Reactivity of the Unsaturated Hydride [Mo₂(η⁵-C₅H₅)₂(μ-H)(μ-PCy₂)(CO)₂] toward 17- and 16-Electron Metal Carbonyl Fragments: Rational Synthesis of Electron-Deficient Heterometallic Clusters

Reactions of the 30-electron hydride [Mo2Cp2(μ-H)(μ-PCy2)(CO)2] (Cp = η5-C5H5) with the 17-electron-fragment precursors [M2Cp2(CO)n] (M = Mo, W, n = 6; M = Ru, n = 4) or [Mn2(CO)10] lead to the 46-electron clusters [Mo2MCp3(μ-PCy2)(μ3-CO)(CO)4] (M = Mo, W), [Mo2RuCp3(μ-PCy2)(μ-CO)(CO)3], and [MnMo2Cp2(μ-PCy2)(μ-CO)2(CO)5]. The structure of the trimolybdenum cluster was confirmed by an X-ray diffraction study and displays two long (ca. 3.1 Å) and one short Mo−Mo distance (2.743(1) Å). The title unsaturated hydride also proved to be highly reactive toward the appropriate precursors of 16-electron fragments such as M(CO)5 (M = Cr, Mo, W) and MnCp‘(CO)2 (Cp‘ = η5-C5H4CH3), then leading to the 46-electron hydride clusters [MMo2Cp2(μ3-H)(μ-PCy2)(CO)7] (M = Cr, Mo, W) and [MnMo2Cp2Cp‘(μ3-H)(μ-PCy2)(CO)4]. The structures of the compounds having Mo2W and Mo2Mn skeletons were also determined by X-ray diffraction methods, both of them displaying Mo−Mo distances (ca. 2.6 Å) somewhat shorter than expected for double MoMo bonds and Mo−M distances longer than the corresponding single-bond lengths. A similar reaction takes place with the 12-electron compound CuCl, to give the hydride [CuMo2ClCp2(μ3-H)(μ-PCy2)(CO)2]. In contrast, the reaction of the title hydride with [Fe2(CO)9], a precursor of the 16-electron fragment Fe(CO)4, gives the heterodinuclear complex [FeMo(μ-PCy2)(CO)6] (Fe−Mo = 2.931(1) Å).