Synthesis, characterization, reactivity and computational studies of new rhenium(I) complexes with thiosemicarbazone ligands derived from 4-(methylthio)benzaldehyde

N-thioamide thiosemicarbazone derived from 4-(methylthio)benzaldehyde (R = H, HL1; R = Me, HL2 and R = Ph, HL3) have been prepared and their reaction with fac-[ReX(CO)(3)(CH3CN)(2)] (X = Br, Cl) in methanol gave the adducts [ReX(CO)(3)(HLn)] (1a X = Cl, n = 1; 1a' X = Br, n = 1; 1b X = Cl, n = 2; 1b X = Br, n = 2; 1c X = Cl, n = 3; 1c' X = Br, n = 3) in good yield. All the compounds have been characterized by elemental analysis, mass spectrometry (ESI), IR and H-1 NMR spectroscopic methods. Moreover, the structures of HL2, HL3, HL3(CH3)(2)SO and 1b'center dot H2O were also elucidated by X-ray diffraction. In 1b', the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms (kappa S,N-3) forming a five-membered chelate ring, as well as three carbonyl and bromide ligands. The resulting coordination polyhedron can be described as a distorted octahedron. The structure of the dimers is based on rhenium(I) thiosemicarbazonates [Re-2(L-1)(2)(CO)(6)] (2a), [Re-2(L-2)(2)(CO)(6)] (2b) and [Re-2(L-3)(2)(CO)(6)] (2c) as determined by X-ray studies. Methods of synthesis were optimized to obtain amounts of these thiosemicarbazonate complexes. In these compounds the dimer structures are achieved by Re-S-Re bridges, where S is the thiolate sulphur from a kappa S,N-3-bidentate thiosemicarbazonate ligand. Some single crystals isolated in the synthesis of 2b contain [Re(L-4)(L-2)(CO)(3)] (3b) where L-4 (=2-methyl-amine-5-(para-methylsulfanephenyl)-1,3,4-thiadiazole) is originated in a cyclization process of the thiosemicarbazone. Furthermore, the rhenium atom is coordinate by the sulphur and the thioamidic nitrogen of the thiosemicarbazonate (kappa S,N-2) affording a four-membered chelate ring. (C) 2011 Elsevier Ltd. All rights reserved.