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 P1̄ space group has been determined by X-ray crystallography. The oxygen atoms of the crown ether exist in an almost ideal envelope conformation. The inorganic cyclophosphazene P3N3 ring has a non-planar envelope conformation. All endocyclic PN bond lengths are equal within experimental error with the mean value of 1.585(5) Å. The Na+ ion is coordinated by oxygen atoms from the crown ether and the water molecule 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 D3d 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 Å.