1.2- Dithioles tautomerism

The interesting ligand (l)136 has two potential chelating modes upon ionization. Depending on its tautomeric state, either N,S or S,S coordination allows it to act as a bidentate chelating ligand. Apparently, it acts as a 2-aminocyclopent-l-ene-l-carbodithioate, i.e. as a 1,1-dithiolate, to form Mo02L2 complexes.136... 

The effect of added water was also calculated for the five tautomeric forms. The results showed that the spectrum corresponded principally to the dithiol 8 (Figure 1) and monothiols 5-7, which overlap the best of the features enhanced on the spectrum measured at high water content solution. These results suggest that a specific solute-solvent interaction is present favoring the dithiols and monothiols isomers indicating that the hydrogen bond in solute-water is a 1 n complex. 

Figure 22. Structures of the dianionic qdt2 ligand (b) and the dithiol (1) and dithione (2) tautomeric forms of the H2qdt ligand (a).

Low-energy (He 584 A) photoelectron spectra for various members of the heteropentalene family have been reported. The difficulties in assigning the various bands in the spectra to particular molecular orbitals are emphasized. Another theoretical paper discusses the differences between the thiathiophthen system, with an electron-rich three-centre bond favoured by the linear arrangement of the three sulphur atoms, and l,2-dithiole-3-thione derivatives of type (7), in which tautomerism between isomers is observable. ... 

New total syntheses of antibiotic dithioles of the thiolutin, holomycin group, e.g. (15), have been described. Theoretical reasons for the differences between 6a-thiathiophthens (see Chapter 7) and the tautomeric system (16) have been... 

Synthesis.— The condensation of acetonitrile with ethyl thionoformate by means of butyl-lithium has been reported to yield thioformylacetonitrile (1) after subsequent treatment of the intermediate lithium salt (2) with hydrochloric acid. The thioaldehyde could not be isolated, but it was reasonably stable in solution in the tautomeric enethiol form (3), and was characterized as its stable S-methyl derivative (4). Several new, stable thioaldehydes, (5) and (6), have been synthesized by solvolysis of the VUsmeier salts (7) and (8) with aqueous sodium hydrogen sulphide. Some deuteriated analogues of (6) were similarly prepared from the corresponding salts (9). The thioaldehydes (10) were isolated as amorphous solids from the cycloaddition reaction of l,2-dithiole-3-thione with propiolic acid or its... 

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