NICKEL K-EDGE EXTENDED X-RAY ABSORPTION FINE-STRUCTURE STUDIES OF TRIS(DIAMINE) COMPLEXES OF NICKEL(II) AND THEIR HALOGEN OXIDATION-PRODUCTS

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 H2NCH(CH2)4CHNH2; 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.