Nickel(II) thiolates derived from transmetallation reaction of [Zn(Tab)4](PF6)2 with Ni(II) ions and their catalytic activity toward the C[sbnd]N coupling reactions

Abstract

Reactions of NiCl2·6H2O or Ni(ClO4)2·6H2O with 2,2′-bipyridine (2,2′-bipy), or 2-bis(diphenylphosphino)ethane (dppe) or 1,4-bis(diphenylphosphino)butane (dppb) followed by addition of [Zn(Tab)4](PF6)2 (1) resulted in the formation of one trinuclear cationic complex [(2,2′-bipy)4Ni3(μ-Tab)4]Cl0.5(PF6)5.5 (2), one mononuclear cationic complex [Ni(Tab)2(dppe)](PF6)2 (3), and one dinuclear cationic complex [Ni2(dppb)(μ-Tab)2(Tab)2](PF6)2(ClO4)2 (4). Complexes 2–4 were characterized by elemental analysis, IR, UV–vis, 1H and 31P NMR, and single-crystal X-ray diffraction. In the [(2,2′-bipy)4Ni3(μ-Tab)4]6+ hexacation of 2, the central Ni(II) atom is connected to two [Ni(2,2′-bipy)2]2+ fragments by two pairs of μ-Tab ligands, forming a linear trinuclear cationic structure. The Ni(II) center of the dication of 3 is tetrahedrally coordinated by two S atoms from two Tab ligands and two P atoms of one dppe ligand. Complex 4 has a dimeric cationic structure in which two [(Tab)Ni]2+ species are linked by a pair of μ-Tab ligands and one dppb ligand. Complexes 2–4 displayed high catalytic activity toward the cross-coupling reactions of arylboronic acids and amines to produce N-arylated amines.