Crystal structure of trichloro(octamethylcyclotetraphosphonitrilium)-copper(II), [(NPMe2)4H] CuCl3

Crystals of [(NPMe2)4H]CuCl3 are orthorhombic, a= 15·701, b= 17·728, c= 14·526A, Z= 8, space group Pbca. The structure was determined with Mo-Kα counter data by Patterson, electron-density, and least-squares methods, to R 0·097 for 1670 observed reflexions. The structure consists of an eight-membered phosphonitrilic ring, in a ‘tub’ conformation, with a proton and a CuCl3 group covalently bonded to opposite nitrogen atoms. There are four distinct pairs of NP bonds, the lengths, starting at the nitrogen bonded to copper, being 1·63, 1·60, 1·56, and 1·67 A. These differences, and corresponding valency angle variations, can be interpreted in terms of π-bonding theories. The ‘tub’ shape of the ring is probably a result mainly of steric requirements. The copper atom co-ordination may be described as distorted square planar. A feature of the intermolecular contacts is a N–H ⋯ Cl hydrogen bond (3·20 A).