Benzothiazolin-2-ylidene and azole mixed-ligand complexes of palladium

Article abstract of DOI:10.1002/ejic.200900447

A series of mixed-ligand, mononuclear complexes trans[PdX ₂(NSHC)(azole)] [NSHC = N,S-heterocyclic carbene; azole = imidazole, l-(2,4,6-trimethylphenyl)-1H-imidazole, benzimidazole, benzothiazole and benzoxazole] have been prepared and characterised by X-ray single-crystal diffrac-tion. These complexes catalyse the sp²-sp³ cross-coupling of fluoroaryl halides with arylboronic acid to give diarylmethanes with good yields and high turnovers, Wiley-VCH Verlag GmbH & Co. KGaA.

Full text of DOI:10.1002/ejic.200900447

FULL PAPER
DOI: 10.1002/ejic.200900447
Benzothiazolin-2-ylidene and Azole Mixed-Ligand Complexes of Palladium
Swee Kuan Yen,[a] Lip Lin Koh,[a] Han Vinh Huynh,[a] and T. S. Andy Hor*[a]
Dedicated to commemorate the 80th anniversary of chemistry research and education in Singapore
Keywords: Palladium / N,S ligands / Nitrogen heterocycles / Cross-coupling / Carbene ligands
A series of mixed-ligand, mononuclear complexes trans-
[PdX2(NSHC)(azole)] [NSHC = N,S-heterocyclic carbene;
azole = imidazole, 1-(2,4,6-trimethylphenyl)-1H-imidazole,
benzimidazole, benzothiazole and benzoxazole] have been
prepared and characterised by X-ray single-crystal diffrac-
tion. These complexes catalyse the sp2–sp3 cross-coupling of
fluoroaryl halides with arylboronic acid to give diarylmeth-
anes with good yields and high turnovers.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
potential of this type of complexes by describing their sp2–
sp3 cross-coupling activities with benzylic halides and an
organoboronic acid to give pharmacologically active diaryl-
methanes.[9] This type of reaction is known to be catalysed
by Pd complexes of phosphanes[10] and mixed oxides,[11]
palladacycles[12,13] and NHC[14] complexes of Pd but is not
known for NSHC complexes. A broad range of polyfunc-
tionalized benzylzinc reagents also undergo smooth cross-
coupling reactions catalyzed by Ni(acac)2 and PPh3.[15]
Introduction
The development of N-heterocyclic carbene complexes
and their catalytic applications is a vibrant area of current
research.[1] Our recent isolation of dinuclear benzothiazole-
based carbene complexes[2] has provided a ready access to
a range of hybrid carbene complexes. The introduction of
a second ligand with a different nature at the metal core
could present a synthetically convenient strategy for tuning
the electronic and steric properties of the coordination
sphere. This approach is appealing as many of these com-
plexes are catalytically active, although their efficacies often
depend strongly on the electronic and steric state of the
metal atom and hence the ligands it carries. We shall de-
velop this idea further herein by preparing a range of N,S-
heterocyclic carbene (NSHC) complexes[2–4] containing an
azole as the second ligand (A–D in Figure 1). These azoles
are inexpensive commercial reagents, which, despite having
similar structural motifs to the thiazole-based carbene, are
fundamentally different as they are sp2-hybridised N-do-
nors whose strength varies with the heteroatom in the ring.
Mixed carbene/azole complexes are rare in the literature,
although one reported example concerns a Sonogashira-
active carbomoyl-substituted NHC-(3-methyl-1H-imid-
azole)palladium(II) complex.[5] To the best of our knowl-
edge, no NSHC analogue is known. Azole complexes, such
as the catalytically active imidazole,[6] imidazoline[7] and
benzoxazole[8] complexes of Cu, Ir, Ru and Pd, are, how-
ever, more common. Herein we demonstrate the catalytic
Figure 1. Azole ligands with different heteroatoms.
Results and Discussion
Dinuclear PdII complexes containing 3-benzyl-, 3-propyl-
and 3-isopropylbenzothiazolium-2-ylidene ligands[2] un-
dergo facile stoichiometric bridge-cleavage with an azole
[imidazole, 1-(2,4,6-trimethylphenyl)imidazole, benzimid-
azole, benzothiazole, benzoxazole] to give the mononuclear
mixed-ligand complexes 1–7 in 53–89% yield (Scheme 1,
Table 1). 1H NMR analysis of the products suggested
monodentate N-coordination of the azole, with the C-2
proton [NC(H)E] (E = NH, NR, S, O) still in place. Coordi-
nation in 1 and 2 occurs preferentially at the sp2-nitrogen
atom, and the oxygen and sulfur atoms of the heterocycle
in 4–7 are pendant. The two ligands (C-bonded benzothi-
azolin-2-ylidene and N-bonded benzothiazole) in 4, 6 and
7 share a common five-membered [C3NS] thiazole ring. The
[a] Department of Chemistry, National University of Singapore,
3 Science Drive 3, Singapore 117543
Fax: +65-6873-1324
E-mail: andyhor@nus.edu.sg
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200900447.
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Mixed-Ligand Palladium Complexes
signal of the isopropyl methine proton of 1–5 (δ = 6.57–
Complexes 1–7 were subjected to X-ray single-crystal dif-
6.68 ppm) is significantly downfield shifted (∆δ = 1.06– fraction analysis. They are all mononuclear with a square-
1.17 ppm) with respect to that in the benzothiazolium sub- planar palladium centre coordinated by the NSHC, azole
strate (δ = 5.51 ppm).[2c] This is attributed to an intramolec- and two halide ligands. The azole and carbene are invari-
ular anagostic C–H···Pd interaction, as discussed previous- ably trans-oriented in this series of isostructural complexes
ly.[2c,16–18] The 13C NMR resonances of the carbenic carbon (Figures 2 and 3 and Figures S1–S5 in the Supporting In-
atom of 1–7 (δ = 189.0–195.9 ppm) are deshielded with re- formation; see also Tables 2 and 5). The cis complexes are
spect to the trans-carbamoyl-substituted NHC-(3-methyl- obtained when the incoming ligand (e.g. PR3) has a higher
1H-imidazole)palladium(II) complex (δ = 151.57 ppm).[5]
trans influence than the halide.[2b]
Scheme 1. Synthesis of mixed NSHC/azole PdII complexes 1–7.
Table 1. Comparison of selected spectroscopic and structural data for complexes 1–7.
1
2
3
4
5
6
7
δ(1H): CH(CH3)2 [ppm]
∆δ [ppm][c]
6.57[a]
1.06
6.58[a]
1.07
–
6.58[b]
1.07
–
6.68[a]
1.17
6.62[b]
1.11
–
–
–
–
δ(1H): NCHS [ppm]
δ(1H): NCHO [ppm]
δ(1H): NCHN [ppm]
δ(13C): Ccarbene [ppm]
d(C–H···Pd) [Å]
–
–
9.46[a]
–
–
9.41[a]
9.44[a]
–
–
8.74[b]
–
–
–
–
–
8.41[a]
8.27[a]
190.3[a]
2.65
8.78[b]
192.8[b]
2.75
–
191.0[a]
189.9[a]
2.75
189.0[b]
2.65
195.9[a]
193.6[a]
2.69, 2.76
122.30, 121.60
1.948(4), 1.952(4)
–
–
–
–
θ(C–H···Pd) [°]
d(Pd–C) [Å]
123.50
1.943(6)
121.50
1.946(4)
121.10
1.956(9)
122.90
1.957(4)
1.952(4)
1.950(3)
[a] Measured in CDCl3. [b] Measured in [D6]DMSO. [c] ∆δ = δH(CHMe2 in complex) – δH(CHMe2 in 3-isopropylbenzothiazolium-2-
ylidene ligand).
