Catalytic Suzuki coupling reactions by amido phosphine complexes of palladium

Article abstract of DOI:10.1021/om0492395

Treatment of PdCl₂(PhCN)₂ with [NP]Li(THF) ₂([NP]^- = N-(2-(diphenylphosphino)phenyl)-2,6-diisopropylanilide) in THF affords dimeric {[NP]PdCl}₂, which reacts with tricyclohexylphosphine to produce [NP]PdCl(PCy₃). The two phosphorus donors in [NP]PdCl(PCy ₃) are mutually cis, as indicated by the solution NMR and X-ray crystallographic studies. Both {[NP]PdCl}₂ and [NP]PdCl(PCy ₃) are highly active catalyst precursors for Suzuki coupling reactions of a wide array of aryl halides, including those featuring electronically deactivated and sterically hindered characteristics.

Full text of DOI:10.1021/om0492395

Organometallics 2005, 24, 353-357
353
Catalytic Suzuki Coupling Reactions by Amido
Phosphine Complexes of Palladium
Lan-Chang Liang,* Pin-Shu Chien, and Mei-Hui Huang
Department of Chemistry and Center for Nanoscience & Nanotechnology,
National Sun Yat-sen University, Kaohsiung 80424, Taiwan
Received October 2, 2004
Treatment of PdCl2(PhCN)2 with [NP]Li(THF)2 ([NP]- ) N-(2-(diphenylphosphino)phenyl)-
2,6-diisopropylanilide) in THF affords dimeric {[NP]PdCl}2, which reacts with tricyclohexyl-
phosphine to produce [NP]PdCl(PCy3). The two phosphorus donors in [NP]PdCl(PCy3) are
mutually cis, as indicated by the solution NMR and X-ray crystallographic studies. Both
{[NP]PdCl}2 and [NP]PdCl(PCy3) are highly active catalyst precursors for Suzuki coupling
reactions of a wide array of aryl halides, including those featuring electronically deactivated
and sterically hindered characteristics.
Chart 1. Representative Examples of Phosphine
Palladacycles
Introduction
Palladium-catalyzed cross-coupling reactions are some
of the most versatile methods for the formation of
carbon-carbon bonds.1-4 The search for appropriate
ancillary ligands that facilitate the generation of highly
active catalyst precursors is of current interest. Signifi-
cant progress has been made recently with the employ-
ment of ligands such as electron-rich, sterically hindered
phosphines5-9 and N-heterocyclic carbenes.10-14 Ortho-
palladated phosphine complexes constitute an intrigu-
ing class of compounds, as catalyst activity and reaction
selectivity can be efficiently probed by systematic ligand
modifications.15 Chart 1 depicts representative examples
of the phosphine palladacycles 1 and 2.16-18 We envi-
sioned that electronic modification of compounds 1 and
2 with a monoanionic amido phosphine ligand such as
those illustrated in 3 and 4 would also lead to catalyti-
cally active species for cross-coupling reactions. We
recently demonstrated that compounds of the type 3 are
highly active catalysts for Heck olefination of aryl
halides.19 In a parallel pursuit, we have set out to
examine the possibility of 4 for catalytic carbon-carbon
bond formation, with the current focus on Suzuki
coupling reactions.20 In this contribution, we describe
our results in this regard with the amido phosphine
ligand being N-(2-(diphenylphosphino)phenyl)-2,6-di-
isopropylanilide ([NP]-).
* To whom correspondence should be addressed. E-mail: lcliang@
mail.nsysu.edu.tw. Fax: +886-7-5253908.
(1) Metal-Catalyzed Cross-Coupling Reactions; Diederich, F., Stang,
P. J., Eds.; Wiley-VCH: Weinheim, Germany, 1998.
(2) Miyaura, N. Top. Curr. Chem. 2002, 219.
(3) Littke, A. F.; Fu, G. C. Angew. Chem., Int. Ed. 2002, 41, 4176-
4211.
(4) Scrivanti, A.; Beghetto, V.; Matteoli, U.; Antonaroli, S.; Marini,
A.; Mandoj, F.; Paolesse, R.; Crociani, B. Tetrahedron Lett. 2004, 45,
5861-5864.
Results and Discussion
(5) Littke, A. F.; Dai, C. Y.; Fu, G. C. J. Am. Chem. Soc. 2000, 122,
4020-4028.
21
The metathetical reaction of [NP]Li(THF)2 with
(6) Liu, S. Y.; Choi, M. J.; Fu, G. C. Chem. Commun. 2001, 2408-
2409.
PdCl2(PhCN)2 in THF at -35 °C produced diamagnetic,
dimeric {[NP]PdCl}2 as a greenish blue solid in quan-
titative yield. The chloride complex was fully character-
ized by multinuclear NMR spectroscopy and elemental
analysis. Analogous to the nickel chemistry of [NP]-,22
the isopropylmethyl groups in {[NP]PdCl}2 are diaste-
reotopic, as evidenced by 1H and 13C NMR spectroscopy,
implying restricted rotation about the N-Ar bond.
