Molecular structures of non-geminally substituted phosphazenes. Part VI. Crystal structure of 2,cis-4,trans-6,trans-8-tetrachloro-2,4,6,8-tetraphenylcyclotetraphosphazatetraene

Abstract

Crystals of the title compound (Ia) are triclinic, a= 11·47, b= 9·31, c= 8·14 (all ±0·02)Å, α= 114·2, β= 115·2, γ= 89·3°(all ±0·3°), space group P, Z= 1. The structure was solved by Patterson and superposition methods from visually estimated photographic X-ray intensity data and refined by full-matrix least-squares to R 0·081 for 1890 reflexions. The molecule occupies a crystallographic centre of symmetry and the eight-membered phosphazene ring has a chair conformation with P–N–P angles of 132·9 and 137·9°. Mean bond lengths (P–N 1·572, P–Cl 2·044, P–C 1·796, and C–C 1·38 Å) are similar to those in the 2,cis-4,cis-6,cis-8-isomer. The phosphazene ring shape is very similar to that in three other chlorotetraphosphazenes but is less puckered than that in its derivative N₄P₄(NHMe)₄Ph₄.