Crystal and molecular structures of dimorpholino-tri- and -di-selane

Abstract

Crystals of the title compound Se₃(NC₄H₈O)₂(1) are orthorhombic, space group Pbcn(no. 60) with a= 5.445(1), b= 9.473(2), c= 25.408(2)Å, and Z= 4. Crystals of Se₂(NC₄H₈O)₂(2) are monoclinic, space group P2₁/c(no. 14) with a= 8.871(1), b= 5.716(1), c= 23.820(3)Å, β= 98.59(1)°, and Z= 4. The structures have been determined by X-ray diffraction from Mo-K_α diffractometer data and refined by full-matrix least squares to R 0.035 and 0.035 for 899 and 2 017 observed reflections respectively. In (1) the molecules lie across crystallographic two-fold axes. The N–Se–Se–Se–N chains occur in the trans form, with N–Se 1.841(5), Se–Se 2.352(1)Å, N–Se–Se 105.2, Se–Se–Se 101.7(1)°, and NSeSe–SeSeSe 97.1°. Intermolecular Se ⋯ Se contacts of 3.404(2)Å occur across the two-fold axes. The N–Se–Se–N chains in (2) have N–Se 1.846(4) and 1.852(4), Se–Se 2.346(1)Å, N–Se–Se 109.0(1) and 109.2(1)°, and NSeSe–SeSeN 94.7°. The shortest intermolecular Se ⋯ Se contact in (2) is 3.588(1)Å. In both compounds the morpholine rings occur in the chair form, with N–Se equatorial.