Isolation of a Reactive Tricoordinate α-Oxo Gold Carbene Complex

Article abstract of DOI:10.1002/anie.201711647

The [(P,P)Au=C(Ph)CO₂Et]⁺ complex 3 [where (P,P) is an o-carboranyl diphosphine ligand] was prepared by diazo decomposition at ?40 °C. It is the first α-oxo gold carbene complex to be characterized. Its crystallographic structure was determined and DFT calculations have been performed, unraveling the key influence of the chelating (P,P) ligand. The gold center is tricoordinate and the electrophilicity of the carbene center is decreased. Complex 3 mimics transient α-oxo gold carbenes in a series of catalytic transformations, and provides support for the critical role of electrophilicity in the chemoselectivity of phenol functionalization (O?H vs. C?H insertion).

Full text of DOI:10.1002/anie.201711647

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Accepted Article
Title: Isolation of a Reactive Tricoordinate alpha-Oxo Gold Carbene
Complex
Authors: Abdallah Zeineddine, Feriel Rekhroukh, E. Daiann
Sosa Carrizo, Sonia Mallet-Ladeira, Karinne Miqueu,
Abderrahmane Amgoune, and Didier Bourissou
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201711647
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10.1002/anie.201711647
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COMMUNICATION
Isolation of a Reactive Tricoordinate -Oxo Gold Carbene
Complex
Abdallah Zeineddine, Feriel Rekhroukh, E. Daiann Sosa Carrizo, Sonia Mallet-Ladeira, Karinne
Miqueu, Abderrahmane Amgoune and Didier Bourissou*
Abstract: The [(P,P)Au=C(Ph)CO2Et]+ complex 3 [where (P,P) is
an o-carboranyl diphosphine ligand] was prepared by diazo
decomposition at –40°C. It is the first -oxo gold carbene complex to
be characterized. Its crystallographic structure was determined and
DFT calculations have been performed, unraveling the key influence
of the chelating (P,P) ligand. The gold center is tricoordinate and the
electrophilicity of the carbene center is reduced. Complex 3 mimics
transient -oxo gold carbenes in a series of catalytic transformations,
and enables to support the critical role of electrophilicity in the
chemoselectivity of phenol functionalization (O–H vs C–H insertion).
tricoordinate gold complexes are formed with the (P,N) ligands,
reducing the electrophilicity of the carbene center.
Although their existence and involvement as key intermediates
leave little doubt,[9] -oxo gold carbene complexes have remained
elusive species so far.[10] They have resisted isolation and
spectroscopic characterization, even with the (P,N) bidentate
ligands that are supposed to form more stable tricoordinate
species. Nevertheless, a variety of gold carbenoids with or without
heteroatom substituents have been experimentally authenticated
over the last 10 years and their bonding situation (gold carbenes
vs gold-stabilized carbocations) has attracted considerable
attention.[11,12]
We have recently reported unprecedented reactivity
(oxidative addition)[13] and bonding situation (enhanced -
backdonation)[14] of gold(I) complexes induced by bidentate
ligands. These results prompted us to envision to generate
tricoordinate -oxo carbene complexes by reacting -diazo esters
with gold precursors featuring hemilabile (P,N) or chelating (P,P)
ligands (Figure 1c). This approach proved successful and we
report here the characterization of an -oxo gold carbene. Its
bonding has been thoroughly analyzed and the influence of the
bidentate ligand has been unraveled. In addition, reactivity
studies (catalytic carbene transfer reactions) show that this
species can indeed be considered as a mimic of transient -oxo
carbene complexes.
