Change of the crown ether geometry by complexation in tetrapyrrolidinyl PNP-lariat ether. Crystal structure of the complex of tetrapyrrolidinyl PNP-lariat ether with sodium iodide

The crystal and molecular structure of the title compound, C24H50IN7NaO6P3, crystallizing in P (1) over bar space group has been determined by X-ray c rystallography, The oxygen atoms of the crown ether exist in an almost idea l envelope conformation. The inorganic cyclophosphazene P3N3 ring has a non -planar envelope conformation. All endocyclic P-N bond lengths are equal wi thin experimental error with the mean value of 1.585(5) Angstrom. The Na+ i on is coordinated by oxygen atoms from the crown ether and the water molecu le but not by the cyclophosphazene nitrogen atom. The O-P-N-P-O part of the 16-membered ring is flexible. The crown ether part of the 16-membered ring adopts approximately D-3d symmetry. Complex mean cavity radii are close to effective ionic radii. There is no coordination bond between nitrogen and metals with effective ionic radii smaller than 2.3 Angstrom. (C) 2001 Elsev ier Science B.V. All rights reserved.