Palladacyclic complexes bearing CNN-type ligands as catalysts in the Heck reaction

Article abstract of DOI:10.1039/b404798b

Preparations of novel unsymmetrical, tridentate nitrogen ligand precursors, PhN=C(CMe₂)(NPh)C=N(CH₂)₂NMe₂ (1) and PhN=C(CMe₂)(NPh)C=N(CH₂)Py (2), are described. Treatment of 1 with 1 molar equiv. (COD)PdCl₂ in the presence of NEt₃ or with 1 molar equiv. Pd(OAc)₂ affords orthometallated palladium(II) complexes, [PhN=C(CMe₂)-(N- η¹-Ph)C=N(CH₂)₂NMe₂]PdX (X = Cl (3); X = OAc (4)), respectively. Compound 3 can be yielded via the reaction of 4 with an excess of LiCl in methanol. Treatment of 2 with 1 molar equiv. of (COD)PdCl₂, Pd(OAc)₂ or Pd(TFA)₂ affords orthometallated palladium(II) complexes, [PhN=C(CMe₂)(N- η¹-Ph)C=NCH₂Py]PdX (X = Cl (5); X = OAc (6); X = TFA (7)), respectively. The crystal and molecular structures are reported for compounds 2, 3, 5 and 6. The application of these novel palladacyclic complexes to the Heck reaction with aryl halide substrates was examined.

Full text of DOI:10.1039/b404798b

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F U L L P A P E R
Palladacyclic complexes bearing CNN-type ligands as catalysts in
the Heck reaction
Chi-Tien Chen,* Yi-Sen Chan, Yi-Ren Tzeng and Ming-Tsz Chen
Department of Chemistry, National Chung-Hsing University, Taichung 402, Taiwan,
Republic of China. E-mail: ctchen@mail.nchu.edu.tw
Received 31st March 2004, Accepted 9th July 2004
First published as an Advance Article on the web 3rd August 2004
Preparations of novel unsymmetrical, tridentate nitrogen ligand precursors, PhNC(CMe2)(NPh)CN(CH2)2NMe2
(1) and PhNC(CMe2)(NPh)CN(CH2)Py (2), are described. Treatment of 1 with 1 molar equiv. (COD)PdCl2 in the
presence of NEt3 or with 1 molar equiv. Pd(OAc)2 affords orthometallated palladium(II) complexes, [PhNC(CMe2)-(N-
1-Ph)CN(CH2)2NMe2]PdX (X = Cl (3); X = OAc (4)), respectively. Compound 3 can be yielded via the reaction of 4
with an excess of LiCl in methanol. Treatment of 2 with 1 molar equiv. of (COD)PdCl2, Pd(OAc)2 or Pd(TFA)2 affords
orthometallated palladium(II) complexes, [PhNC(CMe2)(N-1-Ph)CNCH2Py]PdX (X = Cl (5); X = OAc (6); X = TFA
(7)), respectively. The crystal and molecular structures are reported for compounds 2, 3, 5 and 6. The application of these
novel palladacyclic complexes to the Heck reaction with aryl halide substrates was examined.
Introduction
Results and discussion
Transition metal-catalysed coupling reactions are the most pow-
erful and versatile methods in organic chemistry and have been
extensively studied since they are popular for the formation of
various coupling products.1 Palladium complexes seem to be active
and suitable in preparing the target compounds due to their easy
preparation and commercial availability. Catalysts can be either
prepared in situ from commercially available palladium compounds
and additives, or from the isolated palladacycles.2–16 Among these
complexes, palladacycles bearing metallated carbon atoms and da-
tive group(s) are among the most active catalyst precursors for the
promotion of such reactions.
Some nitrogen-containing palladacycles capable of mediating
C–C coupling reactions have been reported. These complexes usu-
ally form dinuclear species with bridged ligands or mononuclear
species in the presence of neutral dative group.6–17 Except for
pincer complexes,7,18 unusual mononuclear palladacycles bearing
amine or/and imine tridentate ligands have been reported.19–21 We
report herein the synthesis and characterisation of novel pallada-
cycles supported by unsymmetrical CNN-type ligands in mono-
nuclear species. Their catalytic activities toward the Heck reaction
are investigated.
