Metal derivatives of heterocyclic-2-thiones: Variable donor ability, C-S rupture and new structural motifs

Abstract

The chemistry of thio-ligands based on heterocyclic-2-thiones, namely, pyridine-2-thione (SNC5H5), imidazolidine-2-thione (SN2C3H6), imidazoline-2-thione (SN 2C3H4), 1-methyl-imidazoline-2-thione (SN 2C4H6) and thiazolidine-2-thione (S 2NC3H5) with coinage and some other metals are described. The synthesis, solvent effect, isolation of new products after C-S rupture and crystal structure are also discussed. For example, copper(I) bromide with 1-methyl-imidazoline-2-thione (SN2C4H6) in acetonitrile formed Cu I trinuclear complex, {Cu (κI -Br)3(μ-SN2C4H 6)3}·CH3CN. This reaction in the presence of chloroform involved C-S bond rupture, oxidation of sulphur to sulphate and bromination of ring and formed a tetranuclear cluster, Cu 4(κ1 -N-(N2C4H 5Br)4(μ 4-O)(μ-Br)6] (N 2C4H5Br = 2-bromo-1-methyl-imidazole). The reaction of copper(I) chloride with 1-methyl-imidazoline-2-thione (SN 2C4H6) in acetonitrile also involved C-S rup ture and formed a chloro-bridged dinuclear complex [Cu2{κ 2-N,N-(N2C4H5)2S} 2(μ-Cl)2Cl2] {(N2C 4H5)2S = 1, 1′-dimethyl-2, 2′-di-imidazolyl sulphide}. Significantly copper(I) bonded to more polarisable iodide ion (Cu-I) does not involve C-S rupture and in this case it formed Cu I polynuclear complex, {Cu2(μ-I) 2(μ-SN2C4H6)2} n. Both copper(I) chloride and copper(I) bromide with 1-methyl-imidazoline-2-thione in dimethyl sulphoxide involved C-S rupture and oxidation of sulphur to sulphate and formed a sulphate chelated Cu II complex, [Cu II{κ 2-N,N-(N2C 4H5)2S}(η 2-O,OSO (κ1 -OH2)]. Imidazolidine-2-thione (SN 2C3H6) with copper(I) chloride/bromide in dimethyl sulphoxide gave a sulphate bridged polynuclear complex, [Cu II {κ 2-N,N-(N2C3H 5)2S}(μ-O,OSO2(κ1 -OH 2)]n {(N2C3H5) 2S = 2,2′-thio-di-2-imidazoline}. Other metals such as silver, zinc, cadmium and mercury formed monomers or dimers. © 2012 Indian Academy of Sciences.