Without crystallographic data, we tentatively formulate
(7) Old, D. W.; Wolfe, J. P.; Buchwald, S. L. J. Am. Chem. Soc. 1998,
120, 9722-9723.
(8) Walker, S. D.; Barder, T. E.; Martinelli, J. R.; Buchwald, S. L.
Angew. Chem., Int. Ed. 2004, 43, 1871-1876.
(9) Yin, J. J.; Rainka, M. P.; Zhang, X. X.; Buchwald, S. L. J. Am.
Chem. Soc. 2002, 124, 1162-1163.
(10) Zhang, C. M.; Huang, J. K.; Trudell, M. L.; Nolan, S. P. J. Org.
Chem. 1999, 64, 3804-3805.
(11) Herrmann, W. A.; Reisinger, C. P.; Spiegler, M. J. Organomet.
Chem. 1998, 557, 93-96.
(12) Weskamp, T.; Bohm, V. P.; Herrmann, W. A. J. Organomet.
Chem. 1999, 585, 348-352.
(13) Biakey, S. B.; MacMillan, D. W. C. J. Am. Chem. Soc. 2003,
125, 6046-6047.
(18) Ohff, M.; Ohff, A.; van der Boom, M. E.; Milstein, D. J. Am.
Chem. Soc. 1997, 119, 11687-11688.
(14) Navarro, O.; Kelly, R. A.; Nolan, S. P. J. Am. Chem. Soc. 2003,
125, 16194-16195.
(19) Huang, M.-H.; Liang, L.-C. Organometallics 2004, 23, 2813-
2816.
(15) van der Boom, M. E.; Milstein, D. Chem. Rev. 2003, 103, 1759-
1792.
(20) The catalytic Suzuki couplings mediated by 3 will be reported
separately.
(16) Beller, M.; Fischer, H.; Herrmann, W. A.; Ofele, K.; Brossmer,
C. Angew. Chem., Int. Ed. Engl. 1995, 34, 1848-1849.
(17) Gibson, S.; Foster, D. F.; Eastham, G. R.; Tooze, R. P.; Cole-
Hamilton, D. J. Chem. Commun. 2001, 779-780.
(21) Liang, L.-C.; Lee, W.-Y.; Hung, C.-H. Inorg. Chem. 2003, 42,
5471-5473.
(22) Liang, L.-C.; Lee, W.-Y.; Yin, C.-C. Organometallics 2004, 23,
3538-3547.
10.1021/om0492395 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 12/23/2004

354 Organometallics, Vol. 24, No. 3, 2005
Liang et al.
such as the phosphinite derivative 5 (80.24(7)°).24 As
expected, the diisopropylphenyl ring is roughly perpen-
dicular to the N-phenylene-P plane with a dihedral
angle of 88.6°, thereby providing steric protection for
the axial faces of the palladium center.
To survey the reaction parameters for the catalytic
Suzuki couplings, we chose to examine four bases
(K3PO4‚H2O, K3PO4, K2CO3, and Cs2CO3) and two
solvents (dioxane and toluene). Heating at elevated
temperatures was required, due likely to the generally
low solubility of these bases in the solvents that we
screened. We found that reactions performed in dioxane
with K3PO4‚H2O or K3PO4 as the base at 110 °C appear
to be superior to the others.25
The scope of the Suzuki coupling with respect to the
aryl halide component was investigated (Table 1). A
number of aryl iodides, bromides, and chlorides have
been successfully coupled with arylboronic acids. Specif-
ically, {[NP]PdCl}2 is an effective catalyst precursor for
the coupling of activated, unactivated, and deactivated
bromides and iodides (entries 1-21). Extremely high
turnover numbers of up to 6.8 × 107 (per Pd, entry 19)
and turnover frequencies of up to 3.1 × 106 (per Pd per
hour, entry 18) are realized for the coupling of electroni-
cally deactivated 4-bromoanisole with phenylboronic
acid. This condition also allows for the coupling of
heterocyclic (entry 5) and 2,6-disubstituted (entries
9-12) substrates. Of particular interest is the formation
of tri-ortho-substituted biaryls (entries 11 and 12) at
efficient turnover rates, although the palladium catalyst
is supported by a sterically demanding amido phosphine
ligand.
The coupling of aryl chlorides is also achieved (entries
22-31). Although both {[NP]PdCl}2 and [NP]PdCl-
(PCy3) exhibit comparable activities for the activated
substrates (e.g., entry 22 versus entry 25), the latter
complex outperforms the former with respect to the
unactivated and deactivated substrates (e.g., entry 23
versus entry 27). The higher efficiency of [NP]PdCl-
(PCy3) relative to {[NP]PdCl}2 is attributed to the
electronic modification of the coordinated tricyclohexy-
lphosphine.26 Consistent with the phenomenal stability
of these palladium compounds, the coupling reactions
can be conducted under aerobic conditions in the pres-
ence of water (entry 1). No palladium black was
observed in any of the attempts.
Figure 1. Molecular structure of [NP]PdCl(PCy3) with
thermal ellipsoids drawn at the 35% probability level.
