An investigation of the electron density of a Jahn-Teller-distorted Cr(II) cation: the crystal structure and charge density of hexakis(acetonitrile-κN)chromium(II) bis(tetraphenylborate) acetonitrile disolvate.

Abstract

In the crystal structure of the title homoleptic Cr(II) complex, [Cr(CH3CN)6](C24H20B)2·CH3CN, the [Cr(CH3CN)6](2+) cation is a high-spin d(4) complex with strong static, rather than dynamic, Jahn-Teller distortion. The electron density of the cation was determined by single-crystal X-ray refinements using aspherical structure factors from wavefunction calculations. The detailed picture of the electronic density allowed us to assess the extent and directionality of the Jahn-Teller distortion of the Cr(II) cation away from idealized octahedral symmetry. The topological analysis of the aspherical d-electron density about the Cr(II) cation showed that there are significant valence charge concentrations along the axial Cr-N axes. Likewise, there were significant valence charge depletions about the Cr(II) cation along the equatorial Cr-N bonds. These charge concentrations are in accordance with a Jahn-Teller-distorted six-coordinate complex.