An easy electrochemical and chemical synthesis of [Ru(bpy)(CH3CN)2Cl2]: a synthon for heteroleptic tris(diimine)Ru(ii) complexes

Abstract

A novel approach for the synthesis of heteroleptic tris(diimine) ruthenium complexes is reported. This strategy is based on the electrochemical or chemical reduction of Ru(III) precursor complexes in MeCN such as [Ru(bpy)(X)Cl₃] (bpy = 2,2′-bipyridine; X = MeCN (1) or MeOH (2)). This method allows the preparation with high yield of the highly valuable [Ru(bpy)(MeCN)₂Cl₂] synthon (3). The full characterization (mass spectrometry, ¹H NMR, absorption spectroscopy and electrochemistry) of [Ru(bpy)(MeCN)₂Cl₂] as a pure compound is reported for the first time. Indeed the later was previously only obtained in mixtures with the corresponding tris(acetonitrile) derivative: [Ru(bpy)(MeCN)₃Cl]Cl. ¹H NMR analysis of 3 indicates that its structure corresponds to the cis(Cl)–cis(MeCN) isomer form. [Ru(bpy)(MeCN)₂Cl₂] has been further used to synthesize [Ru(bpy)(Me₂bpy)Cl₂] (Me₂bpy = 4,4′-dimethyl-2,2′-bipyridine) for which X-ray analysis indicates that the two chloride ligands are also in cis position.