Crystal structures of the complexes containing macrocyclic cations [M(cyclam)](2+) (M = Ni, Zn) and tetra­iodido­cadmate(2–) anion

The asymmetric units of the isostructural compounds (1,4,8,11-tetra­aza­cyclo­tetra­decane-κ(4) N)nickel(II) tetra­iodido­cadmate(II), [Ni(C(10)H(24)N(4))][CdI(4)] (I), and tri­iodido-1κ(3) I-μ-iodido-(1,4,8,11-tetra­aza­cyclo­tetra­decane-2κ(4) N)cad­mium(II)zinc(II), [CdZnI(4)(C(10)H(24)N(4))] (II) (C(10)H(24)N(4) = 1,4,8,11-tetra­aza­cyclo­tetra­decane, cyclam, L), consist of the centrosymmetric macrocyclic cation [M(L)](2+) [M = Ni(II) or Zn(II)] with the metal ion lying on a twofold screw axis, and the tetra­iodo­cadmate anion [CdI(4)](2−) located on the mirror plane. In I, the anion acts as an uncoordinated counter-ion while in II it is bound to the Zn(II) atom via one of the iodide atoms, thus forming an electroneutral heterobimetallic complex [Zn(L)(CdI(4))]. The Ni(II) and Zn(II) ions are coordinated in a square-planar manner by the four secondary N atoms of the macrocyclic ligand L, which adopts the most energetically stable trans-III conformation. The [CdI(4)](2−) anions in I and II are structurally very similar and represent slightly deformed tetra­hedrons with average Cd—I bond lengths and I—Cd—I angles of ca 2.79 Å and 109.6°, respectively. The supra­molecular organization of the complexes under consideration in the crystals is very similar and is determined by the hydrogen-bonding inter­actions between the secondary amino groups of the ligand L in the [M(L)](2+) cations and iodide atoms of the [CdI(4)](2−) anion. In particular, the alternating cations and anions form chains running along the b-axis direction that are arranged into di-periodic sheets oriented parallel to the (101) and ( [Image: see text] 01) planes. Because both kinds of sheets are built from the same cations and anions, this feature provides the three-dimensional coherence of the crystals of I and II.