Single-Site Homogeneous and Heterogeneized Gold(III) Hydrogenation Catalysts:Mechanistic Implications

摘要

Au(III)-Schiff base complexes are active hydrogenation catalysts,giving turnover frequencies similar to those of the corresponding complexes of Pd(II),which has the same d~8 electronic structure as Au(lll).The mechanism of the reaction has been studied in detail by a combination of kinetic experiments and theoretical calculations.It is predicted and tested that the nature of the solvent plays a critical role for the heterolytic cleavage of H_2 (controlling step).Taking this into account,and by properly selecting the nature of solid supports (polarity and proton-donating ability),it was possible to strongly increase the activity of the homogeneous Au(III) and Pd(II) catalysts by grafting them onto the surface.