Abstract
Thiols and amines, which are common heteroatom nucleophiles in gold-catalysed reactions, are known to dampen the reactivity of gold catalysts. In this article, the identity and activity of gold(I) catalysts in the presence of thiols and amines is investigated. In the presence of thioacid, thiophenol and thiol, digold with bridging thiolate complexes [{Au(L)}2(μ-SR)][SbF6] are formed and have been fully characterised by NMR and X-ray crystallography. In the presence of amines and anilines, complexes [LAu-NH2R][SbF6] are formed instead. All new isolated gold complexes were investigated for their catalytic activity in order to compare the level of deactivation in each species.
Highlights
In less than a decade, homogenous gold catalysis has undergone a transformation from rarity to an incredibly active and rapidly evolving field of research.[1]
In a recent publication describing the gold(I)-catalysed reactions of thiols with cyclopropenes, we briefly disclosed that [{Au(L)}2(μ-SR)][SbF6] species are likely to be the thiol-deactivated complexes formed in the reaction.2f,12 In this article, we present our full investigations into the nature of the gold
Catalyst and was chosen for our studies because it was previously found to have the best catalytic activity in the presence of thiols.2f The second reason for using 8 is one of practicality: the displacement of the MeCN in the complex by an S-nucleophile can be clearly monitored by 1H NMR spectroscopy, indicated by the appearance of unbound MeCN in the solution
Summary
In less than a decade, homogenous gold catalysis has undergone a transformation from rarity to an incredibly active and rapidly evolving field of research.[1]. In order to explain these observations, we were keen to elucidate the structure and activity of the actual gold(I) species involved in these reactions.[8,9] So far, not much effort has been made to isolate, characterise[10] and investigate the catalytic properties of these species. Heteroatom nucleophiles such as RSH and RNH2 are commonly used in gold-catalysed reactions,1a,d so a better understanding of the nature and activity of gold(I) catalysts in the presence of these nucleophiles will be invaluable if we are to better understand the mechanisms of gold-catalysed reactions.[11]. Complexes of type [{Au(L)}2(μ-SR)][SbF6] and [LAuNH2R][SbF6] have never been studied in the context of catalysis, so 6a–c and 7a–c were investigated for their catalytic activity in an effort to compare the level of deactivation in each of these species
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