Synthesis and X-ray crystal structure analysis of the triruthenium-rhodium carbonyl cluster [Ru 3Rh(μ-H) 2(CO) 10(η 5-C 5H 5)

Abstract

The pyrolysis of a mixture of the labile dimer [(Rh(CO) 2Cl) 2] and the hydridocluster [Ru 4H 2(CO) 13] in the presence of Tl(C 5H 5), in hexane, gives the mixed metal complex [Ru 3Rh(μ-H) 2(CO) 10 (η 5-C 5H 5)] as the major product. An X-ray diffraction study of this complex shows that it contains a distorted Ru 3Rh tetrahedron, two RuRu edges of which are bridged by hydrides and one RuRu edge of which is asymmetrically bridged by a carbonyl ligand. The remaining nine carbonyl ligands are terminal, with three bound to each Ru atom, while the cyclopentadienyl ligand is co-ordinated to the Rh atom. The complex crystallises in the monoclinic space group P2 1/ n with a 8.186(1), b 15.061(1), c 16.302(1) Å, β 91.06(1)°, Z = 4; 2737 observed data with F > 4σ( F) were refined by blocked-cascade least squares to R = 0.040, R w = 0.033. At low temperature, the 1H NMR spectrum of the cluster shows two signals, in the hydride region, consistent with the inequivalent hydride positions in the ground state structure, but at higher temperatures coalescence occurs, and the activation energy for this process has been found to be 38 kJ/mol at −80° C.