Selected bond distances (Å) and angles (deg): Pd(1)-N(1)
)
2.079(2), Pd(1)-P(1) ) 2.2532(8), Pd(1)-P(2) )
2.3131(8), Pd(1)-Cl(1) ) 2.3565(7); N(1)-Pd(1)-P(1) )
82.09(7), N(1)-Pd(1)-P(2) ) 176.26(7), P(1)-Pd(1)-P(2)
) 100.04(3), N(1)-Pd(1)-Cl(1) ) 89.86(7), P(1)-Pd(1)-
Cl(1) ) 171.94(3), P(2)-Pd(1)-Cl(1) ) 88.01(3).
this compound as a chloride-bridged dimer, presumably
in the solid state, on the basis of its facile association
with Lewis bases. Addition of PCy3 to an ethereal
solution of {[NP]PdCl}2 generated quantitatively [NP]-
PdCl(PCy3) as a brown crystalline solid. The room-
temperature 31P{1H} NMR spectrum of [NP]PdCl(PCy3)
exhibits two doublet resonances with equal intensity at
52.20 and 36.19 ppm for [NP]- and PCy3, respectively.
The coupling constant of 15 Hz is consistent with a cis
relationship between the two phosphorus donors. Both
{[NP]PdCl}2 and [NP]PdCl(PCy3) are thermally stable
and are not sensitive to air or water. For instance, no
decomposition was observed when {[NP]PdCl}2 (5.1 mM
in dioxane) or [NP]PdCl(PCy3) (7.0 mM in dioxane) was
heated to 120 °C for >2 days in the presence of water
(2000 equiv!) under aerobic conditions, as indicated by
31P{1H} NMR spectroscopy. The unusual stability of
these palladium amides toward protonation in the
presence of water is remarkable,23 a result that is
ascribable to the association of the phosphorus donor
of the [NP]- ligand to the palladium center.
Single crystals of [NP]PdCl(PCy3) suitable for X-ray
diffraction analysis were grown from a concentrated
dioxane solution at room temperature. As depicted in
Figure 1, the solid-state structure is consistent with the
solution structure observed by NMR spectroscopy. The
coordinated PCy3 is cis to the phosphorus donor of the
amido phosphine ligand, with a P-Pd-P angle of
100.04(3)°. The palladium center lies perfectly on the
square plane defined by the four donor atoms. The
N(1)-Pd(1)-P(1) angle of 82.09(7)° is similar to the
corresponding values of five-membered palladacycles
To gain insights into the reaction mechanism, com-
petitive experiments involving activated, unactivated,
and deactivated aryl bromides with phenylboronic acid
in dioxane at 110 °C were performed, leading to Ham-
mett plots with reaction constants F of 0.4847 for {[NP]-
(23) Fryzuk, M. D.; Macneil, P. A. J. Am. Chem. Soc. 1981, 103,
3592-3593.
(24) Bedford, R. B.; Hazelwood, S. L.; Horton, P. N.; Hursthouse,
M. B. Dalton 2003, 4164-4174.
(25) Attempted catalysis runs in a water/dioxane mixture at room
temperature led to turnover frequencies much lower than those
reported in Table 1, due to the formation of bilayers in which the
aqueous potassium phosphate monohydrate solution is separated from
the dioxane solution that contains the other starting materials.
Increasing the reaction temperature of such solutions to 110 °C,
however, proved as efficient as those performed in the absence of water.
(26) Controlled experiments showed that the turnover frequencies
for the couplings of aryl chlorides catalyzed by [NP]PdCl(PPh3) are
notably lower than those found for [NP]PdCl(PCy3), suggesting the
participation of PCy3 in the catalytic cycles. Spectroscopic data for [NP]-
2
PdCl(PPh3): 31P{1H} NMR (1,4-dioxane, 80.953 MHz) δ 54.13 (d, JPP
2
) 15 Hz, NP), 27.85 (d, JPP ) 15 Hz, PPh3).

