Exocyclic Sulfur Atom Research Articles

Metal complexes of 2-mercaptobenzothiazole

Metal complexes of 2-mercaptobenzothiazole (LH) have been prepared and investigated. The metal complexes obtained were of the types ML2 (M = Ni, Pd, Pt, Zn, Cd), CuL.LH, and AgL. The copper complex has been shown to contain copper(I). Evidence from the i.r. spectra shows that in all the complexes the ligand is coordinatedvia the thiazole nitrogen and the exocyclic sulfur atom. Adducts of both the nickel and cadmium complexes were obtained with several nitrogen heterocycles. The complex CdL2py2 (py = pyridine) is isostructural with the six-coordinate NiL2py2 and CoL2py2 which possess acis configuration.

Studies on mesoionic compounds. Part 4. Protonation equilibria of 2,3-diaryl-2H-tetrazolium-5-thiolates and 1,3,4-thiadiazolium-2-thiolates in aqueous perchloric acid solutions

The pKBH+ values of five 2,3-diaryl-2H-tetrazolium-5-thiolate and six 1,3,4-thiadiazolium-2-thiolate mesoionic compounds were determined spectrophotometrically in aqueous perchloric acid solutions at 15, 25, 35, and 45 °C. Our results have shown that both types of mesoionic compounds behave as Hammett bases and that protonation was suggested to occur at the exocyclic sulphur atom. The thermodynamic functions (ΔG°, ΔH°, and ΔS°) of ionization have been determined and are discussed.

Complexes of imidazoline (1,3H)-2-thione with Co(II) and Zn(II) salts

Complexes of imidazoline-2(1,3H)-thione ( ImT,L), have been prepared with Co(II) and Zn(II) salts. Stoichiometries of the complexes, ML 2X 2, for the halides and ML 4X 2 for the nitrates and perchlorates, have been established by chemical analysis. Thermal analysis has revealed the extent of hydration among the cobalt complexes. The solid complexes have been further characterised by means of magnetic susceptibility data, infrared and visible spectral measurements. The soluble complexes have been studied by means of electrolytic conductance measurements and their visible spectra have also been recorded. Ligand field parameters have been determined and probable structures assigned. The ligand coordinated by means of its exocyclic sulphur atom and one of its ring nitrogen atoms in the solid complexes. For the soluble complexes coordination involves the sulphur atom only.

Tin (IV) Halides and Germanium (IV) Chloride Complexes of Sulphur and Nitrogen Containing Ligands

Abstract The complexes of 2,5-dimercapto-1, 5-dimercapto-1, 3, 4-thiadiazole (bismuthiol I, BT), 2-aminothiazole (AT) and 2-amino-6-ethoxybenzothiazole (AEB) with SnCl4, SnBr4 and GeCl4 (except Ge(BT)2Cl4), have been synthesised and characterized by elemental analysis, conductance measurements and I.R. spectroscopy. All the complexes have a 1:2 (M:L) stoichiometry and are non-ionic in acetone solution. Bismuthiol I has been found to coordinate through the exocyclic sulphur atom at position 2 or 5, whereas in the case of AT and AEB coordination occurs through the amino nitrogen. An octahedral trans configuration has been proposed for these adducts.

Derivatives of 3H-1,2,3-triazolo[4,5-d][1,3]thiazine, a new heterocyclic nucleus. Some shifts of a methylene group from a nitrogen to a sulphur atom

Contrary to expectations, 3-alkyl derivatives of 4-amino-5-aminomethyl-3H-1,2,3-triazole (2b and c), when heated with carbon disulphide and a base, did not give a 1,3,6,9-tetrahydro-8-azapurine-2-thione (3b) but a 3-alkyl-3,7-dihydro-1,2,3-triazolo[4,5-d][1,3]thiazine-5(4H)-thione, e.g. (5). This thione (5), the nucleus of which was hitherto unknown, could be methylated on the exocyclic sulphur atom to give the methylthio-derivative (6a), which was readily converted into the amino- and hydrazine-analogues (6b and c). The reaction mechanism that produced the thione (5) depends on the transfer of a 5-methylene group from a nitrogen to a sulphur atom, apparently involving triazol-5-lmethyldithiocarbamate intermediates [(4)→(8)]. Two sulphide by-products (9) and (11) were isolated which had also undergone this very unusual N → S shift. 1H N.m.r., i.r., and mass spectrometric data are presented and discussed.

Complexes of 9-methyl-6-mercaptopurine with some divalent metal ions

The preparations and spectral properties are reported of some complexes formed by 9-methyl-6-mercaptopurine (9 MeMP) and divalent Co, Ni, Cu, Cd and Hg. The involvement of the exocyclic sulphur atom of the purine ligand is much greater than that of O6 in 9-methylhypoxanthine and examples of 9MeMP chelating via N7 and S are reported, as well as compounds in which the ligand binds by N7 or S alone.

