Effect on orthometallation of NHC palladium complexes toward the catalytic activity studies in Suzuki coupling reaction

Article abstract of DOI:10.1039/c7dt03280c

Herein, we report an approach to improve catalytic activity for cross-coupling reactions. N-Heterocyclic carbene (NHC) palladium complexes bearing a nitrogen-based ligand without orthometallation complexes show remarkable activities in Suzuki coupling reaction than orthometallation. Aryl chlorides examples employed in air and ambient temperature in Suzuki coupling reaction to reach completion within few minutes.

Full text of DOI:10.1039/c7dt03280c

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Efficient extraction of sulfate from water using
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Effect on Orthometallation of NHC Palladium Complexes toward
the Catalytic Activity Studies in Suzuki Coupling Reaction
Ming-Tsz Chena* and Zing-Lun Kaoa
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
This work helps to understand how to improve catalytic activity important key is the “throw-away” ligand(s) should incorporate
for cross-coupling reaction. N-heterocyclic carbene (NHC) active metal centre to generate active Pd(0) species during the
palladium complexes bearing nitrogen-based ligand without catalytic process. Ideally, for the preparation and design, the
orthometallation complexes show remarkable activities in Suzuki properties of “throw-away” ligands should be inexpensive and
coupling reaction than orthometallation one. Aryl chlorides remove easily during the activation step.17
examples employed in air and ambient temperature to reach
completion within few minutes.
Ying and co-worker reported a library of N-Heterocyclic
carbene (NHC) palladacycle exhibited excellent activities toward
Suzuki-Miyaura cross-coupling reaction, especially containing with
oxygen atom donor group16, as well as Nolan et al. reported (NHC)
palladacycle complexes demonstrated very active abilities for
Suzuki coupling in the presence of IPA as solvent at room
temperature.14 Palladacycles have been investigated deeply and
well and showed thermal stable properties either palladacycles
containing with another donor adduct(s)41-42. Due to Ying’s NHC
palladium orthometallation catalysts already showed high activities,
moreover, based on cross-coupling reaction mechanism if we can
overcome this sluggish activation step by removing the
orthometallation motif, complexes should shorten the pre-
activation time.43 To prove this idea, hence we tried to design
without orthometallation NHC Palladium complexes as Figure 1
depicted. To clarify the above idea, we have studied the formation
of the amine complexes using NHC Palladium chloride bridge dimer
complexes with amine in shorter reaction time. From this study, we
have isolated and characterised NHC Palladium complexes bearing
N-donor group without orthometallation on Suzuki-Miyura cross-
coupling reaction studies.
In the past decades, palladium catalysts emerged as extremely
powerful tools for the construction of carbon-carbon as well as
carbon-heteroatom bonds in diverse areas of chemistry such as
bioactive, conductive and fluorescent compounds, which have been
broadly applied in pharmaceutical and materials sciences.1-6 The
beginning studies stressed on part through the rich variety of
organometallic nucleophiles that could be used for these reactions7-
12
and more recently interest has focused on the activation of more
challenging and varied electrophiles such as aryl chlorides or mild
conditions.13-17 This has not only resulted in increasing numbers of
studies gaining hands-on experiences with catalysts designed but
has also resulted in increasingly more insight and clear information
referred mechanistic studies have been explored by research
groups2, 4-5, 18
.
As familiarity and understanding have grown, so have the
development, implementation, and dissemination of curricular
strategies that use NHC ligands to investigate relevant cross-
