N-Heterocyclic carbene transfer from gold(I) to palladium(II)

Article abstract of DOI:10.1021/om900776j

N-Heterocyclic carbene gold(I) complexes [(L)AuCl] [L = l,3-diethyl-4,5-dihydroimidazol-2-ylidene (3a); l,3-dibenzyl-4,5- dihydroimidazol-2-ylidene (3c); l,3-dipicolyl-4,5-dihydroimidazol-2-ylidene (3d); l,3-diethylimidazol-2-ylidene (5a); and l-methylthiomethyl-3- mesitylimidazol-2-ylidene (10)] react with [(PhCN)₂PdCl₂] to give the corresponding palladium complexes and the reactions are promoted by the addition of triphenylphosphine. This study demonstrates that the carbene moiety can be transferred from Au(I) to Pd(II) for the first time.

Full text of DOI:10.1021/om900776j

Organometallics 2009, 28, 6957–6962 6957
DOI: 10.1021/om900776j
N-Heterocyclic Carbene Transfer from Gold(I) to Palladium(II)
Shiuh-Tzung Liu,*,† Chun-I Lee,† Ching-Feng Fu,† Chang-Hong Chen,† Yi-Hung Liu,†
Cornelis J. Elsevier,‡ Shei-Ming Peng,† and Jwu-Ting Chen*,†
†Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, Republic of China, and
‡Van’t Hoff Institute of Molecular Sciences, University of Amsterdam, Amsterdam, The Netherlands
Received September 7, 2009
N-Heterocyclic carbene gold(I) complexes [(L)AuCl] [L = 1,3-diethyl-4,5-dihydroimidazol-2-ylidene
(3a); 1,3-dibenzyl-4,5-dihydroimidazol-2-ylidene (3c); 1,3-dipicolyl-4,5-dihydroimidazol-2-ylidene (3d);
1,3-diethylimidazol-2-ylidene (5a); and 1-methylthiomethyl-3-mesitylimidazol-2-ylidene (10)] react with
[(PhCN)2PdCl2] to give the corresponding palladium complexes, and the reactions are promoted by the
addition of triphenylphosphine. This study demonstrates that the carbene moiety can be transferred from
Au(I) to Pd(II) for the first time.
Introduction
iridium,6 nickel,5e,f,7 palladium,5a,b,8,9 platinum,5a,b,8 cop-
per,5b,7b,14 silver,5b and gold.5b,8,11,12 On the other hand,
the reaction of imidazolium salts with Ag2O provides the
corresponding Ag(I) carbenes directly, which can undergo
transmetalation with various metal ions such as Ru(II),
Ru(III), Ru(IV), Ni(II), Pd(II), Pt(II), Rh(I), Rh(III), Ir(I),
Ir(III), Cu(I), and Au(I) to generate the corresponding
carbene species.13 To the best of our knowledge, there is no
precedented report concerning carbene transfer reaction
from gold(I) to the other metal ion. Herein we describe the
first example of a procedure for the carbene transfer from
gold(I) to palladium(II).
Carbene transfer from a metal carbene complex to another
metallic center represents an interesting approach that pro-
vides pragmatic accesses for the preparation of various new
transition metal carbene complexes. Two approaches for the
cabene transfer between metal ions are frequently encoun-
tered, and their starting materials are pentacarbonylmetal
carbenes and silver carbenes, respectively.1 The first example
of a carbene ligand transfer from molybdenum to iron
complexes was reported by Fischer and Beck.2 Since then,
the carbene ligands in group VI metal carbonyl carbene
complexes have been transferred to iron,3 cobalt,4 rhodium,5
Results and Discussion
*Corresponding authors. E-mail: stliu@ntu.edu.tw; jtchen@ntu.edu.tw.
(1) (a) Nolan, S. P., Ed. N-Heterocyclic Carbenes in Synthesis; Wiley-
VCH: Weinheim, Germany, 2006. (b) Glorius, F. N-Heterocyclic Carbenes
in Transition Metal Catalysis; Springer: Berlin, 2007. (c) Liddle, S. T.;
Edworthy, I. S.; Arnold, P. L. Chem. Soc. Rev. 2007, 36, 1732. (d) K€uhl, O.
Chem. Soc. Rev. 2007, 36, 592. (e) Dragutan, V.; Dragutan, I.; Delaude, L.;
Demonceau, A. Coord. Chem. Rev. 2007, 251, 765. (f) Arnold, P. L.;
Pearson, S. Coord. Chem. Rev. 2007, 251, 596. (g) Liu, S.-T.; Reddy,
Preparation of Saturated and Unsaturated NHC Gold(I)
Complexes. Both saturated and unsaturated NHC com-
plexes of gold(I) can be prepared by carbene transfer reac-
tions either from tungsten complexes 2 or from silver
complexes 5 with [(Me2S)AuCl] (Scheme 1). The saturated
tungsten NHC complexes 2 were prepared by the direct
ꢀ
~
K. R. Chem. Soc. Rev. 1999, 315. (h) Gomez-Gallego, M.; Mancheno, M. J.;
Sierra, M. A. Acc. Chem. Res. 2005, 38, 44.
(2) Fischer, E. O.; Beck, H.-J. Angew. Chem., Int. Ed. Engl. 1970, 9,
72.
(3) Fischer, E. O.; Beck, H.-J.; Kreiter, C. G.; Lynch, J.; Muller, J.;
(8) Kessler, F.; Szesni, N.; Maass, C.; Hohberger, C.; Weibert, B.;
Fischer, H. J. Organomet. Chem. 2007, 692, 3005.
