Sustainable carbon–carbon bond formation catalyzed by new oxamate-containing palladium(II) complexes in ionic liquids

•Design of new structurally well-defined bis(oxamato)palladated(II) pre-catalysts•Heck and Suzuki reactions have been efficiently catalyzed by these new complexes in ILs•These catalysts are easily recovered and reused for further catalytic cycles

New and versatile bis(oxamato)palladate(II) complexes of formula (n-Bu4N)2[Pd(2-Mepma)2]·4H2O (1a) and (n-Bu4N)2[Pd(4-Mepma)2]·2H2O·MeCN (1b) (n-Bu4N+ = tetra-n-buthylammonium, 2-Mepma = N-2-methylphenyloxamate and 4-Mepma = N-4-methylphenyloxamate) have been synthesized and characterized by spectroscopic methods and single crystal X-ray diffraction. Each palladium(II) ion in 1a and 1b is four-coordinate with two oxygen and two nitrogen atoms from two fully deprotonated oxamate ligands building a centrosymmetric square planar surrounding. Their catalytic role has been investigated for both Heck and Suzuki coupling reactions using a series of aryl iodide/bromide derivatives in tetra-n-butylammonium bromide (n-Bu4NBr) as ionic liquid, i.e. molten salt. These precatalysts appear as highly efficient, easily recovered and reused at least eight times without any drastic loss of their exceptional reactivity or leaching from the ionic liquid medium.

Graphical abstractNew and versatile structurally well-defined stable bis(oxamato)palladate(II) complexes have been synthesized and their catalytic role investigated for both Heck and Suzuki coupling reactions in the ionic liquid tetra-n-butylammonium bromide (TBAB). The catalysts were easily recovered and reused at least eight times without any significant loss of their exceptional reactivity.Figure optionsDownload full-size imageDownload as PowerPoint slide