New bulky phosphinopyridine ligands. P～N～C Tridentates in palladium complexes

Article abstract of DOI:10.1039/b212169g

The sterically bulky pyridinyl phosphine (P～N) ligands have been prepared from the phosphinylation of 2,4-di-tert-butyl-6-methylpyridine. Due to the steric hindrance, substitution reaction of these P～N ligands with (COD)PdMeCl yields the chloro-bridged dipalladium species [(P～N) ₂Pd₂Me₂Cl₂], in which the P~N ligand acts as a monodentate. Treatment of these dimeric palladium compounds with AgBF₄ in the presence of acetonitrile gives the corresponding C-H activation metal complex [(P～N～C)Pd(CH₃CN)]BF₄. Both spectral and X-ray single-crystal characterization of these palladium complexes are presented.

Full text of DOI:10.1039/b212169g

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New bulky phosphinopyridine ligands. P∼N∼C Tridentates in
palladium complexes
Hsin-Pei Chen, Yi-Hung Liu, Shie-Ming Peng and Shiuh-Tzung Liu*
Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan.
E-mail: stliu@ccms.ntu.edu.tw
Received 12th December 2002, Accepted 6th February 2003
First published as an Advance Article on the web 25th February 2003
The sterically bulky pyridinyl phosphine (P∼N) ligands have been prepared from the phosphinylation of 2,4-di-tert-
butyl-6-methylpyridine. Due to the steric hindrance, substitution reaction of these P∼N ligands with (COD)PdMeCl
yields the chloro-bridged dipalladium species [(P∼N)2Pd2Me2Cl2], in which the P∼N ligand acts as a monodentate.
Treatment of these dimeric palladium compounds with AgBF4 in the presence of acetonitrile gives the corresponding
C–H activation metal complex [(P∼N∼C)Pd(CH3CN)]BF4. Both spectral and X-ray single-crystal characterization of
these palladium complexes are presented.
bidentates was performed by spectroscopic methods. In
Introduction
1
addition to the characteristic shifts for the substituents on H
There is considerable current interest in the design of mixed
NMR spectra, all ligands exhibit singlets in their 31P NMR
donor phosphine–amine ligands because of their potential
spectra and all shifts appear around Ϫ17 to 30 ppm relative to
85% H3PO4 in the typical range for diarylalkylphosphines.
importance in the catalysis of organic transformations1 and
also in polymerization.2 This interest is based on the modifi-
cation of the auxiliary ligand to fine-tune the property of
catalysts for better control. Due to the soft and hard nature
Palladium complexes with 1
Substitution reaction of [(COD)PdMeCl] with an equimolar
amount of 1a,b resulted in the formation of the corresponding
complex immediately. A positive coordination chemical shift on
31P NMR clearly indicates the coordination of the phosphorus
donor toward the palladium center (Table 1). The downfield
shift of 1H NMR signals of CH2P implies the possibility of the
chelation of P∼N donors. However, the shifts of tert-butyl
groups appears not to significantly change, suggesting a free
donor pyridinyl nitrogen atom. This observation was verified by
X-ray single crystal analysis. Instead of a bidentate, the P∼N
ligand behaves in a monodentate mode with only the phosphine
coordinated to the metal center. However, ligands 1a and 1b
provide the corresponding complexes 4a and 4b in different
of phosphorus and nitrogen donors, respectively, study of
phosphine–imine bidentates on either coordination or metal
catalyzed organic transformations has received much atten-
tion.3–33 Among these known P∼N bidentates, few are known as
sterically bulky ones.29 In this work, we present the preparation
of new bulky P∼N ligands and their coordination behavior
toward palladium() ions.
Results and discussion
Ligand synthesis
Synthesis of the desired phosphine ligands is summarized in
Scheme 1. Starting with picoline 2, nucleophilic aromatic sub-
stitution with an excess of tert-butyllithium provided the di-
tert-butyl substituted picoline 3.34 Deprotonation followed by
the treatment with diarylchlorophosphine yielded the corre-
sponding pyridine based phosphine 1a and 1b, respectively.
These ligands are air-sensitive compounds, which were handled
under an inert atmosphere of nitrogen with standard inert
atmosphere techniques. Characterization of these new P∼N
1
stereochemistry (see below). The H signal for Pd–CH3 of 4a
shows P–H coupling (3.1 Hz), but this is not seen in 4b for
unknown reasons.
As shown in Fig. 1 and 2, chloro-bridged palladium ions with
the nitrogen donor uncoordinated appear in both complexes
4a,b. All metal centers are typically square planar in both com-
Scheme 1 Preparation of P∼N ligands.
