The title compound reacted rapidly with CN(t)Bu at room temperature by displacing the BF(4)(-) ligand and incorporating three molecules of isocyanide to yield the electron-precise complex [Mo(2)Cp(2)(μ-PPh(2))(2)(CN(t)Bu)(3)(CO)](BF(4))(2), which was obtained as a mixture of cis and trans isomers. Reaction with several HER(n) molecules (HER(n) = HSPh, HSePh, H(2)PCy) took place with formal elimination of HBF(4) and spontaneous carbonylation to give the electron-precise cations [Mo(2)Cp(2)(μ-ER(n))(μ-PPh(2))(2)(CO)(2)](+). Reactions with several bidentate ligands (L(2)H) having acidic E-H bonds (2-hydroxypyridine, 2-mercaptopyridine, cathecol, 2-aminophenol, and 2-aminothiophenol) proceeded analogously with deprotonation of these bonds with the preference E = S > O > N. The N,O-donor ligands yielded 32-electron chelate derivatives of the type [Mo(2)Cp(2)(O,N-L(2))(μ-PPh(2))(2)(CO)]BF(4) (L(2) = OC(5)H(4)N, OC(6)H(4)NH(2)), whereas the S,N-donors yielded 34-electron, S-bridged complexes [Mo(2)Cp(2)(μ-S:S,N-L(2))(μ-PPh(2))(2)(CO)]BF(4) [L(2) = SC(5)H(4)N (Mo-Mo = 2.8895(8) Å), SC(6)H(4)NH(2)]. However, reaction with catechol gave a monodentate derivative [Mo(2)Cp(2)(O-OC(6)H(4)OH)(μ-PPh(2))(2)(CO)]BF(4). In contrast, reactions of the title complex with several carboxylic acids and related species (acetic, benzoic, and thioacetic acids, acetamide, thioacetamide, and sodium diethyldithiocarbamate) were insensitive to the nature of the donor atoms and gave in all cases 32-electron chelate derivatives of type [Mo(2)Cp(2)(κ(2)-L(2))(μ-PPh(2))(2)(CO)]BF(4). All of the above cations having Mo-bound OH, NH, or NH(2) groups were easily deprotonated upon reaction with 1,8-diazabicycloundec-7-ene (DBU) or other bases to give neutral complexes which exhibited different coordination motifs depending on the donor atoms, including chelate complexes of the type [Mo(2)Cp(2)(κ(2)-L(2)')(μ-PPh(2))(2)(CO)] (L(2)' = OC(6)H(4)O, OC(6)H(4)NH), the bridged complexes [Mo(2)Cp(2)(μ-S,N:S,N-SC(6)H(4)NH)(μ-PPh(2))(2)] and [Mo(2)Cp(2){μ-S,N-N(S)CMe}(μ-PPh(2))(2)], and the terminal acetylimido complex [Mo(2)Cp(2){N-N(O)CMe}(μ-PPh(2))(2)(CO)].

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The title compound reacted with CO at room temperature in the presence of excess HBF(4)·OEt(2) to yield a mixture of the electron-precise complexes [W(2)Cp(2)(μ-PPh(2))(2)(CO)(4)](BF(4))(2) and [W(2)Cp(2)(μ-PPh(2))(2)(CO)(3)(OH(2))](BF(4))(2), with the aquo ligand in the latter complex being easily displaced by simple donors such as acetonitrile. Reaction of the title complex with simple acidic molecules such as HSPh or HBr took place rapidly with elimination of H(2)O to give the 32-electron cations [W(2)Cp(2)(Z)(μ-PPh(2))(2)(CO)](+) [Z = Br, SPh (W-W = 2.8076(9) Å)], which were reversibly carbonylated to give the electron-precise derivatives [W(2)Cp(2)(μ-Z)(μ-PPh(2))(2)(CO)(2)](+). Reaction with hydrogen sulfide likely proceeded analogously, but also involved fast cleavage of the second S-H bond to give the sulfido hydride cation [W(2)Cp(2)(μ-H)(μ-PPh(2))(2)(S)(CO)](+). Deprotonation of the latter cation with 1,8-diazabicycloundec-7-ene (DBU) in the presence of excess H(2)S gave a mixture of the corresponding sulfido and disulfido complexes [W(2)Cp(2)(μ-PPh(2))(2)(S)(CO)] and [W(2)Cp(2)(κ(2)-S(2))(μ-PPh(2))(2)(CO)]. Reactions of [W(2)Cp(2)(OH)(μ-PPh(2))(2)(CO)]BF(4) with several bidentate ligands (L(2)H) having weakly acidic H atoms (L(2) = SC(5)H(4)N, SC(6)H(4)NH(2), NHC(S)Ph) gave the unsaturated chelate derivatives [W(2)Cp(2)(κ(2)-L(2))(μ-PPh(2))(2)(CO)]BF(4). The N-H bonds in the latter cations could be further deprotonated with strong bases (DBU or NaOH) to give neutral derivatives displaying either chelate (N,S-SC(6)H(4)NH) or imido-like terminal ligands (N-NC(S)Ph), respectively. The related chelate complex [W(2)Cp(2)(O,O'-OC(6)H(4)O)(μ-PPh(2))(2)(CO)] (W-W = 2.836(1) Å) was obtained in high yield from the reaction of the thiolato complex [W(2)Cp(2)(SPh)(μ-PPh(2))(2)(CO)]BF(4) with catechol in the presence of DBU.

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, CN t Bu, 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 CN t Bu), to give the hydride [W2Cp2(H)­(μ-PPh2)2(μ-CN t Bu)­(CN t Bu)]­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.