THE CRYSTAL-STRUCTURES OF (NET4+)2[SE5(2-).1/2SE6.SE7] AND (NPR4)2SE11

The title compounds have been prepared by the reactions of a potassium diselenide solution in DMF with excess selenium in the presence of tetraethyl and tetrapropyl ammonium chloride, respectively. They were characterized by X-ray crystal structure determinations. (NEt4+)2[Se5(2-).1/2 Se6.Se7]: Space group P1BAR, Z = 2, 2514 observed unique reflections, R = 0.085. Lattice dimensions at -40-degrees-C: a = 957.7(4), b = 1384.2(4), c = 1545.3(7) pm, alpha = 107.32(3)-degrees, beta = 97.27(4)-degrees, gamma = 105.94(3)-degrees. The compound has an ionic structure of NEt4+ ions and chains of pentaselenide ions, which are associated with Se6 and Se7 ring molecules, forming layers parallel to (1 10BAR). (NPr4)2Se11: Space group C2/c, Z = 4, 2198 observed unique reflections, R = 0.082. Lattice dimensions at -40-degrees-C: a = 2364.7(5), b = 1206.8(2), c = 1609.6(3) pm, beta = 118.74(3)-degrees. The compound consists of cations (N(C3H7)4+ and spirocyclic anions Se11(2-), in which two Se6 rings having chair conformation are linked by a common Se atom with planar coordination. There are no short contacts between the S11(2-) ions.