Role of Surface Basic Sites in Sonogashira Coupling Reaction over Ca5(PO4)3OH Supported Pd Catalyst: Investigation by Diffuse Reflectance Infrared Fourier Transform Spectroscopy

2017 ◽  
Vol 121 (40) ◽  
pp. 22191-22198 ◽  
Author(s):  
Vishali Bilakanti ◽  
Venu Boosa ◽  
Vijay Kumar Velisoju ◽  
Naresh Gutta ◽  
Sudhakar Medak ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Diffuse Reflectance ◽  
Coupling Reaction ◽  
Pd Catalyst ◽  
Sonogashira Coupling ◽  
Basic Sites ◽  
Sonogashira Coupling Reaction ◽  
Diffuse Reflectance Infrared ◽  
Supported Pd

A Merrifield resin supported Pd–NHC complex with a spacer(Pd–NHC@SP–PS) for the Sonogashira coupling reaction under copper- and solvent-free conditions

2015 ◽  
Vol 39 (3) ◽  
pp. 2333-2341 ◽  
Author(s):  
Sanjay N. Jadhav ◽  
Arjun S. Kumbhar ◽  
Sawanta S. Mali ◽  
Chang Kook Hong ◽  
Rajashri S. Salunkhe
Keyword(s):  
Coupling Reaction ◽  
Cross Coupling ◽  
Solvent Free ◽  
Sonogashira Coupling ◽  
Cross Coupling Reaction ◽  
Solvent Free Conditions ◽  
Sonogashira Coupling Reaction ◽  
Merrifield Resin ◽  
Polymer Supported ◽  
Supported Pd

Synthetic applications of a polymer supported air-stable palladium NHC complex with a spacer (catalyst6, Pd–NHC@SP–PS) and without a spacer (catalyst7, Pd–NHC@PS) have been studied for the Sonogashira cross-coupling reaction.

scholarly journals Poison or Promoter? Investigating the Dual-Role of Carbon Monoxide in Pincer-Iridium-Based Alkane Dehydrogenation Systems via Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy

2020 ◽  
Author(s):  
Boris Sheludko ◽  
Cristina Castro ◽  
Alan Goldman ◽  
Fuat E. Celik
Keyword(s):  
Carbon Monoxide ◽  
Fourier Transform ◽  
Diffuse Reflectance ◽  
Fourier Transform Spectroscopy ◽  
Iridium Complexes ◽  
Alkane Dehydrogenation ◽  
Mechanism Of Decomposition ◽  
Diffuse Reflectance Infrared

<p>Pincer-ligated iridium complexes of the <a>form [Ir(<sup>R4</sup>PCP)L] (<sup>R4</sup>PCP = κ<sup>3</sup>-C<sub>6</sub>H<sub>3</sub>-2,6-(XPR<sub>2</sub>)<sub>2</sub>; X = CH<sub>2</sub>, O; R = <i>t</i>Bu, <i>i</i>Pr) </a>have previously been shown competent for acceptorless alkane dehydrogenation when supported on silica. It was observed by post-catalysis solid-state NMR that silica-tethered <a>[Ir(C<sub>2</sub>H<sub>4</sub>)(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] </a>(<b>3-C<sub>2</sub>H<sub>4</sub></b>) was converted fully to [Ir(CO)(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] (<b>3-CO</b>) at 300 °C. In this work, the characterization of species under dehydrogenation reaction conditions far from equilibrium between butane and butenes (approach to equilibrium <i>Q</i>/<i>K</i><sub>eq</sub> = 0.3 at 300 °C) is performed with <i>operando </i>Diffuse Reflectance Infrared Fourier-Transform Spectroscopy (DRIFTS) to show the kinetics of species conversion from <b>3-C<sub>2</sub>H<sub>4</sub></b> to <b>3-CO</b>. It is further found that [IrClH(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] (<b>3-HCl</b>), a species considered to be a precatalyst for alkane dehydrogenation, is also fully converted to <b>3-CO</b>. A mechanism of decomposition is proposed that implicates surface silanol groups, while carbon monoxide acts as a “stabilizer” for the catalyst by promoting their reductive elimination and maintaining the complex in the I oxidation state. </p>

scholarly journals Poison or Promoter? Investigating the Dual-Role of Carbon Monoxide in Pincer-Iridium-Based Alkane Dehydrogenation Systems via Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy

2020 ◽  
Author(s):  
Boris Sheludko ◽  
Cristina Castro ◽  
Alan Goldman ◽  
Fuat E. Celik
Keyword(s):  
Carbon Monoxide ◽  
Fourier Transform ◽  
Diffuse Reflectance ◽  
Fourier Transform Spectroscopy ◽  
Iridium Complexes ◽  
Alkane Dehydrogenation ◽  
Mechanism Of Decomposition ◽  
Diffuse Reflectance Infrared

