N-substituted Aminobiphenyl Palladacycles Stabilized by Dialkylterphenyl Phosphanes: Preparation and Applications in C[sbnd]N Cross-coupling Reactions

Abstract

Neutral and cationic N-methyl- and N-phenyl-2-aminobiphenyl methanesulfonate palladacycles stabilized with dialkylterphenyl phosphanes have been prepared and characterized. Neutral structures are favored with the less bulky phosphane PMe2ArXyl2, L1, while more sterically demanding ligands PiPr2ArXyl2, L3, and PCyp2ArXyl2 (Cyp = cyclopentyl), L4, lead to cationic complexes in which the phosphane exhibits a bidentate κ1-P, η1-Carene coordination mode involving one of the ipso carbon atoms of a flanking terphenyl aryl ring. The complexes were evaluated for activity in C[sbnd]N cross-coupling reactions and [Pd(N-methyl-2-aminobiphenyl)L4](OMs) (OMs = mesylate) was identified as the most efficient precatalyst, facilitating the coupling of aryl chlorides with secondary and primary amines and indoles.