OBSERVED AND THEORETICAL DEFORMATION DENSITY STUDIES OF THE AZIRIDINYL, BENZENE, AND PHOSPHAZENE RINGS IN THE CRYSTAL-STRUCTURE OF THE BENZENE SOLVATE OF HEXAAZIRIDINYLCYCLOTRIPHOSPHAZENE

The crystal structure and the electron density of the benzene solvate of hexaaziridinyldyclotriphosphazene have been analyzed using single-c rystal X-ray diffraction at 200 K with Mo K alpha radiation and an are a detector to a resolution of sin(theta(max)/lambda = 1.25 Angstrom(-1 ); 17 639 measured reflections gave 4596 unique reflections with R, = 0.027. A multipole atomic density model was fitted to 4038 reflections with I > 3 sigma(I) to give an R(F-2) = 0.039. The dynamic deformatio n densities of the trapped benzene molecule, the two unique three-memb ered aziridinyl rings, and the phosphazene ring have all been examined and are reported here for the first time. Those of the benzene and th e aziridinyl groups conform to the expected density for these systems. These observations are used to validate the observations of the dynam ic deformation density in the phosphazene ring. The observed dynamic d eformation density in this ring corresponds to the density for the pi/ pi' models with conjugation from a phosphorus atom, through a ring nit rogen atom to a second phosphorus, but with nodes at each of the phosp horus atoms. Theoretical dynamic deformation densities, derived from a b initio calculations and carried out on the simple aziridinyl and pho sphazene rings, closely resemble the observed deformation densities.