A new class of o-hydroxyaryl-substituted N-heterocyclic carbene ligands and their complexes with palladium

Article abstract of DOI:10.1016/j.jorganchem.2007.01.028

A facile synthesis of o-hydroxyaryl-substituted N-heterocyclic carbene ligands and their complexes with palladium is presented. This kind of salicylaldimine-like NHC ligands expands the class of available NHC ligands for organometallic catalysts.

Full text of DOI:10.1016/j.jorganchem.2007.01.028

Journal of Organometallic Chemistry 692 (2007) 2092–2098
www.elsevier.com/locate/jorganchem
A new class of o-hydroxyaryl-substituted N-heterocyclic carbene
ligands and their complexes with palladium
*
Hongping Ren, Peiyuan Yao, Shansheng Xu, Haibin Song, Baiquan Wang
State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Weijin Road 94#, Tianjin 300071, PR China
Received 22 December 2006; received in revised form 18 January 2007; accepted 18 January 2007
Available online 25 January 2007
Abstract
A facile synthesis of o-hydroxyaryl-substituted N-heterocyclic carbene ligands and their complexes with palladium is presented. This
kind of salicylaldimine-like NHC ligands expands the class of available NHC ligands for organometallic catalysts.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: o-Hydroxyaryl-substituted N-heterocyclic carbene; Palladium; Crystal structure; Suzuki–Miyaura coupling
1. Introduction
such as A. Some metal complexes bearing such ligands
were synthesized, characterized, and applied in catalysis
[6]. Framework B provides another interesting structure
of [C, O] chelating [7]. Unfortunately, this kind of NHC
enolate metal complexes is unstable to electrophiles [7a],
which limits their applications. Framework C is the most
interesting type of [C, O] chelating. This kind of o-hydroxy-
aryl-substituted NHC ligands would be analogue of the
salicylaldimine framework, a common motif in organome-
tallic chemistry [8,9a]. But the reports of such o-hydroxya-
ryl-substituted NHCs are really rare [9] due to the difficulty
in the synthesis of the ligands. Hoveyda et al. reported
binaphthol substituted NHCs and their metal complexes
[10]. Grubbs et al. reported the synthesis of a class of
o-hydroxyaryl substituted saturated NHCs and their Pd
and Ni complexes [9]. However, the synthesis of these
ligands is somewhat lengthy. Here we report a facile syn-
thesis of o-hydroxyaryl substituted unsaturated NHCs
and their Pd allylic complexes.
Since the isolation of the free N-heterocyclic carbene
(NHC) by Arduengo and co-workers firstly in 1991,
NHC ligands have been used extensively in organometallic
and catalytic reactions [1]. As neutral two-electron-donor
ligands, NHCs are strong r-donors and weak p-acceptors
[1d–3]. This feature provides their metal complexes quite
different electronic properties and reactivities compared
with the traditional neutral ligands such as phosphines
[1d]. Some NHC complexes show enhanced activities in
catalytic reactions than their analogues [1e,4,5]. Concern-
ing the structural feature, it is easy to change the steric
and electronic feature through changing the substituents
on the nitrogen atoms. This provides a way to control
the reaction and catalytic activities of their metal
complexes.
Recently much research effort has been devoted to the
study of [C, O] chelating NHC ligands. There are three
types of framework being able to provide an [C, O] chelat-
ing (Chart 1). The bonding between the NHC and metal
can be enhanced by alkoxide or phenoxide as a sidearm
through the incorporation of chelating anionic oxygen,
2. Results and discussion
In 1981, Tashiro et al. discovered that 4-bromo-2,4,6-tri-
tert-butyl-2,5-cyclohexadien-1-one (1) reacted with nucleo-
philic reagent such as pyridine afforded an unexpected
o-substituted phenol (Scheme 1) [11]. Then they expanded
*
Corresponding author. Tel./fax: +86 22 23504781.
