Crystal and molecular structure of nonacarbonyl(cyclododecatrienetriyl)hydrido-triangulo-triruthenium, HRu3(CO)9(C12H15): a ruthenium cluster with a novel allyl bonding system to the cyclododecatrienetriyl ligand

Crystals of the title compound are monoclinic, space group P21/a, with Z= 4 in a unit cell of dimensions: a= 11·18, b= 15·52, c= 15·48 A, and β= 114° 05′. Diffractometer data were used and the structure refined to R 0·080 for 1419 independent reflections. The ruthenium atoms each carry three carbonyl groups and are bonded to one another at the corners of an isosceles triangle. The two equal sides (2·776A) are unbridged, but the apical atom is equidistant from, and π-bonded to, three consecutive atoms C(1)–(3) of the cyclododecatrienyl ligand which thus form a π-allyl group. The outer two atoms of this π-allyl group are also each σ-bonded to one of the basal ruthenium atoms. Rearrangement of the bonds in the cyclododeca-1,5,9-triene ligand occurs, as the complex contains ethylenic links at C(6)–C(7) and at C(9)–C(10). The distance between the two basal metal atoms (2·92 A) is longer than the base–apex distances; this bond is probably hydrogen-bridged. In this compound, therefore, the cyclododecatrienyl ligand functions as a five-electron donor. The mean Ru–C and C–O distances for the carbonyl ligands are 1·87 and 1·17 A respectively.