Heterolytic Bond Activation at Gold: Evidence for Gold(III) H-B, H-Si Complexes, H-H and H-C Cleavage

Rocchigiani, Luca, Budzelaar, Peter and Bochmann, Manfred (2019) Heterolytic Bond Activation at Gold: Evidence for Gold(III) H-B, H-Si Complexes, H-H and H-C Cleavage. Chemical Science, 10 (9). pp. 2633-2642. ISSN 2041-6520

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Abstract

The coordinatively unsaturated gold(III) chelate complex [(C^N-CH)Au(C6F5)]+ (1+) reacts with main group hydrides H-BPin and H-SiEt3 in dichloromethane solution at 70 °C to form the corresponding σ-complexes, which were spectroscopically characterized (C^N-CH = 2-(C6H3But)-6-(C6H4But)-pyridine anion; Pin = OCMe2CMe2O). In the presence of an external base such as diethyl ether, heterolytic cleavage of the silane H-Si bond leads to the gold hydrides [{(C^N-CH)AuC6F5}2(μ-H)]+ (2+) and (C^N-CH)AuH(C6F5) (5), together with spectroscopically detected [Et3Si-OEt2]+. The activation of dihydrogen also involves heterolytic H-H bond cleavage but requires a higher temperature ( 20 °C). H2 activation proceeds in two mechanistically distinct steps: the first leading to 2 plus [H(OEt2)2]+, the second to protonation of one of the C^N pyridine ligands and reductive elimination of C6F5H. By comparison, formation of gold hydrides by cleavage of suitably activated C-H bonds is very much more facile; e.g. the reaction of 1·OEt2 with Hantzsch ester is essentially instantaneous and quantitative at 30 °C. This is the first experimental observation of species involved in the initial steps of gold catalyzed hydroboration, hydrosilylation and hydrogenation and the first demonstration of the ability of organic C-H bonds to act as hydride donors towards gold.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: LivePure Connector
Date Deposited: 23 Jan 2019 12:56
Last Modified: 18 Mar 2020 02:32
URI: https://ueaeprints.uea.ac.uk/id/eprint/69660
DOI: 10.1039/c8sc05229h

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