Cyclic (alkyl)(amino)carbene gold(I) complexes: A synthetic and structural investigation

Article abstract of DOI:10.1016/j.jorganchem.2008.01.026

A series of mono- and dicarbene gold(I) complexes of types Au(CAAC)(Cl) [CAAC = cyclic (alkyl)(amino)carbene] (1) and [Au(CAAC)₂]⁺[X]^- (X = Cl, AuCl₂) (2) have been prepared through reaction of AuCl(SMe₂) with free carbenes a-e, and structurally characterized by single X-ray diffraction studies (1a, 1b, 2d, 2e). In addition two new free cyclic (alkyl)(amino)carbenes (c and e) have been synthesized.

Full text of DOI:10.1016/j.jorganchem.2008.01.026

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1674–1682
www.elsevier.com/locate/jorganchem
Cyclic (alkyl)(amino)carbene gold(I) complexes: A synthetic
and structural investigation
Guido D. Frey, Rian D. Dewhurst, Shazia Kousar, Bruno Donnadieu, Guy Bertrand *
UCR-CNRS Joint Research Chemistry Laboratory (UMI 2957), Department of Chemistry, University of California, Riverside, CA 92521-0403, USA
Received 16 December 2007; received in revised form 16 January 2008; accepted 16 January 2008
Available online 20 January 2008
Abstract
A series of mono- and dicarbene gold(I) complexes of types Au(CAAC)(Cl) [CAAC = cyclic (alkyl)(amino)carbene] (1) and
[Au(CAAC)2]+[X]À (X = Cl, AuCl2) (2) have been prepared through reaction of AuCl(SMe2) with free carbenes a–e, and structurally
characterized by single X-ray diffraction studies (1a, 1b, 2d, 2e). In addition two new free cyclic (alkyl)(amino)carbenes (c and e) have
been synthesized.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Stable carbenes; Carbene complexes; Gold
1. Introduction
uscript describes the synthesis and characterization of a ser-
ies of Au(I) complexes, featuring one or two CAACs,
depending on the bulkiness of the carbene ligand.
Following the discovery of the first stable derivatives
[1,2], singlet carbenes have received considerable attention
as ligands for transition metals [3,4]. Carbenes feature a
strong r-donating ability, and strongly bind metal centers
of high and low oxidation states [5]. Additionally, the pos-
sibility to tune their electronic and steric properties by var-
iation of substituents [6], make carbenes versatile ligands
for transition metal catalysts [7]. Since the Au(I) catalyzed
asymmetric aldol reaction was published in the late 1980s
[8], the use of Au(I) complexes in catalysis has received a
lot of attention [9,10]. The first NHC substituted neutral
and cationic gold(I) complexes were published in 1989
[11], and their application in catalysis stated in 2003 [12].
We have already reported the synthesis and isolation of
well-defined cyclic (alkyl)(amino)carbenes (CAAC) [13a],
their use for the activation of small molecules [13b,13c,
13d], their properties as ligand for transition metals
[13e,13f], and recently the preparation of a CAAC gold(I)
complex, which allows for the catalytic formation of
allenes, starting from enamines and alkynes [14]. This man-
The free carbenes (a–e) including the new ones (c and e)
were readily prepared by deprotonation with LDA of the
corresponding iminium salts; the latter were synthesized
using the hydroiminiumation route [15] as shown in
Scheme 1.
The gold complexes 1a–d were then cleanly prepared by
stirring the free carbenes a–d overnight in darkness in THF
with AuCl(SMe2), the same procedure used for the corre-
sponding NHC complexes [16]. After removing the solvent
under vacuum and washing with hexanes, the remaining
residue was extracted with CH2Cl2 or CHCl3. All com-
plexes 1a–d were isolated as colorless analytically pure
microcrystalline material in good yields (Scheme 2). They
are readily soluble in most common polar solvents
(CH2Cl2, CHCl3, THF), sparingly in diethyl ether and
insoluble in hexanes. Single crystals of complexes 1a and
1b, suitable for X-ray diffraction studies (Fig. 1), were
obtained by slow evaporation of the solvent (CH2Cl2 or
CHCl3). Complexes 1a–d are slightly unstable when
exposed to incandescent light (giving gold metal) but ther-
mally stable in the solid state at room temperature over
several months. The 13C NMR signals for the carbene
*
Corresponding author.
E-mail address: gbertran@mail.ucr.edu (G. Bertrand).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.01.026

G.D. Frey et al. / Journal of Organometallic Chemistry 693 (2008) 1674–1682
1675
H
C
1) LiNMe2
2)
LDA
1) HCl
N
N
C
N
C
Y
Y
N
C
Y
Y
2) Δ
Cl
HCl2
H
H
H
aa-ea
ac-ec
a-e
ab-eb
,
,
,
,
C
C
C
C
C
C
=
Y
b
c
d
e
a
Scheme 1. Synthesis of carbenes a–e.
carbon atom of gold complexes 1a–d (1a, 237.1; 1b, 239.9;
1c, 236.4; 1d, 235.0 ppm) are shifted toward high field com-
pared to those observed for the corresponding free carb-
enes a–d (309–322 ppm).