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S. K. Yen, L. L. Koh, H. V. Huynh, T. S. A. Hor
FULL PAPER
115.50(7)–116.30(3)°]. The benzo rings of the azole ligands
are generally anti to the N-substituent of the carbene ring
(as in 3, 5, 6 and 7) with 4, which has a syn configuration,
the notable exception. The anagostic interactions between
the isopropyl CH groups and the metal atom found in solu-
tion are also witnessed in the solid-state structures (C–
H···Pd 2.65–2.76 Å for 1–5; Table 1). The decrease of the
C1–N1–C8 angle from 124.40(2)° in 3-isopropylbenzothi-
azolium triiodide[2c] to 120.20(3)–122.00(5)° in 1–5, despite
the replacement of H by a much larger Pd atom, also sup-
ports these intramolecular γ-hydrogen interactions.
The stoichiometric cross-coupling of benzyl halides and
arylboronic acids was examined in different solvents at
60 °C at a low catalyst loading of 1 mol-%. Complex 6 was
chosen as a representative model as it has the same benzo-
thiazole motif in both ligands and a sterically less de-
manding N-substituent (Table 3). The use of dmf as solvent
(Table 3, Entries 3 and 8) tends to give the highest yields,
possibly due to the presence of reducing formic acid.[20] Ad-
dition of H2O to the organic solvent increases the yields
significantly (Table 3, Entries 6–9), with a 1:1 mixture of
dmf/H2O giving a quantitative yield with all bases (NaOH,
K2CO3, Cs2CO3) used (Table 3, Entries 8, 10 and 11).
Under optimized conditions in dmf/H2O (1:1) with
K2CO3 as the common base, all the complexes are Suzuki-
active toward the formation of pharmacologically active di-
arylfluoromethanes (Table 4).[9] As the complexes are air-
stable, these catalytic preparations can be carried out in
standard glassware in air. They invariably give quantitative
yields for benzyl bromide (Table 4, Entries 1–7) and near-
quantitative yields for 2-fluorobenzyl (Table 4, Entries 8–
14), 2,4-difluorobenzyl (Table 4, Entries 15–21) and 2,6-di-
fluorobenzyl bromides (Table 4, Entries 22–28) at 60 °C
within 2 h (Table 4). A previous report on the use of trans-
[PdBr(N-succ)(PPh3)2] (1 mol-%; N-succ = N-halosuccin-
imides) with 4-fluorobenzyl bromide gave 91% yield,[21]
with a lower yield (69%) being obtained for the formation
Figure 2. ORTEP representation of two independent molecules in
the asymmetric unit cell of 1 with 50% thermal ellipsoids and label-
ling scheme. All hydrogen atoms, except that involved in metal in-
teraction, have been omitted for clarity.
Figure 3. ORTEP representation of complex 2 with 50% thermal
ellipsoids and labelling scheme. All hydrogen atoms, except that
involved in metal interaction, have been omitted for clarity.
The Pd–Ccarbene bond lengths [1.943(6)–1.957(4) Å] are of 1-benzyl-3,5-difluorobenzene.
within the range observed in other PdII complexes of benzo-
The complexes begin to show some differences when the
thiazolin-2-ylidene with a solvent molecule at the trans po- strongly electron-withdrawing 2-(trifluoromethyl)benzyl
sition[2a,3b] but are shorter than in their iodide-bridged pre- bromide is used as the substrate. Thus, complex 1 performs
cursor [1.968(6) Å],[2c] probably due to the weaker trans in- best, giving a near-quantitative yield, followed by 3, 4, 5
fluence of the azole ligand. The Pd–Nazole bond lengths and 2 (Table 4, Entries 29–35), thereby emphasising the ad-
[2.075(3)–2.114(5) Å] are similar to those in other mixed- vantage of the isopropyl substituent at the nitrogen atom.
ligand NHC/azole complexes of PdII.[5,19] The shortest, and Complexes 2, 3 and 6 also give high yields with 2,3,4,5,6-
presumably strongest, Pd–C bond in complexes 1–5, which pentafluorobenzyl bromide (Table 4, Entries 36–42). This
contain the same carbene ligand, is found in 2 together with system is also active towards benzyl chloride, with the best
the longest, and presumably weakest, Pd–N bond, whereas yields obtained for 2, 3 and 1 (in decreasing order). In gene-
the weakest Pd–C and strongest Pd–N bonds are found in ral, complexes with an isopropyl substituent on the NSHC
5. The carbene ring planes are almost orthogonal (80.30– ring and a second ligand of a (benz)imidazole type tend to
87.50°) to the metal coordination plane [PdCNX2] (X = Br, perform best in this type of benzylic coupling. Benzoxazole
I). The angle between the azole and the metal coordination or benzothiazole ligands are less favourable as a co-ligand.
planes in 1–7 varies over a wide range (36.6–83.5°).
Since 3 is among the best performers in this system, we
Metal coordination at the carbon atom in benzothiaz- examined its turnover numbers (TONs) with different fluo-
olin-2-ylidene complexes 4, 6 and 7 leads to a contraction roaryl bromides and found that the yields are essentially
of the N–C–S angle [110.60(3)–112.00(7)°],[4a] and greater quantitative at 0.01 mol-% catalyst loading, with TONs in
deviation from sp2 hybridisation, compared to those com- the range of 8800–10000. These results are summarized in
plexes containing a benzothiazoly ligand [116.30(3)° or Scheme 2.
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Mixed-Ligand Palladium Complexes
Table 2. Selected bond lengths [Å] and angles [°] for complexes 1–7.
