Carbon-sulfur bond formation by reductive elimination of gold(III) thiolates

Currie, Lucy, Rocchigiani, Luca, Hughes, David L. and Bochmann, Manfred (2018) Carbon-sulfur bond formation by reductive elimination of gold(III) thiolates. Dalton Transactions, 47 (18). pp. 6333-6343. ISSN 1477-9226

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Abstract

Whereas the reaction of the gold(III) pincer complex (C^N^C)AuCl with 1-adamantyl thiol (AdSH) in the presence of base affords (C^N^C)AuSAd, the same reaction in in the absence of base leads to formation of aryl thioethers as the products of reductive elimination of the Au-C and Au-S ligands (C^N^C = dianion of 2-6-diphenylpyridine or 2-6-diphenylpyrazine). Although high chemical stability is usually taken as a characteristic of pincer complexes, results show that thiols are capable of cleaving one of the pincer Au-C bonds. This reaction is not simply a function of S-H acidity, since no cleavage takes place with other more acidic X-H compounds, such as carbazole, amides, phenols and malonates. The reductive C-S elimination follows a second-order rate law, d[1a]/dt = k[1a][AdSH] and requires at least two molar equivalents of RSH per Au. Reductive elimination is enabled by displacement of the N-donor by thiol; this provides the conformational flexibility necessary for C-S bond formation to occur. Alternatively, reductive C-S bond formation can be induced by reaction of pre-formed thiolates (C^N^C)AuSR with a strong Brønsted acid, followed by addition of SMe2 as base. On the other hand, treatment of (C^N^C)AuR (R = Me, aryl, alkynyl) with thiols under similar conditions leads to selective C-C rather than C-S bond formation. The reaction of (C^N^C)AuSAd with H+ in the absence of a donor ligand affords the thiolato-bridged complex [{(C^N-CH)Au(μ-SAd)}2]2+ which was crystallographically characterised.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: Pure Connector
Date Deposited: 04 Apr 2018 08:30
Last Modified: 26 May 2020 00:02
URI: https://ueaeprints.uea.ac.uk/id/eprint/66650
DOI: 10.1039/C8DT00906F

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