X-RAY AND CONFORMATION ANALYSIS OF THE NEW TRINUCLEAR CLUSTER OF OSMIUM Os3(μ,η2-OCC6H5)(η3-C3H5)(CO)9

The crystal structure of the Os-3(mu,eta(2)-O=CC6H5)(eta(3)-C3H5)(CO)(9) cluster synthesized by the reaction of the (mu-H)Os-3(mu-O=CC6H5)(CO)(10) complex with allylamine in chloroform was determined by X- ray analysis. Prolonged storage of the reaction mixture led to N-C bond cleavage in allylamine and eta(3)-addition of the allyl fragment at one of the Os atoms (Os-C 2.246 angstrom, 2.248 angstrom, and 2.273 angstrom). The unit cell parameters of the complex are a = 9.494(1) angstrom, b = 10.479(1) angstrom, c = 12.474(2) angstrom, alpha= 84.55(1)degrees, beta=70.08(1)degrees, gamma= 70.72(1)degrees, V = 1255.8(4) angstrom(3), space group P (1) over tilde, Z = 2; C19H10O10Os3; d(calc) = 2.922 g/cm(3), 3085 I-hkl > 2 sigma(1) of 3611 collected reflections; R = 0.0252. The structure of Os-3(mu,eta(2)-O=CC6H5)(eta(3)-C3H5)(CO)(9) is molecular. The plane of the Os3 triangle and the OsCOOs plane are connected according to the "butterfly" principle with an angle of 103.4 degrees between them. The Os-Os distances in the cluster core vary from 2.836(1) angstrom to 2.844(1) angstrom; the Os-C-carb distances are 1.88(1)-1.97(1) angstrom; the distances to the atoms of the bridging ligands are Os-C 2.11(1) angstrom, Os-O 2.14(1) angstrom; the O-C bridging bond is 1.24(1) angstrom. The conformations of the Os-3(mu,eta(2)-O=CC6H5)(eta(3)-C3H5)(CO)(9) triosmium cluster were studied theoretically. The potential curve of the internal rotation of the allyl ligand relative to the Os(1)-C(9) bond was determined. The rotation barrier of the allyl ligand in crystal relative to the Os(1)-C(9) bond is 8.38 kJ/mol, and the rotation of the ligand is not hindered. The effects of the intra- and intermolecular interactions on the conformation state of the cluster complex are considered.