Complexes of rhodium(I) with carbon monoxide, bis(diphenylphosphino)methane, or bis(diphenylarsino)methane, and various anionic ligands

Abstract

Complexes of rhodium(I) with carbon monoxide, bis(diphenylphosphino)methane (dppm), or the arsine analogue (dpam), and a variety of anionic ligands are described, and the natures of each of the novel complexes are compared with those of known complexes containing terminal or bridging chloro-ligands. In solution in acetone–methanol and in the presence of halide ions (X = Cl^–, Br^–, or I^–) cationic dinuclear ‘A-frame’ complexes [Rh₂(µ-X)(CO)₂L₂]⁺ and [Rh₂(µ-X)(µ-CO)(CO)₂L₂]⁺(L = dppm or dpam) are readily formed. In the presence of the pseudohalide ions (Z = CN^– or SCN^–) the neutral complexes [Rh₂Z₂(CO)₄L₂] are initially formed. The cyano-complexes readily dissociate one (dppm) or two (dpam) moles of CO respectively. When Z is OCN^– or N₃^– the products are dinuclear dicarbonyl complexes [Rh₂Z₂(CO)₂L₂].