Palladium(II) complexes of Y,C,Y-chelated phosphines: Synthesis, structure, and catalytic activity in Suzuki-Miyaura reaction

Article abstract of DOI:10.1002/aoc.1737

The phosphines L¹PPh₂ (1) and L²PPh ₂ (2) containing different Y,C,Y-chelating ligands, L¹ = 2,6-(^tBuOCH₂)₂C₆H₃ ^- and L² = 2,6-(Me₂NCH₂) ₂C₆H₃^-, were treated with PdCl ₂ and di-Aμ-chloro-bis[2-[(N,N-dimethylamino)methyl]phenyl- C,N]-dipalladium(II) and yielded complexes trans-{[2,6-(^tBuOCH ₂)₂C₆H₃]PPh₂} ₂PdCl₂ (3), {[2,6-(Me₂NCH₂) ₂C₆H₃]PPh₂} PdCl₂ (4), {[2,6-(^tBuOCH₂)₂C₆H ₃]PPh₂}Pd(Cl)[2-(Me₂NCH₂)C ₆H₄] (5) and {[2,6-(Me₂NCH₂) ₂C₆H₃]PPh₂}Pd(Cl)[2-(Me ₂NCH₂)C₆H₄] (6) as the result of different ability of starting phosphines 1 and 2 to complex PdCl₂. Compounds 3-6 were characterized by ¹H, ¹³C, ³¹P NMR spectroscopy and ESI-MS. The molecular structures of 3,4 and 6 were also determined by X-ray diffraction analysis. The catalytic activity of complexes 3-6 was evaluated in the Suzuki-Miyaura cross-coupling reaction.

Full text of DOI:10.1002/aoc.1737

Full Paper
Received: 26 May 2010
Revised: 10 August 2010
Accepted: 10 August 2010
Published online in Wiley Online Library: 11 November 2010
(wileyonlinelibrary.com) DOI 10.1002/aoc.1737
Palladium(II) complexes of Y,C,Y-chelated
phosphines: synthesis, structure, and catalytic
activity in Suzuki–Miyaura reaction
a
a
a
b
ˇb
ˇ
˚
´ ˇ
ˇ
´
ˇ
ˇ
ˇ
´
Tomas Reznícek , Libor Dostal , Ales Ruzˇicka , Jirí Kulhanek , Filip Bures
and Roman Jambora∗
The phosphines L1PPh2 (1) and L2PPh2 (2) containing different Y,C,Y-chelating ligands, L1 = 2,6-(tBuOCH2)2C6H3
−
and L2 = 2,6-(Me2NCH2)2C6H3−, were treated with PdCl2 and di-µ-chloro-bis[2-[(N,N-dimethylamino)methyl]phenyl-C,N]-
dipalladium(II) and yielded complexes trans-{[2,6-(tBuOCH2)2C6H3]PPh2}2PdCl2 (3), {[2,6-(Me2NCH2)2C6H3]PPh2} PdCl2 (4),
{[2,6-(tBuOCH2)2C6H3]PPh2}Pd(Cl)[2-(Me2NCH2)C6H4] (5) and {[2,6-(Me2NCH2)2C6H3]PPh2}Pd(Cl)[2-(Me2NCH2)C6H4] (6) as the
result of different ability of starting phosphines 1 and 2 to complex PdCl2. Compounds 3–6 were characterized by 1H, 13C, 31
P
NMR spectroscopy and ESI-MS. The molecular structures of 3,4 and 6 were also determined by X-ray diffraction analysis. The
c
catalytic activity of complexes 3–6 was evaluated in the Suzuki-Miyaura cross-coupling reaction. Copyright ꢀ 2010 John Wiley
& Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: Y,C,Y ligands; palladium; chelates; Suzuki-Miyaura; C–C coupling
Introduction
The treatment of 1 and 2 with PdCl2 and di-µ-chloro-
bis[2-[(N,N-dimethylamino)methyl]phenyl-C,N]-dipalladium(II)
yielded complexes trans-{[2,6-(tBuOCH2)2C6H3]PPh2}2PdCl2 (3),
{[2,6-(Me2NCH2)2C6H3]PPh2}PdCl2 (4), {[2,6-(tBuOCH2)2C6H3]
PPh2}Pd(Cl)[2-(Me2NCH2)C6H4] (5) and {[2,6-(Me2NCH2)2C6H3]
PPh2}Pd(Cl)[2-(Me2NCH2)C6H4] (6) as the result of the differ-
ent abilities of the starting phosphines 1 and 2 to complex
palladium(II) compounds. Compounds 3–6 were characterized
by 1H, 13C, 31P NMR spectroscopy and ESI-MS. The solid-state
structures of 3, 4 and 6 were determined by X-ray diffraction
analysis. Complexes 3–6 were further tested as Pd(II)-precatalysts
in Suzuki–Miyaura cross-coupling reaction.
