Alcohol complexes of tungsten prepared by ionic hydrogenations of ketones

Ionic hydrogenation of acetone by Cp(CO)(3)WH and HOTf (OTf = OSO2CF3) give s the 2-propanol complex [Cp(CO)(3)W((HOPr)-Pr-i)]+OTf-. H-1 NMR data sugge st O-H . . .O hydrogen bonding between the alcohol OH and an oxygen of the triflate anion in solution, and a crystal structure of this complex shows t hat hydrogen bonding also exists in the solid state. The short O . . .O dis tance of 2.63(1) Angstrom indicates a strong hydrogen bond. Hydrogenation o f other ketones and aldehydes gives related [Cp(CO)(3)W(alcohol)] +OTf- com plexes; Aldehydes are selectively hydrogenated over ketones, and alkyl keto nes are selectively hydrogenated over aromatic ketones. Hydrogenation of ac etophenone gives ethylbenzene, with no intermediate tungsten complexes bein g observed. Reaction of 1-phenyl-1,3-butanedione with Cp(CO)(3)WH and HOTf gave {Cp(CO)(3)W[CH3CH(OH)CH2C(=O)Ph]}+OTf-, the structure of which was det ermined by X-ray diffraction. The alcohol complexes [Cp(CO)(3)W(alcohol)]+O Tf- decompose in solution to give free alcohols and Cp(CO)(3)WOTf. The cati onic dihydride [Cp(CO)(2)(PMe3)W(H)(2)]+OTf- hydrogenates aldehydes and ket ones; in these reactions a metal hydride serves as both the proton and hydr ide donor.