Coordination polymers based on cadmium(ii) pyridine complexes: synthesis, range of existence, and structureDedicated to Prof. Dr. G. E. Herberich on the occasion of his 65th birthday.

Abstract

A series of nine new cadmium compounds of formal composition [Cd(m-X) 2 py 2 ] (X ~Cl, Br, I; py 3,5-disubstituted pyridine ligands with methyl, chloro, and bromo substituents) were synthesized and characterized by single crystal X-ray diffraction. Only for the combination of the sterically most demanding ligands, namely I and 3,5-dimethylpyridine, is a mononuclear tetrahedral complex obtained; in all other eight cases one-dimensional coordination polymers are found. In these chains cadmium(II) cations are linked in an edge-sharing fashion by halogen bridges in their pseudoequatorial plane, with terminal pyridine ligands completing the pseudo-octahedral coordination sphere. In all polymers the distance between neighboring Cd atoms corresponds to the shortest lattice constant: metal … metal separations systematically depend on both bridging and terminal ligands and range between 3.77 and 4.14 A ˚. This intermetal distance and the coordination mode of the donor ligands are found to be correlated. Five of the Cd chain polymers adopt the structure type found for [Zn(m-Cl) 2 py 2 ] ' . In addition to previous work the zinc derivatives [ZnX 2 (3,5-Me 2 py) 2 ] (X ~Cl, Br) were investigated for comparison and shown to be mononuclear.

catena-Poly[[bis[quinazolin-4(3H)-one-κN1]cadmium(II)]-di-μ-chlorido]

“…For related Cd(II) coordination polymers, see: Hu & Englert (2002); Hu et al (2003); Englert & Schiffers (2006a,b); Cao et al (2008). For a general review of halide-bridged chain polymers, see: Englert (2010).…”

Tunable Crystal-to-Crystal Phase Transition in a Cadmium Halide Chain Polymer

“…We communicate the twinned low-temperature structure of the material, and we describe the temperature dependence of the transformation in the isomorphous series [{Cd(µ-Br) 2−2x (µ-Cl) 2x py 2 } 1 ∞ ] as summarized in Scheme 1. [1,[6][7][8][9][10] and represents a halide-bridged chain polymer (Scheme 1). At room temperature the compound crystallizes in the orthorhombic space group Pnnm, with the Cd cations in Wyckoff position 2a.…”

Crystal structure of diiodido-bis(phenanthridine-κN)cadmium(II), CdI2(C13H9N)2, C26H18CdI2N2

“…[7][8][9][10]. In most cases, zinc (II) derivatives form mononuclear tetrahedral complexes, whereas the higher homologue cadmium(II) yields chain polymers [7][8][9][10]. Different from the chain polymers of most reported CdX 2 L 2 , the title compound is a mononuclear tetrahedral complex.…”

“…For group 12 (IIB) metal halides and pyridine-type ligands, the reported hybrid materials generally have a formal composition [MX 2 (L) 2 ], where M represents a divalent metal cation (Zn, Cd, Hg), X a halogen ligand (Cl, Br, I), L a pyridine derivative such as pyridine, pyrazine or bipyridine, etc. [7][8][9][10]. In most cases, zinc (II) derivatives form mononuclear tetrahedral complexes, whereas the higher homologue cadmium(II) yields chain polymers [7][8][9][10].…”