E-mail address: bqwang@nankai.edu.cn (B. Wang).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.01.028

H. Ren et al. / Journal of Organometallic Chemistry 692 (2007) 2092–2098
2093
OH
tBu
O
M
M
R
R
But
tBu
But
R
N
O
O
N
N
N
EG
R
N
N
+
R1
R2
135oC
N
n
N
Br
R
R
tBu
Br
A
B
4
1
4a, R= t-Bu
4b, R= Cy
M
M
R
Ar
O
O
N
N
(Mes)
4c,R
=
N
R
Scheme 3.
Salicylaldimine
framework
C
pounds 4 in large scale. The compounds 4 are soluble in
Chart 1.
CH2Cl2, CHCl3, methanol and insoluble in hexane and
diethyl ether. All the H NMR spectra show a singlet at
1
9–10 ppm for the imidazolium proton (9.50 for 4a, 9.48
for 4b, and 10.06 for 4c), two singlets for the phenyl pro-
tons, two doublets for the imidazole protons, and two sing-
lets for the tert-butyl groups at the aryl ring, but no the
signal of phenol proton. It agrees with the spectra of 3
[12] and other known imidazolium salts [12]. Compared
with their saturated analogues reported by Grubbs, the res-
onances for imidazolium protons are shifted downfield
obviously, in consistent with the trend between the diaryl
imidazolium salts and their saturated analogues [13]. All
the Mass spectra of 4 show the cationic peaks of
[M+ÀBr]. The molecular structure of 4b was further con-
firmed by single crystal X-ray diffraction analysis (Fig. 1).
The NHC precursors 4 were deprotonated with 2 equiv
of n-BuLi in THF at room temperature, and then further
reacted with [(allyl)PdCl]2 to give the complexes 5a–c
(Scheme 4). All three complexes are air stable. Compared
with other known NHC allylic palladium complexes, com-
plexes 5a–c are more thermal stable with higher decompo-
sition temperatures [14]. This may due to the rigidity of the
chelating ligands, which prevent the reductive elimination
[15].
OH
O
tBu
But
tBu
N
EG
110oC
+
N
Br
tBu
tBu
Br
EG= ethylene glycol
1
2
Scheme 1.
the reactant to 1-methylimidazole, and the o-hydroxyaryl-
substituted imidazolium salt 3 was achieved in moderate
yield (35%) (Scheme 2) [12]. However, since then there is
no report on the synthesis of the ligands with other N-
substituted imidazoles and their metal complexes. So we
synthesized a series of o-hydroxyaryl substituted imidazo-
lium salts 4 from 1 and different N-substituted imidazoles
using the similar method (Scheme 3).
The reactions were carried out in an argon atmosphere
at 135 ꢁC. N-Substituted imidazole, ethylene glycol and 1
were added in a molar ratio of 2:1:1 for higher yield. Dif-
ferent to 1-methylimidazole, high reaction temperature
(135 ꢁC) is necessary for the formation of 4, possibly due
to the bulky substituents at imidazole of 4. The yields were
lower than that with the less steric reactant N-methyl imid-
azole. The major side products were 2,4,6-tri-tert-butylphe-
nol (around 30–40%), acidified N-substituted imidazoles
(around 20%) and 2-(1,3,5-tri-tert-butyl-4-oxo-2,5-cyclo-
hexadien-1-oxy)ethanol (around 10%) [11,12]. The yield
with 1-2,6-di-isopropylphenylimidazole was too low to iso-
late the objective compound. Although the yield of this
reaction is somewhat low, the routine is simple and purifi-
cation is easy, and it can be used for the synthesis of com-
O
OH
tBu
But
But
N
N
EG
Fig. 1. Molecular structure of 4b, showing one of the two crystallograph-
+ N
N
110oC
˚
ically independent molecules in the unit cell. Selected bond lengths (A) and
Br
tBu
angles (ꢁ): O(1)–C(11) 1.365(6), N(1)–C(1) 1.345(6), N(1)–C(3) 1.380(7),
N(1)–C(4) 1.474(7), N(2)–C(1) 1.325(7), N(2)–C(2) 1.379(6), N(2)–C(10)
1.445(6), C(2)–C(3) 1.360(7), C(1)–N(1)–C(4) 127.6(5), C(1)–N(2)–C(10)
125.1(4), N(2)–C(1)–N(1) 108.7(4).
tBu
Br
3
1
Scheme 2.

