Magnetic Studies on μ-Azido Polynuclear Nickel(II) Compounds with the 222-tet Ligand. Crystal Structure of (μ-N3)2[Ni(222-tet)]2(BPh4)2 (222-tet = Triethylenetetramine) and EXAFS Structural Characterization of the Triangular Compounds (μ-N3)3[Ni(222-tet)]3(X)3 (X = PF6-, ClO4-) | Publicación