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., l-benzyl-[3-(2'-pyridyl)]pyrazole (L-10), 2-[3-(2'-pyridyl)pyrazol-1-ylmethyl]pyridine (L-5) and 2,6-bis(pyrazol-1-ylmethyl)pyridine (L-6), three new mercury(II) complexes - two discrete [(L-10)Hg-II(mu-Cl)Cl](2) (1) and [(L-5)(HgCl2)-Cl-II] (2) and a coordination polymeric [(L-6)(HgCl2)-Cl-II]center dot HgCl2 (3), have been synthesized and structurally characterized. In complex (1) one of the chlorides from each [(L-10)(HgCl2)-Cl-II] 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-6 (facial mode) and two Cl- ions. Notably, in complex (3) one HgCl2 molecule is present with each [(L-6)(HgCl2)-Cl-II] unit. Due to weak interaction by Hg-II-coordinated Cl- ion of "[(L-6)(HgCl2)-Cl-II]" 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 (pi-pi, C-H-center dot center dot center dot pi and C-(HCl)-Cl-center dot center dot center dot) interactions, which play significant role in generating supramolecular architectures of varied topology.