2094
H. Ren et al. / Journal of Organometallic Chemistry 692 (2007) 2092–2098
˚
OH
tBu
[2.0819(17) A] bonds are slightly longer than that in the
But
analogous allyl palladium NHC enolate complex [Pd–
C(allyl): 2.113(4), 2.133(5), 2.204(4) A; Pd–C(carbene):
2.022(4) A; Pd–O: 2.062(3) A] [5b]. In comparison with
the carbene precursor 4b, the notable feature of 5b is the
R
N
N
[(ally)PdCl]2
2n-BuLi
THF
˚
˚
˚
Br
4
˚
shortened C–O bond [from 1.365(6) to 1.322(3) A] and
the lengthened and averaged C(carbene)–N bonds [from
˚
1.325(7), 1.345(6) to 1.363(3), 1.359(3) A], indicating the
5a, R= t-Bu
5b, R= Cy
Pd
R
strong complexation between Pd and the [C, O] chelating
NHC ligand.
O
N
But
N
(Mes)
5c,R
=
It is well known that palladium complexes are excellent
catalysts for Suzuki–Miyaura coupling [18] and Buchward–
Hartwig amination [19]. Some of the N-heterocyclic car-
bene allylic palladium complexes were found with extre-
mely high activities [14,20]. Introduction of the chelating
anionic oxygen to the NHC allylic palladium complexes
may lead to some different results. So a series of Suzuki–
Miyaura coupling reactions was tried with complexes 5a–
c as catalysts. Under the typical conditions as for the
NHC allylic palladium catalysts, bromobenzene could be
coupled with phenyl boronic acid in the presence of
tBu
Scheme 4.
The NMR spectra of 5a–c show five proton and three
carbon distinct resonances for the allyl ligand, in agree-
ment with asymmetric structures of the complexes [16].
The signals of carbene carbons are typical singlets at
around 180 ppm (175.4 for 5a, 175.6 for 5b, and 178.6
for 5c). The chemical shifts are very similar with the known
g3-allylic palladium Schiff base complexes [17] and g3-
allylic palladium NHC halide complexes [5b,14]. The
molecular structure of 5b was also determined by single
crystal X-ray diffraction analysis (Fig. 2). Similar to the
other (allyl)Pd(NHC) complexes [5b,14], a square-planar
coordination geometry is observed. The allyl carbon trans
to the carbene also shows significant lengthening
i
1.1 equiv of KOtBu using 1 mol% of 5 in 1 mL of PrOH
at 80 ꢁC (Table 1). All reactions nearly finished in 4 h. This
indicates that complexes 5 are efficient catalysts for
Suzuki–Miyaura coupling reaction. Similar to the NHC
allylic palladium catalysts [14b], the aryl substituted com-
plex 5c is more effective than the alkyl substituted ana-
logues 5a and 5b. This can be attributed to the poor
stability of the [(NHC)Pd(0)] intermediate for 5a and 5b,
because the catalyst decomposition (Pd black formation)
was observed in the cases of 5a and 5b. Addition of PPh3
may stabilize the [(NHC)Pd(0)] intermediate and increase
the yield. The coupling of different substrates with phenyl
boronic acid was also studied with 5c as catalyst (Table
2). For aryl bromide and the active aryl chloride, good
results were obtained. But for chlorobenzene only poor
yield was obtained. Addition of PPh3 could promote the
reaction, but the yield was still low. This indicates that this
˚
(0.106 A) relative to the allyl carbon trans to the phenolate.
