Yttrium and lanthanum amido-complexes with bis(pyrazol-1-yl)acetates in their coordination spheres were studied as the catalysts in ɛ-caprolactone and lactide ring-opening polymerisation. A high molecular mass poly(ɛ-caprolactone) (PCL) was obtained in almost quantitative yield under mild conditions. rac-Lactide polymerisations were less efficient and required quite harsh experimental conditions to obtain atactic PLA samples with moderate yields. The average chain-length of PCL was dependent upon the choice of the metal centre and the presence of substituents on the pyrazole rings of the ancillary ligand. The ground-state geometries of the complexes and the first stages of ɛ-caprolactone polymerisation were computationally modelled by means of DFT calculations.
‡Presented at the XXV. International Conference on Coordination and Bioinorganic Chemistry, Smolenice, Slovakia, 31 May–5 June 2015.
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