Chelate Ring Size Variations and Their Effects on Coordination Chemistry and Catechol Dioxygenase Reactivity of Iron(III) Complexes

• Published in: Inorganic chemistry Vol. 44; no. 21; pp. 7582 - 7589
• Main Authors: Merkel, Michael, Pascaly, Matthias, Krebs, Bernt, Astner, Jörg, Foxon, Simon P, Schindler, Siegfried
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.10.2005
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic050708k

The catechol dioxygenase reactivity of iron(III) complexes using tripodal ligands was investigated. Increasing, as well as decreasing, chelate ring sizes in the highly active complex [Fe(tmpa)(dbc)]B(C6H5)4 (tmpa = tris[(2-pyridyl)methyl]amine; dbc = 3,5-di-tert-butylcatecholate dianion), using related ligands, only resulted in decreased reactivity of the investigated compounds. A detailed low-temperature stopped-flow investigation of the reaction of dioxygen with [Fe(tmpa)(dbc)]B(C6H5)4 was performed, and activation parameters of ΔH ⧧ = 23 ± 1 kJ mol-1 and ΔS ⧧ = −199 ± 4 J mol-1 K-1 were obtained. Crystal structures of bromo-(tetrachlorocatecholato-O,O‘)(bis((2-pyridyl)methyl)-2-pyridylamine-N,N‘,N‘ ‘)-iron(III), (μ-oxo)-bis(bromo)(bis((2-pyridyl)methyl)-2-pyridylamine-N,N‘,N‘ ‘,N‘ ‘‘)-diiron(III), dichloro-((2-(2-pyridyl)ethyl)bis((2-pyridyl)methyl)amine-N,N‘,N‘ ‘,N‘ ‘‘)-iron(III) and (tetrachlorocatecholato-O,O‘)((2-(2-pyridyl)ethyl)bis((2-pyridyl)methyl)amine-N,N‘,N‘ ‘,N‘ ‘‘)-iron(III) are reported.