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The oxidative addition/reductive elimination of polar molecules such as methyl iodide at late metal centers has a strongly supported SN2 mechanism for many key organometallic complexes, including important industrial catalysts. In the reductive elimination direction, it is proposed that a ligand initially dissociates, typically a halide, followed by subsequent nucleophilic attack at the ligand trans to the now vacant site. The prevailing view is the metal reduction occurs upon transferring the electrophile in the SN2 step. Herein, we report the use of an ensemble of computational techniques to characterize the electronic structure of the reactants and intermediates along this reductive elimination pathway. These calculations demonstrate, unexpectedly, that the initiating loss of an anionic ligand from the octahedral highly oxidized structure leads to an electronic rearrangement that shifts electron density from the apical ligand back toward the metal resulting in an inversion of the electron flow between the metal and apical ligand. The anisotropic shift in electron density to the metal disproportionately affects the apical position, which is best described as a Pt → Me dative bond. With this Pt → Me bonding description, our interpretation of the IUPAC oxidation state formalism would assign the intermediate as PtII. Although counterintuitive, the formal and functional reduction of the metal thus occurs upon halide dissociation. 

Tuning metal–ligand cooperativity to effect monodentate ligand charge has not been widely studied outside of metal hydrides. Here, we explore how metal coordination sphere can be manipulated to invert the polarization of Pt–I bonds and generate electrophilic behavior at I. Coordinative unsaturation trans to I is key to inverting the natural Pt–I bond polarization and is utilized to enable the electrophilic behavior of I in cationic platinum iodide complexes. The synthesis and characterization of the iodination products of reacting biscyclometalated arylpyridines (Pt(phpy)2) with I2 and R3PI+ are reported. Abstracting iodide from Pt(phpy)2I2 yields a putative 5-coordinate Pt intermediate capable of transferring iodonium to a bulky phosphine. These experimental results are further assessed through charge calculations and energy decomposition analysis (EDA).