Hydrogen bonded networks based on Ni(II)-tetraazamacrocycle (tet-b) complexes: synthesis, isolation and structural characterization of α -[Ni(tet-b)(Cl)](ClO4) and α -[Ni(tet-b)(en)](ClO4)2

Abstract

Five- and six-coordinate, α-[Ni(tet-b)(Cl)](ClO4) (1) and α-[Ni(tet-b)(en)](ClO4)2 (2) (tet-b = C-racemic-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) complexes have been synthesized and isolated from the reactions of α-[Ni(tet-b)](ClO4)2, which has trans-V (1R,4R,8R,11R,7S,14S or 1S,4S,8S,11S,7R,14R) conformation, with t-Bu4NCl and ethylenediamine (en), respectively. The complexes have been characterized by X-ray crystallography. The crystal structure of 1 shows a distorted trigonal bipyramidal (TBP) coordination geometry composed of four nitrogen atoms from tet-b and a chloro group with an N4Cl chromophore about the nickel(II) ion. The complex cations of 1 are assembled by the perchlorate ions via N–H ··· O hydrogen bonding to form 1-D zigzag chains along the [001] direction. The chains are linked through intermolecular hydrogen bonding where the coordinated chloro group of the complex cation forms two-center double hydrogen bonds with the adjacent N–H groups of the macrocyclic ligand along the [100] direction, resulting in a two-dimensional α-network. The crystal structure of 2 shows a distorted octahedral coordination environment consisting of four nitrogen atoms from tet-b and two from en with an N6 chromophore about nickel(II) ion. The crystal packing analysis shows that the complex cations, α-[Ni(tet-b)(en)]2+ are interconnected by perchlorate ions through conventional two-center (N)H ··· O, and bifurcated (N)H ··· O ··· H(N) hydrogen bonding.