Synthesis, characterization, and reactivity of cationic gold(I) α-diimine complexes

Article abstract of DOI:10.1021/om2000426

A series of cationic gold(I) α-diimine complexes of the type [(NHC)Au(α-diimine)]X or [(PPh₃)Au(α-diimine)]X, where NHC = IPr, α-diimine = BIAN-dipp, X = PF₆ (1); X = BF ₄ (2); X = SbF₆ (3); NHC = I^tBu, α-diimine = BIAN-dipp, X = PF₆ (4); X = BF₄ (5); NHC = IMes, α-diimine = BIAN-dipp, X = PF₆ (6); PPh₃, α-diimine = BIAN-dipp, X = PF₆ (7); NHC = IPr, α-diimine = DAB-Mes, X = PF₆ (8, 10) bearing an N-heterocyclic carbene (NHC) or a phosphine ligand, have been synthesized and characterized by NMR spectroscopy and single crystal X-ray diffraction. The stability of the new complexes and their catalytic activity for the intermolecular addition of the indole nucleophilic carbon to 1,6-enyne were also investigated.

Full text of DOI:10.1021/om2000426

ARTICLE
pubs.acs.org/Organometallics
Synthesis, Characterization, and Reactivity of Cationic Gold(I)
r-Diimine Complexes
,†
‡
†,§
§
,†
Pierre de Fr ꢀe mont,* Herv ꢀe Clavier, Vitor Rosa, Teresa Avil ꢀe s, and Pierre Braunstein*
†
Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Universit ꢀe de Strasbourg, 4 rue Blaise Pascal,
CS 90032, 67081 Strasbourg, France
‡
Institut des Sciences Mol ꢀe culaires de Marseille (UMR 6263), Universit ꢀe Aix-Marseille III, Case A 62, Av. Escadrille Normandie Niemen,
1
3397 Marseille Cedex 20, France
§
REQUIMTE, Departamento de Quimica, Faculdade de Ci ^e ncias e Tecnologia, Universidade Nova de Lisboa, Caparica,
2
829-516, Portugal
S Supporting Information
b
ABSTRACT: A series of cationic gold(I) R-diimine complexes
of the type [(NHC)Au(R-diimine)]X or [(PPh )Au(R-
3
diimine)]X, where NHC = IPr, R-diimine = BIAN-dipp, X =
t
PF (1); X = BF (2); X = SbF (3); NHC = I Bu, R-diimine =
6
4
6
BIAN-dipp, X = PF (4); X = BF (5); NHC = IMes, R-diimine
6
4
=
BIAN-dipp, X = PF (6); PPh , R-diimine = BIAN-dipp, X =
6
3
PF (7); NHC = IPr, R-diimine = DAB-Mes, X = PF (8, 10)
6
6
bearing an N-heterocyclic carbene (NHC) or a phosphine
ligand, have been synthesized and characterized by NMR
spectroscopy and single crystal X-ray diffraction. The stability
of the new complexes and their catalytic activity for the
intermolecular addition of the indole nucleophilic carbon to
1
,6-enyne were also investigated.
’
INTRODUCTION
Gold(I), having the electronic configuration [Xe]4f 5d and
cis-conformation of the R-diimine moiety, and the free DABs are
mainly found in trans-conformation to minimize the steric repul-
sion from the N-alkyl/aryl substituents borne by both nitrogen
atoms. Independently from their free conformation, both of these
R-diimines normally act as bidentate ligands to form complexes
with high activity in homogeneous catalysis for reactions such as
Suzuki or Negishi coupling, epoxidation of propylene, and polym-
14
10
being in the third transition series of the periodic table, is usually
considered as a soft Lewis acid, binding to soft bases in the1
following preferential order: Si ≈ C ≈ P > S > Cl > N > O > F.
Cationic gold(I) species tend to disproportionate to Au(0) and
Au(III) in the absence of proper stabilization by a powerful
5
erization of alkenes. In order to take advantage of their electronic
σ-donor ligand. Usually anionic nitrogen ligands such as amides
ꢀ
versatility and their steric tunability, we decided to use R-diimines
(
including NTf2 ), bidentate amidinates, guanidinates, β-dike-
2
þ
timinates, and pyrazolates are suitable for this purpose. By
contrast, the weakness of the dative bond between gold and a
neutral nitrogen-donor renders the synthesis of cationic gold(I)
complexes with such ligands more challenging. Recently, the use
of NHC ligands has allowed the isolation of stable cationic
complexes bearing formally neutral nitrogen donors, for example
as neutral stabilizing ligands of the Au center. The use of gold(I)
salts in homogeneous catalysis has bewilderingly gained attention
6
over the last 10 years and is growing very quickly. The acidic
character and low oxophilicity render the gold(I) cation an
attractive candidate for the activation of carbonꢀcarbon multiple
bonds in functionalized organic molecules, even under air. For
instance, it is now a well established catalyst for the hydration or
hydroamination of alkynes, the enyne cycloisomerization, the
Markovnikov hydroamination or hydroalkoxylation of allenes, the
3
nitrile or pyridine ligands (Scheme 1).
The versatility of R-diimines, such as bis-aryl/alkyl-diazabuta-
dienes (DAB)s and bis-aryl/alkyl-acenaphthenequinonediimines
4
(BIAN)s, which are weak σ-donors, strong π-acceptors, and can
[
2 þ 2] or [4 þ 2] cycloaddition of alkynes with alkenes, and the
7
be electronically active and behave as noninnocent ligands, has
resulted in their use as ligands with metals and metalloids from
groups 12ꢀ16, alkaline earths, lanthanides, and transition metals
such as Ti(IV), Mo(VI), Ir(III), Re(I), Ru(II), Ni(II), Pd(II),
Pt(II), Cu(I), and Ag(I), including zerovalent metal atoms
rearrangement of allylic acetates. Herein, we also investigate a new
series of cationic gold(I) complexes containing an R-diimine ligand
as catalyst in the cycloisomerization of enynes.
4,5
Received: January 17, 2011
Published: March 31, 2011
5
from groups 8ꢀ10. In solution, the free BIANs exhibit a blocked
r 2011 American Chemical Society
2241
dx.doi.org/10.1021/om2000426
|Organometallics 2011, 30, 2241–2251

Organometallics
ARTICLE
Scheme 1. Structures of Selected Cationic NHCꢀAu(I) Complexes with Neutral Nitrogen-Donor Ligands
Scheme 2. Synthesis of the Cationic [(NHC)Au(BIAN-dipp)]X Complexes 1ꢀ6
’
RESULTS AND DISCUSSION
not quantitative, and both residual free BIAN-dipp and most likely
the cationic [(IPr)Au(MeCN)]PF could be detected (10%
6
To evaluate the stability of the R-diimine gold(I) complexes, IPr
0
approx) after 24 h while the newly formed complex did not show
any sign of decomposition. As the ratio of all added reagents was
precisely 1:1:1, it was plausible that a competition between
acetonitrile and BIAN-dipp to bind to the gold(I) cation was
taking place. An analogous reaction in deuterated THF surprisingly
gave similar results. Finally, when the reaction was carried out in
(
N,N -bis(2,6-diisopropylphenyl)imidazol-2-ylidene) was initially
chosen as a strong σ-donor to stabilize electronically and sterically
the gold(I) center and suppress its oxidizing character. BIAN-
dipp (bis(2,6-diisopropylphenyl)acenaphthenequinonediimine)
was also selected as a sterically hindered diimine with a fixed cis-
8
conformation. Upon addition of AgPF , a yellow solution of
6
9
CDCl , a quasi-non-coordinating solvent, quantitative conversion
(
IPr)AuCl and BIAN-dipp, in deuterated acetonitrile, turned dark
red with the concomitant formation of AgCl. The H NMR
spectrum of the crude reaction mixture evidenced the formation
3
1
to 1 was observed. After filtration through a plug of silica gel, 1
could be precipitated from pentane as a dark red powder which
13
turned brown after drying. The C NMR spectrum of 1 exhibits a
of the new complex [(IPr)Au(BIAN-dipp)]PF (1) with shifts for
6
signal at 164.8 ppm, typical for a carbene carbon on the cationic
some protons groups. For instance, the ortho- and para-protons of
the naphthalene rings of BIAN-dipp substituents, which are very
sensitive to the coordination mode adopted by the ligand, were
shifted downfield by 0.5 ppm whereas the septet arising from the
diisopropyl groups, from both BIAN and IPr substituents, were
shifted upfield by 0.15 ppm. Nevertheless, the conversion of 1 was
3
goldꢀnitrogen moiety while the signal from the imine carbons
13
shifts from 161.0 ppm to 165.0 ppm. Full assignment of the
C
NMR spectrum was accomplished by a DEPT 135 experiment. A
13
closer look at the C spectrum also revealed a partial activation of
CDCl
likely due to the presence of the silver(I) salt as evidenced
3
2
242
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Organometallics
ARTICLE
Scheme 3. BIAN Complexes with Silver(I) and Thallium(I)
13
31
Table 1. C and P NMR Chemical Shifts of Selected NHC and PPh Gold(I) Complexes
3
complexes
δ
C
(ppm)
reported complexes
δ
C
(ppm)
C
Δ δ (ppm)
a
[
[
[
[
[
[
[
(IPr)Au(BIAN)]PF
6
(1)
(2)
164.8
163.1
166.4
167.6
160.3
160.7
163.7
(IPr)AuCl
175.1
166.1
167.1
168.2
159.7
173.4
165.3
ꢀ10.3 vs (1)
ꢀ1.3 vs (1)
ꢀ2.3 vs (1)
ꢀ7.9 vs (4)
þ0.6 vs (4)
ꢀ9.7 vs (6)
ꢀ1.6 vs (6)
a
(IPr)Au(BIAN)]BF
(IPr)Au(BIAN)]SbF
(IPr)Au(DABMes)](PF
4
(IPr)Au(MeCN)PF
6
a
6
6
(3)
) (8)
(IPr)Au(Py)PF
a
6
(ItBu)AuCl
a
(ItBu)Au(BIAN)]PF
6
(4)
(5)
(6)
(ItBu)Au(MeCN)PF
6
a
(ItBu)Au(BIAN)]BF
4
(IMes)AuCl
a
(IMes)Au(BIAN)]PF
6
(IMes)Au(MeCN)PF
6
complex
δ
P
(ppm)
reported complexes
δ
P
(ppm)
P
Δ δ (ppm)
[
(PPh
3
)Au(BIAN)]PF
6
(7)
32.3
(PPh
3
)AuCl
28.7
48.1
þ3.6 vs (7)
ꢀ15.8 vs (7)
[
(PPh
3
2
) Au]PF
6
a
From the literature.
