Influence of the counter ion on the structure of two new copper(I) coordination polymers: Synthesis, structural characterization and thermal analysis

Two new coordination polymers [Cu2(μ3-SCN)2(μ-bbd)]n (1) and {[Cu(μ-bbd)1.5](PF6)}n (2) were synthesized by the reactions of 1,4-bis(3,5-dimethylpyrazol-1-yl)butane (bbd) with the corresponding copper(I) salts, in order to evaluate the effect of the counter anion on the structure of the resulting products. The structure of these compounds were determined by X-ray crystallography; Compound 1 is a 2D coordination polymer, in which the thiocyanate ligand adopts uncommon μ3-1κ1N;2:3κ2S coordination mode to link three tetrahedrally coordinated copper centers. The fourth coordination site on each copper atom is occupied by a pyrazole nitrogen atom belonging to a μ-bbd ligand. In contrast to 1, 2 is a 1D chain coordination polymer in which the copper atoms, adopting a distorted trigonal planar geometry, are linked by bridging bbd ligands having alternately two different conformations. The results indicate that the use of a coordinating counter anion as thiocyanate which is capable of bridging more than one metal center instead of non-coordinating hexafluorophosphate anion, promotes the formation of a 2D polymer over a 1D polymeric chain. The complexes have also been characterized by elemental analysis, IR spectroscopy, XRPD and thermal analysis.

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► Flexible bbd bridging ligand can adopt various conformations.
► Thiocyanate ligand exhibit uncommon tridentate μ3-1κ1N;2:3κ2S coordination mode.
► Coordinating anion, SCN−, yielded a 2-D neutral polymer while the non-coordinating anion, PF6-, formed a 1-D cationic polymer.
► The complexes have been characterized by single crystal X-ray diffraction and spectroscopic methods.