Syntheses and characterisation of ligand precursors and
palladacycles
Ligand precursors 1 and 2 were prepared from the reaction of 2,2-
dimethyl-N,N′-diphenylpropanediimidoyldichloridewith1.1equiv-
alents of N,N-dimethylethyleneamine or 2-aminomethylpyridine in
the presence of 2.5 equivalents of NEt3. A summary of syntheses
and proposed structures is shown in Scheme 1. The spectroscopic
data of 1 and 2 indicate two phenyl rings in each compound having
different environments. The X-ray structure of 2 features a diimine
compound bearing a four-membered heterocycle. One phenyl
ring attaches to the nitrogen atom on the heterocycle whereas the
other one attaches to one nitrogen atom of the imine groups. The
molecular structure is shown in Fig. 1, and selected bond lengths
and angles are listed in Table 1. The C(1)–N(1) (1.253(2) Å) and
C(3)–N(3) (1.257(2) Å) bond lengths are consistent with significant
double bond character and the bond angles around imino C and
N atoms are indicative of sp2 centres. A plausible mechanism for
the formation of both ligand precursors is proposed in Scheme 2.
The first step is the elimination of one equivalent of HCl by base,
followed by the shift of a proton from the amine group to the
nitrogen atom on the imine group. The cyclisation is then achieved
Scheme 1
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 2 6 9 1 – 2 6 9 6
2 6 9 1

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Table 1 Selected bond lengths (Å) and angles (°) for 2
Table 2 Selected bond lengths (Å) and angles (°) for 3
N(1)–C(1)
N(1)–C(6)
N(3)–C(18)
N(2)–C(1)
N(4)–C(11)
C(2)–C(3)
C(16)–C(17)
1.253(2)
1.459(2)
1.428(2)
1.4139(19)
1.338(2)
1.534(2)
1.372(2)
N(3)–C(3)
N(2)–C(12)
N(2)–C(3)
N(4)–C(7)
C(1)–C(2)
C(12)–C(17)
1.257(2)
1.4152(18)
1.4018(19)
1.336(2)
1.541(2)
1.385(2)
Pd–N(1)
Pd–C(15)
2.002(2)
2.025(3)
Pd–N(2)
Pd–Cl
2.195(3)
2.3181(8)
N(1)–Pd–C(15)
C(15)–Pd–Cl
C(15)–Pd–N(2)
93.20(104)
94.39(8)
174.43(9)
N(1)–Pd–N(2)
N(2)–Pd–Cl
N(1)–Pd–Cl
81.86(9)
90.81(7)
170.20(7)
2.4583(5) Å) found in palladacycles14–16,21,22,25–27 and those
(2.2703(16)–2.301(4) Å) found in palladium imino complexes.29–32
Disorder is found for the carbon atoms C7 and C7′ on the pendant
group. Treatment of 1 with 1 molar equivalent of Pd(OAc)2 at room
temperature affords complex 4 as a white solid. The spectroscopic
and elemental analysis data are consistent with a structure similar to
3 with a difference of coordinating OAc instead of Cl.
C(1)–N(1)–C(6)
C(3)–N(2)–C(1)
C(1)–N(2)–C(12)
N(1)–C(1)–C(2)
N(3)–C(3)–N(2)
N(2)–C(3)–C(2)
N(1)–C(6)–C(7)
117.80(14)
93.39(11)
132.18(13)
140.47(15)
128.76(14)
91.87(12)
112.27(14)
C(3)–N(3)–C(18)
C(3)–N(2)–C(12)
N(1)–C(1)–N(2)
N(2)–C(1)–C(2)
N(3)–C(3)–C(2)
C(3)–C(2)–C(1)
118.70(13)
134.20(13)
128.37(14)
91.14(11)
139.36(14)
83.56(11)
Fig. 1 Molecular structure of compound 2. Hydrogen atoms on the carbon
atoms are omitted for clarity.
Fig. 2 Molecular structure of complex 3. Hydrogen atoms on the carbon
atoms omitted for clarity.
Reactions of 2 with 1 molar equiv. of (COD)PdCl2, Pd(OAc)2
or Pd(TFA)2 afford orthometallated palladium(II) complexes,
[PhNC(CMe2)(N-1-Ph)CNCH2Py]PdX (X = Cl (5); X = OAc
(6); X = TFA(7)), respectively. Similar to compound 3, an additional
tertiary carbon corresponding to metallated carbon was found in the
13C{1H} NMR spectrum of each complex. Suitable crystals of 5 and
6 for structural determination were obtained from CH2Cl2–hexane
solution. The molecular structures of 5 and 6 are shown in Figs. 3
and 4, and selected bond lengths and angles are listed in Tables 3
and 4. Basically, compound 5 is quite similar to compound 3 with a
different pendant group CH2Py instead of CH2CH2NMe2 for 3. The
palladium metal centre is coordinated with a similar mode as in 3
except for one nitrogen atom from pyridine instead of one amine
nitrogen atom. Compound 6 is quite similar to compound 5 but
with coordinated OAc instead of Cl for 5. Bond lengths and bond
angles are similar to those discussed above. The bond lengths of
Pd–NPy (2.1244(17) Å for 5 and 2.101(2) Å for 6) are slightly longer
than those (2.009(3)–2.037(2) Å) found in the literature.30–34 The
bond length of Pd–OOAc (2.0558(18) Å) in 6 is comparable to those
(2.027(9)–2.090(1) Å) found in the literature.26–28
Scheme 2 Plausible mechanism for preparing the ligand precursors.
