STRUCTURES OF THE PHOSPHAZENES [CLC(NPCL3)(2)]- AND [CH3C(NPCL3)(2)]+SBCL6- AT 90 K(PCL6)

The asymmetric units of both ionic compounds [N-(chloroformimidoyl)pho sphorimidic trichloridato]trichlorophosphorus hexachlorophosphate, [Cl C(NPCl3)(2)](+)-PCl6- (1), and [N-(acetimidoyl)phosphorimidic trichlor idato]trichlorophosphorus hexachloroantimonate, [CH3C(NPCl3)(2)]+SbCl6 - (2), contain two formula units with the atoms located on general pos itions. All the cations show cis-trans conformations with respect to t heir X-C-N-P torsion angles [X = Cl for (1), C for (2)], but quite dif ferent conformations with respect to their C-N-P-Cl torsion angles. Th erefore, the two NPCl3 groups of a cation are inequivalent, even thoug h they are equivalent in solution. The very flexible C-N-P angles rang ing from 120.6 (3) to 140.9 (3)degrees can be attributed to the intram olecular Cl ... Cl and Cl ... N contacts. A widening of the C-N-P angl es correlates with a shortening of the P-N distances. The rigid-body m otion 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.