Novel hybrid phosphinite-theophylline ligands and their Pd(II) complexes. Synthesis, characterization and catalytic evaluation in Suzuki-Miyaura couplings

Abstract

Two Pd(II) complexes bearing bidentated [R’2(OR)P^P(OR)R’2] (OR = 7-(2,3-dihydroxypropyl)theophylline and R’ = Ph for (1) and R’ = iPr for (2)) ligands were synthesized and fully characterized, including the unequivocal determination of their molecular structures by single crystal X-ray diffraction analysis. Thus confirming the coordination of the phosphinite-theophylline ligand to the Pd(II) center in a chelate manner. Exploration of these compounds as catalysts in Suzuki-Miyaura Couplings revealed complex (2) to be the best of the pair of complexes in the formation of CC bonds in the reactions of phenylboronic acid and a series of para-substituted bromobenzenes under mild reaction conditions (50 °C, 50 W, 5 min, and 0.05 mol % of catalyst), achieving yields of > 99 %.