Bond Lengths [Å]
1
2
3
4
5
6
7
Molecule a Molecule b
Pd1–C1
Pd1–N2
Pd1–Br1
Pd1–Br2
Pd1–I1
1.948(4)
2.113(4)
Pd2–C14
Pd2–N5
1.952(4)
2.075(3)
1.943(6)
2.114(5)
1.946(4)
2.082(4)
1.956(9)
2.098(8)
1.957(4)
2.096(3)
1.952(4)
2.081(3)
2.438(11)
2.424(11)
1.950(3)
2.090(3)
2.436(4)
2.423(5)
2.611(4)
2.622(5)
1.715(4)
Pd2–I3
Pd2–I4
S2–C14
2.616(4)
2.613(4)
1.717(4)
2.608(6)
2.608(6)
1.708(6)
2.603(5)
2.607(5)
1.712(5)
2.611(10) 2.608(4)
2.605(10) 2.612(4)
1.697(9)
1.733(9)
Pd1–I2
S1–C1
1.710(4)
1.717(4)
1.717(4)
1.711(3)
1.710(4)
S2–C11
S2–C15
O1–C11
N1–C1
N1–C8
N2–C11
N2–C12
N2–C15
N3–C11
N3–C12
N3–C14
1.353(5)
1.328(5)
1.501(5)
N4–C14
N4–C21
1.326(5)
1.499(5)
1.338(7)
1.480(8)
1.314(7)
1.334(6)
1.489(6)
1.301(6)
1.331(12) 1.330(5)
1.489(12) 1.491(5)
1.280(12) 1.284(5)
1.328(5)
1.476(4)
1.335(4)
1.480(4)
1.297(4)
1.329(6)
1.342(6)
N5–C24
N6–C24
1.305(5)
1.327(6)
1.298(5)
1.341(8)
1.444(8)
1.338(6)
Angles [°]
C1–Pd1–N2
C1–Pd1–Br1
C1–Pd1–Br2
N1–C1–S1
N2–Pd1–Br1
N2–Pd1–Br2
Br1–Pd1–Br2
C1–Pd1–I1
175.86(15) C14–Pd2–N5 175.80(15) 176.80(2) 174.73(18) 176.60(4) 178.55(14) 179.14(13) 177.01(12)
89.87(10)
88.38(10)
110.60(3)
90.57(8)
91.20(8)
90.94(9)
88.46(9)
110.80(2)
92.04(8)
88.55(8)
111.20(3)
N4–C14–S2
111.50(3)
111.40(4) 111.90(3)
112.00(7) 111.5(3)
177.89(19) 177.77(17)
88.00(12)
84.43(12)
92.72(10)
95.42(10)
C14–Pd2–I3
C14–Pd2–I4
N5–Pd2–I3
N5–Pd2–I4
87.40(12)
89.08(12)
93.26(10)
90.58(10)
87.40(16) 89.82(14)
85.52(16) 86.14(14)
93.32(13) 92.12(11)
94.02(13) 92.06(11)
88.00(3)
89.00(3)
93.60(2)
89.50(2)
87.45(11)
89.02(11)
93.59(9)
89.98(9)
C1–Pd1–I2
N2–Pd1–I1
N2–Pd1–I2
I1–Pd1–I2
C1–N1–C8
168.90(16) I3–Pd2–I4
174.23(16) 171.46(3) 175.58(18) 176.37(4) 175.86(15)
122.00(5) 120.70(4)
120.20(3)
128.90(3)
129.20(3)
C14–N4–C21 121.00(3)
121.70(8) 120.50(3) 122.30(3)
123.70(3)
122.50(2)
C11–N2–Pd1
C12–N2–Pd1
C15–N2–Pd1
N1–C1–Pd1
N2–C11–S2
N2–C15–S2
N2–C11–O1
N2–C11–N3
N2–C12–N3
Dihedral angle (PdCNX2/azole)
128.60(4) 130.00(3)
123.00(6) 124.60(3)
C24–N5–Pd2 127.70(3)
N4–C14–Pd2 131.00(3)
125.40(3)
126.40(4) 131.00(3)
129.40(7) 127.50(3) 127.90(3)
129.80(2)
116.30(3)
115.50(7)
116.30(3)
115.60(4)
110.70(6) 112.00(5)
110.20(5)
39.60
N5–C24–N6
–
–
110.80(4)
52.10
86.00
36.60
82.70
71.90
86.70
83.50
82.40
61.30
81.70
82.80
86.30
66.00
80.30
Dihedral angle (PdCNX2/NSHC) 87.50
Table 3. Cross-coupling of benzyl bromide and arylboronic acid[a] catalyzed by 6 in different solvents with Cs2CO3 as base.
Entry
Solvent
Yield [%]
1
2
3
thf
CH3CN
dmf
27
55
92
4
5
dioxane
H2O
34
67
6
7
8
9
10
11
thf/H2O (1:1)
CH3CN/H2O (1:1)
dmf/H2O (1:1)
dioxane/H2O (1:1)
dmf/H2O (1:1)[b]
dmf/H2O (1:1)[c]
37
87
100
84
100
99
[a] 0.8 mmol of ArX, 1.2 mmol of Cs2CO3, 0.8 mmol of PhB(OH)2. [b] K2CO3 as base. [c] NaOH as base.
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FULL PAPER
Table 4. Cross-coupling reactions catalyzed by complexes 1–7.
Run
Precatalyst
Substrate[a]
Yield [%]
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
1
2
3
4
5
6
7
1
2
3
4
5
6
7
1
2
3
4
5
6
7
1
2
3
4
5
6
7
1
2
3
4
5
6
7
1
2
3
benzyl bromide
benzyl bromide
benzyl bromide
benzyl bromide
benzyl bromide
benzyl bromide
benzyl bromide
100
100
100
100
100
100
100
100
99
100
99
99
98
98
100
99
100
98
99
97
98
99
96
100
98
97
98
97
98
88
95
94
95
89
91
73
92
95
83
84
90
87
62
89
76
2-fluorobenzyl bromide
2-fluorobenzyl bromide
2-fluorobenzyl bromide
2-fluorobenzyl bromide
2-fluorobenzyl bromide
2-fluorobenzyl bromide
2-fluorobenzyl bromide
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
2,4-difluorobenzyl bromide
2,4-difluorobenzyl bromide
2,4-difluorobenzyl bromide
2,4-difluorobenzyl bromide
2,4-difluorobenzyl bromide
2,4-difluorobenzyl bromide
2,4-difluorobenzyl bromide
2,6-difluorobenzyl bromide
2,6-difluorobenzyl bromide
2,6-difluorobenzyl bromide
2,6-difluorobenzyl bromide
2,6-difluorobenzyl bromide
2,6-difluorobenzyl bromide
2,6-difluorobenzyl bromide
2-(trifluoromethyl)benzyl bromide
2-(trifluoromethyl)benzyl bromide
2-(trifluoromethyl)benzyl bromide
2-(trifluoromethyl)benzyl bromide
2-(trifluoromethyl)benzyl bromide
2-(trifluoromethyl)benzyl bromide
2-(trifluoromethyl)benzyl bromide
2,3,4,5,6-pentafluorobenzyl bromide
2,3,4,5,6-pentafluorobenzyl bromide
2,3,4,5,6-pentafluorobenzyl bromide
2,3,4,5,6-pentafluorobenzyl bromide
2,3,4,5,6-pentafluorobenzyl bromide
2,3,4,5,6-pentafluorobenzyl bromide
2,3,4,5,6-pentafluorobenzyl bromide
benzyl chloride
benzyl chloride
benzyl chloride
[a] 0.8 mmol of ArX, 1.2 mmol of K2CO3, 0.8 mmol of PhB(OH)2.
Conclusions
Experimental Section
General Procedures: Unless otherwise stated, all manipulations
were performed without taking precautions to exclude air and
moisture. All solvents were used as received. Benzothiazole was
purchased from Sigma–Aldrich and distilled prior to use. Imid-
azole, benzimidazole, benzoxazole and Pd(OAc)2 were purchased
from Sigma–Aldrich and used as received. 1-(2,4,6-Trimeth-
The carbene hybrid system presented here utilizes azole
as a neutral nitrogen donor and its deprotonated form as a
heterocyclic carbene ligand. In principle, this synthetic
methodology and the structural motifs can be extended to
different types of heterocyclic carbenes and azoles. These
heterocycle-stabilised heterocyclic carbene complexes are
air-stable and easily prepared, and their efficacy toward
benzylic coupling has prompted us to examine similar com-
plexes for other catalytic applications. These results will be
reported in due course.
ylphenyl)-1H-imidazole was prepared as reported previously.[22] 1
H
and 13C NMR spectra were recorded with a Bruker AMX 500 spec-
trometer by using Me4Si as an internal standard. 19F NMR spectra
were recorded with a Bruker ACF 300 spectrometer by using
CF3CO2H as an external standard. ESI mass spectra were obtained
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Mixed-Ligand Palladium Complexes
Scheme 2. Cross-coupling of different fluorobenzyl bromides and arylboronic acid promoted by 3 at a 0.01 mol-% catalyst loading.
3
with a Finnigan MAT 731 LCQ spectrometer. The yield of the
hetero-coupling products was determined with a Hewlett–Packard
Series 6890 GC (Santa Clara, CA, USA) coupled to a Hewlett–
Packard 5973 MS detector. Elemental analyses were performed
with a Perkin–Elmer PE 2400 elemental analyzer at the Depart-
ment of Chemistry, National University of Singapore.
