Synthesis, structure and electrochemical properties of a family of organoruthenium complexes

Abstract

Reaction of N-(2'-hydroxyphenyl)benzaldimines (abbreviated in general as H₂L-R, where R stands for the para-substituent in the benzaldehyde fragment and H stands for the dissociable hydrogen atoms) with [Ru(PPh₃)₂(CO)₂Cl₂] affords a family of organoruthenium complexes of the type [Ru(PPh₃)₂(CO)(L-R)] where the N-(2'-hydroxyphenyl)benzaldimine ligand is coordinated to the metal center as tridentate C,N,O-donor. Structure of a representative complex has been determined by X-ray crystallography. All the [Ru(PPh₃)₂(CO)(L-R)] complexes are diamagnetic, and show characteristic ¹H NMR signals and moderately intense MLCT transitions in the visible region. Cyclic voltammetry of the [Ru(PPh₃)₂(CO)(L-R)] complexes shows a reversible Ru(II)-Ru(III) oxidation within 0.38-0.68 V versus SCE, followed by an irreversible oxidation of the coordinated benzaldimine ligand within 1.09-1.27 V versus SCE. An irreversible reduction of the coordinated benzaldimine ligand is also observed near -1.1 V versus SCE. Potential of the Ru(II)-Ru(III) oxidation is observed to be sensitive to the nature of para-substituent R.