Soon after the ability of gold complexes to activate -bonds
towards nucleophilic addition was discovered and the “gold rush”
in homogeneous catalysis started, the easy generation and
versatile reactivity of -oxo gold carbene complexes was
recognized, opening a new facet in gold catalysis.[1] Following the
pioneering work of P. Pérez and S. Nolan,[2] the reaction of -
diazo carbonyl compounds with phosphine and NHC gold(I)
precursors proved to be a very efficient and general route to highly
electrophilic -oxo carbene complexes (Figure 1a). Catalytic
applications thereof rapidly flourished and
a
variety of
synthetically useful carbene transfer[2-5] and coupling[6] reactions
have been reported: X–H (X = O, N, S…) insertion,[2] C–H
insertion,[2a,3] cyclopropanation[2,4] and related cycloadditions[5]…
The reaction of -alkyne gold complexes with N-oxides, as
developed by L. Zhang, provides another route to -oxo carbenes
(Figure 1b).[7] Remarkably, bidentate (P,N) and (P,S) ligands
mitigate the reactivity of the gold carbene: the chemoselectivity of
intermolecular reactions is increased and the scope of catalytic
transformations is significantly expanded.[8] It is proposed that
[]
A. Zeineddine, Dr. F. Rekhroukh, Dr. A. Amgoune, Dr. D. Bourissou
CNRS / Université Paul Sabatier, Laboratoire Hétérochimie
Fondamentale et Appliquée (LHFA, UMR 5069). 118 Route de
Narbonne, 31062 Toulouse Cedex 09 (France)
E–mail: dbouriss@chimie.ups–tlse.fr
Homepage: http://hfa.ups-tlse.fr/LBPB/index_lbpb.htm
Dr E. D. Sosa Carrizo, Dr K. Miqueu
CNRS/UNIV PAU & PAYS ADOUR, Institut des Sciences
Analytiques et de Physico-Chimie pour l’Environnement et les
Matériaux (IPREM, UMR 5254). Hélioparc, 2 Avenue du Président
Angot, 64053 Pau Cedex 09 (France)
Figure 1. Known synthetic routes to transient oxo gold carbene complexes
and strategy envisioned in this work.
S. Mallet-Ladeira
Institut de Chimie de Toulouse (FR 2599)
118 Route de Narbonne, 31062 Toulouse Cedex 09 (France)
Cationic gold complexes derived from Me-Dalphos, a (P,N)
bidentate ligand, were first reacted with the -diazo acetate
PhC(=N2)CO2Et 1 with the aim to generate and characterize a
(P,N) -oxo gold carbene complex akin to those proposed by
Zhang et al (Scheme 1).[8] Despite in situ and low temperature
Supporting information for this article is given via a link at the end of
the document.
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10.1002/anie.201711647
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COMMUNICATION
NMR monitoring, only messy reactions were observed and the
desired species A could not be detected. We then turned our
attention to the o-carboranyl diphosphine ligand (DPCb), which
we have previously shown to chelate gold[13a,b] and enhance
backdonation, resulting in stable and unusual CO and
diphenylcarbene complexes.[14] The diazo compound 1 was thus
reacted with the [(P,P)AuNTf2] complex 2 at –40°C. Dinitrogen
fragment and the substituents at phosphorus. The AuC bond
distance (1.961(2) Å) is in the shortest range of those reported for
gold carbene complexes.[11,14] Noteworthy, the phenyl ring is
nearly co-planar with the carbene center and the Ccarbene-Cipso
bond is slightly contracted (1.448(4) Å) indicating that the -
system of the aromatic ring participates in the stabilization of the
carbene species. The ester moiety points away from the
immediately evolved and the reaction mixture turned to dark violet, electrophilic gold center, no sign of O•••Au interaction is noticed
suggesting the formation of a carbene species. 31P NMR
monitoring of the reaction indicated instantaneous formation of a
new species displaying a single resonance signal at 138.9 ppm,
indicative of symmetric coordination of the phosphorus atoms to
gold. In contrast with that previously observed from the reaction
of 2 with diphenyldiazomethane, the resulting product is thermally
unstable and could not be isolated (decomposition occurs rapidly
above 0 °C). However, 3 was fully characterized by multinuclear
NMR spectroscopy at low temperature and unequivocally
assigned as the targeted -oxo gold carbene complex
[(P,P)Au=C(Ph)CO2Et]+ (Scheme 1).
(the corresponding distances exceed 3.5 Å).
Thus, the use of the chelating (P,P) ligand allowed the
isolation of 3, the first -oxo gold carbene complex to be
experimentally characterized. DFT calculations were carried out
on the actual species at the B3PW91/SDD+f(Au), 6-31G**(other
atoms) level of theory to shed light into its bonding situation and
to assess the role of the ancillary ligand in its stabilization.[15] The
optimized geometry nicely reproduces that determined
crystallographically. The computed 13C NMR chemical shift of the
carbene atom (292.6 ppm) and the associated JPC coupling
constant (107.0 Hz) also compare well with experimental values.
