Bond Activation by Unconventional Lewis Pairs

[摘要] Frustrated Lewis pairs are powerful tools for bond heterolysis in organic and inorganic chemistry. In these systems, an electron-deficient Lewis acid and an electron-rich Lewis base synergistically polarize strong bonds in substrate molecules, forming electrophilic and nucleophilic fragments that can be used in subsequent reactions. However, synergistic bond heterolysis is only possible when reactive Lewis acids and bases are unable to form inert Lewis acid/base adducts with each other.In this monograph, I used a broad definition of what constitutes Lewis acids and bases to design unconventional frustrated Lewis pairs that address significant challenges in catalysis, bioinorganic chemistry, and organofluorine chemistry. First, transition metal catalysts incorporating pendent oxyanion bases were prepared that mediate metal/ligand cooperative H2 and HBPin heterolysis, followed by transfer of electrophilic proton or boryl equivalents and nucleophilic hydrides to nitriles, carbonyl compounds, or carbon dioxide. Next, a reduced Fe(0) center was used as a Lewis base in combination with triorganoborane and alkali cation Lewis acids to synergistically weaken and polarize the N-N triple bond in N2. Polarization of N2 was then exploited in selective -N, rather than -Fe, protonation reactions. Finally, a weak borazine-based Lewis acid was used in combination with strong bases to deprotonate HCF3 and HCF2R. The incipient CF3- and CF2R- anions, typically highly unstable, were captured and stabilized by borazine to form stable fluoroalkylation reagents, which react like traditional Grignard reagents. Overall, these systems demonstrate the generality and utility of the frustrated Lewis pair concept.

[发布机构] University of Michigan

[效力级别] Nitrogenase

[关键词] Fluoroform;Nitrogenase;Difluoromethylarylation;Chemistry;Science;Chemistry