Highly Efficient Catalysts in Directed Oxygen-Transfer Processes:  Synthesis, Structures of Novel Manganese-Containing Heteropolyanions, and Applications in Regioselective Epoxidation of Dienes with Hydrogen Peroxide

Abstract

A series of novel manganese(II)-substituted polyoxometalates, [(MnII(H2O)3)2(WO2)2(BiW9O33)2]10- (1), [(MnII(H2O))3(SbW9O33)2]12- (2), and [(MnII(H2O)3)2(MnII(H2O)2)2(TeW9O33)2]8- (3), were synthesized and characterized by X-ray structure analyses. The use of these oxidatively and solvolytically stable heteropolyanions as homogeneous catalysts for the epoxidation of dienes was investigated by gas chromatography/mass spectrometry, IR spectroscopy, UV−visible studies, and cyclic voltammetric measurements. The catalytic performance is exemplified by the model substrate (R)-(+)-limonene, at ambient temperatures in a biphasic system, with excellent regioselectivities, >99%, and very high turnovers even with only a small molar excess of hydrogen peroxide.