Abstract

SPECTROSCOPIC EVIDENCE FOR STERIC ENHANCEMENT OF RESONANCE IN RHODIUM (III) CHLORIDE COMPLEXES

Penke Vijaya Babu, Sunder Kumar Kolli and Manam Sreenivasarao*

Abstract

The assignments reveal that the carboxyl substituted complexes are isolated as fac- isomers and all the remaining seven complexes are having mer-octahedral configuration. Using these sulphides as ligands Rhodium (III) chloride complexes have been synthesized and analyzed. The infrared spectra of these complexes have been recorded in the region 600– 200 cm-1. Generally the electron releasing group in Benzene ring decreases the v(Rh-S) stretching frequency value from the present one where as the electron withdrawing group increases the v(Rh-S) stretching frequency value form its parent one. Otherwise the electron donor exerts a weakening effect on the Rh-S band and the - electron acceptor removes from the metal. The appearance of –OH bond in the complexes of carboxylic substituted ligands shows the absence of intra molecular hydrogen bonding between –OH of carboxylic group and chlorine. The carboxyl frequency of meta and para carboxylic groups gets increased when compared with the ligands. But in the case of higher stability of the meta and para isomers. In recording the electronic spectra the same solvent was used both for the complex and ligand. Generally the bathochromic shift is observed when there is an electron releasing group present in the benzene ring and the presence of electron withdrawing group or steric inhibition results in a hypsochromic shift. The complexes involving p-NO2 and p-COOH substituted phenyl methyl sulphides have the absorption bands almost identical with those of ligands. When an electron donor is present in the benzene ring the electronic transition is from S(of Sme) to Rh and when there is a π-electron acceptor in benzene ring the electronic transition is from Rh to S is quite possible. The phenomenon of steric enhancement of resonance is observed in these complexes from infrared, electronic and „H NMR spectral studies are presented.

Keywords: Stretching frequency, Molecular hydrogen bonding and absorption bands.