(9) (a) Sierra, M. A.; Mancheno, M. J.; Saez, E.; del Amo, J. C. J. Am.
~
ꢀ
Winkler, E. Chem. Ber. 1972, 105, 162.
ꢀ
~
(4) Jordi, L.; Moreto, J. M.; Ricart, S.; Vinas, J. M.; Mejias, M.;
~
Chem. Soc. 1998, 120, 6812. (b) Sierra, M. A.; del Amo, J. C.; Mancheno,
ꢀ
ꢀ
Molins, E. Organometallics 1992, 11, 3507.
M. J.; Gomez-Gallego, M. J. Am. Chem. Soc. 2001, 120, 6812. (c) Albeniz,
ꢀ
(5) (a) Liu, S.-T.; Hsieh, T.-Y.; Lee, G.-H.; Peng, S.-M. Organome-
tallics 1998, 17, 993. (b) Ku, R.-Z.; Huang, J.-C.; Cho, J.-Y.; Kiang, F.-M.;
Reddy, K. R.; Chen, Y.-C.; Lee, K.-J.; Lee, J.-H.; Lee, G.-H.; Peng, S.-M.;
Liu, S.-T. Organometallics 1999, 18, 2145. (c) Barluenga, J.; Vicente, R.;
A. C.; Espinet, P.; Manrique, R.; Perez-Mateo, A. Angew. Chem., Int. Ed.
2002, 41, 2363.
(10) (a) Barluenga, J.; Lopez, L. A.; Lober, O.; Tomas, M.; Garcı
Granda, S.; Alvarez-Rua, C.; Borge, J. Angew. Chem., Int. Ed. 2001, 40,
ꢀ
€
ꢀ
´
a-
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Lopez, L. A.; Rubio, E.; Tomas, M.; Alvarez-Rꢀua, C. J. Am. Chem. Soc.
3392. (b) Barluenga, J.; Barrio, P.; Vicente, R.; Lopez, L. A.; Tomas, M.
ꢀ
ꢀ
2004, 126, 470. (d) Barluenga, J.; Vicente, R.; Lopez, L. A.; Tomas, M.
J. Organomet. Chem. 2006, 691, 5642. (e) Barluenga, J.; Vicente, R.; Barrio,
J. Organomet. Chem. 2004, 689, 3793.
€
(11) Fischer, E. O.; Bock, M. J. Organomet. Chem. 1985, 287, 279.
ꢀ
ꢀ
~
ꢀ
P.; Lopez, L. A.; Tomas, M. J. Am. Chem. Soc. 2004, 126, 5974.
(f) Barluenga, J.; Vicente, R.; Barrio, P.; Lopez, L. A.; Tomas, M.; Borge,
J. J. Am. Chem. Soc. 2004, 126, 14354.
(6) (a) Chang, Y.-H.; Fu, C.-F.; Liu, Y.-H.; Peng, S.-M.; Chen, J.-T.;
Liu, S.-T. Dalton Trans 2009, 861. (b) Chang, Y.-H.; Fu, C.-F.; Liu, Y.-H.;
Peng, S.-M.; Elsevier, C. J.; Chen, J.-T.; Liu, S.-T. Dalton Trans. 2009, 6991.
(7) (a) Barluenga, J.; Barrio, P.; Lopez, L. A.; Tomas, M.; Garcı
Granda, S.; Alvarez-Rua, C. Angew. Chem., Int. Ed. 2003, 42, 3008. (b) del
Amo, J. C.; Mancheno, M. J.; Gomez-Gallego, M.; Sierra, M. A. Organome-
tallics 2004, 23, 5021.
(12) Fananas-Mastral, M.; Aznar, F. Organometallics 2009, 28, 666.
(13) (a) Lin, I. J. B.; Vasam, C. S. Coord. Chem. Rev. 2007, 251, 642.
(b) Garrison, J. C.; Youngs, W. J. Chem. Rev. 2005, 105, 3978, and
references therein. (c) Wang, H. M. J.; Lin, I. J. B. Organometallics 1998,
17, 972.
ꢀ
ꢀ
(14) (a) Lee, C. K.; Vasam, C. S.; Huang, T. W.; Wang, H. M. J.;
Yang, R. Y.; Lee, C. S.; Lin, I. J. B. Organometallics 2006, 25, 3768.
(b) De Fremont, P.; Scott, N. M.; Stevens, E. D.; Ramnial, T.; Lightbody,
O. C.; Macdonald, C. L. B.; Clyburne, J. A. C.; Abernethy, C. D.; Nolan, S. P.
Organometallics 2005, 24, 6301.
ꢀ
ꢀ
´
a-
ꢀ
ꢀ
~
ꢀ
r
2009 American Chemical Society
Published on Web 10/29/2009
pubs.acs.org/Organometallics

6958 Organometallics, Vol. 28, No. 24, 2009
Scheme 1. Preparation of Saturated NHC Gold(I) Complexes
Liu et al.
alkylation of 1 with the corresponding alkyl halide in the
presence of sodium hydride.5b In particular, reaction of 1
with 2-picolyl chloride in the presence of sodium hydride
under refluxing conditions yielded 2d as yellow solids. The
isolated complexes 2a-c have similar spectral data to those
reported previously.5b Complex 2d is an air-stable, yellow
solid. The 13C NMR signal for the carbene carbon atom of 2d
(213.9 ppm) is located in the characteristic range reported for
other analogous metal-NHC complexes, whereas the 1H
NMR spectrum exhibits the 6H-pyridinyl proton signal at
9.15 ppm (coordination shift = 0.6 ppm), indicating the
coordination of the pyridinyl-nitrogen to the tungsten atom.
