New Titanium Catalysts Containing Tetrazole for Cycloaddition of CO2 to Epoxides

Abstract

A series of new half-sandwich titanocene [(eta(5)-C5H5)TiLCl2] (1) and nonorganometallic titanium complexes [TiLCl3(THF)] (2) and [TiL2Cl2] (3) containing 5-(2-hydroxyphenyl)tetrazole (LH) were synthesized in high yield and fully characterized by various spectroscopic methods and X-ray crystallography. In all complexes, the ligand L acted as a monoanionic bidentate ligand and hydrogen bonding between the oxygen of the tetrahydrofuran and hydrogen of the tetrazolyl unit was observed. In the cydoaddition of CO2 to propylene oxide, complex 3 showed the highest activity among the reported Ti complexes.