Crystal structure of 1, trans-3, cis-5, trans-7-tetrakis(dimethylamino)-1,3,5,7-tetrafluorotetraphosphonitrile

Abstract

Crystals of the title compound are monoclinic with a= 15·97, b= 9·27, c= 27·34 Å and β= 102°, space group C2/c with Z= 8. The atomic positions have been determined by Patterson and Fourier methods and refined by least squares to R 0·046 (1640 reflexions) from X-ray data. The conformation of the eight membered ring is close to a saddle with a mean P–N ring bond length of 1·557 Å. The PNP angles are in the range 132·7–137·4°. The dimethylamino-groups and fluorine atoms are arranged alternately above and below the mean ring plane with P–N (amine) bonds of 1·621 Å and P–F bonds of 1·566 Å. Possible factors influencing the ring conformation adopted in tetrasubstituted compounds of this type are discussed.