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 3
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 9 – 1 4 2 4
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Table 1 Selected spectral data of ligands and palladium complexes
1H NMRa
Compound
CH2P
But
Pd–CH3 or Pd–COCH3
31P NMR
1a
1b
4a
4b
5a
5b
3.99 (d, J = 2.1)
4.03 (d, J = 2.4)
4.19 (d, J = 11.4)
4.14 (d, J = 10.1)
4.24 (d, J = 11.6)
4.05 (d, J = 9.9)
1.25, 1.05
1.28, 1.17
1.20, 1.16
1.20, 1.15
1.24, 1.04
1.28, 1.25
Ϫ17.0
Ϫ19.3
27.0
31.5
16.5
1.43 (d, J = 3.1)
0.53
2.04
1.56
21.9
a In CDCl3 except for 1b (in CD3COCD3).
the crystal packing. In fact the 1H NMR shifts of the tert-butyl
groups remain the same as for the free ligands. Interestingly,
complex 4a was formed in a sterically congested fashion with
the two bulky dimesitylphosphino groups positioned cis to
each other, whereas the less steric bulky phosphino groups are
in trans form for 4b. In either instance, only one single isomer
was formed out of the two possibilities. This outcome is similar
to that in [Pd2(µ-Cl)2Me2(PPh2Me)] reported by Ladipo and
Anderson.35
Table 2 Selected bond distances (Å) and angles (Њ) for 4a, 4b and 5b
Complex
4a
4b
5b
Pd(1)–P(1)
Pd(1A)–P(1A)
Pd(1)–Cl(1)
Pd(1A)–Cl(1A)
Pd(1)–C(1)
Pd(1A)–C(1A)
Pd(1)–Cl(1A)
Pd(1A)–Cl(1)
P(1)–C(19)
2.2630(9)
2.269(1)
2.465(1)
2.039(4)
2.034(4)
2.039(4)
2.391(1)
2.490(1)
1.887(4)
2.2279(9)
2.2279(9)
2.3931(9)
2.3931(9)
2.033(4)
2.033(4)
2.481(1)
2.481(1)
1.858(4)
2.291(1)
2.291(1)
2.428(1)
2.428(1)
1.968(5)
1.968(5)
2.539(1)
2.539(1)
1.848(4)
Treatment of 4a and 4b with carbon monoxide provided the
corresponding chloro-bridged dipalladium acetyl complexes
5a and 5b, respectively, as evidenced by spectral data. 31P
NMR spectra of the carbonylated products shift to upper field
relative to the starting materials, as typically observed for
C(1)–Pd(1)–P(1)
C(1A)–Pd(1A)–P(1A)
C(1)–Pd(1)–Cl(1)
C(1A)–Pd(1A)–Cl(1A)
Pd(1)–Cl(1)–Pd(1A)
Pd(1)–Cl(1A)–Pd(1A)
90.2(1)
90.3(1)
171.2(1)
86.9(2)
93.63(3)
98.10(4)
91.1(1)
91.1(1)
89.6(1)
89.6(1)
93.60(3)
93.60(3)
89.8(2)
85.1(2)
95.84(4)
1
related species. H NMR signals at 2.04 ppm for 5a and 1.56
ppm for 5b as well as the IR absorptions at 1730 cmϪ1 for 5a
and 1720 cmϪ1 for 5b clearly illustrate the formation of the
acetyl palladium complexes.
In the carbonylation reaction, there is no indication of the
formation of any mononuclear species. Crystals suitable for
X-ray analysis of complex 5b were obtained. Fig. 3 shows its
ORTEP drawing and selected bond distances and angles are
also summarized in Table 2. Basically the structural framework
is similar to that of 4b except the replacement of methyl by the
acetyl group. It is also noticed that the stereorelationship of
the two acetyl groups remains trans as in 4b.
Fig. 1 ORTEP plot of complex 4a.
Fig. 3 ORTEP drawing of the palladium acetyl complex 5b.
It has been illustrated that the related P∼N ligand [2-(Ph2-
PCH2)C5H4N] shows a chelating P∼N nature with palladium
ions.36 Apparently, ligands designed in this work act as mono-
denate towards [(COD)PdMeCl] due to the steric hindrance of
the tert-butyl group.
Fig. 2 Molecular structure of complex 4b.
