Multinuclear NMR Studies and Reaction with tert-Butyl Isocyanide of Dinuclear Tungsten- or Molybdenum-Palladium μ-Alkylidene Complexes. X-ray Structure of [PdI{μ-C( p-tolyl)dmba}{μ-CO}Mo(Cp) (CN-t-Bu)2]

The lH,13C, and lg3W NMR characteristics for a series of dinuclear complexes containing a W-(p-CR1R2)-Pd moiety are reported. These compounds, derived from the reaction of the carbyne complex (Cp)(C0)2M(=CR), M = Mo, W, R = cyclopentenyl or p-tolyl, with a dinuclear cyclopalladated complex are shown to possess an y2-bond from the cyclopentenyl or p-tolyl fragment to the metal, thus attaining an 18-electron configuration at M. The bridging carbon has its 13C absorption at 6 = 142.4-155.1. Reaction of a Mo derivative with 2 equiv of t-BuNC displaces the y2-bond and affords a new complex, [PdI{p-C(p-tolyl)dmba){p-CO)Mo(Cp)(t-BuNC)~l, whose structure in the solid state was determined by X-ray diffraction. The solution NMR data for this complex clearly show that the $-bond is no longer present.