.
Angewandte
Communications
DOI: 10.1002/anie.201303450
Gold Complexes
À
Direct syn Insertion of Alkynes and Allenes into Au Si Bonds**
Maximilian Joost, Pauline Gualco, Sonia Mallet-Ladeira, Abderrahmane Amgoune,* and
Didier Bourissou*
Over the past decade, gold catalysis has emerged as a very
active field in homogeneous catalysis. Nowadays gold com-
plexes are no longer considered as chemically inert species,
but appear as powerful and versatile catalysts for a broad
À
À
range of transformations for the formation of C C and C X
bonds.[1] All these synthetic developments have stimulated
interest in the formation, stability, and reactivity of organo-
gold complexes. In particular, several key intermediates of p-
activation processes have been detected in situ or even
isolated in the last few years, thereby providing valuable
mechanistic insights.[2–5] Recent studies have also shown that
the reactivity of gold complexes extends well beyond the
coordination/activation of p bonds, and compelling evidence
has been reported for gem-diauration of alkynes and
arenes,[6,7] two-electron redox transformations,[8] as well as
transmetallation reactions.[9]
The reactivity of gold complexes seems more versatile
than anticipated, but compared with the other transition
metals, our knowledge of gold chemistry is still in its infancy
and much remains to be explored. This is particularly true for
insertion reactions that are ubiquitous in transition metal
chemistry but very elusive with gold.[10–13] Among the relevant
literature, the few recent contributions depicted in Scheme 1
are particularly noteworthy. Reversible addition of the N-
heterocyclic carbene (NHC) gold fluoride I across several
alkynes was reported by Sadighi and co-workers.[14] The
vinylgold complex isolated from the reaction of I with 1-
phenyl-1-propyne displays trans arrangement of the gold and
fluoride atoms, and the reaction was thus proposed to proceed
through displacement of the fluoride, followed by nucleo-
philic anti addition to the p-coordinated alkyne. The isolation
of gold hydride complexes II and III by Tsui, Sadighi, and
Bochmann[15] has also stimulated studies on insertion reac-
tions. Upon reaction with dimethyl acetylenedicarboxylate,
the NHC gold(I) hydride II readily afforded the trans addition
Scheme 1. Reactions of gold fluoride, gold hydride, and gold silyl
complexes with alkynes and allenes.
product. In contrast, the pincer gold(III) hydride III was
unreactive towards dimethyl acetylenedicarboxylate; but with
allenes, vinylgold complexes were obtained smoothly and
regiospecifically. Last but not least, Hashmi, Kçppel, and co-
workers investigated experimentally and computationally the
reaction of complex II with ethene,[16] and came to the
À
conclusion that insertion of olefins into the Au H bond is not
a favorable process.[17] Thus, no definite proof for a true
insertion reaction at gold has been reported to date, and the
ability of gold complexes to undergo syn insertion can be
legitimately questioned.
Our recent work on the activation of s-SiSi bonds at
gold[8e,f] prompted us to investigate the feasibility of such
[18]
À
insertion reactions into Au Si bonds. Here we report that
[*] M. Joost, Dr. P. Gualco, Dr. A. Amgoune, Dr. D. Bourissou
Laboratoire Hꢀtꢀrochimie Fondamentale et Appliquꢀe
Universitꢀ Paul Sabatier/CNRS UMR 5069
phosphine gold(I) silyl complexes indeed undergo syn inser-
tion of alkynes and allenes. The stereo- and regioselectivity of
the process has been studied, as well as the reactivity of the
ensuing b-silyl vinylgold(I) complexes.
118 Route de Narbonne, 31062 Toulouse Cedex 09 (France)
E-mail: amgoune@chimie.ups-tlse.fr
Gold silyl complexes have been synthesized and structur-
ally characterized early on by Schubert and co-workers and
Schmidbaur and co-workers,[19] but very little is known about
their reactivity.[20,21] Sterically demanding substituents are
usually necessary to impart reasonable stability, and we thus
worked on (Ph3P)Au-SitBuPh2 (1). By following the reported
methodology,[19] that is coupling the corresponding phosphine
gold chloride with lithiosilane, complex 1 was obtained in
91% yield.[22] Its ability to undergo insertion reactions was
S. Mallet-Ladeira
Institut de Chimie de Toulouse (FR 2599)
118 Route de Narbonne, 31062 Toulouse Cedex 09 (France)
[**] Financial support from the Centre National de la Recherche
Scientifique, the Universitꢀ de Toulouse, and the Agence Nationale
de la Recherche (ANR-10-BLAN-070901) is gratefully acknowledged.
Supporting information for this article is available on the WWW
2
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2013, 52, 1 – 5
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