Metallacycles of cadmium, mercury dicarboxylates

Abstract

A series of linear coordination polymers, metallacycles of cadmium(II) and mercury(II) of flexible carboxylic acid ligands, RCH{3-CH₃–,5-CH₃–,6-(–OCH₂CO₂H)C₆H₂}₂, (when R = C₆H₅, (H₂L¹); 2-NO₂C₆H₄– (H₂L²) and 3-NO₂C₆H₄– (H₂L³)) are synthesized and characterized. [CdL¹ (py)₃]_n·3nH₂O (py = pyridine) is a linear coordination polymer, whereas [CdL²(py)(CH₃OH)]₂·CH₃OH is a dinuclear complex of cadmium with a Cd₂O₂ type of core. The latter is obtained from reaction of cadmium(II) acetate with H₂L² in methanol followed by reaction with pyridine. A similar reaction of cadmium(II) acetate with H₂L² in dimethylformamide results in the formation of a cadmium metallacycle, namely [CdL² (py)₂(H₂O)]₂·H₂O. The H₂L³ reacted with cadmium(II) acetate in the presence of pyridine to form a metallacycle [CdL³(py)₂(H₂O)]₂·3H₂O. The ligand H₂L² form mercury(II) metallacycle [HgL²(4-mepy)₂]₂ in the presence of 4-methylpyridine (4-mepy) and the ligand H₂L³ forms metallacycle [HgL³(3-mepy)₂]₂·DMF in the presence of 3-methylpyridine (3-mepy). The potassium salts of H₂L¹ and H₂L² were found to be coordination polymers and these potassium coordination polymers were structurally characterized.