But the bonding between the allyl and palladium [Pd–
C(allyl): 2.076(12), 2.131(3), 2.182(12) A] in 5b is shorter,
while the Pd–C(carbene) [2.033(2) A] and Pd–O
˚
˚
Table 1
Effect of the substitution at the imidazolyl moiety on precatalyst and PPh3
performance in the Suzuki–Miyaura coupling of a simple substratea
[Pd] (1 mol%)
Br + (HO)2B
KOtBu/iPrOH
80 C, 4 h
Entry
[Pd]
Yieldb (%)
1
2
3
4
5
6
a
5a
5a + PPh3
5b
81c
>99
82c
>99
>99
>99
d
˚
Fig. 2. Molecular structure of 5b. Selected bond lengths (A) and angles
(ꢁ): O(1)–C(1) 1.322(3), N(1)–C(2) 1.438(3), N(1)–C(7) 1.363(3), N(1)–C(8)
1.384(3), N(2)–C(7) 1.359(3), N(2)–C(9) 1.385(3), N(2)–C(10) 1.468(3),
C(8)–C(9) 1.338(3), Pd(1)–C(7) 2.033(2), Pd(1)–O(1) 2.0819(17), Pd(1)–
C(24) 2.076(12), Pd(1)–C(25) 2.131(3), Pd(1)–C(26) 2.182(12), C(24)–
C(25) 1.385(10), C(25)–C(26) 1.388(9), C(24)–Pd(1)–C(26) 68.1(3), C(7)–
Pd(1)–O(1) 85.78(8), C(1)–O(1)–Pd(1) 118.58(14), O(1)–C(1)–C(2)
122.1(2), C(1)–C(2)–N(1) 119.36(19), C(7)–N(1)–C(2) 126.08(19), N(1)–
C(7)–Pd(1) 120.96(16), N(2)–C(7)–N(1) 104.61(19), C(7)–N(2)–C(10)
124.5(2), C(24)–C(25)–C(26) 118.7(7).
5b + PPh3
5c
5c + PPh3
Reaction conditions: phenyl bromide (1 mmol), boronic acid
(1.5 mmol), [Pd] (1 mol %), KOtBu (1.1 mmol), tech grade PrOH (1 mL).
b
i
Isolated yield, average of two runs.
c
Catalyst decomposed.
PPh3 (1 mmol).
d

H. Ren et al. / Journal of Organometallic Chemistry 692 (2007) 2092–2098
2095
Table 2
kind of o-hydroxyaryl-substituted NHC ligands is not
advantaged for Suzuki–Miyaura coupling reaction, in com-
parison with the NHC allylic palladium catalysts.
In the most recognized mechanism of Suzuki–Miyaura
coupling reaction catalyzed by (allyl)Pd(NHC)Cl, the acti-
vation of the Pd center may occur through a nucleophilic
attack at the allyl moiety or through a chloride/alkoxide
r-metathesis followed by reductive elimination, liberating
a [(NHC)Pd(0)] species [16b,20,21] (Scheme 5). In our
cases, the chelating anionic oxygen is a much weaker leav-
ing group than chloride. So the activation process is
harder than that for (allyl)Pd(NHC)Cl and leads to the
low yield.
Suzuki reaction of aryl halides catalyzed by 5ca
[Pd] (1 mol%)
Br + (HO)2B
KOtBu/iPrOH
R
R
80 C
Entry ArX
[Pd]
Product
Time
(h)
Yieldb
(%)
1
2
5c
4
96
Br
5c
4
89
Br
3. Conclusions
3
5c
5c
5c
5c
4
2
4
6
6
>99
>99c
98
MeO
Br
MeO
O2N
O2N
In conclusion, a facile protocol for the synthesis of o-
hydroxyaryl substituted carbene is presented. Allylic palla-
dium complexes 5a–c bearing such ligands were synthesized
and used as efficient catalysts for Suzuki–Miyaura coupling
reaction of aryl bromide.
4
O2N
Br
Cl
5
O2N
4. Experimental
6
14d
4.1. General procedures and starting materials
Cl
Cl
Schlenk and vacuum line techniques were employed for
all manipulations of air- and moisture-sensitive com-
pounds. All solvents were distilled from appropriate drying
26d
e
7
5c + PPh3
agents under argon before use. H and 13C NMR spectra
1
a
Reaction conditions: phenyl bromide (1 mmol), boronic acid
(1.5 mmol), [Pd] (1 mol%), KOtBu (1.1 mmol), tech grade PrOH (1 mL).
i
were recorded on a VARIAN 400 instrument. Elemental
analyses were performed on a Perkin–Elmer 240C ana-
lyzer. Allyl palladium chloride dimer [22], 1-substituted
imidazoles [23] and 1 [24] were prepared according to the
literature methods.
b
Isolated yield, average of two runs.
