Ruthenium Carbonyl Complexes with 4-R-Benzaldehyde Thiosemicarbazone as an Ancillary Ligand: Synthesis and, Structural, Spectral and Electrochemical Properties

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Reaction of 4-R-benzaldehyde thiosemicarbazone (denoted as HL-R; where H stands for the dissociable acidic proton and R (R = OCH3, CH3, H, Cl and NO2) for the substituents) with [Ru(CO)2Cl2]n in toluene in the presence of triethylamine affords a group of yellow complexes of the type [Ru(CO)2(L-R)2]. Structure of [Ru(CO)2(L-NO2)] has been determined by X-ray crystallography. In [Ru(CO)2(L-R)2] complexes, the thiosemicarbazone ligands are bound to the metal center as monoanionic bidentate N,S-donor forming four-membered chelate ring. All the complexes are diamagnetic, and show characteristic 1H NMR signals. The [Ru(CO)2(L-R)2] complexes show intense absorptions in the visible and ultraviolet regions, which have been analyzed by DFT calculations. Cyclic voltammetry on the complexes shows two irreversible oxidations near 0.87 and 1.28 V versus SCE, and an irreversible reduction around −1.24 V versus SCE.