Under the same reaction conditions, a different behavior
was observed for carbene e. In this case the reaction of a
stoichiometric amount of e with AuCl(SMe2) did not afford
the expected mono-carbene gold complex (similar to 1a–d),
but the cationic dicarbene gold complex 2e with AuCl2À as
counteranion (Scheme 3), as demonstrated by a single crys-
tal X-ray diffraction study (Fig. 2). The different nature of
2e, compared to 1a–d, is also apparent from the 13C NMR
spectra, since the carbene carbon gives a signal at
249.7 ppm, some 10–14 ppm downfield compared to those
observed for 1a–d. This result suggests that a disproportion
reaction occurs, as already observed for related NHC–sil-
ver complexes [12,17,18]. Indeed, we found that all
attempts to recrystallize complex 1d from a CD2Cl2 solu-
tion over several days also led to the homoleptic gold car-
bene complex 2d, with chloride as counteranion, as shown
by an X-ray single crystal structure (Fig. 2). Here again, the
13C NMR signal for the carbene carbon of 2d appeared at
lower field (251.2 ppm) than that observed for 1d
(235.0 ppm).
N
C
Au(SMe2)Cl
THF, rt, 14h
a-d
Au
Cl
1a-d
C
C
C
C
All complexes (1a, 1b, 2d, 2e) show the expected linear
coordination of the two ligands at the gold atom
[Ccarbene–Au–X angle (X = Cl, C) between 175.78(6)° [1b]
and 180° [2d, 2e]] (Table 1), and are in agreement with
b
c
d
a
Scheme 2. Synthesis of mono substituted CAAC Au(I) complexes 1a–d.
Fig. 1. Ball and Stick plots of complexes 1a and 1b in the solid state. Hydrogen atoms are omitted for clarity. Some pertinent metric parameters are given
in Table 1.

1676
G.D. Frey et al. / Journal of Organometallic Chemistry 693 (2008) 1674–1682
plexes [24,25]. For all four gold complexes (1a, 1b, 2d and
2e), no aurophilic interactions between the Au atoms were
˚
N
C
observed (>7.4 A).
The steric hindrance and the flexibility of the carbene
carbon substituents have a dramatic effect on the synthetic
outcome of the complexation reactions at gold centers.
When bulky and rigid substituents are present at carbon,
LAuCl complexes 1a,b are isolated, whereas the use of
the smaller non-substituted cyclohexyl and cyclohexylene
groups (d, e) give rise to cationic di(carbene) complexes
2d,e. However, despite the presence of relatively small sub-
stituents, the non-spiro carbene c behaves as a and b; this is
probably due to the higher flexibility of the substitution
motive (or to an interaction between the metal and the ben-
zene ring). Given the likelihood that di(carbene) complexes
of type 2 are at least partially deactivated in terms of catal-
ysis, these results give a first indication of the range of the
substituents, which might allow CAAC gold complexes to
find catalytic applications.
Au
Cl
1d
Au(SMe2)Cl
THF, rt, 14h
slow
d-e
+ X-
N
C
C
Dipp
Au
Dipp
N
C
C
d
e
2d: X = Cl;
2e: X = AuCl2
Scheme 3. Synthesis of homoleptic dicarbene Au(I) complexes 2d and 2e.
2. Experimental
the literature for gold(I) complexes [12,20–31]. The Au–
All reactions were performed under an atmosphere of
argon and solvents were dried over Na metal or CaH2.
Reagents were of analytical grade, obtained from commer-
cial suppliers and used without further purification. 1H
NMR (300 MHz), and 13C{1H}NMR (75 MHz) spectra
were obtained with a Bruker Avance 300 spectrometer at
298 K. 1H and 13C chemical shifts (d) are reported in parts
per million (ppm) relative to TMS and were referenced to
the residual solvent peak. NMR multiplicities are
˚
Ccarbene bond lengths in 1a (1.987(9) A) and 1b
˚
(1.983(2) A) are comparable with those found in substi-
tuted NHC gold(I) chloro complexes [12,18,19], and sug-
gest a single bond character, in good agreement with the
strong r-donor character of CAACs. The cationic com-
plexes 2d and 2e have slightly longer Au–Ccarbene bond
˚
lengths [2.0321(11) and 2.033(4) A, respectively] in the
range observed for cationic dicarbene (NHC) gold(I) com-
Fig. 2. Ball and Stick plots of complexes 2d and 2e in the solid state. Hydrogen atoms are omitted for clarity. Some pertinent metric parameters are given
in Table 1.

G.D. Frey et al. / Journal of Organometallic Chemistry 693 (2008) 1674–1682
1677
Table 1
Pertinent bond distances and angles for complexes 1a, 1b, 2d, and 2e
Compound
1a
1b
2d
2e
˚
Au–Ccarbene [A]
1.987(9)
1.259(11)
1.572(13)
1.508(11)
1.534(13)
1.527(12)
178.6(2)
108.8(8)
1.983(2)
1.304(3)
1.531(3)
1.525(2)
1.551(3)
1.531(3)
175.78(6)
109.6(2)
2.0321(11)
1.304(2)
1.512(2)
1.530(2)
1.548(2)
1.540(2)
180
2.033(4)
1.297(5)
1.506(5)
1.529(5)
1.566(8)
1.538(9)
180
˚
Ccarbene–N [A]
carbene–Cspiro [A]
˚
C
˚
N–CMe2 [A]
˚
spiro–CH2 [A]
C
˚
CMe2–CH2 [A]
Ccarbene–Au–X (X = C, Cl) [°]
N–Ccarbene–Cq [°]
109.99(10)
110.4(3)
abbreviated as follows: s = singlet, d = doublet, t = triplet,
sept. = septet, m = multiplet, br = broad signal. Coupling
constants (J) are reported in hertz (Hz). High-resolution
fast atom bombardment (FAB) mass spectra were obtained
at the UC Riverside Mass Spectrometry Laboratory. Melt-
ing points were measured with a Buchi melting point appa-
¨
ratus system (Dr. Tottoli). Free carbenes a, b, and d were
prepared according to the literature [15].
