Base-Metal Complexes for Challenging Organometallic Transformations

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This proposal describes approaches to render sustainable 1st-row transition metals, such as nickel and cobalt, as catalysts for applications such as the functionalization of C-H, C-F and C-O bonds. The short term goals of the projects involve identification of new ways to render these metals reactive towards traditionally inert bonds. Approaches to this include using ligand design or identifying new mechanisms for bond activation. The long term goal of each project is the commercial application of these catalytic technologies in fields such as pharmaceutical synthesis and biomass conversion. The atom-economic relatively green conversion of traditionally inert C-H bonds to functional groups has been achieved by a number of metal-catalyzed systems in the past decades. Complexes of the expensive 3rd-row late transition metals, such as iridium and platinum, are commonly used in these conversions, due to the strong bonds these elements form to both carbon and hydrogen, which aids in cleaving strong C-H bonds. Comparatively, complexes of nickel are at an extreme thermodynamic disadvantage in these reactions, but nickel has the distinct advantage of being on the order of 10000 times cheaper, due to its relative abundance. Our research suggests that not only can nickel complexes also activate strong C-H bonds, they can also perform catalytic C-H bond transformations that are unprecedented and perhaps unique to these systems. Our current goals are to fully understand the mechanism and scope of these reactions. Similar to C-H bond activation, the activation of C-F and C-O bonds are also problematic for both kinetic and thermodynamic reasons. We hope to do a thorough study of C-F bond activation by nickel complexes to gain insight into how the mechanism and thermodynamic parameters of these reactions are influenced by ancillary ligand choices. The end goal is a rational approach to both C-F bond activation and catalytic C-F bond formation for pharmaceuticals or radionuclide use. The activation of C-O bonds is related to C-F bond activation, and has application in both synthesis and biomass conversion to fuels or fine chemicals.