New (old) hydroxo complexes of platinum(II) as catalysts for the Baeyer-Villiger oxidation of ketones with hydrogen peroxide

Enantioselective Baeyer-Villiger oxidation of cyclic ketones with hydrogen peroxide can be obtained using (P-P*)Pt(2-van) complexes (P-P*, chiral diphosphine; 2-van, bis-anion of 2-vanillin) as catalyst precursors. An analysis of the activation procedure aimed to the identification of the reactive species leads to the isolation of complexes of the type [(P-P)Pt(mu-OH)](2)(2+) (P-P, various diphosphines). The synthesis of some new species is reported together with their characterization with IR and NMR spectroscopy and conductivity data. It is found that these complexes are catalytically active in the (enantioselective) Baeyer-Villiger oxidation of cyclic ketones with hydrogen peroxide. The basic nature of the OH ligands is exploited in the reaction with a variety of acids including hydrogen peroxide.