Electrophilic addition vs electron transfer for the interaction of Ag+ with molybdenum(II) hydrides. 1. Reaction with CpMoH(PMe3)(3) and the mechanism of decomposition of [CpMoH(PMe3)(3)](+)

The compound CpMoH(PMe3)(3), 1, is oxidized by Ag+ in acetonitrile to the 1 7-electron complex [CpMoH(PMe3)(3)](+), [1](+), which is indefinitely stabl e at low temperature. The oxidation takes place without the observation of a silver adduct intermediate. Complex [1](+) has also been generated by fer rocenium oxidation or by anodic oxidation and characterized by EPR spectros copy. Complex [1](+) slowly decomposes at room temperature by a second-orde r rate law (v = k(disp)[1(+)](2)), consistent with a disproportionation mec hanism. In the presence of unoxidized I, on the other hand, the decompositi on of [1](+) is faster and proceeds via a deprotonation mechanism (v = k(de prot)[1(+)][1]) with compound 1 acting as a catalyst. The ratio of the two second-order rate constants is K-deprot/K-disp = 5.8(7)). Intermediates of the disproportionation pathway, the solvent-stabilized double-oxidation pro ducts [CpMoH(S)(PMe3)(3)](2+) (S = THF, MeCN), have been isolated as stable salts with the PF6- and BF4- counterions, respectively. The acetonitrile a dduct has also been characterized by X-ray crystallography. The complex [Cp MoH(MeCN)(PMe3)(3)](2+) slowly transfers a proton to complex 1 to afford a 1:1 mixture of [CpMo(PMe3)(3)(MeCN)](+) and [CpMo(PMe3)(3)H-2](+) and is al so slowly deprotonated by NEt3.