Transition-metal complexes of the 1,2-dipyridylethylene isomers. Part IV. Far-infrared spectra (450–80 cm.–1) of cobalt(II), nickel(II), and copper(II) halide derivatives

Abstract

The far-i.r. spectra (450–80 cm.^–1) of 32 complexes formed by cobalt(II), nickel(II), and copper(II) halides with 1,2-dipyridylethylene isomers or 1,2-di-(4-pyridyl)ethane are described, and assignments discussed, particularly of ν(MX) modes. The structures previously suggested on the basis of magnetic and electronic spectral properties of the compounds are generally confirmed, and in some cases more definite evidence regarding the metal co-ordination environment is obtained. The origin of the ‘second X-sensitive band’ in octahedral copper(II) complexes is discussed.