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.