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-kappa N-4)nickel(II) tetraiodidocadmate(II), [Ni(C10H24N4)][CdI4] (I), and triiodido-1 kappa I-3-mu-iodido-(1,4,8,11-tetraazacyclotetradecane-2 kappa N-4)cadmium(II)-zinc(II), [CdZnI4(C10H24N4)] (II) (C10H24N4 = 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 [CdI4](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)(CdI4)]. 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 [CdI4](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 angstrom and 109.6 degrees, 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 [CdI4](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 ((1) over bar 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.