Synthesis, characterization and low temperature self assembling of (η3-allyl)palladium complexes with 2-pyridyl-1,2,3-triazole bidentate ligands. Study of the catalytic activity in Suzuki-Miyaura reaction

The cationic complexes [Pd(η3-C3H5)(2-((4-propyl-1H-1,2,3-triazol-1-yl)methyl)pyridine)](X) (2: X=BF4−, 3: X=ClO4−), and [Pd(η3-2-CH3-C3H4)(2-((4-propyl-1H-1,2,3-triazol-1-yl)methyl)-pyridine)](BF4−) (4) have been synthesized by reacting the appropriate palladium-allyl precursor with 2-((4-propyl-1H-1,2,3-triazol-1-yl)methyl)pyridine in the presence of AgBF4 or AgClO4. The solid-state structure of 2 has been determined by single-crystal X-ray diffraction analysis. According to 1H NMR spectroscopy the allyl protons undergo syn-syn, anti-anti exchange. 1H NMR spectroscopy reveals that in acetone at temperatures lower than 223 K these complexes form aggregates the stability of which is attributed to solvophobic interactions. Complex 2 is a active catalyst for the S-M coupling of aryl bromides with phenylboronic acid; good reaction rates are obtained only with activated substrates, whereas with deactivated substrates catalyst decomposition to palladium black occurs.