by removal of the other equivalent of HCl with another equivalent
of base to form the target compound.
Treatment of 1 with 1 molar equivalent of (COD)PdCl2 in
the presence of NEt3 at room temperature yields complex 3 as
a pale-yellow solid. One more tertiary carbon was found in the
region of the phenyl ring based on the 13C{1H} NMR spectrum
which indicates a metallated carbon atom being created during the
reaction. Complex 3 can be synthesized by the reaction of 4 with
an excess of lithium chloride in methanol at room temperature.20
Suitable crystals of 3 for structural determination were obtained
from CH2Cl2–hexane solution. The molecular structure is shown
in Fig. 2 and selected bond lengths and angles are listed in Table 2.
The bond angles (from 81.86(9) to 94.39(8)°) around the Pd metal
centres indicate a complex having a slightly distorted square planar
geometry, in which the palladium metal centre is coordinated with
one imine nitrogen atom, one amine nitrogen atom, one metallated
carbon atom, and one chloride atom. The small N(1)–Pd–N(2) angle
(81.86(9)°) results from the relatively small bite size of the pendant
group. The bond length of Pd–Cmetallated (2.025(3) Å) is within those
(1.954(3)–2.104(4) Å) found in palladacycles with metallated
carbon.15,16,20–27 Similarly, the bond length of Pd–NCN (2.002(2) Å)
is within those (1.960(6)–2.122(3) Å) found in palladacycles15,16,20–
22,25 and those (2.0183(10)–2.077(12) Å) found in palladium imino
complexes.28–32 The bond length of Pd–Namine (2.195(3) Å) is close
to those (2.059(3)–2.196(4) Å) found in palladacycles.14–16,21,23,24,26,27
The bond length of Pd–Cl (2.3181(8) Å) is within those (2.153(8)–
Fig. 3 Molecular structure of complex 5. Hydrogen atoms on the carbon
atoms are omitted for clarity.
2 6 9 2
D a l t o n T r a n s . , 2 0 0 4 , 2 6 9 1 – 2 6 9 6

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Table 3 Selected bond lengths (Å) and angles (°) for 5
from the leaving nature of the anionic co-ligand, X. Due to the bet-
ter activity and solubility of 7, lower catalyst concentrations were
investigated with 7 using catalyst/substrate ratios from 10−3 to 10−5
(entries 17–20). The reaction gave degrees of conversion to 98%
within 24 h using a catalyst/substrate ratio of 10−5. Compared with
some Cmetallated–Npy palladacycles,11 Cmetallated–Namine palladacycles,6,17
Cmetallated–Nimine palladacycles,6 Cmetallated–Nimine–Nimine pallada-
cycles,20 diimino palladium complexes,28 and dipyridyl palladium
complexes,35,36 the new CNN-type palladacycles show comparable
catalytic activities toward the Heck coupling reaction. In some cases
they exhibit even higher activities than for the others.
Pd–N(1)
Pd–C(13)
1.9975(16)
2.019(2)
Pd–N(2)
Pd–Cl
2.1244(17)
2.3334(6)
N(1)–Pd–C(13)
C(13)–Pd–Cl
C(13)–Pd–N(2)
93.77(8)
94.95(6)
172.94(7)
N(1)–Pd–N(2)
N(2)–Pd–Cl
N(1)–Pd–Cl
79.89(7)
91.68(5)
169.45(5)
Table 4 Selected bond lengths (Å) and angles (°) for 6
Pd(1)–N(3)
Pd(1)–C(17)
1.988(2)
1.995(3)
Pd(1)–N(4)
Pd(1)–O(1)
2.101(2)
2.0558(18)
In summary, novel palladacycles, phosphine-free imine
complexes, have been prepared and demonstrated catalytic
activities toward the Heck C–C coupling reaction. Their catalytic
activities are determined not only by the coordination ability of the
pendant groups but also by the leaving nature of the anionic co-
ligands. Under optimised conditions, complex 7 shows comparable
activity to those of existing nitrogen-based palladacycle systems.