Tertiary aromatic phosphines bearing the methoxy groups
at the 2,6-positions of the phenyl group such as tris
(2,6-dimethoxyphenyl)phosphine (TDMPP), tris(2,4,6-trimeth-
oxyphenyl)phosphine (TTMPP) and their related phosphines
have the combined characteristics of high basicity and
steric bulkiness.[1–3] Transition metal complexes with ether-
functionalized phosphine ligands have been found to exhibit
enhanced reactivity due to the presence of weak (P,OMe) chela-
tion producing metal–ether interactions that are often labile both
in the solid state and in solution.[3–5] As a result of this behavior,
ether functionalized phosphines are referred to as ‘hemi-labile’
ligands. These ligands possess a variety of the coordination modes
in the transition metal complexes; the bidentate or tridentate
chelate rings containing metal–O bonds derived from elimination
of methyl groups.[3,5,6] In contrast, corresponding P–N chelating
ligands are widely used in the chemistry of transition metals. In
general, the discussed functionalized phosphines form six- and
five-member metal–donor rings as the result of P ∩ N-chelation to
transition metal centre.[7]
Results and Discussion
The treatment of the lithium salts L1Li and L2Li with
chlorodiphenylphosphine yielded compounds L1PPh2 (1) (see
Experimental) and L2PPh2 (2).[9] The reaction of 1 (2 equiv.) with
PdCl2 yielded complex trans-{[2,6-(tBuOCH2)2C6H3]PPh2}2PdCl2
(3) (Scheme 1).
Recently, we have reported the synthesis of intramolecularly
coordinatedcompoundscontainingheaviermain-groupelements
M (M is Sn, Sb or Bi) containing O,C,O- or N,C,N-chelating ligands
L1–2 (see Fig. 1) and demonstrated possible stabilization of a
speciesasdistannyneL2SnSnL2 orL2SbSebytheabove-mentioned
pincer ligands.[8]
∗
Correspondence to: Roman Jambor, Department of General and Inorganic
´
Chemistry,FacultyofChemicalTechnology,UniversityofPardubice,Studentska
573, CZ-53210, Pardubice, Czech Republic. E-mail: roman.jambor@upce.cz
a
Department of General and Inorganic Chemistry, Faculty of Chemical
As a part of our studies on main group elements con-
taining pincer-type ligands, we discuss here the reactivity
of phosphines L1PPh2 (1) and L2PPh2 (2) containing Y,C,Y-
´
Technology, University of Pardubice, Studentska 573, CZ-53210, Pardubice,
Czech Republic
−
chelating ligands, −L1 = 2,6-(tBuOCH2)2C6H3 and L2 = 2,
b
InstituteofOrganicChemistryandTechnology,FacultyofChemicalTechnology,
6-(Me2NCH2)2C6H3 towards different palladium(II) complexes.
´
University of Pardubice, Studentska 573, CZ-53210, Pardubice, Czech Republic
c
Appl. Organometal. Chem. 2011, 25, 173–179
Copyright ꢀ 2010 John Wiley & Sons, Ltd.

ˇ
T. Reznícˇek et al.
Figure 1. The Y,C,Y-chelating ligands used for the synthesis of the starting
phosphine ligands.
The 31P NMR of 3 showed a signal at 14.7 ppm that was shifted
downfield compared with 1 (−20.4 ppm). The 1H NMR spectrum
of 3 measured at 300 K contained sharp resonance at 4.45 ppm
for CH2O group of the ligand L1. In addition, the 1H and 13C
NMR spectra revealed only one set of sharp signals at the whole
temperature range (300–210 K), suggesting both free rotation of
un-coordinated CH2OtBu arms and a symmetrical arrangement
around the central Pd atom in 3. The ESI/MS analysis of 3 showed
the presence of the specific ion at m/z 1011 [M − Cl]+. The
molecular structure of 3 was determined by X-ray diffraction
techniques. The ORTEP drawing is depicted in Fig. 2 together with
the selected bond distances and angles. The crystal data and
structure refinement are given in Table 1.
Figure 2. The ORTEP view of 3. The thermal ellipsoids are drawn with
50% probability. Hydrogen atoms are omitted for clarity. Selected
bond distances (Å) and angles (deg): Pd1–Cl1 2.3014(8), Pd1–Cl1a
2.3014(8), Pd1–P1 2.3363(8), Pd1–P1a 2.3363(8), Cl1–Pd1–Cl1a 180.00(5),
Cl1–Pd1–P1a 94.54(3), Cl1–Pd1–P1 85.46(3), Cl1a–Pd1–P1a 85.46(3),
Cl1–Pd1–P1a 94.54(3), P1–Pd1–P1a 180.00(5).
The coordination number of Pd(II) is 4 with mutually trans
monodentate phosphines 1 and chlorine atom Cl1 and Cl1a in
3. The P1–Pd1–Cl1 and P1a–Pd1–Cl1 angles are 85.46(3)◦ and
94.54(3)◦, respectively, leading to a slight distortion from the
square planar geometry around the metal center. The trans atoms
define angles of P1–Pd1–P1a = 180.0(5)◦ and Cl1–Pd1–Cl1a =
180.0(5)◦. The average Pd–P bond distance in 3 of 2.3363(8) Å is
similar to those observed in phosphine and phosphite complexes
of Pd(II) (2.2–2.4 Å).[3,5–7] The η1 –Pd-P bond distance is longer
than those found in (PdTTMPP-O)2 [2.270(4) Å and 2.251(4) Å] as
the result of the chelate effect of the η2-TTMPP ligands in the latter
compound.[6e]
Thereactionof2(2equiv.)withPdCl2 wasmonitoredby31PNMR
spectroscopy with appearing of new signal at 19.4 ppm together
withthesignalat−16.5 ppmcorrespondingto2in1: 1integration
ratio. The modification of stoichiometry to 1 : 1 (2–PdCl2) resulted
in the synthesis of compound {[2,6-(Me2NCH2)2C6H3]PPh2}PdCl2
(4) (Scheme 2).
