Chain Transfer to Solvent in Propene Polymerization with Ti Cp-phosphinimide Catalysts: Evidence for Chain Termination via Ti-C Bond Homolysis

Propene polymerization using Ti Cp-phosphinimide catalysts in toluene and related aromatic solvents leads to the formation of benzyl-terminated polymer chains. End-group analysis suggests that these are formed after a 2,1 insertion event; density functional theory (DFT) studies support a mechanism involving homolysis of a Ti-sec-alkyl bond. This reaction could enable the catalytic formation of chain-end functionalized polyolefins. More importantly, it demonstrates that Ti-C homolysis might limit activity but does not necessarily constitute an irreversible deactivation mechanism.