The Role of Inverted Ligand Field in the Electronic Structure and Reactivity of Octahedral Formal Platinum (IV) Complexes**

Abstract

Platinum complexes are ubiquitous in chemistry and largely used as catalysts or as precursors in drug chemistry, thus a deep knowledge of their electronic properties may help in planning new synthetic strategies or exploring new potential applications. Herein, the electronic structure of many octahedral platinum complexes is drastically revised especially when they feature electronegative elements such as halogens and chalcogens. The investigation revealed that in most cases the five d platinum orbitals are invariably full, thus the empty antibonding orbitals, usually localized on the metal, are mainly centered on the ligands, suggesting a questionable assignment of formal oxidation state IV. The analysis supports the occurrence of the Inverted Ligand Field theory in all cases with the only exceptions of the Pt‐F and Pt‐O bonding. The trends for the molecular complexes are mirrored also by the Density of States plots of extended structures featuring octahedral platinum moieties in association with chalcogens atoms. Finally, the oxidative addition of a Se‐Cl linkage to a square platinum complex to achieve an octahedral moiety has been revised in the framework of the Inverted Ligand Field.

Oxidation States: Intrinsically Ambiguous?

“…Manca and co-workers recently computationally investigated the oxidative addition of PhSeCl to a square-planar formal d 8 Pt(II) complex (Figure ), resulting in an octahedral formal d 6 Pt(IV) species, as previously reported experimentally . Similarly to [Cu(CF 3 ) 4 ] − , Manca and co-workers describe the ligand field of the square-planar formal d 8 Pt(II) reactant complex as inverted, and it is therefore said to be physically (2 e – ) reduced, i.e., d 10 Pt(0).…”

“…Similarly to [Cu­(CF 3 ) 4 ] − , Manca and co-workers describe the ligand field of the square-planar formal d 8 Pt­(II) reactant complex as inverted, and it is therefore said to be physically (2 e – ) reduced, i.e., d 10 Pt(0). Interestingly, their application of ILF theory to the octahedral product complex differs from Lancaster’s treatment of octahedral complexes of group 10 transition metals (see Supporting Information for details): for this formal d 6 Pt­(IV) species, Manca and co-workers propose a doubly inverted (4 e – reduced) d 10 Pt(0) description. Through their ligand field analysis, they conclude that the metal center “maintains the d 10 configuration” throughout the reaction, so the electron holes created by the complex’s oxidation “are mainly centered on the ligands” .…”

“…Interestingly, their application of ILF theory to the octahedral product complex differs from Lancaster’s treatment of octahedral complexes of group 10 transition metals (see Supporting Information for details): for this formal d 6 Pt­(IV) species, Manca and co-workers propose a doubly inverted (4 e – reduced) d 10 Pt(0) description. Through their ligand field analysis, they conclude that the metal center “maintains the d 10 configuration” throughout the reaction, so the electron holes created by the complex’s oxidation “are mainly centered on the ligands” . These conclusions collide with the traditional understanding of oxidative addition reactions of transition metal complexes.…”