by the appearance of two new triplets (1:1:1) at 105.6 and 101.7
seemed to interact with silver(I), and a second (1:1:1) triplet
1
13
ppm, showing a coupling constant ( J( CꢀD) = 33 Hz) equal to
accounting for CDHCl was found at 5.29 ppm. Even though
2
3
1
that found for CDCl at 77.0 ppm. The P NMR spectrum of 1
attempts were not made to isolate the complex detected by
NMR, two plausible species could be assumed to be formed in
solution: [(BIAN-dipp) Ag]PF and/or [(BIAN-dipp)Ag-
3
ꢀ
1
31
19
showedthecharacteristicPF6 septetatꢀ141.3ppm( J( Pꢀ F)
712 Hz). The silver(I) cation is known to catalyze the hydrolysis
of PF6 to PO4 via a PO F intermediate, and after one day in
=
2
6
ꢀ
3-
ꢀ
2 2
(DCM) ]PF . Consequently, the formation of the cationic
X 6
31
nondry CDCl , the P NMR spectrum of 1 exhibited the
gold(I) complexes, via dehalogenation, may have occurred
through a competition between gold(I) and silver(I) to coordi-
3
ꢀ
2
1
31
19
characteristic broad triplet of PO F at ꢀ15.5 ppm ( J( Pꢀ F)
2
1
0
=
972 Hz). To keep the synthesis straightforward under air
nate the BIAN-dipp. In contrast, the addition of TlPF to BIAN-
6
conditions, CDCl was replaced by CD Cl and AgPF by TlPF ,
dipp in CD Cl did not result in any change of color of the
2 2
3
2
2
6
6
which allowed the formation of 1 without any side reaction
solution, even after an excess (2.2 equiv) of thallium salt was
added. In this case, the H NMR spectrum revealed no noticeable
1
(Scheme 2).
Recently, Avil ꢀe s et al. reported the coordination of
shift (0.04 ppm) of the resonances for the ortho- and para-
protons of the naphthalene backbone, implying that the thallium-
(I) center had very limited interactions with the BIAN-dipp
ligand prior to halide abstraction. By following the optimized
conditions for the synthesis of 1, the analogues [(IPr)Au(BIAN-
[
Ag(MeCN) ]BF with BIAN-dipp to form [(BIAN-dipp) Ag]BF ,
4 4 2 4
and Cowley et al. reported the coordination of TlPF to BIAN-Mes
6
(
bis(2,4,6-trimethylphenyl)acenaphthenequinonediimine) with for-
11
mation of (BIAN-Mes)TlPF6. Both silver and thallium adducts
were fully characterized by NMR spectroscopy and X-ray diffraction
dipp)]BF
prepared starting from (IPr)AuCl, BIAN-dipp, and AgBF
4
4
(2) and [(IPr)Au(BIAN-dipp)]SbF
6
(3) were also
or
AgSbF . Both complexes exhibited H and C NMR spectra
6
(
Scheme 3).
1
13
In order to gain insight into the species responsible for the
13
halide abstraction from the precursor gold complex, the reactions
which were very similar to those of 1. In the C NMR spectra,
the carbene carbons of 2 and 3 were, respectively, observed at
163.1 and 166.4 ppm (Table 1). In order to tune the steric
environment around the gold(I) cation, the new complexes
1
of BIAN-dipp with AgPF or TlCl were investigated by H NMR
6
spectroscopy. Addition of AgPF to BIAN-dipp in CD Cl led to
6
2
2
a color change from yellow to bright orange accounting for a
1
t
t
probable coordination of Ag(I), which was confirmed by H
[(I Bu)Au(BIAN-dipp)]PF
6
(4), [(I Bu)Au(BIAN-dipp)]BF
(6) were synthesized,
4
NMR spectroscopy. The doublets of the ortho- and para-protons
of the acenaphthene skeleton became multiplets and shifted
downfield by 0.15 ppm. Interestingly, the dichloromethane
(5), and [(IMes)Au(BIAN-dipp)]PF
starting from the known reagents (I Bu)AuCl (I Bu = N,N -
bis(tert-butyl)imidazol-2-ylidene) and (IMes)AuCl (IMes = N,
6
t
12
t
0
9
2
243
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Organometallics
ARTICLE
Scheme 4. Synthesis of [(PPh )Au(BIAN-dipp)]PF (7)
[(PPh ) Au]PF gave, respectively, a broad multiplet centered at
3
6
3 2
6
7
.60 ppm and a peak at 48.0 ppm, matching the signals from the
second impurity found during the synthesis of 7. The formation of
(PPh ) Au]PF was also confirmed by ESI-mass spectroscopy
[
3
2
6
with an intense peak found at m/z = 721.156 accounting for
þ
[
Au(PPh ) ] . This could also explain the release of BIAN-dipp
3
2
during the reaction. In 2005, Gagosz et al. upon attempting to
prepare the cationic complex [(PPh )Au]PF in DCM observed
3
6
only a rearrangement to [(PPh ) Au]PF and could not isolate the
3
2
6
16
desired complex. After a prolonged time in CD Cl , 7 also
2
2
appeared to very slowly rearrange to [(PPh ) Au]PF . After
3
2
6
crystallization from a mixture of octane/DCM, 7 could be recov-
ered pure and cocrystallized with two molecules of DCM
(Scheme 4).
0
N -bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), using the
same reaction conditions as described above for the formation
of 1 and 2. The H NMR spectra of the new complexes exhibited
1
Attempts to extend the above method to less bulky DAB-Mes
the signals for each NHC moiety and the ortho- and para-protons
borne by the naphthalene backbone (from BIAN-dipp) were
slightly shifted downfield. The C NMR spectra exhibited the
were made. Addition of TlPF to a solution of (IPrAu)Cl and
6
DAB-Mes in CD Cl resulted in a color change from yellow to
2
2
13
bright orange and formation of a white precipitate of TlCl. The
1
characteristic signal for a carbene carbon bound to cationic
H NMR spectrum of the crude reaction mixture evidenced the
gold(I) with values falling in the range between 160.3 and
formation of two new complexes, with two sets of signals related
to a coordinated DAB-Mes ligand. After precipitation by addition
of pentane, a bright orange powder was obtained. The H NMR
3
1
63.7 ppm (Table 1). After 24 h in solution, no sign of
1
decomposition was obvious.
The development and isolation of cationic gold(I) complexes
stabilized by bulky phosphines has undergone a very fast growth
during the last 5 years. Echavarren et al. have developed a series of
cationic gold(I) biphenylphosphines which are very active catalysts
spectrum of the solid displayed only one set of signals, with
integration consistent for the new complex [(IPr)Au(DAB-
1
3
31 19
Mes)](PF ) (8). It was further characterized by C, P,
F
6
13
NMR and by elemental analysis. The C NMR spectrum
13
for the cycloisomerization of enynes. In addition, various elegant
cationic π-gold(I) phosphine complexes with alkynes, alkenes, and
allenes have been recently isolated and characterized by single
showed a signal at 167.6 ppm characteristic for a carbene bound
3
to an NꢀAu moiety. The ESI-mass spectroscopy could not
provide any signal clearly related to 8. It is important to note that
the formation of the side product was extremely difficult to avoid,
even by changing the stoichiometry of DAB-Mes and/or TlPF6.
In order to test the viability of the (BIAN-dipp)AuCl complex
in the absence of a strong σ-donor stabilizing ligand, the reaction
of BIAN-dipp with (CH ) SAuCl in CD Cl was monitored first.