(d, 3J = 6.8 Hz, 6H, CH(CH3)2), 1.12 (d, 3J = 6.8 Hz,
12H, CH(CH3)2). 13C{1H} NMR (CDCl3)
172.4
d
(NCH), 148.7 (Cq), 146.8 (Cq), 142.4 (Cq), 137.4 (Cq),
135.1 (Cq), 130.9 (CH), 126.1 (CH), 123.9 (CH), 122.9
(CH), 115.5 (CH2), 46.4 (CH2), 44.9 (Cq), 44.5 (CH2),
33.8 (CH3), 27.5, 25.5, 24.2, 23.6, 22.6. FAB-HRMS calcd
for C29H42N [M+H]+: m/z 404.3317; found, 404.3314. To
a solution of cb (6.71 g, 16.63 mmol) in acetonitrile
(10 mL) was added a solution of HCl in Et2O (2M,
20.7 mL, 41.6 mmol). The vessel was sealed, and heated
to 80 °C for 14 h. The acetonitrile was removed, and the
residue was extracted twice with boiling toluene
(20 mL). After cooling to room temperature, the suspen-
sion was filtered, washed with toluene and dried to obtain
2.1. Carbene c
2,6-Diisopropylaniline (5.00 mL, 4.70 g, 26.5 mmol)
was added at room temperature to a reaction flask con-
taining molecular sieves (15 g) and a hexane solution
(50 mL) of 2-methyl-3-(p-isopropylphenyl)propionalde-
hyde (5.84 mL, 5.55 g, 29.2 mmol). The reaction mixture
was stirred for 18 h. The molecular sieves were removed
by filtration, and the hexane was removed in vacuo. After
removal of the excess 2,6-diisopropylaniline by short path
distillation at 170 °C under vacuum, imine ca was
obtained as a light yellow oil. Yield: 6.52 g (70%). 1H
NMR (CDCl3) d 7.57 (d, 3J = 4.5 Hz, 1H, NCH), 7.22
(br, 4H, Har), 7.12 (br, 3H, Har), 3.11–2.74 (m, 6H,
CH(CH3)2 + CH2 + CHCHCH3), 1.30 (d, 3J = 6.6 Hz,
9H, CH(CH3)2 + CHCHCH3), 1.12 (d, 3J = 6.8 Hz,
1
cc (X = HClÀ2 ) as a white solid. Yield: 5.74 g (72%). H
NMR (CD3CN)
d 9.39 (s, 1H, NCH), 7.59 (t,
3J = 7.7 Hz, 1H, Har), 7.44 (t, 3J = 6.8 Hz, 2H, Har),
3
3
7.34 (d, J = 7.7 Hz, 2H, Har), 7.28 (d, J = 7.7 Hz, 1H,
Har), 6.13 (br s, 1H, HCl2), 3.47 (d, 3J = 14.0 Hz, 1H,
CH2), 3.03 (d, 3J = 14.0 Hz, 1H, CH2), 2.96 (sept.,
3J = 6.9 Hz, 1H, CH(CH3)2), 2.66 (sept., 3J = 6.7 Hz,
1H, CH(CH3)2), 2.64 (d, 2J = 14.0 Hz, 1H, CH2), 2.35
2
3
(d, J = 14.0 Hz, 1H, CH2), 2.15 (sept., J = 6.6 Hz, 1H,
CH(CH3)2), 1.73 (s, 3H, CH3), 1.42 (s, 3H, CH3), 1.35
(d, 3J = 6.7 Hz, 3H, CH(CH3)2), 1.26 (d, 3J = 6.8 Hz,
6H, CH(CH3)2), 1.13 (m, 9H, CH3), 0.93 (s, 3H, CH3).
13C{1H}NMR (CD3CN) d 192.8 (NCH), 149.3 (Cq),
145.6 (Cq), 145.0 (Cq), 134.7 (Cq), 132.6 (CH), 131.1
(CH), 129.7 (Cq), 127.7 (CH), 126.5 (CH), 125.9 (CH),
84.7 (NC(CH3)2), 55.3 (Cq), 44.1 (CH2), 43.8 (CH2),
34.4, 30.1, 29.8, 28.5, 27.6, 26.3, 24.2, 22.0, 21.8. FAB-
HRMS calcd for C29H42N [M]+: m/z 404.3317; found,
404.3317.
12H, CH(CH3)2). 13C{1H}NMR (CDCl3)
d
170.1
(NCH), 148.7 (Cq), 146.4 (Cq), 137.1 (Cq), 136.7 (Cq),
128.9 (CH), 126.3 (CH), 123.8 (CH), 122.6 (CH), 41.7
(NCHCH), 39.6 (CH2), 33.7 (CH), 27.4 (CH(CH3)2),
24.1 (CH), 23.4 (CH(CH3)2), 23.3 (CH(CH3)2), 17.4
(CHCH3). FAB-HRMS calcd for C25H36N [M+H]+: m/
z 350.2848; found, 350.2852. A solution of ca (6.52 g,
18.7 mmol) was added slowly to a solution of LiNMe2
(1.00 g, 19.6 mmol) in Et2O (20 mL). The mixture was
allowed to warm to room temperature, and then stirred
for 2 h. 3-Chloro-2-methyl-1-propene (2.03 g, 2.19 mL,
22.4 mmol) was added slowly under stirring to this solu-
tion. After stirring for 2 h, all volatiles were removed in
vacuo. Hexanes (20 mL) were added and the suspension
was filtered. The solvent was evaporated to give com-
pound cb as an oil. Yield: 6.71 g (89%). 1H NMR
(CDCl3) d 7.72 (s, 1H, NCH), 7.27–7.06 (m, 7H, Har),
4.95 (s, 1H, CH), 4.82 (s, 1H, CH), 2.95 (s, 2H, CH2),
2.86 (sept., 3J = 6.8 Hz, 3H, CH(CH3)2), 2.43 (d,
2J = 13.8 Hz, 1H, CH2), 2.31 (d, 2J = 13.8 Hz, 1H,
CH2), 1.84 (s, 3H, CH3), 1.31 (s, 3H, CH3), 1.27
To a Schlenk tube containing the iminium salt cc
(X = HClÀ2 ) (4.86 g, 10.20 mmol) and NaBPh4 (3.49 g,
10.20 mmol) was added methylene chloride (40 mL). The
mixture was stirred for 1 h at room temperature and fil-
tered afterwards through Celite (3 g). The solvent was
removed in vacuo, and the residue was extracted twice with
boiling hexanes. The hexanes extract was cooled to À20 °C,
and the solution was decanted from the solid. The solid was
dried in vacuo to yield cc (X = BPhÀ4 ) 5.31 g (72%) as a
white powder. A solution of KHMDS (419 mg, 2.10 mmol)
in THF (10 mL) was added slowly to a solution of cc (X =
BPhÀ4 ) (500 mg, 1.05 mmol) in THF (10 mL) at À78 °C.
