Formation of polymeric cadmium(II) complexes by interlinkage through 1,4-diazoniobicyclo[2.2.2]octane-1,4-diacetate: [{CD(L)X 2(H 2O) 2} n]· nH 2O (X=Cl,Br) and [{Cd(L)I 2} n]· n H 2O [formula omitted

Abstract

Three novel polymeric cadmium(II) halide complexes containing a double betaine ligand with a rigid tris(ethylene) bridge between two quaternary nitrogen atoms, namely [{Cd(L)Cl 2(H 2O) 2} n ]· nH 2O ( 1), [{Cd(L)Br 2(H 2O) 2} n ]· nH 2O ( 2) and [{Cd(L)I 2} n ]· nH 2O ( 3) ( L = − O 2 CCH 2 N + ( CH 2 CH 2) 3 N + CH 2 CO 2 −) , have been prepared and characterized by X-ray crystallography. Complexes 1 and 2 constitute an isomorphous pair exhibiting an infinite zigzag chain running parallel to the c-axis, which is constructed of an alternate arrangement of distorted CdX 2O 4(X = Cl, Br) octahedra and double betaine ligands. Complex 3 consists of a similar zigzag chain running parallel to the c-direction, but each cadmium(II) atom is in an irregular CdI 2O 3 five-coordinate environment. The formation of hydrogen bonds leads to a three-dimensional network in 1 and 2, and a two-dimensional layer in 3. The conformation of the present rigid double betaine ligand and its ability to generate coordination polymers are compared with related cadmium(II) complexes containing two flexible double betaine ligands containing an adipic acid skeleton.