Structural studies on ruthenium carbonyl hydrides. XIV. Synthesis, characterization, and crystal structure of (μ-H)₂Ru₃(η₃-η²-CHC(O)OCH₃)(CO)₈(PPh₃). An example of cis-labilization by an oxygen donor ligand

The reaction of PPh₃ with (μ-H(₂Ru₃(μ₃-η²-CHC(O)OCH₃)(CO)₉ displaces a CO ligand, rather than the coordinated oxygen atom of the acyl moiety, thereby generating (μ-H)₂Ru₃(μ₃-η²-CHC(O)OCH₃)(CO)₈(PPh₃). A single-crystal X-ray study of (μ-H)₂Ru₃(η₃-η²-CHC(O)OCH₃)(CO)₈(PPh₃) has been performed. This complex crystallizes in the triclinic space group P1 with a 9.360(1), b 11.442(1), c 15.192(1) Å, α 84.554(7), β 78.729(8), γ 83.023(3)°, V 1579.6(3) ų and Z = 2. Data for 2θ 5.0-50.0° (Mo-K_α) were collected on a Syntex P2₁ automated four-circle diffractometer and the structure was refined to R_F 4.6% for all 5601 reflections (R^F 3.4% for those 4962 reflections with |F_°| > 3σ(|F_°|). The crystal structure establishes that PPh₃ substitution occurs cis to the coordinated oxygen in that equatorial site which is trans to the non-hydrido-bridged RuRu bond. The high rate of CO displacement from (μ-H)₂Ru₃(μ₃-η²-CHC(O)OCH₃)(CO)₉, as compared with that for (μ-H)₃Ru₃(μ₃-CC(O)OCH₃)(CO₉, is attributed to cis labilization by the oxygen donor atom.