One cannot withstand the importance of the classical concept of the oxidation state (OS). In coordination chemistry, the OS of the metal atom is typically defined as 'the charge it would bear if all the ligands were removed along with the electron pairs that were shared with the central atom''. Thus, formal OS are obtained by assigning integer number of electrons to the atoms/ligands according to some rules, which however, in complicated bonding situations, may be rather ambiguous. Oxidation states are intrinsically related to the electronic distribution, but electronic or spin populations are only a pointer of the atom's OS.We have most recently shown that the so-called effective atomic orbitals (eff-AOs) can be utilized, treating alpha and beta electrons separately, to derive the most appropriate atomic electron configurations for the atoms or molecular fragments in the molecule. Accordingly, we have introduced a simple and general way to derive effective oxidation states from the analysis of the electron density/wave function.  The method is general and it can formally be applied to any molecular system but the focus is on transition metal and organometallic chemistry for which the concept of the OS is most relevant. For practical applications we have proposed a hierarchical strategy based on the partitioning of the molecular system into fragment/ligands prior to the eff-AO analysis.We will discuss several applications of the scheme, in particular a number of intermediates and active species involved in the C-H catalytic hydroxylation carried out by a Fe(Pytacn) complex,where the presence of high-valent Fe(V) species was suggested.

Oxidation states from wavefunction analysis: Some applications

248th National Meeting (2014)

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