Oxidative Addition of 2-Halogenopyridines and 2-Chloroquinoline to Zero-Valent Group 10 Metals

Abstract

Oxidative addition of the C2–X (X = Cl, Br) bond of 2-halogenopyridines or 2-chloroquinoline to zero-valent group 10 metal complexes in the presence of a proton source leads to complexes bearing pyridine-derived protic remote NHC (rNHC) ligands. The oxidative addition of 2-halogeno-functionalized pyridine derivatives to complexes [M0(PPh3)4] (M = Pd, Pt) in the presence of NH4BF4 or NH4PF6 yielded complexes trans-[1]PF6–trans-[5]BF4 with a trans-arrangement of the two remaining PPh3 ligands. The oxidative addition to Ni0 was achieved by reaction of the halogenopyridine derivatives with [Ni(cod)2]/PEt3 in the presence of a proton acid (NH4BF4 or NH4PF6) yielding complexes of type trans-[Ni(protic-rNHC)(PEt3)2X]A (A = BF4–, PF6–). In the absence of a proton source, the oxidative addition of 2-chloroquinone to [Ni(cod)2]/PEt3 yielded the neutral complex trans-[8] bearing an anionic quinoline-derived rNHC ligand. The molecular structures of selected complexes have been determined by X-ray diffraction studies.