NCH=), 6.81 (s, 1 H, Ar-H), 6.58 [m, JH,H = 7.09 Hz, 1 H,
CH(CH3)2], 2.34 (s, 3 H, CH3), 2.17 (s, 3 H, CH3), 2.02 (s, 3 H,
CH3), 1.91 [d, JH,H = 7.55 Hz, 6 H, CH(CH3)2] ppm. 13C{1H}
3
NMR (125 MHz, CDCl3): δ = 190.3 (s, NCS), 143.5 (s, NCHN),
141.4, 139.6, 138.9, 135.1, 133.3, 132.5, 129.2, 125.9, 124.4, 122.1,
120.1, 115.8 (s, Ar-C), 63.1 [s, CH(CH3)2], 21.1 (s, CH3), 19.1 [s,
CH(CH3)2], 17.6 (s, CH3) ppm. MS (ESI, positive mode): m/z
trans-(Imidazole-κN)diiodo(3-isopropylbenzothiazolin-2-ylidene)pal-
ladium(II) (1): Complex 1 was prepared by suspending the dinu-
clear PdII precursor [Pd(µ-I)(NSHC)]2 [NSHC = 3-isopropylbenzo-
thiazolin-2-ylidene] (97 mg, 0.09 mmol) and imidazole (13 mg,
0.18 mmol) in CH2Cl2 (5 mL) and stirring the mixture at room
temp. overnight. The precipitate thus obtained was washed several
times with Et2O to give a yellow solid. Yellow single crystals of 1
were obtained upon diffusion of Et2O into a concentrated CH2Cl2
solution. Yield: 97 mg (0.16 mmol, 89 %). 1H NMR (500 MHz,
( % ) = 1 1 3 6 ( 1 0 0 ) [ M – I + 2 C 1 2 H 1 4 N 2 + C H 3 C N ] +
.
C22H25I2N3PdS·Et2O·CH2Cl2 (882.80): calcd. C 36.73, H 4.22, N
4.76, S 3.63; found C 36.92, H 4.72, N 4.59, S 3.92.
trans-(Benzimidazole-κN)diiodo(3-isopropylbenzothiazolin-2-ylidene)-
palladium(II) (3): Complex 3 was obtained as a yellow solid in anal-
ogy to 1 from the dinuclear PdII precursor (100 mg, 0.093 mmol)
and benzimidazole (22 mg, 0.186 mmol). Yellow single crystals of 3
were obtained upon diffusion of Et2O into a concentrated CH2Cl2
CDCl3): δ = 9.47 (s, 1 H, NH), 8.41 (s, 1 H, NCHN), 7.88 (d, 3JH,H solution. Yield: 100 mg (0.15 mmol, 82%). 1H NMR (500 MHz,
3
= 8.85 Hz, 1 H, Ar-H), 7.56 (d, JH,H = 10.08 Hz, 1 H, Ar-H),
[D6]DMSO): δ = 13.33 (s, 1 H, NH), 8.78 (s, 1 H, NCHN), 8.25
3
3
3
7.48–7.34 (m, 2 H, Ar-H), 6.98 (s, 2 H, NCH=), 6.57 [m, JH,H
=
(d, JH,H = 8.2 Hz, 1 H, Ar-H), 8.11 (d, JH,H = 8.2 Hz, 2 H, Ar-
3
7.15 Hz, 1 H, CH(CH3)2], 1.90 [d, JH,H = 6.95 Hz, 6 H, CH-
H), 7.60–7.55 (m, 2 H, Ar-H), 7.50 (t, 3JH,H = 7.6 Hz, 1 H, Ar-H),
(CH3)2] ppm. 13C{1H} NMR (125 MHz, CDCl3): δ = 191.0 (s, 7.40–7.34 (m, 2 H, Ar-H), 6.58 [m, JH,H = 6.6 Hz, 1 H, CH-
3
3
NCS), 141.4 (s, NCHN), 140.7, 138.9, 134.9, 132.1, 125.9, 124.5,
121.8, 115.8 (s, Ar-C), 63.1 [s, CH(CH3)2], 19.1 [s, CH(CH3)2] ppm.
MS (ESI, positive mode): m/z (%) = 546 (100) [M – I + imid-
azole]+. C13H15I2N3PdS·Et2O·H2O (697.71): calcd. C 29.26, H
3.90, N 6.02, S 4.60; found C 29.06, H 3.11, N 5.61, S 5.74. The
elemental analysis remained unsatisfactory despite repeated purifi-
cation and analysis, possibly due to solvation.
(CH3)2], 1.90 [d, JH,H = 7.0 Hz, 6 H, CH(CH3)2] ppm. 13C{1H}
NMR (125 MHz, [D6]DMSO): δ = 192.8 (s, NCS), 144.9 (s,
NCHN), 141.2, 140.5, 138.0, 132.5, 127.2, 125.4, 124.1, 123.2,
122.9, 122.3, 120.7, 116.8, 113.0 (s, Ar-C), 62.9 [s, CH(CH3)2], 19.1
[s, CH(CH3)2] ppm. MS (ESI, positive mode): m/z (%) = 645 (100)
[M – I + benzimidazole]+, 527 (60) [M – I]+. C17H17I2N3PdS
(655.63): calcd. C 31.14, H 2.61, N 6.41, S 4.89; found C 31.27, H
2.81, N 6.32, S 4.43.
trans-Diiodo(3-isopropylbenzothiazolin-2-ylidene)[1-(2,4,6-trimethyl-
phenyl)-1H-imidazole-κN]palladium(II) (2): Complex 2 was pre-
pared as a yellow solid in analogy to 1 from the dinuclear PdII
precursor (108 mg, 0.10 mmol) and 1-(2,4,6-trimethylphenyl)-1H-
imidazole (37 mg, 0.2 mmol). Yellow single crystals of 2 were ob-
trans-(Benzothiazole-κN)diiodo(3-isopropylbenzothiazolin-2-ylidene)-
palladium(II) (4): Complex 4 was prepared as a yellow solid in anal-
ogy to 1 from the dinuclear PdII precursor (193 mg, 0.18 mmol)
and benzothiazole (49 mg, 0.36 mmol). Yellow single crystals of 4
were obtained upon diffusion of Et2O into a concentrated CH2Cl2
tained upon diffusion of Et2O into a concentrated CH2Cl2 solution.
Yield: 76 mg (0.105 mmol, 53%). H NMR (500 MHz, CDCl3): δ solution. Yield: 155 mg (0.23 mmol, 64%). 1H NMR (500 MHz,
1
3
= 8.27 (s, 1 H, NCHN), 7.89 (s, 1 H, Ar-H), 7.88 (s, 1 H, Ar-H),
CDCl3): δ = 9.46 (s, 1 H, NCHS), 8.88 (d, JH,H = 8.20 Hz, 1 H,
Ar-H), 7.92 (d, JH,H = 8.20 Hz, 2 H, Ar-H), 7.80 (d, JH,H =
7.55 Hz, 1 H, Ar-H), 7.69 (t, JH,H = 7.88 Hz, 1 H, Ar-H), 7.55 (t,
3
3
3
3
7.75 (d, JH,H = 8.15 Hz, 1 H, Ar-H), 7.42 (t, JH,H = 7.88 Hz, 1
3
3
H, Ar-H), 7.35 (t, JH,H = 7.58 Hz, 1 H, Ar-H), 6.97 (s, 2 H,
Eur. J. Inorg. Chem. 2009, 4288–4297
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4293

S. K. Yen, L. L. Koh, H. V. Huynh, T. S. A. Hor
FULL PAPER
2/3
3JH,H = 7.25 Hz, 1 H, Ar-H), 7.46 (t, 3JH,H = 7.25 Hz, 1 H, Ar-H),
= 10.00 Hz, Ar-C), 125.1 (d,
J
= 29.32 Hz, Ar-C), 122.1 (d, 2/
C,C
3
3
7.39 (t, JH,H = 7.25 Hz, 1 H, Ar-H), 6.68 [m, JH,H = 7.15 Hz, 1
3JC,C = 12.84 Hz, Ar-C), 113.7 (s, Ar-C), 57.1 (s, CH2CH2CH3),
3
H, CH(CH3)2], 1.98 [d, JH,H = 6.95 Hz, 6 H, CH(CH3)2] ppm. 22.1 (s, CH2CH2CH3), 11.8 (s, CH2CH2CH3) ppm. MS (ESI, posi-
13C{1H} NMR (125 MHz, CDCl3): δ = 189.9 (s, NCS), 158.8 (s,
NCHS), 150.2, 141.3, 138.9, 131.7 (s, Ar-C), 126.8 (d,
20.95 Hz, Ar-C), 126.1, 125.7, 124.7 (s, Ar-C), 122.2 (d,
tive mode): m/z (%) = 541 (40) [M – Br +
CH3CN]+.
