6533b871fe1ef96bd12d2205

RESEARCH PRODUCT

N-protonated 2-pyridylnickel(II) complexes insertion of isocyanides into the nickel2-pyridyl bond

subject

description

The reaction of the binuclear complex [NiCl(μ-2-py)(PPh3)]2 (μ-2-py = μ-C5H4N-C2,N) with the phosphines L (L = PPh3, PMePh2, PMe2Ph or PEt3) or dppe (= 1,2-bis(diphenylphosphino)ethane) in the presence of HClO4 yields the N-protonated 2-pyridyl derivatives trans-[NiCl(2-pyH)(L)2]ClO4 or [NiCl(2-pyH)(dppe)] ClO4 (2-pyH = C5H5N-C2) with a square-planar coordination around the nickel(II) center. These products are largely associated through hydrogen bonding between the NH group and the perchlorate anion, both in the solid and in chlorinated solvents. The configuration in solution has been studied by 1H and 31P NMR spectroscopy. In the complex trans-[NiCl(2-pyH)(PMe2Ph)2]ClO4, the planar 2-pyH ligand is oriented perpendicularly to the coordination plane, with restricted rotation about the NiC2 bond. The reaction of rans-[NiCl(2-pyH)(PMePh2)2]ClO4 with CNC6H4OMe-p and then with NEt3 yields the unstable compound trans-[NiCl{C(2-py)NC6H4OMe-p}(PMePh2)2] through a fast migratory insertion of the isocyanide into the nickel2-pyridyl bond. This product can be isolated and characterized only when the imino(2-pyridyl)methyl group is σ,σ′-N,N′-chelated to ZnCl2.