Thiocarbonyl compounds spectroscopy

Thiocarbonyl compounds can be generated thermally in the gas-phase from a variety of precursors. Bock et al. [77JCS(CC)287 82CB492] have shown that pyrolysis of 1,2,4-trithiolane derivatives (81) is especially advantageous for this purpose. The fragmentation reactions were monitored by PE spectroscopy. By this method thioaldehydes including thioformaldehyde and thioketones that polymerize readily were obtained. 1,2,4-Trithiolane 4-oxide (82) yields a mixture of thioformaldehyde and thioformaldehyde oxide. 

Physical Properties of Thiazolidines.—An investigation of the charge distribution in a series of N-alkylated thioureas and related thiocarbonyl compounds (including thiazolidinethiones), using X-ray photoelectron spectroscopy, has been described.Population analysis, which refines the population of the electrons in a molecule, has been carried out on R-thiazolidine-4-carboxylic acid, and the results were compared with theoretical calculations.A stereochemical analysis of 2-aryl-3-(2-pyridyl)-thiazolidin-4-ones, using H n.m.r. and i.r. spectroscopies, has been reported," and these techniques also give information on the tautomeric equilibrium of some 2-arylamino-thiazolidines. ... 

Compared to the classes of compounds considered in the two preceding sections, relatively few simple thiocarbonyl compounds have been investigated by PE spectroscopy. This is mainly due to the relative instability of many of these species. 

An example of thione coordination is demonstrated with the thiocarbonyl donor ligand 2,6-dimethyl-4H-pyran-4-thione, that gives a complex with zinc chloride of the form ZnL2Cl2-The crystal structure shows the zinc is tetrahedrally coordinated by two chloride and two sulfur donors and the compound was further studied by 3H NMR and IR spectroscopy.573 Both monomeric and dimeric heterocyclic thione complexes have been formed with zinc.5 4,575... 

The preparative reduction, polarography, and cyclic voltammetry of 5-methyl-l,2-dithiole-3-thione have been studied.171 The results obtained are in agreement with a one-electron reduction of the thiocarbonyl group to a radical-anion, which could not be detected by ESR spectroscopy as it dimerizes too fast. The dimer is further reduced by a one-electron reduction to an anion in which the ring has been opened. (Scheme 12). The dianion could be isolated after methylation and was found to be identical with the compounds isolated by Maignan and Vialle by reduction with sodium sulfide.124 The dianion corresponds to the thioketonate dianion obtained by electrochemical reduction of 1,2-dithiolylium salts.172... 

The photoelectron spectroscopy of organic sulfur compounds was reviewed in detail by Gleiter and Spanget-Larsen in 19796. At that time most of the published work in this area involved compounds of divalent sulfur, particularly those in which sulfur is bonded to one or two carbon atoms. Consequently, the review was confined to the cases of saturated sulfides, unsaturated sulfides and thiocarbonyls, though some polyvalent sulfur compounds were included. 

Molecular rotation in the cavity has been discussed for many compounds using nmr(8,9), esr(lO) and Mossbauer spectroscopy(4,5). A complete description of the Mossbauer spectrum for such a case has been given by Gibb(4) for that of the 3 1 clathrate of thiocarbonyl diamide and bis( -cyclopentadienyl)iron(II). Evidence for conformational isomerism has been presented recently based on the ir spectra of y-cyclopentadienylmetal carbonyl complexes such as CpFe(CO) SiCl Me(ll), ip -MeC H Mn(CO) (P(OMe) )(12) and others(13), and on the Mossbauer... 

Spectroscopy.—Photoelectron spectroscopy and electronic absorption and emission spectra indicate that there exists a strong interaction between the two thiocarbonyl groups in (73), whereas the carbonyl and thiocarbonyl groups in (74) interact only weakly. U.v., i.r., and C n.m.r. spectra have been reported for compounds (28)—(31). The relative stabilities of tautomers of ) -thioxoketones have been studied on the basis of u.v. and n.m.r. spectroscopies and of molecular orbital calculations. It is concluded that when the thioxoketone is substituted by at least one vinyl group, the enol form is more stable than the enethiol form, whereas methyl and/or phenyl substituents stabilize the enethiol form more than the enol form. E.s.r. spectroscopy has revealed that thiobenzoylphenylmethylene has the triplet biradical structure (75) and that the carbon-carbon bond in (75) has greater double-bond character than the carbon-sulphur bond. ... 

Photoelectron and E.S.C.A. Spectra. The diselenide structure of thiuram diselenides has been established by means of Rdntgenphotoelectron spectroscopy. The photoelectron spectra of thiocarbonyl halides have been studied and interpreted on the basis of CNDO calculations by two groups of workers. ESCA investigations have been performed on dithio-esters derived from active-methylene compounds and carbon disulphide, and on isocoumarins, thioisocoumarins, and isoquinolines containing the thiocarbonyl function." ... 

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