Synthesis, characterization, and electrochemical studies on some selected dinuclear rhodium complexes

New binuclear rhodium(I) complexes containing terminal carbon monoxide, bridging dpm (bis(diphenylphosphino)methane) ligands, and a triazolate anion or pyrazolate (pz) derivative in the bridgehead position have been investigated. Products obtained by the chemical oxidation of these complexes using I₂, Br₂, and CI₂ have also been synthesized. It has been found that with some of the pz derivatives that are not substituted in the 4-position treatment of Br₂ and CI₂ with some of the complexes leads to substitution in the 4-position as well as oxidative addition at the metal centers.

The electrochemical behavior of several rhodium complexes has been examined using cyclic voltammetry and bulk electrolysis. A new Rh(II)-Rh(II) complex has been prepared by the electrochemical oxidation of a methylene chloride solution containing trans-Rh₂CI₂(μ-C0)(μ-Cl)(dpm)₂ in the presence of excess chloride to give the compound, [Rh₂CI₂(μ-C0)(μ-Cl)(dpm)₂]PF₆, 4. This new product when treated with CO undergoes simultaneous substitution, addition, and reduction reactions to produce a mixture of Rh(I)-Rh(I) and Rh(II)- Rh(II) dimers.