Theoretical study of the deformation densities of d electrons in K2[PdCl6] and K2[PtCl6] crystals

Abstract

Aspherical distributions of the d electrons in dipotassium palladium hexachloride, K2[PdCl6], and dipotassium platinum hexachloride, K2[PtCl6], crystals were analyzed by theoretical calculations. Hartree–Fock and configuration interaction calculations were performed for [PdCl6]2− and [PtCl6]2− with and without taking into account the Madelung potentials, using a model potential method. The major relativistic effects were incorporated in the model potentials for Pd and Pt. The deformation-density maps calculated were similar to those given by the X-ray diffraction method. The theoretical result suggested that the positive peaks on the threefold axes and the negative peaks on the metal—Cl bond axis correspond to the excess d electrons (4d of Pd and 5d of Pt) in the t 2g (dxy, dxz, dyz ) orbitals and the electron deficiency in the eg (dz 2,dx 2− y 2) orbitals, respectively. The positive and negative peak heights were calculated to be +1.8 and −0.8 e Å−3 for [PdCl6]2− and +1.2 and −0.6 e Å−3 for [PtCl6]2−. The effective charges and effective radii of Pd and Pt, and the number of electrons in the t 2g , eg and t 1u orbitals, were calculated by direct integration. The effects of the Madelung potential and electron correlation on the charge distributions of [PdCl6]2− and [PtCl6]2− were also analyzed.