New imino-pyridyl nickel(II) complexes: Synthesis, molecular structures and application as Heck coupling catalysts

Reactions of imino-pyridyl ligands, (2-pyridyl-2-thiophenemethyl)imine (L1) and (2-pyridyl-2-thiopheneethyl)imine (L2) with NiBr2(DME) gave the corresponding complexes [Ni(L1)Br2] (1) and [Ni(L2)Br2] (2) in good yields. Treatment of 1 and 2 with one equivalent of 2-hydroxythiophenol resulted in the displacement of the bromide ligands to form the nickel(II) thiolato complexes 3 and 4. Molecular structure of 3 confirmed that L1 and L2 bind to the nickel atom in a bidentate fashion. Complexes 1–4 catalyzed the Heck coupling reaction of iodobenzene and bromobenzene with methyl acrylate.

Nickel(II) complexes derived from imino-pyridyl ligands effectively catalyze the coupling reactions of aryl iodides and aryl bromides with methyl acrylate under mild conditions of 80 °C, displaying conversions as high as 90%.Figure optionsDownload as PowerPoint slideHighlights
► Four imino-pyridyl nickel(II) complexes have been synthesized.
► The complexes catalyze Heck coupling reactions at mild conditions.
► High conversions of 90% for the iodobenzene reactions were observed.
► Low conversions of 23% were reported for the bromobenzene reactions.