Nickel K-edge extended X-ray absorption fine structure studies of tris(diamine) complexes of nickel(II) and their halogen oxidation products

Abstract

Nickel K-edge extended X-ray absorption fine structure data are reported for the tris(diamine) complexes [Ni(L–L)₃]X₂[L–L = H₂NCH₂CH₂NH₂(en), H₂NCHMeCH₂NH₂(pn), H₂NCH₂CH₂NHMe, H₂NCH₂CMe₂NH₂, and H₂N[graphic omitted]HNH₂; X = Cl, Br, sometimes F or BF₄]. In all cases the data show two clearly defined shells of six nitrogen and six carbon atoms respectively, and for the cyclohexanediamine complexes a third shell of six carbons is well defined. However for the pn, H₂NCH₂CH₂NHMe, and H₂NCH₂CMe₂NH₂ complexes the Ni ⋯ C(Me) distances are not clearly defined, and the data could not distinguish between Ni ⋯ N(Me) and Ni ⋯ NC_backbone distances. The initial chlorine oxidation products of the nickel(II) complexes suspended in dry CCl₄, have been shown to be [Ni(diamine)₃]Cl₃, which decompose to known [Ni(diamine)₂X₂]X or mixed-valence materials in solution.