Preliminary studies on fine-tuning of ligands and further application
of metal complexes to the catalytic reactions are currently being
undertaken.
N(3)–Pd(1)–C(17)
C(17)–Pd(1)–O(1)
C(17)–Pd(1)–N(4)
94.51(10)
90.69(9)
174.25(8)
N(3)–Pd(1)–N(4)
N(4)–Pd(1)–O(1)
N(3)–Pd(1)–O(1)
80.06(9)
94.70(8)
174.69(7)
Experimental
All manipulations were carried out under an atmosphere of di-
nitrogen using standard Schlenk-line or drybox techniques. Solvents
were refluxed over the appropriate drying agent and distilled prior
to use. Deuterated solvents were dried over molecular sieves.
1H and 13C{1H} NMR spectra were recorded either on Varian
Gemini-200 (200 MHz), Varian Mercury-400 (400 MHz) or Varian
Inova-600 (600 MHz) spectrometers in chloroform-d at ambient
temperature unless stated otherwise and referenced internally to
the residual solvent peak and reported as parts per million relative
to tetramethylsilane. Elemental analyses were performed by a
Elementar Vario ELIV instrument.
Fig. 4 Molecular structure of complex 6. Hydrogen atoms on the carbon
atoms are omitted for clarity.
Catalytic studies
The molecular structures of the palladacycles discussed above
exhibit similar structural features to the nitrogen-based catalysts
used for the carbon–carbon coupling reactions. Those results
encouraged us to examine the activity of those complexes toward
the Heck reaction (Scheme 3).
Aniline (Acros), dimethylmalonyl dichloride (TCI), PCl5
(RDH), 2-aminomethylpyridine (Acros), Pd(OAc)2, Pd(TFA)2 and
(COD)PdCl2 (Strem) were used as supplied. NEt3 and N,N-dimethyl-
ethyleneamine were dried over CaH2 and distilled before use.
Preparations
2,2-Dimethyl-N,N′-diphenylmalonamide. To a solution of ani-
line (2.6 ml, 29 mmol) in 60 ml diethyl ether, a dilute solution of
dimethylmalonyl dichloride (0.9 ml, 7 mmol) in 65 ml diethyl ether
was added at 0 °C. The reaction mixture was allowed to warm to
room temperature. After 4 h of stirring, the white suspension was
filtered. The residue was washed with 60 ml of water followed by
20 ml diethyl ether to afford a white solid. Yield, 1.89 g, 96%. 1H
NMR (400 MHz):  1.70 (s, CH3, 6H), 7.14 (m, p-Ph, 2H), 7.34 (m,
m-Ph, 4H), 7.54 (m, o-Ph, 4H), 8.48 (s, NH, 2H). 13C{1H} NMR
(150 MHz):  24.2 (s, C(CH3)2), 50.8 (s, tert-C(CH3)2), 120.3, 124.8,
129.0 (o, m, p-C6H5), 137.3 (s, Cipso–C6H5), 171.5 (s, CO). Anal.
Calc. for C17H18N2O2: C, 72.32; H, 6.43; N, 9.92. Found: C, 72.59;
H, 6.27; N, 9.82%.
Scheme 3 Application of the palladacycles in the Heck reaction.
In order to investigate the catalytic activity, optimised conditions
using the coupling of 4-bromoacetophenone with styrene catalysed
by 5 were conducted. Selected results are listed in Table 5. The rate
of the Heck reaction is solvent-dependent with N,N-dimethylacet-
amide (DMA) being the choice after several trials with THF, toluene
and DMA (entries 3–11). For the choice of a base, we surveyed
K3PO4, Cs2CO3 and KF (entries 5, 8 and 11). Finally, we found that
use of 1 mol% 5 and 1.5 equiv. KF in DMA at 135 °C leads to the
best conversion within 3 h (entry 11). Excellent conversion is ob-
served with the same catalyst amount using 4-bromobenzaldehyde
under the optimised conditions (entry 12). The same conditions
were applied to examine the catalytic activity of 3, 4, 6 and 7. The
catalytic activities of 3 and 4, however, showed lower conversions.
The poor activities exhibited by 3 and 4 indicate that the pendant
group with Npy is better than that with Namine in this system. Excel-
lent conversions are observed within 2 h for 6 and 1.5 h for 7 (entries
13 and 15). Enhancements in activity are also observed using 4-
bromobenzaldehyde instead of 4-bromoacetophenone in both cases
(entries 14 and 16). When the catalytic activities are compared, it
can be seen that they fall in the order of 7 > 6 > 5. This could result
2,2-Dimethyl-N,N′-diphenylpropanediimidoyl
dichloride.
