Reactivity of the Unsaturated Hydride [Mo2(η 5-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(í-H)(í-PCy2)(CO)2] (Cp ) è5-C5H5) with the 17-electronfragment precursors [M2Cp2(CO)n] (M ) Mo, W, n ) 6; M ) Ru, n ) 4) or [Mn2(CO)10] lead to the 46-electron clusters [Mo2MCp3(í-PCy2)(í3-CO)(CO)4] (M) Mo, W), [Mo2RuCp3(í-PCy2)(í-CO)(CO)3], and [MnMo2Cp2(í-PCy2)(í-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¢ ) è5-C5H4CH3), then leading to the 46-electron hydride clusters [MMo2Cp2(í3-H)(í-PCy2)(CO)7] (M ) Cr, Mo, W) and [MnMo2Cp2Cp¢(í3-H)(í-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 ModMo 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(í3-H)(í-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(í-PCy2)(CO)6] (Fe-Mo ) 2.931(1) Å).