Crystal structure of 2,2,4,4-tetrachloro-6,6-bis(trimethylsilylamino)cyclo-triphosphazene, N3P3Cl4(NHSiMe3)2

Abstract

The X-ray crystal structure of N₃P₃Cl₄(NHSiMe₃)₂ has been determined. Crystals are monoclinic, space group C2/c, with a= 13.749(6), b= 7.343(3), c= 20.124(3)Å, β= 95.24(3)°, and Z= 4; R= 0.049 for 961 unique observed reflections. The phosphazene ring lies on a crystallographic two-fold axis and is planar within 0.031(2)Å. The exo P–N bond distance is 1.609(5) and the Si–N bond distance is 1.757(5)Å which suggests preferential nitrogen lone pair delocalization to the phosphorus atom. The P–N distances in the ring alternate (from the P with the exo N atoms) from 1.617(5) to 1.551(5) to 1.591(4)Å. The structural and ³¹P n.m.r. parameters of N₃P₃Cl₄(NHSiMe₃)₂ are compared to those of the analogous t-butylamino derivative.