Intramolecular C–H activation
plexes with slight distortions as evidenced by the bond angles
slightly deviating from 90Њ. Selected bond distances and bond
angles are listed in Table 2. All bond distances and bond angles
lie within the normal range even for 4a with the bulky substi-
tuents being in cis arrangement. Distances of Pd–Cl bonds
trans to carbon ligands appear to be longer than those trans
to phosphine. The bulky pyridinyl groups appeared to be
staggered to each other in Fig. 1, which it is believed is due to
Treatment of 4a with silver tetrafluoroborate in acetonitrile at
room temperature gave an unexpected result. A new resonance
at 2.83 (d, JPH = 3.3 Hz, 2H) appears with the vanishing of the
ortho tert-butyl group in the 1H NMR spectrum, indicating the
formation of a metallated CH2 group. Complex 4b behaves
similarly (Scheme 2). Although both 1H and 13C NMR spectra
give unambiguously the structural determination for the C–H
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 9 – 1 4 2 4
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Table 3 Crystal data for 4a, 4b, 5b and 6ba
Complex
4a
4b
5b
6b
Formula
Mw
C66H94Cl2N2P2Pd2
1261.07
C29H39 ClNPPd
574.43
C60H78Cl2N2O2P2Pd2
1204.88
C30H38BF4N2PPd
650.80
Crystal system
Space group
Triclinic
P1
Triclinic
P1
Monoclinic
P21/c
Triclinic
P1
¯
¯
¯
a/Å
b/Å
c/Å
α/Њ
11.5490(1)
16.1300(1)
17.9020(2)
94.554(1)
101.601(1)
91.325(1)
3253.83(5)
2
9.7940(1)
12.2410(1)
13.1120(2)
75.428(1)
72.473(1)
72.846(1)
1409.27(3)
2
12.3940(2)
16.7220(3)
15.0540(2)
90
106.559(1)
90
2990.58(8)
2
1.338
9.4710(2)
12.1480(3)
14.1510(4)
104.090(1)
94.389(1)
103.300(1)
1521.56(7)
2
β/Њ
γ/Њ
V/Å3
Z
Dc/Mg mϪ3
F(000)
1.287
1320
1.354
596
1.420
668
1248
Crystal size/mm
θ range/Њ
Reflns. collected
Independent reflns. (Rint
R1 [I > 2σ(I )]
wR2
0.25 × 0.20 × 0.15
2.16–25.00
21494
11445 (0.0299)
0.0437
0.30 × 0.25 × 0.20
2.20–25.00
9383
4972 (0.0211)
0.0408
0.25 × 0.20 × 0.15
1.71–25.00
14733
5266 (0.0485)
0.0436
0.15 × 0.20 × 0.25
2.00–25.00
21100
5334 (0.0383)
0.0498
)
0.1219
0.1297
0.1097
0.1486
a Refinement method: full-matrix least squares on F 2.
Scheme 2 C–H Activation and ligand substitution reactions.
activation product, an X-ray diffraction study of 6b further
confirmed the proposed structure. An ORTEP view of 6b is
shown in Fig. 4. The crystal data for complex 6b are sum-
marized in Table 3. As expected, the palladium center displays
a slightly distorted square-planar geometry with phosphorus,
nitrogen as well as carbon donors from ligand 1b and
acetonitrile. All bond distances and bond angles lie within
normal ranges. The Pd–C(9) bond length [2.041(4) Å] is slightly
longer by about 0.04 Å than that of the related species 10
reported by Minghetti and coworkers.37 Presumably this is due
to the trans influence of phosphorus versus nitrogen donors. As
for the angles C(9)–Pd(1)–N(1) [80.9(2)Њ] and N(1)–Pd(1)–P(1)
[83.71(9)Њ], deviation from 90Њ indicate these chelating rings
have a high strain energy.
Concerning the C–H activation, reaction of 5a with AgBF4
gave a similar result, but accompanied with the formation of
methane and acetaldehyde as evidenced by the NMR spectrum.
Apparently the abstraction of chloride from the palladium
complexes readily generates the free coordination sites, which
allows the coordination of nitrogen and C–H activation to take
place. Upon the treatment of 5a with AgBF4, the tricoordinated
species 9 was the possible intermediate (Scheme 3), which then
underwent either C–H activation and reductive elimination of
acetaldehyde (path a) or the de-insertion of carbonyl group
followed by C–H activation and reductive elimination of
methane (path b).
Fig. 4 ORTEP plot of 6b. Selected bond lengths (Å) and angles (Њ):
Pd(1)–P(1) 2.390(1), Pd(1)–C(9) 2.041(4), Pd(1)–N(1) 1.996(3), Pd(1)–
N(2) 2.014(4); C(9)–Pd(1)–P(1) 164.1(1); N(1)–Pd(1)–N(2) 169.2(1),
N(1)–Pd(1)–C(9) 80.9(2), N(2)–Pd(1)–C(9) 88.6(2), N(1)–Pd(1)–P(1)
83.71(9).