14
crystal X-ray diffraction. In order to extend the use of the BIAN-
dipp ligand to another class of cationic gold(I) complexes, a
synthesis was carried out using PPh , instead of IPr, as stabilizing
3
σ-donor ligand. The reaction of (PPh )AuCl with BIAN-dipp in
3
the presence of TlPF in CD Cl yielded a dark red solution and a
6
2
2
3 2
2
2
1
white precipitate of TlCl. The H NMR spectrum of the crude
After 12 h, the reaction mixture was dark orange and a gold
1
reaction mixture confirmed the formation of the new complex
mirror formed. The H NMR spectrum of the crude reaction
[
(PPh )Au(BIAN-dipp)]PF (7). The ortho- and para-protons of
mixture showed mainly some unreacted BIAN-dipp with
(CH ) SAuCl and (CH ) S. A new set of signals with low
intensity (10% vs free BIAN-dipp) was also observed, and it
could be assigned to the formation of (BIAN-dipp)AuCl (9).
However, attempts to crystallize it, by slow diffusion of a layer of
octane, led to some yellow and white crystals which were
3
6
the naphthalene backbone (from the BIAN) were slightly shifted
upfield and appeared as two doublets at 8.18 and 6.78 ppm,
respectively. Two other sets of weak signals were also observed:
the first, obviously related to BIAN-dipp, comprised three doublets
at 7.96, 6.99, 6.69 ppm, and a septet at 2.98 ppm, and the second,
3
2
3 2
31
related to PPh , a multiplet at 7.68 ppm. The P NMR spectrum
identified as BIAN-dipp (yellow) and (IPrNH )Cl (white) by
3
3
displayed a major peak at 32.3 ppm assignable to the coordinated
comparison with crystallographic data from the literature (2,
6-diisopropylphenylamonium chloride). As the hydrolysis of
ꢀ
17
PPh in 7, a smaller peak at 48.1 ppm and the signal of PF6 at
3
ꢀ
141.3 ppm (Table 1). After filtration through Celite and
precipitation from pentane, complex 7 was obtained as a red
diimines is known to be catalyzed by a strong Brønsted or Lewis
acid, the generation of (IPrNH )Cl with concomitant formation
3
powder with a small PPh -containing impurity. The supernatant
of acenaphthene-1,2-dione may be facilitated by the Lewis acidity
of the gold(I) center. When the reaction was carried out under
anhydrous conditions, after 12 h the crude solution retained its
original yellow color and no trace of gold(0) was observed. The
starting materials could be recovered by crystallization. This lack
of reactivity under such conditions is intriguing and points to the
following: (i) the BIAN-dipp ligand was not able to displace the
3
pentane solution was yellow, which suggested the presence of
noncoordinated BIAN-dipp. After evaporation of the pentane, the
1
remaining solids were analyzed by NMR spectroscopy. The H
NMR spectrum showed only the signal for the free BIAN-dipp, and
surprisingly the doublet at 6.99 ppm was no longer observed. In
31
19
addition, the P and F NMR spectra did not show any signal,
which ruled out the possibility of formation of (BIAN-dipp)TlPF6
(CH ) S and had low affinity for gold(I); (ii) the hydrolysis of
3 2
or (BIAN-dipp)Au(X)PF . Note that working under anhydrous
conditions, or changing the stoichiometry of the synthesis, by
the BIAN-dipp might have occurred through a displacement of
(CH ) S by H O followed by coordination and attack of the
6
3
2
2
adding an excess of BIAN-dipp and/or TlPF could not prevent the
diimine. In a last attempt to generate (BIAN-dipp)AuCl, the
reaction of AuCl and BIAN-dipp in dry CD Cl was monitored
by NMR spectroscopy. Upon addition of an excess of AuCl, the
reaction mixture turned dark red with precipitation of gold(0).
The spectrum of the crude reaction mixture revealed a shift of the
6
formation of both impurities described above. In order to account
for these facts, we prepared [(PPh ) Au]PF by reacting 2 equiv of
2
2
3
2
6
PPh with 1 equiv of (CH ) SAuCl (dimethyl sulfide gold(I)
3
3 2
1
5
1
31
chloride) and 1 equiv of TlPF . The H and P NMR spectra of
6
2
244
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Organometallics
ARTICLE
Figure 2. Ball and stick representation of [(IMes)Au(BIAN-dipp)]PF
6
(
6) (bottom) and [(Ph P)Au(BIAN-dipp)]PF (7) (top). Hydrogen
3
6
Figure 1. Ball and stick representation of [(IPr)Au(BIAN-dipp)]SbF
6
atoms and DCM molecules have been omitted for clarity.
t
(
3) (bottom) and [(I Bu)Au(BIAN-dipp)]BF (5) (top). Hydrogen
4
atoms and DCM molecules have been omitted for clarity.
þ
and a peak at m/z = 1255.547 [((BIAN-dipp) AuClNa ) ꢀ H]
2
para-protons of the naphthalene backbone from 7.89 to 8.10
ppm. The other signals were split, and their separate integrations
were not consistent with two species in solution. The four
protons giving a sextuplet at 2.96 ppm for the free BIAN-dipp
gave rise to a well-defined septet at 2.95 ppm, and an undefined
sextuplet at 3.11 ppm accounting, respectively, for three and one
protons. The eight methyl groups were also split into three
doublets, at 1.37, 1.24, and 1.03 ppm accounting for 3, 3 þ 6, and
were observed. Unfortunately, we did not succeed to obtain
crystals of sufficient quality for a study by X-ray diffraction, and
there is a lingering doubt about the possible formation of clusters
þ
ꢀ
2
or [(BIAN-dipp) Au ]AuCl rather than 9.
2
To unambiguously characterize the new gold(I) diimine com-
plexes, X-ray quality crystals were grown from a mixture of DCM/
octane for 3, 5, 6, 7, and 8. Ball-and-stick representations are
provided in Figures 1 and 2, and crystallographic data are given in
Table 2. The complexes 3, 5, 6, and 7 contain a two-coordinated
gold atom, in the expected almost linear coordination environment.
In solution, the coordinated and free imine nitrogen atoms are
likely to exchange their role rapidly on the NMR time scale, but in the
solid state the gold(I) cation retains its preferred two-coordinate
linear geometry. Observed AuꢀN distances in the range 2.09ꢀ
2.11 Å are characteristic of a neutral nitrogen donor group bound to
6
þ 6 protons. Such splitting for the isopropyl protons might be
characteristic of an agostic interaction with the acidic gold(I)
center and was not observed for the NHC and PPh complexes
3
described above. Elemental analysis confirmed the existence of
(
BIAN-dipp)AuCl (9) and thus ruled out the formation of
(BIAN-dipp)Au Cl . Under the ESI-mass conditions, 9 was
2
2
not detected and a major peak at m/z = 1023.610 ((BIAN-
þ
3
dipp Na ) ꢀ H), a peak at m/z = 1233.62 (BIAN-dipp AuCl),
gold. AuꢀN distances between 2.74ꢀ3.00 Å are in agreement with
2
2
2
245
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Organometallics
ARTICLE
Table 2. Selected Bond Distances (Å) and NꢀAuꢀC Angles (deg) in Gold Complexes
complexes
AuꢀC(1)
AuꢀN(3)
Au N(4)
C(1)ꢀAuꢀN(3)
3
3 3
[
[
[
(IPr)Au(BIAN)]SbF
6
(3)
1.983(7)
2.014(5)
1.980(3)
2.091(6)
2.094(4)
2.088(2)
3.000(7)
2.863(4)
2.851(3)
167.9(3)
(ItBu)Au(BIAN)]BF
4
(5)
175.59(19)
170.37(12)
(IMes)Au(BIAN)]PF
6
(6)
Au(1)ꢀC(1)
Au(1)ꢀN(3)
C(1)ꢀAu(1)ꢀN(3)
[
[
[
((IPr)Au)
2
(DAB-Mes)](PF
(DAB-Mes)](PF
6
)
)
2
(10)
(10)
1.958(10)
2.063(9)
ꢀ
177.6(4)
Au(2)ꢀC(48)
Au(2)ꢀN(4)
C(48)ꢀAu(1)ꢀN(4)
((IPr)Au)
2
6
2
2.007(10)
2.036(9)
ꢀ
176.6(4)
AuꢀP(1)
2.2371(15)
AuꢀN(1)
2.110(4)
Au N(2)
P(1)ꢀAuꢀN(1)
3
3 3
(PPh
3
)Au(BIAN)]PF
6
(7)
2.742(2)
169.74(13)
structure of [(IPr)Au(DAB-Mes)](PF ) (8) revealed the unex-
6
pected formation of the dinuclear complex [((IPr)Au) (DAB-
2
Mes)](PF ) (10). In this complex, the DAB-Mes adopts a trans-
6
2
þ
configuration probably mandatory to anchor two bulky (IPr)Au
fragments (Figure 3). The CꢀAu bond distances are equal to 1.96
and 2.00 Å. The NꢀAu bond distances are equal to 2.04 and
2
.07 Å. Both gold(I) cations are two-coordinate with an almost
linear coordination geometry; the NꢀAuꢀC angles are equal to
1
77.6 and 176.6° (Table 2). There are two molecules of DCM
cocrystallized, not interacting with the gold(I) centers.
