Syntheses and Crystal Structures of Five Cadmium(II) Complexes Derived from 4-Aminobenzoic Acid

Abstract

Five cadmium(II) complexes, [CdClL·H2O]n (1), [CdBrL·H2O]n (2), CdI2(HL)2 (3), {[Cd(dca)2(HL)2]·2H2O}n (dca− = dicyanamide) (4), and (H2L)2[CdCl4(H2O)2] (5), have been synthesized by the reaction between 4-aminobenzoic acid (HL) and Cd2+. In 1 and 2, L− serves as a tridentate ligand and bridges six-coordinate CdII centers to form [CdII−L]n chains; halide anions link adjacent chains into two-dimensional layers. Complex 3 is a typical metallic carboxylic acid synthon. In 3, HL acts as a monodentate ligand coordinating to CdII through the nitrogen atom, and the head-to-tail hydrogen bonds of carboxylic groups result in a zigzag chain. The weak Cd···I interactions between adjacent chains extend the zigzag chain-like structure into a two-dimensional structure. Complex 4 consists of [Cd(dca)2(HL)2]n chains and free water molecules. The twelve-membered rings formed by water molecules and carboxylic groups through hydrogen bonds link the adjacent chains to yield a two-dimensional layer. Complex 5 consists of discrete [CdCl4(H2O)2]2− anions and H2L+ organic cations, which are linked by intermolecular hydrogen-bonding interactions to form a three-dimensional structure. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)