David H. Reid

Reactions of 3-Benzylidene-3H-1,2-dithioles and 3-Alkyl-1λ4,2-dithiol-1-ylium Salts with Isonitriles: A Synthesis of 1,6aλ4-Dithia-6-azapentalenes†‡

1,6aλ4-Dithia-6-azapentalenes (7a)–(7h), (12a), and (12b) have been synthesized by the reaction of 5-aryl-3-benzylidene-3H-1,2-dithioles with isonitriles in the presence of phosphoryl chloride and by the reaction of 3-benzyl- and 3-methyl-1λ4, 2-dithiol-1-ylium salts with isonitriles. Possible mechanisms for these reactions are discussed.

3,5-Diphenyl-2-(2-pyridylamino)-1-thia-6,6aλ4-diselenapentalene

Crystals of the title compound, C 22 H 16 N 2 SSe 2 , contain two crystallographically independent molecules in the unit cell. The Se-Se and Se-S bonds are long [Se-Se 2.465 (2), 2.488 (2); Se-S 2.498 (3), 2.495(3)A] and the Se-Se-S bond angle is wide [173.6(4), 174.09 (4)°]. All other bond angles in the triheteropentalene framework are intermediate between those of corresponding single and double bonds. The pyridine ring and the phenyl substituents are twisted out of the plane of the triheteropentalene unit.

N-[(2Z,4Z)-4-Benzyl­idene-6-chloro-1,4-dihydro­pyrido[2,3-d][1,3]thia­zin-2-yl­idene]benzamide

In the crystal structure of the title compound, C21H14ClN3OS, molecules assemble into inversion dimers via pairs of N—H⋯N hydrogen bonds involving the N—H hydrogen of the thiazine ring and the N atom of the pyridine ring. There is a close intramolecular contact [2.570 (2) Å] between the carbonyl O atom of the benzamide and the S atom of the puckered thiazine ring. The title compound can exist in two tautomeric forms, viz. amino or imino. The observed structure is compatible with the imino form on the basis of observed residual electron density and the two C—N bond lengths of 1.308 (2) and 1.353 (2) Å.

Heteropentalenes as donors in charge-transfer complexes

Charge-transfer complexes (CTs) have been known for decades, as expertly documented by Herbstein [1]. One of the archetypal CTs involving heterocycles is tetrathiofulvalinium tetracyanoquinodimethane (TTF TCNQ), renowned for the observation of its high electrical conductivity [2]. Subtle structural features, such as modulation, obviously play an essential part in understanding structure-property relationships in such CTs [3]. The recent observation of roomtemperature ferroelectricity in a different class of CTs demonstrates the topical interest in materials of this type [4], as well as the ongoing discussion about the nature of the CT interactions and the role of dispersive forces [5-6]. In this work we investigate the use of substituted heteropentalenes, such as dithia-6-azapentalene, together with strong aromatic donors, such as trinitrobenzene, to generate a new class of charge-transfer complexes. The heteropentalenes investigated, shown schematically in Fig.1, include those with Q = S, N; X = C, N and R = H,Me, iBu, Ph. Theycan be prepared by methods reported previously [7]. Only donors with Q = N, X = C have thus far yielded CT complexes. Their preparation, structures and solid-state properties will be discussed in this paper. Fig. 1 Stacking of 2-tert-butyl-6-methyl-dithia6 azapentalene and TNB molecules in the 1:1 CT crystal showing the two strongest intermolecular interactions (-60.7 and -44.5 kJ/mol). [1] Herbstein, F. H., Crystalline molecular complexes and compounds : structures and principles. (2005); New York : Oxford University Press. [2] Coleman, L.; Cohen, M.; Sandman, D. J.; Yamagishi, F.; Garito, A. F.; Heeger, A. (1973). Solid State Communications, 12, 1125. [3] Coppens, P.; Petricek, V.; Levendis, D.; Larsen, F. K.; Paturle, A.; Yan, G.; Legrand, A. D. (1987). Physical Review Letters 59, (15), 1695-1697. [4] Tayi, A. S.; Shveyd, A. K.; Sue, A. C. H.; Szarko, J. M.; Rolczynski, B. S.; Cao, D.; Kennedy, T. J.; Sarjeant, A. A.; Stern, C. L.; Paxton, W. F.; Wu, W.; Dey, S. K.; Fahrenbach, A. C.; Guest, J. R.; Mohseni, H.; Chen, L. X.; Wang, K. L.; Stoddart, J. F.; Stupp, S. (2012). Nature 488, 485. [5] Schneider, H.-J. (2012). Accounts of Chemical Research 46, 1010. [6] Bertolasi, V.; Gilli, P.; Gilli, G. (2012). Crystal growth & design 12, 4758. [7] Dingwall,, J. G., Ingram, A. S., Reid, D. H. & Svmon, J. D. (1973). J. Chem. Soc. Perkin Trans. 1, 2351-2358.

5,6,7,8-Tetrahydro-2,3-diphenyl-2aλ4-thia-2,3,4a,8a-tetraazacyclopent[cd]azulene-1[2H],4[3H]-diselone

The title compound, C19H18N4SSe2, crystallizes in the P\overline{1} space group with two molecules in the asymmetric unit. In both molecules the chemically equivalent halves are identical within experimental error, except for conformational differences which arise from intermolecular interactions between the flexible seven-membered rings and surrounding selenium atoms. The central triheterapentalene system is almost planar, with individual ring conformations consistent with three regions of conjugation separated by single bonds. The N-S bond lengths, stretched beyond the standard for a single bond, imply a three-centre interaction.

5-Ethylamino-3-p-tolyl-1λ4,2,4-thiaselenazol-1-ylium Bromide: a New Heteroaromatic System

In the title compound, C 11 H 13 N 2 SSe + .Br - , the Se-S bond length is 2.189 (2) A and the C(2) - Se and C(1) - S bond lengths are 1.890 (3) and 1.765 (3) A, respectively. The C(2)-Se-S and C(1)-S-Se bond angles are 89.36(10) and 93.36 (11)°, respectively. In the planar heterocyclic ring, π-electron delocalization extends over the exocyclic N(2) atom.