2/3
J
J
=
=
C17H16Br2N2PdS2 (578.68): calcd. C 35.28, H 2.79, N 4.84, S 11.08;
found C 35.18, H 2.56, N 4.79, S 10.35.
C,C
2/3
C,C
17.30 Hz, Ar-C), 115.9 (s, Ar-C), 63.7 [s, CH(CH3)2], 19.5 [s,
CH(CH3)2] ppm. MS (ESI, positive mode): m/z (%) = 586 (90) [M –
I + CH3CN]+. C17H16I2N2PdS2 (672.68): calcd. C 30.35, H 2.40,
N 4.16, S 9.53; found C 29.96, H 2.25, N 3.89, S 8.96.
General Procedure for the Suzuki–Miyaura Reaction: K2CO3
(1.2 mmol), benzyl halide (0.8 mmol), phenylboronic acid
(0.8 mmol) and dodecane (0.8 mmol as internal standard) were
placed in a reaction flask equipped with a stirring bar. An aliquot
of solvent (5 mL) was introduced, and the resulting suspension was
stirred at room temp. or 60 °C for 10 min before addition of the
catalyst. After the desired reaction time, the reaction mixture was
cooled to room temp., water was added and the product extracted
with CH2Cl2 (3ϫ4 mL). The combined organic extracts were dried
with MgSO4, filtered and the products analyzed by GC/MS. The
organic products were purified by TLC chromatography using
CH2Cl2 as eluent. The characterisation data of these products are
given below.
trans-(Benzoxazole-κN)diiodo(3-isopropylbenzothiazolin-2-ylidene)-
palladium(II) (5): Complex 5 was obtained as a yellow solid in anal-
ogy to 1 from the dinuclear PdII precursor (100 mg, 0.093 mmol)
and benzoxazole (22 mg, 0.186 mmol). Yellow single crystals of 5
were obtained upon diffusion of Et2O into a concentrated CH2Cl2
solution. Yield: 98 mg (0.15 mmol, 81%). 1H NMR (500 MHz, [D6]-
3
DMSO): δ = 8.74 (s, 1 H, NCHO), 8.39 (d, JH,H = 6.9 Hz, 1 H,
Ar-H), 7.91 (d, 3JH,H = 8.2 Hz, 1 H, Ar-H), 7.79 (d, 3JH,H = 7.6 Hz,
3
1 H, Ar-H), 7.61 (d, JH,H = 7.6 Hz, 1 H, Ar-H), 7.52–7.39 (m, 4
H, Ar-H), 6.62 [m, 3JH,H = 7.1 Hz, 1 H, CH(CH3)2], 1.96 [d, 3JH,H
= 7.0 Hz, 6 H, CH(CH3)2] ppm. 13C{1H} NMR (125 MHz, [D6]- 1-Benzylbenzene: The data are similar to those reported pre-
DMSO): δ = 189.0 (s, NCS), 156.2, 149.4, 141.3, 138.8, 137.2, viously.[21]
127.0, 126.2, 125.5, 124.7, 122.8, 122.2, 115.9, 111.5 (s, Ar-C), 63.4
1
1-Benzyl-2-fluorobenzene: H NMR (500 MHz, CDCl3): δ = 7.31–
7.28 (m, 2 H, Ar-H), 7.23–7.14 (m, 5 H, Ar-H), 7.07–7.02 (m, 2 H,
Ar-H), 4.01 (s, 2 H, CH2) ppm. 13C{1H} NMR (125 MHz, CDCl3):
[s, CH(CH3)2], 19.1 [s, CH(CH3)2] ppm. MS (ESI, positive mode):
m/z (%) = 656 (100) [M + H]+. C17H16I2N2OPdS (656.62): calcd.
C 31.10, H 2.46, N 4.27, S 4.88; found C 31.34, H 2.78, N 4.31, S
5.15.
1
δ = 161.0 (d, JC,F = 243.20 Hz, Ar-C), 139.9 (s, Ar-C), 131.0 (d,
4/5
2
J
= 4.55 Hz, Ar-C), 128.7 (d, JC,F = 36.44 Hz, Ar-C), 128.1
C,F
3/4
trans-(Benzothiazole-κN)(3-benzylbenzothiazolin-2-ylidene)dibrom-
idopalladium(II) (6): Complex 6 was prepared in analogy to 1 from
the dinuclear PdII precursor [PdBr(µ-Br)(NSHC)]2 [NSHC = 3-
benzylbenzothiazolin-2-ylidene; 88 mg, 0.09 mmol] and benzothi-
azole (24 mg, 0.18 mmol). Yellow single crystals of 6 were obtained
upon diffusion of Et2O into a concentrated CH2Cl2 solution. Yield:
(s, Ar-C), 127.9 (d,
(d,
J
C,F
= 8.20 Hz, Ar-C), 126.2 (s, Ar-C), 124.1
4/5
2
J
= 3.60 Hz, Ar-C), 115.3 (d, JC,F = 21.86 Hz, Ar-C),
C,F
4/5
111.2 (s, Ar-C), 34.8 (d,
J
C,F
= 2.74 Hz, CH2) ppm. 19F{1H}
NMR (282.28 MHz, CDCl3): δ = –41.9 (s, 1 F, Ar-F) ppm. GC/
MS analysis: m/z = 186 [M]+.
94 mg (0.15 mmol, 83%). 1H NMR (500 MHz, CDCl3): δ = 9.41 1-Benzyl-2,4-difluorobenzene: 1H NMR (500 MHz, CDCl3): δ =
