Hydrogen Atom Transfer Reactions of the Unsaturated Hydroxycarbyne Complex [W2Cp2(μ-COH)(μ-PPh2)2]BF4

The hydroxycarbyne complex salt [W2Cp2(μ-COH)­(μ-PPh2)2]­BF4 (1) reacted rapidly with water in the presence of the oxidant [FeCp2]­BF4 to give the hydroxo complex salt [W2Cp2(OH)­(μ-PPh2)2(CO)]­BF4, a preparation that could be replicated using the neutral carbonyl complex [W2Cp2(μ-PPh2)2(μ-CO)] (2) instead. A similar reaction took place slowly with HSPh and rapidly in the presence of [FeCp2]­BF4, to yield the known 32-electron complex salt [W2Cp2(SPh)­(μ-PPh2)2(CO)]­BF4. In contrast, 1 did not react with PhOH or H2Np-tol even in the presence of [FeCp2]­BF4. However, a fast reaction between these molecules and 2 took place in the presence of [FeCp2]­BF4, to give the phenolato complex salt [W2Cp2(OPh)­(μ-PPh2)2(CO)]­BF4 and the imido-hydride [W2Cp2(μ-H)­(Np-tol)­(μ-PPh2)2(CO)]­BF4 (W–W = 2.9135(8) Å), respectively, after formal elimination of hydrogen. The hydroxycarbyne complex 1 reacted rapidly with PH2Cy to give the hydride derivative [W2Cp2(H)­(μ-PPh2)2(CO)­(PH2Cy)]­BF4, this requiring H-migration from O to W atoms. The M–H bonds in the latter hydride cations were deprotonated by strong bases to give the corresponding neutral complexes [W2Cp2(Np-tol)­(μ-PPh2)2(CO)] and [W2Cp2(μ-PPh2)2(CO)­(PH2Cy)]. Compound 1 also reacted easily with two-electron donors such as NCMe, CNtBu, and CNp-tol, to give products derived from the addition of two molecules of reagent in each case, and some rearrangement of the COH ligand. The first reaction gave the new cationic complex [W2Cp2(μ-PPh2)2(μ-N:N,N′-N2HC2Me2)­(CO)]­BF4, derived from the C–C coupling of two nitrile molecules accompanied by an O to N shift of the hydroxycarbyne proton. In contrast, no C–C coupling processes were observed in the reactions with isocyanides, although proton migration occurred in all cases, either to the metal (reaction with CNtBu), to give the hydride [W2Cp2(H)­(μ-PPh2)2(μ-CNtBu)­(CNtBu)]­BF4, or to the N atom of one of the incoming isocyanides (reaction with CNp-tol), to give the aminocarbyne derivative [W2Cp2{μ-CN­(H)p-tol}­(μ-PPh2)2(CNp-tol)­(CO)]­BF4.