Exploiting Unique Reactivity of Boryl-centered Pincer Complexes of Transition metals

Texas A&M University, College Station TX

Investigators

Abstract

With the support of the Chemical Synthesis (SYN) program in the Division of Chemistry Professor Oleg Ozerov of Texas A&M University is studying the development of complexes of late transition metals that contain boron-metal bonds, and the exploitation of the boron-metal synergy in selective transformations of nitrogen-containing organic molecules. Selective activation and transformation of chemical bonds, especially carbon-hydrogen bonds, is key to the efficient utilization of available chemical resources in organic synthesis. The work in the Ozerov group will explore the nuanced fundamental aspects of the interactions of boron-metal units with carbon-hydrogen and other bonds, and will explore the potential for catalytic transformations with unusual selectivity. The project will serve as a vehicle for training graduate and undergraduate students in modern organometallic synthesis and a variety of characterization techniques. It will benefit from a network of US and international collaborators, including faculty at primarily undergraduate institutions, and from outreach activities in the state of Texas aimed at increasing participation and interest in organometallic chemistry. This project will explore the fundamental reactivity of new transition metal complexes supported by tridentate “pincer” ligands anchored by the boryl donors forming a central boron-metal bond. These central boryl moieties offer unique possibilities beyond the more conventional C/N/P donors, in part because of the availability of an empty p-orbital on boron. On the fundamental side, the work will aim to create new understanding of the overall reactivity and the role of Lewis-acidic boryl ligands in bond-breaking and bond-making steps. In particular, investigations will target the mechanistic role of B in transferring the organic fragments to and from the transition metal and the novel mechanism for C-H (and possibly other C-Element) bond formation at boron, assisted by the transition metal. The fundamental insight will be leveraged for the optimization of ligand design and the development of catalytic methods of C-H functionalization of nitrogenous heterocycles that rely on the selectivity principles specific to the boryl-metal unit. The core studies with Rh and Ir as the transition metals in the boryl-metal partnership are expected to be extended to Co in group 9, and to Fe/Ru/Os in group 8. Access to the desired variety of boryl pincer ligands will require synthetic innovation that should become useful to a broad set of practitioners of transition metal chemistry. The proposed work will benefit significantly from the synergy between theoretical and experimental studies to navigate the efficacy of the various sub-classes of ligands. 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.