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

Article abstract of DOI:10.1021/om060999k

The reactions of the 30-electron hydride [Mo₂Cp ₂(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-PCy ₂)(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) A). The title unsaturated hydride reacts readily with isocyanides to give in good yield the insertion products [Mo₂Cp ₂(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 (PhCH₂N ₃) to give two 32-electron derivatives, the azavinylidene complex [Mo₂Cp₂(μ-N=CHPh)-(μ-PCy₂)(CO) ₂] (Mo-Mo = 2.632(1) A) and the amido derivative [Mo ₂Cp₂{μ-NH(CH₂Ph)}(μ-PCy ₂)-(CO)₂], in a 2:1 ratio. The latter product can be obtained almost selectively by reaction of the triply bonded anion [Mo ₂Cp₂(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.