Session Overview |
Wednesday, July 20 |
10:30 |
-Allyl Au(III) complexes and Au(I)/Au(III) catalytic allylation
* David Vesseur, CNRS/Université Paul Sabatier, Laboratoire Hétérochimie Fondamentale et Appliquée , France Au-catalyzed allylation reactions have started to emerge over the past 15 years. However it is striking to note that none of these gold-catalyzed allylation reactions operate via π-allyl complexes, as is classically the case with Pd, Ru and Ir catalysts. Only very recently the first gold π-allyl complexes were prepared and unambiguously authenticated in two parallel studies by Tilset and Bourissou. Recently it was also demonstrated that P^N hemilabile ligands such as MeDalphos trigger the oxidative addition of C(sp2) and C(sp)–X bonds (X = I; Br) to gold under mild conditions. Additionally the P^N ligands support π-coordination and activation of alkenes (and alkynes) at Au(I), as substantiated by the isolation of a variety of π-complexes and their application to the C3-alkylation of indoles. In this work, our aim was to combine the ability of P^N ligands to facilitate oxidative addition and π-coordination at gold to achieve Au(I)/Au(III) catalytic allylation reactions involving π-allyl Au(III) complexes. We found that (MeDalphos)AuCl complexes efficiently catalyze the cross-coupling of indoles with allyl substrates (Scheme 1). The observed selectivity for the branched product suggested a π-allyl intermediate. Further mechanistic investigations by performing every elementary step individually allowed for the characterization of the π-allyl Au(III) intermediate. This transformation represents the first example of a gold-catalyzed allylation reaction operating via a Au(I)/Au(III) cycle and involving π-allyl complexes. As such, this work bridges the gap between gold and the transition metals prevailing in catalytic allylation, namely palladium, ruthenium and iridium which all operate classically via π-allyl complexes. |
10:45 |
Cooperative redox enhancement effects in Au-Pd catalysis of alcohol and formyl oxidation
Xiaoyang Huang, Cardiff University, United Kingdom Ouardia Akdim, Cardiff University, United Kingdom * Mark Douthwaite, Cardiff University, United Kingdom Kai Wang, Cardiff University, United Kingdom Liang Zhao, Cardiff University, United Kingdom Richard Lewis, Cardiff University, United Kingdom * Samuel Pattisson , Cardiff University, United Kingdom Isaac Daniel, Cardiff University, United Kingdom Peter Miedziak, University of South Wales, United Kingdom David J. Morgan, Cardiff University, United Kingdom Qian He, National University of Singapore, Singapore Donald Bethell, Cardiff University, United Kingdom Steven McIntosh, Lehigh University, United States Christopher Kiely, Lehigh University, United States Graham J. Hutchings, Cardiff University, United Kingdom This talk will discuss a new observation made in the field of bimetallic catalysis: cooperative redox enhancement (CORE). Using alcohol/formyl oxidative dehydrogenation and oxygen reduction as model reactions, it is demonstrated that coupling two separate (but complimentary) processes can lead to significant catalytic rate enhancements. Over spatially separated Au and Pd, it is demonstrated that oxidative dehydrogenation predominantly proceeds on Au sites, while oxygen reduction proceeds on Pd sites. The conclusions derived are based on a combination of thermo- and electrochemical testing, and extensive characterisation was conducted to support the findings. The conclusions drawn have the potential to dramatically influence how researchers approach the design of multicomponent heterogeneous catalysts going forward. |
11:00 |
Enhanced Catalytic Activity Utilizing Strong Metal-Support Interactions (SMSI) - Isomerization of Alkenes over Hydroxyapatite Supported Gold Catalysts
