1,2-Dithiolan cation-radical

A similar cycloreversion in 1,2-dithiolan cation-radical was used to prepare CH2S2 ions which were reduced with Xe to generate elusive CH2S2 molecules. The structure of neutral CH2S2, dithiirane or CH2=S=S, was not determined from the +NR+ mass spectra [158]. Density functional theory calculations favored both dithiirane and its cation-radical as being more stable than CH2=S=S and CH2=S=S+, respectively, and so the authors tentatively assigned cyclic structure to the ion and neutral. 

Tetracyanoethylene (TCNE) is widely used as an excellent dipolarophile in cycloaddition reactions, also including syntheses of 1,3-dithiolane derivatives. Thus, the reaction of the allylic dithioesters 583 with TCNE produced the 1,3-dithiolane cation radical 584, which next reacted with TCNE yielding 3,3,4,4-tetracyano-5-phenyl-6,8-dithia-bicyclo[3.2.1]octane 585 (Scheme 83) <1995T11503>. 

Typical examples for type 1 are the anodic cleavages of two carbon-sulfur bonds in 1,3-dithianes [46] or dithiolanes [47]. This reaction is especially effective if performed under the conditions of indirect electrolysis using triarylamine cation radicals as regenerable oxidative mediators [47] ... 

The molecular cation radical of 2-(3,5-di-/-butyl-4-oxophenyl)-l,3-dithiolane (59), which was generated by the electron impact method, split into ethylene and the cation radical of the corresponding dithiirane 60 (79DOK1030). 

The molecular and electronic structures of cyclic disulfide cation radicals of 1,2-dithietane 6 and 1,2-dithiete 7, and radical cations of 1,2-dithiolane 2 (2a-c represent stable conformations determined in terms of the symmetry restriction of Cs, Cz, and Czv), with emphasis on the nature of a two-center three-electron (Zc-ie) sulfur-sulfur bond have been examined by ab initio molecular orbital (MO) calculations <1997JMT(418)171>. Unrestricted Hartree-Fock (UHF)/ MIDI-4(d) computations showed that this bond in organodisulfide radical cation 2 is shorter in comparison to 1,2-dithiolane 2 and possesses partial Jt-bond character (structure A), as previously implied by electron spin resonance (ESR) spectroscopy <1982JA2318>, which correlates best with the form as the most favorable conformation of the cation radical 2. Contrary to the repulsive S-S interaction in the parent 1,2-dithiolane arising from the lone pairs of electrons, the hemi-7t-bond formed by one-electron oxidation should stabilize the five-membered ring of 2, or, for example, a similar cation radical of LA 3 which is involved in diverse biochemical reactions. 

Ab initio and PM3 semi-empirical methods have been used to optimize the geometry of the benzo[l,5-r 2,4-r ]-dithiolane 4 (R = H or Et). Electron density calculations predicted desymmetrization in the radical cation <1997PCB3665, 1997SM(86)1999>. 

The selective Bock Oxidation using AICI3/CH2Q2 in the meantime has formed widespread application for main group element compounds the prediction of one-electron oxidizability based on first ionization energies IEJ < 8 eV is valid also for numerous other classes of compounds. For examples of ESR/ENDOR-detected radical cations or their rearrangement products, see BN heterocycles H. Noth, W. Winterstein, W. Kaim and H. Bock, Chem. Ber., 112, 2494 (1979) tetra-teri-butyltetrahedrane H. Bock, R. Roth and G. Maier, Chem. Ber., 117, 172 (1984) tetrakis(dimethylamino)-p-benzoquinone H. Bock, P. Hanel and U. Lechner-Knoblauch, Tetrahedron Lett., 26, 5155 (1985) 1,2-dithiolane H. Bock, B. I. Chenards, P. Rittmeyer and U. Stein, Z. Naturforsch. B, 43, 177 (1988), and references cited therein. 

Only a few X-ray crystal structure determinations on 1,3-dithioles have been carried out. Some typical bond lengths and bond angles of the tetrathiafulvalene (5), l,3-dithiole-2-thione derivative (6) and 1,3-dithiolanes (7) and (8) are given in Tables 2 and 3, respectively. Also bond lengths and bond angles of the radical cation of tetrathiafulvalene in the tetrathiafulvalene-7,7,8,8-tetracyanoquinodimethane complex have been determined <74AX(B)763>. 

The major fragmentation pathway of the radical cation 51 generated from the corresponding Czv -symmetrical dithiolane 51 was 1,3-cycloreversion, which led to the generation of two fragments, radical cations 52 and 53 (Scheme 3). The radical cation 54 is present in MS spectra of nearly all dithiolanes of type 51. The radical cation 54 lost the fragments SH or CeHs to form 50 or 55, respectively <2000EJ01695>. 

A new class of highly conducting charge-transfer complexes (306 R=H or Me, X = Cl, Br, or I) has been prepared. ° Cyclic voltammetry of the bis(dithiafulvenyl)-derivatives (307) and (308) has been reported.Oxidation of the bis(dithiolan) (309) with iodine in the presence of aluminium chloride yields the crystalline radical cation salt (310). ... 

Figure 8 Schematic structures of the cation and anion radicals of 1,2-dithiolane in solution at low temperature. Based on results in Bock and Stein [99, 100] for the cation, and Cremonini et al. [102] for the anion. The strongest couping constants observed in the ESR spectra are to the axial H atoms (Max) in the cation and the pseudoequatorial ones (He<,) in the anion.

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