Question

Inorganic questions

1.For each possible electron configuration in an octahedral field, determine which configurations are potentially Jahn-Teller active.

2.Consider the trans-dichlorotetraaminocobalt(II) molecule. Use the concepts of crystal field theory and ligand field theory to determine the geometry of the ion. In other words, is it octahedral?

Answer 1

1. The Jahn–Teller theorem states that a non-linear molecule with a spatially degenerate electronic ground state will undergo a geometrical distortion to remove the degeneracy and lower the overall energy of the system. In principle, Jahn–Teller distortions are possible for many transition-metal ions; in practice, however, they are observed only for systems with an odd number of electrons in the e_g orbitals such as the Cr²⁺ and Cu²⁺ ions.

Jahn–Teller distortions are most important for d⁹ and high-spin d⁴ complexes; the distorted system is more stable than the undistorted one.