The use of amidinate ligands in paddlewheel diruthenium chemistry

Abstract

The amidinate anions have been widely used in the formation of dinuclear complexes with paddlewheel structure. The higher donor character of this type of ligands, compared to carboxylate ligands, increases the electronic density of the dimetallic units giving, in the case of ruthenium, stable complexes with a large variety of oxidation states containing Ru24+, Ru25+ and Ru26+ units. Even complexes with Ru22+, Ru23+ and Ru27+ cores have been detected in electrochemical measurements and isolated in some cases. The influence of formamidinate and benzamidinate ligands in the synthesis, characterization, properties and reactivity of metal-metal bonded diruthenium complexes with paddlewheel structure in several oxidation states is considered. A revision of the electronic and magnetic properties of diruthenium complexes and their relationship with the different electronic configurations found in this type of complexes is broadly documented. Additionally, the switching between oxidation states is considered through the discussion of the results obtained by electrochemical measurements. Finally, the most relevant applications of the amidinatodiruthenium complexes are also reviewed.