Additional attempts to crystallize 8 yielded the formation of a
yellow solution containing some orange crystals having the cell
parameters of 10. These crystals were dried under vacuum and
1
then dissolved in CD Cl . Their H NMR spectrum confirmed
2
2
the clean formation of 10 with a new set of signals different from
those of 8 having an integration fitting a ratio DAB-Mes/IPr
equal to 2:1. The yellow octane solution was taken to dryness,
1
and the residue was analyzed by H NMR spectroscopy, reveal-
ing the presence of free-DAB-Mes. It is very important to note
that 10 was in fact already detected as a side product during the
formation of 8 in the crude mixture. It is not clear whether the
complete rearrangement from 8 to 10 is seen as triggered by
changing slowly the polarity of the solution from DCM to octane,
but 8 and 10 can be kinetic and thermodynamic products,
Figure 3. Ball and stick representation of [(IPr)
2
Au(DAB-Mes)]-
(
PF ) (10). Hydrogen atoms and DCM molecules have been omitted
6
2
for clarity.
þ
respectively, upon addition of DAB-Mes to the (IPr)Au
the presence of van der Waals interactions. Since the BIAN-dipp
ligand has a mirror plane of symmetry (C2v symmetry) with two
equivalent nitrogen positions, and tetragonal BIAN-dipp complexes
with copper(I) and silver(I) are known, we would have expected a
plausible structure with a tricoordinated gold atom, and two
equivalent goldꢀnitrogen bond distances. All AuꢀC distances lie
in the range of 1.98ꢀ2.01 Å and are in agreement with those
fragment.
Reactivity Studies. The new BIAN-dipp gold(I) complexes
having their synthesis rationalized, 1, 2, 3, 4, 6, and 7, were tested
to mediate the addition of a nucleophilic carbon to an 1,6-enyne.
Recently, Echavarren et al. have published a series of elegant
results, supported with detailed mechanistic studies, on the
addition of indole to N-cinnamyl-4-methyl-N-(prop-2-yn-1-
yl)benzenesulfonamide (11). They used some bulky cationic
phophine, phosphite, and NHC gold(I) complexes such as
3
reported for the cationic NHCꢀAu(I) complexes. The PꢀAu
distance is equal to 2.23 Å and is close to those reported by
13c
Echavarren et al. for cationic biphenylphosphine Au(I) complexes.
[(dtBubP)Au(MeCN)]SbF (12) (dtBubP = ditertbutylbiphe
6
The NꢀAuꢀC and NꢀAuꢀP angles are within the range between
nylphosphine), [(IPrAu)Au(Bzn)]SbF6 (13) (Bzn = benzo
1
67.9° and 176.6°. The deviation from linear coordination geometry
nitrile), [(IMesAu)Au(Tmb)]SbF6 (14) (Tmb =2,4,6-tri
t
may be due to important steric interactions brought in by the ligands,
and this effect is particularly noticeable with 3 and 7.
methoxybenzonitrile), or [(I BuAu)Au(Tmb)]SbF (15) to per-
6
13
form the catalysis. For the sake of comparison, similar reaction
conditions were used: 5 mol % of [Au(I)] and 0.25 M of (11) in
DCM, at room temperature. The reaction time was set at 17 h
because the NHC-Au(I) systems are known to catalyze the
reaction slowly. The addition of indole with the BIAN-dipp
complexes generated the formation of 3-((S)-((S)-4-methylene-
1-tosylpyrrolidin-3-yl)(phenyl)methyl)-1H-indole (16) and
There is an inclusion of disordered molecules of DCM in the
crystal lattice, but they do not interact with the gold(I) cation to
18
form a halonium adduct. Moreover, there is no trace of residual
thallium(I) even though the chemistry of gold(I)ꢀthallium(I)
19
clusters is rich. Note that a monodentate coordination mode for
the BIAN-dipp is extremely rare. The attempt to resolve the crystal
2
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Organometallics
ARTICLE
Table 3. Indole Addition to 1,6-Enynes Catalyzed by Various Au(I) Complexes
a
a
entry
catalyst
isolated yield (%)
ratio 16/17
catalyst
isolated yield (%)
ratio 16/17
d
1
2
3
4
5
6
7
TlPF
6
NR
92
93
95
65
30
ꢀ
AuCl
NR
57
ꢀ
ꢀ
d
1
2
3
4
6
7
50:50
48:52
47:53
71:29
85:14
13
25:75
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
40:60
39:61
80:20
d
b
14
62
d
15
68
d
c
39
>98:2
12
74
a
b
c
d
13
Ratio determined by NMR. Reaction time: 19 h. Reaction time 1 h. Results from Echavarren et al.
3
-(((1R,5S,6R)-6-phenyl-3-tosyl-3-azabicyclo[3.1.0]hexan-1-yl)-
release of the BIAN-dipp and therefore enhance the catalytic
activity. The selectivity for the formation of 16 over 17 is also
apparently correlated to the steric hindrance of the σ-donor ligand.
For gold, steric parameters have been ranked as follows from the
13,20
methyl)-1H-indole (17) together with different ratios.
The
reaction likely proceeded in three steps: coordination and acti-
vation by Au(I) of the alkyne function; rearrangement involving
the alkene function to a distorted anticyclopropyl gold(I)
carbene via an 5-exodig process; attack of the indole to the
carbene gold(I) or the cyclopropyl ring leading, respectively, to
21
more to the less crowed IPr > ItBu > IMes > PPh . Increasing the
3
ligand steric bulk leads to a decrease of the selectivity of the
reaction. This illustrates perfectly the difficulty to associate in
catalysis selectivity and activity.
1
6 and 17.
A first glance at Table 3 shows that all the BIAN-dipp complexes
are active, whereas TlPF is inert. The best yields are obtained with
6
’
CONCLUSIONS
1, 2, and 3 bearing an IPr moiety, and the reaction is almost
quantitative. The yields decrease by 30% when using IMes and are
We have emphasized the ability of R-diimines to form stable
adducts with the gold(I) cation. The use of BIAN-dipp allows for
t
further lowered by 25% with PPh and I Bu. Surprisingly, the trend
3
of the reaction yield versus the σ-donor ligand for 3, 4, 6, and 7 is
roughly reversed compared to the one described by for 12, 13, 14,
and 15. The (IPr)Au(BIAN) moiety gives the same amount of 16
the formation of a series of PPh and NHC cationic complexes
3
characterized by NMR and X-ray diffraction. The gold atom is
two-coordinate with an almost linear environment, and an
unusual monochelating mode for the BIAN-dipp ligand was
evidenced. The replacement of BIAN-dipp by DAB-Mes leads to
the formation of a monogold adduct which rearranges into a bis-
gold adduct during the formation of crystals in a nonpolar
solvent. All the BIAN-dipp complexes were active to catalyze
the addition of indole to 1,6-enyne. In this regard, the phosphine-
based complex is less active than anticipated. More importantly,
the BIAN-dipp ligand appears to play a role determining the
þ
and 17 (around 50:50) regardless of the noncoordinating anions
employed. The formation of 16 is favored by 25% with 4 and 6 and
is almost quantitative with the phosphine complex 7. The preferred
formation of 16 over 17 seems to be governed by the nature of the
σ-donor ligand (NHC or phosphine) and more specifically its
13,20,21
steric bulk.
Thus, the BIAN-dipp is likely to remain uncoor-
dinated during the catalytic cycle to allow substrate approach. A
more sterically demanding NHC such as IPr will facilitate the
2
247
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Organometallics
ARTICLE
3
1
1
regioselectivity of the reaction. Studies aimed at exploring the
stability/reactivity of complexes with bulkier R-diimines are
currently ongoing in our laboratory.
(CH
(CD
NMR (CD
Calcd for C63
1.17; H, 6.27; N, 4.28.
Synthesis of [(IPr)Au(BIAN)]BF
equiv, 0.32 mmol) was dissolved in 5 mL of dichloromethane with BIAN
(163 mg, 1.01 equiv, 0.33 mmol). Then AgBF was added (64 mg, 1.02
3 2 3 2 3 2
) ), 23.1 (s, CH (CH ) ), 23.0 (s, CH (CH ) ); P{ H} NMR
1
31
19
ꢀ
19
1
Cl
): δ ꢀ141.3 (septet, J( Pꢀ F) = 712.1 Hz, PF
); F{ H}
2
2
6
1
31
19
6ꢀ
2
Cl
2
): δ ꢀ74.0 (septet, J( Pꢀ F) = 712.1 Hz, PF ). Anal.
76 4 6
H N AuPF (1231.24): C, 61.52; H, 6.20; N, 4.54. Found: C,
6
’
EXPERIMENTAL SECTION
4
(2). In a flask, (IPr)AuCl (200 mg, 1
General Considerations. NMR spectra were recorded at room
1
temperature on a Bruker AVANCE 300 spectrometer ( H, 300 MHz;
4
1
3
1
1
C{ H}, 75.5 MHz), a BrukerAVANCE 400 spectrometer ( H, 400
equiv, 0.33 mmol), and the solution was stirred at room temperature for
24 h. The color of the reaction mixture color went from yellow to dark
red with the formation of a white precipitate of AgCl. The solution was
filtered through a plug of silica gel (3 g). After reduction of the volume of
DCM to 0.5 mL, 5 mL of pentane was added that led to the appearance
of a clear orange precipitate. This precipitate was filtered, washed with
13
1
19
1
31
1
MHz; C{ H}, 100.6 MHz; F{ H}, 283.0 MHz; P{ H}, 121.9
MHz), and referenced using the residual proton solvent ( H) or solvent
(
1
1
3
31
1
19
1
C) resonance, or BF and PF anions signals ( P{ H}, F{ H}).