The mixture was allowed to warm to room temperature,

1678
G.D. Frey et al. / Journal of Organometallic Chemistry 693 (2008) 1674–1682
and stirred for 1 h. The THF was removed and the residue
was extracted with hexanes (10 + 5 mL), filtered and the
hexanes was removed yielding colorless crystals of free car-
3H), 2.03–1.96 (m, 1H, CH2), 1.88–1.77 (m, 1H, CH2),
1.85 (s, 3H, CH3), 1.18 (d, J = 6.9 Hz, 6H, CH(CH3)2),
3
1.17 (d, 3J = 6.9 Hz, 6H, CH(CH3)2). 13C{1H}NMR
(CDCl3) d 171.2 (NCH), 149.2 (Co,ar), 142.0 (CCH2),
137.0 (Cm,ar), 126.4 (CH), 125.8 (CH), 124.1 (CH), 122.9
(CH), 115.6 (CCH2), 46.2 (CH2), 42.8 (NCHCq), 32.7
(CH2), 30.3 (CH2), 27.6 (CH), 25.4 (CH3), 23.8 (CH3),
23.3 (CH2). FAB-HRMS calcd for C23H34N [M+H]+: m/z
324.2691; found, 324.2697. To a solution of eb (3.04 g,
9.44 mmol) in acetonitrile (10 mL) was added a solution
of HCl in Et2O (2 M, 9.44 mL, 18.82 mmol). The vessel
was sealed, and heated to 90 °C for 16 h. The acetonitrile
was removed, and the residue was extracted twice with boil-
ing toluene (20 mL). After cooling to À20 °C, the suspen-
sion was filtered, washed with toluene and dried. ec with
HClÀ2 as a counteranion was obtained as a white solid.
Yield: 2.95 g (79%). M.p. 164–166 °C (dec.). 1H NMR
(CD3CN) d 12.88 (s, 1H, HCl2), 9.17 (s, 1H, NCH), 7.62
1
bene c. Yield: 236 mg (56%). H NMR (C6D6) d 7.75 (m,
3
1H, Har), 7.38–7.20 (m, 6H, Har), 3.93 (sept., J = 6.9 Hz,
3
1H, CH(CH3)2), 3.80 (sept., J = 6.8 Hz, 1H, CH(CH3)2),
3.78 (d, J = 8.2 Hz, 1H), 3.60 (sept., 3J = 6.4 Hz, 1H,
CH(CH3)2), 3.28 (d, J = 8.3 Hz, 1H, CH2), 2.87 (s, 3H,
CH3), 2.15 (d, 2J = 12.7 Hz, 1H, CH2), 1.79 (d,
2J = 12.7 Hz, 1H, CH2), 1.45 (d, 3J = 6.9 Hz, 3H,
3
CH(CH3)2), 1.37 (d, J = 6.9 Hz, 3H, CH(CH3)2), 1.36 (s,
3H, CH(CH3)2), 1.36 (d, 3J = 6.6 Hz, 3H, CH(CH3)2),
1.29–1.25 (9H, CH(CH3)2), 1.19 (d, 3J = 6.9 Hz, 3H,
CH(CH3)2). 13C{1H}NMR (C6D6) d 313.0 (Ccarbene),
152.7 (Cq), 152.5 (Cq), 147.0 (Cq), 139.2 (Cq), 137.7 (Cq),
131.0 (CH), 127.6 (CH), 126.6 (CH), 124.8 (CH), 124.7
(CH), 80.7 (NC(CH3)2), 61.2 (Cq), 51.5 (CH2), 46.5
(CH2), 34.4, 30.1, 29.8, 28.5, 27.6, 26.3, 24.2, 22.0, 21.8.
