Synthesis and characterization of thiosemicarbazone derivatives of 2-chloro-4-hydroxy-benzaldehyde and their rhenium(I) complexes

N-Thioamide thiosemicarbazone derived of 2-chloro-4-hydroxy-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 chloroform gave the adducts [ReX(CO)3(HL)] (1a X = Cl, R = H; 1a′ X = Br, R = H; 1b X = Cl, R = CH3; 1b′ X = Br, R = CH3; 1c X = Cl, R = Ph; 1c′ X = Br, R = Ph) in good yield. Complexes 1a′ and 1b’ were also obtained by the reaction of HL1 and HL3 with [ReBr(CO)5] in toluene.All the compounds have been characterized by elemental analysis, mass spectrometry (FAB), IR and 1H NMR spectroscopic methods. Moreover, the structures of HL2, HL3 and 1a·H2O were also established by X-ray diffraction. In 1a, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms, forming a five-membered chelate ring, as well as three carbonyl carbon and chloride atoms. The resulting coordination polyhedron can be described as a distorted octahedron.The study of the crystals obtained by slow evaporation of methanol and DMSO solutions of the adducts 1a′ and 1b, respectively, showed the formation of dimer structures based on rhenium(I) thiosemicarbazonates [Re2(L1)2(CO)6]·3H2O (2a)·3H2O and [Re2(L2)2(CO)6]·(CH3)2SO (2b)·2(CH3)2SO. Amounts of these thiosemicarbazonate complexes [Re2(L)2(CO)6] (2) were obtained by reaction of the corresponding free ligands with [ReCl(CO)5] in dry toluene.In 2a·3H2O and 2b·2(CH3)2SO the dimer structures are established by Re–S–Re bridges, where S is the thiolate sulphur from a N,S-bidentate thiosemicarbazonate ligand. In both structures the rhenium coordination sphere is similar; the dimers are in the same diamond Re2S2 face.

Graphical abstractN-Thioamide thiosemicarbazone derived of 2-chloro-4-hydroxy-benzaldehyde have been prepared and their reaction with fac-[ReX(CO)3(CH3CN)2] (X = Br, Cl) in chloroform gave the adducts [ReX(CO)3(HL)] (1) in good yield. The study of the crystals obtained from solutions of some adducts 1 showed the formation of dimer structures based on rhenium(I) thiosemicarbazonates [Re2(L)2(CO)6] (2). Amounts of 2 were obtained by reaction of the corresponding free ligands with [ReCl(CO)5] in dry toluene. The dimer structures are established by Re–S–Re bridges, where S is the thiolate sulphur from a N,S-bidentate thiosemicarbazonate ligand.Figure optionsDownload full-size imageDownload as PowerPoint slide