyclohexene oxide/ carbon dioxide (TOF= 20 h(-1)), cyclohexene oxide/phthalic anhydride (TOF= 33 h(-1)) and the ring-opening polymerisations of rac-lactide (TOF= 99 h(-1)) and e-caprolactone (TOF= 5280 h (-1)).