Discrete monomeric and chloride-bridged dimeric and 1D coordination polymeric mercury(II) complexes of a class of pyridyl-pyrazole ligands with variable denticity and flexibility

Abstract

Using a class of pyridyl-pyrazole ligands with variable denticity and flexibility, i. e., 1-benzyl-[3-(2′-pyridyl)]pyrazole (L¹⁰), 2-[3-(2′-pyridyl)pyrazol-1-ylmethyl]pyridine (L⁵) and 2,6-bis(pyrazol-1-ylmethyl)pyridine (L⁶), three new mercury(II) complexes – two discrete [(L¹⁰)Hg^II(<img src='/image/spc_char/micro.gif' border=0>–Cl)Cl]₂ (<b style="">1</b>) and [(L⁵)Hg^IICl₂](<b style="">2</b>) and a coordination polymeric [(L⁶)Hg^IICl₂]<b style="">·</b>HgCl₂ (<b style="">3</b>), have been synthesized and structurally characterized. In complex (<b style="">1</b>) one of the chlorides from each [(L¹⁰)Hg^IICl₂] unit acts as a bridge, affording a dichloro-bridged mercury(II) complex with slightly distorted square-pyramidal HgN₂Cl₃ coordination sphere. The structure of complex (<b style="">2</b>)<b style=""> </b>reveals an almost ideal square-pyramidal HgN₃Cl₂ coordination sphere. Complex (<b style="">3</b>)<b style=""> </b>has<b style=""> </b>N₃Cl₂ distorted square-pyramidal coordination around Hg^II ion with coordination by L⁶ (facial mode) and two Cl^– ions. Notably, in complex (<b style="">3</b>) one HgCl₂ molecule is present with each [(L⁶)Hg^IICl₂] unit. Due to weak interaction by Hg^II-coordinated Cl^– ion of “[(L⁶)Hg^IICl₂]” unit to HgCl₂, complex (<b style="">3</b>) is a coordination polymer. Analysis of crystal packing diagram of complexes (<b style="">1</b>)–(<b style="">3</b>) reveals occurrence of a variety of non-covalent (<img src='/image/spc_char/pi.gif' border=0>–<img src='/image/spc_char/pi.gif' border=0>, C–H<b style="">^…</b><img src='/image/spc_char/pi.gif' border=0> and C–H<b style="">^...</b>Cl) interactions, which play significant role in generating supramolecular architectures of varied topology.