Suzuki Couplings by Amido Phosphine Complexes of Pd
Organometallics, Vol. 24, No. 3, 2005 355
Table 1. Catalytic Suzuki Reactions of Aryl Halides with Arylboronic Acidsa
entry
catalystb (amt, mol %)
ArX
R
t (h)
TON
1 000
yield (%)c
100 (100)d
100 (100)
100
100 (94)
100
100
100 (96)
100
89 (89)
73
1
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
A (0.000 5)
A (0.000 05)
A (0.000 005)
A (0.000 000 5)
A (0.000 000 5)
A (0.05)
A (0.05)
A (0.05)
A (0.05)
B (0.1)
4-BrC6H4NO2
4-BrC6H4C(O)Me
4-BrC6H4CHO
2-BrC6H4F
2-bromothiophene
PhBr
4-BrC6H4Me
H
1
1
2
H
H
H
H
H
H
H
H
H
Me
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
1 000
1 000
1 000
1 000
1 000
1 000
1 000
890
3
1
4
1
5
1
6
1
7
1
8
BrC6H3Me2-3,5
BrC6H2Me3-2,4,6
1
9
1
i
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
BrC6H2 Pr3-2,4,6
12
24
24
1
730
BrC6H2Me3-2,4,6
820
82
34
i
BrC6H2 Pr3-2,4,6
340
4-BrC6H4OMe
4-BrC6H4NMe2
4-BrC6H4OMe
4-BrC6H4OMe
4-BrC6H4OMe
4-BrC6H4OMe
4-BrC6H4OMe
PhI
1 000
980
100 (93)
98 (86)
96
12
1
1
96 000
350 000
10 000 000
37 000 000
68 000 000
1 000
1 000
840
35
12
12
24
12
12
24
24
24
24
24
24
24
24
24
24
100
37
68
100
4-IC6H4OMe
4-ClC6H4NO2
PhCl
4-ClC6H4C(O)Me
4-ClC6H4NO2
4-ClC6H4CHO
PhCl
2-ClC6H4Me
4-ClC6H4Me
ClC6H3Me2-3,5
4-ClC6H4OMe
100 (99)
84
110
11
990
99
B (0.1)
970
97
B (0.1)
950
95
B (0.1)
530
53
B (0.1)
550
55
B (0.1)
540
54
B (0.1)
450
45
B (0.1)
420
42
a Reaction conditions: 1.0 equiv of aryl halide, 1.5 equiv of boronic acids, 2.0 equiv of K3PO4‚H2O, 4 mL of 1,4-dioxane. Reaction times
have not been minimized. b Catalyst A, {[NP]PdCl}2; catalyst B, [NP]PdCl(PCy3). c Determined by GC, based on aryl halides; average of
two runs. Yields in parentheses refer to isolated yields; average of two runs. d Reaction run under aerobic conditions in the presence of
0.5 mL of water.
Figure 2. Hammett plot for the coupling of 4-substituted
Figure 3. Hammett plot for the coupling of 4-substituted
phenyl bromides with phenylboronic acid catalyzed by
phenyl bromides with phenylboronic acid catalyzed by [NP]-
{[NP]PdCl}2 in dioxane at 110 °C, providing the reaction
constant F ) 0.4847.
PdCl(PCy3) in dioxane at 110 °C, providing the reaction
constant F ) 0.6620.
PdCl}2 (Figure 2) and 0.6620 for [NP]PdCl(PCy3) (Fig-
Conclusions
ure 3). The low F value likely suggests that aryl halide
oxidative addition is not the rate-determining step in
this process. This result is consistent with that obtained
from the Heck olefination catalyzed by 3.19 A much
larger value of F ) 5.2 was reported for oxidative
addition of aryl halides to Pd0 supported by a 1,3-bis-
(diisopropylphosphino)propane ligand.27 Similar low F
values were also reported for other catalytic Suzuki
coupling reactions, in which transmetalation was sug-
gested to be slow.28,29
In summary, we have demonstrated that the diaryl-
amido phosphine complexes of palladium are highly
effective catalysts for Suzuki coupling reactions. It is
somewhat surprising that these palladium compounds
are air- and water-stable at elevated temperatures,
given the inherent reactivity of the palladium-amide
bond. A diverse array of aryl halides, including sterically
hindered, electronically deactivated, and heterocyclic
substrates, have been successfully coupled in this
(27) Portnoy, M.; Milstein, D. Organometallics 1993, 12, 1665-1673.
(28) Weissman, H.; Milstein, D. Chem. Commun. 1999, 1901-1902.
(29) Zim, D.; Lando, V. R.; Dupont, J.; Monteiro, A. L. Org. Lett.
2001, 3, 3049-3051.

356 Organometallics, Vol. 24, No. 3, 2005
Liang et al.
dioxane (3 mL) was added to a green solution of {[NP]PdCl}2
(81 mg, 0.07 mmol) in 1,4-dioxane (3 mL) at room temperature.
The reaction solution was stirred at room temperature for 3
min to give a dark brown solution. The solution was then kept
at room temperature for 2 days without stirring to allow for
the crystallization of the product. Brown crystals thus obtained
were suitable for X-ray diffraction study; yield 90 mg (75%).
Method 2. The reaction may also be conducted in THF
solution under conditions similar to those described in method
process. Extremely low catalyst loadings for the coupling
of 4-bromoanisole are particularly attractive. In view
of the ease with which the substituents at the donor
atoms in [NP]- can be readily modified, we anticipate
that further enhancements in catalytic activity will be
promising. Studies along this line are currently under-
way.
