Crystal structure of compounds with (N–P)n rings. Part 12. Decafluorocyclopentaphosphazene

Abstract

Three monoclinic crystal modifications of the title compound (m.p. –50 °C) have been obtained by low-temperature crystallization. The crystallographic data are: (1). space group P2₁/c, a= 11.098(19), b= 14.459(6), c= 11.784(19)Å. β= 142.4(5)°;.(2), space group P2₁/a, a= 15.785(12), b= 15.237(10), c= 4.919(6)Å, β= 97.4(2)°; and (3). space group P2₁/n, a= 14.02, b= 16.02, c= 5.24 Å, β= 99.5 °. The crystal structures of modifications (1) and (2) have been determined from low-temperature diffractometer data by the symbolic addition method and refined by block-diagdnal least-squares analysis [(1), 1 598 reflections, R 0.59; (2), 1 919 reflections, R 0.74]. The unit cell in both structures contains four molecules in a general position. In (1) the (N–P)₅ ring of the molecule is somewhat boat-shaped and the molecule has a pseudo-two-fold rotation axis passing through an N and a P atom. In (2) the molecule has a rather irregular shape, which resembles to some extent the structure of N₅P₅Br₁₀ Mean P–N bond lengths are 1.549(5) in (1) and 1.546(5)Å in (2). The mean P–F bond length is the same in (1) and (2)[1.528(4)Å]. The P–N–P angles range from 132.7 to 151.6 °[means 137.4(3) for (1) and 140.6(4)° for (2)]. The N–P–N angles range from 119.1 to 123.9 °[means 121.4(2) in (1) and 120.9(3)° in (2)]. The mean value of the F–P–F angles in (1) and (2) is 99.4(2)°.