4 6
Elemental analyses were performed by the “Service de Microanalyses”,
Universit ꢀe de Strasbourg. Electrospray mass spectra (ESI-MS) were
recorded on a microTOF (Bruker Daltonics, Bremen, Germany)
instrument using nitrogen as drying agent and nebulizing gas.
5 mL of cold pentane, and dried to afford the desired complex. Yield: 328
1
mg (87%). H NMR (CD
Cl
2
): δ 7.99 (d, J = 8.4 Hz, 2H, CH-aromatic),
2
X-ray Data Collection, Structure Solution, and Refinement for All
Compounds. Suitable crystals for the X-ray analysis of all compounds were
obtained as described above. The intensity data were collected at 173(2) K
on a Kappa CCD diffractometer 88 (graphite-monochromated MoꢀKR
radiation, λ = 0.71073 Å). Crystallographic and experimental details for the
structures are provided in the Supporting Information. The structures were
solved by direct methods (SHELXS-97) and refined by full-matrix least-
7.48 (m, 2H, CH-aromatic), 7.36 (broad m, 4H, CH-aromatic), 7.28 (m,
4H, CH-aromatic), 7.21 (m, 4H, CH-aromatic), 7.11 (s, 2H, CH-
imidazole), 6.11 (d, J = 7.5 Hz, 2H, CH-aromatic), 2.69 (septet, J =
6.9 Hz, 4H, CH(CH
(d, J = 6.9 Hz, 12H, CH (CH
3 2
0.86 (d, J = 6.9 Hz, 12H, CH (CH )
)
), 2.54 (septet, J = 6.9 Hz, 4H, CH(CH
), 0.94 (d, J = 6.9 Hz, 12H, CH (CH
), 0.68 (d, J = 6.9 Hz, 12H, CH
(CH ) ); C{ H} NMR (CD Cl ): δ 164.9 (s, NC-imine), 163.1 (s, C-
3 2 2 2
)
), 1.07
3
2
3 2
3
)
2
3 2
)
),
13
1
2
squares procedures (based on F , SHELXL-97) with anisotropic thermal
carbene), 145.4 (s, C-aromatic), 145.3 (s, C-aromatic),141.2 (s, C-aromatic),
136.5 (s, C-aromatic), 134.4 (s, C-aromatic), 131.5 (s, C-aromatic), 131.4
(s, C-aromatic), 130.8 (s, C-aromatic), 128.5 (s, C-aromatic), 128.3 (s, C-
aromatic), 127.2 (s, C-aromatic), 125.9 (s, C-aromatic), 125.7 (s, C-aromatic),
22
parameters for all the non-hydrogen atoms. The hydrogen atoms were
introduced into the geometrically calculated positions (SHELXL-97
procedures) and refined, riding on the corresponding parent atoms. The
crystal lattice contains some highly disordered DCM molecules; the
diisopropyl substituents of the BIAN-dipp or NHC ligands are slightly
disordered.
124.9 (s, C-aromatic), 124.5 (s, CH-imidazole), 28.8 (s, CH (CH
(s, CH (CH ), 24.1 (s, CH (CH ), 23.4 (s, CH (CH ), 23.1 (s, CH
(CH ), 22.9 (s, CH (CH Cl
): δ ꢀ153.7
(1173.08): C, 64.51; H, 6.54;
3 2
) ), 28.7
3
)
2
3
)
2
3 2
)
1
9
1
)
)
H
); F{ H} NMR (CD
AuBF
N, 4.83. Found: C, 64.62; H, 6.46; N, 4.53.
Synthesis of [(IPr)Au(BIAN)]SbF (3). In a flask, (IPr)AuCl (200 mg, 1
equiv, 0.32 mmol) was dissolved in 5 mL of dichloromethane with BIAN
(163 mg, 1.01 equiv, 0.33 mmol). Then AgSbF was added (121 mg, 1.1
3
2
3
2
2
2
ꢀ
General Procedure: Synthesis of the Gold Complexes. All
(s, BF
4
). Anal. Calcd for C63
76
N
4
4
reactions using (NHC)AuCl and (PPh )AuCl as starting materials were
3
carried out in air with nondried solvents, unless stated otherwise. CD
Cl
2 2
6
and CD CN were distilled from CaH , degassed, and stored over 4 Å
3
2
molecular sieves. THF(d ) was bought dry and used directly from a sealed
6
8
bottle. All other reagents were used as received from commercial suppliers.
Yields of the new complexes are based on the precursor gold complexes.
The reactions involving silver salts were made under normal light condi-
tions. However, these salts were stored away from light under argon prior
to use.
equiv, 0.35 mmol), and the solution was stirred at room temperature for
24 h. The color of the reaction mixture went from yellow to dark red with
the formation of a white precipitate of AgCl. The solution was filtered
through a plug of silica gel (2 g). After reduction of the volume of DCM
to 0.5 mL, 5 mL of pentane was added that led to the appearance of a
bright orange precipitate. This precipitate was filtered, washed with 5 mL
Synthesis of [(IPr)Au(BIAN)]PF
equiv, 0.32 mmol) was dissolved in 5 mL of dichloromethane with BIAN
163 mg, 1.01 equiv, 0.33 mmol). Then TlPF was added (124 mg, 1.1
equiv, 0.35 mmol), and the solution was stirred at room temperature for
4 h. The color of the reaction mixture went from yellow to dark red with
6
(1). In a flask, (IPr)AuCl (200 mg, 1
of cold pentane, and dried to afford the desired complex. Yield: 364 mg
1
(
6
(86%). H NMR (CD
2
Cl
2
): δ 7.99 (d, J = 7.8 Hz, 2H, CH-aromatic),
7.46 (m, 2H, CH-aromatic), 7.36 (broad m, 4H, CH-aromatic), 7.29 (m,
4H, CH-aromatic), 7.21 (m, 4H, CH-aromatic), 7.11 (s, 2H, CH-
imidazole), 6.11 (d, J = 7.5 Hz, 2H, CH-aromatic), 2.69 (septet, J =
2
the formation of a white precipitate of TlCl. The solution was filtered
through a plug of silica gel (3 g). After reduction of the volume of DCM
to 0.5 mL, 5 mL of pentane was added that led to the appearance of a
brownish precipitate. This precipitate was filtered, washed with 5 mL of
6.9 Hz, 4H, CH(CH
(d, J = 6.9 Hz, 12H, CH (CH
0.86 (d, J = 6.9 Hz, 12H, CH (CH )
3 2
3
)
2
), 2.55 (septet, J = 6.9 Hz, 4H, CH(CH
), 0.94 (d, J = 6.9 Hz, 12H, CH (CH
), 0.68 (d, J = 6.9 Hz, 12H, CH
3 2 2 2
(CH ) ); C{ H} NMR (CD Cl ): δ (ppm) = 166.4 (s, C-carbene),
3
)
2
), 1.07
3
)
2
3 2
)
),
1
3
1
cold pentane, and dried to afford the desired complex. Yield: 361 mg
1
(
91%). H NMR (CD
2
Cl
2
): δ 7.99 (d, J = 7.8 Hz, 2H, CH-aromatic),
164.8 (s, NC-imine), 145.6 (s, C-aromatic), 145.3 (s, C-aromatic), 139.4
(s, C-aromatic), 136.5 (s, C-aromatic), 134.4 (s, C-aromatic), 131.5
(s, C-aromatic), 131.4 (s, C-aromatic), 130.8 (s, C-aromatic), 128.5 (s,
C-aromatic), 128.3 (s, C-aromatic), 127.2 (s, C-aromatic), 125.9 (s, C-
aromatic), 125.7 (s, C-aromatic), 124.9 (s, C-aromatic), 124.5 (s, CH-
7
4
.48 (m, 2H, CH-aromatic), 7.37 (broad m, 4H, CH-aromatic), 7.29 (m,
H, CH-aromatic), 7.20 (m, 4H, CH-aromatic), 7.11 (s, 2H, CH-
imidazole), 6.11 (d, J = 7.5 Hz, 2H, CH-aromatic), 2.69 (septet, J =
.9 Hz, 4H, CH(CH ), 2.54 (septet, J = 6.9 Hz, 4H, CH(CH ), 1.07
d, J = 6.9 Hz, 12H, CH (CH ), 0.94 (d, J = 6.9 Hz, 12H, CH (CH ),
.86 (d, J = 6.9 Hz, 12H, CH (CH ) ), 0.68 (d, J = 6.9 Hz, 12H, CH
6
3
)
2
3 2
)
(
3
)
2
3
)
2
imidazole), 28.8 (s, CH (CH
3
)
2
), 28.7 (s, CH (CH
), 23.1 (s, CH (CH
AuSbF (1322.02): C, 57.22; H,
3
)
2
), 24.1 (s, CH
) ), 23.0 (s, CH
3 2
0
(CH
(CH
3
)
)
2
), 23.4 (s, CH (CH
). Anal. Calcd for C63
3
)
2
3
2
13
1
(
CH
carbene), 145.3 (s, C-aromatic), 144.3 (s, C-aromatic), 141.2 (s, C-aromatic),
36.5 (s, C-aromatic), 134.4 (s, C-aromatic), 131.5 (s, C-aromatic), 131.4 (s,
3
)
2
); C{ H} NMR (CD
2
Cl
2
): δ 165.0 (s, NC-imine), 164.8 (s, C-
3
2
H
76
N
4
6
5.72; N, 4.24. Found: C, 57.10; H, 5.80; N, 4.07.