The 31P NMR of 4 showed a signal at 19.4 ppm that is shifted
downfield compared with 2 (−16.5 ppm). The 1H NMR spectrum
of 4 measured at 300 K contained the broad signal at 2.42 ppm for
CH2N and 1.76 ppm for CH3 groups of the ligand L2. The 1H NMR
spectrum of 4 measured at 250 K revealed an AB spin system (δA
2.26, δB 2.39) with JAB being 12 Hz and an AX spin system at 3.38
and 3.76 ppm for CH2N groups and three signals at 1.74, 2.69 and
3.14 ppm in the ratio 2 : 1:1 for the CH3 groups of the ligand L2. This
pattern indicates that 4 in solution possesses two magnetically
inequivalent CH2NMe2 moieties. This is in accordance with the
measured solid-state structure (see below). The ESI/MS analysis of
4 revealed the presence of specific ions at m/z 591 [M + K]+, m/z
575 [M + Na]+ and at m/z 517 [M − Cl]+ as well as at m/z 587 [M
+ Cl]−. The molecular structure of 4 was also confirmed by X-ray
diffraction techniques. The ORTEP drawing is depicted in Fig. 3
together with the selected bond distances and angles. The crystal
data and structure refinement are given in Table 1.
The phosphine 2, bearing nitrogen atom, behaves as a P ∩
N chelate in 4. The coordination number of Pd(II) is 4 with
mutually cis arrangement of phosphorus and nitrogen atoms
of the η2-coordinated phosphine 2 and chlorides Cl1 and Cl2
in 4. The cis atoms define angles of P1–Pd1–N1 = 94.75(8)◦
and Cl1–Pd1–Cl2 = 88.13(3)◦, and shows the distortion of ideal
square-planar geometry resulting from the ring strain of the six-
membered metallacycle Pd1–P1–C1–C2–C7–N1. The Pd1–P1
bond distance in 4 of 2.2543(9) Å is similar to those observed in
phosphine and phosphite complexes of Pd(II) (2.2–2.4 Å).[3,5–7]
The value of the Pd1–N1 bond is 2.087(3) Å, defining a strong
coordination of nitrogen to Pd atom, and is comparable to those
Scheme 1. The synthesis and schematic structure of 3.
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Palladium(II) complexes of Y,C,Y-chelated phosphines
Table 1. Crystal data and structure refinement for 3, 4 and 6
3
4
6
Empirical formula
Color
C56H70Cl2O4P2Pd ×3(C4H8O)
C24H29Cl2N2PPd ×2(CH2Cl2)
Yellowish
C33H41ClN3PPd × CH2Cl2
Yellowish
Yellowish
Monoclinic
P 21/c
Crystal system
Space group
a (Å)
Monoclinic
P 21/c
Monoclinic
P 21/c
13.0851(13)
20.3479(18)
12.2730(4)
8.9871(4)
14.1711(12)
10.0210(4)
b (Å)
12.6159(9)
c (Å)
26.635(2)
25.5919(16)
α (deg)
β (deg)
γ (deg)
Z
µ (mm−1
Dx (mg m−3
112.261(5)
94.512(6)
109.110(7)
2
0.503
4
1.222
4
0.848
)
)
1.387
1.597
1.426
Crystal size (mm)
Crystal shape
θ range (deg)
0.55 × 0.30 × 0.15
Plate
0.28 × 0.16 × 0.09
Needle
0.40 × 0.25 × 0.10
Block
1–27.5
0.823, 0.938a
1–27.5
0.812, 0.906a
1–27.5
0.717, 0.918a
T
min, Tmax
No. of reflections measured
No. of unique reflections; Rint
No. of observed ref. [I > 2σ(I)]
No. of parameters
Final Rb
20852
30983
21481
6777, 0.0806
5198
6851, 0.0764
5136
7637, 0.0750
5505
295
325
379
0.0544
0.0432
0.0521
[I > 2σ(I)]
wR2b (all data)
0.1398
0.0845
0.1248
2
2
a Correction by SORTAV program. b Definitions: R(F) = ꢀ||Fo|−||Fc||/ꢀ|Fo|, wR2 = {ꢀ[w(Fo −Fc2)2]/ꢀ[w(Fo2)2]}1/2, S = {ꢀ[w(Fo −Fc2)2]/(Nreflns
−
2
N
params)}1/2. cWeighting scheme w = [σ2(Fo2) + (w1P) + w2P]−1; P = [max(Fo2, 0) + 2Fc2]/3; Rint = ꢀ|Fo − Fo2(mean)|/ꢀFo2 (summation is carried
out only where more than one symmetry equivalent is averaged).
Scheme 2. The synthesis and schematic structure of 4.
found in similar monomeric N-coordinated Pd complexes (range
of 2.073–2.155 Å).[7,10]
The ESI/MS spectra of 5 showed a specific ion at m/z 674
[M − Cl]+.
Complexes {[2,6-(tBuOCH2)2C6H3]PPh2}Pd(Cl)[2-(Me2NCH2)C6
H4] (5) and {[2,6-(Me2NCH2)2C6H3]PPh2}Pd(Cl)[2-(Me2NCH2)C6
H4] (6) were prepared by the cleavage reaction of di-
meric di-µ-chlorobis{2-[(dimethylamino)methyl]phenyl-C,N}-di-
palladium(II) by phosphines 1 or 2, respectively (Scheme 3).
The 31P NMR of 5 showed the signal at 24.2 ppm that is shifted
downfield compared with 1 (−20.4 ppm). The 1H NMR spectrum
of 5 measured at 300 K contained sharp resonance at 4.84 ppm
for the CH2O group of the ligand L1 and 3.58 ppm for the CH2N
group. In addition, the 1H and 13C NMR spectra revealed only one
set of sharp signals at the whole temperature range (300–220 K),
suggesting both free rotation of un-coordinated CH2OtBu arms
and coordination of the CH2N group of the C,N-chelate ligand to
thecentralPdatomin5.TheNMRdatathusdefineη1-coordination
of 1 to the Pd atom, which is further coordinated by the chlorine
atom, nitrogen and carbon atoms of C,N-chelate ligand (Fig. 4).
