Heterometallische Mehrkernkomplexe von Zink und Cadmium mit cis-[Cr(OH)2(en)2]+-Liganden / Heterom etallic Polynuclear Complexes of Zinc and Cadmium with cis-[Cr(OH)2(en)2]+ Ligands

Abstract

A series of polynuclear heterometallic complexes containing chromium and zinc or cadmium were prepared by the reaction of cis-[CrCl2(en)2]Cl and a zinc or cadmium salt in water and the molecular and crystal structures of 1 to 5 determined by X-ray structure analyses. The products contain chelating or bridging cis-[Cr(OH)2(en)2]+ groups. For the zinc complexes a tetrahedral coordination is observed, and the [Cr(OH)2(en)2]+ units are found to act as bridges. [[ZnCl2(μ-OH)Cr(en)2(μ-OH)]ClO4]n (1) has a chain polymeric structure. [{ZnCl2(μ-OH)Cr(en)2(μ-OH)}2]Cl2 (2) has a cyclic structure. In the case of the cadmium complexes the [Cr(OH)2(en)2]+ units act as chelating ligands. For the three cadmium complexes [Cd3(μ-Cl)4Cl4{Cr(μ3-OH)(μ-OH)(en)2}2]·4H20 (3), [[Cd(μ-Cl)(H2O)2{Cr(μ-OH)2(en)2}](ClO4)(NO3)·2H2O]n; (4), and [Cd2(μ-Cl)2Cl3(H2O)3{ Cr(μ-OH)2(en)2}]n; (5) an octahedral coordination sphere is observed. The cadmium atoms in 3 to 5 are connected by at least one chloro bridge. In the centrosymmetrical pentanuclear complex 3 bridging occurs by face-sharing, and in the chain polymeric complexes 4 and 5 by edge-sharing of the coordination octahedra. In the crystal structures of all complexes a network of hydrogen bonds is observed, which contributes substantially to the stability of the conformation of the chain structures.