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

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