Early Metal Bimetallic Platforms for Controlled, Catalytic Dinitrogen Functionalization

With the support of the Chemical Synthesis program in the Division of Chemistry, Professor Polly L Arnold of the University of California, Berkeley, will study the structure, bonding, and reactivity of f-block and related electropositive molecules that are designed to convert atmospheric dinitrogen to ammonia and amines. One of the most important industrial processes is the conversion of atmospheric nitrogen into ammonia – the basis of nearly all nitrogen fertilizers. This is accomplished by the Haber Bosch (HB) process that is efficient but requires high temperatures and pressures. The HB process is carried out using petroleum and contributes about 2% of the worldwide carbon emissions. Chemists have spent over a hundred years trying to develop alternatives to the HB process that can operate at room temperature/pressure. This project will facilitate these reactions using catalysts based on metals that have not normally been applied to this application. During the project students will be trained in this vital field and will include members of underrepresented groups. Metalacyclic phenolate complexes of a variety of electropositive and Lewis acidic metals from the s, d, and f-block will be synthesized and their reductive small molecule activation chemistry will be evaluated. The ligands will be functionalized to enable the isolation of small and soluble dilanthanide complexes that can be crystallized and studied. Correlations with size, Lewis acidity, and one-electron redox potentials will be investigated. Open-faced complexes will make complicated dinitrogen functionalization reactivity amenable to study and will offer the opportunity to study s-block reductive activation chemistry with greater ease. Throughout the studies, a range of spectroscopic techniques will be employed to understand the path of electron flow from the source of reducing electrons to the dinitrogen molecule that activated by the electropositive metal center(s). The studies will aid our understanding of how electropositive base metals, which would not normally be able to bind or add electrons to dinitrogen, are able to support its conversion to amines. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.