Modellrechnungen zum Gegenioneneinfluß auf die kationische Polymerisation; Geometrieoptimierung und Verhalten gemischter Halogenoantimonate SbCl_nBr

Abstract

Model Calculations on the Counterion Effect in the Cationic Polymerization; Geometry Optimization and Behaviour of the Mixed Halogenoantimonates SbClnBr −n−6. The CNDO/2 method including geometry optimization with respect to the energy has been applied to calculate the structure and the electronic properties of the complex anions SbClnBr −6−n. Independently on the composition of the anions the bond lengths Sb‐X (X = Cl, Br) remain those of the pure antimonates. The HOMOs are delocalized over the ligand sphere. They mainly contain components of Br and are lifted by increasing Br amount. The LUMOs have central atom character and are lowered by Br. Charge distribution and Wiberg bond indices indicate extra easy cleavage of the Sb‐Br bond if Cl holds a trans position to Br. The computed data agree with spectral properties, the acceptor behaviour and the decay trend of the antimonates SbClnBr −6−n.