An Air‐Stable Molybdenum‐Based Precatalyst in Oxygen‐Atom Transfer Reactions

We report on the preparation and characterization of two new air‐stable mononuclear molybdenum(VI) complexes, termed Mo VI O 2 (OPNO) 2 ( 1 ) and Mo VI O 2 (SPNO) 2 ( 2 ). The potential of these complexes to act as functional mimics of molybdoenzymes from the DMSO reductase family was investigated. Initial catalytic studies suggest that 2 (but not 1 ) catalyzes the reduction of a sulfoxide into the thioether derivative. Studying the catalytic intermediates by UV/Vis spectroscopy, NMR spectroscopy, and DFT indicates that the active species (SPNO) 2 OMo V –O–Mo V O(SPNO) 2 ( 4 ), a dinuclear molybdenum(V) dimer with one µ‐oxo bridge, is formed upon successive reduction of the (SPNO) – ligands and the molybdenum(VI) ion.