Nickel K-edge extended X-ray absorption fine structure studies of bis(diamine) nickel-(II) and -(III) complexes

Abstract

Nickel and bromine K-edge extended X-ray absorption fine structure (EXAFS) data combined with UV/VIS spectroscopy have been used to study a range of Ni(L–L)₂X₂ complexes [X = Cl or Br; L–L = H₂NCH₂CH₂NH₂(en), H₂NCHMeCH₂NH₂(pn), H₂N(CH₂)₃NH₂(tn), MeHNCH₂NH₂, Me₂NCH₂CH₂NH₂, MeHNCH₂CH₂NHMe or Me₂NCH₂CH₂NHMe]. The data are consistent with pseudo-octahedral cis-N₄X₂ donor sets. In two cases only was there clear evidence in the EXAFS of back scattering from a second nickel centre indicative of a halide-bridged dimer formulation [(L–L)₂Ni(µ-X)₂Ni(L–L)₂]X₂. The synthesis and properties of some nickel(III) complexes trans-[Ni(L–L)₂X₂]X are described.