In fact, the C–H activation reaction depends on the reaction
temperature. Fig. 5 shows variable-temperature 1H NMR
spectra for the reaction of complex 4a with an equimolar
amount of AgBF4 in CD3CN. At Ϫ30 ЊC, the tert-butyl groups
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 9 – 1 4 2 4
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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 as received unless otherwise
stated.
Nuclear magnetic resonance spectra were recorded in
CDCl3 or d6-acetone on either a Bruker AC-E 200 or AM-300
spectrometer. Chemical shifts are given in parts per million
1
relative to Me4Si for H and 13C NMR spectra and relative to
85% H3PO4 for 31P NMR spectra. Due to the complication of
the aromatic region, only chemical shifts of non-aromatic
carbons are reported. IR spectra were measured on a Nicolet
Magna-IR 550 spectrometer (Series-II) as KBr pallets, unless
otherwise noted.
Scheme 3
Ligand 1a
To a THF solution (10 mL) of compound 3 (1.3 g, 6.3 mmol)
was slowly added a hexane solution of n-butyllithium (2.5 M,
2.53 mL, 6.3 mmol) at ice-cold temperature. After stirring for
1 h, a solution of bis(2,4,6-trimethylphenyl)chlorophosphine
(1.67 M in 3.83 mL THF, 6.4 mmol) was added to the above
solution at Ϫ78 ЊC. The reaction mixture was stirred at room
temperature for 3 h. Upon concentration, the residue was
extracted with pentane and the extracts were filtrated through
Celite. The filtrate was concentrated to give a light yellow
viscous liquid, which was dissolved in methanol. The desired
phosphine was crystallized as a white solid (1.79 g, 60%): mp
129–130 ЊC. 1H NMR (CDCl3, 300 MHz): δ 6.96 (s, 1H, py-H5),
6.65 (s, 4H, Ar-H), 6.24 (s, 1H, py-H3), 3.99 (d, J = 2.08 Hz, 2H,
CH2), 2.16 (s, 6H, Ar–CH3), 2.10 (s, 12H, Ar–CH3), 1.25 (s, 9H,
But), 1.05 (s, 9H, But). 31P NMR: δ Ϫ17. 13C NMR: δ 168.0,
158.9, 156.3 (d, J = 6.6 Hz), 141.8 (d, J = 13.6 Hz), 137.1, 132.9
(d, J = 24.8 Hz), 129.6, 118.2 (d, J = 6.1 Hz), 112.6, 37.9 (d,
J = 20.9 Hz, py–CH2), 38.3, 34.3, 34.2 (d, J = 16.6 Hz), 29.9,
22.8 (d, J = 13.0 Hz), 20.7. HR-FAB MS: calc. for C32H44PN:
m/z 473.3211. Found: 473.3212. Anal. Calc. for C32H44NP: C,
81.84; H, 9.36; N, 2.96. Found: C, 81.29; H, 9.60; N, 2.97%.
Fig. 5 (a) Partial 1H NMR spectrum of 4a and partial 1H NMR
spectra upon addition of AgBF4 to 4a in the presence of CH3CN at (b)
Ϫ30 ЊC, (c) 0 ЊC and (d) 10 ЊC.
remain intact with the signal of Pd–CH3 up-field shifted relative
to the chloro-bridged species (Fig. 5(b)). As the temperature
increases, the signal of the Pd–CH3 becomes sharper as the
exchange of actonitrile becomes faster. (Fig. 5(c)) Above 0 ЊC,
C–H activation takes place as evidenced by the decrease in the
Pd–CH3 signal intensity and the appearance of a new signal
corresponding to methane (Fig. 5(d)). This observation
suggests that the removal of chloride ligand readily helps
the coordination of the pyridinyl nitrogen donor toward the
palladium center at lower temperature and the C–H activation
takes place above 0 ЊC to form 6a.
Ligand 1b
To a THF solution of 5 (1.1 g, 5.3 mmol) was added a 1.6 M
hexane solution of n-butyllithium (3.4 mL, 5.3 mmol) at ice-
cold temperature. After stirring for 1 h, (o-Tol)2PCl (1.33 g,
5.4 mmol) in THF (5 mL) was added to the above mixture at
Ϫ78 ЊC. The resulting mixture was warmed to room tem-
perature and stirred for another 5 h. After concentration, the
residue was distilled under vacuum to give the desired product
1
as a viscous liquid (0.98 g, 45%). H NMR (d6-acetone, 400
MHz): δ 7.46–7.42 (m, 2H, Ar-H), 7.26–7.23 (m, 7H, Ar-H),
6.60 (s, 1H, py-H3), 4.03 (d, J = 2.4 Hz, 2H, py–CH2), 2.35
(s, 6H, CH3), 1.28 (s, 9H, But), 1.17 (s, 9H, But). 31P NMR
(d6-acetone, 161.9 MHz): δ Ϫ19.3. HR-FAB MS: calc. for
C28H36PN: m/z 417.2585. Found (M ϩ 1): 418.2337.