The carbonyl stretching wavenumbers of 2d occur in the
range 2000-1800 cm-1, which is in accord with a tetracar-
bonyl species. These spectral data conclude that the pyridi-
nyl-carbene ligand behaves as bidentate, not tridentate in 2d.
Carbene transfer from tungsten to gold(I) has been re-
ported by Fischer and Bock in the reaction of [(CO)5Wd
C(R0)NR2] with HAuCl4.11 In an early work, we have also
demonstrated that reactions of [(NHC)W(CO)5] with
[(Me2S)AuCl] could provide biscarbene gold(I) complexes
[{(NHC)2Au}Cl]. With a similar procedure, the gold(I)
carbene complexes 3a-d are formed directly via the reaction
of 2a-d with 1 equiv of [(Me2S)AuCl] (Scheme 1). Typically,
a mixture of 2a and an equal molar amount of [(Me2S)AuCl]
in CH2Cl2 in dichloromethane at room temperature under
ambient conditions readily caused a color change to deep
green, indicating the formation tungsten clusters.5b The
desired Au(I) carbene complexes were isolated as white solids
after chromatographic purification.
The transmetalation route using a NHC-silver complex
has proved to be useful in the preparation of a variety of
unsaturated NHC complexes.13 In this study, we employed
this method to prepare the unsaturated NHC gold species as
depicted in Scheme 2. First, reaction of the imidazolium salts
4a,b with an excess of Ag2O in dichloromethane afforded the
corresponding NHC-silver complexes 5a,b. The NMR spec-
tral data of 5a,b are essentially similar to those reported in
the literature.14 Successive reaction of 5a,b with [(Me2S)-
AuCl] in dichloromethane at room temperature provided 6a,
b in excellent yields. Furthermore, the unsymmetric carbene
gold complex was prepared by a similar route (Scheme 3).
Thus, reaction of the mesityl-substituted imidazole 7 with
R-chlorodimethyl sulfide provided the imidazolium salt 8,
which was subsequently reacted with silver oxide to yield the
silver carbene complex 9. A similar procedure was employed
for the reaction of 9 with [(Me2S)AuCl] to yield the desired
gold complex 10.
Scheme 2. Preparation of Unsaturated NHC Gold(I) Complexes
suggest the formulation of these complexes to be [(NHC)AuCl].
Indeed, the characteristic downfield signal for the coordinated
carbene carbon atom is in the region 191-194 ppm for 2a-d
and 169-176 ppm for 5a,b (Table 1), which are typical values
for gold NHC complexes.5b,15 The coordination of chloride
toward the metal center is evidenced by the infrared absorption
at 330-345 cm-1, which is characteristic for the stretching
frequency of Au-Cl (Table 1).16
Carbene Transfer from Au(I) to Pd(II). Initially, attempts
on the carbene transfer reactions of 3a with [(COD)PdCl2] or
[(Ph3P)2PdCl2] were investigated, but failed. In both instances,
the reactions did not proceed at all; the gold carbene complex
was recovered. However, reaction of 3a with 1.5 molar equiv of
[(C6H5CN)2PdCl2] in CH2Cl2 at ambient temperature went
smoothly to yield 11a in 35% isolated yield, which was proved
to be a chloride-bridged dinuclear palladium carbene complex,
and some other unidentified species. When the reaction was
carried out in the presence of 1 molar equiv of PPh3, the
complex 11a could be collected as the sole product, which can
be characterized by NMR determination.5a The formulation of
11a was confirmed by both 1H and 13C NMR observation.5a
However, the addition of an excess of phosphine may hinder
the carbene transfer, presumably due to the competitive for-
mation of [(Ph3P)2PdCl2]. In this context it is worth mentioning
that the presence of phoshine in the reaction of 3a and
[(PhCN)2PdCl2] does not provide the formation of any phos-
hine-substituted carbene palladium species such as 12. How-
ever, the coordination of triphenylphosphine toward Au(I),
yielding [(Ph3P)AuCl], and the formation of 11a were acheived
(eq 1). To our best knowledge, this observation demonstrates
the first example of carbene transfer from Au(I) to Pd(II).
To test the generality of such a unique carbene transfer,
other gold(I) carbene complexes, 3b-d, 5a,b, and 10, were
also studied. Similar to 3a, reactions of 3c or 3d with
All gold carbene complexes in this work are white solids.
Conductivity measurement of gold carbene complexes in di-
chloromethane shows that these complexes are essentially none-
lectrolytic. In addition, mass spectra indicate that one carbene
moiety is coordinated to the metal center. These observations
(15) De Fremont, P.; Scott, N. M.; Stevens, E. D.; Nolan, S. P.
Organometallics 2005, 24, 2411.
(16) Ieda, H.; Fujiwara, H.; Fuchita, Y. Inorg. Chim. Acta 2001, 319,
203.

Article
Organometallics, Vol. 28, No. 24, 2009 6959
Scheme 3. Preparation of Unsymmetric NHC Gold(I) Complexes
Table 1. Selected Spectral Data of Gold(I) Complexesa
carbene transfer reaction from 10 to Pd(II) went smoothly to
yield the (C,S)-chelation complex 15. Complex 15 can also be
prepared by a typical procedure via the carbene transfer from
Ag(I) to Pd(II). Thus, reaction of 9 with [(COD)PdCl2]
yielded 15 in 70% isolated yield.
