Helical vs. zigzag coordination polymer: Influence of structural preference of metal-ion coordination geometry

Two new coordination polymers [(L-6)CoCl2](infinity) (1) and [(L-6)CdCl2](infinity) (2) (L-6 = alpha,alpha'-bis(pyrazolyl)-m-xylene) have been synthesized and characterized by X-ray crystallography. Structural analysis of I (space group P2(1)) revealed that each Co(II) center is coordinated by two chloride ions and two pyrazole nitrogens from two different L-6 ligands, giving rise to pseudo-tetrahedral coordination environment around Co(II). For this structure 1D helical polymeric chain running along crystallographic 2(1) axis is observed. While for 2 (space group P (1) over bar), each Cd(II) center is coordinated by two chloride ions, two pyrazole nitrogens from two different L-6 ligands, and a chloride ion from the adjacent layer. It provides distorted trigonal bipyramidal geometry around Cd(II), which leads to the formation of a 2D zigzag polymer. In continuation of our recent activity on inorganic crystal engineering, from the standpoint of metal-ligand coordination chemistry and C-H---Cl2MII hydrogen bonding, in this work we have investigated the potential of coordination tectons 1 and 2 in bringing about generality in helix/zigzag network formation, strengthened primarily by C-H---Cl hydrogen-bonding interactions. (c) 2005 Elsevier B.V. All rights reserved.