Experimental Section
1
1. The product was isolated as a brown solid; yield 92%. H
NMR (CDCl3, 500 MHz): δ 8.03 (dd, 4, Ar), 7.56 (m, 2, Ar),
7.50 (m, 4, Ar), 7.14 (s, 3, Ar), 6.75 (t, 1, Ar), 6.60 (dd, 1, Ar),
6.09 (t, 1, Ar), 5.70 (dd, 1, Ar), 3.40 (septet, 2, CHMe2), 2.20
(m, 3, Cy), 1.60 (m, 15, Cy), 1.52 (m, 6, Cy), 1.30 (d, 6, CHMe2),
1.13 (m, 3, Cy), 0.94 (d, 6, CHMe2), 0.89 (m, 6, Cy). 31P{1H}
General Procedures. Unless otherwise specified, all ex-
periments were performed under nitrogen using standard
Schlenk or glovebox techniques. All solvents were reagent
grade or better and were purified by standard methods. The
21
compound [NP]Li(THF)2 was prepared by following the
2
NMR (CDCl3, 202.31 MHz): δ 52.20 (d, JPP ) 15.38, NP),
procedures reported previously. All other chemicals were used
as received from commercial vendors. The NMR spectra were
recorded on Varian instruments. Chemical shifts (δ) are listed
as parts per million downfield from tetramethylsilane, and
coupling constants (J) are in hertz. 1H NMR spectra are
referenced using the residual solvent peak at δ 7.16 for C6D6
and δ 7.27 for CDCl3. 13C NMR spectra are referenced using
the residual solvent peak at δ 128.39 for C6D6 and δ 77.23 for
CDCl3. The assignment of the carbon atoms for all compounds
is based on DEPT 13C NMR spectroscopy. 31P and 19F NMR
spectra are referenced externally using 85% H3PO4 at δ 0 and
CFCl3 in CHCl3 at δ 0, respectively. Routine coupling constants
are not listed. All NMR spectra were recorded at room
temperature in specified solvents. High-resolution mass spec-
tra were recorded on a Bruker Apex mass spectrometer.
Elemental analysis was performed on a Heraeus CHN-O Rapid
analyzer. The Suzuki coupling reactions were analyzed by GC
on a Varian Chrompack CP-3800 instrument equipped with a
CP-Sil 5 CB chrompack capillary column and the yields
calculated versus aryl halides or dodecane as an internal
standard. The identity of the products was confirmed by
comparison with authentic samples.
36.19 (d, 2JPP ) 15.38, PCy3). 31P{1H} NMR (1,4-dioxane, 80.95
2
2
MHz): δ 51.45 (d, JPP ) 14.65, NP), 36.01 (d, JPP ) 14.41,
PCy3). 31P{1H} NMR (THF, 80.95 MHz): δ 51.36 (d, JPP
)
2
14.65, NP), 35.69 (d, 2JPP ) 14.65, PCy3). 13C{1H} NMR (CDCl3,
125.70 MHz): δ 164.94 (d, JCP ) 25.39, C), 147.36 (s, C), 145.66
(s, C), 134.35 (d, JCP ) 11.82, CH), 132.80 (s, CH), 131.95 (s,
CH), 131.38 (s, CH), 131.24 (d, JCP ) 49.40, C), 128.58 (d, JCP
) 10.94, CH), 124.33 (s, CH), 122.61 (s, CH), 114.09 (d, JCP
)
14.08, CH), 114.03 (d, JCP ) 57.19, C), 112.13 (d, JCP ) 8.67,
1
CH), 34.89 (d, JCP ) 21.37, PCH), 29.82 (s, CH2), 28.08 (s,
CHMe2), 27.16 (d, 2JCP ) 10.94, CH2), 26.18 (s, CH2), 24.40 (s,
CHMe2), 23.74 (s, CHMe2). Anal. Calcd for C48H64ClNP2Pd-
(dioxane)0.5: C, 66.51; H, 7.59; N, 1.55. Found: C, 66.17; H,
7.65; N, 1.48.
General Procedures for the Suzuki Reactions Out-
lined in Table 1. A Schlenk flask was sequentially charged
with the palladium catalyst {[NP]PdCl}2 or [NP]PdCl(PCy3)
(1.0 mg for each single experiment), aryl halide (1.0 equiv),
arylboronic acid (1.5 equiv), potassium phosphate monohydrate
(2.0 equiv), 1,4-dioxane (4 mL), and a magnetic stir bar. The
flask was capped with a glass stopper and heated in an oil
bath at 110 °C with stirring for a specified period of time. After
being cooled to room temperature, the reaction mixture was
diluted with diethyl ether (8 mL), filtered through a pad of
Celite, and treated with aqueous NaOH solution (3 mL, 1 M).
The diethyl ether solution was separated from the aqueous
layer, dried over MgSO4, and evaporated to dryness under
reduced pressure to afford the desired product. For experi-
ments with low catalyst loading (entries 15-19), stock solu-
tions of appropriate concentrations were prepared by dissolv-
ing 1.0 mg of the palladium catalyst in appropriate amounts
of dioxane and used for each independent run.
Biphenyl.30 1H NMR (CDCl3, 500 MHz): δ 7.74 (d, 4, J )
8.0 Hz, ortho), 7.57 (t, 4, J ) 6.9 Hz, meta), 7.48 (t, 2, J ) 7
Hz, para). 13C NMR (CDCl3, 125.70 MHz): δ 141.17 (ipso),
128.71 (CH), 127.20 (CH, para), 127.11 (CH). HRMS (EI):
calcd for C12H10 m/z 154.0783, found m/z 154.0779.