t
Synthesis of [(I Bu)Au(BIAN)]PF
1
6
(4). A protocol similar to that used
t
C-aromatic), 130.8 (s, C-aromatic), 128.5 (s, C-aromatic), 128.3 (s, C-
aromatic), 127.2 (s, C-aromatic), 125.9 (s, C-aromatic), 125.7 (s, C-
aromatic), 124.9 (s, C-aromatic), 124.5 (s, C-imidazole), 28.8 (s, CH
for 1 gave 4 (from 100 mg, 0.24 mmol of (I Bu)AuCl)) as a clear brown
1
2 2
solid. Yield: 235 mg (94%). H NMR (CD Cl ): δ 8.10 (d, J = 8.4 Hz,
2H, CH-aromatic), 7.51ꢀ7.45 (broad m, 3H, CH-aromatic), 7.43
(
CH ) ), 28.7 (s, CH (CH ) ), 24.1 (s, CH (CH ) ), 23.4 (s, CH
(m, 1H, CH-aromatic), 7.39 (m, 2H, CH-aromatic), 7.36 (m, 2H,
3 2 3 2 3 2
2
248
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Organometallics
ARTICLE
CH-aromatic), 7.19 (s, 2H, CH-imidazole), 6.50 (d, J = 7.2 Hz, 2H, CH-
aromatic), 3.12 (septet, J = 6.9 Hz, 4H, CH(CH ) ), 1.74 (s, 18H,
CH-aromatic), 7.59ꢀ7.46 (broad m, 8H, CH-aromatic), 7.44 (m, 4H,
CH-aromatic), 7.33ꢀ7.26 (broad m, 11H, CH-aromatic), 6.78 (d, J =
3
2
C(CH
3
)
3
), 1.22 (d, J = 6.9 Hz, 12H, CH (CH
3
)
2
), 0.86 (d, J = 6.9 Hz,
): δ 165.3 (s, NC-imine),
60.3 (s, C-carbene), 144.2 (s, C-aromatic), 141.5 (s, C-aromatic), 137.1
3 2
7.2 Hz, 2H, CH-aromatic), 3.08 (septet, J = 6.9 Hz, 4H, CH(CH ) ),
13
1
1
1
2H, CH (CH
3
)
2
); C{ H} NMR (CD
2
Cl
2
3 2
1.11 (d, J = 6.9 Hz, 12H, CH (CH ) ), 0.99 (d, J = 6.9 Hz, 12H, CH
1
3
1
3
31
13
(CH ) ); C{ H} NMR (CD Cl ): δ (ppm) = 165.2 (d, J( Pꢀ C)
3
2
2
2
(
s, C-aromatic), 131.7 (s, C-aromatic), 128.7 (s, C-aromatic), 128.0 (s,
C-aromatic), 127.5 (s, C-aromatic), 126.0 (s, C-aromatic), 124.9 (s, C-
aromatic), 117.7 (s, CH-imidazole), 58.9 (s, C(CH ), 31.3 (s, C-
= 3.8 Hz, NC-imine), 144.0 (s, C-aromatic), 144.0 (s, C-aromatic), 143.1
2
31
13
(s, C-aromatic), 137.5 (s, C-aromatic), 134.6 (d, J( Pꢀ C) = 12.0 Hz,
1 31 13
2
31
13
3
)
3
C-aromatic), 134.5 (d, J( Pꢀ C) = 11.9 Hz, C-aromatic), 134.1 (d,
(
(
7
(
(
CH ) ), 28.8 (s, CH (CH ) ), 23.8 (s, CH (CH ) ), 23.5 (s, CH
J( Pꢀ C) = 22.3 Hz, C-aromatic), 133.3 (m, C-aromatic), 133.2 (m,
3 31 13
3
3
3 2
3 2
31
1
1
31
19
CH
12.1 Hz, PF
3
)
2
). P{ H} NMR (CD
2
Cl
2
): δ ꢀ141.3 (septet, J( Pꢀ F) =
C-aromatic), 132.8 (d, J( Pꢀ C) = 5.5 Hz, C-aromatic), 132.7 (d,
ꢀ
19
1
1
3
2
31
13
6
); F{ H} NMR (CD
2
Cl
2
): δ ꢀ73.9 (septet, J -
J( Pꢀ C) = 4.4 Hz, C-aromatic), 131.8 (s, C-aromatic), 130.4 (d,
31 13 2 31 13
3
1
19
ꢀ
Pꢀ F) = 712.1 Hz, PF
6
). Anal. Calcd for C47
H
60
N
4
AuPF
6
J( Pꢀ C) = 9.4 Hz, C-aromatic), 130.3 (d, J( Pꢀ C) = 9.8 Hz, C-
1 31 13
1022.94): C, 55.18; H, 5.91; N, 5.48. Found: C, 55.17; H, 6.56; N, 5.54.
aromatic), 129.8 (d, J( Pꢀ C) = 19.5 Hz, C-aromatic), 129.6 (d,
31 13
t
Synthesis of [(I Bu)Au(BIAN)]BF
1
4
(5). A protocol similar to that used
J( Pꢀ C) = 19.5 Hz, C-aromatic), 128.5 (s, C-aromatic), 128.3 (s, C-
3 31 13
t
for 2 gave 5 (from 100 mg, 0.24 mmol of (I Bu)AuCl)) as an orange
solid. Yield: 0.210 g (89%). H NMR (CD Cl ): δ 8.12 (d, J = 8.1 Hz,
aromatic), 127.6 (s, C-aromatic), 127.4 (d, J( Pꢀ C) = 3.7 Hz, C-
aromatic), 126.2 (s, C-aromatic), 125.3 (s, C-aromatic), 29.7 (s, CH
1
2
2
3
1
1
2
1
H, CH-aromatic), 7.52ꢀ7.45 (broad m, 3H, CH-aromatic), 7.43 (m,
(CH ) ), 23.5 (s, CH (CH ) ), 23.4 (s, CH (CH ) ); P{ H} NMR
3 2 3 2
3 2
31
1
19
H, CH-aromatic), 7.40 (m, 2H, CH-aromatic), 7.37 (m, 2H, CH-
(CD
2
Cl
2
19
): δ 32.3 (s, PPh
3
), ꢀ141.3 (septet, J( Pꢀ F) = 712.4 Hz,
ꢀ
1
1 31 19
aromatic), 7.24 (s, 2H, CH-imidazole), 6.51 (d, J = 7.5 Hz, 2H, CH-
aromatic), 3.13 (septet, J = 6.9 Hz, 4H, CH(CH ) ), 1.75 (s, 18H,
PF
6
); F{ H} NMR (CD
2
Cl
2
): δ ꢀ73.5 (septet, J( Pꢀ F) = 712.4
ꢀ
Hz, PF6 ). Anal. Calcd with crystals for C H N AuP F Cl
3
2
56 59
2
2
6
4
C(CH
3
)
3
), 1.22 (d, J = 6.9 Hz, 12H, CH (CH
3
)
2
), 0.87 (d, J = 6.9 Hz,
): δ 165.7 (s, NC-imine),
60.7 (s, C-carbene), 144.6 (s, C-aromatic), 142.0 (s, C-aromatic), 137.5
(1272.81): C, 52.76; H, 4.62; N, 2.19. Found: C, 52.60; H, 4.81; N, 2.06.
Synthesis of [(IPr)Au(DAB-Mes)](PF ) (8). In a flask, (IPr)AuCl (200
mg, 1 equiv, 0.32 mmol) was dissolved in 2 mL of dichloromethane with
13
1
1
1
2H, CH (CH
3
)
2
); C{ H} NMR (CD
2
Cl
2
6
(s, C-aromatic), 132.2 (s, C-aromatic), 131.4 (s, C-aromatic), 129.1 (s,
DAB-Mes (495 mg, 5 equiv, 1.60 mmol). Then TlPF was added (123 mg,
6
C-aromatic), 128.4 (s, C-aromatic), 127.9 (s, C-aromatic), 126.4 (s, C-
aromatic), 125.3 (s, C-aromatic), 118.2 (s, CH-imidazole), 59.2 (s,
C(CH ) ), 31.7 (s, C(CH ) ), 29.2 (s, CH (CH ) ), 24.2 (s, CH
1.1 equiv, 0.35 mmol), and the solution was stirred at room temperature for
16 h. The color of the reaction mixture went from yellow to bright orange
with the appearance of an intense orange precipitate of TlCl. The solution
was filtered over a plug of silica gel (3 g). After reduction of the volume of
DCM to 0.5 mL, 5 mL of pentane was added that led to the appearance of
3
3
3 3
3 2
19
1
(
CH ) ), 23.9 (s, CH (CH ) ); F{ H} NMR (CD Cl ): δ ꢀ153.7 (s,
3
ꢀ
2
3 2
2
2
BF
4
). Anal. Calcd for C47
H
60
N
4
AuBF
4
(964.97): C, 58.50; H, 6.21; N,
5
.80. Found: C, 58.81; H, 6.29; N, 5.87.