At room temperature.
Catalyst decomposed.
c
d
e
PPh3 (1 mmol).
4.2. General procedures for preparation of o-hydroxyaryl
substituted imidazolium salts 4a–c
O
4-Bromo-2,4,6-tri-tert-butyl-2,5-cyclohexadien-1-one (6.83 g,
20 mmol), ethylene glycol (1.24 g, 20 mmol), and N-substituted
imidazole (40 mmol) were heated in an oil bath at 135 ꢁC
for 8 h. Then 50 mL of HBr aqueous solution (3 N) was
added and stirred violently. After filtration, the solid was
washed with water (3 · 10 mL) and hexane (3 · 20 mL) to
give the o-hydroxyaryl substituted imidazolium salts 4 as
white powder. They were pure enough for H NMR Spec-
tra characterization. Recrystallization from CH2Cl2/hex-
ane made the further purification for element analysis.
K
Pd
R
Pd
R
O
N
O
N
But
N
But
N
tBu
tBu
1
KOtBu
O
Pd0
R
O
K
O
N
4.2.1. Compound 4a (R = t-Bu)
Yield 19%, mp: 255–256 ꢁC. Anal. Calc. for
C21H33N2OBr: C, 61.61; H, 8.12; N, 6.84. Found: C,
Pd
R
But
N
K
But
O
N
N
1
61.29; H, 8.01; N, 6.35%. H NMR (400 MHz, CDCl3): d
tBu
9.50 (s, 1H, CcarbeneH), 7.55 (s, 1H, Ar–H), 7.46 (d, 1H,
im–CH, J = 2.29 Hz), 7.38 (s, 1H, Ar–H), 7.01 (d, 1H,
im–CH, J = 2.29 Hz), 1.81 (s, 9H, C(CH)3), 1.46 (s, 9H,
tBu
Scheme 5.

2096
H. Ren et al. / Journal of Organometallic Chemistry 692 (2007) 2092–2098
C(CH)3), 1.30 (s, 9H, C(CH)3). MS (SCI): m/z = 329
(M+ÀBr).
(d, 1H, CallyH, J = 13.7 Hz), 3.20 (d, 1H, CallyH,
J = 6.56 Hz), 2.29 (d, 1H, CallyH, J = 11.7 Hz), 2.18–1.52
(m, 10H, (CH2)5), 1.49 (s, 9H, C(CH)3), 1.31 (s, 9H,
C(CH)3). 13C NMR (400 MHz, CDCl3): d175.6, 157.1,
141.1, 134.4, 130.1, 121.9, 119.4, 116.8, 115.6, 115.0, 69.9,
60.4, 41.6, 35.7, 34.1, 34.0, 31.8, 29.6, 25.7, 25.3.
4.2.2. Compound 4b (R = Cy)
Yield 18%, mp: 236–237 ꢁC. Anal. Calc. for
C23H35N2OBr: C, 63.44; H, 8.10; N, 6.43. Found: C,
1
63.49; H, 8.54; N, 6.92%. H NMR (400 MHz, CDCl3): d
9.48 (s, 1H, CcarbeneH), 7.52 (s, 1H, Ar–H), 7.46 (d, 1H,
im–CH, J = 2.36 Hz), 7.37 (s, 1H, Ar–H), 7.01 (d, 1H,
im–CH, J = 2.36 Hz), 4.38 (m, 1H, NCH(CH2)5), 2.48–
1.65 (m, 10H, (CH2)5), 1.44 (s, 9H, C(CH)3), 1.30 (s, 9H,
C(CH)3). MS (SCI): m/z = 355 (M+ÀBr).
