Evidence for the Formation and Structure of Palladacycles during Pd‐Catalyzed CN Bond Formation with Catalysts Derived from Bulky Monophosphinobiaryl Ligands

The structural origins of the differences in catalytic activity observed between catalysts containing 2′-substituted and 2′,6′-disubstituted biaryl monophosphane ligands for a Pd-catalyzed CN bond-forming reaction are discussed. It is shown that palladacycle formation is avoided and optimal catalyst activity is achieved through the use of the 2′,6′-disubstituted ligands. (tAm=tert-amyl, dppe=1,2-bis(diphenylphosphanyl)ethane).