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.
“Evidence for the Formation and Structure of Palladacycles during Pd-Catalyzed C–N Bond Formation with Catalysts Derived from Bulky Monophosphinobiaryl Ligands”, Angew. Chem. Int. Ed., 2006, 45(6), 925-928.