1H NMR
-N-CHn-CHn-N-
13C NMR
C(NHC)-Au
IR ν(Au-Cl)
(cm-1 b
complex
)
3a
3b
3c
3d
5a
5b
10
3.62
3.61
3.45
3.67
6.95
7.15
7.41 and 6.93
191.6
192.8
192.3
193.7
169.5
175.5
172.1
332
335
330
331
331
341
338
a NMR in CDCl3. ppm. b CsI.
(PhCN)2PdCl2 in the presence of 1 equiv of PPh3 in CH2Cl2
provided 11c and 13a, respectively. Complex 11c is a known
species and was characterized by 1H and 13C NMR spectro-
scopies.5a The 1H NMR spectrum of 13a exhibits the
6H-pyridinyl proton signal at δ 9.40 (coordination shift =
0.9 ppm), indicating the coordination of the pyridinyl-nitro-
gen to the palladium atom. The proton spectrum of 13a also
showed only one set of signals (δ 5.09) for the methylene
units in the bridging pyridinyl and imidazole rings, support-
ing the presence of equivalent pyridinyl groups on the
molecule, as expected for a structure in which the carbene
ligand forms a pincer-type complex with palladium. Mass
spectrometry also supported the proposed structure. Elec-
trospray MS gave a clear ion at m/z 393.0 Da, which
corresponds to the formula [(carbene)Pd35Cl]þ. Further
confirmation of the formulation comes from the crystal
structure of its hexafluorophosphate salt 13b, which was
obtained via the anion metathesis. It should be noted that
another synthetic approach leading to 13a can be achieved by
the direct transfer reaction of 2d with [(COD)2PdCl2], i.e., the
carbene transfer from tungsten to palladium.
Crystallography. For the pincer-type complex, yellow
crystals of 13b were subsequently isolated, which proved
suitable for X-ray crystallography. The ORTEP plot (Figure
1) shows the palladium atom with slightly distorted square-
planar coordination bonded to carbene and two pyridinyl
nitrogen donors. The metallacycles are strongly puckered, as
evidenced by the dihedral angles N(1)-C(1)-Pd(1)-N(4)
(31.7°) and N(2)-C(1)-Pd(1)-N(3) (29.1°). These compare
well to those observed in related pincer Pd(II) carbene
complexes. The Pd-C(carbene) bond length is 1.936(2) A,
which is normal for Pd-C(carbene) bonds. Selected bond
lengths and angles are given in Table 2, and all are in the
expected range.
Complex 15 was isolated as light yellow crystals, and
X-ray crystal structure confirms the formation of a (C,S)-
chelation complex (Figure 2). Selected bond distances and
angles are shown in Table 3. Complex 15 adopts a slightly
distorted square geometry around the palladium atom,
where the carbene carbon [C(3)] and the sulfur donor [S(1)]
constitute a five-membered ring with the metal atom. The
resulting bite angle is 84.99(6)o. All bond lengths and angles
of 15 are in the normal range as compared with those of the
related species. The different trans influence of carbene vs
sulfur donors is shown by the difference in the Pd-Cl bond
ꢀ
distances [2.3033(6) vs 2.3456(6) A].
Summary
In contrast with these cases, the analogous reaction of 3b
gave complicated mixtures of palladium black and other
unidentified species. It appears that reaction of 11b with
Pd(II) may undergo other reaction pathways.
Besides the saturated NHC complexes, gold complexes
with an unsaturated carbene moiety are also investigated.
Like complex 3a, the NHC ligand on complex 6a readily
transfers to the palladium to yield 14 in 73% yield, but
complex 6b remains intact. Presumably, the steric bulkiness
of the substituents on the NHC hinders the transformation.
Another example of this kind of transformation is illustrated
with complex 10. With a NHC bearing a thioether donor,
In this work, we discover that gold(I) complexes with
N-heterocyclic carbenes [(L)AuCl] can transfer NHC to
[(PhCN)2PdCl2] to generate NHC palladium complexes with
the promotion of triphenylphosphine. Although palladium
carbene complexes can be obtained via several approaches, a
carbene moiety transfer from Au(I) to Pd(II) leading to the
formation of palladium carbene complexes is unprece-
dented. Further utilization of this type of carbene complexes
and kinetics for the carbene transfer reactions are under
investigation.

6960 Organometallics, Vol. 28, No. 24, 2009
Liu et al.
Figure 2. ORTEP plot of 15 (drawn with 30% probability
ellipsoids; labels for the phenyl group are omitted for clarity).
ꢀ
˚
Table 3. Selected Bond Distances (A) and Bond Angles (deg)
Figure 1. ORTEP plot of the cationic portion of 13b (drawn
with 30% probability ellipsoids; labels for the pyridinyl rings are
omitted for clarity).
