Developing selective cross coupling methodology using nickel catalysis
Palladium complexes have long been the go-to catalyst for use in cross coupling reactions between organohalides and organometallic reagents due to the ease with which catalyst activity can be tuned, enabling chemo- and regioselectivity. Contrastingly, nickel catalysis is not as well developed, but offers a more sustainable alternative while exhibiting similar reactivity. Within this current study, modulation of chemoselectivity for the oxidative addition of 1-(pseudo)halonaphthalenes to nickel complexes though ligand selection was explored, computationally and experimentally. Density Functional Theory was used to calculate the Gibbs free energy of activation and Gibbs free energy of the oxidative process, whereas kinetic analysis was employed to examine the effect of the ligand used on the rate constant. Overall, the data presented herein provides a framework for selecting appropriate ligands to achieve desired chemoselectivity, as data concerning the reactivity trends for the halides and ligands is described. However, the kinetic studies within this project were significantly more limited in scope, partly due to the inability to synthesise several of the planned nickel complexes and restricted laboratory access resulting from COVID-19. Despite this, unexpected results were obtained, highlighting the potential for unusual selectivity not indicated in the DFT studies.