Comparative Studies of 2-, 3-, and 4-Pyridylpalladium(II) Complexes: Synthesis and Properties

Article abstract of DOI:10.1246/bcsj.60.149

Oxidative addition reactions of bromopyridines to tetrakis(triphenylphosphine)palladium(0) gave (1b), trans- (2b), and trans- (3b), which were converted on treatment with triethylphosphine to trans- complexes (1d, 2d, 3d, respectively).Titration with perchloric acid in dioxane-water (1:1 by volume) indicated the basicity sequence of these complexes: 2-pyridyl>>4-pyridyl>3-pyridyl.The bromide ligand in 1b-3b can readily be replaced by Cl^-, I^-, N3^-, NCO^-,and NCS^-.In each corresponding series the relative thermal stability is in the sequence of 2-pyridyl>4-pyridyl>3-pyridyl.The pyridyl complexes containing triphenylphosphine react with carbon monoxide at ambient temperature and pressure to afford acyl complexes, which produce the corresponding esters by reactions with methanol.They also act as catalysts for cross coupling reactions of bromopyridines.