The 31P NMR of 6 showed a signal at 10.3 ppm that
is shifted downfield compared with 2 (−16.5 ppm). In con-
trast to the NMR data of 5, the 1H NMR spectrum of {[2,
6-(Me2NCH2)2C6H3]PPh2}Pd(Cl)[2-(Me2NCH2)C6H4] (6) at 300 K
contained two broad signals at 2.82 ppm for CH2N moieties of
the ligand L2 and at 2.23 ppm for the C,N-chelating group. The
1H NMR spectrum of 6 at 210 K revealed an AB spin system (δA
2.41, δB 2.71) with JAB being approximately 11 Hz and an AX spin
system at 3.17 and 3.95 ppm for CH2N groups of ligand L2 together
with a singlet at 2.31 for CH2N moiety of C,N-chelating group. This
pattern indicates that 6 in solution possesses two magnetically
non-equivalent CH2NMe2 moieties of the ligand L2, and further
indicates that phosphine 2 behaves as the P ∩ N chelate in 6. The
η2-coordination of 2 to the Pd atom that is further coordinated by
chlorine atom and carbon atoms of C,N-chelate ligand resulted in
de-coordination of the CH2N group of C,N-chelate ligand from the
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ˇ
T. Reznícˇek et al.
Figure 4. The schematic structure of complexes 5 and 6.
Figure 3. The ORTEP view of 4. The thermal ellipsoids are drawn with 50%
probability. Hydrogen atoms and CH2Cl2 molecule are omitted for clarity.
Selected bond distances (Å) and angles (deg): Pd1–N1 2.087(3), Pd1–P1
2.2543(9), Pd1–Cl2 2.3001(9), Pd1–Cl1 2.3732(9), N1–Pd1–P1 94.75(8),
N1–Pd1–Cl2 173.67(8), P1–Pd1–Cl2 87.56(3), N1–Pd1–Cl1 90.38(8),
P1–Pd1–Cl1 170.85(3), Cl2–Pd1–Cl1 88.13(3).
centralPdatomin6(seeFig. 4). Thisisinaccordancewiththesolid-
state structure (see below). The ESI/MS spectra revealed specific
ions at m/z 654 [M + H]+ and m/z 616 [M − Cl]+, respectively. The
molecular structure of 6 was determined by X-ray diffraction tech-
niques. The ORTEP drawing is depicted in Fig. 5 together with the
selected bond distances and angles. The crystal data and structure
refinement are given in Table 1. The Pd atom is four-coordinated
and exhibits a square planar configuration. The η2-coordination
of phosphine 2 with the bond distances of Pd1–P1 and Pd1–N2
is 2.2288(11) Å and 2.177(3) Å, respectively. Complex 6 forms a
six-membered metallacycle Pd1–P1–C10–C11–C16–N2 which
results in dissociation of the Pd1–N1 bond of C,N-chelating ligand
[Pd1–N1 = 2.880(4) Å].
Figure 5. The ORTEP view of 6. The thermal ellipsoids are drawn with
50% probability. Hydrogen atoms and CH2Cl2 molecules are omitted for
clarity. Selected bond distances (Å) and angles (deg): Pd1–C1 1.995(4),
Pd1–N2 2.177(3), Pd1–P1 2.2288(11), Pd1–Cl1 2.4040(11), C1–Pd1–N2
172.00(15), C1–Pd1–P1 87.47(12), N2–Pd1–P1 96.07(9), C1–Pd1–Cl1
88.59(12), N2–Pd1–Cl1 90.85(9), P1–Pd1–Cl1 157.18(4).
well as 4-bromobenzylbromide and 2-bromo-1-methylimidazole-
4,5-dicarbonitrile 7[13] were screened. The reactions were mon-
itored by GC analysis and the results are summarized in
Table 2. Commercially available [(PPh3)2PdCl2] was used as a
standard (Table 2, entries 21–25). 4-Substituted biphenyls 8
or 2-phenylimidazole 9 were detected as major products in
all cases. As a general trend, compounds 3 and 5 featuring
bulkier phosphine ligand 1 showed higher catalytic activities
in all examined reactions than compounds 4 and 6 contain-
ing ligand 2. Whereas the capability of 4 and 6 to catalyze
CatalyticActivityof3–6intheSuzuki–MiyauraCross-coupling
Reactions
Prepared palladium(II) complexes 3–6 were used as the catalysts
in the Suzuki–Miyaura[11] reaction between (hetero)aryl bromides
and phenylboronic acid (Scheme 4).
