Coordination Chemistry of Acrylamide. 6 Synthesis and Coordination Compounds of N‐Pyrazolylpropanamide – a Versatile Acrylamide‐derived Ligand

Abstract

AbstractThe syntheses, spectroscopy and single crystal X‐ray structures of the multifunctional acrylamide‐derived ligand N‐pyrazolylpropanamide (= L) (1), and its complexes [L2CuCl2] (2) and [L4Co3Cl6] (3) with copper(II) and cobalt(II) chlorides, respectively, are described. The ligand 1 is easily obtained in one step by the reaction of pyrazole with acrylamide in a 1:1 molar ratio in the presence of trimethylbenzylammonium hydroxide as a basic catalyst. The reaction of CuCl2·2H2O with 1 in a 1:2 metal salt:ligand molar ratio in ethanol/‐triethylorthoformate solution gave coordination compound 2. The crystal structure of 2 contains two seven‐membered chelate rings formed by two nitrogen atoms of the pyrazolyl groups and two weakly coordinated carbonyl oxygen atoms of the substituted amide moieties. Two chloride ions in the axial positions complete a distorted octahedral coordination environment around the CuII atom. The reaction of CoCl2·6H2O with 1 in a 1:2 metal salt:ligand molar ratio afforded the unusual zwitterionic complex 3. The crystal structure of 3 contains a central cobalt atom in an octahedral coordination surrounded by four ligands in which two of them act as chelate ligands and the other two, coordinated via the carbonyl oxygen atoms of the amide moieties to this metal center, act as bridging ligands bonded to two CoCl3− units.