3
(s, 1 H, NCHS), 8.90 (d, JH,H = 8.15 Hz, 2 H, Ar-H), 7.89 (d,
7.31–7.28 (m, 3 H, Ar-H), 7.23–7.18 (m, 3 H, Ar-H), 7.11–7.07 (m,
1 H, Ar-H), 6.82–6.77 (m, 1 H, Ar-H), 3.96 (s, 2 H, CH2) ppm.
3
3JH,H = 8.20 Hz, 1 H, Ar-H), 7.63 (d, JH,H = 6.90 Hz, 4 H, Ar-
H), 7.51–7.47 (m, 2 H, Ar-H), 7.42–7.33 (m, 4 H, Ar-H), 6.62 (s, 2 13C{1H} NMR (125 MHz, CDCl3): δ = 139.6 (s, Ar-C), 131.5 (d,
H, CH2) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ = 195.9 (s,
J
C,F
3
= 3.65 Hz, Ar-C), 131.4 (d, JC,F = 15.49 Hz, Ar-C), 128.6
4/5
3
4/5
NCS), 158.8 (s, NCHS), 149.7, 142.8, 136.7, 135.4, 133.8, 133.6, (d, JC,F = 16.40 Hz, Ar-C), 126.4 (s, Ar-C), 111.2 (d,
J
C,F
=
2/3
4/5
131.8, 129.2, 128.6, 127.7 (s, Ar-C), 127.2 (d,
J
C,C
= 10.03 Hz,
3.63 Hz, Ar-C), 111.0 (d,
J
C,F
= 4.56 Hz, Ar-C), 104.9 (s, Ar-C),
2/3
2
4/5
Ar-C), 127.0 (s, Ar-C), 126.8 (d,
J
= 11.84 Hz, Ar-C), 125.2
103.7 (t, JC,F = 25.50 Hz, Ar-C), 34.3 (d,
J
C,F
= 1.83 Hz, CH2)
C,C
2/3
2/3
(d,
J
C,C
= 14.58 Hz, Ar-C), 121.9 (d,
J
C,C
= 25.51 Hz, Ar-C),
ppm. 19F{1H} NMR (282.28 MHz, CDCl3): δ = –37.2 (d, JC,F
=
115.1 (s, Ar-C), 60.1 (s, C2) ppm. MS (ESI, positive mode): m/z
8.27 Hz, 1 F, Ar-F), –37.6 (d, JC,F = 8.24 Hz, 1 F, Ar-F) ppm. GC/
(%) = 589 (90) [M – Br + CH3CN]+. C21H16Br2N2PdS2 (626.72): MS analysis: m/z = 204 [M]+.
calcd. C 40.24, H 2.54, N 4.47, S 10.23; found C 39.02, H 2.56, N
4.18, S 9.37.
1-Benzyl-2,6-difluorobenzene: 1H NMR (500 MHz, CDCl3): δ =
7.29–7.25 (m, 4 H, Ar-H), 7.21–7.12 (m, 2 H, Ar-H), 6.89–6.85 (m,
2 H, Ar-H), 4.01 (s, 2 H, CH2) ppm. 13C{1H} NMR (125 MHz,
trans-(Benzothiazole-κN)dibromido(3-propylbenzothiazolin-2-ylidene)-
palladium(II) (7): Complex 7 was prepared as a yellow solid in anal-
ogy to 1 from the dinuclear PdII precursor [PdBr(µ-Br)(NSHC)2]
[NSHC = 3-propylbenzothiazolin-2-ylidene; 79 mg, 0.089 mmol]
and benzothiazole (24 mg, 0.178 mmol). Yellow single crystals of 7
were obtained upon diffusion of Et2O into a concentrated CH2Cl2
solution. Yield: 82 mg (0.142 mmol, 80%). 1H NMR (500 MHz,
1
CDCl3): δ = 161.4 (d, JC,F = 250.00 Hz, Ar-C), 139.2, 128.8 (s,
4/5
3/4
Ar-C), 128.5 (d,
J
= 6.38 Hz, Ar-C), 127.9 (t,
J
C,F
=
C,F
3/4
10.48 Hz, Ar-C), 127.2 (d,
J
= 10.01 Hz, Ar-C), 126.3, 116.9
C,F
3/4
4/5
(s, Ar-C), 111.2 (dd,
J
= 20.04,
J
C,F
= 6.38 Hz, Ar-C), 28.2
C,F
4/5
(d,
J
C,F
= 2.72 Hz, CH2) ppm. 19F{1H} NMR (282.28 MHz,
CDCl3): δ = –39.0 (s, 2 F, Ar-F) ppm. GC/MS analysis: m/z = 204
3
[M]+.
CDCl3): δ = 9.44 (s, 1 H, NCHS), 8.99 (d, JH,H = 8.20 Hz, 1 H,
3
3
Ar-H), 7.93 (d, JH,H = 8.20 Hz, 1 H, Ar-H), 7.85 (d, JH,H
=
3
1
7.55 Hz, 1 H, Ar-H), 7.72 (d, JH,H = 8.20 Hz, 1 H, Ar-H), 7.69 (t,
1-Benzyl-2-(trifluoromethyl)benzene: H NMR (500 MHz, CDCl3):
3JH,H = 7.88 Hz, 1 H, Ar-H), 7.55 (t, 3JH,H = 7.88 Hz, 2 H, Ar-H),
δ = 7.69–7.61 (m, 1 H, Ar-H), 7.47–7.35 (m, 1 H, Ar-H), 7.33–7.30
3
3
7.46 (t, JH,H = 7.60 Hz, 1 H, Ar-H), 5.25 (t, JH,H = 8.18 Hz, 2 (m, 3 H, Ar-H), 7.25–7.22 (m, 1 H, Ar-H), 7.19–7.15 (m, 3 H, Ar-
H, CH2CH2CH3), 2.44 (p. sext, JH,H
= 7.82 Hz, 2
H, H), 4.20 (s, 2 H, CH2) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ
3
3
CH2CH2CH3), 1.30 (t, JH,H = 7.58 Hz, 3 H, CH2CH2CH3) ppm. = 141.3, 139.9, 139.5, 131.8, 131.7, 129.2, 128.8, 128.6 (s, Ar-C),
13C{1H} NMR (125 MHz, CDCl3): δ = 193.6 (s, NCS), 158.8 (s,
127.2 (d,
J
= 10.93 Hz, Ar-C), 126.3 (d,
J
C,F
= 13.66 Hz,
3/4
3/4
C,F
2/3
4/5
NCHS), 149.7, 142.9, 136.7, 131.9, 127.0 (s, Ar-C), 126.8 (d,
J
C,C
Ar-C), 125.9 (q,
J
C,F
= 5.77 Hz, CF3), 125.7 (s, Ar-C), 37.8 (d,
4294
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 4288–4297

Mixed-Ligand Palladium Complexes
4/5
J
C,F
= 1.81 Hz, CH2) ppm. 19F{1H} NMR (282.28 MHz, 1-(2,4-Difluorobenzyl)-4-methylbenzene: 1H NMR (500 MHz,
CDCl3): δ = 16.3 (s, 3 F, CF3) ppm. GC/MS analysis: m/z = 236
CDCl3): δ = 7.14–7.08 (m, 5 H, Ar-H), 6.83–8.78 (m, 2 H, Ar-H),
[M]+.
3.93 (s, 2 H, CH2), 2.34 (s, 3 H, CH3) ppm. 13C{1H} NMR
1
3/4
(125 MHz, CDCl3): δ = 161.6 (dd, JC,F = 246.25,
J
= 12.75
1-Benzyl-2,3,4,5,6-pentafluorobenzene: 1H NMR (500 MHz,
CDCl3): δ = 7.34–7.29 (m, 2 H, Ar-H), 7.25–7.23 (m, 3 H, Ar-H),
4.04 (s, 2 H, CH2) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ =
146.0–145.9 (m, Ar-C), 144.1–143.9 (m, Ar-C), 141.3 (s, Ar-C),
C,F
and 12.36 Hz, Ar-C), 160.8 (dd, 1JC,F = 246.25,
J
= 10.90 and
3/4
C,F
11.85 Hz, Ar-C), 138.3, 136.7, 136.5, 135.9 (s, Ar-C), 131.5 (d,
4/5
4/5
J
C,F
= 6.39 Hz, Ar-C), 131.4 (d,
J
C,F
4/5
= 6.38 Hz, Ar-C), 129.5,
128.3, 128.6 126.8 (s, Ar-C), 124.3 (d,
124.2 (d,
C), 110.9 (d,
Ar-C), 33.8 (d,
J
C,F
4/5
= 4.56 Hz, Ar-C),
140.9–140.8 (m, Ar-C), 139.0–138.8 (m, Ar-C), 138.6–138.4 (m, Ar-
4/5
J
C,F
4/5
= 3.64 Hz, Ar-C), 111.1 (d,
J
= 3.65 Hz, Ar-
3/4
C,F
C), 137.5 (s, Ar-C), 136.7–136.4 (m, Ar-C), 128.8 (d,
J
C,F
=
2/3
J
C,F
4/5
= 4.55 Hz, Ar-C), 103.7 (t,
= 2.74 Hz, CH2), 21.0 (d,
J
= 25.51 Hz,
3/4
C,F
8.20 Hz, Ar-C), 128.3 (s, Ar-C), 127.2 (d,
J
C,F
= 10.93 Hz, Ar-
= 18.68 Hz, Ar-C), 28.1 (s,
4/5
J
C,F
J
C,F
= 9.11 Hz,
2/3
C), 126.9 (s, Ar-C), 114.4 (t,
J
C,F
CH3) ppm. 19F{1H} NMR (282.28 MHz, CDCl3): δ = –37.4 (d,
JC,F = 8.24 Hz, 1 F, Ar-F), –38.7 (d, JC,F = 8.24 Hz, 1 F, Ar-F)
ppm. GC/MS analysis: m/z = 218 [M]+.
