Structures of the Phosphazenes [ClC(NPCl₃)₂]⁺PCl₆ ⁻ and [CH₃C(NPCl₃)₂]⁺SbCl₆ ⁻ at 90 K

Abstract

The asymmetric units of both ionic compounds [N-(chloroformimidoyl)phosphorimidic trichloridato]trichlorophosphorus hexachlorophosphate, [C1C(NPCI3)2] +-PC16 (1), and [N-(acetimidoyl)phosphorimidic trichloridato]trichlorophosphorus hexachloroantimonate, [CH3C(NPC13)2]+SbCI6 (2), contain two formula units with the atoms located on general positions. All the cations show cis-trans conformations with respect to their X--C--N--P torsion angles [X = C1 for (1), C for (2)], but quite different conformations with respect to their C--N--P--C1 torsion angles. Therefore, the two NPC13 groups of a cation are inequivalent, even though they are equivalent in solution. The very flexible C--N--P angles ranging from 120.6 (3) to 140.9 (3) ° can be attributed to the intramolecular C1...C1 and C1...N contacts. A widening of the C--N--P angles correlates with a shortening of the P--N distances. The rigid-body motion analysis shows that the non-rigid intramolecular motions in the cations cannot be explained by allowance for intramolecular torsion of the three rigid subunits about specific bonds.