Synthesis and Characterisation of Diruthenium Paddlewheel Compounds Bearing 2,6-Di(p-tolyl)benzoate Ligands

The mixed carboxylate diruthenium complexes trans-[Ru 2 II,III (O2CCH3)2(O2CAr)2Cl] (I) and trans-[Ru 2 II,II (O2CCH3)2(O2CAr)2] (II) (O2CAr = 2,6-di(p-tolyl)benzoate) have been synthesised along with [Ru 2 II,III (O2CAr)4Cl] (III) and the homoleptic complex [Ru 2 II,II (O2CAr)4] (IV). The structures trans-[Ru2(O2CCH3)2(O2CAr)2Cl(thf)]·(thf) and [Ru2(O2CAr)4Cl(η 1-CH2Cl2)] were determined by X-ray crystallography, and display the expected paddlewheel arrangement of the carboxylate ligands around the diruthenium core. The structure of III is a rare example of a structurally characterised dichloromethane complex, highlighting the Lewis acidic nature of the diruthenium axial position. The bulky −O2CAr ligand protects the axial positions from intermolecular interactions in the absence of strong nucleophiles for III and IV, and the effect this has on the electronic structure of the diruthenium core in these complexes was investigated by cyclic voltammetry, electronic absorption spectroscopy and magnetic susceptibility studies.