Metallocene catalysts for the ring-opening co-polymerisation of epoxides and cyclic anhydrides

The ring-opening co-polymerisation (ROCOP) of epoxides and cyclic anhydrides is a versatile route to new polyesters. The vast number of monomers that are readily available means that an effectively limitless number of unique polymeric materials can be prepared using a common synthetic route, thereby paving the way to polymers that are more recyclable and could be used in applications that currently lie exclusively within the remit of polyolefins. Metallocene complexes [Cp₂MCl₂] (M = Ti, Zr, Hf, Cp = η⁵-C₅H₅) are known to be excellent pre-catalysts for olefin polymerisation and yet have not been reported for ROCOP, despite their supreme pedigree in the polymerisation realm. Herein, we report the first application of [Cp₂MCl₂] as catalysts for the ROCOP of epoxides and anhydrides and show that they are effective catalysts for this reaction. The catalytic performances are good with standard epoxides such as cyclohexene oxide but are excellent with more challenging sterically demanding limonene oxide, and this therefore represents a highly effective catalyst system for the preparation of bio-derived recyclable polymers.