Synthesis and structural characterisation of cadmium(II) and zinc(II) coordination polymers with an angular dipyridyl bridging ligand: parallel interpenetration of two-dimensional sheets with 4.82 topology

Abstract

Coordination polymers formed between Cd(NO₃)₂ or Zn(NO₃)₂ and 2,4-bis(4-pyridyl)-1,3,5-triazine (dpt) have been synthesized and their single crystal structures determined. Reaction of a 1∶1 ratio of Cd(NO₃)₂ with dpt in MeCN–CH₂Cl₂ affords the complex [Cd₂(NO₃)₄(dpt)₂(MeCN)]_∞ 1 which exists as a doubly interpenetrated 4.8² two-dimensional sheet in the solid state. Each sheet is constructed from nitrate-bridged [Cd(dpt)]₄ metallacycles. In sharp contrast the analogous reaction performed using a 2∶1 L∶M ratio affords the discrete molecular complex [Cd(NO₃)₂(dpt)₂(MeCN)] 2 in which both dpt ligands act as terminal donors rather than bridging metal centres. Reaction of Cd(NO₃)₂ with dpt in EtOH–CH₂Cl₂ affords a one-dimensional coordination polymer [Cd(NO₃)₂(dpt)(EtOH)]_∞ 3. Zn(NO₃)₂ reacts with dpt in either a 1∶1 or 2∶1 L∶M ratio to afford the one-dimensional polymer [Zn(NO₃)₂(dpt)]_∞ 4 which can be isolated as two polymorphs 4a and 4b which differ in their nitrate binding modes. The product formed is independent of the L∶M ratio used in the reaction. Only 4a is formed when MeCN–CH₂Cl₂ is used as reaction solvent whereas both 4a and 4b are formed from either EtOH–CH₂Cl₂ or ⁱPrOH–CH₂Cl₂.