Molecular catalysts for ammonia oxidation to dinitrogen and dihydrogen are of current interest for alternative energy schemes that utilize ammonia as a fuel and/or source of hydrogen. The process requires not only the breaking of multiple strong N-H bonds but also N-N bond formation and so multiple pathways and intermediates are plausible. Recent progress in this area have focused on weaking the N-H bonds through coordination to transition metals and N-N bond formation from the resulting imido or nitrido complexes but many details and aspects of catalyst design remain to be uncovered. We have developed di and monoanionic pentadentate ligand platforms that are capable of coordinating a variety of transition metals, including Sc, Ti, V, Fe, Co, and Ni. This talk will describe aspects of both iron and molybdenum chemistry utilizing these pyridyl-pyrazolylborate ligand frameworks for coordination and activation of NH<sub>3</sub> through homolytic cleavage of N-H bonds. The characterization and reactivity of important intermediates formed will be described and potential mechanisms for the N-N bond forming step discussed.

Pentadentate ligand platforms for small molecule activation: Ammonia

ACS Spring Meeting 2021

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