Determination of the effective charges of atoms in complexes from the x-ray absorption spectra

Summary

• 1. The physical basis of a method for calculating the x-ray K-absorption spectra of atoms in molecules and in complex molecules or ions with an approximate central symmetry of the field around the absorbing atom has been examined.

• 2. It has been shown that it is possible to determine the effective charge of an atom and to calculate approximately the radius of the sphere within which this charge is distributed.

• 3. The method is used for the calculation of the effective charge of the atoms of transition metals in complicated complex ions and molecules. The possibility of determining from the x-ray spectra the effective radii of atoms and the lengths of bonds has been shown.

• 4. The results of calculation definitely indicate that, in the compounds investigated, there are no multiply charged ions (even for atoms in their highest valency state). The tendency to a sharp decrease of the charge with an increase of the valency of an atom has been noted.

• 5. The determination of the effective charge of atoms of transition elements in aromatic complexes has shown that the type of bond in this class of compounds is mainly covalent, with the exception of (C₅H₅)₂ Mn which has ionic bonds. It has been shown that the bond of Mn to C₅H₆ in C₅H₅ Mn(CO)₃ is of the ferrocene type.