Infrared studies on the complexes cis-[Rh(CO) 2(NH 3)(X)] (XCl, Br): isotopic labelling studies and normal coordinate analysis

Abstract

The infrared spectra (4000-50 cm −1) of the complexes cis-[Rh(CO) 2(NH 3)(X)] (XCl, Br) and their 15NH 3, ND 3 and 13CO isotopomers have been determined. Empirical assignments of the infrared-active modes are based on the frequency shifts caused by selective isotopic substitution experiments. The empirical assignments have been verified by a normal coordinate analysis of the in-plane vibrational modes. The potential energy distribution reveals very little coupling between the normal vibrational modes. However, there exists some coupling between ν(RhX) and ν(RhC) in the choro complex.