The frontier orbitals HOMO and LUMO of 3 (Figure 2) mainly
correspond to bonding and anti-bonding combinations between
the occupied dxz(Au) orbital at gold and the vacant 2p(C) orbital
at the carbene center. Natural Bond Order (NBO) analysis
revealed C=C(Ph)2p(C) and nC*C=O (CO) donor-acceptor
interactions (65.6 and 16.0 kcal/mol, respectively), indicative of
the push-pull nature of the -oxo carbene. In addition, we noticed
significant dxz(Au)2p(C) backdonation (18.2 kcal/mol), which is
also apparent in the significant contribution of the 2p(C) orbital
(12.1%) in the corresponding Natural Localized Molecular Orbital
(NLMO). Charge transfer (as estimated from the NBO charges)
indicates small transfer of electron density between the
[C(Ph)CO2Et] carbene moiety and [(P,P)Au]+ fragment (CT = –
0.07 e). Charge-decomposition analysis (CDA)[16] provides an
estimation of the relative contributions of CcarbeneAu donation
and AuCcarbene backdonation, with a d/b ratio = 1.76.[15]
Scheme 1. Synthesis and molecular structure of the -oxo gold carbene
complex 3. Thermal ellipsoids drawn at 50% probability, hydrogen atoms,
counter anion and solvate molecules are omitted. Selected bond lengths (Å)
and angles (°): Au-C1 1.961(2), C1-C2 1.489(4), C1-C3 1.448(4), PAuP
90.57(2).
The formation of the carbene species 3 is clearly apparent by
13C NMR spectroscopy with a characteristic resonance signal at 
283.4 ppm appearing as a triplet (JCP = 87.6 Hz). This chemical
shift is in the range of previously characterized gold(I) carbenoid
complexes (225-321 ppm).[11] In addition, the resonance signals
for the carbonyl moiety and all of the Carom of the phenyl ring,
except Cpara, appear as triplets, with JCP coupling constants
ranging from 7.6 to 15.8 Hz.[15]
Crystals of 3 were obtained by slow diffusion of pentane into
a concentrated solution of dichloromethane at –30°C, and its
molecular structure was analyzed by X-ray diffraction (Scheme 1).
2-coordination of the DPCb ligand to gold in a symmetric manner
results in a tricoordinate -oxo gold carbene complex. The gold
center adopts trigonal planar geometry with a PAuP bite angle of
90.26(4)° and PAuC bond angles of 130.92(8) and 138.47(8)°.
The carbene center is perfectly planar and perpendicular to the
PAuP coordination plane (with a twist angle of 87.15°). This
orientation minimizes steric repulsions between the carbene
Figure 2. HOMO (left) and LUMO (right) of the -oxo gold carbene complex 3.
Comparison with the corresponding undetectable (P,N)
complex A (Figure 3) highlights the influence of the ligand. The
Au•••N distance (2.53 Å) in the optimized geometry of A is
relatively long [46 % shorter than the rVdW (3.07 Å)[17] but 22%
longer than the rcov (2.07 Å)[18]]. Consistently, the P-Au-Ccarbene
arrangement is almost linear (163.3°). In the absence of
significant N to Au coordination, the gold center is electron-
deficient, much more than that of the [(P,P)Au]+ fragment. As a
consequence, a significant transfer of electron density from the
carbene to the metal (CT = 0.8 e) is observed and the donation /
backdonation ratio (2.16) is significantly higher for complex A than
for 3. This bonding situation explains the high electrophilicity and
instability of the carbene complex A. Comparatively, the chelating
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10.1002/anie.201711647
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(P,P) ligand brings much more stability thanks to the formation of
a tricoordinate -oxo gold carbene species.
To confirm the critical role of the gold carbene electrophilicity
on the C–H vs O–H insertion selectivity, we envisioned to
introduce electron-withdrawing groups in remote positions of the
phenyl substituent of the carbene.[22,23] We selected the bis(CF3)
diazo compound 1-CF3 and tested its reactivity towards phenol
under the same conditions than for 1 (5 mol% of complex 2 at RT,
Scheme 3). The reaction was quantitative and about 4 times
faster than with 1 (30 min vs 2 h). In this case, the functionalized
phenol 6b-CF3 was actually obtained as major product (68%
yield) along with a minor amount of the arylether 6a-CF3 (32%).