A mixture of 2,2-dimethyl-N,N′-diphenylmalonamide (5.82 g,
20.6 mmol) and PCl5 (9.0 g, 43.3 mmol) in 100 ml toluene was
stirred and refluxed for 3 h. The mixture was filtered when hot,
and the volatiles were removed under reduced pressure to afford
1
a yellow solid. Yield, 6.48 g, 99%. H NMR (400 MHz):  1.81
(s, CH3, 6H), 6.92 (m, o-Ph, 4H), 7.19 (m, p-Ph, 2H), 7.38 (m,
m-Ph, 4H). 13C{1H} NMR (150 MHz):  25.3 (s, C(CH3)2), 59.7
(s, tert-C(CH3)2), 119.8, 125.1, 128.9 (o, m, p-C6H5), 146.8, 148.5
(Cipso–C6H5 and CN). Anal. Calc. For C17H16N2Cl2: C, 63.96; H,
5.05; N, 8.78. Found: C, 63.91; H, 4.78; N, 8.33%.

PhN=C(CMe )(NPh)C=
N(CH2)2NMe2 (1). To a flask contain-
2

ing 2,2-dimethyl-N,N′-diphenylpropanediimidoyl dichloride (1.7 g,
5.3 mmol) and NEt3 (1.4 g, 13.3 mmol) in 20 ml CHCl3, was added
a dilute solution of N,N-dimethylethyleneamine (0.5 g, 5.9 mmol)
D a l t o n T r a n s . , 2 0 0 4 , 2 6 9 1 – 2 6 9 6
2 6 9 3

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Table 5 Heck coupling reaction catalysed by new palladium complexesa
Entry
Catalyst
Aryl halide
Base
Solvent
[Pd] (mol%)
T/°C
t/h
Conversionb (%)
Yieldc (%)
75
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
3
4
5
5
5
5
5
5
5
5
5
5
6
6
7
7
7
7
7
7
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromobenzaldehyde
4-Bromoacetophenone
4-Bromobenzaldehyde
4-Bromoacetophenone
4-Bromobenzaldehyde
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromoacetophenone
KF
KF
DMA
DMA
THF
Toluene
DMA
THF
Toluene
DMA
THF
Toluene
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
135
135
70
110
135
70
110
135
70
110
135
135
135
135
135
135
135
135
135
135
3
3
3
3
3
3
3
3
3
3
3
3
2
2
82
52
4
18
65
14
7
93
3
6
99
96
95
93
99
98
97
99
97
98
Cs2CO3
Cs2CO3
Cs2CO3
K3PO4
K3PO4
K3PO4
KF
KF
KF
KF
KF
KF
KF
KF
KF
KF
KF
KF
—
—
53
—
—
82
—
—
89
87
87
84
91
88
87
90
90
88
1.5
1.5
5
8
20
0.1
0.01
0.005
0.001
24
1
a Reaction conditions: 1 mmol aryl halide, 1.3 mmol styrene, 1.5 mmol base, 2 ml solvent. b Determined by H NMR. c isolated yield. (average of two
experiments).
in 10 ml CHCl3. After 24 h of stirring, the volatiles were pumped
off, and the residue was extracted with 30 ml hot hexane to afford
a pale-yellow solid. Yield, 0.88 g, 50%. H NMR (400 MHz): 
from CH2Cl2–hexane solution to afford a crystalline solid. Yield,
1
0.064 g, 88%. H NMR (600 MHz, CDCl3):  1.49 (s, C(CH3)2,
6H), 2.64 (t, CH2, 2H, 3JHH = 5.4 Hz), 2.75 (s, N(CH3)2, 6H), 3.71
(t, CH2, 2H, 3JHH = 6.0 Hz), 6.95 (d, 2H, 3JHH = 7.8 Hz), 6.98 (t, 1H,
3JHH = 6.6 Hz),7.12(t,1H,3JHH = 7.2 Hz),7.13(t,1H,3JHH = 7.2 Hz),
1
1.46 (s, C(CH3)2, 6H), 2.32 (s, N(CH3)2, 6H), 2.59 (m, CH2, 2H),
3.54 (m, CH2, 2H), 6.93 (d, o-Ph, 2H, 3JHH = 7.6 Hz), 7.07 (t, p-Ph,
1H, 3JHH = 7.2 Hz), 7.13 (t, p-Ph, 1H, 3JHH = 7.2 Hz), 7.29 (t, m-Ph,
2H, 3JHH = 7.6 Hz), 7.37 (t, m-Ph, 2H, 3JHH = 8.0 Hz), 8.27 (d, o-Ph,
2H, 3JHH = 8.0 Hz). 13C{1H} NMR (150 MHz):  21.5 (s, C(CH3)2),
45.9 (s, N(CH3)2), 47.1 (s, (CH2)2), 57.9 (s, tert-C(CH3)2), 61.0 (s,
(CH2)2), 119.2, 121.4, 123.2, 124.2, 128.54, 128.56 (o, m, p-C6H5),
137.2, 146.8, 158.0, 158.1 (two Cipso–C6H5 and two CN). Anal.