The cross-coupling reactions were carried out under stan-
dard conditions involving a Pd(II) catalysts 3–6 (4%)/THF–water
(4 : 1)/Na2CO3 system under argon.[12] Aryl bromides featuring ei-
ther electron-donating or electron-withdrawing substituents as
Scheme 3. The synthesis of complexes 5 and 6.
c
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Palladium(II) complexes of Y,C,Y-chelated phosphines
Scheme 4. Suzuki–Miyaura cross-coupling reaction.
the Suzuki–Miyaura reaction on the examined (hetero)aryl bro-
mides was lower than that observed for [(PPh3)2PdCl2], the
catalytic activities of 3 and 5 were generally higher. As expected,
the Suzuki–Miyaura reaction carried out on the electron-rich
N,N-dimethyl-4-bromoaniline afforded the lowest yields. A cross-
coupling of 2-(N,N-dimethylaminomethyl)phenyl moiety present
in complexes 5 and 6 was observed only in two reactions cat-
alyzed by 6 (Table 2, entries 17 and 18). Side products resulting
from the reduction or homocoupling of the starting bromides
were not detected except for the commercially available catalyst
(Table 1, entry 23). However, in case of 4-bromobenzylbromide
as a starting compound, product 10 derived from the consec-
utive cross-coupling on Br-C(sp3) was also detected (Table 2,
entries 4, 9, 14, 19 and 24). In addition, the Suzuki–Miyaura
reaction carried out on heterocyclic substrate 7 afforded target
product 9 in yields up to 88% (3). With respect to the easy
preparation from PdCl2 and the highest yields obtained in the
Suzuki–Miyaura reaction, Pd(II)–complex 3 seems to be the cata-
lyst of choice.
Conclusions
In summary, the coordination arrangement of the central Pd(II)
atom in 3–6 differs substantially as the result of different
binding abilities of the starting phosphines 1 and 2. While the
phosphine 1 behaves as the monodentate ligand, phosphine 2
prefers a chelating P ∩ N-arrangement. The different arrangement
prompted us to test the catalytical activity of the prepared
complexes 3–6 in the Suzuki–Miyaura cross-coupling reactions
to see the influence of the phosphines and different structures on
the catalytic activity. In general, all of the prepared compounds
3–6 were able to catalyze the Suzuki–Miyaura reaction. However,
palladium(II) complex 3 bearing two bulky phosphine ligands 1
Table 2. Catalytic activity of Pd(II) complexes 3–6 in the Suzuki–Miyaura reaction
Entry
Catalyst
Bromide (R)
Conversion (%)a
Products [R/yields (%)]b
1
3
H
NO2
NMe2
CH2Br
7
91
100
69
100
88
86
82
20
95
34
94
100
70
98
73
86
45
9
8 (R = H/91%)
8 (R = NO2/100%)
8 (R = NMe2/68%),
8 (R = CH2Br/47%), 10 (51%)
9 (87%)
2
3
3
3
4
3
5
3
6
4
H
8 (R = H/85%)
7
4
NO2
NMe2
CH2Br
7
8 (R = NO2/81%)
8 (R = NMe2/20%),
8 (R = CH2Br/55%), 10 (40%)
9 (33%)
8
4
9
4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
4
5
H
8 (R = H/93%)
5
NO2
NMe2
CH2Br
7
8 (R = NO2/96%)
8 (R = NMe2/71%)
8 (R = CH2Br/58%), 10 (40%)
9 (72%)
5
5
5
6
H
8 (R = H/85%)
6
NO2
NMe2
CH2Br
7
8 (R = NO2/41%)c
8 (R = NMe2/5%)c
8 (R = CH2Br/53%), 10 (39%)
9 (23%)
6
6
92
23
83
96
62
97
67
6
[(PPh3)2PdCl2]
[(PPh3)2PdCl2]
[(PPh3)2PdCl2]
[(PPh3)2PdCl2]
[(PPh3)2PdCl2]
H
8 (R = H/82%)
NO2
NMe2
CH2Br
7
8 (R = NO2/95%)
8 (R = NMe2/53%)d
8 (R = CH2Br/62%), 10 (35%)
9 (67%)
a Based on the consumption of (hetero)aryl bromide. b According to the GC analyses. c Transfer of 2-(N,N-dimethylaminomethyl)phenyl ligand was
observed (4%). d Homocoupling of the starting bromide was observed (9%).
c
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ˇ
T. Reznícˇek et al.
afforded the 4-substituted biphenyls and 2-phenylimidazole in
69–100% yields.
Preparation of {[2,6-(Me2NCH2)2C6H3]PPh2}PdCl2 (4)
PdCl2 (0.15 g, 0.85 mmol) was added to the solution of 2 (0.32 g,
0.85 mmol)inTHF(10 ml)andthesuspensionwasstirredfor5 days.
Thesolventwasevaporated, thesolidresiduumwasextractedwith
CH2Cl2 (1 × 15 ml) and the suspension was stirred for 30 min. The
solvent was evaporated after filtration and the solid was washed
with hexane (5 ml) t◦o afford orange crystals of 4. Yield: 0.38 g
(81%). M.p. 186–189 C; 1H NMR (CDCl3, 500 MHz, 250 K) δ (ppm):
1.74 (s, 6H, NCH3); 2.33 (AB spin system, 2H, CH2NP, δa 2.26, δb
2.39); 2.69 (s, 3H, NCH3); 3.14 (s, 3H, NCH3); 3.38 (AX spin system,
1H, CH2N); 3.76 (AX spin system, 1H, CH2N); 7.21–7.82 (m, 13H,
ArH);13CNMR(CDCl3, 125 MHz)δ (ppm):22.4(NCH3);31.98(NCH3);
44.9 (PNCH3); 62.6 (CH2N); 68.9 [(CH2N); 3J(13C, 31P) = 15.1 Hz];
123.2 [C(1); 1J(13C, 31P) = 46.5 Hz]; 126.9 [C(4)]; 128.8 [C(3ꢁ,5ꢁ)];
131.5 [C(4ꢁ)]; 131.7 [C(5); 3J(13C, 31P) = 10.1 Hz]; 132.4 [C(3); 3J(13C,
31P) = 5.0 Hz]; 132.6 [C(1ꢁ); 1J(13C, 31P) = 32.7 Hz]; 134.9 [C(2ꢁ,6ꢁ)];
Experimental
The starting phosphine L2PPh2 (2) was synthesized accord-
ing to literature.[9] Starting PdCl2 and di-µ-chloro-bis{2-[(N,
N-dimethylamino)methyl]phenyl-C,N}-dipalladium(II) were pur-
chased from Sigma Aldrich and used as received. All reactions
were carried out under argon atmosphere, using standard Schlenk
techniques. Solvents were dried by standard methods and dis-
tilled prior to use. The 1H,13C, 31P NMR spectra were acquired with
a Bruker Avance 500 spectrometer in CDCl3 or C6D6. Appropri-
ate chemical shifts were calibrated on: 1H-residual peak of CHCl3
(δ = 7.25 ppm), 13C-residual peak of CHCl3 (δ = 77.23 ppm) and
31P-external H3PO4 (δ = 0.00 ppm). Electrospray mass spectra
(ESI/MS) were recorded in positive mode on an Esquire3000 ion
trap analyzer (Bruker Daltonics) in the range 100–600 m/z and in
the negative mode on the Platform quadrupole analyzer in the
range 100–800 m/z. The samples were dissolved in acetonitrile or
CHCl3 andanalyzedbydirectinfusionataflowrateof1–10 µl/min.
