Evidence for the formation and structure of palladacycles during Pd-catalyzed C-N bond formation with catalysts derived from bulky monophosphinobiaryl ligands

(Chemical Equation Presented) 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). © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.