anorange precipitate. Thisprecipitate wasfilteredandwashedwith5 mL of
1
Synthesis of [(IMes)Au(BIAN)]PF (6). A protocol similar to that used
6
cold pentane. Yield: 274 mg (84%). H NMR (CD Cl ): δ 8.09 (s, 2H,
2 2
for 1 and 4 gave 6 (from 150 mg, 0.28 mmol of (IMes)AuCl)) as a clear
NCH), 7.40 (t, J = 7.8 Hz, 2H, CH-aromatic), 7.38 (s, 2H, CH-imidazole),
7.18 (d, J = 7.8 Hz, 4H, CH-aromatic), 6.90 (s, 4H, CH-aromatic), 2.38
1
orange solid. Yield: 0.270 g (85%). H NMR (CD Cl ): δ 8.06 (d, J = 8.1
2
2
Hz, 2H, CH-aromatic), 7.46ꢀ7.40 (broad m, 4H, CH-aromatic), 7.31
m, 4H, CH-aromatic), 7.10 (s, 2H, CH-imidazole), 6.81 (S, 4H, CH-
aromatic), 6.56 (d, J = 7.2 Hz, 2H, CH-aromatic), 2.74 (septet, J = 6.9
Hz, 4H, CH(CH ), 2.28 (s, 6H, CH ), 1.89 (s, 12H, CH ); 0.94 (d, J =
), 0.81 (d, J = 6.9 Hz, 12H, CH (CH );
): δ 165.5 (s, C-carbene), 163.7 (s, NC-imine),
(septet, J = 6.9 Hz, 4H, CH(CH
CH ), 1.18 (d, J = 6.9 Hz, 12H, CH (CH
(CH
imine), 145.5 (s, C-aromatic), 144.7 (s,C-aromatic), 137.8 (s, C-aromatic),
133.0 (s, C-aromatic), 131.3 (s, C-aromatic), 129.4 (s, C-aromatic), 127.2
(s, C-aromatic), 124.8 (s, C-aromatic), 124.2 (s, C-aromatic), 28.7 (s, CH
3
)
2
), 2.33 (s, 6H, CH
), 1.34 (d, J = 6.9 Hz, 12H, CH
3 2 2 2
) ); C{ H} NMR (CD Cl ): δ 167.6 (s, C-carbene), 165.2 (s, NC-
3
), 1.83 (s, 12H,
(
3
)
3 2
13
1
3
)
2
3
3
6
.9 Hz, 12H, CH (CH
C{ H} NMR (CD Cl
2
3
)
2
3 2
)
1
3
1
2
1
1
1
1
1
2
44.3 (s, C-aromatic), 141.6 (s, C-aromatic), 139.9 (s, C-aromatic),
36.3 (s, C-aromatic), 134.4 (s, C-aromatic), 131.5 (s, C-aromatic),
31.0 (s, C-aromatic), 129.6 (s, C-aromatic), 129.0 (s, C-aromatic),
28.7 (s, C-aromatic), 127.9 (s, C-aromatic), 127.2 (s, C-aromatic),
25.4 (s, C-aromatic), 124.5 (s, CH-imidazole), 123.9 (s, C-aromatic),
(CH
(s, CH
712.5 Hz, PF
= 712.5 Hz, PF
H, 5.87; N, 5.47. Found: C, 55.10; H, 6.11; N, 5.27.
3
)
2
), 24.0 (s, CH (CH
3
)
2
), 23.7 (s, CH (CH
). P{ H} NMR (CD Cl
): δ ꢀ141.3 (septet, J( Pꢀ F) =
); F{ H} NMR (CD
3 2 3
) ), 20.6 (s, CH ), 17.7
3
1
1
1
31
19
3
2
2
ꢀ
19
1
1
31
19
Cl
). Anal. Calcd for C47
):δꢀ74.1 (septet, J( Pꢀ F)
6
2
2
ꢀ
6
H
60
N
4
AuPF (1022.94): C, 55.18;
6
8.9 (s, CH (CH
3
)
2
), 22.9 (s, CH (CH
3
)
2
), 22.5 (s, CH (CH
3
)
2
), 20.8
Synthesis of (BIAN-dipp)AuCl (9). In a flask, BIAN-dipp (60 mg, 1
equiv, 0.12 mmol) was dissolved in 2 mL of dichloromethane, and AuCl
was added (84 mg, 3 equiv, 0.36 mmol). The solution was stirred at room
temperature for 16 h. The color of the reaction mixture went from yellow
to dark red with the appearance of a metallic gold(0) precipitate. The
solution was filtered over a plug of silica gel (2 g). After reduction of the
volume of DCM to 0.5 mL, 5 mL of pentane was added that led to the
appearance of a brick red precipitate. This precipitate was filtered, washed
31
1
(
s, CH ), 17.2 (s, CH
3
3
); P{ H} NMR (CD Cl
2
2
): δ ꢀ141.3 (septet,
1
31
19
ꢀ
19
1
J( Pꢀ F) = 712.0 Hz, PF ); F{ H} NMR (CD Cl ): δ ꢀ74.0
6
2
2
1
31
19
ꢀ
(
septet, J( Pꢀ F)
AuPF
9.27; H, 5.42; N, 4.66.
Synthesis of [(PPh )Au(BIAN)]PF
mg, 1 equiv, 0.40 mmol) was dissolved in 5 mL of dichloromethane with
BIAN (202 mg, 1.01 equiv, 0.41 mmol). Then TlPF was added (157
=
712.0 Hz, PF
6
). Anal. Calcd for
C
5
57
H
64
N
4
6
(1147.08): C, 59.68; H, 5.62; N, 4.88. Found: C,
3
6 3
(7). In a flask, (PPh )AuCl (200
1
6
with 5 mL of cold pentane. Yield: 56 mg (64%). H NMR (CD Cl ): δ
2
2
mg, 1.1 equiv, 0.45 mmol), and the solution was stirred at room
temperature for 16 h. The color of the reaction mixture went from
yellow to dark red with the formation of a white precipitate of TlCl. The
solution was filtered through a plug of silica gel (3 g). After reduction of
the volume of DCM to 0.5 mL, 5 mL of pentane was added that led to
the appearance of a dark red precipitate. This precipitate was filtered and
8.09 (broad d, J = 8.1 Hz, 2H, CH-aromatic), 7.51 (t, J = 7.8 Hz, 2H, CH-
aromatic), 7.41ꢀ7.35 (broad m, 6H, CH-aromatic), 6.83 (d, J = 6.9 Hz,
1.35H, CH-aromatic), 6.67 (d, J = 6.9 Hz, 0.64H, CH-aromatic), 3.10
(broadm, 1H, CH(CH ) ), 2.95(septet, J=6.9 Hz,4H,CH(CH ) ), 1.37
3
2
3 2
(d, J =6.9 Hz, 3H, CH (CH ) ), 1.24 (d, J =6.6 Hz, 9H, CH (CH ) ), 1.03
3
2
3 2
1
3
1
(m, 12H, CH (CH ) ); C{ H} NMR (CD Cl ): δ 161.3 (s, NC-imine),
3
2
2
2
1
31
washed with 5 mL of cold pentane. H and P NMR spectra exhibited
the desired complex slightly contaminated (less than 5%) by
144.7 (s, C-aromatic), 142.1 (s, C-aromatic), 141.6 (s, C-aromatic), 136.9
(s, C-aromatic), 131.2 (s, C-aromatic), 130.6 (s, C-aromatic), 129.0 (s, C-
aromatic), 128.4 (s, C-aromatic), 128.1 (s, C-aromatic), 127.4 (s, C-
aromatic), 125.7 (s, C-aromatic), 124.6 (s, C-aromatic), 124.4 (s, C-
aromatic), 123.9 (s, C-aromatic), 29.0 (s, CH (CH ) ), 28.9 (s, CH
[Au(PPh
3 2 6
) ]PF as a side product from the synthesis. This impurity
was discarded by slow crystallization from a mixture of octane and DCM.
1
2 2
Yield: 349 mg (79%). H NMR (CD Cl ): δ 8.18 (d, J = 8.4 Hz, 2H,
3
2
2
249
dx.doi.org/10.1021/om2000426 |Organometallics 2011, 30, 2241–2251

Organometallics
ARTICLE
(
(
3
CH
3
)
2
), 23.4 (s, CH (CH
3
)
2
), 22.9 (s, CH (CH
3
)
2
), 22.6 (s, CH
46, 5841–5843. (c) Guan, B.; Xing, D.; Cai, G.; Wan, X.; Yu, N.; Fang, Z.;
Yang, L.; Shi, Z. J. Am. Chem. Soc. 2005, 127, 18004–18005.
(3) (a) de Fr ꢀe mont, P.; Marion, N.; Nolan, S. P. J. Organomet. Chem.
2009, 694, 551–560. (b) Lavallo, V.; Frey, G. D.; Donnadieu, B.;
Soleilhavoup, M.; Bertrand, G. Angew. Chem., Int. Ed. 2008, 47,
CH ) ). Anal. Calcd for C H N AuCl (733.14): C, 59.42; H, 4.45; N,
3
2
36 40 2
.81. Found: C, 59.65; H, 5.68; N, 3.67.
6 2
Synthesis of [((IPr)Au) (DABMes)](PF ) (10). In a vial, 100 mg of 8
2
was placed and dissolved in 0.5 mL of DCM. Then a thin layer of n-octane
was added, triggering the formation of dark orange crystals in a pale yellow
solution after 24 h. X-ray diffraction of two different sets of crystals
5
224–5228. (c) de Fr ꢀe mont, P.; Stevens, E. D.; Fructos, M. R.; Diaz-
Requejo, M. M.; P ꢀe rez, P. J.; Nolan, S. P. Chem. Commun. 2006,
045–2047.