2
140.1 [C(6); J(13C, 31P) = 17.6 Hz]; 145.2 [C(2)]; 31P NMR (CDCl3,
145 MHz) δ (ppm): 19.4. (ESI+) MS: m/z 591 [M + K]+ (5%); m/z 575
[M + Na]+ (6%); m/z 517 [M − Cl]+ (10%). (ESI−) MS: m/z 587 [M
+ Cl]− (73%). Anal. calcd for C24H29Cl2N2PPd (554.80): C, 46.38; H,
5.50. Found: C, 46.45; H, 5.56%.
Preparation of {[2,6-(tBuOCH2)2C6H3]PPh2}Pd(Cl)[2-(Me2
NCH2)C6H4] (5)
Preparation of {[2,6-(tBuOCH2)2C6H3]PPh2 (1)
Di-µ-chlorobis{2-[(dimethylamino)methyl]phenyl-C,N}-dipalla-
dium(II) (0.25 g, 0.45 mmol) was added to the solution of 1
(0.68 g, 0.96 mmol) in THF (15 ml) and the mixture was stirred
for 1 day. The solvent was evaporated and the solid residuum
was washed with hexane (5 ml) to afford yellow crystals of 5.
Yield: 0.82 g (89%). M.p. 148–151 ◦C; 1H NMR (CDCl3, 500 MHz) δ
(ppm): 1.04 (s, 18H, CH3); 2.57 (s, 6H, NCH3); 3.58 (s, 2H, CH2N);
4.84 (s, 4H, CH2O); 6.53–8.04 (m, 17H, ArH); 13C NMR (CDCl3,
125 MHz) δ (ppm): 27.5 (CH3); 50.6 (NCH3); 64.2 [(CH2N);3J(13C,
31P) = 12.5 Hz]; 73.5 [(CH2O); 3J(13C, 31P) = 10.0 Hz]; 74.5 (OCMe3);
124.4 [C(1)-CN-chelate]; 131.6 [C(1); 1J(13C, 31P) = 60.4 Hz];
144.3 [C(1ꢁ);1J(13C, 31P) = 6.3 Hz]; 147.7 [C(2,6);2J(13C, 31P) =
2.5 Hz]; 151.8 [C(2)-CN-chelate]; 125.1, 126.4, 127.8, 135.5, 136.7
(Ar–pincer); 121.5, 123.8, 130.3, 130.8 (Ar–CN–chelate); 31P NMR
(CDCl3, 145 MHz) δ (ppm): 24.2; (ESI+) MS (m/z): 674 [M − Cl]+
(100%). Anal. calcd for C37H47ClNO2PPd (710.62): C, 62.83; H, 7.09.
Found: C, 62.98; H, 7.00%.
A 7.1 ml aliquot of 1.6 M n-BuLi was added dropwise to the hexane
(25 ml) solution of L1 (2.85 g, 11.3 mmol) and the solution was
stirred for 16 h. The Ph2PCl (1.76 ml, 9.7 mmol) was added to the
resulting hexane solution (20 ml) of L1Li and stirred for 1 day.
The suspension was filtered, the hexane solution was evaporated
and the yellow residue was washed with hexane (3◦ml) to give
1
pale yellow solid 1. Yield: 3.99 g (87%). M.p. 73–76 C, H NMR
(CDCl3, 360 MHz) δ (ppm): 1.01 (s, 18H, OtBu); 4.42 (s, 4H, CH2O);
6.99–7.73 (m, 13H, ArH); 13C NMR (CDCl3, 90 MHz) δ (ppm): 28.1
(CH3); 64.9 (CH2O;3J(13C, 31P) = 18.6 Hz); 73.4 (OCMe3); 128.3
[C(3,5);3J(13C, 31P) = 3.6 Hz]; 129.1 [C(3ꢁ,5ꢁ);3J(13C, 31P) = 7.9 Hz];
130.7[C(1);1J(13C,31P)=20.8 Hz];130.9[C(4ꢁ)];132.3[C(2ꢁ,6ꢁ);2J(13C,
31P) = 18.1 Hz]; 136.2 [C(1ꢁ);1J(13C, 31P) = 19.0 Hz]; 137.6 [C(4)];
147.6 [C(2,6) ;2J(13C, 31P) = 14.5 Hz]; 31P NMR (CDCl3, 202 MHz) δ
(ppm): −20.4. Anal. calcd for C28H35O2P (434.55): C, 77.29; H, 8.16.
