Crystal and molecular structure of dodecamethoxycyclohexaphosphazene: non-bonded interactions and conformation

Abstract

Crystals of the title compound are monoclinic, a= 11·434, b= 12·891, c= 9·805 Å(all ±0·008 Å), β= 104·5 ± 0·1°, Z= 2, space group P2₁/n. The structure was determined from photographic data by Patterson and Fourier methods and refined three dimensionally to R 0·11 for 2228 observed reflections. The molecule is centrosymmetric and has a double-tub conformation, in which all the ring bonds are equal in length (1·567 Å); ring N–P–N angles are 114·4–121·6°(mean 118·5°), and P–N–P angles 133·4–135·1°(mean 134·3°). The detailed stereochemistry is similar to that of phosphate diesters. The angles at phosphorus, the conformation of the ring, and the orientation of the methoxy-groups are inter-related, and are discussed in terms of non-bonded interactions, including polar contributions.