The coordinating acetonitrile of 6 is easily substituted by
carbon monoxide and chloride to yield the corresponding
complexes 7a and 8a (Scheme 2). However, migratory insertion
of CO does not occur in these complexes even at elevated tem-
perature or pressure. This is quite unlike the behaviour of the
palladium complex 11 reported by Herrmann and coworkers,38
presumably due to the stable fused five-membered chelating
rings.
In summary, the tert-butyl group at the α position of the
pyridine ring hinders the coordination of the nitrogen donor
towards the metal center. However, C–H activation of the
tert-butyl group readily occurs to relieve the steric inter-
action, which allows the P∼N ligand to become a P∼C∼N
tridentate. The catalytic activity of these palladium complexes
are currently under investigation.
Complex 4a
A mixture of (COD)PdMeCl (0.177 g, 0.67 mmol) and ligand
1a (0.317 g, 0.67 mmol) in dichloromethane (15 mL) was stirred
at ambient temperature for 1 h. Upon concentration and
washed with hexane, the chloro-bridged palladium com-
1
plex was obtained as a yellow solid (0.39 g, 92%). H NMR
(d6-acetone, 400 MHz): δ 7.12 (s, 2H, py-H5), 7.06 (s, 2H,
py-H3), 6.77 (s, 8H, Ar-H), 4.19 (d, J = 11.4 Hz, 4H, CH2), 2.25
(s, 16H, Ar–CH3), 2.21 (s, 12H, Ar–CH3), 1.43 (d, J = 3.1,
6H, Pd–CH3), 1.20 (s, 18H, But), 1.16 (s, 18H, But). 31P NMR
(d6-acetone, 161.9 MHz): δ 27. 13C NMR (CDCl3, 100 MHz):
δ 169.2, 160.1, 152.4, 140.9 (d, J = 9.9 Hz), 130.9 (d, J = 8.8 Hz),
126.7, 126.3, 119.2 (d, J = 5.5 Hz), 114.6 (d, J = 2.9 Hz), 40.4
(d, J = 20.6 Hz, py–CH2), 37.5, 34.7, 30.4, 30.1, 22.2 (d, J =
10.1 Hz), 20.7, 5.7 (Pd–CH3). Anal. Calc. for C66H94N2-
Experimental
General information
All reactions, manipulations and purification steps were per-
formed under a dry nitrogen atmosphere. Tetrahydrofuran was
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 9 – 1 4 2 4
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Cl2P2Pd2: C, 62.86; H, 7.51; N, 2.13. Found: C, 63.99; H, 7.71;
N, 2.13%.
Ar–CH3), 1.39 (s, 6H, CH3), 1.30 (s, 9H, But). 31P NMR
(CDCl3, 161.9 MHz): δ 1.1. 13C NMR (CDCl3, 100 MHz):
δ 177.7, 165.4, 160.8 (d, J = 10.7 Hz), 140.3 (d, J = 9.9 Hz),
131.0 (d, J = 6.9 Hz), 127.8, 127.5, 124.2, 119.2 (d, J = 9.4 Hz),
116.8, 52.6 (d, J = 6 Hz), 48.7 (d, J = 42.4 Hz, py–CH2),
35.6, 31.86 (d, J = 5.8 Hz), 30.3, 23.4 (d, J = 9.5 Hz), 20.8, 3.1
(CH3CN). HR-FAB MS: Calc. for C34H46BF4N2PPd Ϫ CH3-
CNBF4: m/z = 578.2168. Found: 578.2152. Anal. Calc. for
C34H46BF4N2PPd: C, 57.76; H, 6.89; N, 3.75. Found: C, 58.05;
H, 6.56; N, 3.96%.
Complex 4b
The procedure for the preparation of this complex is essentially
similar to that for 4a. Yellow solid (97%): mp 188–189 ЊC
1
(decomp.). H NMR (CDCl3, 400 MHz): δ 7.93–7.91 (m, 2H,
Ar-H), 7.26–7.23 (m, 10H, Ar-H), 6.35 (s, 1H, py-H3), 6.77
(s, 4H, Ar-H), 4.14 (d, J = 10.1 Hz, 2H, CH2), 2.52 (s, 6H, CH3),
1.20 (s, 9H, But), 1.15 (s, 9H, But), 0.53 (s, 3H, Pd–CH3). 31P
NMR (CDCl3, 161.9 MHz): δ 31.5. 13C NMR (CDCl3, 100
MHz): δ 167.8, 159.7, 153.6 (d, J = 5.7 Hz), 141.9 (d, J =
8.8 Hz), 135.3 (d, J = 11.3 Hz), 131.3 (d, J = 8.2 Hz), 130.2,
128.6 (d, J = 46 Hz), 125.1 (d, J = 10.5 Hz), 119.5 (d, J = 4.4 Hz),
113.2, 37.4, 36.7 (d, J = 24.9 Hz, py–CH2), 34.6 (d, J = 5.5 Hz),
30.6, 30.1, 23.1 (d, J = 7.5 Hz), 22.6, 6.55 (Pd–CH3). Anal.