Figure 3. Optimized structure of the (P,N) -oxo carbene complex A (left) with
key geometric (distances in Å and bond angles in °) and bonding parameters,
as to compare with the related (P,P) carbene complex 3 (right). The substituents
at P have been simplified for clarity.
The next step of the study was to assess to which extent the
chelating coordination of the (P,P) ligand affects the reactivity of
the carbene complex. In other words, is it meaningful to consider
complex 3 as a mimic of transient -oxo gold carbene complexes?
To this end, the behavior of 3 in a few representative catalytic
reactions was tested (Scheme 2). First, styrene was reacted with
the -diazo ester 1 in the presence of 5 mol% of the [(P,P)AuNTf2]
complex 2. Cyclopropane 4[2b] was thereby obtained in 58% yield
after 64 hours at room temperature (RT). The carbene 3 also
reacted readily with the phosphine-borane Ph3PBH3 to give the
B–H insertion product 5[19] (56% yield after 30 minutes at RT). We
then turned to the reaction with phenol and observed selective
formation of the aryl ether 6a (60% yield after 2 hours). Such O–
H insertion reactivity parallels that of Pd, Cu, Rh, Fe… carbene
complexes derived from -diazo esters,[20] but differs from that
reported recently for P-ligated gold(I) complexes.[3f,g] Indeed, it
was discovered in 2014 that gold carbene complexes possess
unique propensity to insert into the para C–H bond, enabling the
direct and selective functionalization of unprotected phenols.
Chemoselectivity for C–H vs O–H insertion is optimal with
electron-deprived phosphite ligands, which increase the
electrophilicity of the -oxo gold carbene intermediate. As
mentioned above, the (P,P) ligand strengthens AuCcarbene
backdonation and decreases the electrophilicity of the carbene,
which apparently switches the chemoselectivity of gold towards
O–H insertion and leads in this case to the formation of the aryl
ether.[21]
Scheme 3. O-H vs C-H functionalization of phenol with the aryl diazo ester 1-
CF3 catalyzed by complex 2.
To rationalize the different selectivity observed with 1 and 1-
CF3, the electronic structure of the -oxo carbene complex 3-CF3
was analyzed. First, it should be noticed that the 3-CF3 could be
detected by 31P NMR spectroscopy at –90°C. However, it is much
less stable than 3 and decomposes very rapidly even at this
temperature. According to DFT calculations, the geometric
features and bonding situation of 3-CF3 parallel those of 3.[15] Here
also, significant backdonation from gold to the carbene center is
apparent in NBO [dxz(Au)2p(C) donor-acceptor interaction of
18.8 kcal/mol, 13.3% contribution of 2p(C) in the corresponding
NLMO] and CDA analysis (d/b = 1.70). The most noticeable
difference is in fact the energy levels of the frontier orbitals, which
are lowered in 3-CF3 by 0.2-0.3 eV compared to 3, and actually
closer to those of the (P,N) complex A (Figure 4). From these data,
it can be concluded that it is indeed the electrophilicity of the
carbene complex that governs the chemoselectivity between O–
H and C–H insertion. Overall, if the (P,P) ligand stabilizes the gold
carbene complex 3 and tempers its electrophilicity by enhancing
Aucarbene backdonation, it displays the typical reactivity of
transient gold carbene complexes and the reaction with
unprotected phenols can be driven to O–H or C–H insertion by
changing the aryl substituent at the carbene center.
Figure 4. Schematic representation of the HOMO-LUMO energy levels of the
-oxo gold carbene complexes 3, 3-CF3 and A.
In conclusion, an -oxo gold carbene complex has been
experimentally authenticated for the first time. As shown by the X-
ray diffraction analysis and DFT calculations, the o-carboranyl
Scheme 2. Typical gold carbene reactivity upon reaction of diazo compound 1
with styrene, triphenylphosphine-borane and phenol catalyzed by the (P,P)
complex 2.
