Water-soluble tungsten hydrides:: Synthesis, structures, and reactions of (C5H4CO2H)(CO)3WH and related complexes

The water-soluble metal hydride (C5H4CO2H(CO)(3)WH (1) was prepared and characterized. The crystal structure of this complex determined by X-ray diffraction shows it to be dimeric in the solid state, due to OH ... O hydrogen bonds between the CO2H groups, The pK(a) of the W-H proton was determined to be 5.8 (+/-0.2) in water. While the CO2H site of (C5H4CO2H)(CO)(3)WH is more acidic than the W-H proton in water, the order of thermodynamic acidity is inverted in organic solvents. Deprotonation of (C5H4CO2H)(CO)(3)WH with KH in THF, followed by counterion exchange, gives [(C5H4CO2H)(CO)(3)W]-NBu4+ (2) This anion is also dimeric through intermolecular hydrogen bonding of the CO2H groups, as shown by X-ray crystallography, The reaction of PMe3 or P(OMe)(3) with (C5H4CO2H)(CO)(3)WH gives substitution of a CO ligand and formation of [C5H4CO2H)(PR3)(CO)(2)WH (R = Me, OMe), Reaction of PTA (PTA = phosphatriazaadamantane) with (C5H5)(CO)(3)WH gives (C5H5)(PTA)-(CO)(2)WH. This complex exists as an equilibrating cia/trans mixture in solution, but was crystallized as the trans isomer, as shown by X-ray crystallography, Water solubility of (C5H5)(PTA)(CO)(2)WH was negligible. The water-soluble metal-metal-bonded bimetallic complexes [(C5H4CO2H)(CO)(3)W](2), [(C5H4CO2H)(PMe3)(CO)(2)W](2), and {(C5H4CO2H)[P(OMe)(3)]-(CO)(2)W}(2) were prepared by reaction of the metal hydrides with trityl radical (Ph3C.).