Crystal structure of 1, cis-3, cis-5-trichloro-1,3,5,7,7-pentakis(dimethylamino)cyclotetraphosphazene

Abstract

Crystals of the title compound are orthorhombic with a= 32.484(8), b= 12.816(3), and c= 11.783(3)Å, space group Pbca, Z= 8. The atomic positions have been determined by Patterson and Fourier methods from X-ray data and refined by least squares to R 0.038 (3 363 reflexions). The ring bond lengths vary in pairs, 1.586, 1.545, 1.570, and 1.564 Å, in a manner explicable in terms of different degrees of ring π bonding involving the nitrogen lone pairs. Exocyclic P–N bond lengths are all equal (1.633 Å) and continue the trend established in similar systems. The irregular ring conformation is best described as a mixed crown–saddle, the former being associated with the three non-geminally substituted atoms [P(1)–(3)] while the latter contains the P(1), P(3), P(4) segment. Details of the ring conformation can be related to substituent orientation.