Nickel(II) complexes with tetraaza macrocyclic ligands

The Ni(II) complexes of 1,5,9,13-tetraazacyclohexadecane ([16]aneN(4)) and 1,4,8,12 tetraazacyclopentadecane ([15]aneN(4)) ligands have been synthesized and characterized by X-ray crystallography. Crystal data for orange [Ni([16]aneN(4))](ClO4)(2) (1) at 213 K: monoclinic space group P2(1)/c, a = 13.38(1), b = 17.818(6), c = 16.579(6) Angstrom, beta = 90.80(6)degrees, V = 3952(4) Angstrom 3; for [Ni([15]aneN(4))[ClO4)(2)] (3) at 173 K: monoclinic space group P2(1)/n, a = 8.072(2), b = 17.857(2), c = 12.923(2) Angstrom, beta = 95.92(1)degrees, V = 1852.8(7) Angstrom 3. Compound 1 has the ligand in the ch,ch,ch,ch, + - + - conformation, but the nitrogen atoms are practically coplanar. In 3, the ligand conformation is again planar, but octahedral coordination about the nickel ion is completed by two unidentate ClO4- ions and the compound is purple with (presumably) high-spin nickel(II). There is an orange precursor, 2, to 3 in which the ClO4- ions are not coordinated and the structure is planar. (C) 1998 Elsevier Science B.V. All rights reserved.