Structures of tetrakis(1,2-dimethylimidazole)MII diperchlorates (MII = Ni,Cu).

[Ni(C5H8N2)4]2+.2ClO4-, Mr = 642.14, monoclinic, P2(1)/n, a = 17.938 (2), b = 14.438 (2), c = 11.336 (2) A, beta = 93.38 (1) degrees, V = 2931 (1) A3, Z = 4, Dm = 1.44 (1), D chi = 1.455 Mg m-3, mu(Mo K alpha, lambda = 0.71073 A) = 0.90 mm-1, F(000) = 1336, T = 297 (1) K, RF = 0.061, wRF = 0.076 for 2676 reflections. [Cu(C5H8N2)4]2+.2ClO4-, Mr = 646.97, monoclinic, P2(1)/n, a = 98.413 (7) degrees, V = 2873 (1) A3, Z = 4, Dm = 1.47 (1), D chi = 1.496 Mg m-3, mu(Mo K alpha, lambda = 0.71073 A) = 1.00 mm-1, F(000) = 1340, T = 297 (1) K, RF = 0.053, wRF = 0.069 for 2889 reflections. Three of the four ClO4 groups in both structures showed disorder; they were modeled as single-site Cl atoms with unrestrained low-occupancy O atoms. Each NiII ion is coordinated in a distorted square-planar fashion by four N donor atoms from the dimethylimidazole groups. The Ni-N distances are typical. In the Cu complex, one ligand showed an approximate twofold disorder about the Cu-N(im) direction. Each CuII ion also has four square-planar equatorial Cu-N(im) bonds and, in addition, shows unusually weak axial coordination by two O(ClO4) atoms. The Cu-O(ClO4) distances are substantially longer than those found for typical tetragonal CuN4O2(ClO4) coordination, and the observed Cu-O-Cl angles are much larger than usual.