Crystal structures of the complexes containing macrocyclic cations [ M (cyclam)] 2+ ( M = Ni, Zn) and tetra-iodido-cadmate(2-) anion.

The asymmetric units of the isostructural compounds (1,4,8,11-tetra-aza-cyclo-tetra-decane-κ 4 N )nickel(II) tetra-iodido-cadmate(II), [Ni(C 10 H 24 N 4 )][CdI 4 ] ( I ), and tri-iodido-1κ 3 I -μ-iodido-(1,4,8,11-tetra-aza-cyclo-tetra-decane-2κ 4 N )cad-mium(II)zinc(II), [CdZnI 4 (C 10 H 24 N 4 )] ( II ) (C 10 H 24 N 4 = 1,4,8,11-tetra-aza-cyclo-tetra-decane, 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 tetra-iodo-cadmate 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 tetra-hedrons with average Cd-I bond lengths and I-Cd-I angles of ca 2.79 Å and 109.6°, respectively. The supra-molecular organization of the complexes under consideration in the crystals is very similar and is determined by the hydrogen-bonding inter-actions 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 (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 .