Cluster Compounds Bearing both High- and Low-Valent Transition Metal Fragments: The Reactions of Imido Carbonyl Cluster Ru₃(CO)₁₀(μ₃-NPh) with Dioxo Acetylide Complexes (C₅Me₅)W(O)₂(CCR), R = Ph and CMe=CH₂

Heterobimetallic compounds (C₅Me₅)W(O)(μ-O)Ru₃(μ₃-NPh)(CCR)(CO)₈, R = Ph and CMe= CH₂ (1a and 1b), which contain the high oxidation state dioxo tungsten fragment and the low-valent ruthenium carbonyl unit, were obtained from the reaction of Ru₃(μ₃-NPh)(CO)₁₀ with (C₅Me₅)W(O)₂(CCR), R = Ph and CMe=CH₂. These complexes consist of an open triangular Ru₃ core with the dioxo tungsten unit coordinated to the central Ru atom via a W=O→Ru dative interaction. Conversion to the pentametallic complex (C₅Me₅)W(O)(μ-O)-Ru₄(μ₃-PPh)(CCPh)(CO)₁₀ (2) was realized by treatment of 1a with Ru₃(CO)₁₂ in refluxing toluene, while heating a solution of 1b led to the isolation of (C₅Me₅)W(μ-O)₂Ru₃(μ ₃-NPh)-(CCCMe=CH₂)(CO)₆ (4) through the removal of two CO ligands. Reaction of 4 with PMe₂-Ph was examined, giving the monosubstituted (C₅Me₅)W(μ-O)₂Ru₃(CCCMe=CH₂)(μ₃-NPh)(CO)₅(PMe₂Ph) (5) in moderate yield, of which the X-ray diffraction study lends support to the identification of its precursor 4. The reactivity of complex 4 with CO was then established, affording (C₅Me₅)W(μ-O)₂Ru₃(μ₃-NPh)(CCCMe=CH₂)(CO)₇ (6) and (C₅Me₅)W(O)₂-Ru₃(μ₃-NPh)(CCCMe=CH₂)(CO)₈ (7), which are generated by removal of the vinyl or the dioxo tungsten fragment from the coordination sphere of ruthenium metal, respectively. In addition, upon exposure to pressurized CO atmosphere, complex 7 slowly converts to Ru₃-(CO)₉[C₆H₅O(CONHPh)] (8), which has been crystallographically shown to possess a Ru₃ skeleton with the vinylacetylide linked with one bridging CO and a carboxamido fragment; the latter is derived from the coupling of CO with the imido group. A possible reaction mechanism leading to the formation of 8 is discussed.