Protonation of tricarbonylbis(tricyclohexylphosphine)tungsten

Protonation of W(CO){sub 3}(PCy{sub 3}){sub 2} with equimolar HBF{sub 4}{center dot}OEt{sub 2} in toluene produces WH(BF{sub 4})(CO){sub 3}(PCy{sub 3}){sub 2}. This was characterized by spectroscopic methods and single-crystal x-ray diffraction as a seven-coordinate molecule with {eta}{sup 1}-coordinated BF{sub 4}{sup {minus}}. The location of the hydride, in the WFP{sub 2}CO plane and in the cis position relative to one P and CO, makes the phosphines inequivalent. This inequivalence is evident in both the {sup 31}P and {sup 1}H NMR spectra, but the onset of hydride fluxionality is detected already at 25{degree}C. The low-temperature {sup 19}F NMR spectrum and also the comparison of the spectral data of this molecule to that of the analogous products from HO{sub 3}SCF{sub 3}, H{sub 2}C(SO{sub 2}CF{sub 3}){sub 2}, and HCl{center dot}Et{sub 2}O indicate that the conjugate base of the acid employed for protonation remains coordinated in aromatic solvents. Reactivity studies of W(CO){sub 3}P{sub 2} with BF{sub 4}{sup {minus}} are consistent with the idea that the overall protonation reaction of 16-electron W(CO){sub 3}(PCy{sub 3}){sub 2} is initiated by proton transfer, not by coordination of a lone pair of the conjugate base (e.g., BF{sub 4}{sup {minus}} or OEt{sub 2}). 15 refs., 4 figs., 3 tabs.