Synthesis and crystal structure of 1,3-di--butyl-2-chloro-4,4-diphenyl-1,3,2λ,4-di-aza-phospha-siletidine.

The chemical reaction of di-lithium ,'-di( but-yl)-,-di-phenyl-silanedi-amide and PCl yielded an off-white solid. Sublimation of the crude product under reduced pressure at elevated temperature gave colourless prismatic crystals of the title compound, CHClNPSi, which crystallizes in the non-centrosymmetric monoclinic space group The asymmetric unit of the crystal structure contains one mol-ecule and it is dominated by the central SiNP four-membered ring, which is almost planar with a mean deviation of the atoms from the best plane of 0.014 Å. The angles between the plane defined by the silicon atom and the two nitro-gen atoms and the best planes of the -phenyl groups are 85.1 (2) and 77.4 (2)°, with the tilt of the phenyl rings in the opposite direction. Both -butyl groups suffer from a two-position rotational disorder with site occupancies of 0.752 (6)/0.248 (6) and 0.878 (9)/0.122 (9). The P-Cl bond [2.2078 (17) Å] is remarkably elongated compared to the P-Cl distance in PCl [2.034 Å; Galy & Enjalbert (1982). , 1-23].