STRUCTURE AND THERMAL MOTION OF TETRAKIS(TRICHLOROPHOSPHAZENO)PHOSPHONIUM DICHLOROIODATE(I), [P(NPCL3)(4)](-).2[(CCL4)(X)(CHCL3)(1-X)], X=0.67 (2)()[ICL2]()

P(NPCl3)(4)](+)[ICl2](-).2[(CCl4)(x)(CHCl3)(1-x)], x= 0.67(2), M(r)=11 19.1, tetragonal, I4(1)/acd, a= 16.114(4), c=27.777(7)Angstrom, V=7213 (1)Angstrom(3), Z=8, D-x=2.06 g cm(-3), lambda(Mo K alpha)=0.71069 Ang strom, mu= 2.76 mm(-1), F(000)=4251.5, T=293 K, R=0.0434, wR=0.0452 fo r 596 unique observed reflections and 80 parameters. The cation, anion and solvent molecules show site symmetries of S-4, D-2 and C-2, respe ctively. In the cation, the observed P-N distances of 1.452(17) and 1. 481(17)Angstrom are extremely short. Taking the observed P...P distanc e of 2.928(4)Angstrom as a basis, a correlation Of the P-N-P bond angl es with the P...P distances found in the Cambridge Structural Database (CSD) suggests a P-N-P angle of ca 136 degrees rather than the observ ed angle of 173.3(11)degrees. The N and; Cl atoms especially have unus ually large displacement parameters. The thermal motion analysis shows that the 'rigid-bond' test is fulfilled. The PN4 tetrahedron, the alm ost regular P(...P)(4) tetrahedron and the NPCl3 tetrahedron appear to be rigid bodies; the [P(NPCl3)(4)](+) cation as a whole does not. Fur thermore, the non-rigid body motion cannot be explained by allowance f or intramolecular torsion. All these facts can only be explained by an exceptionally high flexibility of the P-N-P bond angle or by a preces sion motion of the N atom about the P...P connecting line with a P-N-P angle of ca 136 degrees or by some similar disorder. The anion is lin ear and symmetric [I-Cl 2.535 (3) Angstrom].