Nature of distortion isomers of hexacoordinate copper complexes

The question of the structure of complexes of the type trans-Cu/sup II/ (NH/sub 3/)/sub 2/Hal/sub 4/ has been studied from the point of view of the theory of the Jahn-Teller effect. It has been shown that the existence of two isomers with D/sub 4h/ and D/sub 2h/ symmetry in such complexes can be explained when the linear and quadratic terms in the vibronic coupling operator and the differences between the ligands in the first coordination sphere of the metal are taken into account without relying on any intermolecular interactions. An explanation for the experimentally observed interatomic distances in the chainlike compounds with Hal = Br and Cl requires consideration of the interaction of the Jahn-Teller e/sub g/* orbitals with the higher lying ..cap alpha../sub 1g/* state.