4-(Dimethylamino)biphenyl.31 1H NMR (CDCl3, 500
MHz): δ 7.62 (d, 2, J ) 7.8 Hz, ortho C6H5), 7.57 (d, 2, J ) 8.5
Hz), 7.45 (t, 2, J ) 7.8 Hz, meta C6H5), 7.31 (t, 1, J ) 7.5 Hz,
para C6H5), 6.86 (d, 2, J ) 8.5 Hz), 3.04 (s, 6, NMe2). 13C NMR
(CDCl3, 125.70 MHz): δ 149.91, 141.17, 129.25, 128.61 (CH),
127.66 (CH), 126.25 (CH), 125.96 (para C6H5), 112.78 (CH),
40.56 (NMe2). HRMS (EI): calcd for C14H15N m/z 197.1204,
found m/z 197.1201.
X-ray Crystallography. Data for [NP]PdCl(PCy3) were
collected on a Bruker-Nonius Kappa CCD diffractometer with
graphite-monochromated Mo KR radiation (λ ) 0.7107 Å).
Structures were solved by direct methods and refined by full-
matrix least-squares procedures against F2 using the WinGX
crystallographic software package. All full-weight non-hydro-
gen atoms were refined anisotropically. Hydrogen atoms were
placed in calculated positions.
Synthesis of {[NP]PdCl}2. Solid PdCl2(PhCN)2 (100 mg,
0.261 mmol) was dissolved in THF (4 mL) and cooled to -35
°C. To this was added a solution of [NP]Li(THF)2 (153 mg,
0.261 mmol) in THF (4 mL) at -35 °C. The reaction mixture
was naturally warmed to room temperature with stirring.
After being stirred at room temperature for 1 h, the solution
was evaporated to dryness under reduced pressure. The solid
residue was extracted with CH2Cl2 (8 mL) and the extract
filtered through a pad of Celite. Solvent was removed in vacuo,
and the solid was washed with pentane (5 mL × 2), affording
1
the product as a blue-green solid; yield 148.8 mg (98.7%). H
NMR (C6D6, 500 MHz): δ 7.67 (m, 4, Ar), 7.13 (m, 1, Ar), 7.09
(m, 2, Ar), 7.03 (m, 2, Ar), 6.97 (m, 4, Ar), 6.76 (m, 2, Ar), 6.22
(m, 1, Ar), 6.09 (m, 1, Ar), 3.74 (septet, 2, CHMe2), 1.29 (d, 6,
CHMe2), 1.12 (d, 6, CHMe2). 13C{1H} NMR (C6D6, 125.70
MHz): δ 168.41 (d, JCP ) 24.60, C), 147.69 (s, C), 146.60 (s,
C), 134.22 (s, CH), 134.00 (d, JCP ) 5.52, CH), 133.43 (s, CH),
4-Acetylbiphenyl.31 1H NMR (CDCl3, 500 MHz): δ 8.04
(d, 2, J ) 8.5 Hz), 7.69 (d, 2, J ) 8.5 Hz), 7.64 (d, 2, J ) 7.5
Hz, ortho C6H5), 7.48 (t, 2, J ) 7.5 Hz, meta C6H5), 7.41 (t, 1,
J ) 7.3 Hz, para C6H5), 2.64 (s, 3, CH3). 13C NMR (CDCl3,
125.70 MHz): δ 197.65 (CdO), 145.65, 139.75, 135.74, 128.87
(CH), 128.83 (CH), 128.15 (para C6H5), 127.17 (CH), 127.11
131.71 (s, CH), 130.56 (d, JCP ) 58.99, C), 129.14 (d, JCP
6.28, CH), 126.70 (s, CH), 124.38 (s, CH), 115.63 (d, JCP
)
)
16.44, CH), 115.01 (d, JCP ) 8.16, CH), 109.26 (d, JCP ) 61.75,
C), 28.92 (s, CHMe2), 24.96 (s, CHMe2), 24.54 (s, CHMe2). 31P-
{1H} NMR (C6D6, 202.31 MHz): δ 57.76. 31P{1H} NMR (THF,
80.95 MHz): δ 53.99. Anal. Calcd for (C30H31ClNPPd)2: C,
62.29; H, 5.40; N, 2.42. Found: C, 62.54; H, 5.47; N, 2.45.
Synthesis of [NP]PdCl(PCy3). Method 1. A colorless
solution of tricyclohexylphosphine (39 mg, 0.14 mmol) in 1,4-
(30) Li, G. Y. J. Organomet. Chem. 2003, 653, 63-68.
(31) Najera, C.; Gil-Molto´, J.; Karlstro¨m, S.; Falvello, L. R. Org. Lett.
2003, 5, 1451-1454.

Suzuki Couplings by Amido Phosphine Complexes of Pd
Organometallics, Vol. 24, No. 3, 2005 357
(CH), 26.56 (CH3). HRMS (EI): calcd for C14H12O m/z 196.0888,
found m/z 196.0885.
MHz): δ -119.38. HRMS (EI): calcd for C12H9F m/z 172.0688,
found m/z 172.0685.