4.3.3. Compound 5c (R = Mes)
Yield 95%, mp: 209–210 ꢁC (dec). Anal. Calc. for
C29H38N2OPd: C, 64.86; H, 7.13; N, 5.22. Found: C,
1
64.81; H, 7.13; N, 5.22. H NMR (400 MHz, CDCl3): d
7.64 (s, 1H, Ar–H), 7.23 (m, 1H, im–CH,), 7.14 (m, 1H,
im–CH,), 7.00 (s, 1H, Ar–H), 6.97 (s, 2H, Ar–H), 4.96
(m, 1H, CallyH), 4.04 (d, 1H, CallyH, J = 7.48 Hz), 3.06
(d, 1H, CallyH, J = 13.6 Hz), 2.36 (s, 3H, Ar–CH3), 2.19
(d, 1H, CallyH, J = 5.00 Hz), 2.10 (s, 3H, Ar–CH3), 2.02
(s, 3H, Ar–CH3), 1.93 (d, 1H, CallyH, J = 6.01 Hz), 1.50
(s, 9H, C(CH)3), 1.34 (s, 9H, C(CH)3); 13C NMR
(400 MHz, CDCl3): d178.6, 157.2, 141.4, 139.0, 137.2,
135.8, 135.6, 134.4, 129.4, 128.7, 122.2, 121.2, 119.2,
115.9, 115.2, 68.4, 42.1, 35.8, 34.1, 31.8, 29.7, 21.1, 18.0,
17.9.
4.2.3. Compound 4c (R = Mes)
Yield 20% yield, mp: 278–279 ꢁC. Anal. Calc. for
C26H35N2OBr: C, 66.23; H, 7.48; N, 5.94. Found: C,
1
66.17; H, 7.86; N, 6.15%. H NMR (400 MHz, CDCl3): d
10.01 (s, 1H, CcarbeneH), 7.65 (m, 1H, Ar–H), 7.52 (d,
1H, im–CH, J = 2.10 Hz), 7.31 (m, 1H, Ar–H), 7.11 (d,
1H, im–CH, J = 2.10 Hz), 7.04 (s, 2H, Ar–H), 2.35
(s, 3H, Ar–CH3), 2.26 (s, 6H, Ar–CH3), 1.49 (s, 9H,
C(CH)3), 1.34 (s, 9H, C(CH)3). MS (SCI): m/z = 391
(M+ÀBr).
4.4. General procedure of Suzuki–Miyaura coupling
reactions
4.3. General procedures for preparation of chelating
N-heterocyclic carbene palladium complexes 5a–c
To a Schlenk bottle with a magnetic stir bar and a sep-
tum were added in turn catalyst (1 mmol%), potassium
tert-butoxide (1.1 mmol, 124 mg), boronic acid (1.5 mmol,
183 mg) and aryl halide (1 mmol, if solid). Then the system
A solution of n-BuLi (1.7 M, 2.0 mmol) in hexane was
added to the suspension of imidazolium salt (1.0 mmol)
in THF. After stirring for 30 min, [Pd(allyl)Cl]2 (0.18 g,
0.5 mmol) was added and the resulting orange solution
was stirred overnight. After removal of solvents in vacuum,
the residue was extracted with CH2Cl2 and filtered through
Celite. Removal of CH2Cl2 gave the object complex in high
yield.
Table 3
Crystal data and summary of X-ray data collection for 4b and 5b
4b Æ 0.75H2O
5b
Formula
Fw
C
448.95
23H36.5BrN2O1.75 C26H38N2OPd
500.98
294(2)
0.71073
Triclinic
4.3.1. Compound 5a (R = t-Bu)
Yield 90%, mp: >250 ꢁC (dec). Anal. Calc. for
C24H36N2OPd: C, 60.69; H, 7.64; N, 5.90. Found: C,
T (K)
113(2) K
0.71070
Monoclinic
P121/a1
11.176(2)
28.222(5)
14.987(3)
90
90.392(3)
90
4726.9(15)
8
˚
k (A)
Crystal system
Space group
1
ꢀ
60.51; H, 7.41; N, 5.84%. H NMR (400 MHz, CDCl3): d
P1
˚
a (A)
9.8536(13)
9.9100(13)
14.8527(18)
82.761(2)
86.366(2)
60.250(2)
1249.2(3)
2
7.24 (m, 2H, Ar–H), 7.18 (d, 1H, im–CH,J = 2.58 Hz),
7.02 (d, 1H, im–CH,J = 2.58 Hz), 5.32 (m, 1H, CallyH),
4.25 (dd, 1H, CallyH,J = 2.05, 7.50 Hz), 3.28–3.20 (m, 2H,
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
C
allyH), 2.35 (d, 1H, CallyH,J = 11.8 Hz), 1.76 (s, 9H,
C(CH)3), 1.48 (s, 9H, C(CH)3), 1.32 (s, 9H, C(CH)3). 13C
NMR (400 MHz, CDCl3): d175.4, 157.6, 140.6, 134.4,
132.1, 122.3, 118.9, 118.4, 116.3, 114.6, 69.8, 57.8, 48.0,
35.6, 34.0, 31.8, 31.5, 29.8.
