Issue 4, 2020

Monoaurated vs. diaurated intermediates: causality or independence?

Abstract

Diaurated intermediates of gold-catalysed reactions have been a long-standing subject of debate. Although diaurated complexes were regarded as a drain of active monoaurated intermediates in catalytic cycles, they were also identified as the products of gold–gold cooperation in dual–activation reactions. This study shows investigation of intermediates in water addition to alkynes catalysed by [(IPr)Au(CH3CN)(BF4)]. Electrospray ionisation mass spectrometry (ESI-MS) allowed us to detect both monoaurated and diaurated complexes in this reaction. Infrared photodissociation spectra of the trapped complexes show that the structure of the intermediates corresponds to α-gold ketone intermediates protonated or aurated at the oxygen atom. Delayed reactant labelling experiments provided the half life of the intermediates in reaction of 1-phenylpropyne (∼7 min) and the kinetic isotope effects for hydrogen introduction to the carbon atom (KIE ∼ 4–6) and for the protodeauration (KIE ∼ 2). The results suggest that the ESI-MS detected monoaurated and diaurated complexes report on species with a very similar or the same kinetics in solution. Kinetic analysis of the overall reaction showed that the reaction rate is first-order dependent on the concentration of the gold catalyst. Finally, all results are consistent with the reaction mechanism proceeding via monoaurated neutral α-gold ketone intermediates only.

Graphical abstract: Monoaurated vs. diaurated intermediates: causality or independence?

Supplementary files

Article information

Article type
Edge Article
Submitted
08 Nov 2019
Accepted
12 Dec 2019
First published
13 Dec 2019
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2020,11, 980-988

Monoaurated vs. diaurated intermediates: causality or independence?

M. Anania, L. Jašíková, J. Zelenka, E. Shcherbachenko, J. Jašík and J. Roithová, Chem. Sci., 2020, 11, 980 DOI: 10.1039/C9SC05662A

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