Structural characterization of a new polymeric Cu(II) complex with unexpected chlorinated pyrazole ligand

• A new coordination polymer based on Cu(II) and Cl-pyrazole ligand is reported.
• The polymer has been obtained by a very easy synthesis and green reaction conditions.
• The new [CuCl2(ClpzH)2]n compound presented an unexpected chlorination of the Hpz ring.
• > Extended structure revealed a 2D network supported by N-H
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• Cl and C-H
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• Cl hydrogen bonds and π-π stacking interactions.

A new coordination polymer based on copper(II) and pyrazole (pzH) ligand, [CuCl2(ClpzH)2]n, has been obtained by a very easy synthesis and green reaction conditions using water as solvent. The compound was characterized by single crystal X-ray diffraction elemental analyses, infrared and UV–Vis spectroscopies. For the first time the C(2)-chlorination of the pyrazolyl ring keeping the protonation of the N(2)–H is reported. The polymeric crystal structure consists of a one dimensional infinite neutral chain in which the copper(II) atoms are six-coordinated in a slightly distorted octahedral geometry with two nitrogen and four chlorine atoms. In this structure, intermolecular interactions have been identified and studied. Extended structure analyses revealed a novel two-dimensional network supported by intermolecular NHCl and CHCl hydrogen bonds, in addition to the π–π stacking interactions.

The synthesis of a new [CuCl2(ClpzH)2]n compound where the C-chlorination of the pyrazole ring and the formation of a polymeric structure are unexpectedly observed. This new compound has been characterized by elemental analyses, infrared and UV–vis spectroscopies, and single crystal X-ray diffraction. Intermolecular interactions have been studied. Extended structure analyses revealed a novel three-dimensional network formed by intermolecular NHCl hydrogen bonds, CHCl and π–π stacking interactions.Figure optionsDownload as PowerPoint slide