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

Two new di-zinc aryl complexes, [LZn2Ph2] and [LZn2(C6F5)2], coordinated by a diphenol tetraamine macrocyclic ligand are prepared and fully characterized, including by single crystal X-ray diffraction experiments. The complexes' reactivities with monomers including carbon dioxide, cyclohexene oxide, phthalic anhydride, iso-propanol and phenol are 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 ε-caprolactone (TOF = 5280 h-1).