Crystal and molecular structure of nitrilohexaphosphonitrilic chloride [2,2,3a,5,5,6a,8,8,9a-nonachloro-2,2,5,5,8,8-hexahydro-1,3,4,6,7,9,9b-hepta-aza-2,3a,5,6a,8,9a-hexaphospha(3a,6a,9a,-PV)phenalene]

Abstract

Crystals of the title compounds are monoclinic, a= 19·817, b= 6·357, c= 29·897 Å, β= 99·38°, Z= 8, space group C2/c. The structure was determined by direct methods, and was refined by electron-density and full-matrix least-squares procedures to R 0·048 for 1947 observed reflections. P₆N₇Cl₉ has a non-planar condensed ring structure which shows small but significant deviations from C_3v symmetry. The structure can be interpreted as containing a set of three central weakened σ-bonds supplemented by π-bonds. These central P–N bonds, 1·723(6)Å, are longer than for any other phosphazene derivative hitherto reported. The remaining P–N bonds average 1·558(6) and 1·570(6)Å. The two types of P–Cl bonds have significantly different values, 2·004(3) and 1·980(3)Å.