Alkyl initiated ring opening polymerization of lactide by indium complexes supported by NCN pincer ligands

Indium-alkyl NCN pincer complexes supported by amine and imine donors are active catalysts for the ring opening polymerization of lactide. The amine indium complexes are significantly more active for polymerization due to the decoordination of the amine donors at higher temperatures. Solid state structures of the imine and amine indium complexes indicate that the imine–indium bonds are stronger than the analogous amine–indium bonds. Higher molecular weight polymers that were not observable by MALDI-TOF were shown to be linear by comparing their intrinsic viscocities with those of known linear polymers. The alkyl indium complexes are more active than the analogous alkyl aluminum complexes but are prone to transesterification reactions.