On the geometrical and electronic structure of the hexahydroxochromate(III) anion

Abstract

Restricted Hartree–Fock and ligand-field configuration interaction calculations have been made on two structures of the [Cr(OH)₆]^3– anion. The bent structure (bond angle for the CrOH fragments 109°) was found in all circumstances to be significantly more stable than the O_h conformation (all CrOH fragments linear). The electronic effects within the anion are predominant and favour the bent structure, although the electrostatic repulsive interaction of the central cluster with the second co-ordination sphere favours the linear structure. The calculated ligand-field transitions predict a relatively small trigonal splitting of the T states (1500 cm^–1), the S₆ structure exhibiting a better agreement with the experimental transition energies.