Reactivity of the Unsaturated Hydride [Mo2(η5-C5H5)2(μ-H)(μ-PCy2)(CO)2] toward P-Donor Bidentate Ligands and Unsaturated N-Containing Organic Molecules

The reactions of the 30-electron hydride [Mo2Cp2(μ-H)(μ-PCy2)(CO)2] with the bidentate P-donor ligands bis(diphenylphosphino)methane (dppm), bis(dimethylphosphino)methane (dmpm), and tetraethylpyrophosphite (tedip) lead to the electron-precise derivatives [Mo2Cp2(μ-H)(μ-PCy2)(CO)2(μ-L2)] (L2 = dppm, dmpm, tedip), in which the bidentate ligand bridges the dimetal center. In the reaction with dppm, the tricarbonyl derivative [Mo2Cp2(μ-H)(μ-PCy2)(CO)3(κ1-dppm)] is also obtained as a minor byproduct. All of these compounds are obtained as mixtures of isomers, most of them interconverting in solution, and the structure of the major isomer of the tedip derivative was confirmed through an X-ray diffraction study (Mo−Mo = 3.2251(5) Å). The title unsaturated hydride reacts readily with isocyanides to give in good yield the insertion products [Mo2Cp2(μ-η,κ:η,κ-HCNR)(μ-PCy2)(CO)2] (R = p-tolyl, tBu), having a 5e-donor formimidoyl ligand, as confirmed by an X-ray study of the tBu compound. When R = p-tolyl, the addition derivative [Mo2Cp2(μ-H)(μ-PCy2)(CO)2(CNR)2] is also obtained as a minor product. Although the title hydride does not react with acetonitrile or simple diazo compounds, it reacts readily with benzyl azide (PhCH2N3) to give two 32-electron derivatives, the azavinylidene complex [Mo2Cp2(μ-NCHPh)(μ-PCy2)(CO)2] (Mo−Mo = 2.632(1) Å) and the amido derivative [Mo2Cp2{μ-NH(CH2Ph)}(μ-PCy2)(CO)2], in a 2:1 ratio. The latter product can be obtained almost selectively by reaction of the triply bonded anion [Mo2Cp2(μ-PCy2)(μ-CO)2]- with benzyl azide in the presence of H2O as a source of protons. The solution structures of the new complexes are discussed on the basis of the solid-state X-ray studies and the IR and variable-temperature NMR (1H, 31P, 13C) data, and the reaction pathways responsible for the formation of the new complexes are discussed on the basis of the available information.