Found: C, 77.32; H, 8.18%.
Preparation of {[2,6-(Me2NCH2)2C6H3]PPh2}Pd(Cl)[2-(Me2
NCH2)C6H4] (6)
Preparation of {[2,6-(tBuOCH2)2C6H3]PPh2}2PdCl2 (3)
Di-µ-chlorobis{2-[(dimethylamino)methyl]phenyl-C,N}-dipalla-
dium(II) (0.29 g, 0.53 mmol) was added to the solution of 2
(0.39 g, 1.05 mmol) in THF (15 ml) and the mixture was stirred for
4 days. The solvent was evaporated and the resulting product
was washed with pentane (5 ml) to◦afford yellow crystals of 6.
Yield: 0.57 g (85%). M.p. 129.4–133.0 C; 1H NMR (CDCl3, 500 MHz,
210 K) δ (ppm): 1.55 (s, 6H, NCH3); 1.99 (s, 6H, C,N–CH3); 2.31
(s, 2H, C,N–CH2); 2.56 (AB spin system, 2H, CH2NP, δa 2.41, δb
2.71); 3.17 (AX spin system, 1H, CH2N); 3.41 (s, 3H, NCH3); 3.95
(AX spin system, 1H, CH2N); 4.57 (s, 3H, NCH3); 6.52–7.53 (m, 17H,
ArH);13C NMR (CDCl3, 90 MHz, 300 K) δ (ppm): 45.3 (bs, NCH3); 47.3
(CH3 –CN–chelate); 63.1 (CH2N–CN–chelate); 68.1 (bs, CH2N);
123.4, 124.9, 128.5, 130.3, 131.7 and 137.2 (ArH–CN–chelate);
126.5 [bs, C(4)]; 133.1 [bs, C(3,5)]; 143.8 [bs, C(2,6)]; 147.9 [bs, C(1)];
31P NMR (CDCl3, 145 MHz) δ (ppm): 10.3; (ESI+) MS (m/z): 654 [M
+ H]+ (100%); 616 [M − Cl]+ (30%). Anal. calcd for C33H41ClN3PPd
(653.54): C, 60.51; H, 6.10. Found: C, 60.98; H, 6.28%.
PdCl2 (0.15 g, 0.85 mmol) was added to the solution of 1 (0.73 g,
1.69 mmol) in THF (20 ml) and the suspension was stirred for
4 days. The suspension was filtered and the solvent evaporated.
The resulting orange solid was washed with hexane (3 ml) to
afford crystals of 3. Yield: 0.81 g (93%). M.p. 172–175 ◦C; 1H NMR
(CDCl3, 500 MHz) δ (ppm): 0.87 (s, 36H, CH3); 4.45 (s, 8H, CH2O);
7.26–7.84 (m, 26H, ArH);13C NMR (CDCl3, 125 MHz) δ (ppm): 27.5
(CH3); 64.1 [CH2O;3J(13C, 31P) = 10.9 Hz]; 73.3 (OCMe3); 123.9 [C(1);
1J(13C, 31P) = 43.5 Hz]; 126.5 [C(3,5); 3J(13C, 31P) = 10.8 Hz]; 127.9
[C(3ꢁ,5ꢁ); 3J(13C, 31P) = 12.4 Hz]; 130.4 [C(4ꢁ)]; 130.6 [C(4)]; 131.8
[C(1ꢁ); 1J(13C, 31P) = 48.0 Hz]; 135.9 [C(2ꢁ,6ꢁ); 2J(13C, 31P) = 12.7 Hz];
2
143.8 [C(2,6); J(13C, 31P) = 9.0 Hz]; 31P NMR (CDCl3, 202 MHz) δ
(ppm): 14.7. (ESI+) MS: m/z 1011 [M − Cl]+ (100%). Anal. calcd for
C56H70Cl2O4P2Pd (1046.45): C, 63.39; H, 9.74. Found: C, 63.49; H,
9.94%.
c
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Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 173–179

Palladium(II) complexes of Y,C,Y-chelated phosphines
A General Procedure for the Suzuki–Miyaura Reaction
O. Steigelmann, A. H. White, Inorg. Chem. 1992, 31, 3656; e)
L.-J. Baker, G. A. Bowmaker, B. W. Skelton, A. H. White, J. Chem.
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C. E. Uzelmeier, A. Howard, Inorg. Chim. Acta. 1995, 240, 527;
g) L. J. Baker, R. C. Bott, G. A. Bowmaker, P. C. Healy, B. W. Skelton,
P. Schwerdtfeder, A. H. White, J. Chem. Soc. Dalton Trans. 1995,
1341 and references therein.
To a degassed solution of starting bromide (0.318 mmol) and
phenylboronic acid (53 mg, 0.32 mmol) in THF–H2O (10 ml, 4 : 1),
Pd(II) catalyst 3–6 (0.013 mmol) and Na2CO3 (34 mg, 0.318 mmol)
were added. The mixture was stirred for 24 h under Ar at 60 ◦C,
diluted with water and extracted with EtOAc (2 × 10 ml). The
combined organic layers were dried (Na2SO4) and subjected to GC
analysis (Table 2).
[2] M. Wada, S Higashizaki, A. Tsuboi, J. Chem. Soc. Synop. 1985, 38;
J. Chem. Res. Miniprint. 1985, 0467; b) M. Wada, A. Tsuboi, J. Chem.
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[3] J.-F. Ma, Y. Kojima, Y. Yamamoto, J. Organomet. Chem. 2000, 616,
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Crystallography
[4] a) Y. Yamamoto, R. Sato, M. Ohshima, F. Mysuo, C. Sudoh,
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[5] H. Weissman, L. J. W. Shimon, D. Milstein, Organometallics 2004, 23,
3931.
