Ryoji Mitsuhashi

Nickel(II) complex with 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane‡

A nickel(II) complex, [Ni(taetacn)](ClO4)2 ⋅ H2O, where taetacn = 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane was synthesized. The crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. The complex crystallizes in the orthorhombic space group Pna21 with a = 16.004(2) Å, b = 10.186(1) Å, c = 13.937(2) Å, V = 2271.9(5) Å3, Dx = 1.56 g cm−3, Dm = 1.59 g cm−3 (floatation method), and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values are 0.0636 and 0.1672, respectively, for all 4845 independent reflections. The compound is composed of octahedral nickel(II) cation with three 2-aminoethyl pendant groups of taetacn, tetrahedral ClO4− anion, and a water molecule of crystallization. Electronic spectra are consistent with the octahedral geometry. Temperature dependence of the magnetic susceptibility (4.5–300 K) can be interpreted considering the zero-field splitting of the nickel(II) ion (g = 2.14, D = 3.72 cm−1, and Nα = 300 × 10−6 cm3 mol−1). Cyclic voltammetry in DMF showed quasi-reversible and irreversible oxidation waves (Epa = 0.54 V, Epc = 0.45 V; Epa = 1.16 V, Epc = 0.71 V vs. Ag/Ag+).