Square, tetragonal and tetrahedral complexes of nickel (II) with quinoxaline

Abstract

The reaction of quinoxaline with nickel halides has been investigated, Complexes of the form QNiX 2, where X = Cl, Br and Q 2NiX 2, where X = I, are characterised. The visible absorption and reflectance spectra, and magnetic behaviour of the compounds are used to elucidate their structure. The iodide is square and diamagnetic, whilst the chloride is a tetragonal polymer and paramagnetic. Two isomeric forms of the polymeric bromide are reported; the yellow form is tetragonal and paramagnetic, whilst the brown form is believed to involve alternating tetrahedral and tetragonal nickel atoms. Infra-red, conductivity and molecular weight data are listed. Evidence is presented which indicates that the polymers are not totally depolymerised upon solution. The crystal field strength, and Racah parameter B, are computed.