Ti and Zr amino-tris(phenolate) catalysts for the synthesis of cyclic carbonates from CO2 and epoxides

Herein, we report the application of four amino-tris(phenolate)-based metal complexes incorporating Ti(IV) or Zr(IV) centres (2a-3b) as homogeneous catalysts for conversion CO2 and epoxides into cyclic carbonates. The were synthesised, characterised then evaluated in combination with tetrabutylammonium iodide, bromide chloride binary catalytic systems reaction 1,2-epoxyhexane epoxide substrate at 12 bar pressure 90 °C 2 h. comprising two (2a 2b) showed similar performance. One notable exception was system consisting titanium complex 2b, bearing an axial Cl-ligand, chloride, which displayed higher activity compared to other titanium-based systems. Even achieved 3a, isopropoxide ligand, reached turnover numbers (TONmetal) up 1920 This performance is comparable that state-of-the-art this reaction. 3a explored further by investigating its applicability a broad scope, achieving quantitative several carbonate products 18 selectivity towards ? 98% all studied terminal 80% examined cyclohexene-type epoxides.