Calc. for C58H78N2Cl2P2Pd2: C, 60.63; H, 6.81; N, 2.44. Found:
C, 60.63; H, 7.31; N, 2.23%. FAB MS: m/z = 1132.5 (C58H78-
Cl2N2P2Pd2 Ϫ CH3).
Complex 6b
The procedure for the preparation of this complex is essentially
similar to that for 6a. Yellow solid (97%): mp: 169–173 ЊC
1
(decomp.). H NMR (d6-acetone, 400 MHz): δ 7.87 (s, 1H,
py-H5), 7.49–7.44 (m, 4H, Ar-H), 7.42–7.28 (m, 5H, Ar-H),
4.30 (d, J = 8.8 Hz, 2H, py–CH2), 2.92 (d, J = 8.2 Hz, 2H, CH2–
Pd), 2.67 (s, 3H, NCCH3), 2.55 (s, 6 H, Ar–CH3), 1.38 (s, 6H,
CH3), 1.36 (s, 9H, But). 31P NMR (CDCl3, 161.9 MHz): δ 6.9.
13C NMR (CDCl3, 100 MHz): δ 177.6, 163.4, 158.9 (d, J =
8.8 Hz), 141.8 (d, J = 14.3 Hz), 131.8, 131.7 (d, J = 14.9 Hz),
128.3, 127.9, 127.0 (d, J = 7.9 Hz), 125.5, 119.4, 117.2, 52.6 (d,
J = 5.5 Hz), 49.7 (d, J = 31.2 Hz, py–CH2), 35.7, 31.8 (d, J =
6.0 Hz), 31.6, 22.6, 21.7 (d, J = 11.8 Hz), 3.4 (CH3CN). Anal.
Calc. for C32H43NPPdCl: C, 62.54; H, 7.05; N, 2.28. Found: C,
62.88; H, 6.64; N, 2.31%. HR-FAB MS: Calc. for C30H38BF4-
N2PPd Ϫ CH3CNBF4) m/z = 522.1542. Found: 522.1550.
Complex 5a
A solution of 4a (0.50 g, 0.39 mmol) in dichloromethane (5 mL)
was bubbled with carbon monoxide for 30 min. The reaction
mixture was passed through Celite and diethyl ether was added
to the filtrate, which gave the complex 5a as a yellow precipitate
(0.52 g, 98%): mp 168–169 ЊC (decomp.). IR (KBr): 1730 cmϪ1
1
(νC᎐O). H NMR (CDCl3, 400 MHz): δ 7.75 (s, 1H, py-H5),
7.0᎐4 (s, 1H, py-H3), 6.73 (d, J = 2.9 Hz, 4H, Ar-H), 4.24 (d, J =
11.6 Hz, 2H, CH2), 2.19 (s, 6H, Ar–CH3), 2.13 (s, 12H, Ar–
CH3), 2.04 (s, 3H, COCH3), 1.24 (s, 9H, But), 1.04 (s, 9H, But).
31P NMR (CDCl3, 161.9 MHz): δ 16.5. 13C NMR (CDCl3, 100
Complex 7a
A solution of 6a (0.30 g, 0.48 mmol) in dichloromethane (3 mL)
was bubbled with carbon monoxide at ambient temperature
for 10 min. The reaction mixture was filtered through Celite
and the filtrate was evaporated to a small volume. Upon the
addition of diethyl ether, a yellow precipitate was obtained,
filtered off, and washed with diethyl ether to give the analyti-
cally pure sample as a yellow solid (0.24 g, 82%). IR (KBr):
MHz): δ 210.7 (C᎐O), 168.7, 160.6, 153.0, 140.8 (d, J = 9.8 Hz),
᎐
131.0 (d, J = 8.2 Hz), 126.0 (d, J = 40.5 Hz), 119.6 (d, J =
5.7 Hz), 114.4 (d, J = 3.4 Hz), 37.2, 37.1 (d, J = 19.7 Hz, py–
CH2), 34.9 (d, J = 19.7 Hz), 34.8, 30.5, 29.7, 22.4 (d, J = 7.4 Hz),
20.7. FAB MS: m/z = 1228.4 (C68H94N2Cl2P2Pd2O2 Ϫ C2H6O2).
Anal. Calc. for C68H94N2Cl2P2Pd2O2: C, 62.01; H, 7.19; N, 2.13.
