Evidence for an orbitally degenerate ground state in hexa-ammine-cobalt(III) hexacyanoferrate(III) from Mössbauer spectroscopy

Abstract

The compound [Co(NH₃)₆][Fe(CN)₆] has been found to have trigonal symmetry at the iron site. Mössbauer-spectroscopic measurements show that the ground state of the low-spin iron(III) is an orbitally degenerate ²E_g state. The effective spin–orbit coupling parameter is λ≃–100 cm^–1, and it is shown that non-bonding 3d orbitals of t_2g symmetry are expanded relative to the free ion under the influence of a cubic ligand field.