Dehydrogenation of formic acid using iridium-NSi species as catalyst precursors

Guzmán, Jefferson ; Urriolabeitia, Asier (Universidad de Zaragoza) ; Polo, Víctor (Universidad de Zaragoza) ; Fernández-Buenestado, Marta ; Iglesias, Manuel ; Fernández-Álvarez, Francisco J. (Universidad de Zaragoza)

Resumen: Using a low loading of the iridium(III) complexes [Ir(CF3SO3)(κ2-NSiiPr)2] (1) (NSiiPr = (4-methylpyridin-2-yloxy)diisopropylsilyl) and [{Ir(κ2-NSiMe)2}2(μ-CF3SO3)2] (2) (NSiMe = (4-methylpyridin-2-yloxy)dimethylsilyl) in the presence of Et3N, it has been possible to achieve the solventless selective dehydrogenation of formic acid. The best catalytic performance (TOF5 min ≈ 2900 h−1) has been achieved with 2 (0.1 mol%) and Et3N (40 mol% to FA) at 373 K. Kinetic studies at variable temperatures show that the activation energy of the 2-catalyzed process at 353 K is 22.8 ± 0.8 kcal mol−1. KIE values of 1.33, 2.86, and 3.33 were obtained for the 2-catalyzed dehydrogenation of HCOOD, DCOOH, and DCOOD, respectively, in the presence of 10 mol% of Et3N at 353 K. These data show that the activation of the C–H bond of FA is the rate-determining step of the process. A DFT mechanistic study for the catalytic cycle involving hydride abstraction from the formate anion by the metal, assisted by a molecule of formic acid, and heterolytic H2 formation has been performed. Moreover, the presence of Ir-formate intermediates was identified by means of NMR studies of the catalytic reactions in thf-d8 at 323 K. In all the cases, the decomposition of the catalyst to give unactive crystalline iridium NPs was observed.

Idioma: Inglés

DOI: 10.1039/d1dt04335h

Año: 2022

Publicado en: Dalton Transactions 51, 11 (2022), 4386-4393
ISSN: 1477-9226

Factor impacto JCR: 4.0 (2022)

Categ. JCR: CHEMISTRY, INORGANIC & NUCLEAR rank: 7 / 42 = 0.167 (2022) - Q1 - T1

Factor impacto CITESCORE: 7.1 - Chemistry (Q1)

Factor impacto SCIMAGO: 0.79 - Inorganic Chemistry (Q1)

Financiación: info:eu-repo/grantAgreement/ES/DGA-FSE/E42-20R
Financiación: info:eu-repo/grantAgreement/ES/MCIU/PGC2018-099383-B-I00
Financiación: info:eu-repo/grantAgreement/ES/MICINN/RTI2018-099136-A-I00

Tipo y forma: Artículo (PostPrint)

Área (Departamento): Área Química Inorgánica (Dpto. Química Inorgánica)
Área (Departamento): Área Química Física (Dpto. Química Física)