Strained metal bonding environments in methylindium dithiolates and their reactivity as initiators for the ring-opening polymerization of cyclic esters

摘要: Abstract We have synthesized indium complexes containing a variety of metal bonding environments through use polyfunctional dithiolate ligands and examined their reactivity as initiators for the ring-opening polymerization l -lactide, rac-lactide, e-caprolactone β-butyrolactone. The facile reaction Me3In with corresponding dithiols in toluene, thf or diethyl ether resulted formation [MeIn(SOOS)]2 (3), MeIn(SNNS) (4), [MeIn(ONS2)]3 (5), MeIn(NNS2) (6), MeIn(NNS2Pr) (7) MeIn(pyrS)2 (8). solid-state structures 3 5 each show ligand to be tridentate an uncoordinated O atom. Dimeric (3) trimeric (5) result from short intermolecular In … S interactions. All five coordinate centres distorted trigonal bipyramidal environments, but various arrangements donor atoms (eq/ax): SSC/OS (3,5), SNC/NS SSN/NC SSC/NS SSC/NN DFT studies model MeIn(SMe)2(NH3)2 systems 4 6 highly strained, while axial In–Me bond shows longest distance lowest vibrational frequency. Compound provided best control -lactide rac-lactide THF at 70 °C, small heterotactic enrichment was observed latter. Compounds β-BL toluene 70 °C compound e-CL 70 °C. all cases, rates were low. This work demonstrates systematic approach exploring modification main group motifs, which has identification two novel “strained” indium.