High nuclearity carbonyl clusters of rhodium. Part 2. Crystal and molecular structure of the tetramethylammonium salt of dodeca-µ-carbonyl-dodecacarbonylhydrido-polyhedro-tridecarhodate(4–)–1-methylpyrrolidin-2-one (1/3)

Abstract

The title compound, [N(CH₃)₄]₄[Rh₁₃H(CO)₂₄]·3C₅H₉NO, crystallises in the triclinic space group P with unit-cell dimensions a= 22.596(11), b= 14.263(7), c= 14.512(8)Å, α= 65.56(3), β= 107.58(4), γ= 100.86(5)°, and Z= 2. The structure has been solved by conventional Patterson and Fourier methods from single-crystal X-ray counter data and refined by least-squares methods to R 0.061 for 3 680 significant reflections. The anion, of idealised C_s symmetry, containing a centred twinned-cuboctahedron of metal atoms, is similar to that of the other members of the family [Rh₁₃H_5–n(CO)₂₄]^n– already studied. The mean value of the Rh–Rh bond lengths, ranging from 2.718(3) to 2.894(3)Å, is 2.782 Å. The Rh–C and C–O interactions for the 12 terminal and for the 12 edge-bridging CO groups have mean values of 1.80, 1.18, and 1.97, 1.21 Å, respectively. The hydride atom has been located in a semi-octahedral cavity, i.e. on a square face of the cluster, bisected by the ideal mirror plane.