Trivalent Titanium Salen Complex: Thermally Robust and Highly Active Catalyst for Copolymerization of CO₂ and Cyclohexene Oxide

Abstract

A trivalent titanium complex combining salen ligand (salen-H₂<i>N,N</i>-bis­(3,5-di-<i>tert</i>-butylsalicylidene)-1,2-benzenediamine) was synthesized as catalyst for copolymerization of CO₂ and cyclohexene (CHO). In combination with onium salt [PPN]­Cl, (Salen)­Ti­(III)Cl showed impressive activity and selectivity, yielding completely alternating copolymer without the formation of cyclohexene carbonate (CHC), with turnover frequency (TOF) of 557 h^–1 at 120 °C, which was more than 10 times higher than that of our previously reported (Salalen)­Ti­(IV)­Cl, and close to the Cr counterparts. In addition to the biocompatibility of Ti, thermally robust character resulting from the reducibility of trivalent Ti was industrially desirable