Found: C, 61.56; H, 7.90; N, 1.69%.
2099 cmϪ1 (νC᎐O); 1H NMR (CDCl3, 400 MHz): δ 7.98 (s, 1H, py-
᎐
H5), 7.20 (s, 1H, py-H3), 6.89 (d, J = 11.4 Hz, 4H, Ar-H3,5), 4.76
(d, J = 11.5 Hz, 2H, py–CH2), 2.83 (d, J = 3.3 Hz, 2H, Pd–CH2),
2.27 (s, 18H, Ar–CH3), 1.49 (s, 6H, CH3), 1.38 (s, 9H, But). 31
P
Complex 5b
NMR (CDCl3, 161.9 MHz): δ 5.7. 13C NMR (CDCl3, 100
The procedure for the preparation of this complex is essentially
MHz): δ 181.5 (C᎐O), 175.1, 168.2, 161.7 (d, J = 9.5 Hz), 141.2,
᎐
similar to that for 5a. Yellow solid (97%): mp 172–174 ЊC
1
(decomp.). IR (KBr): 1720 cmϪ1 (νC᎐O). H NMR (CDCl3, 400
140.3, 131.4 (d, J = 8.0 Hz), 125.6 (d, J = 38.6 Hz), 121.3 (d,
J = 10.0 Hz), 54.1 (d, J = 5.5 Hz), 49.0 (d, J = 70.2 Hz), 43.1 (d,
J = 26.5 Hz), 36.1, 32.4 (d, J = 5.8 Hz), 23.7 (d, J = 9.4 Hz),
20.8. HR-FAB MS: Calc. for C33H43PNPdOBF4 Ϫ BF4: m/z =
606.2117. Found: 606.2122.
᎐
MHz): δ 8.28 (br, 2H, Ar-H5), 7.44 (s, 1H, py-H3), 7.26 (t, J =
14.8 Hz, 2H, Ar-H), 7.16–7.08 (m, 5H, Ar-H, py-H3), 4.05
(d, J = 9.9 Hz, 2H, CH2), 2.45 (s, 6H, Ar–CH3), 1.56 (s, 3H,
COCH3), 1.28 (s, 9H, But), 1.25 (s, 9H, But). 31P NMR (CDCl3,
161.9 MHz): δ 21.9. 13C NMR (CDCl3, 100 MHz): δ 219.5
(C᎐O), 168.0, 160.5, 153.9 (d, J = 5.6 Hz), 142.2 (d, J = 8.5 Hz),
᎐
Complex 8a
131.3 (d, J = 7.7 Hz), 130.6, 129.0, 128.6, 125.6 (d, J = 10.9 Hz),
120.3 (d, J = 4.2 Hz), 113.7, 37.5, 36.8 (d, J = 20.78 Hz,
py–CH2), 35.0, 30.8, 30.2, 22.9 (d, J = 7.6 Hz). Anal. Calc. for
C60H78Cl2N2O2P2Pd2: C, 59.81; H, 6.52; N, 2.32. Found: C,
59.85; H, 6.21; N, 2.08%. FAB MS: m/z 1125.3 (C60H78Cl2-
N2O2P2Pd2 Ϫ CH3OCl).
To a mixture of 6a (0.10 g, 0.14 mmol) and Et4NCl (13.9 mg,
0.16 mmol) was added acetonitrile (3 mL). The resulting solu-
tion was stirred at room temperature for 3 h. Upon filtration
through Celite, diethyl ether was added to the filtate to precipi-
tate the desired complex out of the solution. Filtration gave the
8a as a light yellow solid (61 mg, 71%). 1H NMR (CDCl3, 400
MHz): δ 7.12 (d, J = 1.4 Hz, 1H, py-H5), 6.99 (d, J = 1.7 Hz, 1H,
py-H3), 6.76 (d, J = 3.0 Hz, 4H, Ar-H), 4.02 (d, J = 8.4 Hz, 2H,
CH2), 2.63 (d, J = 9.2 Hz, 2H, CH2–Pd), 2.31 (s, 12H, Ar–CH3),
2.20 (s, 6H, Ar–CH3), 1.37 (s, 6H, CH3), 1.30 (s, 9H, But). 31P
NMR (CDCl3, 161.9 MHz): δ 0.51. 13C NMR (CDCl3, 100
MHz): δ 178.0 (d, J = 7.9 Hz), 162.9, 159.8 (d, J = 10.3 Hz),
140.5 (d, J = 10.4 Hz), 139.0, 130.4 (d, J = 6.3 Hz), 129.9 (d,
J = 19.3 Hz), 117.9 (d, J = 7.5 Hz), 116.1, 52.8 (d, J = 5.6 Hz),
48.0 (d, J = 96.6 Hz, py–CH2), 43.2 (d, J = 17.2 Hz), 35.3, 31.7
(d, J = 6.2 Hz), 30.4, 23.8 (d, J = 9.1 Hz), 20.8. HR-FAB MS:
Calc. for C32H43NPPdCl: m/z 613.1856. Found: 613.1863. Anal.
