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

A series of novel manganese(II)-substituted polyoxometalates, [(Mn(II)(H(2)O)(3))(2)(WO(2))(2)(BiW(9)O(33))(2)](10-) (1), [(Mn(II)(H(2)O))(3)(SbW(9)O(33))(2)](12-) (2), and [(Mn(II)(H(2)O)(3))(2)(Mn(II)(H(2)O)(2))(2)(TeW(9)O(33))(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.