CAREER: Cavity-Enforced Structure and Reactivity of High-Valent Iron Oxo, Nitrosyl, and Superoxo Complexes

University Of Rochester, Rochester NY

Investigators

Abstract

With support from the Chemical Synthesis program of the Division of Chemistry, Brandon R. Barnett of the University of Rochester is investigating the synthesis of biologically-inspired iron complexes that can facilitate the breaking of strong carbon-hydrogen bonds during chemical reactions. This process is essential for the chemical industry where many important processes require the breaking of such bonds in the usual chemical feedstocks. The proposed work aims to develop ways to perform such reactions and exert fine control over the carbon-hydrogen cleavage process. These studies will further develop strategies that enable the new iron compounds to be employed as catalysts and enable the efficient conversion of feedstocks to value-added products. Synergistically, the proposed work will develop essential technical and non-technical skill sets of early career trainees and facilitate the engagement of students from underrepresented backgrounds in modern chemistry research. Additionally, this project is well suited for outreach and training of students from across multiple educational levels and communities. Beyond the incorporation of undergraduate research into this project, the PI will initiate a summer workshop series, with the aim of developing the “soft skills” of undergraduate chemistry researchers. Complementing this effort is a plan to interface inner-city high school students with the proposed research, and to incorporate virtual reality technology into the graduate level curriculum. The proposed research will undertake mechanistic investigations of C-H activation by cavity-enclosed iron(IV)-oxos, which will be greatly aided by the ability to handle these complexes at ambient and moderately elevated temperatures. Importantly, the rigid nature of the cavity is anticipated to allow for steric selectivity in C-H activation, whereby regioselectivity is determined by the steric accessibility of the bond rather than its strength. Investigations into net C-H functionalization will be initiated, as will targeted approaches that can enable catalytic turnover. As an extension of scope, the proposed work will also elucidate the effects of spatial confinement on the electronic and geometric structures of iron superoxo and nitrosyl complexes. The targeted high-valent iron complexe will be built using a ligand system that contains an organic macrocycle atop a trigonal metal-chelating platform. These are designed to surround and kinetically stabilize the reactive metal-bound fragments. The proposed work aims to exploit an interplay between the ability of the cavity to enforce conformations of low thermodynamic stability, to suppress common degradation pathways, and to control substrate approach so as to achieve regioselective C-H functionalization, with potentially broad scientific impact and application, if successful. 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.