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

The reaction of [Cp-2*Nb(Te2H)] (1) (Cp* = C5Me5) with [Ru-3(CO)(12)] in boiling toluene gave [Ru-3(mu(2)-H)(2)(CO)(9)(mu(3)-Te)] (2), [Ru-6(mu(3)-H)(CO)(15)(mu(3)-Te)(3)][Cp-2*Nb(CO)(2)] (3) and [Ru-5(mu(2)-H)(CO)(14)(mu(4)-Te)][Cp-2*Nb(CO)(2)] (4) along with already known [Ru-4(CO)(11)(mu(4)-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 C-3, symmetry, in which the central Ru-3 triangle, being bridged by a mu(3)-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 [Ru-3(mu(2)-H)(2)(CO)(7)(dPPM)(mu(3)-Te)] (6). Low temperature H-1-NMR spectroscopy and X-ray diffraction analysis show an unsymmetrical distribution of both hydride ligands over the triangular Ru-3 basis of the Ru3Te tetrahedron. The reaction of 5 with dppm gave [Ru-3(CO)(7)(dppm)(mu(3)-Te)(2)] (7) and known [Ru-4(CO)(9)(dppm)(mu(4)-Te)(2)] (8). The crystal structure of 7 reveals a square pyramidal arrangement of the Ru3Te, core. Electrochemical studies of 5 show this complex to be able to consume up to four electrons in reversible steps. (C) 2002 Elsevier Science B.V. All rights reserved.