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On the Mechanism of Reduction of Maleate Ions by Ni I Complexes with Tetraazamacrocyclic Ligands in Aqueous Solutions
Author(s) -
Schutz Osnat,
Masarwa Alexandra,
Zilbermann Israel,
Maimon Eric,
Cohen Haim,
Meyerstein Dan
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201301115
Subject(s) - chemistry , cyclam , aqueous solution , maleic acid , radiolysis , steric effects , ligand (biochemistry) , metal , nickel , metal ions in aqueous solution , inorganic chemistry , ion , medicinal chemistry , stereochemistry , organic chemistry , biochemistry , receptor , copolymer , polymer
Recently, it was shown that Ni I and Co I complexes with tetraazamacrocyclic ligands [namely, trans ‐III‐Ni I L 3 + ( L 3 = 1,4,8,11‐tetraazacyclotetradecane), Ni I cyclam and rac ‐Co I L 1 + ( L 1 = 5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradeca‐4,11‐diene, dien)] reduce maleate ions in aqueous solutions. It was decided to expand the study to further Ni I L i + complexes. In the present study, the reactions of rac ‐Ni I L 1 + and meso ‐Ni I L 2 + ( L 2 = 5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane) with maleate ions were investigated. The effect of the addition of maleic acid to aqueous solutions containing these low‐valent metal complexes, prepared by the pulse radiolysis technique, was studied. The d→π* complexes formed between monovalent nickel complexes and maleate ions were detected and characterised by UV/Vis spectroscopy. The nature of the final products formed depends strongly on the nature of the metal and the ligand. Detailed mechanisms of the reduction processes are proposed and compared with those previously reported. The results indicate that the electronic configuration of the central cation as well as the reduction potential of the complex and steric hindrance induced by the ligand affect the reduction mechanism of maleate ions by these analogous complexes.