Electron addition to dirhodium complexes: an electron spin resonance study

Abstract

Exposure of dilute solutions of Rh₂(O₂CMe)₄ and Rh₂(O₂CCF₃)₄ in various solvents to ⁶⁰Co γ-rays resulted in electron capture, the resulting unstable species being detected and characterized by e.s.r. spectroscopy. Rh₂(O₂CMe)₄ gave an axially symmetric anion with the electron located primarily in a combination of d_z² orbitals. The initial species showed an e.s.r. spectrum which was solvent independent, but the products formed on annealing varied with the solvent. It is suggested that ligand loss precedes dissociation into monorhodium species. Rh₂(O₂CCF₃)₄ gave a non-axial species upon irradiation at 77 K, showing that ligand loss is more facile, as expected for the weak CF₃CO₂^– ligand.