* Akihiro Nakayama, Tokyo Metropolitan University, Japan Ryusei Sodenaga, Tokyo Metropolitan University, Japan Yuvaraj Gangarajula, Dalian Institute of Chemical Physics, China Ayako Taketoshi, Yokohama National University, Japan Toru Murayama, Tokyo Metropolitan University, Japan Tetsuo Honma, Japan Synchrotron Radiation Research Institute (JASRI), Japan Norihito Sakaguchi, Hokkaido University, Japan Tetsuya Shimada, Tokyo Metropolitan University, Japan Shinsuke Takagi, Tokyo Metropolitan University, Japan Masatake Haruta, Tokyo Metropolitan University, Japan Botao Qiao, Dalian Institute of Chemical Physics, China Junhu Wang, Dalian Institute of Chemical Physics, China Tamao Ishida, Tokyo Metropolitan University, Japan Precise control of the strong metal-support interaction (SMSI) between Au and hydroxyapatite (HAP) enhanced the soft Lewis acidity of Au. Partial substitution of cations in HAP could deposit smaller Au clusters than non-substituted HAP, which further enhanced the cationic properties of Au. Even though Au was partly covered by HAP thin layers for the catalyst with SMSI, the enhanced cationic properties of Au by SMSI surpassed a disadvantage of the decrease in the number of exposed surface Au atoms, resulting in higher catalytic activity than the same catalyst without SMSI. |
11:15 |
Lowering the operating temperature of Au acetylene hydrochlorination catalysts using oxidised carbon supports
* Samuel Pattisson, Cardiff Catalysis Institute, United Kingdom Simon Dawson, Cardiff Catalysis Institute, United Kingdom Grazia Malta, Cardiff Catalysis Institute, United Kingdom Nicholas Dummer, Cardiff Catalysis Institute, United Kingdom Louise Smith, Cardiff Catalysis Institute, United Kingdom Anna Lazaridou, Cardiff Catalysis Institute, United Kingdom David J. Morgan, Cardiff Catalysis Institute, United Kingdom Simon Freakley, University of Bath, United Kingdom Simon Kondrat, Loughborough University, United Kingdom Joost Smit, Johnson Matthey, United Kingdom Peter Johnston, Johnson Matthey, United Kingdom Graham J. Hutchings, Cardiff Catalysis Institute, United Kingdom Gold catalysts have recently been commercialized as a replacement for the highly toxic mercuric chloride acetylene hydrochlorination catalyst. This study investigates the effect of varying levels of support oxidation on the activity of gold catalysts with a focus on producing catalysts which can operate at lower temperatures in existing reactors. |
11:30 |
New trends in gold catalysis for the preparation of propargylamines and 1,3-thiazines
Stephany Zárate-Roldán , INSTITUTO DE SINTESIS QUIMICA Y CATALISIS HOMOGENEA (CISC-UNIVERSITY OF ZARAGOZA), Spain Guillermo Canudo-Barreras, INSTITUTO DE SINTESIS QUIMICA Y CATALISIS HOMOGENEA (CISC-UNIVERSITY OF ZARAGOZA), Spain M. Concepción GImeno, INSTITUTO DE SINTESIS QUIMICA Y CATALISIS HOMOGENEA (CISC-UNIVERSITY OF ZARAGOZA), Spain * Raquel P. Herrera, INSTITUTO DE SINTESIS QUIMICA Y CATALISIS HOMOGENEA (CISC-UNIVERSITY OF ZARAGOZA), Spain In this event, we would like to present our recent works focused on gold catalysis for the preparation of final high-added value compounds. The formation of propargylamines and 1,3-thiazinane will be discussed. Both species are important for their potential biological properties |
11:45 |
Observing surface intermediates during selective hydrogenation reactions using SHINERS
* Shaoliang Guan, Cardiff University, United Kingdom Gary Attard, University of Liverpool, United Kingdom Andy Wain, National Physical Laboratory, United Kingdom In situ electrochemistry and Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was applied to a few studies in monitoring the catalytic process of asymmetric hydrogenation of pro-chiral ketones and semi-hydrogenation of acetylenic bonds on Pt single crystal electrodes. This allows us to understand the structure-activity relationship so that highly efficient catalysts could be designed. |