Pd(1)-C(3)
1.977(2)
2.3033(6)
1.351(3)
1.442(3)
84.99(6)
176.95(2)
104.6(2)
Pd(1)-S(1)
2.2640(6)
2.3456(6)
1.344(3)
1.330(3)
95.99(6)
171.02(6)
111.6(2)
Pd(1)-Cl(1)
Pd(1)-Cl(2)
N(1)-C(3)
N(2)-C(3)
N(1)-C(2)
C(4)-C(5)
C(3)-Pd(1)-S(1)
S(1)-Pd(1)-Cl(1)
N(2)-C(3)-N(1)
C(3)-Pd(1)-Cl(1)
C(3)-Pd(1)-Cl(2)
C(3)-N(1)-C(5)
ꢀ
˚
Table 2. Selected Bond Distances (A) and Bond Angles (deg)
Pd(1)-C(1)
Pd(1)-Cl(1)
Pd(1)-N(3)
Pd(1)-N(4)
C(1)-N(1)
C(1)-N(2)
C(2)-C(3)
1.936(2)
2.3688(5)
2.066(2)
2.054(2)
1.321(3)
1.313(3)
1.523(3)
N(4)-Pd(1)-N(3)
C(1)-Pd(1)-Cl(1)
C(1)-Pd(1)-N(4)
C(1)-Pd(1)-N(3)
Pd(1)-C(1)-N(1)
Pd(1)-C(1)-N(2)
174.92(6)
176.78(6)
87.15(8)
87.87(8)
123.9(2)
124.7(2)
portions were dried and concentrated. The residue was dissolved
in dichloromethane. By addition of hexane, the desired complex
precipitated out as yellow solids (0.43 g, 66%). 1H NMR
(DMSO-d6, 400 MHz): δ 8.98 (m, 1H, Py-H), 8.51 (m, 1H,
Py-H), 7.99 (m, 1H, Py-H), 7.78 (m, 1H, Py-H), 7.72 (m, 1H, Py-
H), 7.33 (m, 1H, Py-H), 7.26-7.29 (m, 2H, Py-H), 4.99 (s, 2H,
-NCH2-Py), 4.70 (s, 2H, -NCH2-Py), 3.81-3.86 (m, 2H, imi-
H), 3.52-3.57 (m, 2H, imi-H). 13C NMR (DMSO-d6, 100.6
MHz): δ 218.8, 213.9, 213.5 (trans-CO, WdC and axial-CO),
203.2 (cis-CO), 158.0, 156.9, 156.6, 149.2, 139.1, 136.9, 125.4,
123.9, 122.4, 121.2, 55.6, 55.2, 51.3, 49.1. IR (KBr, νCO): 1992,
1862, 1811 cm-1. ESI-MS: calcd for (M þ H)þ C19H17N4O4W
m/z = 549.1, found 549.1. Anal. Calcd for C19H16N4O4W: C,
41.63; H, 2.94; N, 10.22. Found: C, 41.61; H, 3.31; N, 10.05.
Complex 3a. To a solution of 2a (149.8 mg, 0.33 mmol) in
CH2Cl2 (1 mL) was added a dichloromethane solution (5 mL) of
[(Me2S)AuCl] (108 mg, 0.36 mmol). The resulting mixture was
stirred at room temperature for 10 min, and the solution turned
a dark green color. The reaction mixture was concentrated and
the residue was chromatographed on silica gel (15 g) with the
elution of ethyl acetate/hexane (1:1). The fraction of the desired
product was collected and concentrated to yield 3a as white
solids (85.6 mg, 72%). IR: 332 cm-1 (Au-Cl). ΛM (1.0 ꢀ 10-3
mol dm-3, dichloromethane): 8 Ω cm2 mol-1. 1H NMR (CDCl3,
400 MHz): δ 3.66 (q, J = 7.2 Hz, 4H, -CH2CH3), 3.62 (s, 4H,
imi-H), 1.19 (t, J=7.2 Hz, 6H, -CH2CH3). 13C NMR (CDCl3,
100 MHz): δ 191.6 (AudC), 47.8, 45.4, 13.6. Anal. Calcd for
C7H14AuClN2: C, 23.44; H, 3.93; N, 7.81. Found: C, 23.81; H,
4.23; N, 7.57.
Experimental Section
General Information. All reactions, manipulations, and pur-
ification steps were performed under a dry nitrogen atmosphere.
Tetrahydrofuran was distilled under nitrogen from sodium
benzophenone ketyl. Dichloromethane and acetonitrile were
dried over CaH2 and distilled under nitrogen. Other chemicals
and solvents were of analytical grade and were used after a
degassing process. Tungsten carbene complex 1, 2a-c, 5a,b, and
1-mesitylimidazole were prepared according to the method
reported previously.5a,14,17
Nuclear magnetic resonance spectra were recorded in CDCl3
on a Bruker AVANCE 400 spectrometer. Chemical shifts are
given in parts per million relative to Me4Si for 1H and 13C NMR
and relative to 85% H3PO4 for 31P NMR. Infrared spectra were
measured on a Bomem DA 8.3 spectrometer as CsI pallets.
Conductivity measurements were carried out at 25 °C on a YSI
model 32 conductance meter.
Complex 2d. A mixture of sodium hydride (prewashed with
hexane 10 mL ꢀ 2) (25 mmol) and 1 (0.5 g, 1.27 mmol) in
anhydrous THF (20 mL) was stirred at room temperature for
8 h. 2-Picolyl chloride (0.86 g, 6.7 mmol) in THF was added to
the above solution and then heated to reflux overnight. Upon
cooling, the excess of NaH was slowly quenched by water and
the organic portion was separated. The aqueous layer was
extracted with dichloromethane (20 mL). The combined organic
Complex 3b. The preparation procedure is similar to that
for 2a: white powders (78%). IR: 335 cm-1 (Au-Cl). ΛM
(1.0 ꢀ 10-3 mol dm-3, dichloromethane): 8 Ω cm2 mol-1
.
