1.2- Dithiole-3-thiones structure

An NMR study of stereoelectronic effects in dithiolane sulfoxides such as 35 has appeared <07CEJ4273> and the new donor-acceptor system 36 has been examined for possible use in solar cells. A variety of new crystallographic studies of l,3-dithiole-2-thione structures have... 

Potential 2-hydroxy- and 2-mercapto-l,3,4-thiadiazoles have been examined both by infrared and by ultraviolet spectra in the solid state and in solution by Sheinker et They concluded that these compounds exist in the 2-oxo and 2-thione forms, respectively. To 2,5-dimercapto-l,3,4-thiadiazole the 2-mercapto-5-thione structure (155) was given. The structure of this compound has been the subject of some controversy. Stanovnik and TiSler have added some valuable arguments to the discussion. They measured the pKfl values of 155, its iV-methyl, iV -phenyl, and iV -phenyl-/S-methyl derivatives (156), and of the conjugate acids of these and the S-methyl derivative (pKn ) (Table III). In all compounds 156 with R = H, the infrared spectrum showed an absorption band near 2300 cm characteristic of the SH group. They also had pK i values near —1.5, Avhich in connection with the infrared evidence was taken as characteristic of an SH group in this situation. Since the 2,5-dithiol structure is excluded by ultraviolet spectral evidence, the 2-mercapto-5-thione structure (155) seems rather well established. It has previously been shown bj Thorn to predominate in chloroform solution, whereas he concluded that the dithione form (157) should predominate in ethanol solution. However, the pK i value for 155, — 1.36, makes it rather probable that Thorn used the monoanion of 155 instead of the acid itself for spectral comparison, and in that case his conclusions have a very weak foundation. 

The reaction of 36 with sulfur in dimethylformamide gave a compound which was originally ascribed the l,2-dithiole-3-thione structure 37.72 X-Ray studies, however, showed that the coronenelike trithiapentalene structure... 

The structure of [Mo3S4(dmit)3] (dmit=l,3-dithiole-2-thione-4,5-dithiolate) represents one of the rare examples of M3S4 clusters where each metal atom appears as pentacoordinate instead of its more common type-I structure octahedral environment [39]. Complexes [M3Q4(dmit)3] (M = Mo, W Q = S, Se) degrade in air with an almost quantitative yield and afford a series of M(V) dimers of formula [M202(//-Q)2(dmit)2] where the oxygen atoms are in a syn configuration. 

For some strong electron donor molecules the polarization of the X2 molecule may be sufficient that the X atom not complexed to B serves as an electron donor to a second X2 molecule, i.e., the dihalogen is amphoteric , acting as a Lewis acid to Lewis base B, and as a Lewis base to the second X2 molecule, acting as a Lewis acid. For a 1 1 B X2 X2 ratio, an extended adduct (Fig. 1, mode AA) is formed, as illustrated in Fig. 2c for 4,5-bis(bromomethyl)-l,3-dithiole-2-thione-diiodine diiodine (HAMCAA) [58]. This is often referred to as an extended spoke structure. If the second X2 acts as Lewis acid acceptor at either end of the molecule, then a bridged amphoteric adduct (Fig. 1, mode BA) is formed, as illustrated for (acridine I2)2 I2 (QARGIZ) [31] in Fig. 2d. 

A polymeric structure is also observed in the adduct LE 2I2 (LE = 4,5-6z s(bromomethyl)l,3-dithiole-2-thione). LE-I2- I2 bent-shaped units, which are typical in discrete extended spoke adducts with 1 2 (LE/I2) stoichiometry, are joined head-to-tail by soft-soft I- -I interactions involving the terminal iodide atom of the LE-I2 moiety and the terminal iodide atom of the second coordinated di-iodine molecule.37... 

Interestingly, the introduction of two bromomethyl functions in 4- and 5-positions of ethylen-l,3-dithiole-2-thione leads to a packing determined by weak interactions involving also the bromine atoms. One I2 molecule behaves as an acceptor towards S and as donor towards the second I2 molecule, which in turn behaves as donor towards the a c Br orbital (Figure 13). Intermolecu-lar S- -Br, CFF Br and L -I contacts make up a three-dimensional network.480 Reaction of 5,5-dimethyl-2-selenoxoimidazoline-4-one with iodine provided the first structurally characterised compound of the type [RR C Se — I-I].32 The Se-I bond is shorter (269.9 pm) and the I-I contacts are longer (296.2 pm) than in 1 1 adducts of dialkylselenides with iodine (see Chapter 8.2). 

The synthesis, X-ray structure and solid state NMR of 4,4-dimethyl-l,2-ditellurolane 75 have been reported <98PS(136-8)291>. Chemoselective oxidation of 1,2-dithiole derivatives using dimethyldioxirane to give products such as 76 has been described <00SUL169>. Cycloaddition of dihydroquinoline-fused l,2-dithiole-3-thiones 77 with DMAD gives the spiro 1,3-dithioles 78 <99CHE587>. Dicationic thiatelluroles such as 79 have been prepared <00AG(E)1318>, anti cancer properties have been claimed for the simple dithiolopyrrolones... 

