Metal Complexes with Macrocyclic Ligands. Part XXVII. Cu2+-promoted hydrolysis of carboxylic- and phosphonic-acid esters in the side chain of tetraazamacrocycles

✍ Scribed by Daniel Tschudin; Andreas Riesen; Thomas A. Kaden

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: German
• Weight: 433 KB
• Volume: 72
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19890720117

✦ Synopsis

The X-ray structures of the Cuz+ complexes of 1,4,8,11 -tetraazacyclotetradecane derivatives with an ethylpropionate and diethylphosphonate group, 5 and 6, respectively, indicate that the metal ion is pentacoordinated by the four N-atoms of the macrocycle and one 0-atom. In the case of 5, it is the carbonyl 0-atom of the carboxylate group, whereas for 6 it is the phosphonyl 0-atom of the phosphonate group. The hydrolysis kinetics of the functional group in the Cu2+ complexes with the 1,4,8,1l-tetraazacyclotetradecanes 3-6 have been measured by pH-stat and stopped-flow techniques. The rate law for the hydrolysis of the carboxylates 3-5 is proportional to the complex concentration and to [OH7 up to pH 13, whereas that of the phosphonate 6 is proportional to [OH-] up to pH 11.5, becoming independent of [OH-] at pH > 11.5. The mechanisms of these two reactions are discussed, considering the possibility of an intra-or an intermolecular OH-attack and the results of the X-ray structure analyses.