1H NMR (CDCl3, 400 MHz): δ 5.80 (m, 2H, -CH2-CHdCH2),
5.26 (d, J=14 Hz, 4H, -CH2-CHdCH2), 4.25 (d, J=6 Hz, 4H,
(17) Johnson, A. L.; Kauer, J. C.; Sharma, D. C.; Dorfman, R. I.
J. Med. Chem. 1969, 12, 1024.

Article
Organometallics, Vol. 28, No. 24, 2009 6961
-CH2-CHdCH2), 3.61 (s, 4H, imi-H). 13C NMR (CDCl3,
100 MHz): δ 192.8 (AudC), 131.9, 119.5, 53.3, 48.2. Anal.
Calcd for C9H14AuClN2: C, 28.25; H, 3.69; N, 7.32. Found:
C, 28.56; H, 4.00; N, 7.26.
Complex 3c. The preparation procedure is similar to that for
2a: white solids (65%). IR: 330 cm-1 (Au-Cl). 1H NMR
(CDCl3, 400 MHz): δ 7.42-7.28 (m, 10H, Ar-H), 4.85 (s, 4H,
-CH2Ph), 3.45 (s, 4H, imi-H). 13C NMR (CDCl3, 100 MHz): δ
192.3 (AudC), 134.6, 128.9, 128.4, 128.1, 54.7, 48.0. Anal. Calcd
for C17H18AuClN2: C, 42.29; H, 3.76; N, 5.80. Found: C, 42.67;
H, 4.18; N, 5.63.
filtrate was chromatographed on silica gel with elution of ethyl
acetate. Upon concentration, complex 10 was obtained as
white solids (113 mg, 87%). IR: 338 cm-1 (Au-Cl). 1H NMR
(400 MHz CDCl3): δ 7.41 (d, J=2 Hz, 1H, imi-H), 6.94 (s, 2H,
Ar-H), 6.93 (d, J=2 Hz, 1H, imi-H), 5.35 (s, 2H, -CH2-), 2.31
(s, 3H, p-Ar-Me), 2.19 (s, 3H, -SCH3), 2.00 (s, 6H, o-Ar-Me).
13C NMR (400 MHz CDCl3): δ 172.1 (Au-C), 139.8, 134.6,
134.3, 129.4, 123.3, 119.6, 53.9, 21.2, 17.9, 14.4. Anal. Calcd for
C14H18AuClN2S: C, 35.12; H, 3.79; N, 5.85. Found: C, 34.89; H,
3.82; N, 5.59.
1
Complex 11a. H NMR (CDCl3, 300 MHz): δ 4.22 (q, J =
Complex 3d. The preparation procedure is similar to that for
2a: white solids (23%). IR: 331 cm-1 (Au-Cl). ΛM (1.0 ꢀ 10-3
mol dm-3, dichloromethane): 4 Ω cm2 mol-1. 1H NMR (CDCl3,
400 MHz): δ 8.50 (d, 2H, Py-H, J=4.4 Hz), 7.66 (t, 2H, -Py, J=
7.6 Hz), 7.43 (d, 2H, Py-H, J = 7.6 Hz), 7.20 (t, 2H, Py-H, J =
4.4 Hz), 4.93 (s, 4H, -CH2Py), 3.67 (s, 4H, imi-H). 13C NMR
(CDCl3, 100 MHz): δ 193.7 (AudC), 155.0, 149.5, 137.2, 123.0,
122.4, 56.0, 49.1. Anal. Calcd for C15H16AuClN4: C, 37.17; H,
3.33; N, 11.56. Found: C, 37.42; H, 3.01; N, 11.48.
7.3 Hz, 8H, -CH2-), 3.63 (s, 8H, imi-H), 1.37 (t, J =7.3 Hz,
12H, -CH3). These spectral data are consistent with the litera-
ture data.5a,b
Complex 11c. 1H NMR (CDCl3, 300 MHz): δ 7.46-7.50 (m,
8H, Ar-H), 7.36-7.28 (m, 12H, Ar-H), 5.41 (s, 8H, -CH2Ph),
3.37 (s, 8H, imi-H). These spectral data are consistent with the
literature data.5a,b
Complex 13a. Method A. A mixture of 2d (30 mg, 5.5 ꢀ 10-2
mmol) and [(COD)PdCl2] (23.4 mg, 8.2 ꢀ 10-2 mmol) in CH2Cl2
(8 mL) was stirred at room temperature for 2 h. The reaction
mixture was passed through Celite (2 g) to remove tungsten
species, and the filtrate was concentrated. The residue was
recrystallized in CH2Cl2/ether to yield yellow crystalline solids
(13 mg, 55%).
