Polynuclear ruthenium clusters containing stibine, stibene, and stibinidene ligands

Abstract

The reaction of [Ru3(CO)10(µ-dppm)] with SbPh3 has been investigated. Me3NO activation of [Ru3(CO)10(µ-dppm)] in the presence of excess SbPh3 yields the known cluster [Ru3(CO)9(SbPh3)(μ-dppm)] (1) in nearly quantitative yield. Refluxing 1 in THF yields the new triruthenium clusters [Ru3(CO)8{μ,η2-C(O)Ph}(µ-SbPh2)(µ-dppm)] (2) and [Ru3(CO)9(σ-C6H5)(μ-SbPh2)(µ-dppm)] (3). Both clusters exhibit an opened Ru3 polyhedron supported by a bridging stibene ligand (SbPh2), whose formation results from the cleavage of an Sb–Ph bond of the SbPh3 ligand in 1. Cluster 2 contains a μ,η2-C(O)Ph ligand formed by the coupling of the cleaved Ph moiety with a coordinated CO ligand. In contrast, cluster 3 contains a σ-bonded phenyl moiety that is situated trans to the μ-SbPh2 moiety. Thermolysis of [Ru3(CO)10(µ-dppm)] with SbPh3 at 80°C furnished the new cluster [Ru3(CO)7(σ-C6H5)(μ-SbPh2)2{μ-C(=O)C6H4P(Ph)CH2PPh2}] (4) as the major product, along with 2 and 3. Control experiments involving 2 and excess SbPh3 at 80°C afforded 4. In contrast, the reaction between [Ru3(CO)10(µ-dppm)] and SbPh3 at 110°C furnished the unusual Ru6Sb2 cluster [Ru6(CO)13(μ-CO)(μ-SbPh2)(μ4-SbPh){μ-C(=O)C6H4P(Ph)CH2PPh2}(μ-dppm)] (5) in addition to 2. The results of thermal control experiments demonstrating the conversion of 1 to 5 are discussed. The molecular structures of 2–5 have been established by X-ray crystallography, and the bonding in these new clusters has been examined by electronic structure calculations.