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

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)3ClL]− are obtained. Carbonylation of [Rh(C6Cl5)3] produces the insertion of CO molecules in two of the RhCaryl 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 tBuNC breaks all the rhodiumo-chloro interactions producing the compound mer-[Rh(C6Cl5)3(tBuNC)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(tBuNC)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.