Hydrogen atom vs electron transfer in catecholase-mimetic oxidations by superoxometal complexes. Deuterium kinetic isotope effects

TitleHydrogen atom vs electron transfer in catecholase-mimetic oxidations by superoxometal complexes. Deuterium kinetic isotope effects
Publication TypeJournal Article
Year of Publication2005
AuthorsSimandi, TM, May, Z, Szigyártó, ICs., Simandi, LI
JournalDALTON TRANSACTIONS
Pagination365-368
Type of ArticleArticle
ISSN1477-9226
Abstract

Dioximato-cobalt(II), -iron(II) and -manganese(II) complexes ( 1) ( 6), acting as functional catecholase and phenoxazinone synthase models, exhibit a deuterium kinetic isotope effect predicted by theory (k(4H)/k(4D) less than or equal to 3) in the catalytic oxidative dehydrogenation of 3, 5-di-tert-butylcatechol and 2-aminophenol by O-2. KIEs in the range of (k(4H)/k(4D) approximate to 1.79-3.51) are observed with (1) and(2) as catalysts, pointing to hydrogen atom transfer in the rate-determining step from the substrate hydroxy group to the metal-bound superoxo ligand. Less significant KIEs (1.06-1.20) are exhibited by catalysts systems (3)-(6), indicating that proton-coupled electron transfer is the preferred route in those cases.

DOI10.1039/b412500b