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Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies.
Eur J Inorg Chem ; 2019(15): 2146-2153, 2019 Apr 24.
Article en En | MEDLINE | ID: mdl-31787843
ABSTRACT
The reduction of CO2 to formic acid by transition metal hydrides is a potential pathway to access reactive C1 compounds. To date, no kinetic study has been reported for insertion of a bridging hydride in a weak-field ligated complex into CO2; such centers have relevance to metalloenzymes that catalyze this reaction. Herein, we report the kinetic study of the reaction of a tri(µ-hydride)triiron(II/II/II) cluster supported by a tris(ß-diketimine) cyclophane (1) with CO2 monitored by 1H-NMR and temperature-controlled UV-vis spectroscopy. We found that 1 reacts with CO2 to traverse the reported monoformate (1-CO 2 ) and a diformate complex (1-2CO 2 ) at 298 K in toluene, and ultimately yields the triformate species (1-3CO 2 ) at elevated temperature. The second order rate constant, H/D kinetic isotope effect, ∆H ‡,and ∆S ‡for formation of 1-CO 2 were determined as 8.4(3)×10-4 M-1·s-1, 1.08(9), 11(1) kcal·mol-1, and -3(1)×10 cal·mol-1·K-1, respectively at 298 K. These parameters suggest that CO2 coordination to the iron centers does not coordinate prior to the rate controlling step whereas Fe-H bond cleavage does.
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Idioma: En Revista: Eur J Inorg Chem Año: 2019 Tipo del documento: Article

Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Idioma: En Revista: Eur J Inorg Chem Año: 2019 Tipo del documento: Article
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