3
(t,3J = 7.8 Hz, 1H, Hp,ar), 7.49 (d, J = 7.8 Hz, 2H, Hm,ar),
2.2. Carbene e
5.90 (m, 1H, CH), 5.78 (m, 1H, CH), 2.75 (m, 3H, CH
(CH3)2 + CH2), 2.56–2.39 (m, 3H), 2.28–2.22 (m, 3H),
2.12–2.07 (m, 1H), 1.57 (s, 6H, C(CH3)2), 1.37 (d,
3J = 6.7 Hz, 6H, CH(CH3)2), 1.12 (d, 3J = 6.7 Hz, 6H,
CH(CH3)2). 13C{1H}NMR (CD3CN) d 192.5 (NCH),
145.4 (Co,ar), 132.7 (Cm,ar), 130.1 (Cm,ar), 128.1 (CH),
126.2 (CH), 123.0 (CH), 84.6 (NCq), 51.5 (NCHCq), 45.8
(CH2), 33.9 (CH2), 30.4 (CH2), 30.3 (CH3), 29.0 (CH),
28.5 (CH), 26.4 (CH3), 22.2 (CH3), 22.1 (CH3), 21.6
(CH2). FAB-HRMS calcd for C23H34N [M]+: m/z
324.2691; found, 324.2699. To a Schlenk tube containing
the iminium salt ec (2.95 g, 7.45 mmol) and NaBPh4
(2.55 g, 7.45 mmol) was added methylene chloride
(40 mL). The mixture was stirred for 1 h at room tempera-
ture and filtered afterwards through Celite (3 g). The sol-
vent was removed in vacuo, and the residue was
extracted two times with boiling hexanes. The hexanes
extract was cooled to À20 °C and the solution was dec-
anted from the solid. The solid was dried in vacuo to
yield 4.03 g (84%) of ec with BPhÀ4 as counteranion as
a white powder. A solution of KHMDS (250 mg,
1.26 mmol) in THF (6 mL) was added slowly to a solu-
tion of ec (BPhÀ4 ) (810 mg, 1.26 mmol) in THF (5 mL)
at À78 °C. The mixture was allowed to warm to room
temperature, and stirred for 2 h. The THF was removed
and the residue was extracted with toluene (10 + 5 mL),
and filtered. After removal of the toluene, carbene e
was isolated as colorless crystals. Yield: 265 mg (65%).
1H NMR (C6D6) d 7.35–7.18 (m, 3H, Har), 5.77 (s, 2H,
2,6-Diisopropylaniline (10.00 mL, 9.40 g, 53 mmol) was
added at room temperature to a reaction flask containing
molecular sieves (15 g) and a hexane solution (50 mL) of
1-cyclohexene-1-carboxaldehyde (90%) (7.23 mL, 7.01 g,
64 mmol). The reaction mixture was stirred for 16 h. The
molecular sieves were removed by filtration, and the hexane
was removed in vacuo. Excess 2,6-diisopropylaniline was
removed by short path distillation at 170 °C under vacuum.
The resulting oily residue was recrystallized from ethanol at
low temperatures to afford N-Dipp-C-3-cyclohexene (ea) as
1
white crystals. Yield: 11.296 g (79%). H NMR (CDCl3) d
3
7.63 (d, J = 4.5 Hz, 1H, NCH), 7.16–7.06 (m, 3H, Har),
3
5.80 (s, 2H, CH), 2.96 (sept., J = 6.9 Hz, 2H, CH(CH3)2),
2.80–2.74 (m, 1H, NCHCH), 2.36–2.30 (m, 2H, CH2),
2.26–2.21 (m, 2H, CH2), 2.15–2.06 (m, 1H, CH2), 1.82–
3
1.72 (m, 1H, CH2), 1.19 (d, J = 6.9 Hz, 12H, CH(CH3)2).
13C{1H}NMR (CDCl3) d 168.8 (NCH), 149.2 (Co,ar), 136.6
(Cm,ar), 126.7 (CH), 125.3 (CH), 123.6 (CH), 122.4 (CH),
39.7 (NCHCH), 27.5 (CH), 27.4 (CH2), 25.2 (CH2), 24.2
(CH2), 23.2 (CH3). FAB-HRMS calcd for C19H28N
[M+H]+: m/z 270.2222; found, 270.2226. A solution of ea
(8.80 g, 32.7 mmol) was added slowly to a solution of
LDA (3.67 g, 34.3 mmol) in Et2O (20 mL). The mixture
was allowed to warm to room temperature, and then stir-
red for 2 h. 3-Chloro-2-methyl-1-propene (3.55 g,
3.84 mL, 39.2 mmol) was added to this solution slowly
under stirring. After stirring for 2 h, all volatile compounds
were removed under vacuo. The remaining residue was
dried at 50 °C in vacuo to remove all traces of diethyl ether
and diisopropylamine. Hexanes (20 mL) was added and the
suspension was filtered. The solvent was evaporated to give
eb as a pale yellow oil. Yield: 7.40 g (70%). 1H NMR
(CDCl3) d 7.62 (s, 1H, NCH), 7.15–7.02 (m, 3H, Har),
5.75 (m, 2H, CH), 4.94 (s, 1H, CH), 4.80 (s, 1H, CH),
2.97 (sept., 3J = 6.9 Hz, 2H, CH(CH3)2), 2.52
(d,2J = 16.4 Hz, 1H), 2.39 (s, 2H, CH2), 2.29–2.20 (m,
3
CH), 3.84 (sept., J = 6.7 Hz, 1H, CH(CH3)2), 3.82 (sept.,
3J = 6.7 Hz, 1H, CH(CH3)2), 3.48 (td, 3J = 8.5 Hz,
3J = 7.0 Hz, 2H, CH2), 2.35–2.12 (m, 2H), 1.91 (d,
3
J = 2.5 Hz, 2H), 1.79 (t, J = 6.3 Hz, 2H, CH2), 1.40 (s,
3H, C(CH3)2), 1.38 (s, 3H, C(CH3)2), 1.25 (d,
3J = 8.6 Hz, 12H, CH(CH3)2). 13C{1H}NMR (C6D6) d
311.0, 152.7, 152.6, 139.4, 136.0, 127.5, 127.4, 127.1,
124.6, 85.9, 63.0, 55.3, 40.0, 39.8, 35.0, 29.6, 29.5, 29.1,
29.0, 27.2, 27.1, 24.6, 23.7.

