Protonation Reactions on the Binuclear Complexes [W₂Cp₂(CO)_n(μ-L₂)] [L₂ = Ph₂PCH₂PPh₂, Me₂PCH₂PMe₂; n = 2, 4]. Chemical Behavior of Their Hydrido and Hydroxycarbyne Derivatives

Reaction of the triply bonded dimers [W₂Cp₂(CO)₂(μ-L₂)] (L₂ = Ph₂PCH₂PPh₂, Me₂PCH₂PMe₂) with HBF₄·OEt₂ and other strong acids leads to the unsaturated cationic hydrides [W₂Cp₂(μ-H)(CO)₂(μ-L₂)]⁺. In contrast with this, reaction of HBF₄·OEt₂ with the singly bonded dimers [W₂Cp₂(CO)₄(μ-L₂)] leads, depending on L₂ and reaction conditions, to either hydroxycarbyne cations [W₂(μ-COH)Cp₂(CO)₂(μ-L₂)]⁺ or hydridoderivatives [W₂Cp₂(μ-H)(CO)_n(μ-L₂)]⁺ (n = 2 or 4). The relative amounts of the above products in the reaction mixtures depend both on the nature of L₂ and reaction conditions. From these data and the results of additional experiments it is concluded that, when L₂ = Ph₂PCH₂PPh₂, protonation gives initially the hydroxycarbyne complex, which can experience afterward a solvent-assisted transformation into the corresponding hydrido derivatives, possibly through an H−C(cyclopentadienyl) activation step. When L₂ = Me₂PCH₂PMe₂, the above O-protonation competes with direct proton attack at the intermetallic bond, the latter process being dominant under most of the reaction conditions. The structure of the new complexes as well as the dynamic behavior of some of them is discussed with the aid of IR and variable-temperature NMR spectroscopy.