Calc. for C21H26N4: C, 75.41; H, 7.84; N, 16.75. Found: C, 75.28;
3
3
7.33 (t, 2H, JHH = 7.2 Hz), 8.08 (d, 1H, JHH = 7.8 Hz), 8.44 (d,
1H, JHH = 8.4 Hz). 13C{1H} NMR (150 MHz, CDCl3):  20.9 (s,
3
C(CH3)2), 48.4 (s, N(CH3)2), 48.9 (s, CH2), 56.8 (s, tert-C(CH3)2),
62.2 (s, CH2), 116.9, 120.8, 124.1, 124.7, 125.1, 129.0, 141.2 (seven
CH–C6H5), 125.9, 131.0, 145.6, 153.5, 157.8 (one 1-Ph, two
Cipso–C6H5 and two CN). Anal. Calc. for C21H25ClN4Pd: C, 53.06;
H, 5.30; N, 11.79. Found: C, 53.08; H, 5.17; N, 11.79%.
H, 7.43; N, 16.44%.
[PhNC(CMe2)(N-1-C6H4)CN(CH2)2NMe2]Pd(OAc) (4).
To a flask containing Pd(OAc)2 (0.17 g, 0.75 mmol) and 1 (0.31 g,
0.93 mmol), 20 ml THF was added at room temperature. After 16 h
of stirring, the yellow suspension was filtered to afford a white solid.
Yield, 0.24 g, 64%. 1H NMR (600 MHz, CDCl3):  1.46 (s, C(CH3)2,
6H), 2.19 (s, OC(O)CH3, 3H), 2.68 (t, CH2, 2H, 3JHH = 6 Hz), 2.72
(s, N(CH3)2, 6H), 3.69 (t, CH2, 2H, 3JHH = 6 Hz), 6.93 (m, 2H), 6.99
(m, 1H), 7.11 (m, 1H), 7.12 (m, 1H), 7.33 (m, 2H), 7.50 (m, 1H),

PhN=C(CMe2 )(NPh)C=N(CH2)Py (2). To a flask containing

2,2-dimethyl-N,N′-diphenylpropanediimidoyl dichloride (0.64 g,
2 mmol) and NEt3 (0.51 g, 5.0 mmol) in 20 ml CHCl3, was added
a dilute solution of 2-aminomethylpyridine (0.23 g, 2.2 mmol) in
10 ml CHCl3. After 20 h of stirring, the volatiles were pumped off,
and the residue was extracted with 30 ml hot hexane to afford a pale-
1
yellow solid. Yield, 0.37 g, 52%. H NMR (600 MHz):  1.47 (s,
3
C(CH3)2, 6H), 4.81 (s, CH2, 2H), 6.94 (d, o-Ph, 2H, 3JHH = 7.2 Hz),
7.08 (t, p-Ph or 3- or 4-Py, 1H, 3JHH = 7.2 Hz), 7.17 and 7.18 (two
overlapping t, p-Ph or 3- or 4-Py, 2H, 3JHH = 7.2 Hz), 7.29 (t, m-Ph,
2H, 3JHH = 7.2 Hz), 7.41 (t, m-Ph, 2H, 3JHH = 8.4 Hz), 7.59 (d, Py,
1H, 3JHH = 7.8 Hz), 7.72 (m, p-Ph or 3- or 4-Py, 1H), 8.39 (d, o-Ph,
8.05 (d, 1H, JHH = 7.2 Hz). 13C{1H} NMR (150 MHz, CDCl3): 
20.8 (s, C(CH3)2), 24.8 (s, O–C(O)–CH3) 48.3 (s, N(CH3)2), 48.8
(s, CH2), 56.7 (s, tert-C(CH3)2), 61.6 (s, CH2), 116.6, 120.9, 124.1,
124.5, 124.9, 128.9, 136.0 (seven CH–C6H5), 126.5, 131.1, 145.7,
153.6, 157.8 (one 1-Ph, two Cipso–C6H5 and two CN), 177.6 (s,
O–C(O)–CH3). Anal. Calc. for C23H28O2N4Pd: C, 55.37; H, 5.66;
N, 11.23. Found: C, 55.55; H, 6.57; N, 11.03%.
