Addition and Oxidation Reactivity of a Pentacoordinate Nickelacyclobutane

Nickelacyclobutanes are reactive intermediates in catalytic cycles including cyclopropanation and insertion reactions. The stoichiometric study of these intermediates has shown that their reactivity is highly influenced by the coordination environment of the nickel center. A pentacoordinated nickelacyclobutane embedded in a diphosphine pincer ligand has been shown to selectively undergo various reactions with exogenous ligands, including [2+2] cycloreversion and carbene transfer to an isocyanide. Herein, we investigate the reactivity of the pentacoordinated nickelacyclobutane towards addition and oxidation reactions. Addition reactions lead to ring-opening to form stable square planar Ni(II) compounds, while metal oxidation enhances [2+2] cycloreversion. DFT calculations are used to shed light on the different mechanisms.