1.2.4.6- Thiatriazinyls

In contrast to the ring folding observed in 1,5-(R2P)2N482, the 7t -7i interaction in [8204] is an intermolecular process involving the association of two species. An analogy in inorganic heterocycles Is provided by the thiatriazinyl... 

UV-PES studies of 1,2,4,6-thiatriazinyl [R2C2N3S] and 1,2,3,5-dithidiazolyl [RCN2S2] (15) radicals have also provided ionization potentials that are in good agreement with modified neglect of differential overlap (MNDO) calculations. " ... 

The thiatriazinyl system (43), prepared by the reduction of the corresponding S-chloro derivative, is also a In-electron radical. In the solid state, it exists as a cofacial dimer with an S-S distance of ca. 2.67 A. In solution, the ESR spectrum of (43) gives a seven-line pattern with equal hyperfine coupling constants to all three nitrogen atoms. 

Thiatriazinyl radicals have been generated in the gas phase and studied by helium ionization photoclectron spectroscopy. Ionization potential and hyperfine coupling constant data for these radical systems have been analyzed in relation to the results of MINDO calculations and their electronic structure. 

Using sulfuryl chloride, oxidative chlorination of 3,5-diphenyl-4//-l,2,4,6-thiatriazine gives 1-chlorothiatriazine 4.47 The same procedure gives 4 in 8% yield by reaction of sulfuryl chloride with the dimer bis(3,5-diphenyl-l,2,4,6-thiatriazinyl)48... 

Thiatriazinium salts 2, 4 and 6 are stable compounds, extremely sensitive to moisture. In general, the most stable salts arc obtained in the form of ion pairs with complex anions. 1-Halo-substituted thiatriazines 3 and 526 or thiatriazinyl radicals or their precursors,49,61 67,68 e.g. dimer 1, can be converted into the corresponding thiatriazinium salts. 

A slurry of the dimer bis(3,5-diphenyl-1 24,2,4,6-thiatriazinyl) (1 0.365 g, 0.723 mmol) and NOBF4 (0.19 g, 1.63 mmol) in MeCN (25 mL) was stirred and heated at reflux for 2 h to give a clcar-red solution from which orange-red crystals precipitated on cooling. The extremely moisture-sensitive crystals were collected by filtration under dry N2 yield 0.235 g (48%) mp >230°C (dec.). 

The crystal structure of the thiatriazinyl radical dimer is triclinic, space group PI <85JA1346>. 

Chloro-1,2,4,6-thiatriazines (16) readily form the thiatriazinyl radical, for example, on treatment with triphenylantimony. These radicals associate in the solid state to form cofacial dimers (80JOU1303, 85JA1346>. Persistent thiatriazinyl radicals have also been produced by treating chlorothiatriazines with sodium or with triphenylverdazyl (83SUL143>. 

FIGURE 25. Photoelectron spectra of l,3,5-trichloro-l,2,4,6-thiatriazine and its reduction product 3,5-dichloro-l,2,4,6-thiatriazinyl. Reprinted with permission from Reference 66. Copyright (1989) American Chemical Society... 

Gas-phase electron-transfer processes for the 1,2,4,6-thiatriazinyl radicals 13 were investigated using the Hartree-Fock (HF) and B3LYP methods with the 6-31G(d) basis set augmented with diffuse functions. The calculated... 

Keywords Benzotriazinyls Dithiadiazolyls Dithiazolyls Heterocyclic radicals Hydrazyls Thiadiazinyls Thiatriazinyls Thiazyls Verdazyls... 

Thiatriazinyls 89, 93, and the 3,5-dithien-2-yl analogue form diffuse vr —7T cofacial dimers in the crystalline solid state hnked with S---S contacts of 2.6 A suggesting dimeric species that are intermediate between 7T- and n-bonded dimec (2011IC5123, 2015CGD2524). 

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