G.D. Frey et al. / Journal of Organometallic Chemistry 693 (2008) 1674–1682
1679
2.3. Complex 1a
(186 mg, 0.63 mmol), complex 1c was isolated as a white
solid (189 mg, 47% yield). 1H NMR (C6D6) d 7.47 (t,
3
A THF solution (5 mL) of free carbene a (666 mg,
1.75 mmol) was added to a THF solution (5 mL) of
AuCl(SMe2) (500 mg, 1.71 mmol). The reaction mixture
was stirred for 12 h at room temperature. The solvent
was removed under vacuum, and the residue was washed
with hexane (10 mL). The residue was extracted with meth-
ylene chloride (10 mL), and the solvent was removed under
vacuum, affording complex 1a as a white solid (914 mg,
87% yield). Crystals suitable for X-ray diffraction study
were obtained by slow evaporation of a CHCl3 solution.
3J = 7.5 Hz, 1H, Har), 7.39 (d, J = 7.4 Hz, 2H, Har), 7.31
3
3
(t, J = 7.3 Hz, 2H, Har), 7.25 (d, J = 7.5 Hz, 2H, Har),
3
3.52 (d, J = 13.6 Hz, 1H, CH2), 2.92 (sept., J = 7.0 Hz,
1H, CH(CH3)2), 2.82 (d, J = 14.2 Hz, 1H, CH2), 2.79 (m,
1H, CH(CH3)2), 2.39 (d, J = 13.2 Hz, 1H, CH2), 2.36
3
(sept., J = 7.0 Hz, 1H, CH(CH3)2), 2.00 (d, J = 13.7 Hz,
3
1H, CH2), 1.57 (s, 3H, CCH3), 1.35 (d, J = 6.5 Hz, 6H,
CH(CH3)2), 1.30–1.18 (m, 15H, CH3), 1.07 (d,
3J = 6.8 Hz, 3H, CH(CH3)2). 13C{1H}NMR (C6D6) d
236.4 (Ccarbene), 147.8 (Cq), 145.7 (Cq), 145.3 (Cq), 135.5
(Cq), 131.4 (CH), 130.0 (CH), 126.4 (CH), 125.2 (CH),
125.0 (CH), 81.3 (NC(CH3)2), 60.2 (Cq), 46.1 (CH2), 44.2
(CH2), 34.3, 29.7, 29.4, 29.0, 28.6, 27.2, 26.8, 24.1, 23.9,
22.5, 22.3. FAB-HRMS (solvent CH3CN) calcd for
C30H42AuN2 [MHÀ(Cl+CH3)+CH3CN]+: m/z 627.3014;
found, 627.3015.
1
M.p. 124–125 °C. [a]D20 = 7.5 (CHCl3). H NMR (CDCl3)
d 7.42 (t, 3J = 7.1 Hz, 1H, Hp ar), 7.24 (d, 3J = 7.1 Hz, 2H,
3
Hm ar), 3.16–2.89 (m, 2H), 2.83 (sept., J = 6.3 Hz, 1H,
3
CH(CH3)2), 2.79 (sept., J = 6.3 Hz, 1H, CH(CH3)2), 2.37
(d, 3J = 13.6 Hz, 1H), 2.12–1.99 (m, 2H), 1.95–1.83 (m,
2H), 1.80–1.72 (m, 1H), 1.44 (d, 3J = 6.7 Hz, 3H,
3
CH(CH3)2), 1.39 (s, 3H, CH3), 1.37 (d, J = 7.0 Hz, 3H,
3
CH(CH3)2), 1.34 (d, J = 6.5 Hz, 3H, CH(CH3)2), 1.33 (s,
2.6. Complex 1d
3H, CH3), 1.32 (d, 3J = 7.0 Hz, 3H, CH(CH3)2), 1.30–
3
1.21 (m, 2H), 1.18 (d, J = 6.9 Hz, 3H, CH(CH3)2), 1.75–
Following the same experimental procedure as for 1a
but free carbene d (331 mg, 1.02 mmol) and AuCl(SMe2)
(294 mg, 1.00 mmol), complex 1d was isolated as a white
3
1.25 (m, 1H), 1.02 (d, J = 6.9 Hz, 3H, CH(CH3)2), 0.89
3
(d, J = 6.4 Hz, 3H, CH(CH3)2). 13C{1H}NMR (CDCl3)
1
d 237.1 (Ccarbene), 145.4 (Co,ar), 145.0 (Co,ar), 135.2 (Cm,ar),
129.8 (Cp,ar), 125.0 (Cm,ar), 124.9 (Cm,ar), 76.6 (C), 64.1 (C),
52.6 (CH2), 51.4 (CH), 49.8 (CH2), 35.6 (CH2), 30.3, 29.7,
29.7, 29.4, 29.0, 28.1, 27.5, 27.0, 25.2, 24.4 (CH2), 23.0,
22.9, 22.8, 20.2. FAB-HRMS (solvent CH3CN) calcd for
C27H43AuN Á CH3CN [MÀCl+CH3CN]+: m/z 619.3327;
found, 619.3303.
