Phosphazene Ring Research Articles

An improved determination of the crystal structure of hexachlorocyclotriphosphazene (phosphonitrilic chloride)

By use of X-ray diffractometer intensity data, the crystal structure of hexachlorocyclotriphosphazene, N3P3Cl6, has been refined to R 0·048 for 1222 reflexions. The phosphazene ring is almost planar but there are small deviations from planarity of up to 0·04 A. The P–N bonds are all equal in length, 1·581 A(σ 0·004–0·005 A) and the P–Cl bond lengths range from 1·991–1·995 A(σ 0·004–0·005 A). The mean N–P–N angle in the ring (118·4°) is significantly smaller than the mean P–N–P angle (121·4°). There are only slight deviations from the ideal molecular symmetry D3h(m2). An analysis of the atomic thermal vibrations shows that at 25°± 2 °C the molecule is undergoing translational vibrations with root-mean-square amplitudes of 0·17–0·19 A combined with angular oscillations about the molecular axes whose root-mean-square amplitudes are 3·4–3·6°.

Crystal and molecular structure of octamethoxycyclotetraphosphazene

Crystals of octamethoxycyclotetraphosphazene, N4P4(OMe)8, are orthorhombic, a= 17·85, b= 16·55, c= 13·06 Å, space group Pbca with Z= 8. The atomic positions have been determined by least-squares refinement from X-ray diffraction data, the final R being 0·078 for 1305 reflexions. The eight-membered phosphazene ring has a slightly distorted saddle shape with a mean P–N bond length of 1·57 Å and mean angles N–P–N 121 and P–N–P 132°. The phosphorus atoms are almost coplanar but the nitrogen atoms are alternately 0·5 Å above or below their plane. The mean length of the P–O bond, 1·58 Å, and the mean P–O–C angle, 121°, suggest π-bonding between phosphorus and oxygen atoms although steric repulsions appear to be the main factor governing the orientation of the methoxy-groups.

Crystal and molecular structure of chloro[dodeca(dimethylamino)-cyclohexaphosphazene-NNNN]-copper(II) dichlorocuprate(I), [N6P6(NMe2)12CuIICl]+ CuICl2 ?

Crystals of [N6P6(NMe2)12CuIICl]+Cu ICl2– are monoclinic, a= 19·352(8), b= 8·690(6), c= 14·069(7)Å, β= 91·04(4)°, Z= 2, space group P2/n. The structure was determined with Mo-Kα diffractometer data from Patterson and electron-density maps; full-matrix least-squares refinement reduced R to 0·083 for 1103 observed reflexions. The cation is situated on a crystallographic C2 axis, and has the copper(II) atom bonded to four nitrogen atoms of the phosphazene ring and to one chlorine atom, in a distorted square-pyramidal co-ordination, with the chlorine atom in the apical position. There are two distinct P–N bond distances, 1·62 and 1·55 Å, which are explicable in terms of π-bonding theory. The CuICl2+ ion is also situated on a crystallographic C2 axis, and is linear, with Cu–Cl 2·11 Å.

A new conformation of the eight-membered phosphazene ring: X-ray crystallographic evidence

The cis-isomer of 2,4,6,8-tetrachloro-2,4,6,8-tetraphenylcyclotetraphosphazatetraene (m.p. 190°) has been shown by X-ray crystal-structure analysis to contain molecules in which the eight-membered phosphazene ring has a somewhat flattened crown conformation.