4-Methoxybiphenyl.7 1H NMR (CDCl3, 500 MHz): δ 7.61
(d, 2, J ) 8.5 Hz), 7.59 (d, 2, J ) 8.5 Hz), 7.47 (t, 2, J ) 7.8
Hz, meta C6H5), 7.36 (t, 1, J ) 7.5 Hz, para C6H5), 7.03 (d, 2,
J ) 8.5 Hz), 3.89 (s, 3, CH3). 13C NMR (CDCl3, 125.70 MHz):
δ 159.10, 140.77, 133.72, 128.68 (CH), 128.10 (CH), 126.69
(CH), 126.61 (para C6H5), 114.16 (CH), 55.27 (CH3). HRMS
(EI): calcd for C13H12O m/z 184.0888, found m/z 184.0884.
4-Methylbiphenyl.32 1H NMR (CDCl3, 500 MHz): δ 7.79
(d, 2, J ) 8.3 Hz), 7.70 (d, 2, J ) 8.0 Hz), 7.62 (t, 2, J ) 6.8
Hz, meta C6H5), 7.52 (t, 1, J ) 7.5 Hz, para C6H5), 7.44 (d, 2,
J ) 8.0 Hz), 2.59 (s, 3, CH3). 13C NMR (CDCl3, 125.70 MHz):
δ 141.08, 138.28, 136.88, 129.43 (CH), 128.65 (CH), 126.92
(CH), 126.89 (CH), 21.02 (CH3). HRMS (EI): calcd for C13H12
m/z 168.0939, found m/z 168.0936.
2-Phenylthiophene.37 1H NMR (CDCl3, 500 MHz): δ 7.72
(d, 2, J ) 7.0 Hz, ortho C6H5), 7.47 (t, 2, J ) 7.5 Hz, meta
C6H5), 7.41 (dd, 1, J ) 3.5 Hz, J ) 1.0 Hz), 7.381 (t, 1, J ) 7.5
Hz, para C6H5), 7.35 (dd, 1, J ) 5.0 Hz, J ) 1.0 Hz), 7.17 (dd,
1, J ) 5.0 Hz, J ) 3.5 Hz). 13C NMR (CDCl3, 125.70 MHz): δ
144.35, 134.33, 128.82 (CH), 127.94 (CH), 127.38 (CH), 125.88
(CH), 124.73 (CH), 123.01 (CH). HRMS (EI): calcd for C10H8S
m/z 160.0347, found m/z 160.0341.
4-Phenylbenzaldehyde.38 1H NMR (CDCl3, 500 MHz): δ
10.05 (s, 1, CHdO), 7.95 (d, 2, J ) 8.0 Hz), 7.74 (d, 2, J ) 8.0
Hz), 7.64 (d, 2, J ) 7.5 Hz), 7.49 (t, 2, J ) 7.6 Hz, meta C6H5),
7.43 (t, 1, J ) 7.5 Hz, para C6H5). 13C NMR (CDCl3, 125.70
MHz): δ 191.78 (CdO), 146.96, 139.49, 135.02, 130.11 (CH),
128.87 (CH), 128.34 (para C6H5), 127.49 (CH), 127.19 (CH).
HRMS (EI): calcd for C13H10O m/z 182.0732, found m/z
182.0727.
3,5-Dimethylbiphenyl.39 1H NMR (CDCl3, 500 MHz): δ
7.89 (d, 2, J ) 8.3 Hz, ortho C6H5), 7.71 (t, 2, J ) 7.8 Hz, meta
C6H5), 7.62 (t, 1, para C6H5), 7.54 (s, 2, ortho C6H3Me2), 7.29
(s, 1, para C6H3Me2), 2.68 (s, 6, C6H3Me2). 13C NMR (CDCl3,
125.70 MHz): δ 141.41, 141.19, 138.07, 128.83 (CH), 128.56
(CH), 127.09 (CH), 126.98 (CH), 125.04 (CH), 21.30 (Me).
HRMS (EI): calcd for C14H14 m/z 182.1096, found m/z 182.1092.
Representative Example of Experimental Details for
the Competition Reactions. A Schlenk flask was charged
with [NP]PdCl(PCy3) (1.0 mg, 1.16 µmol, 0.4 mol % with
respect to each of the aryl bromides), aryl bromides (0.291
mmol for each), phenylboronic acid (1.16 mmol), potassium
phosphate monohydrate (2.33 mmol), 1,4-dioxane (4 mL), and
a magnetic stir bar. The flask was capped with a glass stopper
and heated in an oil bath at 110 °C with stirring for 15 min.
An aliquot was taken with a syringe and subjected to GC
analysis. Yields were calculated versus aryl halides or dode-
cane as an internal standard. The Hammett plots are shown
in Figures 2 and 3.
