Synthesis of boron, antimony, and bismuth diiminopyridine complexes and reactivity with tris(ortho-carboranyl)borane.


Diiminopyridines (DIMPYs) are a unique ligand class capable of multi-site substitution to fine tune coordination. This ligand framework offers multiple binding modes and the potential for stabilization of abnormal oxidation states due to the ligand’s inherent redox activity. The utility of DIMPY metal complexes has garnered a multitude of attention as they are capable of facilitating polymerization reactions, selective hydrogenation, hydroboration, hydrosilylation, transfer hydrogenation, methanol reforming, carbene transfer, insertion chemistry (C-N, N-H, O-H), cyclopropanation, epoxidation, and various other named reactions. More than 50 elements across the periodic table are successfully synthesized bound to the pincer DIMPY ligand. The original work in this dissertation includes generating the first known examples of boron(bidentate), antimony(tridentate), and bismuth(tridentate) complexes. This completes group 13 of the periodic table in regard to complexation, reveals that row 2 elements can in fact bind to the DIMPY ligand, and provides further insight into potential complexes to explore the aforementioned catalytic processes and reactions. Boranes are desirable synthetic tools due to their ability to catalyze transformations, hydroboration reactions, and form frustrated Lewis pairs with increasing interest in regard to their design and stability. Tris(pentafluorophenyl)borane [B(C6F5)3] has been the benchmark Lewis acid and as history shifts toward a green approach, our lab generated a fluorine-free Lewis superacid, tris(ortho-carboranyl)borane. In exploration of its catalytic capabilities, we needed to understand the stability of our newly formed catalyst with E-H functional groups. We observed that with O-H and N-H bearing substrates protodeboronation is observed forming new bis(ortho-carboranyl)borane-based products whereas with S-H, P-H, and B-H substrates, no reaction was observed. This information is invaluable when considering catalyst screening and therefore is disclosed herein.