ON BOND ALTERNATION IN SIMPLE SHORT-CHAIN PHOSPHAZENES

Using a standard ab initio method the optimal geometries in various co nformations and corresponding electronic structure of OP(Cl-2)NPCl3, O P(Cl-2)NP(Cl-2)NPCl3 and [Cl3PNP(Cl-2)](2)N+ are investigated at the D Z + P basis set level. The dependence of P-N bond length alternation i n these systems on the actual conformation is very small in comparison with differences implied by various ligands and/or chain lengths. The origin of P-N bond length alternation should be in breaking the molec ular symmetry (terminal O atoms) and in non-vanishing end group effect s. (C) 1998 Elsevier Science B.V.