Orthogonal Nanoparticle Catalysis with Organogermanes

• Published in: Angewandte Chemie International Edition 2019-12, Vol.58 (49), p.17788-17795
• Main Authors: Fricke, Christoph, Sherborne, Grant J., Funes‐Ardoiz, Ignacio, Senol, Erdem, Guven, Sinem, Schoenebeck, Franziska
• Format: Article
• Language: English
• Subjects: Aromatic compounds; Catalysis; Catalysts; chemoselectivity; Computer applications; Coupling (molecular); Cross coupling; density functional calculations; germanium; Halides; Nanoparticles
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201910060

Although nanoparticles are widely used as catalysts, little is known about their potential ability to trigger privileged transformations as compared to homogeneous molecular or bulk heterogeneous catalysts. We herein demonstrate (and rationalize) that nanoparticles display orthogonal reactivity to molecular catalysts in the cross‐coupling of aryl halides with aryl germanes. While the aryl germanes are unreactive in LnPd0/LnPdII catalysis and allow selective functionalization of established coupling partners in their presence, they display superior reactivity under Pd nanoparticle conditions, outcompeting established coupling partners (such as ArBPin and ArBMIDA) and allowing air‐tolerant, base‐free, and orthogonal access to valuable and challenging biaryl motifs. As opposed to the notoriously unstable polyfluoroaryl‐ and 2‐pyridylboronic acids, the corresponding germanes are highly stable and readily coupled. Our mechanistic and computational studies provide unambiguous support of nanoparticle catalysis and suggest that owing to the electron richness of aryl germanes, they preferentially react by electrophilic aromatic substitution, and in turn are preferentially activated by the more electrophilic nanoparticles. Palladium nanoparticles display orthogonal reactivity to molecular catalysts in the cross‐coupling of aryl halides with aryl germanes. While aryl germanes are unreactive under LnPd0/LnPdII catalysis, they display superior reactivity under Pd nanoparticle conditions. Owing to their electron richness, aryl germanes preferentially react by electrophilic aromatic substitution, and in turn are preferentially activated by the more electrophilic nanoparticles.