3
2H, JHH = 7.8 Hz), 8.53 (m, Py, 1H). 13C{1H} NMR (150 MHz):
 21.5 (s, C(CH3)2), 53.8 (s, CH2), 58.1 (s, tert-C(CH3)2), 119.3,
121.1, 121.4, 121.8, 123.4, 124.5, 128.7, 136.8, 148.9 (CH–C6H5
and CH–Py), 137.4, 146.7, 158.0, 159.6, 160.2 (two Cipso–C6H5, one
Cipso–Py and two CN).Anal. Calc. for C23H22N4: C, 77.94; H, 6.26;
N, 15.81. Found: C, 77.63; H, 6.52; N, 15.60%.
[PhNC(CMe2)(N-1-C6H4)CNCH2Py]PdCl (5). To a flask
containing (COD)PdCl2 (0.37 g, 1.30 mmol) in 20 ml CH2Cl2, a
solution of 2 (0.46 g, 1.30 mmol) in 10 ml CH2Cl2 was added at
room temperature. After 24 h of stirring, the yellow suspension was
filtered. The residue was washed with 20 ml toluene to afford a
yellow solid. Yield, 0.46 g, 71%. Suitable crystals of 5 for structural
determination were recrystallized from CH2Cl2–hexane solution. 1H
NMR (600 MHz, CD2Cl2):  1.56 (s, C(CH3)2, 6H), 5.23 (s, CH2,
2H), 6.95 (m, 1H), 6.99 (m, 2H), 7.14 (m, 1H), 7.16 (m, 1H), 7.37
[PhNC(CMe2)(N-1-C6H4)CN(CH2)2NMe2]PdCl (3).
Method 1. To a flask containing (COD)PdCl2 (0.35 g, 1.20 mmol) in
20 ml CH2Cl2, a solution of 1 (0.41 g, 0.56 mmol) and NEt3 (0.2 ml,
1.4 mmol) in 10 ml CH2Cl2 was added at room temperature. After
48 h of stirring, the dark-green solution was washed twice with
20 ml water. The volatiles were removed from the organic layer
and the residue was washed twice with 20 ml hexane to afford a
pale-yellow solid. Yield, 0.17 g, 30%.
3
(m, 2H), 7.40 (m, 2H), 7.85 (m, 1H), 8.14 (d, 1H, JHH = 7.8 Hz),
8.42 (m, 1H), 9.32 (m, 1H). 13C{1H} NMR (150 MHz, CD2Cl2): 
20.7 (s, C(CH3)2), 57.3 (s, tert-C(CH3)2), 58.0 (s, CH2), 117.0, 120.3,
120.9, 123.6, 124.27, 124.29, 124.9, 129.2, 138.5, 141.4, 149.8
(CH–C6H5 and CH–Py), 127.9, 131.0, 145.8, 154.0, 158.3, 158.8
(one 1-Ph, two Cipso–C6H5, one Cipso–Py and two CN).Anal. Calc.
for C23H21ClN4Pd: C, 55.77; H, 4.27; N, 11.31. Found: C, 55.09; H,
4.89; N, 11.41%.
Method 2. To a flask containing LiCl (0.033 g, 0.77 mmol), a
solution of 4 (0.076 g, 0.15 mmol) in 20 ml MeOH was added at
room temperature. After 30 min of stirring, the suspension was
filtered to afford a pale-yellow solid. The crude product was purified
2 6 9 4
D a l t o n T r a n s . , 2 0 0 4 , 2 6 9 1 – 2 6 9 6

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Table 6 Summary of crystal data for compounds 2, 3, 5 and 6
2
3
5
6
Formula
M
T/K
Crystal system
C23H22N4
354.45
293(2)
Triclinic
P1
C21H25ClN4Pd
475.30
293(2)
Triclinic
P1
C23H21ClN4Pd
495.29
293(2)
Rhombohedral
R 3
C25H24O2N4Pd
518.88
293(2)
Triclinic
P1
Space group
a/Å
b/Å
c/Å
/°
8.7023(9)
9.7380(11)
13.0560(14)
71.287(2)
84.039(2)
68.003(2)
971.47(18)
2
9.9515(8)
10.8850(9)
11.1266(9)
99.068(2)
115.3140(10)
98.306(2)
1045.17(15)
2
35.2349(14)
35.2349(14)
8.6726(5)
90
90
120
8.1039(5)
12.5455(7)
13.1672(8)
112.4890(10)
101.6740(10)
104.6700(10)
1127.52(12)
2
/°
/°
V/Å3
9324.5(8)
18
Z
Dc/Mg m−3
(Mo-K)/mm−1
Reflections collected
No. of parameters
R1a
1.212
0.073
5484
244
0.0533
0.1646
1.298
1.510
1.028
5792
265
0.0325
0.1025
0.965
1.588
1.041
17452
262
0.0238
0.0838
0.781
1.528
0.852
6308
289
0.0300
0.0987
0.931
wR2a
GoFb
2
a R1 = [∑(|Fo| − |Fc|]/∑|Fo|]; wR2 = [∑w(Fo2 − Fc2)2/∑w(Fo )2]1/2, w = 0.10. b GoF = [∑w(Fo2 − Fc2)2/(Nrflns − Nparams)]1/2
.
