Charge-Transfer Complexes of 4-Phenyl-1,2,3,5-dithiadiazolyl and 4-Phenyl-1,2,3,5-diselenadiazolyl with Iodine. Preparation and Solid-state Characterization of [PhCN2E2]3[I3] (E = S, Se) and [PhCN2S2][I3]

The 1:1 reaction of the heterocyclic radicals [PhCN2E2]∙ (E = S, Se) and iodine affords the mixed valence salts [PhCN2E2]3[I3], while reaction of PhCN2S2 with an excess of iodine affords the simple salt [PhCN2S2][I3]; the solid-state structures of these complexes have been determined by X-ray crystallography. Crystals of both of the mixed valence compounds belong to the triclinic space group P¯1; for E = S, a = 10.278(4), b = 11.508(2), c = 13.333(4) Å, α = 114.97(2), β = 99.21 (3), γ = 92.65(2)°, FW = 308.15, Z = 6; for E = Se, a = 10.368(6), b = 10.818(8), c = 13.421(8) Å, α = 80.64(5), β = 81.20(5), γ = 75.18(6)°, FW = 401.95, Z = 6. Crystals of the simple salt belong to the monoclinic space group P21/a; a = 7.366(4), b = 11.734(1), c = 15.166(2) Å, β = 95.92(3)°, FW = 1303.99(7), Z = 4. In each of the mixed valence compounds the molecular (asymmetric) unit consists of a trimeric [PhCN2E2]3+ cation and an associated triiodide anion. Within the cations the mean interannular E-E contacts are 3.181/3.377 Å (E = S/Se). The packing patterns of the two compounds show important differences. For E = S the crystal structure does not exhibit stacking of the trimeric molecular building blocks, but for E = Se the trimer units form dovetailed stacks in which consecutive layers are oriented in a trans-antipodal fashion. This arrangement introduces close interannular contacts between the blocks along the stack, as well as close lateral contacts. The asymmetric unit of [PhCN2S2][I3] consists of a single PhCN2S2+ cation and an associated triiodide anion; there are no unusual stacking features. The magnetic and conductivity properties of [PhCN2Se2]3[I3] are reported, and the results discussed in the light of extended Hückel band structure calculations.