Thermal, structural and electrical studies of the chloro complexes of cobalt, nickel, copper and zinc with 2-methylquinoxaline

Abstract

The chloro compounds of 2-methylquinoxaline (MeQ) with cobalt(II), nickel(II), copper(II) and zine(II) were prepared in ethanolic solution from which the solid compounds were isolated. The suggested structure for the cobalt and zinc compounds is tetrahedral, while for the nickel and copper compounds it is octahedral. The techniques of thermogravimetry and differential thermal analysis show that the compounds Co(MeQ) 2Cl 2 and Ni(MeQ) 2Cl 2 form intermediate compounds before the metal halide is produced. The compound Cu(MeQ)Cl 2 undergoes decomposition with loss of the 2-methylquinoxaline and the formation of copper(II) chloride, while the compound Zn(MeQ) 2Cl 2 decomposes with loss of the 2-methylquinoxaline and chlorine and the formation of zinc oxide. From the electrical measurements on the compounds isolated from ethanolic solution, it was found that two distinct groups exist: Co(MeQ) 2Cl 2 and Ni(MeQ) 2Cl 2 have nearly equal and relatively high conductivities, whilst Cu(MeQ)Cl 2 and Zn(MeQ) 2Cl 2 have nearly equal but relatively low conductivities. Within each group the temperature dependence of electrical conductivity is similar but it differs between the groups.