CH2) ppm. 19F{1H} NMR (282.28 MHz, CDCl3): δ = –67.3 (d,
JC,F = 8.24 Hz, 1 F, Ar-F), –67.4 (d, JC,F = 8.24 Hz, 1 F, Ar-F),
–81.1 (t, JC,F = 20.61 Hz, 1 F, Ar-F), –86.3 (d, JC,F = 8.24 Hz, 1
F, Ar-F), –86.4 (d, JC,F = 8.24 Hz, 1 F, Ar-F) ppm. GC/MS analy-
sis: m/z = 258 [M]+.
1-(2,6-Difluorobenzyl)-4-methylbenzene: 1H NMR (500 MHz,
3
CDCl3): δ = 7.49 (d, JH,H = 8.20 Hz, 1 H, Ar-H), 7.18–7.09 (m, 4
H, Ar-H), 6.87 (t, 3JH,H = 7.58 Hz, 2 H, Ar-H), 3.99 (s, 2 H, CH2),
1
1-Benzyl-4-methylbenzene: H NMR (500 MHz, CDCl3): δ = 7.48
2.31 (s, 3 H, CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ =
3
3
(d, JH,H = 8.20 Hz, 5 H, Ar-H), 7.23 (d, JH,H = 8.20 Hz, 2 H,
1
4/5
5
161.4 (dd, JC,F = 250,
J
C,F
= 9.11 and 8.20 Hz, Ar-C), 138.3,
Ar-H), 7.09 (d, JH,H = 1.90 Hz, 1 H, Ar-H), 3.99 (s, 2 H, CH2),
3/4
2.38 (s, 3 H, CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ =
138.3, 136.7, 129.4, 129.1, 128.9, 128.8, 128.4, 126.8, 125.9 (s, Ar-
C), 53.4 (s, CH2), 21.1 (s, CH3) ppm. GC/MS analysis: m/z = 182
[M]+.
136.7, 136.2, 135.8, 129.4, 129.2, 128.3 (s, Ar-C), 127.7 (t,
J
=
C,F
4/5
10.0 Hz, Ar-C), 126.8 (s, Ar-C), 111.3 (d,
J
C,F
= 6.34 Hz, Ar-C),
4/5
4/5
111.1 (d,
J
= 6.38 Hz, Ar-C), 27.8 (s, CH2), 21.0 (s,
J
C,F
=
C,F
9.10 Hz, CH3) ppm. 19F{1H} NMR (282.28 MHz, CDCl3): δ =
–39.1 (s, 1 F, Ar-F), –40.3 (s, 1 F, Ar-F) ppm. GC/MS analysis: m/z
= 218 [M]+.
1
2-(Fluorobenzyl)-4-methylbenzene: H NMR (500 MHz, CDCl3): δ
= 7.21–7.09 (m, 6 H, Ar-H), 7.06–7.01 (m, 2 H, Ar-H), 3.97 (s, 2
H, CH2), 2.32 (s, 2 H, CH3) ppm. 13C{1H} NMR (125 MHz,
4-Methyl-2-(trifluorobenzyl)benzene: H NMR (500 MHz, CDCl3):
1
1
3
CDCl3): δ = 160.9 (d, JC,F = 244.13 Hz, Ar-C), 136.8, 136.7 (s,
δ = 7.37–7.28 (m, 2 H, Ar-H), 7.25 (d, JH,H = 8.20 Hz, Ar-H),
4/5
3
3
Ar-C), 131.0 (d,
Ar-C), 128.4 (d,
J
J
= 4.55 Hz, Ar-C), 129.4, 129.2, 128.7 (s,
7.18 (d, JH,H = 8.20 Hz, Ar-H), 7.12 (d, JH,H = 8.15 Hz, Ar-H),
C,F
3/4
4/5
3
= 15.49 Hz, Ar-C), 127.8 (d,
J
=
7.05 (d, JH,H = 8.20 Hz, Ar-H), 4.16 (s, 2 H, CH2), 2.34 (s, 3 H,
C,F
C,F
8.20 Hz, Ar-C), 126.8 (s, Ar-C), 124.0 (d,
J
C,F
= 3.65 Hz, Ar-C),
CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ = 140.0 (d, JC,F
4/5
2
2/3
4/5
3/4
115.3 (d,
J
C,F
= 21.86 Hz, Ar-C), 34.4 (d,
J
C,F
= 3.65 Hz, = 31.89 Hz, Ar-C), 138.3 (s, Ar-C), 136.8 (d,
J
= 12.75 Hz,
J = 9.11 Hz,
C,F
C,F
CH2), 21.0 (s, CH3) ppm. 19F{1H} NMR (282.28 MHz, CDCl3): δ
= –42.0 (s, 1 F, Ar-F) ppm. GC/MS analysis: m/z = 200 [M]+.
Ar-C), 135.8 (s, Ar-C), 131.9 (s, Ar-C), 131.7 (d,
Ar-C), 131.4, 129.4 (s, Ar-C), 129.1 (d,
3/4
2/3
J
= 22.76 Hz, Ar-C),
C,F
Table 5. Selected crystallographic data for complexes 1–7.
