Substituent effect of diimino-palladium (II) pincer complexes on the catalysis of Sonogashira coupling reaction

Three series 5-Z-2-Br-isophthalaldimines were treated with Pd2(dba)3 to afford the corresponding pincer complexes. Sonogashira coupling demonstrated that the PdII-NCN-NO2 pincers normally exhibited a higher catalytic activity than PdII-NCN-But, PdII-NCN-H pincers. The structural comparison indicated that the both the group NO2 at the position-4 of palladium (II) and Me group at the aniline ring might be responsible for the pincers' high activity, particular for the former dominated.