[PhNC(CMe2)(N-1-C6H4)CNCH2Py]Pd(OAc) (6). To
a flask containing Pd(OAc)2 (0.224 g, 1.0 mmol) and 2 (0.354 g,
1.0 mmol), 20 ml THF was added at room temperature.After 28 h of
stirring, the yellow suspension was filtered. The residue was washed
with 20 ml toluene to afford a white solid. Yield, 0.22 g, 41%. 1H
NMR (600 MHz):  1.50 (s, C(CH3)2, 6H), 2.28 (s, OC(O)CH3,
3H), 5.16 (s, CH2, 2H), 6.93 (d, 2H, 3JHH = 7.2 Hz), 7.01 (m, 1H),
7.12 (m, 2H), 7.32 (m, 4H), 7.65 (m, 1H), 7.77 (m, 1H), 8.09 (d,
1H, JHH = 7.8 Hz), 8.44 (d, 1H, JHH = 5.4 Hz). 13C{1H} NMR
(150 MHz):  20.6 (s, C(CH3)2), 24.9 (s, O–C(O)–CH3), 56.9
(s, tert-C(CH3)2), 57.5 (s, CH2), 116.6, 120.1, 120.8, 123.6, 124.2,
124.5, 125.0, 129.0, 135.9, 138.1, 148.6 (CH–C6H5 and CH–Py),
128.6, 130.6, 145.6, 153.5, 157.6, 158.6 (one 1-Ph, two Cipso–C6H5,
one Cipso–Py and two CN), 177.7 (s, O–C(O)–CH3). Anal. Calc.
for C25H24N4O2Pd: C, 57.87; H, 4.66; N, 10.80. Found: C, 57.23; H,
5.21; N, 10.85%.
AXS SMART 1000 diffractometer. The absorption correction was
based on the symmetry equivalent reflections using the SADABS
program. The space group determination was based on a check of
the Laue symmetry and systematic absences and was confirmed
using the structure solution. The structure was solved by direct
methods using a SHELXTL package.All non-H atoms were located
from successive Fourier maps, and hydrogen atoms were refined
using a riding model. Anisotropic thermal parameters were used
for all non-H atoms, and fixed isotropic parameters were used for
H atoms. Some details of the data collection and refinement are
given in Table 6.
3
3
CCDC reference numbers 216807 (2) and 216808 (5).
See http://www.rsc.org/suppdata/dt/b4/b404798b/ for crystallo-
graphic data in CIF or other electronic format.
Acknowledgements
We would like to thank the National Science Council of the
Republic of China for financial support.
[PhNC(CMe2)(N-1-C6H4)CNCH2Py]Pd(TFA) (7). To a
flask containing Pd(TFA)2 (0.332 g, 1.0 mmol) and 2 (0.354 g,
1.0 mmol), 20 ml THF was added at room temperature. After
16 h of stirring, the pale-gray suspension was filtered. The
residue was washed with 20 ml toluene to afford pale-gray
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Crystal structure data
Crystals were grown from concentrated hexane solution (2) or
CH2Cl2–hexane solution (3, 5 or 6), and isolated by filtration.
Suitable crystals of 2, 3, 5 or 6 were sealed in thin-walled glass
capillaries under a nitrogen atmosphere and mounted on a Bruker
D a l t o n T r a n s . , 2 0 0 4 , 2 6 9 1 – 2 6 9 6
2 6 9 5

View Article Online
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2 6 9 6
D a l t o n T r a n s . , 2 0 0 4 , 2 6 9 1 – 2 6 9 6