Crystallographically determined SeO and PO interactions in tris(2,4-dimethoxyphenyl) phosphine selenide and the 2,4,6-trimethoxy analogue. Correlations of PSe bond lengths with 77Se NMR data

Abstract

(2,4-Dimethoxyphenyl) 3PSe crystallizes in the monoclinic space group P2 1/ n with four molecules in the unit cell having dimensions of a = 9.0660(1), b = 17.2102(3), c = 17.2475(3) Å, β = 98.3(2)° and refined to R = 5.2% for 1258 observed reflections. (2,4,6-Trimethoxyphenyl) 3PSe is orthorhombic, space group P2 12 12 1 with four molecules in the unit cell a = 18.2983(5), b = 12.3716(1), c = 12.4696(1) Å and refined to R = 6.4% for 1229 observed diffractometer data. In both cases the rings are orientated so that weak PO interactions take place between one of the o-methoxy groups and phosphorus. Similar interactions between selenium and oxygen are also found. These interactions may account for the significant deshielding of the selenium atom in these compounds compared with related triarylphosphine selenides as shown by 77Se NMR data.