Activation and functionalization of inert molecules is essential to solve some of the world’s energy problems. Important examples of these molecules include aromatic compounds, as well as small molecules such as CO, CO2, CH4, and N2. Synthetic organometallic chemists have contributed majorly to advancing this field of research by designing compounds that display unusual properties and, consequently, reactivity toward these substrates. The basis of molecular design in organometallic chemistry is the study of ancillary ligands that enable specific characteristics to various metal centers.
An important new direction in ligand design is engineering direct ligand involvement in the reactions of a specific metal. This effect may be achieved through reversible processes: weak interactions (such as hydrogen bonds), protonation/deprotonation, and redox switches. Most systems that take advantage of these processes incorporate only one type of such an interaction. Our approach, however, is unique because the ligand platform can interact with the metal center through more than one process. Chelating ferrocene ligands can invoke two desirable characteristics: (i) the ligand backbone is redox active and (ii) a weak interaction of donor-acceptor type may occur between iron and an electrophilic metal center. This approach is distinct; we take advantage of weaker interactions between the metal center and iron than those delineated by others because they become important in influencing the behavior of a metal center during the course of a reaction. This stategy led to unprecedented reactivity. As part of this project, we are still studying inverse sandwiches of arene-bridged lanthanides (Chem. Sci. 2020) and actinides (J. Am. Chem. Soc. 2020).
