Aluminium salabza complexes for fixation of CO2 to organic carbonates

Abstract

A highly stable and easy to synthesize aluminium complex bearing a flexible N₂O₂-donor salabza ligand (N,N′-bis(salicylene)-2-aminobenzylamine) in combination with tetrabutylammonium bromide forms an active binary catalytic system for the cycloaddition of CO₂ to epoxides (TOFs 120–3434 h⁻¹) under mild conditions (10 bar, 80 °C) and low catalyst loadings (0.05–0.2 mol%). Kinetic experiments have shown that the cycloaddition of CO₂ to styrene oxide catalyzed by 1/TBAB is first order in 1, TBAB, CO₂ and epoxide. A reaction mechanism is proposed based on these observations. Fe(III) and Co(III) related complexes are less active catalysts for this reaction.