THEORETICAL-STUDY OF ELECTRON-DENSITY TOPOLOGIES AND ATOMIC POPULATIONS IN SELECTED IRON COMPLEXES

Ab initio Hartree-Fock multiconfigurational self-consistent-field and configuration-interaction calculations have been performed for the hexaaqua and hexacyanide complexes of Fe(II) and Fe(III). The electron density and the bonding is analyzed using a topological method, considering bond paths, critical points, the Laplacian of the density, and charges found by integration. Differences due to different ligands, different oxidation steps, and high and low spin are discussed. A very special topology was found for the 1A(g) state of Fe(H2O)6(2+), where there are two bond paths and rive critical points for each Fe-O bond. No conspicuous shapes were found for the Fe basins, and the assignment of atomic charges to Fe using this method is not strikingly different from what is found by Mulliken populations. By none of the methods do gross charges and oxidation steps correlate well.