Zwitterionic Complexes of Group 4 Metal Chlorides Containing a Bis(imino)phenoxide Scaffold: Synthesis, Characterization and Polymerization Studies

• Published in: ChemistrySelect (Weinheim) 2016-10, Vol.1 (16), p.5218-5229
• Main Authors: Chakraborty, Debashis, Chokkapu, Eswara Rao, Mandal, Mrinmay, Gowda, Ravikumar R., Ramkumar, Venkatachalam
• Format: Article
• Language: English
• Subjects: Group 4; polyesters; polyethers; ROP; zwitterionic complexes
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.201600909

Chlorides of group 4 metals containing the bis(imino)phenoxide ligand scaffold were synthesized from a direct reaction between the respective ligand and metal chlorides MCl4 (M=Ti, Zr and Hf). These complexes were thoroughly characterized using various spectroscopic methods and single crystal X‐ray diffraction studies. They are potent catalysts for the polymerization of rac‐lactide (rac‐LA), L‐lactide (L–LA), ϵ‐caprolactone (ϵ‐CL), epoxides such as, rac‐cyclohexene oxide (rac‐CHO), rac‐propylene oxide (rac‐PO), rac‐styrene oxide (rac‐SO) and ethylene, resulting in polymers with high number average molecular weights (Mn) and narrow molecular weight distributions (MWDs). The kinetic and mechanistic studies associated with the polymerization of lactide, ϵ‐CL and CHO has been investigated in details. Zwitterionic complexes of group 4 metals containing the bis(imino) phenoxide ligand scaffold were synthesized and their activity towards the ROP of lactide, ϵ‐CL, ethylene and homopolymerization of epoxides were investigated.