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.