FULL PAPER DOI:10.1002/ejic.201300676 Chemistry of Heterocyclic 2-Thiones: In Situ Generation of 3-(2-Thiazolin-2-yl)thiazolidine-2-thione and 1,1'- Dimethyl-2,2'-diimidazolyl Sulfide and Their Coordination to Cu I and Cu II Tarlok S. Lobana,* [a] Razia Sultana, [a] Ray J. Butcher, [b] Alfonso Castineiras, [c] Takashiro Akitsu, [d] Francisco J. Fernandez, [e] and M. Cristina Vega [e] Keywords: Cleavage reactions / Copper / S ligands / Sulfur heterocycles / N ligands The chemical reactivity of copper(I) chloride/copper(I) brom- ide, [Cu I (NCCH 3 ) 4 ](BF 4 ), and copper(II) nitrate towards a series of heterocyclic-2-thiones under aerobic conditions is described. Thiazolidine-2-thione (NC 3 H 5 S 2 ) in CH 3 CN in the presence of copper(I) chloride/bromide and [Cu I (NCCH 3 ) 4 ]- (BF 4 ) was transformed into 3-(2-thiazolin-2-yl)thiazolidine-2- thione (C 3 H 4 S 2 N-C 3 H 4 SN) through C–S bond cleavage and the formation of a C–N bond between two heterocyclic rings. This new thio ligand (C 3 H 4 S 2 N-C 3 H 4 SN) chelates to Cu I through N,S-donor atoms, and the third site is occupied by the halogen atoms (Cl, Br), which leads to the formation of three-coordinate Cu I complexes, [Cu I X(κ 2 -N,S-C 3 H 4 S 2 N- C 3 H 4 SN)] [X = Cl (1), Br (2)], and a four-coordinate N,S-che- lated complex, [Cu I (κ 2 -N,S-C 3 H 4 S 2 N-C 3 H 4 SN) 2 ](BF 4 )(3), is obtained in the presence of BF 4 – . In each case, the formation of CuSO 4 ·5H 2 O was also observed. Upon reaction of 1-methyl- Introduction Sulfur-containing ligands such as heterocyclic thioam- ides or closely related ligands bearing the –N(H)C(=S)– ↔ – N=C(–SH)– or –N(H)C(=S)–N(H)– ↔ –N=C(–SH)–N(H)– functional groups have shown interaction with a wide range of metals owing to the presence of both nitrogen (hard) and sulfur (soft) donor atoms, and thus, these thio ligands have [a] Department of Chemistry, Guru Nanak Dev University, Amritsar, 143 005, India E-mail: tarlokslobana@yahoo.co.in Homepage: www.gndu.ac.in [b] Department of Chemistry, Howard University, Washington DC 20059, USA [c] Departamento De Quimica Inorganica, Facultad de Farmacia, Universidad de Santiago, 15782- Santiago, Spain [d] Department of Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku-Ku, Tokyo 162-8601, Japan [e] Department of Structural and Quantitative Biology, Center for Biological Research (CIBeCSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejic.201300676. Eur. J. Inorg. Chem. 2013, 5161–5170 © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 5161 imidazoline-2-thione (N 2 C 4 H 6 S) with [Cu I (NCCH 3 ) 4 ](BF 4 ) or copper(II) nitrate in CH 3 CN or CH 3 CN/MeOH, respec- tively, the thio ligand is converted into 1,1'-dimethyl-2,2'-di- imidazolyl sulfide (N 2 C 4 H 5 ) 2 S (a thioether), which prefers to bind to Cu II (in situ formed) to yield six-coordinate N,N-che- lated octahedral complexes, namely, {Cu II [κ 2 -N,N-(N 2 C 4 H 5 ) 2 - S] 2 (κ 1 -OH 2 ) 2 }X 2 [X = BF 4 (6), NO 3 (7)], with water in the axial positions. The transformation of the thio ligand into 1,1'-di- methyl-2,2'-diimidazolyl sulfide is also observed in its cop- per(I) chloride reaction in acetonitrile, which yields an N,N- chelated chloro-bridged dimer, {Cu II 2 [κ 2 -N,N-(N 2 C 4 H 5 ) 2 S] 2 - (μ-Cl) 2 Cl 2 }(5). Reaction of copper(I) iodide with thiazolidine- 2-thione and 1-methylimidazolidine-2-thione (N 2 C 4 H 8 S) in acetonitrile yields an iodo-bridged dimer, [Cu 2 (κ 1 -S- NC 3 H 5 S 2 ) 4 (μ-I) 2 ](4), and a novel polymer, [Cu 4 (μ 3 -I) 2 (μ-I) 2 (μ- S-N 2 C 4 H 8 S) 2 (κ 1 -S-N 2 C 4 H 8 S)] n (8), respectively. exhibited variable bonding modes in neutral and anionic forms, which has led to the formation of mono-, di-, tri-, and polynuclear complexes. [1] In addition to the diversity of metal–ligand interactions, the above ligands have caught the attention of many workers as a result of their applica- tions as biomimics in biological systems, [2] as fungicides, [2,3] as electric conductors, [4] in the pharmaceuticals industry, [5] as anticancer agents, [6] and in catalysis. [1] During our studies of the chemistry of copper(I) halides in reactions with heterocyclic-2-thioamides (Scheme 1), it was found that variation of the reaction conditions, includ- ing solvent and ratio of reactants, produced different types of products. [7–10] During the course of these reactions, C–S bond cleavage was observed upon treatment of copper(I) bromide with 1-methylimidazoline-2-thione (N 2 C 4 H 6 S, II) and upon treatment of copper(I) chloride/bromide with imidazolidine-2-thione (N 2 C 3 H 6 S, III) [11] in DMSO. Ad- ditionally, the reaction of thio ligand II with copper(I) bromide in acetonitrile/chloroform also involved C–S bond cleavage with subsequent conversion of II into 2-bromo-1- methylimidazole (N 2 C 4 H 5 Br). [12] In the literature, cleavage