Crystal and molecular structure of [octakisdimethylaminocyclotetraphosphazene]tetracarbonyltungsten

Abstract

Crystals of the title compound are monoclinic, a= 18·274(22), b= 18·594(24), c= 10·533(14)Å, β= 90·39(10)°, Z= 4, space group P2₁/n. The structure was determined from diffractometer data by Patterson and Fourier methods, and refined by full-matrix least-squares methods to R 0·071 for 2372 observed reflexions. The phosphonitrile is co-ordinated to tungsten through a ring nitrogen atom and an exocyclic dimethylamido-nitrogen atom. The co-ordination geometry about tungsten is distorted octahedral with the nitrogen atoms of the phosphonitrile occupying cis-positions and N–W–N angle 65·4°. The bond-length variations in the phosphonitrilic ring caused by co-ordination are explained in terms of π-bonding theory.