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.以甲苯及相关芳香族溶剂为反应介质，使用钛-环戊二烯基膦亚胺催化剂（Ti Cp-phosphinimide catalysts）进行丙烯聚合时，会生成苄基封端的聚合物链。端基分析表明，此类聚合物链是经2,1-插入反应形成的；密度泛函理论（DFT）研究证实了其反应机理涉及钛-仲烷基键的均裂。该反应可实现链端功能化聚烯烃的催化合成。更为关键的是，该研究表明钛-碳键均裂可能会降低催化活性，但未必会造成不可逆的催化剂失活。