Boron-Doped Acenes for the Redox Activation of Small Molecules:

Organoboranes have emerged as an important ligand class in transition metal chemistry. As Lewis acids, organoboranes engage in Z-type or retrodative interactions with electron-rich transition metals, and the unique characteristics of these interactions can enable new catalysis and/or the stabilization of electronically unusual species. We have developed a class of ligands based on diboraanthracene that feature such interactions. In particular, they enable the stabilization of a unique complex of gold(–1), or auride, that can be reversibly oxidized to the analogous gold(+1) complex via an intermediate state consisting of a borane radical anion and gold(+1) center. Interestingly, this auride species reacts primarily at the boron sites via either nucleophilic attack or cycloaddition chemistry to enable the activation of a wide range of substrates including H₂O, CO₂, and organic carbonyls. In some cases, transformed substrates can be liberated to regenerate the gold complex. We will also discuss the extension of this chemistry to a novel platinide species (Pt(-2)) as well as second generation ligand platforms.