1
2
3
4
5
6
7
Empirical formula
Formula mass
Color, habit
Crystal size [mm]
Temperature [K]
Crystal system
Space group
a [Å]
C13H15I2N3S1 Pd C22H25I2N3SPd C17H17I2N3SPd C18H17.25Cl2.75I2N2S2Pd C17H16I2N2SO Pd C21H16Br2N2S2Pd C17H16Br2N2S2Pd
605.54
723.71
655.60
783.40
656.58
626.70
578.66
orange, block
orange, needle
orange, block
orange, block
orange, block
yellow, needle
white, block
0.32ϫ0.10ϫ0.05 0.36ϫ0.06ϫ0.02 0.16ϫ0.16ϫ0.10 0.18ϫ0.14ϫ0.06
0.26ϫ0.12ϫ0.02 0.20ϫ0.10ϫ0.06 0.30ϫ0.10ϫ0.10
223(2) K
monoclinic
P21/c
295(2) K
orthorhombic
Pbca
223(2) K
monoclinic
P21/c
293(2) K
orthorhombic
Pbca
223(2) K
monoclinic
P21/c
223(2) K
monoclinic
P21/n
223(2) K
monoclinic
P21/c
19.6046(7)
15.1707(6)
12.3633(5)
90
9.1240(6)
15.7419(11)
35.431(2)
90
15.1785(9)
8.1886(5)
16.8322(10)
90
17.9597(15)
9.8547(9)
27.837(3)
90
9.1743(5)
10.8697(6)
20.8718(11)
90
5.824(4)
19.560(11)
18.648(11)
90
9.3539(5)
18.6679(10)
10.7483(6)
90
b [Å]
c [Å]
α [°]
β [°]
γ [°]
V [Å3]
107.4560(10)
90
3507.7(2)
8
2.293
Mo-Kα
4.691
90
90
5088.9(6)
8
1.889
101.7340(10)
90
2048.4(2)
4
2.126
Mo-Kα
90
90
4926.7(8)
8
2.112
102.3720(10)
90
2033.04(19)
4
2.145
Mo-Kα
94.899(14)
90
2117(2)
95.6270(10)
90
1867.80(18)
4
2.058
Mo-Kα
Z
4
Dc [gcm–3]
Radiation
µ [mm–1]
1.967
Mo-Kα
4.859
Mo-Kα
3.251
Mo-Kα
3.736
4.026
4.059
5.497
θ range [°]
Unique data
R(int)
1.72–27.50
24526
0.0284
1.15–27.50
34166
0.0627
1.37–27.50
13991
0.0317
1.46–27.50
32984
0.0929
2.00–27.49
14161
0.0347
1.51–27.50
14854
0.0386
2.18–27.50
13133
0.0291
Max., min transmission
Final R indices [I Ͼ 2σ(I)] R1 = 0.0342,
wR2 = 0.0755
0.7993, 0.3152
0.9378, 0.3874
R1 = 0.0547,
wR2 = 0.1237
R1 = 0.0806,
wR2 = 0.1401
1.163
0.6889, 0.5652
R1 = 0.0386,
wR2 = 0.0873
R1 = 0.0493,
wR2 = 0.0974
1.042
0.8069, 0.5528
R1 = 0.0762,
wR2 = 0.1541
R1 = 0.1084,
wR2 = 0.1659
1.132
0.9232, 0.4184
R1 = 0.0343,
wR2 = 0.0745
R1 = 0.0440,
wR2 = 0.0790
1.035
0.7592, 0.4432
R1 = 0.0339,
wR2 = 0.0782
R1 = 0.0481,
wR2 = 0.0926
1.054
0.6094, 0.2894
R1 = 0.0322,
wR2 = 0.0800
R1 = 0.0417,
wR2 = 0.0834
1.074
R indices (all data)
R1 = 0.0404,
wR2 = 0.0783
1.072
Goodness-of-fit on F2
Peak/hole [eÅ–3]
1.219/–0.580
1.026/–1.050
1.893/–1.361
1.558/–0.996
1.109/–0.884
0.670/–0.631
1.072/–0.430
Eur. J. Inorg. Chem. 2009, 4288–4297
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4295

S. K. Yen, L. L. Koh, H. V. Huynh, T. S. A. Hor
FULL PAPER
N-Heterocyclic Carbenes in Synthesis, Wiley-VCH, Weinheim,
Germany, 2006; i) P. L. Arnold, S. Pearson, Coord. Chem. Rev.
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Heterocyclic Carbenes in Transition Metal Catalysis: Topics in
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2008, 47, 3122.
a) S. K. Yen, L. L. Koh, F. E. Hahn, H. V. Huynh, T. S. A. Hor,
Organometallics 2006, 25, 5105; b) S. K. Yen, L. L. Koh, H. V.
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128.8, 128.6 (s, Ar-C), 126.8, 126.3, 126.1 (s, Ar-C), 126.0 (d,
4/5
4/5
J
= 6.38 Hz, Ar-C), 125.8 (q,
J
= 5.77 Hz, CF3), 123.5
C,F
C,F
4/5
4/5
(s, Ar-C), 37.4 (d,
J
C,F
= 1.83 Hz, CH2), 21.0 (d,
J
C,F
=
7.29 Hz, CH3) ppm. 19F{1H} NMR (282.28 MHz, CDCl3): δ =
16.4 (s, 3 F, CF3) ppm. GC/MS analysis: m/z = 250 [M]+.
4-Methyl-(2,3,4,5,6-pentafluorobenzyl)benzene:
1H
NMR
(500 MHz, CDCl3): δ = 7.15–7.11 (m, 4 H, Ar-H), 3.99 (s, 2 H,
CH2), 2.33 (s, 3 H, CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3):
δ = 144.1–143.9 (m, Ar-C), 140.9–140.8 (m, Ar-C), 138.9–138.7 (m,
[2]
Ar-C), 138.6–138.4 (m, Ar-C), 138.3 (s, Ar-C), 136.7–136.4 (m, Ar-
4/5
C), 134.4 (s, Ar-C), 129.5 (d,
J
C,F
= 6.38 Hz, Ar-C), 128.2, 126.8
2/3
(s, Ar-C), 114.7 (t,
J
C,F
= 18.22 Hz, Ar-C), 27.7 (s, CH2), 20.9 (s,
[3]
[4]
a) S. K. Yen, L. L. Koh, H. V. Huynh, T. S. A. Hor, Dalton
Trans. 2007, 3952; b) S. K. Yen, L. L. Koh, H. V. Huynh,
T. S. A. Hor, Chem. Asian J. 2008, 3, 1649.
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JC,F = 8.24 Hz, 1 F, Ar-F), –67.5 (d, JC,F = 8.24 Hz, 1 F, Ar-F),
–81.4 (t, JC,F = 20.61 Hz, 1 F, Ar-F), –86.4 (d, JC,F = 8.24 Hz, 1
F, Ar-F), –86.5 (d, JC,F = 8.24 Hz, 1 F, Ar-F) ppm. GC/MS analy-
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X-ray Diffraction Studies: Single crystals of complexes 1–7 were
obtained by diffusion of Et2O into CH2Cl2 solutions. The crystal
of 1 contained two independent molecules in the asymmetric unit
of the cell. Suitable crystals were mounted on quartz fibres and X-
ray data collected with a Bruker AXS APEX diffractometer
equipped with a CCD detector and a graphite-monochromated
Mo-Kα radiation source (λ = 0.71073 Å). Data collection, reflection
indexing and determination of the lattice parameters and polariza-
tion effects were performed with the SMART program suite.[23] In-
tegration of reflection intensities and scaling were performed with
SAINT. Empirical absorption correction was performed with SA-
DABS.[24] Space group determination, structure solution and least-
squares refinements on |F|2 were carried out with SHELXTL.[25]
The structures were solved by direct methods to locate the heavy
atoms, followed by difference maps for the light non-hydrogen
atoms. Anisotropic thermal parameters were refined for the rest of
the non-hydrogen atoms, with hydrogen atoms placed in their ideal
positions. The structures of 1 and 2 are shown in Figures 2 and 3,
respectively, whereas the other structures (of 3–7) are available as
Supporting Information. Selected crystal data for complexes 1–7
are given in Tables 2 and 5. CCDC-742911 (1), -743693 (2), -743695
(4), -743696 (5) and -743698 (7) contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
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Acknowledgments
We thank the National University of Singapore (NUS) and the
Ministry of Education & Agency for Science, Technology & Re-
search for financial support (grant nos. R-143-000-277-305 and R-
143-000-361-112) as well as the staff at the CMMAC of NUS for
technical assistance. S. K. Y. acknowledges the NUS for a research
scholarship and K. E. Neo for helpful discussions.
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Received: May 17, 2009
Published Online: August 20, 2009
Eur. J. Inorg. Chem. 2009, 4288–4297
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4297