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10.1002/anie.201711647
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[9] According to advanced mass spectrometric studies, -oxo gold carbenes
are not generated with pyridine N-oxide. Only pyridine adducts have been
characterized in this case: a) J. Schulz, L. Jašíková, A. Škríba, J. Roithová
J. Am. Chem. Soc. 2014, 136, 11513-11523; b) J. Schulz, J. Jašík, A. Gray,
J. Roithová Chem. Eur. J. 2016, 22, 9827-9834.
[10] -Oxo copper carbene complexes have been authenticated early on, see:
B. F. Straub, P. Hofmann Angew. Chem. 2001, 113, 1328-1330; Angew.
Chem. Int. Ed. 2001, 40, 1288-1290
[11] a) A. S. K. Hashmi, Angew. Chem. 2008, 120, 6856-6858; Angew. Chem.
Int. Ed. 2008, 47, 6754-6756; b) A. Fürstner, L. Morency, Angew. Chem.
2008, 120, 5108-5111; Angew. Chem. Int. Ed. 2008, 47, 5030-5033; c) D.
Benitez, N. D. Shapiro, E. Tkatchouk, Y. Wang, W. A. Goddard, F. D. Toste,
Nat. Chem. 2009, 1, 482-486; d) G. Seidel, R. Mynott, A. Fürstner, Angew.
Chem. 2009, 121, 2548-2551; Angew. Chem. Int. Ed. 2009, 48, 2510-2513;
e) G. Seidel, A. Fürstner, Angew. Chem. 2014, 126, 4907-4911; Angew.
Chem. Int. Ed. 2014, 53, 4807-4811; f) R. J. Harris, R. A. Widenhoefer,
Angew. Chem. 2014, 126, 9523-9525; Angew. Chem. Int. Ed. 2014, 53,
9369-9371; g) M. W. Hussong, F. Rominger, P. Krämer, B. F. Straub,
Angew. Chem. 2014, 126, 9526-9529; Angew. Chem. Int. Ed. 2014, 53,
9372-9375; h) Y. Wang, M. E. Muratore, A. M. Echavarren, Chem. Eur. J.
2015, 21, 7332-7339; i) R. J. Harris, R. A. Widenhoefer, Chem. Soc. Rev.
2016, 45, 4533-4551.
diphosphine ligand plays a key role in the stabilization of the
electrophilic carbenoid species. It chelates the gold center and
thereby enhances AuCcarbene -backdonation. The resulting
tricoordinate species participates in several catalytic carbene
transfer reactions (cyclopropanation, insertions). Most noticeable
is the functionalization of phenol. It underscores the critical impact
of the carbene electrophilicity on chemoselectivity (O–H vs C–H
insertion). These results substantiate further the influence and
interest of ligand design and secondary interactions in gold
chemistry. As shown here, bidentate ligands can dramatically
affect the stability and reactivity of cationic gold(I) complexes.[8,13]
Ligands featuring secondary groups (Lewis acids, Lewis bases)
in proximal or remote position[24] are also attracting growing
interest to enhance the reactivity and selectivity of gold complexes.
[12] For a unique nucleophilic gold(III) carbene complex, see: A. Pujol, M.
Lafage, F. Rekhroukh, N. Saffon-Merceron, A. Amgoune, D. Bourissou, N.
Nebra, M. Boutignon, N. Mézailles, Angew. Chem. 2017, 129, 12432-
12435; Angew. Chem. Int. Ed. 2017, 56, 12264-12267.
[13] a) M. Joost, A. Zeineddine, L. Estévez, S. Mallet-Ladeira, K. Miqueu, A.
Amgoune, D. Bourissou, J. Am. Chem. Soc. 2014, 136, 14654-14657; b)
M. Joost, L. Estévez, K. Miqueu, A. Amgoune, D. Bourissou, Angew. Chem.
2015, 127, 5325-5329; Angew. Chem. Int. Ed. 2015, 54, 5236-5240; c)
Zeineddine, A.; Estévez, L.; Mallet–Ladeira, S.; Miqueu, K.; Amgoune, A.;
Bourissou, D. Nat. Commun. 2017, 8, 565.