powder. Yield: 221 mg (40%). H NMR (CD3CN) d 7.51
(t, J = 7.7 Hz, 1H, Hp,ar), 7.36 (d, J = 7.7 Hz, 2H, Hm,ar),
2.85 (sept, 3J = 6.7 Hz, 2H, CH), 2.20 (s, 2H, CH2),
2.16–2.10 (m, 2H), 1.85–1.40 (m, 8H), 1.37 (s, 6H,
3
C(CH3)2), 1.35 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.32 (d,
3J = 6.7 Hz, 6H, CH(CH3)2). 13C{1H}NMR (CD3CN) d
235.0 (Ccarbene), 145.3 (Co,ar), 134.3 (Cm,ar), 129.9 (Cp,ar),
125.0 (Cm,ar), 80.7 (C), 58.6 (C), 44.4 (CH2), 36.0 (CH2),
28.7, 26.1, 25.0 (CH2), 22.0, 21.4 (CH2). FAB-HRMS (sol-
2.4. Complex 1b
vent
CH3CN)
calcd
for
C23H35AuN Á CH3CN
Following the same experimental procedure as for 1a but
free carbene b (640 mg, 1.69 mmol) and AuCl(SMe2)
(475 mg, 1.61 mmol), complex 1b was isolated as a white
solid (850 mg, 86% yield). Crystals suitable for an X-ray dif-
fraction study were obtained by slow evaporation of a
CHCl3 solution. M.p. 194–195 °C (dec.). 1H NMR (CDCl3)
[MÀCl+CH3CN]+: m/z 563.2701; found, 563.2690.
2.7. Complex 2d
Complex 1d slowly rearranges in dichloromethane
(48 h) to the dicarbene complex 2d. The dichloromethane
was removed in vacuo to give a white powder. Crystals
suitable for X-ray analysis were obtained by slow evapora-
tion of a concentrated dichloromethane solution. Yield:
1.535 g (85%, relative to carbene d). M.p. 248–252 °C. H
NMR (CD3CN) d 7.50 (dd, J = 8.4 Hz, J = 7.0 Hz, 2H,
Hp,ar), 7.39 (d, J = 7.0 Hz, 4H, Hm,ar), 2.71 (sept,
3
3
d 7.37 (t, J = 7.7 Hz, 1H, Hp,ar), 7.20 (d, J = 7.7 Hz, 2H,
H
m,ar), 4.00 (d, 2J = 12.9 Hz, 2H, CH2), 2.71 (sept.,
3J = 6.7 Hz, 2H, CH), 2.32 (s, 2H), 2.12 (s, 1H), 2.02 (s,
1H), 1.98 (s, 1H), 1.92 (s, 3H), 1.78 (m, 6H), 1.39 (d,
3J = 6.7 Hz, 6H, CH(CH3)2), 1.31 (s, 6H, C(CH3)2), 1.26
1
3
3
3
(d, J = 6.7 Hz, 6H, CH(CH3)2). 13C{1H}NMR (C6D6) d
239.9 (Ccarbene), 144.8 (Co,ar), 135.2 (Cm,ar), 129.7 (Cp,ar),
125.0 (Cm,ar), 76.9 (Cq), 63.7 (Cq), 48.5 (CH2), 39.0 (CH2),
37.0, 35.2, 34.6 (CH2), 29.2, 29.1, 27.6, 27.1, 26.9, 23.1.
FAB-HRMS (solvent CH3CN) calcd for C27H39AuN Á
CH3CN [MÀCl+CH3CN]+: m/z 615.3014; found,
615.2990.
3J = 6.7 Hz, 4H, CH), 2.10 (s, 4H, CH2), 1.63–1.52 (m,
8H), 1.37 (s, 12H, C(CH3)2), 1.31 (br s, 12 H, C(CH3)2),
1.26–1.21 (m, 24H, CH(CH3)2). 13C{1H}NMR (CD3CN)
d 252.2 (Ccarbene), 146.1 (Co,ar), 135.8 (Cm,ar), 131.1 (Cp,ar),
126.3 (Cm,ar), 82.7 (C), 60.2 (C), 45.3 (CH2), 36.3 (CH2),
29.8, 29.6, 27.3, 25.8 (CH2), 23.6, 22.2 (CH2). 13C NMR
(CD2Cl2) d 251.2 (Ccarbene), 145.0 (Co,ar), 134.6 (Cm,ar),
130.3 (Cp,ar), 125.3 (Cm,ar), 81.9 (C), 59.6 (C), 45.2
(CH2), 35.8 (CH2), 29.5, 29.0, 26.8, 25.1 (CH2), 23.9,
21.5 (CH2). FAB-HRMS calcd for C46H70AuN2 [M]+:
m/z 847.5200; found, 847.5204.
2.5. Complex 1c
Following the same experimental procedure as for 1a
but free carbene c (254 mg, 0.63 mmol) and AuCl(SMe2)

1680
G.D. Frey et al. / Journal of Organometallic Chemistry 693 (2008) 1674–1682
2.8. Complex 2e
125.4 (CH), 125.1 (CH), 125.0 (CH), 122.5 (CH), 122.4
(CH), 81.9 (NCq), 57.4 (Cq), 45.0 (CH2), 34.8 (CH2), 34.7
(CH2), 32.2 (CH2), 32.1 (CH2), 29.5 (CH3), 29.0 (CH3),
28.9 (CH), 28.8 (CH), 26.7 (CH3), 26.4 (CH3), 22.9
(CH3), 22.8 (CH3), 22.6 (CH3), 22.5 (CH3), 20.8 (CH2),
20.7 (CH2). FAB-HRMS calcd for C46H66AuN2 [M]+:
m/z 843.4891; found, 843.4891.
To a hexane solution (5 mL) of free carbene e (410 mg,
1.27 mmol) a hexane suspension (5 mL) of AuCl(SMe2)
(372 mg, 1.26 mmol) was added and stirred at room tem-
perature for 14 h. The hexane was removed by filtration
and the residue was extracted twice with 5 mL dichloro-
methane. The dichloromethane was removed in vacuo to
give a white powder. Crystals suitable for X-ray analysis
were obtained by slow evaporation of a concentrated
dichloromethane solution. Yield: 471 mg (67%). M.p.
