2,2′-Bipyridine, 2-(2-oxazolyl)pyridine and 2,2′-bisoxazole derived nickel(0) complexes as selective catalysts for cross-coupling of aryl chlorides by intramolecularly stabilized dialkylaluminum reagents

Unlike the NiCl2(PPh3)2 catalyzed cross-coupling of chloroarenes with some intramolecularly stabilized dialkylaluminum reagents that is associated with hydrodehalogenation of the substrate, the phosphine-free bis(2,2′-bipyridine)nickel, bis[2-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)pyridine)]nickel, bis[4,4′,5,5′-tetrahydro-4,4,4′,4′-tetramethyl-2,2′-bisoxazole]nickel and tetrakis(pyridine)nickel, promote the cross-coupling in a highly selective fashion. The reduction in the undesired hydrodechlorination by the nickel(0) complexes is explained by the presence of the nitrogen-containing ligands which stabilize the alkylnickel intermediate in the cross-coupling, against disproportionation into an alkene and nickel hydride. X-ray diffraction analyses of the reaction products of Ni(cod)2, chloroarene (or benzyl chloride) with 2,2′-bipyridine and with bis[2-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)]pyridine, respectively, have been performed.