Reactivity of rhodium(III) complexes containing chelating pentachlorophenyl ligands. Molecular structures of fac-[Rh(C6Cl5)3(py)] and mer-[Rh(C6Cl5)3((t)BuNC)3]

Article abstract of DOI:10.1016/S0020-1693(00)00202-4

The reactions of the octahedral rhodium(III) complexes [Rh(C₆Cl₅)₃] and [Rh(C₆Cl₅)₃Cl]- with neutral monodentate ligands have been studied. With pyridine, triethylphosphine or pyrazole, one of the rhodium-o-chloro bonds of the starting materials is broken and complexes of formula [Rh(C₆Cl₅)₃L] and [Rh(C₆Cl₅)₃C1L]^- are obtained. Carbonylation of [Rh(C₆Cl₅)₃] produces the insertion of CO molecules in two of the Rh-C(aryl) bonds giving the diacyl complex [Rh{C(O)C₆Cl₅}₂(C₆Cl₅)(CO)], while the reaction of [Rh(C₆Cl₅)₃] or [Rh(C₆Cl₅)₃Cl]^- with the strong σ-donor ligand (t)BuNC breaks all the rhodium-o-chloro interactions producing the compound mer-[Rh(C₆Cl₅)₃((t)BuNC)₃]. All the complexes are stable to the air and moisture in the solid state and moderately stable in deoxygenated solutions. The compounds have been studied and characterised by IR, NMR and MS. The crystal structures of fac-[Rh(C₆Cl₅)₃(py)] and mer-[Rh(C₆Cl₅)₃((t)BuNC)₃] have been determined by X-ray diffraction methods. They display distorted octahedral metal environments but, while the pyridine complex shows two C₆Cl₅ groups acting as chelate ligands bonded through the ipso-C atom and one of the o-Cl atoms, the isocyanide complex exhibits all the coordinated ligands acting as monodentate groups. (C) 2000 Elsevier Science S.A.