<p>Pincer-ligated iridium complexes of the <a>form [Ir(<sup>R4</sup>PCP)L] (<sup>R4</sup>PCP = κ<sup>3</sup>-C<sub>6</sub>H<sub>3</sub>-2,6-(XPR<sub>2</sub>)<sub>2</sub>; X = CH<sub>2</sub>, O; R = <i>t</i>Bu, <i>i</i>Pr) </a>have previously been shown competent for acceptorless alkane dehydrogenation when supported on silica. It was observed by post-catalysis solid-state NMR that silica-tethered <a>[Ir(C<sub>2</sub>H<sub>4</sub>)(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] </a>(<b>3-C<sub>2</sub>H<sub>4</sub></b>) was converted fully to [Ir(CO)(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] (<b>3-CO</b>) at 300 °C. In this work, the characterization of species under dehydrogenation reaction conditions far from equilibrium between butane and butenes (approach to equilibrium <i>Q</i>/<i>K</i><sub>eq</sub> = 0.3 at 300 °C) is performed with <i>operando </i>Diffuse Reflectance Infrared Fourier-Transform Spectroscopy (DRIFTS) to show the kinetics of species conversion from <b>3-C<sub>2</sub>H<sub>4</sub></b> to <b>3-CO</b>. It is further found that [IrClH(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] (<b>3-HCl</b>), a species considered to be a precatalyst for alkane dehydrogenation, is also fully converted to <b>3-CO</b>. A mechanism of decomposition is proposed that implicates surface silanol groups, while carbon monoxide acts as a “stabilizer” for the catalyst by promoting their reductive elimination and maintaining the complex in the I oxidation state. </p>

scholarly journals Poison or Promoter? Investigating the Dual-Role of Carbon Monoxide in Pincer-Iridium-Based Alkane Dehydrogenation Systems via Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy

2020 ◽  
Author(s):  
Boris Sheludko ◽  
Cristina Castro ◽  
Alan Goldman ◽  
Fuat E. Celik
Keyword(s):  
Carbon Monoxide ◽  
Fourier Transform ◽  
Diffuse Reflectance ◽  
Fourier Transform Spectroscopy ◽  
Iridium Complexes ◽  
Alkane Dehydrogenation ◽  
Mechanism Of Decomposition ◽  
Diffuse Reflectance Infrared

<p>Pincer-ligated iridium complexes of the <a>form [Ir(<sup>R4</sup>PCP)L] (<sup>R4</sup>PCP = κ<sup>3</sup>-C<sub>6</sub>H<sub>3</sub>-2,6-(XPR<sub>2</sub>)<sub>2</sub>; X = CH<sub>2</sub>, O; R = <i>t</i>Bu, <i>i</i>Pr) </a>have previously been shown competent for acceptorless alkane dehydrogenation when supported on silica. It was observed by post-catalysis solid-state NMR that silica-tethered <a>[Ir(C<sub>2</sub>H<sub>4</sub>)(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] </a>(<b>3-C<sub>2</sub>H<sub>4</sub></b>) was converted fully to [Ir(CO)(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] (<b>3-CO</b>) at 300 °C. In this work, the characterization of species under dehydrogenation reaction conditions far from equilibrium between butane and butenes (approach to equilibrium <i>Q</i>/<i>K</i><sub>eq</sub> = 0.3 at 300 °C) is performed with <i>operando </i>Diffuse Reflectance Infrared Fourier-Transform Spectroscopy (DRIFTS) to show the kinetics of species conversion from <b>3-C<sub>2</sub>H<sub>4</sub></b> to <b>3-CO</b>. It is further found that [IrClH(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)] (<b>3-HCl</b>), a species considered to be a precatalyst for alkane dehydrogenation, is also fully converted to <b>3-CO</b>. A mechanism of decomposition is proposed that implicates surface silanol groups, while carbon monoxide acts as a “stabilizer” for the catalyst by promoting their reductive elimination and maintaining the complex in the I oxidation state. </p>

scholarly journals Changes of Pd Oxidation State in Pd/Al2O3 Catalysts Using Modulated Excitation DRIFTS

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 116
Author(s):  
Gian Luca Chiarello ◽  
Ye Lu ◽  
Miren Agote-Arán ◽  
Riccardo Pellegrini ◽  
Davide Ferri
Keyword(s):  
Particle Size ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Oxidation State ◽  
Diffuse Reflectance ◽  
X Ray ◽  
Spectral Changes ◽  
Diffuse Reflectance Infrared ◽  
X Ray Absorption ◽  
Reversible Reduction

Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies significantly and reversibly under alternate pulses of CO or H2 and O2. Moreover, these baseline changes are proportional to the Pd content in Pd/Al2O3 samples exhibiting comparable Pd particle size. Similar measurements by X-ray absorption spectroscopy on a different 2 wt.% Pd/Al2O3 confirm that the baseline changes reflect the reversible reduction-oxidation of Pd. Hence, we demonstrate that changes in oxidation state of metal-based catalysts can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and that this behavior is part of the spectral changes that are returned by experiments under operando conditions.

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