Calc. for C32H43NPPdCl: C, 62.54; H, 7.05; N, 2.28. Found: C,
62.88; H, 6.64; N, 2.31%.
Complex 6a
A solution of 4a (0.50 g, 0.15 mmol) in dichloromethane (5 mL)
was added to a suspension of AgBF4 (62.0 mg, 0.15 mmol) in
dichloromethane (5 mL) at room temperature. After stirring for
1 h, the reaction mixture was passed through Celite to remove
the silver salt. The filtrate was concentrated to a small volume
of solution. Diethyl ether was added to the solution and
the palladium complex was obtained as a yellow precipitate
1
(191 mg, 97%): mp 173–174 ЊC (decomp.). H NMR (CDCl3,
400 MHz): δ 7.37 (s, 1H, py-H5), 7.05 (s, 1H, py-H3), 6.84
(d, J = 3.1 Hz, 4H, Ar-H), 4.21 (d, J = 9.6 Hz, 2H, CH2), 2.59
(d, J = 8.4 Hz, 2H, CH2–Pd), 2.38 (s, 3H, NCCH3), 2.23 (s, 18H,
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 9 – 1 4 2 4
1423

View Article Online
13 R. Romeo, L. M. Scolaro, M. R. Plutino, A. Romeo, F. Nicolo and
A. Del Zotto, Eur. J. Inorg. Chem., 2002, 629.
14 P. Pelagatti, A. Bacchi, M. Carcelli, M. Costa, H.-W. Fruhauf,
K. Goubitz, C. Pelizzi, M. Triclistri and K. Vrieze, Eur. J. Inorg.
Chem., 2002, 439.
15 F. Dahan, P. W. Dyer, M. J. Hanton, M. Jones, D. M. P. Mingos,
A. J. P. White, D. J. Williams and A.-M. Williamson, Eur. J. Inorg.
Chem., 2002, 732.
16 Z. B. Guan and W. J. Marshall, Organometallics, 2002, 21, 3580.
17 W.-P. Deng, X.-L. Hou, L.-X. Daia and X.-W. Dong, Chem.
Commun., 2000, 1483.
Crystallography
Crystals suitable for X-ray determination were obtained for 4a,
4b, 5b and 6b by slow diffusion of diethyl ether into a dichloro-
methane solution at room temperature. Cell parameters were
determined either by a Siemens SMART CCD diffractometer.
Crystal data of complexes 4a, 4b, 5b and 6b are listed in Table 3
and their ORTEP plots are shown in Figs. 1–4, respectively
(labels of phenyl groups are omitted for clarity).
CCDC reference numbers 199587–199590.
See http://www.rsc.org/suppdata/dt/b2/b212169g/ for crystal-
lographic data in CIF or other electronic format.
18 (a) P. Braunstein, F. Naud and S. Rettig, New J. Chem., 2001, 25, 32;
(b) P. Braunstein, M. D. Fryzuck, M. Le Dall, F. Naud, S. Rettig and
F. Speiser, J. Chem. Soc., Dalton Trans., 2000, 1067.
19 H. Yang, H. Gao and R. Angelici, Organometallics, 2000, 19, 622.
20 (a) X. M. Liu, K. F. Mok and P. H. Leung, Organometallics, 2001,
20, 3918; (b) X. M. Liu, K. F. Mok, J. J. Vittal and P. H. Leung,
Organometallics, 2000, 19, 3722.
Acknowledgements
We thank the National Science Council for financial support
(NSC90–2113-M-002–038).
21 F. Lam, M. Q. Feng and K. S. Chan, Tetrahedron, 1999, 55, 8377.
22 M. D. Mikoluk, R. McDonald and R. G. Cavell, Inorg. Chem., 1999,
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23 T. R. Ward, Chimia, 1999, 53, 19.
24 G. Muller, M. Klinga, P. Osswald, M. Leskela and B. Rieger,
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D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 9 – 1 4 2 4
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