Some trans-chlorobis(triphenylphosphine)ruthenium(II) complexes with N,N,O-donor N-(aroyl)- N′-(picolinylidene)hydrazines

Abstract

The reactions of [Ru(PPh 3) 3Cl 2] and N-(aroyl)- N′-(picolinylidene)hydrazines (HL), derived from 2-pyridinecarbaldehyde and 4-substituted aroylhydrazines in boiling methanol provide mixed-ligand complexes having the general formula trans-[RuL(PPh 3) 2Cl]. The complexes were characterized by analytical, spectroscopic and electrochemical measurements. The +2 oxidation state of the metal ions in these complexes is confirmed by their diamagnetic nature in the solid state and electrically non-conducting behavior in solution. The X-ray structure of a representative complex has been determined. The metal ion is in a distorted octahedral N 2OP 2Cl coordination sphere. The monoanionic pyridine-N, imine-N and deprotonated amide-O donor ligand and the chlorine atom form an N 2OCl square-plane around the metal centre and the P-atoms of the PPh 3 molecules occupy the remaining two axial sites. The 31P NMR spectra of all the complexes in CDCl 3 solutions are consistent with the trans orientation of the PPh 3 molecules. Electronic spectra of the complexes in dichloromethane solution display several bands in the range 590–261 nm due to metal-to-ligand charge transfer and intraligand transitions. Cyclic voltammograms of the complexes in dimethylformamide solution display the reversible Ru(III)/Ru(II) couple in the potential range 0.40–0.52 V (versus saturated calomel electrode). The trend in these potential values reflects the polar effect of the substituents on the aroyl moiety of the ligand (L −).