Reactivity of Thiosemicarbazides with Redox Active Metal Ions: Controlled Formation of Coordination Complexes versus Heterocyclic Compounds

Abstract

The reactions of 1,1-dimethyl-4-phenylthiosemicarbazide (LH) with Cu(II) and Sn(IV) have been investigated. If THF or methanol is used as solvent with Cu(II), oxidative cyclisation and coupling are observed, yielding a 1,2,4-thiadiazole or a 1,3,4-thiadiazolium salt. SnI(4) is also able to induce oxidative coupling of two thiosemicarbazide ligands, yielding 1,2,4-thiadiazolium or 1,2,4-triazolium salts, with I(3)(-) as the counterion, depending on the reaction conditions. By contrast, reaction of LH with SnI(4) in acetone yields a 1,3-thiazolium salt, with I(-) as counterion. Reaction with Cu(II) salts or SnI(4) in basic media leads to the formation of metal complexes containing two deprotonated thiosemicarbazide ligands. In the reaction of CuCl(2) in water in the presence of acid a complex containing two neutral ligands is obtained. Reactions with SnCl(4) are not able to induce ligand cyclisation, although a coordination compound with two neutral ligands was isolated from methanol.

Crystal structure of 1-(4-chlorophenyl)-3-[methyl(phenyl)amino]thiourea, C14H14ClN3S

“…The twist in the molecule is confirmed by the dihedral angle between the phenyl rings of 71.07(4)°. As for the literature structures [5,6] The structure of the present compound is isostructural with the 4-Me analogue [6]. As anticipated, equivalent intermolecular interactions are present in both crystals with the additional C5-Cl1• • • π(phenyl-C2-C7) contact obviously lacking in the 4-Me structure.…”

“…Recent structural studies of molecules of the general formula Me(R)NN(H)C(=S)N(H)(PhY-4) have revealed a high degree of homogeneity in terms of the adopted molecular geometry and in the formation of supramolecular synthons of the type {• • • HNCS} 2 owing to the syn disposition of the thione-S and thioamide-N-H atoms [5,6]. The main motivations for investigating such di-substituted thiourea derivatives comes about owing to their utility in asymmetric synthesis as dual hydrogen bonding catalysis [7] and their pharmaceutical potential [8].…”

1-[N-Methyl-N-(Phenyl)amino]-3-(4-Methylphenyl)Thiourea

“…There is a closely related structure in the literature where the N-bound phenyl group of (1) is substituted by a methyl group and the original 4-tolyl ring is now a phenyl ring, that is, Me2NN(H)C(=S)N(H)Ph (2) [7]. Molecule (2) adopts essentially the same conformation as just In the crystal of (1), the most prominent feature of the molecular packing is the formation of thioamide-N1-H• • • S1(thione) hydrogen bonds.…”

“…The melting point was determined on a Biobase automatic melting point apparatus MP450 (Biobase Group, Jinan, Shandong Province, China). The IR spectrum was measured There is a closely related structure in the literature where the N-bound phenyl group of (1) is substituted by a methyl group and the original 4-tolyl ring is now a phenyl ring, that is, Me 2 NN(H)C(=S)N(H)Ph (2) [7]. Molecule (2) adopts essentially the same conformation as just described for (1) but, some systematic changes in the key bond lengths are evident.…”

Structural peculiarities of the [(2-amino-5-ethyl-1,3,4-thiadiazole)CuCl] complex

“…[1][2][3][4][5]), as well as owing to their unique role in self-organization of potential metalorganic complexes through coordination to different transition metal ions [6][7][8][9][10][11]. For example, 2-amino-1,3,4-thiadiazole easily undergoes a transition-metalinduced reductive coupling reaction with acetonitrile, resulting in Co(III) amidine complexes [6], while the bis(5-anilino-3-methyl-1,3,4-thiadiazol-3-ium) tetrachlorocuprate(II) salt has been prepared in a good yield by a Cu(II)-induced reaction of a thiosemicarbazide precursor (PhNHCSNHNMe 2 ) with CuCl 2 [11]. Despite the considerable interest in 1,3,4-thiadiazole derivatives, the research area of their complexation with copper halides is still rather poorly covered and the only hitherto synthesized and X-ray studied copper(I) chloride complex is [Cu(L2)Cl] (2) (L2 = 2-amino-5-methyl-1,3,4-thiadiazole) [12].…”