Mono- and di-nuclear complexes of thiosemicarbazones with copper(I): Synthesis, spectroscopy and structures

Reactions of copper(I) halides with a series of thiosemicarbazones, namely, benzaldehyde thiosemicarbazone (R1R2CN–NH–C(S)–NH2, R1 = Ph, R2 = H; Hbtsc), 2-benzoylpyridine thiosemicarbazone (R1 = Ph, R2 = py; Hbpytsc), and acetone thiosemicarbazone (R1 = R2 = Me; Hactsc), in the presence of PPh3 has formed dimeric complexes, viz. sulfur bridged [Cu2(μ-S-Hbtsc)2Br2(PPh3)2]·2H2O (1), iodo-bridged [Cu2(μ-I)2(η1-S-Hbtsc)2(PPh3)2] (2), and heterobridged [Cu2(μ3-S,N3-Hactsc)(η1-Br)(μ-Br)(PPh3)2] (3), as well as mononuclear complexes [CuX(η1-S-Hbpytsc)(PPh3)2]·CH3CN (X = Br, 4; Cl, 5). Complexes 1, 2, 4 and 5 involve thiosemicarbazone ligands in η1-S bonding mode while in compound 3, ligand acts in N3, S-chelation-cum-S-bridging mode (μ3-S,N3 mode). The intermolecular interactions such as, N2H⋯X, HN1H⋯X (X = S, Br, Cl), CH⋯π interactions lead to 2D networks. All the complexes have been characterized with the help of elemental analyses, IR, 1H, and 31P NMR spectroscopy, and single crystal X-ray crystallography. The role of a solvent in alteration of nuclearity and bonding modes of complexes has been highlighted.

Graphical abstractCopper(I) iodide with benzaldehyde thiosemicarbazone in CH3CN–CHCl3 mixture yielded a dinuclear complex 1 unlike mononuclear complex in CH3CN alone.Figure optionsDownload full-size imageDownload as PowerPoint slide