Cyclic Voltammetry Study of <i>Closo</i>-Ruthenacarboranes

Abstract

Electrochemical properties of transition metal complexes are important parameters that should be considered for the successful application of these compounds in catalytic reactions. The proper choice of ligands and the type of its coordination allow the construction of a catalyst with high performance. The reversibility of complex oxidation is a prerequisite for successful participation in redox catalysis, while the potential values correlate with the rate of the process and necessary catalyst loading. This work summarizes the results of the exploration of a series of ruthenium carborane complexes based on the nido-C2B9 ligand obtained in our group by cyclic voltammetry and describes the found correlations. The knowledge of the electrochemical properties of the studied ruthenacarboranes is required for the optimization of its structure for successful catalysis of Atom Transfer Radical Polymerization or other applications. It was found that the value of the potential of reversible Ru(II)-Ru(III) transition may vary from −0.501 to 0.389 V versus Fc|Fc+ couple, depending on the nature of auxiliary phosphine, halogen or nitrile ligand, natural bite angle of κ2-diphosphine ligand and the presence of alkyl substituents in the carborane cage. The further oxidation towards formal Ru(IV) may be reversible or not depending on the complex structure. The found trends are in good agreement with the earlier performed findings in the field of coordination chemistry and should be considered as a tool for obtaining of complexes suitable for catalytic applications.

Keywords

• ruthenacarboranes
• cyclic voltammetry
• electrochemistry
• ruthenium complexes
• diphosphines