Spin density and bonding in the CrF6 3? ion in K2Na[CrF6

Abstract

The spin-density data previously obtained by a polarised neutron diffraction experiment on K2Na[CrF6] have been reanalysed. A chemically-based model for the CrF63– ion, involving conventional atomic orbitals, has been fitted to the 92 observed magnetic structure factors using a least-squares procedure. The best refinement, with seven variable parameters, converged with the agreement factors R 0.0861, R′ 0.0579, and χ2 1.569. The spin density in chromium 3d orbitals has t2g symmetry [t2g2.66(5), eg–0.06(5)]. There is also a region of spin density centred on the chromium atom which is radially much more diffuse than the theoretical 3d orbitals and contains 0.4(1) spins parallel to the spin density of t2g symmetry closer to the chromium centre. The model indicates a small parallel spin population [0.020(5)] in each 2pπ orbital of fluorine, and an antiparallel spin population [–0.02(1)] in a fluorine 2pσ orbital. The model also indicates further antiparallel spin density along the Cr–F vector, and no significant spin population of the fluorine 2s orbital. The spin-transfer coefficients fs*, fσ*, and fπ from the present modelling [0.001(3), –0.021(12), 0.020(5) respectively] are shown to be in good agreement with the values determined from other resonance and neutron diffraction techniques.