Crystal structures of cis-2,4,6-trichloro- and cis-2,4,6-tribromo-2,4,6-trifluorocyclotri(phosphazene)

Abstract

The crystal structures of (I), 2,cis-4,cis-6-trichloro-, and (II), 2,cis-4,cis-6-tribromo-2,4,6-trifluorocyclotri-(phosphazene), have been determined by Patterson and Fourier methods and refined by least squares to R 0·028 [(I) 534 reflexions] and 0·071 [(II), 539 reflexions]. Crystals of both compounds are orthorhombic, space group Cmc 21, with Z= 4. The ring conformation for (I) is a slight boat while in (II) it is an irregular slight chair. These deviations from planarity together with small differences in some of the chemically equivalent bond distances and angles are attributed to crystal packing effects. Crystal data: (I), a= 12·575(1), b= 9·654(1), c= 7·75(1); (II), a= 12·514(2), b= 10·144(1), c= 7·987(1)Å.