Interactions between sodium dithiocarbamates and p- and d-block metals

Abstract

Working on the problem of the interactions between p- and d-block metals and dithiocarbamate sodium salts as ligands, we report in this study the derivatives of Cr(III), Mn(III), Pb(II), Sn(II), Os(II) and Os(III) with ▪ We have previously described the complexes of many transition metals with the above dithiocarbamates, derivatives of iridium phosphine and arsine hydrides, and monohalobisdithiocarbamate iron(III), antimony(III) and bismuth(III) derivatives [1]. This paper is an extension of the previously reported studies on the dithiocarbamates in which dialkyl groups are replaced by heterocycles. It is of interest to study the influence of the different heterocyclic groups on the CN and CS bands and, consequently, on the electronic structure of the complexes. The nature of the heterocycle is important in the behaviour of the dithiocarbamates as ligands owing to the variation in the electron releasing ability of the different amines. The compounds are microcrystalline, soluble in N, N′-dimethylformamide (DMF) and non-conducting in this solvent. Our manganese(III) derivatives have a μ value in the 4.8–4.9 B.M. range and these values are typical of high-spin complexes. These trisdithiocarbamates can be readily prepared by aerial oxidation of the suspension produced when aqueous or aqueous-ethanolic solutions are mixed. However a recrystallization under nitrogen is necessary to prevent aerial decomposition. The thioureide band near 1500 cm −1 indicates considerable double bond character in CN bond. This fact could be ascribed to the electron releasing ability of the heterocyclic group, which forces high electron density towards the sulphur atoms, via the π system, thus producing greater double-bond character in the carbonnitrogen bond, and shifting v(CN) to higher energies. The band attributed to the prevailing contribution of v(CS) is indicative of a bidentate behaviour of the dithio-ligands and this fact is confirmed by the blue shift of the v(CN) mode. The v(CN) band undergoes a blue shift greater in the chromium(III), manganese(III), osmium(III) and osmium(II) derivatives than in the tin(II) and lead(II) complexes. This behaviour could be explained by considering either the different stereochemistries of the complexes or the fact that the three first metals are of the d-block, while the last two belong to the p-block. Perhaps because of the rigid heterocyclic ring system, which shows less tendency to release electrons to the carbonnitrogen bond, this bond has a less double-bond character; this tendency to release electrons is less in the p-block metal derivatives than in the d-block ones. The electronic spectra have been studied and will be discussed in detail. The room temperature magnetic moment values for Cr(III), Mn(III) and Os(III) derivatives are in agreement with the literature data; all the remaining complexes of Pb(II), Sn(II) and Os(II) are diamagnetic.