The peripheral selenodiazole rings of porphyrazine (169) can be opened upon treatment with H2S with the proposed formation of the octaaminoporphyrazine (184), which was not isolated and instead converted into the tetrakis(pyrazino)porphyrazine (185) (Scheme 34) (171). Other heterocycles have been fused on the periphery of porphyrazines, such as l,3-dithiol-2-thione in order to extend the aromatic core (172). Macrocyclization of 4,5-dicyano-l,3-dithiole-2-thione (186) under Linstead conditions in the presence of magnesium butoxide produced the symmetrically substituted tetrakis(l,3-dithiol-2-thiono)porphyrazine (187) (Scheme 35). Due to the low solubility of porphyrazine 181, a consequence of the planar aromatic molecular structure, a full characterization of this compound could not be accomplished. 

M(dmit)2 complexes (dmit = C3S52- = l,3-dithiole-2-thione-4,5-dithio-late) constitute one of the most important subclasses. The most studied metal complexes are those of group 10 (Ni, Pd, Pt), which possess a square-planar geometry see for instance the molecular structure of the monoanion [Ni(dmit)2], Figure 42.73... 

Many papers deal with both analytical determination and cathodic transformations of thiones (21). Thus, a four-electron reduction of OLTIPRAZ [4-methyl-5-(2-pyrazinyl)-l,2-dithiole-3-thione] produces several species that could account for the schistosomicidal activity of metabolites of the starting compound. The first two-electron reduction (in aqueous media) affords the scission of the S —S linkage and the thus formed dianion can be readily [197] alkylated by common alkyl halides. Let us note that the cathodic behavior of structure (21) was shown to be strongly influenced by the nature of substituents and particularly [198] by the electron-donating ability of Rh... 

Structurally similar 5-chloro-l,2-dithiole-3-thiones 97 were obtained upon treatment of N-(2-phthalimidoethyl)-N-alkylisopropylamines with sulfur monochloride and DABCO and a final reaction with tiiethylamine (20030L929). The stability of thiones 97 is explained by the dipole-dipole interaction between the electron-rich l,2-dithiole-3-thione ring and electron-poor phthalimido groups (Scheme 48). 

Di-f-butyl-3,6-dineopentylthieno[3,2b]thiophene (338) was obtained unexpectedly by the phosphite desulfurization of 4-r-butyl-5-neopentyl-l,3-dithiole-2-thione (337 Scheme 117). The alternate structure (339) was ruled out on the basis of an X-ray analysis (75UP31800). 

The intermolecular Diels-Alder reactions of 1,3-dithioles (163) with DMAD and DEAD produced the first 7//-thieno[2,3-c]thiopyran-7-thiones (164) and 47/-thieno [3.2-c]thiopyran-4-thiones (165), the structures of which were confirmed by X-ray diffraction. Further work on the mechanism of the cycloaddition and subsequent rearrangement is in progress (Scheme 46).191... 

Syntheses and X-ray structures have been reported for (53) [94T11205] and (54) [95MI645], The preparation and non-linear optical properties of 2-imino-l,3-dithioles (55) have been described [95MI35] and the dimeric derivatives (R3 = p-phenylene) have also been reported [94BSF774]. The product (56), obtained from reaction of 4-methyl-5-phenyl-l,2-dithiol-3-thione with DMAD, undergoes cycloaddition with a further molecule of DMAD to afford the spiro compound (57) whose structure is confirmed by X-ray methods [94KGS908]. 

These structures may be named as follows 7, l-(l,2-benzodithiol-3-ylidene)propane-2-thione and 8, 6-(5-methyl-l,2-dithiol-3-ylidene)-2,4 -cy clohexadiene-1 -thione. 

However, it has been shown67-69 that the structure of the final product may depend on the experimental procedure. For example, if phenylacetylene reacts with 5-phenyl-l,2-dithiole-3-thione in xylene in the presence of hydrochloric acid, the l,3a IV,4-trithiapentalene is obtained but by using neutral dry xylene as solvent, a l,6,6a IV-trithiapentalene is formed which can also be obtained by heating the l,3aiSIV,4-isomer with phosphorus pentasulfide in tetrahydronaph-thalene (Scheme 14).67,68... 

Dithiolium ions, l,2-dithiole-3-thiones, and 1,6,6astructural relationships which can be further extended. Compounds of this series are of peculiar interest because of the structural problems involved concerning the nature of the chemical bond and the aromaticity of the ring systems. 

From 5-[(l,2-dithiol-3-ylidene)alkyl]-l,2-dithiole-3 thiones (74) other extended structures can be obtained,89 90 e.g., (a) a-( 1,2-dithiol-3-ylidene)-a -(l,3-dithiol-2-ylidene)thioketones (77), by reaction... 

For the compound (13) the sulfur-sulfur distance was 2.054 A, in accord with the non-ionic structure (13a) (77TL2717). 4-Thioacyl-l,2-dithiole-3-thiones (14) show no interaction between the two thione sulfur atoms (77JCS(P2)1854). 

Benzo-l,2-dithiole-3-thione (77b) also reacts, but the monoadducts corresponding to (95) have o-thioquinone methide structures (cf. structure 104) and form diadducts rapidly. The use of dehydrobenzene (benzyne) gives 2-thioacylmethylenebenzo-l,3-dithioles (95 R3, R4 = (CH=CH)2). 

The 2,4-bis(thiobenzoylmethylene)-l,3-dithiete (169) has an obvious structural relationship to 4,5-diphenyl-l,2-dithiole-3-thione (170), which is formed on thionation (73TL1915). 

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>. 

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