Water-Soluble Tungsten Hydrides: Synthesis, Structures, and Reactions of (C5H4CO2H)(CO)3WH and Related Complexes

The water-soluble metal hydride (C 5 H 4 CO 2 H)(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 CO 2 H groups. The p K a of the W−H proton was determined to be 5.8 (±0.2) in water. While the CO 2 H site of (C 5 H 4 CO 2 H)(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 (C 5 H 4 CO 2 H)(CO) 3 WH with KH in THF, followed by counterion exchange, gives [(C 5 H 4 CO 2 H)(CO) 3 W] - NBu 4 + ( 2 ). This anion is also dimeric through intermolecular hydrogen bonding of the CO 2 H groups, as shown by X-ray crystallography. The reaction of PMe 3 or P(OMe) 3 with (C 5 H 4 CO 2 H)(CO) 3 WH gives substitution of a CO ligand and formation of (C 5 H 4 CO 2 H)(PR 3 )(CO) 2 WH (R = Me, OMe). Reaction of PTA (PTA = phosphatriazaadamantane) with (C 5 H 5 )(CO) 3 WH gives (C 5 H 5 )(PTA)(CO) 2 WH. This complex exists as an equilibrating cis/trans mixture in solution, but was crystallized as the trans isomer, as shown by X-ray crystallography. Water solubility of (C 5 H 5 )(PTA)(CO) 2 WH was negligible. The water-soluble metal−metal-bonded bimetallic complexes [(C 5 H 4 CO 2 H)(CO) 3 W] 2, [(C 5 H 4 CO 2 H)(PMe 3 )(CO) 2 W] 2, and {(C 5 H 4 CO 2 H)[P(OMe) 3 ](CO) 2 W} 2 were prepared by reaction of the metal hydrides with trityl radical (Ph 3 C • ).