X-ray and high resolution selenium-77 solid state NMR spectroscopy as complementary probes to structural studies of...

77Se high resolution solid state NMR spectroscopy was employed to study structural properties of bis(diisopropoxyphosphorothioyl) diselenide 1 and bis(dineopentoxyphosphorothioyl) diselenide 2. The principal elements Tii of 77Se effective dipolar/chemical shift tensor were calculated from spinning sideband intensities employing the WIN-MAS program. The values of anisotropy and asymmetry parameters reflect the distortion of the selenium environment. It was found that the T33 component mostly contributes to changes in the isotropic chemical shifts. 77Se CP/MAS experiments were used to decide the assignment of space group by counting the number of crystallographically unique selenium centers in the unit cell. Crystals of diselenide 1 are triclinic, space group P1 with a = 8.485(3) A, b = 8.508(1) A, c = 8.511(2) A, alpha = 98.835(15) degrees, beta = 111.653(24) degrees, gamma = 93.524(21) degrees, V = 559.5(3) A3, Dc = 1.544(2) g/cm3 and Z = 1. Refinement using 2222 reflections for 157 variables gives R = 0.037. Crystals of diselenide 2 are triclinic, space group P1 with a = 9.1418(8) A, b = 9.1465(8) A, c = 9.9200(9) A, alpha = 74.751(8) degrees, beta = 74.629(7) degrees, gamma = 82.216(7) degrees, V = 769.7(1) A3, Dc = 1.365(2) g/cm3 and Z = 1. Refinement using 3316 reflections for 297 variables gives R = 0.0272.