3
˚
V (A )
Z
Dcalc (g cmÀ3
)
1.262
1.757
1900
1.332
0.761
524
l (mmÀ1
F(000)
)
4.3.2. Compound 5b (R = Cy)
Yield 90%, mp: >250 ꢁC (dec). Anal. Calc. for
C26H38N2OPd: C, 62.33; H, 7.64; N, 5.59. Found: C,
Crystal size (mm)
h Range (ꢁ)
Number of reflections collected
Number of independent
reflections/Rint
0.32 · 0.20 · 0.10
1.96–25.00
35897
0.28 · 0.20 · 0.12
2.38–26.36
7103
8309/0.1359
5041/0.0164
1
62.21; H, 7.68; N, 5.51%. H NMR (400 MHz, CDCl3): d
7.38 (d, 1H, Ar–H, J = 1.73 Hz), 7.18 (d, 1H, im–CH,
J = 2.44 Hz), 7.08 (d, 1H, Ar–CH, J = 1.84 Hz), 7.03 (d,
1H, im–CH, J = 2.44 Hz), 5.26 (m, 1H, CallyH), 4.36 (m,
1H, NCH(CH2)5), 4.21 (d, 1H, CallyH, J = 7.47 Hz), 3.30
Number of parameters
Goodness-of-fit on F2
R1, wR2 [I > 2r(I)]
R1, wR2 (all data)
520
1.071
0.0722, 0.1791
0.0915, 0.1929
305
1.028
0.0285, 0.0711
0.0339, 0.0747

H. Ren et al. / Journal of Organometallic Chemistry 692 (2007) 2092–2098
2097
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was degassed and charged with argon three times.
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4.5. Crystallographic studies
´
´
(d) E. Mas-Marza, M. Poyatos, M. Sanau, E. Peris, Organometallics
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Single crystals of 4b and 5b suitable for X-ray diffraction
were obtained from CH2Cl2/hexane solution. Data collec-
tion was performed on Rigaku 007 with Saturn 70 CCD
(for 4b) or Bruker Smart 1000 (for 5b) diffractometer, using
graphite-monochromated Mo Ka radiation (x–2h scans).
Semi-empirical absorption corrections were applied for
all complexes. The structures were solved by direct meth-
ods and refined by full-matrix least-squares. All calcula-
tions were done using the SHELXL-97 program system. The
crystal data and summary of X-ray data collection are pre-
sented in Table 3.
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Acknowledgments
´
(m) V. Jurcˇık, M. Gilani, R. Wilhelm, Eur. J. Org. Chem. (2006)
5103;
We are grateful to NSFC (20421202, 20474031),
SRFDP (20050055008), the 111 Project (B06005), and the
Program for New Century Excellent Talents in University
(NCET-04-0229) for financial support.
(n) Z. Wang, H. Sun, H. Yao, Q. Shen, Y. Zhang, Organometallics
25 (2006) 4436;
(o) D. Zhang, H. Kawaguchi, Organometallics 25 (2006) 5506;
(p) M. Chen, H. Sun, W. Li, Z. Wang, Q. Shen, Y. Zhang, J.
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Appendix A. Supplementary material
(q) Z. Wang, H. Sun, H. Yao, Y. Yao, Q. Shen, Y. Zhang, J.
Organomet. Chem. 691 (2006) 3383;
CCDC 634034 and 631539 contain the supplementary
crystallographic data for 4b and 5b. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: +(44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
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