Synthesis, reactivity and structures of ruthenium carbonyl clusters with telluride and hydride ligands

The reaction of [Cp*2Nb(Te2H)] (1) (Cp*=C5Me5) with [Ru3(CO)12] in boiling toluene gave [Ru3(μ2-H)2(CO)9(μ3-Te)] (2), [Ru6(μ3-H)(CO)15(μ3-Te)3][Cp*2Nb(CO)2] (3) and [Ru5(μ2-H)(CO)14(μ4-Te)][Cp*2Nb(CO)2] (4) along with already known [Ru4(CO)11(μ4-Te)2] (5). Complexes 2–4 were analytically and spectroscopically characterized and X-ray diffraction analyses of 3 and 4 were carried out. The anion of 3 is built up of a triangular hexametallic core of C3v symmetry, in which the central Ru3 triangle, being bridged by a μ3-H ligand, is composed of three corner-linked Ru3Te tetrahedra. The main structural feature of the anion of 4 is a Ru5Te octahedron. The cations in 3 and 4 are known niobocenedicarbonyl species. The reaction of 2 with bis(diphenylphosphino)methane (dppm) gave [Ru3(μ2-H)2(CO)7(dppm)(μ3-Te)] (6). Low temperature 1H-NMR spectroscopy and X-ray diffraction analysis show an unsymmetrical distribution of both hydride ligands over the triangular Ru3 basis of the Ru3Te tetrahedron. The reaction of 5 with dppm gave [Ru3(CO)7(dppm)(μ3-Te)2] (7) and known [Ru4(CO)9(dppm)(μ4-Te)2] (8). The crystal structure of 7 reveals a square pyramidal arrangement of the Ru3Te2 core. Electrochemical studies of 5 show this complex to be able to consume up to four electrons in reversible steps.