Some theoretical and practical problems in the use of organic reagents in chemical analysis—IV: Infra-red and ultra-violet spectrophotometric study of the dimethylglyoxime complexes of transition metals

Abstract

The dimethylglyoxime complexes of iron (II), iron (III), cobalt (II), cobalt (III), copper (II), nickel (II), palladium (II) and platinum (II) were prepared and their composition was established by elementary analysis (Table 1). The presence of the Me → N = C donor π-bond was proved in the dimethylglyoxime complexes of bivalent metals by infrared spectrophotometry (by the shift of the CN-frequency). It was found that the effect of the donor π bond increases in the order Cu II < Ni II < Co II < Fe II, and Ni II < Pd II < Pt II. From the character of the OH bands of the infra-red spectra, conclusions can be drawn about the nature and strength of the hydrogen bridges in the complexes. Investigations by ultra-violet spectrophotometry disclosed that in an alkaline solution the absorption band of undissociated dimethylglyoxime (HDMG) splits into two bands. The character of the ultraviolet spectrum of the dimethylglyoxime complexes in aqueous solution is quite identical with that of the spectrum of the dimethylglyoximate anion (DMG −).