Synthesis and Crystallographic Characterization of (μ-H)₂Ru₃(CO), (μ₃-η²-MeCCOMe)

Hydrogenation of the 1, 3-dimetalloallyl cluster (μ-H)Ru₃(μ₃-η³-HCCHCOMe)(CO)₉forms the μ₃-alkyne cluster (μ-H)₂Ru₃(μ₃-η²-MeCCOMe)(CO)₉ in 11% yield, in addition to the major product (μ-H)3Ru3(μ₃-CEt)(CO)₉ (previously reported, 39%). The former product has been characterized by spectroscopic methods and by a single-crystal X-ray diffraction study. (μ-H)₂Ru₃(CO)₉(μ₃-η²-MeCCOMe) crystallizes in the centrosymmetric triclinic space group PI with a = 9.6879 (30) Å, b = 9.7830 (17) Å, c = 10.3423 (17) Å, α = 101.897 (14)°, β = 91.014 (20)°, γ = 96.836 (20)°, V = 951.4 (3) ų, and Z = 2. Diffraction data (Mo Ka, 2θ = 4.5-45.0°) were collected on a Syntex P2₁ diffractometer, and the structure was refined to R_F = 3.6% and R_wF = 3.2% for all 2790 data. All atoms, including all hydrogen atoms, were located and refined to convergence. The molecule contains a triangular array of ruthenium atoms, each of which is linked to three terminal carbonyl ligands. The intermetallic distances are Ru(1)-Ru(2) = 2.979 (1) Å, Ru(1)-Ru(3) “2.743 (1) Å, and Ru(2)-Ru(3) = 2.827 (1) Å. Hydride ligands bridge the Ru(1)-Ru(2) vector (Ru(1)-H(12) = 1.69 (5) Å; Ru(2)-H(12) = 1.77 (5) Å) and the Ru(2)-Ru(3) vector (Ru(2)-H(23) = 1.73 (6) Å; Ru(3)-H(23) = 1.60 (6) Å). The MeCCOMe fragment behaves as a μ₃-η²-alkyne ligand with σ-bonds to Ru(1) and Ru(2) (Ru(1)-C(4) = 2.082 (15) Å; Ru(2)-C(5) = 2.134 (5) Å) and a ir-linkage to Ru(3) (Ru(3)-C(4) = 2.391 (5) Å; Ru(3)-C(5) = 2.221 (5) Å). This is the first accurate structure determination of a member of the class (μ-H)₂M₃(CO)₉(μ₃-η^2-RCCR') including location of the hydride ligands.