Mechanism of ketone hydrosilylation using NHC–Cu(I) catalysts: a computational study

Vergote, Thomas; Gathy, Thomas; Nahra, Fady; Riant, Olivier; Peeters, Daniel; Leyssens, Tom

doi:10.1007/s00214-012-1253-4

Cited by 18 publications

(14 citation statements)

References 109 publications

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“…The mechanism proposed in Scheme is closely related to the mechanism for Cu I -catalyzed hydrosilylation [mechanism (a) in Scheme ], as proposed and refined by Ito, Lipshutz, Nolan, Leyssens, − and Bellemin-Laponnaz/Dedieu . Notably, the KIE for the hydrosilylation catalyzed by a Cu I phosphine alkoxide complex was found to be k H / k D = 2, similar to the positive KIE observed for the iron-catalyzed reaction ( vide supra ).…”

Section: Discussionsupporting

confidence: 63%

Mechanism of the Iron(II)-Catalyzed Hydrosilylation of Ketones: Activation of Iron Carboxylate Precatalysts and Reaction Pathways of the Active Catalyst

Bleith

Gade

2016

J. Am. Chem. Soc.

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A detailed mechanistic study of the catalytic hydrosilylation of ketones with the highly active and enantioselective iron(II) boxmi complexes as catalysts (up to >99% ee) was carried out to elucidate the pathways for precatalyst activation and the mechanism for the iron-catalyzed hydrosilylation. Carboxylate precatalysts were found to be activated by reduction of the carboxylate ligand to the corresponding alkoxide followed by entering the catalytic cycle for the iron-catalyzed hydrosilylation. An Eyring-type analysis of the temperature dependence of the enantiomeric ratio established a linear relationship of ln(S/R) and T(-1), indicating a single selectivity-determining step over the whole temperature range from -40 to +65 °C (ΔΔG(‡)sel, 233 K = 9 ± 1 kJ/mol). The rate law as well as activation parameters for the rate-determining step were derived and complemented by a Hammett analysis, radical clock experiments, kinetic isotope effect (KIE) measurements (kH/kD = 3.0 ± 0.2), the isolation of the catalytically active alkoxide intermediate, and DFT-modeling of the whole reaction sequence. The proposed reaction mechanism is characterized by a rate-determining σ-bond metathesis of an alkoxide complex with the silane, subsequent coordination of the ketone to the iron hydride complex, and insertion of the ketone into the Fe-H bond to regenerate the alkoxide complex.

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Section: Discussionsupporting

confidence: 63%

Mechanism of the Iron(II)-Catalyzed Hydrosilylation of Ketones: Activation of Iron Carboxylate Precatalysts and Reaction Pathways of the Active Catalyst

Bleith

Gade

2016

J. Am. Chem. Soc.

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“…Natural Population Analysis of the Natural Bond Orbitals (NBOs) indicates an increase in positive charge on the Cu center and a decrease in negative charge on the hydride for the transition state compared to the Cu-H monomer (Table S13 †), in agreement with previous calculations on (IPr)CuH. 64 The NBO analysis of the bonding in the transition state for propene insertion shows that the hydride is still mostly interacting with the Cu, whereas in the acetaldehyde transition state, the hydride has mostly transferred to the substrate, forming a C-H bond. The transition state for propene insertion is $9 kcal mol À1 higher than that for acetaldehyde insertion, which is consistent with our observation that insertion of a-olens is slower than insertion of activated carbonyls and has a different rate-limiting step.…”

Section: Dft Calculations Of Insertions Into Cu-hsupporting

confidence: 88%

“…In contrast, a previous study suggested formation of a weak van der Waals complex before insertion. 36,64 Substrate binding results in elongation of the Cu- H bond and bending of the C NHC -Cu-H angle from 180 to $110 . In the transition state, the Cu-H bond is elongated by $0.04Å compared to the CuH-substrate complex, and the C NHC -Cu-H bond angle increases (Tables S11 and S12 †).…”

Section: Dft Calculations Of Insertions Into Cu-hmentioning

confidence: 99%

“…Additionally, as discussed above, NBO analysis suggests that a partial positive charge forms at the Cu center during hydride transfer, in agreement with other studies on Cu-H systems. 63,64,[70][71][72] The transition state for insertion would therefore be destabilized by the less electron-donating IPr*Cl ligand, resulting in a decrease in k 2 .…”

Section: Dft Calculations Of Insertions Into Cu-hmentioning

confidence: 99%

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Accelerating the insertion reactions of (NHC)Cu–H via remote ligand functionalization

et al. 2021

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“…They postulate a hypervalente hydrosilicate as the active species . Leyssens et al and Nolan et al combined the benefits of both in their mechanism postulated for a copper(I) catalyzed hydrosilylation of ketones, which was supported by both, theoretical and experimental studies . Gade et al in 2008 published chiral iron(II) N,N,N ‐pincer complexes that gave good to excellent enantiomeric excesses in the catalytic hydrosilylation of ketones .…”

Section: Introductionmentioning

confidence: 85%

Iron(II) Complexes of Chiral Tridentate Nitrogen Donors and their Application in Catalytic Hydrosilylation Reactions

Groß

Omlor

Grimm

et al. 2020

Zeitschrift anorg allge chemie

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Enantiomerically pure, C2‐symmetric 2,6‐bis(pyrazol‐3‐yl) pyridine ligands were obtained by treatment of diethyl‐2,6‐pyridinedicarbonate with (1R,4R)‐(+)‐camphor in the presence of NaH followed by ring closure with hydrazine. After twofold N‐alkylation at the pyrazole rings, the addition of iron(II) chloride led to the according pentacoordinate dichloridoiron(II) complexes. All intermediates of the ligand synthesis, the ligands bearing NCH3 and NCH2C6H5 groups and the derived iron(II) complexes were structurally characterized by means of X‐ray structure analysis. In‐situ reaction with iron(II) carboxylates resulted in the formation of iron(II) carboxylate complexes, which turned out to be highly active in the hydrosilylation of acetophenone. However, even at room temperature, the enantiomeric excess of the product 1‐phenylethanol is poor. 57Fe Mössbauer spectroscopy gave an insight into the species formed during catalysis.

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Mechanism of ketone hydrosilylation using NHC–Cu(I) catalysts: a computational study

Cited by 18 publications

References 109 publications

Mechanism of the Iron(II)-Catalyzed Hydrosilylation of Ketones: Activation of Iron Carboxylate Precatalysts and Reaction Pathways of the Active Catalyst

Mechanism of the Iron(II)-Catalyzed Hydrosilylation of Ketones: Activation of Iron Carboxylate Precatalysts and Reaction Pathways of the Active Catalyst

Accelerating the insertion reactions of (NHC)Cu–H via remote ligand functionalization

Iron(II) Complexes of Chiral Tridentate Nitrogen Donors and their Application in Catalytic Hydrosilylation Reactions

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