Acknowledgements
Financial support from the CNRS and the Université de Toulouse
is acknowledged. We thank Umicore AG & Co for a generous gift
of gold precursors. UPPA, MCIA (Mésocentre de Calcul Intensif
Aquitain) and CINES under allocation 2017 (A002080045) made
by Grand Equipement National de Calcul Intensif (GENCI) are
acknowledged for computational facilities. E. Daiann Sosa
Carrizo thanks CDAPP for funding part of his post-doctoral
contract.
[14] M. Joost, L. Estevez, S. Mallet-Ladeira, K. Miqueu, A. Amgoune, D.
Bourissou, Angew. Chem. 2014, 126, 14740-14744; Angew. Chem. Int. Ed.
2014, 53, 14512-14516.
[15] See supporting information for details.
[16] For a pioneering contribution on CDA analyses of carbene complexes, see:
S. F. Vyboishchikov, G. Frenking, Chem. Eur. J. 1998, 4, 1428-1438.
[17] S. S. Batsanov, Inorg. Mat. 2001, 37, 871-885.
[18] B. Cordero, V. Gomez, A. E. Platero-Prats, M. Reves, J. Echeverria, E.
Cremades, F. Barragan, S. Alvarez, Dalton Trans. 2008, 2832-2838.
[19] For a recent example of B–H insertion reactions with -diazo esters
catalyzed by Cu, see: Q. Q. Cheng, S. F. Zhu, Y. Z. Zhang, X. L. Xie, Q. L.
Zhou, J. Am. Chem. Soc. 2013, 135, 14094-14097.
Keywords: carbene complex • bidentate ligand • gold• diazo
compounds • catalysis
[1] For reviews, see: a) D. Qian, J. Zhang, Chem. Soc. Rev. 2015, 44, 677-
698; b) L. Liu, J. Zhang, Chem. Soc. Rev. 2016, 45, 506-516; c) M. R.
Fructos, M. M. Diaz-Requejo, P. J. Pérez, Chem. Commun. 2016, 52,
7326-7335.
[2] a) M. R. Fructos, T. R. Belderrain, P. de Frémont, N. M. Scott, S. P. Nolan,
M. M. Diaz-Requejo, P. J. Pérez, Angew. Chem. 2005, 117, 5418-5422;
Angew. Chem. Int. Ed. 2005, 44, 5284-5288; b) P. de Fremont, E. D.
Stevens, M. R. Fructos, M. Mar Diaz-Requejo, P. J. Perez, S. P. Nolan,
Chem. Commun. 2006, 2045-2047.
[3] a) M. R. Fructos, P. de Frémont, S. P. Nolan, M. M. Diaz-Requejo, P. J.
Pérez, Organometallics 2006, 25, 2237-2241; b) M. R. Fructos, M. M. Diaz-
Requejo, P. J. Perez, Chem. Commun. 2009, 5153-5155; c) I. Rivilla, B. P.
Gomez-Emeterio, M. R. Fructos, M. M. Diaz-Requejo, P. J. Pérez,
Organometallics 2011, 30, 2855-2860; d) J. Barluenga, G. Lonzi, M. Tomas
and L. A. Lopez, Chem. Eur. J. 2013, 19, 1573-1576; e) E. Lopez, G. Lonzi,
L. A. Lopez, Organometallics 2014, 33, 5924-5927; f) Z. Yu, B. Ma, M. Chen,
H. H. Wu, L. Liu, J. Zhang, J. Am. Chem. Soc. 2014, 136, 6904-6907; g) Y.
Xi, Y. Su, Z. Yu, B. Dong, E. J. McClain, Y. Lan, X. Shi, Angew. Chem.
2014, 126, 9975-9979; Angew. Chem. Int. Ed. 2014, 53, 9817-9821.
[4] a) J. F. Briones, H. M. L. Davies, J. Am. Chem. Soc. 2012, 134, 11916-
11919; b) Z. Y. Cao, X. Wang, C. Tan, X. L. Zhao, J. Zhou, K. Ding, J. Am.
Chem. Soc. 2013, 135, 8197-8200.
[20] For selected reviews, see: a) S.-F. Zhu, Q.-L. Zhou, Acc. Chem. Res. 2012,
45, 1365-1377; b) D. Gillingham, N. Fei, Chem. Soc. Rev. 2013, 42, 4918-
4931.
