Oxotungsten(IV)-acetylene complexes: Synthesis via intermetal oxygen atom transfer and nuclear magnetic resonance studies

Article abstract of DOI:10.1021/ic50218a056

The first synthesis of oxotungsten(IV)-acetylene complexes, OW(R¹C≡CR²)(S₂CNR₂) ₂, has been effected by controlled oxidation of W(CO)(R¹C≡CR²)(S₂CNR₂) ₂ with the dimeric oxygen atom transfer reagent Mo₂O₃[S₂P(OEt)₂]₄. These complexes, including the parent C₂H₂ derivative, are stable toward alkyne dissociation (cf. OMo(HC₂H)(S₂CNR₂)₂) and have been characterized by elemental analysis, infrared spectroscopy, and variable-temperature nuclear magnetic resonance techniques. Dynamic NMR studies support the premise that a single molecular process is responsible for coalescence of the acetylenic proton signals and the dithiocarbamate alkyl signals. Neither acetylene rotation nor rotation around the C-N bond of the dithiocarbamate ligands is adequate to account for the experimental observations. A rearrangement of the chelating ligands, perhaps via dissociation of the sulfur trans to oxygen to form a fluxional five-coordinate intermediate, is compatible with the data obtained for OW(C₂H₂)(S₂CNEt₂)₂, OW(C₂H₂)(S₂CNMe₂)₂, and OW(PhC₂H)(S₂CNMe₂)₂.