Nickel-(II), -(III) and -(IV) complexes of 1,2-bis(dimethylarsino)tetrafluorobenzene and X-ray crystallographic and extended X-ray absorption fine structure studies of nickel-(III) and -(IV) bromo complexes

Abstract

1,2-Bis(dimethylarsino)tetrafluorobenzene, o-C₆F₄(AsMe₂)₂, forms high-spin tetragonal nickel(II) complexes [Ni(L–L)₂X₂](X = Cl or Br), which remain six-co-ordinate in non-polar solvents, and planar diamagnetic [Ni(L–L)₂]I₂. Pseudo-octahedral nickel-(III) and -(IV) complexes [Ni(L–L)₂X₂]ⁿ⁺ are formed on oxidation, and their properties are compared with those of the fluorine-free ligand o-C₆H₄(AsMe₂)₂. The X-ray crystal structure of trans-[Ni{o-C₆F₄(AsMe₂)₂}₂Br₂]BF₄ has been determined, and revealed a tetragonal cation with Ni–Br 2.543(1) and Ni–As 2.336(1), 2.339(1)Å. Nickel and bromine K-edge extended X-ray absorption fine structure data are reported for a variety of complexes of Ni^II, Ni^III and Ni^IV with o-C₆F₄(AsMe₂)₂, o-C₆H₄(AsMe₂)₂ and o-C₆H₄(PMe₂)₂, and the results compared with existing data on the chloride analogues.