Synthesis and crystal structure of 1,3-di-tert-butyl-2-chloro-4,4-diphenyl-1,3,2λ3,4-diazaphosphasiletidine

Abstract

The chemical reaction of dilithium N,N′-di(tbutyl)-Si,Si-diphenylsilanediamide and PCl3 yielded an off-white solid. Sublimation of the crude product under reduced pressure at elevated temperature gave colourless prismatic crystals of the title compound, C20H28ClN2PSi, which crystallizes in the non-centrosymmetric monoclinic space group Cc. The asymmetric unit of the crystal structure contains one molecule and it is dominated by the central SiN2P 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 nitrogen atoms and the best planes of the Si-phenyl groups are 85.1 (2) and 77.4 (2)°, with the tilt of the phenyl rings in the opposite direction. Both tert-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 PCl3 [2.034 Å; Galy & Enjalbert (1982). J. Solid State Chem. 44, 1–23].

Keywords

• diazaphosphasiletidine
• four-membered heterocycle
• crystal structure
• long P—Cl bond