Synthesis and catalytic epoxidation activity with TBHP and H \u3c inf\u3e 2 O \u3c inf\u3e 2 of dioxo-, oxoperoxo-, and oxodiperoxo molybdenum(VI) and tungsten(VI) compounds containing monodentate or bidentate phosphine oxide ligands: Crystal structures of WCl \u3c inf\u3e 2 (O) \u3c inf\u3e 2 (OPMePh \u3c inf\u3e 2 ) \u3c inf\u3e 2 , WCl \u3c inf\u3e 2 (O)(O \u3c inf\u3e 2 )(OPMePh \u3c inf\u3e 2 ) \u3c inf\u3e 2 , MoCl \u3c inf\u3e 2

The dioxo tungsten(VI) and molybdenum(VI) complexes WCl2(O) 2(OPMePh2)2, WCl2(O) 2dppmO2, and MoCl2(O)2-dppmO 2, the oxoperoxo compounds WCl2(O)(O2) (OPMePh2)2, WCl2(O)(O2)dppmO 2, and MoCl2(O)(O2)dppmO2, and the oxodiperoxo complexes, W(O)(O2)2dppmO2 and Mo(O)(O2)2dppmO2 have been prepared and characterized by IR spectroscopy, 31P NMR spectroscopy, elemental analysis, and X-ray crystallography. The structural and X-ray crystallographic data of compounds WCl2(O)2(OPMePh2) 2, WCl2(O)(O2)(OPMePh2)2, MoCl2(O)2dppmO2·C4H 10O, WCl2(O)2dppmO2, Mo(O)(O 2)2dppmO2, and W(O)(O2) 2dppmO2 are also detailed. All complexes were studied as catalysts for cis-cyclooctene epoxidation in the presence of tert-butyl hydroperoxide (TBHP) or H2O2 as an oxidant. The Mo-based catalysts showed a superior reactivity over W-based catalysts in the TBHP system. On the other hand, in the H2O2 system, the W-based catalysts (accomplishing nearly 100% epoxidation of cyclooctene in 6 h) are more reactive than the Mo catalysts ( \u3c 45% under some conditions). Various solvent systems have been investigated, and ethanol is the most suitable solvent for the H2O2 system. © 2006 American Chemical Society