4) Hill, N. J.; Vargas-Baca, I.; Cowley, A. H. Dalton Trans.
2009, 240–253 and references therein.
5) (a) Warsink, S.; Chang, I.-H.; Weigand, J. J.; Hauwert, P.; Chen,
2
revealed the unexpected formation of 10. This transformation from 8 to
1
(
1
0 appeared quantitative and was confirmed by H NMR spectroscopy.
1
H NMR (CD
aromatic), 7.32 (s, 4H, CH-imidazole), 7.13 (d, J = 7.8 Hz, 8H, CH-
aromatic), 6.88 (s, 4H, CH-aromatic), 2.41 (s, 6H, CH ), 2.28 (septet, J =
.9 Hz, 8H, CH(CH ) ), 1.46 (s, 12H, CH ), 1.12 (d, J = 6.9 Hz, 24H,
2 2
Cl ): δ 7.97 (s, 2H, NCH), 7.43 (t, J = 7.8 Hz, 4H, CH-
(
J.-T.; Elsevier, C. J. Organometallics 2010, 29, 4555–4561. (b) Kern, T.;
Monkowius, U.; Zabel, M.; Kn €o r, G. Eur. J. Inorg. Chem. 2010,
4148–4156. (c) Singh, A.; Anandhi, U.; Cinellu, M. A.; Sharp, P. R.
Dalton Trans. 2008, 2314–2327. (d) Durand, J.; Milani, B. Coord. Chem.
Rev. 2006, 250, 542–560. (e) Klein, A.; Schurr, T.; Z ꢀa li ꢂs , S. Z. Anorg. Allg.
Chem. 2005, 631, 2669–2676. (f) Valente, A. A.; Moreira, J.; Lopes,
A. D.; Pillinger, M.; Numes, C. D.; Rom ~a o, C. C.; K €u hn, F. E.;
Gon c- alves, I. S. New J. Chem. 2004, 28, 308–313. (g) Z ꢀa li ꢂs , S.; Amor,
N. B.; Daniel, C. Inorg. Chem. 2004, 43, 7978–7985. (h) Wik, B. J.;
Rømming, C.; Tilset, M. J. Mol. Cat. A: Chem. 2002, 189, 23–32. (i)
Tromp, D. S.; Duin, M. A.; Kluwer, A. M.; Elsevier, C. J. Inorg. Chim. Acta
2002, 327, 90–97. (j) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem.
Rev. 2000, 100, 1169–1203.
3
6
3
2
3
31
1
3 2 3 2
CH (CH ) ), 0.91 (d, J = 6.9 Hz, 24H, CH (CH ) ). P{ H} NMR
1
31
19
ꢀ
19
1
(CD
2
Cl
2
): δ ꢀ141.3 (septet, J( Pꢀ F) = 712.1 Hz, PF
6
); F{ H}
1
31
19
ꢀ
NMR (CD Cl ): δ ꢀ74.0 (septet, J( Pꢀ F) = 712.1 Hz, PF ).
2
2
6
Cycloisomerization General Procedure. A Schlenk flask, under
nitrogen, was charged with the catalyst (0.025 mmol, 0.05 equiv) and
dry dichloromethane (1 mL), and then enyne 11 (162 mg, 0.5 mmol, 1
equiv) and indole (60 mg, 0.55 mmol, 1.1 equiv) in solution in
dichloromethane (1 mL) were added. The mixture was stirred for
17 h at room temperature. Reaction progress was monitored by TLC
(pentane/ether 8:2). The reaction mixture was directly purified by
column chromatography on silica gel (dichloromethane) to afford the
products as an inseparable mixture. NMR data were found in good
agreement with the literature. They are reported in the Supporting
Information.
(6) (a) Hashmi, A. S. K. Angew. Chem., Int. Ed. 2010, 49, 5232–5241.
(b) Díez-Gonz ꢀa lez, S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009,
109, 3612–3676. (c) Di ꢀa z-Requejo, M. M.; P ꢀe rez, P. J. Chem. Rev.
2008, 108, 3379–3394. (c) Arcadi, A. Chem. Rev. 2008, 108, 3266–3325.
13
(
d) Li, Z.; Brouwer, C.; He, C. Chem. Rev. 2008, 108, 3239–3265.
7) (a) Bartolom ꢀe , C.; Ramiro, Z.; García-Cuadrado, D.; P ꢀe rez-Gal ꢀa n,
P.; Raducan, M.; Bour, C.; Echavarren, A. M.; Espinet, P. Organometallics
010, 29, 951–956. (b) L ꢀo pez-Carillo, V.; Echavarren, A. M. J. Am. Chem.
(
’
ASSOCIATED CONTENT
2
S
Supporting Information. Experimental procedures and/
b
Soc. 2010, 132, 9292–9294. (c) Gimeno, A.; Medio-Sim ꢀo n, M.; Ramírez de
Arellano, C.; Asensio, G.; Cuenca, A. B. Org. Lett. 2010, 12, 1900–1903. (d)
Saito, A.; Konishi, T.; Hanzawa, Y. Org. Lett. 2010, 12, 372–374. (e)
Gorske, B. C.; Mbofana, C. T.; Miller, S. J. Org. Lett. 2010, 12, 4318–4321.
(f) Hadfield, M. X.; Lee, A. L. Org. Lett. 2010, 12, 484–487. (g) Zeng, X.;
Kinjo, R.; Donnadieu, B.; Bertrand, G. Angew. Chem., Int. Ed. 2010,
49, 942–945. (h) Ram ꢀo n, R. S.; Bosson, J.; Díez-Gonz ꢀa lez, S.; Marion,
N.; Nolan, S. P. J. Org. Chem. 2010, 75, 1197–1202. (i) Zeng, X.;
Soleihavoup, M.; Bertrand, G. Org. Lett. 2009, 11, 3166–3169. (j) Hashmi,
A. S. K.; Schuster, A. M.; Rominger, F. Angew. Chem., Int. Ed. 2009,
or characterizations of 10, 11, 16, and 17. Crystallographic
information files (CIF) of the complexes 3, 5, 6, 7, and 10.
(
CIF files have also been deposited with the CCDC, 12 Union
Rd., Cambridge, CB2 1EZ, U.K., and can be obtained on request
free of charge, by quoting the publication citation and deposition
numbers 802668ꢀ802672.) This material is available free of
charge via the Internet at http://pubs.acs.org.
’
AUTHOR INFORMATION
4
2
1
8, 8247–8249. (k) Marion, N.; Ram ꢀo n, R. S.; Nolan, S. P. J. Am. Chem. Soc.
009, 131, 448–449. (l) Li, G.; Zhang, G.; Zhang, L. J. Am. Chem. Soc. 2008,
30, 3740–3741. (m) Nieto-Oberhuber, C.; P ꢀe rez-Gal ꢀa n, P.; Herrero-
Corresponding Author
*E-mail: braunstein@unistra.fr; defremont@unistra.fr.
G ꢀo mez, E.; Lauterbach, T.; Rodríguez, C.; L ꢀo pez, S.; Bour, C.; Rosell ꢀo n,
A.; C ꢀa rdenas, D. J.; Echavarren, M. A. J. Am. Chem. Soc. 2008,
1
1
30, 269–279. (n) Zhang, Z.; Widenhoefer, R. A. Org. Lett. 2008,
0, 2079–2080. (o) Kar, A.; Mangu, N.; Kaiser, H. M.; Beller, M.; Kin
’
ACKNOWLEDGMENT
The Centre National de la Recherche Scientifique (CNRS),
Tse, M. Chem. Commun. 2008, 386–388. (p) Kinder, R. E.; Zhang, Z.;
Windenhoefer, R. A. Org. Lett. 2008, 10, 3157–3159. (q) Bender, C. F.;
Windenhoefer, R. A. Chem. Commun. 2008, 2741–2743.
the Minist ꢁe re de la Recherche and the Funda c- ~a o para a Ci ^e ncia e
Tecnologia (FCT) (postdoctoral fellowship (SFRH/BPD/
4
4262/2008) to Dr. Vitor Rosa) are gratefully acknowledged
(8) (a) Coventry, D. N.; Batsanov, A. S.; Goeta, A. E.; Howard,
J. A. K.; Marder, T. B. Polyhedron 2004, 23, 2789–2795. (b) El-Ayaan,
U.; Paulovicova, A.; Fukuda, Y. J. Mol. Struct. 2003, 645, 205–212.
for financial support of this work. We thank some colleagues
from the Universit ꢀe de Strasbourg: Dr. Roberto Pattacini and
Dr Lydia Brelot for their help with the treatment of crystal-
lographic data, and visiting Prof. Andreas Danopoulos for some
fruitful discussions.
(
9) de Fr ꢀe mont, P.; Scott, N. M.; Stevens, E. D.; Nolan, S. P.
Organometallics 2005, 24, 2411–2418.
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(
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dx.doi.org/10.1021/om2000426 |Organometallics 2011, 30, 2241–2251

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(
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dx.doi.org/10.1021/om2000426 |Organometallics 2011, 30, 2241–2251