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.