The Pt-Catalyzed Ethylene Hydroamination by Aniline: A Computational Investigation of the Catalytic Cycle DubPavel A. PoliRinaldo 2010 A full QM DFT study without system simplification and with the inclusion of solvation effects in aniline as solvent has addressed the addition of aniline to ethylene catalyzed by PtBr<sub>2</sub>/Br<sup>−</sup>. The resting state of the catalytic cycle is the [PtBr<sub>3</sub>(C<sub>2</sub>H<sub>4</sub>)]<sup>−</sup> complex (<b>II</b>). A cycle involving aniline activation by N−H oxidative addition was found energetically prohibitive. The operating cycle involves ethylene activation followed by nucleophilic addition of aniline to the coordinated ethylene, intramolecular transfer of the ammonium proton to the metal center to generate a 5-coordinate (16-electron) Pt<sup>IV</sup>−H intermediate, and final reductive elimination of the PhNHEt product. Several low-energy ethylene complexes, namely <i>trans</i>- and <i>cis</i>-PtBr<sub>2</sub>(C<sub>2</sub>H<sub>4</sub>)(PhNH<sub>2</sub>) (<b>IV</b> and <b>V</b>) and <i>trans</i>- and <i>cis</i>-PtBr<sub>2</sub>(C<sub>2</sub>H<sub>4</sub>)<sub>2</sub> (<b>VII</b> and <b>VIII</b>) are susceptible to aniline nucleophilic addition to generate zwitterionic intermediates. However, only [PtBr<sub>3</sub>CH<sub>2</sub>CH<sub>2</sub>NH<sub>2</sub>Ph]<sup>−</sup> (<b>IX</b>) derived from PhNH<sub>2</sub> addition to <b>II</b> is the productive intermediate. It easily transfers a proton to the Pt atom to yield [PtHBr<sub>3</sub>(CH<sub>2</sub>CH<sub>2</sub>NHPh)]<sup>−</sup> (<b>XX</b>), which leads to rate-determining C−H reductive elimination through transition state <b>TS(XX−L)</b> with formation of the σ-complex [PtBr<sub>3</sub>(κ<sup>2</sup>:<i>C</i>,<i>H</i>-HCH<sub>2</sub>CH<sub>2</sub>NHPh)]<sup>−</sup> (<b>L</b>), from which the product can be liberated via ligand substitution by a new C<sub>2</sub>H<sub>4</sub> molecule to regenerate <b>II</b>. Saturated (18-electron) Pt<sup>IV</sup>−hydride complexes obtained by ligand addition or by chelation of the aminoalkyl ligand liberate the product through higher-energy pathways. Other pathways starting from the zwitterionic intermediates were also explored (intermolecular N deprotonation followed by C protonation or chelation to produce platina(II)azacyclobutane derivatives; intramolecular proton transfer from N to C, either direct or assisted by an external aniline molecule) but all gave higher-energy intermediates or led to the same rate-determining <b>TS(XX−L)</b>.