Crystals suitable for X-ray analyses were grown from THF (3) or
CH2Cl2 (4 and 6)–hexane solutions at +4 ◦C and compounds
crystallized as the corresponding solvates
[6] a) E. Lindner, A. Bader, Coord. Chem. Rev. 1991, 108, 27
and references therein; b) E. Lindner, M. Haustein, H. A. Mayer,
K. Gierling, R. Fawzi, M. Steimann, Organometallics 1995, 14, 2246;
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Organometallics 1994, 13, 5021; e) J.-S. Sun, C. E. Uzelmeier,
D. L. Ward, K. R. Dunbar, Polyhedron 1998, 17, 2049.
[7] Six-member rings: a) S. Maggini, Coord. Chem. Rev. 2009, 253, 1793
and references therein; b) O. del Campo, A. Carbayo, J. V. Cuevas,
G. García-Herbosa, A. Mun˜oz, Eur. J. Inorg. Chem. 2009, 2254 and
references therein; c) Ch. Uchiike, M. Ouchi, T. Ando, M. Kamigaito,
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H. Fan, M. Pink, D. J. Mindiola, Dalton Trans. 2009, 39, 358; f)
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47, 10479.
3 × (THF)3, 4 × (CH2Cl2)2 and 6 × CH2Cl2
The intensity data for single crystals were measured on four-
circle diffractometer KappaCCD with CCD area detector by
monochromatized MoKα radiation (λ = 0.71073 Å) at 150(2) K.
The crystallographic details are summarized in Table 1, and
empirical absorption corrections were applied (multiscan from
symmetry-related measurements). The structure was solved by
the direct methods (SIR97) and refined by a full-matrix least-
squares procedure based on F2 (SHELXL97). Hydrogen atoms
were mostly localized on a difference Fourier map; however, to
ensure uniformity of treatment of crystal, all hydrogens were
recalculated into idealized positions (riding model) and assigned
temperaturefactorsHiso(H) = 1.2Ueq(pivotatom)or1.5Ueq forthe
methyl moiety. There is disordered solvent (three THF molecules)
in the structure of compound 3. Attempts were made to model
this disorder or split it into two or more positions, but were
unsuccessful. PLATON/SQUEZZE15 was used to correct the data
for the presence of disordered solvent.
[8] a) R. Jambor, B. Kasˇna´, K. N. Kirschner, M. Schuermann, K. Jurkschat,
Angew. Chem. Int. Ed. 2008, 9, 1650; b) L. Dosta´l, R. Jambor,
˚
A. Ruzˇicˇka, A. Lycˇka, J. Brus, F. de Proft, Organometallics 2008, 23,
˚
6059; c) L. Dosta´l, R. Jambor, A. Ruzˇicˇka, J. Holecˇek, Organometallics
2008, 10, 2169.
Acknowledgments
[9] F. Carre´, C. Chuit, J. P. R. Corriu, A. Mehdi, C. Reye´. J. Organomet.
Chem. 529, 1997, 59.
This research was supported by the Czech Science Foundation
(project no. GA370468 and GA207/10/0215) and the Ministry of
Education, Youth and Sport of the Czech Republic (projects no.
MSM0021627501).
[10] For most recent structures see for example: a) Y. Qin,
H. Lang, J. J. Vittal, G. K. Tan, S. Selvaratnam, A. J. P. White,
D. J. Williams, P. H. Lejny, Organometallics 2003, 22, 3944;
b) V. V. Dunina, O. N. Gorunova, Y. K. Grishin, L. G. Kuzmina,
A. V. Churakov, A. V. Kuchin, J. A. K. Howard, Russ. Chem. Bull.
2005, 2010; c) A. Apfelbacher, P. Braunstein, L. Brissieux, R. Walter,
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Tetrahedron: Asymm. 1999, 10, 2797; e) V. V. Dunina, L. G. Kuzmina,
M. Y. Rubina, Y. K. Grishin, Y. A. Veits, E. I. Kazakova, Tetrahedron:
Asymm 1999, 10, 1483; f) A. Mentek, R. D. W. Kemmitt, J. Fawcett,
D. R. Russell, J. Mol. Struct. 2004, 693, 241.
[11] a)N. Miyaura, K. Yamada, A. Suzuki, TetrahedronLett. 1979, 20, 3437;
b) N. Miyaura, A. Suzuki, Chem. Commun. 1979, 866; b) A. Suzuki,
Pure Appl. Chem. 1991, 63, 419; c) N. Miyaura, A. Suzuki, Chem. Rev.
1995, 95, 2457; d) A. Suzuki, J. Organomet. Chem. 1999, 576, 147;
e) N. Miyaura, Top. Curr. Chem. 2002, 219, 11; f) S. Kotha, K. Lahiri,
D. Kashinath, Tetrahedron 2002, 58, 9633.
Supporting Information
Supporting information can be found in the online version of this
article. CCDC-773072 (for 3), −773073 (for 4), −773071 (for 6) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.ac.uk/data request/cif.
[12] a) F. Buresˇ, W. B. Schweizer, J. C. May, C. Boudon, J.-P. Gisselbrecht,
M. Gross, I. Biaggio, F. Diederich, Chem. Eur. J. 2007, 13, 5378; b)
F. Buresˇ, W. B. Schweizer, C. Boudon, J.-P. Gisselbrecht, M. Gross,
F. Diderich, Eur. J. Org. Chem. 2008, 994.
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c
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