CAS: Collaborative Research: Electronic Structure/Function Relationships Underpinning Atom Transfer Reactivity

Cornell University, Ithaca NY

Investigators

Abstract

With the support of the Chemical Structure, Dynamics & Mechanisms-B Program of the Chemistry Division, Professors Theodore Betley of the Department of Chemistry and Chemical Biology at Harvard University and Kyle Lancaster of the Department of Chemistry and Chemical Biology at Cornell are investigating the electronic structure of radicaloid ligand transition metal complexes. This collaborative project seeks to synthesize and characterize novel metal-ligand multiple bond (MLMB) systems that can deliver diverse functionalities into carbon hydrogen bond substrates. The ability to selectively incorporate functionality into unactivated carbon hydrogen bonds represents a significant advance in converting inexpensive chemical feedstocks (e.g. hydrocarbons) to value-added molecules (e.g., pharmaceutical precursors). The joint project will leverage the combined expertise of the Lancaster group to perform inorganic spectroscopy and the Betley group’s expertise in synthesis to explore periodic trends in the electronic structure and reactivity of mono- and trinuclear transition metal complexes bearing nitrenoid and nitrido ligands. The project lies at the interface of inorganic and organometallic chemistry and is therefore well suited to the education of scientists at all levels. These groups organize and participate in interactive demonstrations for students at the K-12 level from local grade schools and high schools. Here the students are invited to participate in a series of experiments and observe chemical phenomena at their laboratories. The overarching goals of the project are to probe how metal-ligand compositions and their changing oxidation levels alter the resultant physical properties and reactivity for these coordination complexes. To this end, they seek to synthesize mono- and trinuclear complexes featuring nitrenoid and nitrido functionalities to examine and harness their reaction chemistry. Thus, they aim to address the following questions: (1) How are molecular redox processes distributed along the primary redox pair in MLMB associations? (2) How do molecular redox changes of MLMBs alter oxidative group transfer processes? (3) For cluster-bound imido/nitrido complexes, how is the redox load localized? (4) For cluster-bound functionalities, can ligand hole character accumulate under oxidative processes? The target open-shell units will be designed to support a breadth of molecular oxidation states, altering the electronic structure of the MLMB or cooperatively bound moiety. They will leverage N K-edge XAS as means to probe the sub-octet character of coordinated N-donors and to quantify M–N covalency in coordination complexes. These data will be used to rationalize periodic trends in the reactivity (nucleophilic vs. electrophilic) of MLMB and cluster-based complexes across the late first transition series. 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.