148–152 °C (dec.). 1H NMR (CDCl3) d 7.40 (t,3J =
2.9. Crystal structure determination of compounds 1a, 1b, 2d
and 2e
The Bruker X8-APEX X-ray diffraction instrument [32]
with Mo-radiation was used for data collection. All data
frames were collected at low temperature (T = 100 K)
using an x, /-scan mode (0.3°x-scan width, hemisphere
of reflections) and integrated using a Bruker SAINTPLUS soft-
ware package [33]. Intensity data were corrected for
Lorentzian polarization. Absorption corrections were per-
formed using the SADABS program [34]. The SIR92 [35] was
used for solution. Direct methods of phase determination
followed by some subsequent difference Fourier map led
to an electron density map from which most of the non-
3
7.7 Hz, 2H, Hp,ar), 7.22 (d, J = 7.7 Hz, 4H, Hm,ar), 5.76
(m, 2H, CH), 5.63 (m, 2H, CH), 2.58 (m, 4H, CH(CH3)2),
2.50–2.38 (m, 2H), 2.18–2.03 (m, 8H), 1.94–1.78 (m, 2H),
1.73–1.57 (m, 4H), 1.39 (s, 6H, C(CH3)2), 1.34 (s, 6H,
3
C(CH3)2), 1.26 (d, J = 6.6 Hz, 6H, CH(CH3)2), 1.25 (d,
3J = 6.5 Hz, 6H, CH(CH3)2), 1.14 (d, 3J = 6.7 Hz, 4H,
CH(CH3)2), 1.02 (d, 3J = 6.6 Hz, 4H, CH(CH3)2), 0.92
3
(d, J = 6.6 Hz, 4H, CH(CH3)2). 13C{1H}NMR (CH2Cl2)
d 249.7 (Ccarbene), 144.7 (Co,ar), 144.5 (Co,ar), 133.7 (Ci,ar),
130.1 (CHp,ar), 127.0 (CH), 126.9 (CH), 125.5 (CH),
Table 2
Crystallographic data for 1a, 1b, 2d, and 2e
1a
1b Á (CHCl3)
2d Á 4(CHCl3)
2e
Formula
Fw
C
614.04
27H43AuClN
C28H40AuCl4N
729.38
C50H74AuCl13N2
1360.92
C46H66Au2Cl2N2
1111.84
Color/habit
Crystal dimensions (mm)
Crystal system
Space Group
Colorless
0.46 Â 0.40 Â 0.13
Monoclinic
P2(1)
12.361(2)
12.268(2)
21.666(4)
90.0
103.145(2)
90.0
3199.4(9)
4
Colorless
0.17 Â 0.16 Â 0.09
Orthorhombic
Pbca
Colorless
Colorless
0.43 Â 0.36 Â 0.13
0.32 Â 0.25 Â 0.17
Triclinic
Triclinic
ꢀ
ꢀ
P1
P1
˚
a (A)
15.6359(13)
16.4652(12)
22.5014(18)
90.0
90.0
90.0
10.1388(6)
12.1156(7)
12.7174(8)
71.544(3)
84.588(3)
75.268(3)
1432.95(15)
1
9.2198(4)
11.5608(5)
12.1686(5)
62.4130(10)
75.221(2)
77.4290(10)
1104.02(8)
1
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
5792.9(8)
8
Z
T (K)
100
1.275
4.693
1232
1.92–33.14
À18 6 h 6 19,
À16 6 k 6 18,
À32 6 l 6 33
39,186
100
1.673
5.466
2896
6.39–32.57
0 6 h 6 23,
À19 6 k 6 7,
À25 6 l 6 5
6504
100
1.577
3.208
1376
1.82–51.27
À21 6 h 6 20,
À23 6 k 6 25,
À27 6 l 6 27
68,429
100
1.672
6.790
1096
1.92–32.57
À13 6 h 6 13,
À17 6 k 6 16,
À18 6 l 6 10
10,679
Dcalc (g cmÀ3
)
l (mmÀ1
F(000)
h Rangea (°)
)
Index ranges (h, k, l)
Number of reflections collected
Number of independent reflections/Rint 19,291/0.0410
4742/0.0250
2828
29,275/0.0258
28,903
7327/0.0139
6929
Number of observed reflections
[I > 2r(I)]
17,952
Number of data/restraints/parameters
R1/wR2 [I > 2r(I)]a
19,291/455/560
R1 = 0.0572,
wR2 = 0.1371
R1 = 0.0615,
wR2 = 0.1387
1.194
4742/15/349
R1 = 0.0291,
wR2 = 0.0406
R1 = 0.0653,
wR2 = 0.0454
0.787
29,275/0/308
R1 = 0.0391,
wR2 = 0.1064
R1 = 0.0402,
wR2 = 0.1075
1.036
7327/0/253
R1 = 0.0352,
wR2 = 0.0924
R1 = 0.0372,
wR2 = 0.0934
1.255
R1/wR2 (all data)a
Goodness-of-fit on F2a
Largest difference in peak and hole
4.518 and À6.799
0.746 and À0.567
3.138 and À3.748
4.705 and À6.688
À3 a
˚
(e A
)
a
Because of the very large h angle, and as often observed for gold complexes, there are large electronic residuals close to gold in complexes 1a, 2d and 2e.

G.D. Frey et al. / Journal of Organometallic Chemistry 693 (2008) 1674–1682
1681
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Inc. for financial support, the Alexander von Humboldt
Foundation and the Higher Education Commission
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