Palladium(II) complexes with new bidentate phosphine-imine ligands for the Suzuki C[sbnd]C coupling reactions in supercritical carbon dioxide

Abstract

Newly designed perfluorinated phosphine-imine ligands (3a-c) have been synthesized from the 3-(heptadecafluorooctyl)aniline and 2-(diaryl)phosphinobenzaldehyde (diaryl: −Ph2, 2a; −(3,5-(CH3)2Ph)2, 2b; −(3,5-(CF3)2Ph)2, 2c) and complexed with dichloro(1,5-cyclooctadiene)palladium(II) to form supercritical carbon dioxide (ScCO2) soluble palladium(II) complexes (4a-c). All compounds were fully characterized using spectroscopic and analytical techniques, including 31P, 1H, 19F, 13C NMR and FTIR spectroscopies and high resolution mass spectroscopy. These palladium(II) complexes having perfluoroctyl ponytails (-C8F17) are soluble in carbon dioxide at >333 K under 122 atm of CO2 pressure. Homogenous palladium catalyzed Suzuki CC coupling reactions using the novel catalysts were carried out at 353 K 135 atm. To the best of our knowledge, we applied the first example of hetereodonor bidentate ligands which are bearing both phosphine and imine group for the palladium catalyzed Suzuki CC coupling reaction in ScCO2 solvent system.