4-Nitrobiphenyl.33 1H NMR (CDCl3, 500 MHz): δ 8.28 (d,
2, J ) 9.0 Hz), 7.72 (d, 2, J ) 9.0 Hz), 7.32 (d, 2, J ) 7.8 Hz),
7.52 (t, 2, J ) 7.3 Hz, meta C6H5), 7.46 (t, 1, J ) 6.5 Hz, para
C6H5).13C NMR (CDCl3, 125.70 MHz): δ 147.46, 146.87, 138.55,
129.04 (CH), 128.83 (para C6H5), 127.62 (CH), 127.24 (CH),
123.96 (CH). HRMS (EI): calcd for C12H9NO2 m/z 199.0633,
found m/z 199.0630.
2,4,6-Triisopropylbiphenyl.34 1H NMR (CDCl3, 500
MHz): δ 7.51 (t, 2, J ) 7.5 Hz, meta C6H5), 7.46 (t, 1, J ) 7.3
Hz, para C6H5), 7.33 (d, 2, J ) 8.5 Hz, ortho C6H5), 7.22 (s, 2,
i
meta C6H2 Pr3), 3.10 (septet, 1, J ) 7.0 Hz, para CHMe2), 2.77
(septet, 2, J ) 7.0 Hz, ortho CHMe2), 1.46 (d, 6, J ) 7.0 Hz,
para CHMe2), 1.23 (d, 12, J ) 7.0 Hz, ortho CHMe2). 13C NMR
i
(CDCl3, 125.70 MHz): δ 147.82, 146.51 (ortho C6H2 Pr3),
140.88, 137.11, 129.80 (CH), 127.89 (CH), 126.40 (para C6H5),
120.49 (CH), 34.30 (para CHMe2), 30.26 (ortho CHMe2), 24.23
(ortho-CHMe2), 24.12 (para CHMe2). HRMS (EI): calcd for
C21H28 m/z 280.2191, found m/z 280.2189.
2,4,6-Trimethylbiphenyl.35 1H NMR (CDCl3, 500 MHz):
δ 7.58 (t, 2, J ) 7.5 Hz, meta C6H5), 7.50 (t, 1, J ) 7.5 Hz,
para C6H5), 7.33 (d, 2, J ) 7.5 Hz, ortho C6H5), 7.14 (s, 2, meta
C6H2Me3), 2.52 (s, 3, para C6H2Me3), 2.21 (s, 6, ortho C6H2Me3).
13C NMR (CDCl3, 125.70 MHz): δ 141.07, 139.03, 136.45,
135.87 (ortho C6H2Me3), 129.24 (CH), 128.32 (CH), 128.02
(CH), 126.45 (para C6H5), 20.98 (para Me), 20.70 (ortho Me).
HRMS (EI): calcd for C15H16 m/z 196.1252, found m/z 196.1249.
2-Fluorobiphenyl.36 1H NMR (CDCl3, 500 MHz): δ 7.63
(d, 2, J ) 7.3 Hz), 7.52 (m, 3), 7.44 (t, 1, J ) 7.4 Hz), 7.37 (m,
1), 7.27 (t, 1, J ) 7.4 Hz), 7.22 (t, 1, J ) 8.3 Hz). 13C NMR
(CDCl3, 125.70 MHz): δ 159.74 (JCF ) 248 Hz, CF), 135.79
(ipso C6H5), 130.74 (JCF ) 3 Hz, CH), 129.01 (JCF ) 3 Hz, ortho
C6H5), 128.92 (JCF ) 8 Hz, CH), 128.40 (meta C6H5), 127.92
Acknowledgment. We thank the National Science
Council of Taiwan for financial support (Grant No. NSC
93-2113-M-110-016) of this work and Mr. Ting-Shen
Kuo at the Instrumentation Center of National Taiwan
Normal University for solving the X-ray structure of
[NP]PdCl(PCy3).
Supporting Information Available: Tables and figures
giving the X-ray crystallographic report and data in CIF format
for [NP]PdCl(PCy3). This material is available free of charge
via the Internet at http://pubs.acs.org.
(JCF ) 200 Hz, ipso C6H4F), 127.62 (para C6H5), 124.30 (JCF
)
4 Hz, CH), 116.05 (JCF ) 23 Hz, CH). 19F NMR (CDCl3, 188.15
(32) Mowery, M. E.; DeShong, P. J. Org. Chem. 1999, 64, 3266-
3270.
OM0492395
(33) Mori, Y.; Seki, M. J. Org. Chem. 2003, 68, 1571-1574.
(34) Hartmann, N.; Niemeyer, M. Synth. Commun. 2001, 31, 3839-
3846.
(37) Wolfe, J. P.; Singer, R. A.; Yang, B. H.; Buchwald, S. L. J. Am.
Chem. Soc. 1999, 121, 9550-9561.
(35) Anderson, J. C.; Namli, H.; Roberts, C. A. Tetrahedron 1997,
53, 15123-15134.
(38) Dupuis, C.; Adiey, K.; Charruault, L.; Michelet, V.; Savignac,
M. Tetrahedron Lett. 2001, 42, 6523-6526.
(36) Zhang, J.; DesMarteau, D. D. J. Fluorine Chem. 2001, 111,
253-257.
(39) Bei, X.; Turner, H. W.; Weinberg, W. H.; Guram, A. S.; Petersen,
J. L. J. Org. Chem. 1999, 64, 6797-6803.