Hydride, gold(I) and related derivatives of the unsaturated ditungsten anion [W2Cp2(μ-PCy2)-(μ-CO)2]-

Protonation of the title anion with [NH4]PF6 gave [W2Cp2(H)(mu-PCy2)(CO)(2)] (2), which in solution exists as an equilibrium mixture of two isomers having either bridging (major) or terminal (minor) hydrides. Both molecules retain short intermetallic distances (ca. 2.54 angstrom), with the H-bridged isomer being almost 15 kJ mol(-1) more stable than the terminal one, according to density functional theory calculations. Further protonation with acids having weakly coordinating anions (BF4- or BAr'(-)(4); Ar' = 3,5-C6H3(CF3)(2)) yielded isomeric cations also displaying bridging and terminal hydride ligands ([W2Cp2(mu-H)(H)(mu-PCy2)(CO)(2)](+) and [W2CP2(H)(2)(mu-PCy2)(CO)(2)](+)), with the latter being only slightly more energetic (by ca. 4 kJ mol(-1)). In contrast, protonation of 2 with carboxylic acids yielded carboxylate-bridged derivatives [W2Cp2(mu-PCy2)(mu-O:O'-O2CR)(CO)(2)] [R = Ph, CF3] following from dihydrogen elimination. The title anion also reacted readily with metal-based electrophiles such as ClSnPh3 and [AuCl(PR3)] (R = Pr-I, p-tol) to give the corresponding heterometallic clusters [W2Cp2(mu-PCy2)(mu-SnPh3)(CO)(2)] and [AuW2Cp2(mu-PCy2)(CO)(2)(PR3)], these having the added electrophile placed at the bridging position and formally retaining triple W-W bonds. The gold complexes, however, were rather unstable species decomposing spontaneously to give the tetranuclear clusters [Au2W2CP2(mu-PCy2)(CO)(2)(PR3)(2)]X (W-W = 2.5803(6) angstrom and Au-Au = 2.8050(6) angstrom when R = Pr-I and X = PF6), which could be prepared more conveniently by adding two equivalents of [AuCl(PR3)] to the anion, as expected. In contrast, reaction of the title anion with ClPbPh3 led to the formation of the phenyl-bridged complex [W2Cp2(mu-PCy2)(mu-Ph)(CO)(2)], following from the formal loss of PbPh2.