[21] For
a recent computational study on the origins of O–H vs C–H
chemoselectivity in the insertion of -oxo gold carbene complexes into
phenol, see: Y. Liu, Z. Yu, J. Z. Zhang, L. Liu, F. Xia, J. Zhang, Chem. Sci.
2016, 7, 1988-1995.
[22] During the preparation of this manuscript, L. Liu, J. Zhang et al reported a
similar strategy, using ortho-Cl and Br phenyl diazoacetates to achieve the
selective C–H functionalization of arenes with (Ph3P)AuOTf: B. Ma, J. Wu,
L. Liu, J. Zhang, Chem. Commun. 2017, 53, 10164-10167.
[23] Another way to enhance the electrophilicity is to introduce an electron-
withdrawing group on the ester substituent, as reported recently: B. Ma, Z.
Chu, B. Huang, Z. Liu, L. Liu, J. Zhang, Angew. Chem. 2017, 129, 2793-
2797; Angew. Chem. Int. Ed. 2017, 56, 2749-2753.
[24] For a few selected recent examples, see: a) Z. Wang, Y. Wang, L. Zhang,
J. Am. Chem. Soc. 2014, 136, 8887-8890; b) Y. Wang, Z. Wang, Y. Li, G.
Wu, Z. Cao, L. Zhang, Nat. Commun. 2014, 5, 4470; c) M. Devillard, E.
Nicolas, C. Appelt, J. Backs, S. Mallet-Ladeira, G. Bouhadir, J. C. Slootweg,
W. Uhl, D. Bourissou, Chem. Commun. 2014, 50, 14805-14808; d) H. Yang,
̈
F. P. Gabbaı, J. Am. Chem. Soc. 2015, 137, 13425-13432.
[5] a) V. V. Pagar, A. M. Jadhav, R. S. Liu, J. Am. Chem. Soc. 2011, 133,
20728-20731; b) J. F. Briones, H. M. L. Davies, J. Am. Chem. Soc. 2013,
135, 13314-13317; c) G. Lonzi, L. A. Lopez, Adv. Synth. Catal. 2013, 355,
1948-1954; d) V. V. Pagar, R. S. Liu, Angew. Chem. 2015, 127, 5005-5008;
Angew. Chem. Int. Ed. 2015, 54, 4923-4926.
[6] a) D. Zhang, G. Xu, D. Ding, C. Zhu, J. Li, J. Sun, Angew. Chem. 2014,
126, 11250-11254; Angew. Chem. Int. Ed. 2014, 53, 11070-11074; b) G.
Xu, C. Zhu, W. Gu, J. Li, J. Sun, Angew. Chem. 2015, 127, 897-901; Angew.
Chem. Int. Ed. 2015, 54, 883-887.
[7] Z. Zheng, Z. Wang, Y. Wang, L. Zhang, Chem. Soc. Rev. 2016, 45, 4448-
4458.
[8] a) Y. Luo, K. Ji, Y. Li, L. Zhang, J. Am. Chem. Soc. 2012, 134, 17412-
17415; b) K. Ji, Y. Zhao, L. Zhang, Angew. Chem. 2013, 125, 6636-6640;
Angew. Chem. Int. Ed. 2013, 52, 6508-6512; c) K. Ji, L. Zhang, Org. Chem.
Front. 2014, 1, 34-38; d) K. Ji, Z. Zheng, Z. Wang, L. Zhang, Angew. Chem.
2015, 127, 1261-1265; Angew. Chem. Int. Ed. 2015, 54, 1245-1249; e) Y.
Wang, Z. Zheng, L. Zhang, J. Am. Chem. Soc. 2015, 137, 5316-5319.
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10.1002/anie.201711647
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
For the first time, an -oxo gold
carbene has been experimentally
authenticated, providing useful
insight into the factors influencing the
structure, stability and reactivity of
the transient species.
Abdallah Zeineddine, Feriel Rekhroukh,
E. Daiann Sosa Carrizo, Sonia Mallet-
Ladeira, Karinne Miqueu,
Abderrahmane Amgoune, Didier
Bourissou*
P
P
Au
C
Page No. – Page No.
Isolation of a Reactive Tricoordinate
-Oxo Gold Carbene Complex
chelating (P,P) ligand
tricoordinate Au center
enhanced AuCcarbene backdonation
This article is protected by copyright. All rights reserved.