Complex 6a. A solution of 5a (148 mg, 0.47 mmol) in dichloro-
methane (1 mL) was added to a solution of [(Me2S)AuCl]
(153.7 mg, 0.47 mmol) in dichloromethane (5 mL), and the
resulting mixture was stirred at room temperature for 2 h. After
filtration of silver salts and concentration of the filtrate, the
residue was chromatographed on silica gel with elution of
ethyl acetate. The desired complex was obtained as white solids
Method B. A mixture of 3d (10 mg, 2 ꢀ 10-2 mmol) and
[(PhCN)2PdCl2] (12 mg, 3 ꢀ 10-2 mmol) in CH2Cl2 was stirred
at 40 °C for 6 h. The reaction mixture was concentrated and
chromatographed on silica gel with elution of hexane/ethyl
acetate. A yellow band from the column was collected and
(155.9 mg, 92%). IR: 331 cm-1 (Au-Cl). ΛM (1.0ꢀ 10-3 mol dm-3
,
dichloromethane): 6 Ω cm2 mol-1. 1H NMR(CDCl3, 400 MHz): δ
6.95 (s, 2H, -imi-H), 4.18 (q, J=7 Hz, 4H, CH3CH2-), 1.43 (t, J=
7 Hz, 6H, CH3CH2-). 13C NMR (CDCl3, 100 MHz): δ 169.5
(AudC), 119.9, 46.4, 16.4. Anal. Calcd for C7H12AuClN2: C,
23.58; H, 3.39; N, 7.86. Found: C, 23.68; H, 3.60; N, 7.22.
Complex 6b. The preparation procedure is similar to that for
5a: white solid (86%). IR: 341 cm-1 (Au-Cl). ΛM (1.0 ꢀ 10-3
mol dm-3, dichloromethane): 5 Ω cm2 mol-1. 1H NMR (CDCl3,
400 MHz): δ 7.48 (t, J=7.8 Hz, 2H, Ar-H), 7.26 (d, J=7.8 Hz,
2H, Ar-H),7.15 (s, 2H, imi-H), 2.54 (m, 4H, -CH), 1.32 (d, J=
7 Hz, 6H, -CH3), 1.19 (d, J = 7 Hz, 6H, -CH3). 13C NMR
(CDCl3, 100 MHz): δ 175.5 (AudC), 145.6, 134.0, 130.7, 124.3,
123.1, 28.8, 24.4, 24.0. Anal. Calcd for C27H36AuClN2: C, 52.22;
H, 5.84; N, 4.51. Found: C, 52.12; H, 6.02; N, 4.10.
1
concentrated to give 13a as yellow solids (6.2 mg). H NMR
(CDCl3, 400 MHz): δ 9.40 (d, J=6 Hz, 2H, Py-H), 7.97 (dd, J=
8, 6 Hz, 2H, Py-H), 7.87 (d, J=8 Hz, 2H, Py-H), 7.42 (dd, J=8,
6 Hz, 2H, Py-H), 5.09 (s, 4H, -CH2Py), 4.33 (s, 4H, imi-H). 13
C
NMR (CDCl3, 100 MHz): δ 178.2 (MdC), 155.9, 153.6, 140.7,
126.3, 124.8, 52.9, 51.9. HR-ESI-MS calcd for C15H16-
N435Cl106Pd [M - Cl] m/z = 393.0096, found 393.0097. ΛM
(1.0 ꢀ 10-3 mol dm-3, CH3OH): 63 S cm2 mol-1. Anal. Calcd
for C15H16Cl2N4Pd: C, 41.93; H, 3.75; N, 13.04. Found: C,
41.73; H, 3.85; N, 13.25.
Complex 13b. To a solution of 13a was added an excess of
KPF6 in CH3CN. Upon stirring at room temperature for 2 h, the
solvent was removed and the residue was extracted with
CH2Cl2/H2O. The organic extract was dried and concentrated.
Upon recrystallization from CH2Cl2/ether, the desired complex
Compound 8. A mixture of imidazole 7 (0.5 g, 2.7 mmol) and
chloromethyl methyl sulfide (1.15 g, 12 mmol) in anhydrous
THF (10 mL) was heated to reflux for 24 h. Yellowish solids
were collected and redissolved in CH2Cl2. Addition of ether to
the solution gave 8 as white precipitates (0.7 g, 91%). 1H NMR
(CDCl3, 400 MHz): δ 11.02 (s, 1H, im-H), 7.76 (s, 1H, im-H),
7.15 (s, 1H,im-H), 7.00 (s, 2H, Ar-H), 5.94 (s, 2H, -CH2-), 2.33
(s, 3H, p-Ar-Me), 2.30 (s, 3H, -SCH3), 2.07(s, 6H, o-Ar-Me).
13C NMR (CDCl3, 100 MHz): δ 140.2, 137.1, 133.2, 129.9,
128.9, 123.0, 122.7, 51.8, 20.2, 16.7, 13.6. Anal. Calcd for
C14H19ClN2S: C, 59.45; H, 6.77; N, 9.90. Found: C, 59.25; H,
6.62; N, 10.11.
1
13b was obtained as yellow crystalline solids (73%). H NMR
(CDCl3, 400 MHz): δ 9.42 (d, J=6 Hz, 2 H, Py-H), 7.97 (t, J=
7.8 Hz, 2H, Py-H), 7.62 (d, J =7.8 Hz, 2H, Py-H), 7.43 (t, J =
6 Hz, 2H, Py-H), 4.80 (s, 4H, CH2-Py), 4.12 (s, 4H, imi-H). 13
C
NMR (CDCl3, 100.6 MHz): δ 178.2 (MdC), 155.9, 153.6, 140.7,
126.3, 124.8, 52.9, 51.9. 31P{1H} NMR (CDCl3, 162 MHz): δ
-144.0 (sept, PF6, JFP = 712.8 Hz). Anal. Calcd for C15H16-
ClF6N4PPd: C, 33.42; H, 2.99; N, 10.39. Found: C, 33.28; H,
2.89; N, 10.18.
