Facing the Challenges of Borderline Oxidation State Assignments Using State-of-the-Art Computational Methods

Martí Gimferrer; Jeroen Van der Mynsbrugge; Alexis T Bell; Pedro Salvador; Martin Head-Gordon

doi:10.1021/acs.inorgchem.0c02405

Facing the Challenges of Borderline Oxidation State Assignments Using State-of-the-Art Computational Methods

Inorg Chem. 2020 Oct 19;59(20):15410-15420. doi: 10.1021/acs.inorgchem.0c02405. Epub 2020 Oct 8.

Authors

Martí Gimferrer¹, Jeroen Van der Mynsbrugge², Alexis T Bell², Pedro Salvador¹, Martin Head-Gordon^{3

4}

Affiliations

¹ Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Maria Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain.
² Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, California 94720, United States.
³ Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.
⁴ Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.

PMID: 33030893
DOI: 10.1021/acs.inorgchem.0c02405

Abstract

The oxidation state (OS) of metals and ligands in inorganic complexes may be defined by carefully curated rules, such as from IUPAC, or by computational procedures such as the effective oxidation state (EOS) or localized orbital bonding analysis (LOBA). Such definitions typically agree for systems with simple ionic bonding and innocent ligands but may disagree as the boundary between ionic and covalent bonds is approached, or as the role of ligand noninnocence becomes nontrivial, or high oxidation states of metals are supported by heavy dative bonding, and so on. This work systematically compares IUPAC, EOS, and LOBA across a series of complexes where OS assignment is challenging. These systems include high-valent transition metal oxides, transition metal complexes with noninnocent ligands such as dithiolate and nitrosyl, metal sulfur dioxide adducts, and two transition metal carbene complexes. The differences in OS assignment by the three methods are carefully discussed, demonstrating the synergy between EOS and LOBA. In addition, a clarity index for LOBA OS assignments is introduced that provides an indication of whether or not its predictions are close to the ionic-covalent boundary.