Computational Analysis of the Intramolecular Oxidative Amination of an Alkene Catalyzed by the Extreme π-Loading N-Heterocyclic Carbene Pincer Tantalum(V) Bis(imido) Complex

The extreme π-loading of a (CCC-NHC) pincer Ta(V) bis(imido) complex was previously reported. This complex catalyzes the cyclization of α,ω-aminoalkenes (2,2-diphenylpent-4-en-1-amine) to produce three different products in varying proportions: cyclic imine from oxidative amination (OA), reduction product (RP) from hydrogenated substrate, and hydroamination (HA) (Helgert, T. R.; Organometallics 2016, 35, 3452). Various plausible pathways for the reactions generating cyclic imine product from oxidative amination, the reduction of substrate from hydrogen transfer, the cyclic amine product from hydroamination, and the dehydrogenation of hydroamination product were evaluated using density functional theory computations. RP is the thermodynamic product, while OA and HA are the kinetic products, with HA being lower in energy than OA. Multiple pathways for the generation of OA product were examined. The lowest free energy of activation (ΔG⧧) of the rate-determining-step (RDS) during the oxidative amination was c...