An X-Ray Photoelectron Spectroscopic Study of 2-Mercaptobenzothiazole Metal Complexes

Abstract The X-ray photoelectronic spectra of 2-mercaptobenzothiazole (LH) and its metal complexes have been measured. On the basis of the chemical shifts of the N(1s), S(2p), and Cu(2p3⁄2) electron binding energies, the coordination mode of the ligand and the oxidation state of the copper atom have been examined. It is suggested that, in HgL2, PbL2, AgL, and CuL3H2Cl complexes, the ligand is solely coordinated through the exocyclic sulfur atom, and that, in CuL, CuL2, PtL2, PdL2, NiL2, and CdL2 complexes, the ligand is coordinated through both the exocyclic sulfur and nitrogen atoms. In CuL2 and CuL3H2Cl, it was found that the copper was present in a (+1) oxidation state, and that part of the ligand molecules, bis(benzothiazol-2-yl) disulfide, resulted from oxidation of LH by the Cu2+ ion on complex formation.

Addition reactions of thiazol-5(4H)-ones—IV : Synthesis, tautomerism and addition reactions of 2-phenylthiazole-5-thiols

4-Substituted 2-phenylthiazole-5-thiols 3 undergo addition reactions of a different type from those of their oxygen analogues, the oxazol- and thiazol-5(4 H )-ones, since they exist in solution entirely in the thioenol tautomeric form. Their addition reactions involve only the exocyclic sulphur atom, and they behave as typical heteroaromatic thiols towards unsaturated systems, giving sulphides. A mesoionic thiazole-5-thiol, however, is shown to possess cycloaddition reactivity, undergoing cycloaddition-extrusion reactions with unsaturated systems comparable with well-established reactions of oxygen analogues.

Stéréoisomérie de sulfures insaturés en série pyrazoline‐, isoxazoline‐ et oxazoline‐5‐ones

AbstractThe stereoisomerism of 39 4,1'‐alkyl(aryl)thioalkyl(aryl)idenepyrazolin‐, isoxazolin‐ and oxazolin‐5‐ones in various solvents has been investigated by NMR spectroscopy. The exocyclic sulfur atom induces the interconversion of the two stereoisomers exo Z and exo E. The part played by the solvent and the steric interactions in the equilibrium composition is discussed.

The Reaction of 3H-1,2-Benzodithiole-3-thione with Diphenyldiazomethane

Abstract 3H-1,2-Benzodithiole-3-thione (35S=C<) reacted with diphenyldiazomethane in the presence of copper-(II) acetylacetonate to afford the corresponding 4,5-benzo-3-diphenylmethylene-1,2-dithiole with a predominant extrusion of the exocyclic sulfur atom, while with its selenium analog the exclusive loss of in-ring sulfur was observed, resulting in the formation of the selenium-migrated 4,5-benzo-3-di-phenylmethylene-1,2-thiaselenole.

The crystal and molecular structure of dehydrodithizone

The structure of the orange oxidation product of dithizone has been determined by X-ray analysis and shown to be dehydrodithizone, a tetrazole ring system with two phenyl groups substituted in the 2- and 3-positions and an exocyclic sulphur atom in the 5-position.

Condensation of rhodanine with?-dicarbonyl compounds

Reaction of acetylacetone with rhodanine in ethanol solution, in the presence of ammonia and ammonium chloride gives two condensation products, containing one or two rhodanine groups. Under the same conditions benzoylacetone condenses with one molecule of rhodanine. Methylation of these compounds with methyl iodide takes place at an exocyclic sulfur atom, to give mono- and dimethylmercapto derivatives. The condensation products from the above carbonyl compounds and rhodanine have an active methylene group which can react with nitroso compounds and diazonium salts.

Electronic structures and dipole moments of 4- and 5-phenyl-1, 2-dithiol-3-thiones

The simple LCAO MO method is used to calculate π-electron configurations of 1,2-dithiol-3-thione and its 4- and 5-phenyl derivatives. In these compounds the heterocyclic ring has an aromatic character, but the S-S bond is almost excluded from conjugation. The phenyl group in 4-phenyl-1,2-dithiol-3-thione is an electron acceptor, whereas in the 5 isomer it is an electron donor. The exocyclic sulfur atom has considerable negative charge, while the two endocyclic ones are positively charged. The dipole moments of 4- and 5-phenyl-1,2-dithiol-3-thione are determined, and the values found are compared with the calculated ones.