Complex 9. A mixture of 8 (0.1 g, 0.36 mmol) and Ag2O
(0.1 g, 0.43 mmol) in CH3CN (10 mL) was stirred at room
temperature in the dark for 24 h. The reaction mixture was
filtered, and the solvent was removed under vacuum to give the
crude product, which was washed with ether to give complex 9 as
a gray-white solid (79 mg, 56%). 1H NMR (CDCl3, 300 MHz):
δ 7.43 (s, 1H, imi-H), 7.00 (s, 1H, imi-H), 6.94 (s, 2H, Ar-H), 5.23
(s, 2H, -CH2-), 2.32 (s, 3H, p-Ar-Me), 2.10 (s, 3H, -SCH3),
1.95 (s, 6H, o-Ar-Me). 13C NMR (CDCl3, 100 MHz): δ 180.8,
139.0, 134.9, 134.2, 128.9, 123.0, 121.1, 54.1, 20.1, 17.2, 13.7.
Anal. Calcd for C14H18AgClN2S: C, 43.15; H, 4.66; N, 7.19.
Found: C, 42.95; H, 4.75; N, 7.38.
Complex 14. The procedure is similar to that for 5a (method
B) (61%). 1H NMR (CDCl3, 400 MHz): δ 6.91 (s, 4H, imi-H),
4.67 (q, J=7 Hz, 8H, -CH2-), 1.63 (t, J=7 Hz, 12H, -CH3).
13C NMR (CDCl3, 100.6 MHz): δ 139.8 (MdC), 121.5, 46.1,
16.1. Anal. Calcd for C14H24Cl4N4Pd2: C, 27.88; H, 4.01; N,
9.29. Found: C, 27.68; H, 4.12; N, 9.08.
Complex 15. Method A (transfer from Ag-carbene). A mixture
of 9 (31.2 mg, 0.08 mmol) and [Pd(COD)Cl2] (23 mg, 0.08 mmol)
in CH2Cl2 (3 mL) was stirred at room temperature in the dark
for 24 h. The reaction mixture was filtered through Celite, and
the filtrate was concentrated. The residue was washed with ether
(2 mL ꢀ 2) to give 15 as light yellow solids (25 mg, 73%).
Method B. The procedure is similar to that for 5a (method B)
(70% isolated yield). 1H NMR (400 MHz, CD3CN): δ 7.48 (s,
1H), 6.96 (m, 3H), 5.26 (d, 1H, J = 12.7 Hz), 4.95 (d, 1H, J =
12.7 Hz), 2.67 (s, 3H), 2.32 (s, 1H), 2.08 (s, 1H), 2.03 (s, 1H).
Complex 10. A mixture of 9 (105.9 mg, 0.27 mmol) and
[Me2SAuCl] (79.0 mg, 0.27 mmol) in anhydrous dichloro-
methane (10 mL) was stirred at room temperature under a
nitrogen atmosphere for 4 h. After filtration of silver salts, the

6962 Organometallics, Vol. 28, No. 24, 2009
Liu et al.
Anal. Calcd for C14H19Cl2N2PdS: C, 39.69; H, 4.28; N, 6.61.
Found: C, 39.49; H, 4.32; N, 6.61.
data for 15: C14H18Cl2N2PdS, Mw=423.66, monoclinic, P21/n,
a = 8.0299(2) A, b = 17.8932(3) A, c = 12.3472(3) A, β =
108.238(2)°, V = 1684.93(7) A3, Z = 4, Dcalcd = 1.670 Mg/m3,
F(000)=848, 0.25 ꢀ 0.15 ꢀ 0.10 mm3, 2θ=2.86-27.50°, 20 043
reflns collected, 3855 independent reflns [R(int)=0.0345], full-
matrix least-squares on F2, R1 = 0.0233, wR2 = 0.0583 [I >
2σ(I)], goodness of fit on F2 1.039. Other crystallographic data
are deposited as Supporting Information.
Crystallography. Crystals suitable for X-ray determination
were obtained for 13b and 15 by recrystallization at room
temperature. Cell parameters were determined by a Siemens
SMART CCD diffractometer. The structure was solved using
the SHELXS-97 program18 and refined using the SHELXL-97
program19 by full-matrix least-squares on F2 values. Crystal
data for 13b: C15H16ClF6N4PPd, Mw=539.14, triclinic, P1, a=
8.8533(2) A, b=10.3000(2) A, c=11.7433(3) A, R=69.643(2)°,
Acknowledgment. We thank the National Science
Council (NSC97-2113-M-002-013-MY3) and the NSC-
NWO Project for their financial support.
β=84.810(2)°, γ=67.415(2)°, V=925.83(4) A3, Z=2, Dcalcd
=
1.934 Mg/m3, F(000) = 532, 0.20 ꢀ 0.15 ꢀ 0.10 mm3, 2θ =
3.18-27.50°, 21 207 reflns collected, 4245 independent reflns
[R(int) = 0.0233], full-matrix least-squares on F2, R1 = 0.0236,
wR2 = 0.0833 [I > 2σ(I)], goodness of fit on F2 0.775. Crystal
Supporting Information Available: Tables providing atomic
positional parameters, bond distances and angles, anisotropic
thermal parameters, and calculated hydrogen atom positions
for complexes 13b and 15. A CIF file is also available. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(18) Sheldrick, G. M.SHELXS-97. Acta Crystallogr., Sect. A: Found.
Crystallogr. 1990, 46, 467
€
SHELXL-97; University of Gottingen:
(19) Sheldrick, G. M.
€
Gottingen, Germany, 1997.