Highly sterically demanding phosphine ligands have proven to be essential in enabling many efficient transformations catalyzed by various late transition metals. The benefits of these ligands in homogenous gold catalysis have only recently been revealed. Below are the structures of two such sterically hindered gold catalysts, BrettPhosAuNTf2 (1) and Me4t-BuXPhosAuNTf2 (2), first reported by Prof. Liming Zhang.
Several studies by Zhang show that cationic Au(I) complexes derived from highly hindered and electron-rich ligands such as BrettPhos and Me4t-BuXPhos are more effective catalysts than those typically derived from triarylphosphines and N-heterocyclic carbenes. Steric congestion around the gold center imposed by these ligands not only makes the electrophilic metal more stable, leading to longer catalyst lifetime, but also facilitates challenging reactions by limiting side reactions.
*Special thanks to Prof. Liming Zhang for contributing this technical spotlight.
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