Mononuclear and dinuclear bromide-nitrite cadmium(II) complexes with related 1,4-diazabicyclo[2.2.2]octane ligands.

The title compounds, di-μ-bromido-bis[bromido(1-carboxymethyl-4-aza-1-azoniabicyclo[2.2.2]octane-κN(4))(nitrito-κ(2)O,O')cadmium(II)] dihydrate, [Cd(2)Br(4)(C(8)H(15)N(2)O(2))(2)(NO(2))(2)]·2H(2)O, (I), and aquabromido(1-cyanomethyl-4-aza-1-azoniabicyclo[2.2.2]octane-κN(4))bis(nitrito-κ(2)O,O')cadmium(II) monohydrate, [CdBr(C(8)H(14)N(3))(NO(2))(2)(H(2)O)]·H(2)O, (II), are two-dimensional hydrogen-bonded metal-organic hybrid complexes. In (I), the complex is situated on a centre of inversion so that each symmetry-related Cd(II) atom is coordinated by two bridging Br atoms, one monodentate Br atom, one chelating nitrite ligand and one organic ligand, yielding a significantly distorted octahedral geometry. The combination of O-H···O and O-H···Br hydrogen bonds produces centrosymmetric R(6)(6)(16) ring motifs, resulting in two-dimensional layers parallel to the ab plane. In contrast, the complex molecule in (II) is mononuclear, with the Cd(II) atom seven-coordinated by two bidentate nitrite groups, one N atom from the organic ligand, one monodentate Br atom and a water O atom in a distorted pentagonal-bipyramidal environment. The combination of O-H···O and O-H···Br hydrogen bonds produces R(5)(4)(14) and R(3)(3)(8) rings which lead to two-dimensional layers parallel to the ac plane.