PREPARATION AND SOLID-STATE STRUCTURES OF (CYANOPHENYL)DITHIADIAZOLYL AND (CYANOPHENYL)DISELENADIAZOLYL RADICALS

The preparation and solid-state characterization of the dimers of the cyanophenyl-substituted 1,2,3,5-dithia- and 1,2,3,5-diselenadiazolyl radicals [NCC6H4CN2E2]. (E = S, Se) are described. Crystals of the 4-cyanophenyl derivatives 4 are triclinic, space group P1BAR. The radicals dimerize in a cofacial fashion, with mean intradimer E---E spacings of 3.104/3.233 angstrom (E = S/Se). The dimer units form ribbonlike arrays connected by head-to-tail CN---E contacts. The ribbons are packed in an antiparallel fashion with no close interdimer E---E contacts. The 3-cyanophenyl sulfur derivative 5 crystallizes in two phases. The alpha-phase, along with the isomorphous selenium compound, belongs to the monoclinic space group P2(1)/n. As in the 4-cyano derivatives, the radicals dimerize cofacially, generating ribbons connected by head-to-tail CN---E contacts. The ribbons, however, are layered with CN2E2 rings oriented into stacks parallel to the a axis. In addition to short intradimer E---E contacts (mean values = 3.13 (2)/3.27 (4) angstrom for E = S/Se), there are relatively short interdimer E---E contacts (mean values = 4.26 (5)/4.15 (5) angstrom (E = S/Se) along the stacking axis. The beta-phase of the 3-cyanophenyl sulfur compound 5, monoclinic space group P2(1)/n, forms discrete dimers associated in a trans antarafacial fashion, with intradimer S---S contacts of 3.121 (1) angstrom; there are no close interdimer S---S contacts. The 2-cyanophenyl selenium derivative 6 crystallizes in the polar space group P2(1). In this structure also the dimer units are laced together by short CN---Se contacts. The dimers form stacks parallel to the b axis, with mean intradimer and interdimer Se---Se contacts of 3.312/4.083 angstrom, respectively. Lattice constants for the six structures are: 4 (E = S), C8H4N3S2, a = 10.466 (3) angstrom, b = 10.342 (2) angstrom, c = 9.169 (2) angstrom, alpha = 104.97 (2)-degrees, beta = 112.97 (2)-degrees, gamma = 69.84 (2)-degrees, V = 849.0 (3) angstrom3, Z = 4; 4 (E = Se), C8H4N3Se2, a = 10.478 (4) angstrom, b = 10.780 (4) angstrom, c = 9.432 (4) angstrom, alpha = 107.16 (3)-degrees, beta = 115.23 (2)-degrees, gamma = 68.39 (3)-degrees, V = 883.8 (6) angstrom3, Z = 4; 5 (E = S, alpha-phase), C8H4N3S2, a = 7.295 (3) angstrom, b = 20.488 (2) angstrom, c = 11.276 (2) angstrom, beta = 95.54 (2)-degrees, V = 1676.0 (7) angstrom3, Z = 8; 5 (E = Se), C8H4N3Se2, a = 7.364 (8) angstrom, b = 21.085 (2) angstrom, c = 11.119 (4) angstrom, beta = 94.91 (5)-degrees, V = 1720 (7) angstrom3, Z = 8; 5 (E = S, beta-phase), C8H4N3S2, a = 8.782 (1) angstrom, b = 5.638 (1) angstrom, c = 17.128 (4) angstrom, beta = 102.94 (2)-degrees, V = 826.5 (6) angstrom3, Z = 4; 6 (E = Se), C8H4N3Se2, a = 7.301 (1) angstrom, b = 11.883 (2) angstrom, c = 10.186 (1) angstrom, beta = 101.50 (1)-degrees, V = 866.1 (5) angstrom3, Z = 4.