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(Nptol)( 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.