Chemical and electrochemical oxidation of diphenylphosphide-bridged hydrides [M2 (η5-C5H5)2(μ-H)(μ-PPh2)(CO)4] and anions [M2(η5-C5H5)2(μ-PPh2)(CO)4]- (M = mo, w)

Reaction of the hydride complexes [M2Cp2(mu-H)(mu-PPh2)(CO)(4)] (M = Mo, W; Cp = eta(5)-C5H5) with [FeCp2]BF4 proceeds in a 1:2 ratio to give the unsaturated tetracarbonyl salts [M2Cp2(mu-PPh2)(CO)(4)]BF4, which spontaneously (M = Mo) or in the presence of CO (M = W) transform into the corresponding electron-precise pentacarbonyls [M2Cp2(mu-PPh2)(mu-CO)-(CO)(4)]BF4. In contrast, reaction of the above hydride complexes with [FeCp2](BAr'(4)) (Ar' = 3,5-C6H3(CF3)(2)) proceeds in a 1:1 ratio to give the paramagnetic salts [M2Cp2(mu-H)(mu-PPh2)(CO)(4)](BAr'(4)). No further reaction takes place with [FeCp2](BAr'(4)) unless a proton acceptor such as water or tetrahydrofuran is present, in which case the corresponding salts [M2Cp2(mu-PPh2)(CO)(4)](BAr'(4)) or [M(2)CPp(2)(mu-PPh2)(mu-CO)(CO)(4)](BAr'(4)) are rapidly formed. Reactions of the anions [M2Cp2(mu-PPh2)(CO)(4)](-) (as (H-DBU)(+) salts, DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) with [FeCp2]BF4 proceed stepwise to give first the 33-electron radicals [M2Cp2(mu-PPh2)(CO)(4)], which can be isolated as very air-sensitive green solids, and then the unsaturated salts [M2Cp2(mu-PPh2)(CO)(4)]BF4, which are identical to those formed from the neutral hydrides. The structure and dynamic behavior of the new compounds are analyzed on the basis of solution IR, H-1, P-31, and C-13 NMR or ESR spectroscopic data. In addition, the redox and other chemical transformations connecting all the new compounds are discussed on the basis of the synthetic and structural data, as well as cyclic voltammetry measurements carried out in dichloromethane on the neutral hydrides [M2Cp2(mu-H)(mu-PPh2)(CO)(4)] and the anions [M2Cp2(mu-PPh2)(CO)(4)](-) (as [N(PPh3)(2)](+) salts).