Synthetic, structural and catalytic studies of metal carbonyl clusters of group VIII

Jones, Anthony Gould (1986) Synthetic, structural and catalytic studies of metal carbonyl clusters of group VIII. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Derivative of Ru₃(CO)₁₂ and Ru₆C(CO)₁₇ with monodentate phosphines and bidentate phosphines and arsines have been prepared and characterised. The fluxional behaviour of the hexa-ruthenium species has been studied by NMR. Catalytic studies with 1-pentene have been performed under mild conditions (8^o or 40^oC/latm H₂/72 or 24h). The larger and sterically hindered clusters are inactive. Other derivatives of Ru₃(CO)₁₂ lack the induction period of the parent cluster. Monodentate and rigid bidentate derivatives have a high initial activity which falls rapidly compared to the more flexible ligands. Major changes occur in the order of activity between 8^oC (minimal decomposition) and 40^oC (extensive decomposition). A chiral cluster, Ru₃(CO)₁₀ (-) DIOP, has been prepared and characterised. The molecule crystallises in the P2₁2₁2₁ system a = 14.344(5)AA, b = 14.763(3)AA, c = 21.830(1)AA and Z = 4. The structure was refined to R + 0.0604 for 3537 reflections. The (-)DIOP ligand occupies a bridging, equatorial position and considerably distorts the cluster, two semi-bridging carbonyls being evident across this Ru-Ru bond. Attempts to prepare a chiral mixed metal cluster led to the synthesis of (Et₄N) Fe₄RhC(CO)₁₃PPh₃, which was characterised by X-ray crystallography. Some structural parameters are ill-defined due to the crystal morphology and disorder. The molecule crystallised in the P2₁/m system, a = 10.440(1)AA, b = 11.978(3)AA, c = 18.040(2)AA, β= 101.78(1)^o and Z = 2. The structure was refined to R = 0.241. The cluster contains a square pyramid with the Rh atom in the basal plane.