High nuclearity carbonyl clusters of rhodium. Part 1. Crystallographic characterization of dodeca-µ-carbonyl-dodecacarbonyldihydrido-polyhedro-tridecarhodate(3–) in its benzyltriphenylphosphonium salt

Abstract

The title complex crystallizes in the monoclinic space group P2₁/n with unit-cell dimensions a= 14.334 (2), b= 29.231(4), c= 24.626(3)Å, β= 94.61(3)°, and Z= 4. The structure has been determined by conventional methods from X-ray single-crystal counter data and refined by least-squares calculations to R 0.061 for 7 286 significant diffraction intensities. The [Rh₁₃H₂(CO)₂₄]^3– anion contains a polyhedron of rhodium atoms consisting of a fragment of hexagonal close packing (D_3h symmetry). The mean Rh–Rh distance is 2.794 Å. Twelve of the CO ligands are terminally bonded and 12 symmetrically edge bridging on half of the polyhedron edges; the idealized overall molecular symmetry is C_s. On the basis of the Rh–Rh distances and of the holes left by the ligands on the cluster surface, the hydride atoms have been located in two semi-octahedral cavities of the cluster.