X-RAY AND HIGH-RESOLUTION SE-77 SOLID-STATE NMR-SPECTROSCOPY AS COMPLEMENTARY PROBES TO STRUCTURAL STUDIES OF ORGANOPHOSPHORUS DISELENIDES

Se-77 high resolution solid state NMR spectroscopy was employed to stu dy structural properties of bis(diisopropoxyphosphorothioyl) diselenid e 1 and bis(dineopentoxyphosphorothioyl) diselenide 2. The principal e lements T-ii of Se-77 effective dipolar/chemical shift tensor were cal culated from spinning sideband intensities employing the WIN-MAS progr am. The values of anisotropy and asymmetry parameters reflect the dist ortion of the selenium environment. It was found that the T-33 compone nt mostly contributes to changes in the isotropic chemical shifts. Se- 77 CP/MAS experiments were used to decide the assignment of space grou p by counting the number of crystallographically unique selenium cente rs in the unit cell. Crystals of diselenide 1 are triclinic, space gro up P (1) over bar with a = 8.485(3) Angstrom, b = 8.508(1) Angstrom, c = 8.511(2) Angstrom, alpha = 98.835(15)degrees, beta = 111.653(24)deg rees, gamma = 93.524(21)degrees, V = 559.5(3) Angstrom(3), D-c = 1.544 (2) g/cm(3) and Z = 1. Refinement using 2222 reflections for 157 varia bles gives R = 0.037. Crystals of diselenide 2 are triclinic, space gr oup P1 with a = 9.1418(8) Angstrom, b = 9.1465(8) Angstrom, c = 9.9200 (9) Angstrom, alpha = 74.751(8)degrees, beta = 74.629(7)degrees, gamma = 82.216(7)degrees, V = 769.7(1) Angstrom(3), D-c = 1.365(2) g/cm(3) and Z = 1. Refinement using 3316 reflections for 297 variables gives R = 0.0272. (C) 1998 Elsevier Science B.V. All rights reserved.