A Novel Bonding Scheme of an Allene System in a Transition Metal Cluster Complex. Molecular Structure of μ₃-η-(1-Methyl-3-ethyl-3-allenyl)-μ-hydrido-triangulo-tris(tricarbonylruthenium)(3Ru-Ru)

The molecular structure of μ₃-η-(1-methyl-3-ethyl-3-allenyl)-μ-hydrido-triangulo-tris(tricarbonylruthenium), HRu₃(CO)₉C₆H₉, has been determined by a single-crystal x-ray analysis. This compound crystallizes in the triclinic system, space group P1, with two molecules in a unit cell of dimensions a = 9.569 (11) Å, b = 11.231 (7) Å, c = 9.379 (5) Å, α = 95.09 (1)°, β = 90.96 (4)°, and γ = 99.75 (1)°. A total of 2890 nonzero reflections were collected with an automatic diffractometer; the structure was solved by Patterson and Fourier methods. The hydrogen atom positions were revealed when only low-angle data (0 < (sin θ)/λ ≤ 0.35 Å^-1) were used to calculate difference maps. The atom parameters were refined by least-squares techniques to R = 0.035. The molecule consists of a cluster of three ruthenium atoms each bonded to three carbonyl groups, at the corners of an isosceles triangle, and an aliene ligand. The bonding between the two parts of the molecule is attained via two π bonds and one a bond in a new arrangement found for an aliene ligand. The hydridic hydrogen atom symmetrically bridges the longest Ru-Ru bond. A comparison is made with another compound of the same molecular formula obtained by thermal rearrangement of the title compound.