Chemistry of Unsaturated Group 6 Metal Complexes with Bridging Hydroxy and Methoxycarbyne Ligands. 5. Heterometallic Clusters Derived from the Neutral Complex [Mo₂(η⁵-C₅H₅)₂(μ-COMe)(μ-PCy₂)(μ-CO)]

The unsaturated complex [Mo2Cp2(μ-COMe)(μ-PCy2)(μ-CO)] (1) reacts with the solvate manganese complexes [MnL(CO)2(THF)] (L = Cp, η5-C5H4Me) rapidly at room temperature in toluene solution to give the corresponding electron-precise clusters [MnMo2Cp2L(μ3-COMe)(μ-PCy2)(CO)4] (Mo−Mo = 2.986(1) Å when L = Cp), which follow from the addition of the manganese fragment to compound 1 and further spontaneous carbonylation. In contrast, the incorporation of the group 8 metal fragments M(CO)4 occurs selectively either at room temperature (reaction with [Fe2(CO)9]) or under photochemical activation (reaction with [Ru3(CO)12]) to give the 46-electron derivatives [Mo2MCp2(μ3-COMe)(μ-PCy2)(CO)5] (M = Fe, Ru), which follow from the addition of the M(CO)4 fragment to compound 1 and carbonyl migration from M to molybdenum. Simple addition of a metal fragment to the triple intermetallic bond of 1 is observed in its reaction with CuCl, which gives the unsaturated derivative [CuMo2ClCp2(μ3-COMe)(μ-PCy2)(μ-CO)]. Compound 1 can also yield tetranuclear derivatives. Thus, it reacts with [Co2(CO)8] at room temperature to give a mixture of the clusters [Co2Mo2Cp2(μ3-COMe)(μ-PCy2)(μ-CO)2(CO)4] and [Co2Mo2Cp2(μ3-COMe)(μ-PCy2)(μ-CO)(CO)6]. The heptacarbonyl compound has the expected composition, i.e., the one resulting from the addition of a Co2(CO)6 fragment to compound 1, but not the expected structure, since the PCy2 ligand is found as bridging one Mo−Co edge of the tetrahedral metal core, according to an X-ray diffraction study. In contrast, the hexacarbonyl cluster roughly has the expected structure, but has one carbonyl below the number that might have been anticipated, with the resulting unsaturation being mainly located at the Mo−Mo bond (2.686(1) Å) of this tetrahedral cluster.