Kinetic and thermodynamic acidity of hydrido transition-metal complexes. 4. Kinetic acidities toward aniline and their use in identifying proton-transfer mechanisms

Edidin, Robin T.; Sullivan, Jeffrey M.; Norton, Jack R.

doi:10.1021/ja00247a019

Cited by 100 publications

(87 citation statements)

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“…The selected pK a THF values given in Table 4 [117][118][119][120][121][122][123][124][125][126][127]. Norton and coworkers examined the thermodynamic and kinetic acidity of a series of transition metal complexes [128][129][130][131][132][133]. They found that the rates of H + transfer from transition metal hydrides can be quite slow when compared to organic and mineral acids of similar pK a 's [134].…”

Section: Metal-monohydride Species -"Hydride Ligands Can Be Acidic!"mentioning

confidence: 99%

The Activation of Dihydrogen

Tye

Darensbourg

Hall

2006

Activation of Small Molecules

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Section: Metal-monohydride Species -"Hydride Ligands Can Be Acidic!"mentioning

confidence: 99%

The Activation of Dihydrogen

Tye

Darensbourg

Hall

2006

Activation of Small Molecules

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“…The ratio of k HD to the reverse rate constant k DH will depend on the magnitude of the equilibrium isotope effect present. 32 The estimated equilibrium constant for the eq. 4, calculated for M = Pd 32,33,34…”

Section: Diethylamine -D (10)mentioning

confidence: 99%

Can Agostic Interaction Affect Regiochemistry of Carbopalladation? Reverse Regioselectivity in the Palladium-Catalyzed Dimerization of Aryl Acetylenes

2001

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Instrumentation. NMR spectra were recorded on Bruker Avance DRX-500 (500 MHz) instrument. IR spectra were recorded on Genesis II FT-IR Mattson spectrometer. Highresolution mass s pectra were recorded on CONSEPT/EXTREL mass spectrometer. GC/MS analyses were performed on a Hewlett Packard Model 6890 GC interfaced to a Hewlett Packard Model 5973 mass selective detector (15 m × 0.25 mm capillary column, HP-5MS). Column chromatography w as carried out employing Merck silica gel (Kieselgel 60, 63-200 µm), preparative TLC was performed on pre-coated PLC plates (Merck Kieselgel 60 F -254, 2 mm). All manipulations were conducted under argon atmosphere using a glove box or/and standard Schlenk technique. Chemicals. Compounds 1c,j,k,n 22 and 1d-h,l,m, 23 11 23,24 were prepared using known procedures. Deuterated compounds 8, 25 10 26 were prepared as described below. All other chemicals and solvents were purchased from Aldrich, Acros Organics and Fluorochem USA. Products 2a, 27 2b,c, 28 2f, 28,29 2j 3e are known compounds, and their analytical data are in agreement with the literature data. The spectral data for new compounds 1m, 2d,e,g,l are provided below.

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“…22 : stepwise PTET (pathway a, black), stepwise ETPT (pathway b, red), and concerted electron-proton transfer (CEPT) in a single kinetic step (pathway in blue). The thermodynamic data given are for the previously studied [CpWH(CO)3] in CH3CN (E 0 32-34 vs. Fc +/0 and pKa 35,36 ), with data for [(MeCp)WH(CO)3] in brackets (this study). (C) Kinetics for the three pathways, with the two kinetic limits for the step-wise mechanisms: either pre-equilibrium conditions or a rate-limiting first step.…”

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confidence: 99%

Accelerating proton-coupled electron transfer of metal hydrides in catalyst model reactions

et al. 2018

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Metal hydrides are key intermediates in catalytic proton reduction and dihydrogen oxidation. There is currently much interest in appending proton relays near the metal centre to accelerate catalysis by proton-coupled electron transfer (PCET). However, the elementary PCET steps and the role of the proton relays are still poorly understood, and direct kinetic studies of these processes are scarce. Here, we report a series of tungsten hydride complexes as proxy catalysts, with covalently attached pyridyl groups as proton acceptors. The rate of their PCET reaction with external oxidants is increased by several orders of magnitude compared to that of the analogous systems with external pyridine on account of facilitated proton transfer. Moreover, the mechanism of the PCET reaction is altered by the appended bases. A unique feature is that the reaction can be tuned to follow three distinct PCET mechanisms-electron-first, proton-first or a concerted reaction-with very different sensitivities to oxidant and base strength. Such knowledge is crucial for rational improvements of solar fuel catalysts.

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Kinetic and thermodynamic acidity of hydrido transition-metal complexes. 4. Kinetic acidities toward aniline and their use in identifying proton-transfer mechanisms

Cited by 100 publications

References 0 publications

The Activation of Dihydrogen

The Activation of Dihydrogen

Can Agostic Interaction Affect Regiochemistry of Carbopalladation? Reverse Regioselectivity in the Palladium-Catalyzed Dimerization of Aryl Acetylenes

Accelerating proton-coupled electron transfer of metal hydrides in catalyst model reactions

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