coupling reactions in meaningful ways. The enhanced reactivity
found were credited to use different donor groups to cooperate Pd
metal centre. Interesting catalysts bearing both NHC as well as
different auxiliary ligands were developed, such as N-donor14, 17, 19-31
P-donor32-35 and other donors.15, 36-40 A crucial research area is to
figure out how to design effective catalyst from a stable Pd(II)
complex go into the active Pd(0) species in the transition state of
the catalytic cycle. Within this process, the Pd(II) complex must lose
some of the ligands attached to the metal centre. The most
N
N
N
N
,
Cl Pd
N
Cl Pd Cl
N
cat.
Remove orthometallation to
accelerate pre-activation step
This work
Figure 1. The idea to design active catalysts.
Preparation of complexes 1a and 1b was very straightforward
and was achieved by combining the corresponding [(NHC)PdCl2]2
dimers with 2 equiv. N, N-dimethylbenzylamine in CH2Cl2 at room
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Pd(1)−Cl(1) 2.2995(17), Pd(1)−Cl(2) 2.2965(18), Pd(1)−N(3) 2.194(5);
C(1)−Pd(1)−Cl(1) 87.86(18), C(1)−Pd(1)−N(3) 177.6(2),
Cl(2)−Pd(1)−N(3) 92.85(15).
temperature for 20 min reaction time. Synthetic details are
summarized in Scheme 1. ‡
N
N
N
Cl Pd Cl
N
N
N
Cl
2
2
2
Pd
R.T., 20 min
Cl
IPrPdCl2BnNMe2: 1a
1b
SIPrPdCl2BnNMe2:
Scheme 1. The synthesis of (NHC)PdCl2BnNMe2 complexes 1a-b
The target complexes were isolated in very good yields in
95% for 1a and 78% for 1b by evaporating the solvent.‡
Complexes 1a and 1b were not only fully characterised by
means of elemental analysis and 1H and 13C NMR spectroscopy
but also solid-state structures were determined by X-ray
diffraction.† Both crystal structures were grown from
dichloromethane and adopted a slightly distorted square-
planar geometry with the chloride ligands perpendicular to the
plane of NHC and N, N-dimethylbenzylamine trans to it. In the
Figure 3. Crystal structure of 1b with thermal ellipsoids drawn at
the 50% probability level. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (o): Pd(1)−C(1) 1.963(3),
Pd(1)−Cl(1) 2.2964(8), Pd(1)−Cl(2) 2.2953(8), Pd(1)−N(3) 2.2083(19);
C(1)−Pd(1)−Cl(1) 87.24(8), C(1)−Pd(1)−N(3) 177.8(12),
Cl(2)−Pd(1)−N(3) 92.80(7).
case of complexes 1a-b, these new complexes are air- and
moisture-stable and indefinitely can be stored in air. X-ray
structural images were depicted in Figures 2-3. As usual in
NHC-bearing complexes, the Pd-Ccarbene distance is in the range
of a single bond (1.957(6) Å for 1a and 1.963(3) for 1b), longer
than that of the corresponding parent dimers. The Pd-Cl bond
distances of complexes 1a and 1b fall between the values
found for the Pd-(μ-Cl) and Pd-Cl distances of the parent dimer
It was worth examining whether the observed structural
insights could lead to an improved activation and result in an
increase in a number of active Pd species in solution on test
substrates of Suzuki-Miyaura coupling reaction. A comparison of
the performance of eight NHC-Pd complexes comprising other five
very active catalysts, such as Cazin(2a)45, Navarro(4)17, Organ(5)19
,
[Pd(μ-Cl)Cl(IPr)]2(2a),
[Pd(μ-Cl)Cl(SIPr)]2(2b):
IPrPd-(μ-Cl)
Nolan(6)14 groups have reported in Suzuki-Miyaura reaction, in the
presence of 2-chloroanisole and phenylboronic acid at room
temperature was employed, and screen catalyst structures were
listed in Figure 4. All results were collected in Table 1.
2.4029(9); SIPrPd-(μ-Cl) 2.4029(9), Pd-Cl 2.2965(18), 2.2995(17)
for 1a and 2.2953(8), 2.2964(8) for 1b. Try to compare with the
same N-donor but exhibited orthmetallation complex
3 (Figure
4), and complex 1a showed symmetric phenyl splitting signals
in 6.95-7.50 in 1H NMR as well as lacked one quaternary
carbon signal in 13C NMR.44 Because complex 1a didn’t have
the orthometallated carbon and the trans effect of the carbon
atom resulted in shorter Pd-Ccarbene bond 1.957(6) Å and trans
to the nitrogen atom to elongate Pd-N bond 2.194(5) Å
compared to the Pd-Ccarbene bond 1.976 Å and Pd-N bond 2.142
N
N
N
N
N
Cl
Pd
Cl Pd Cl
N
Cl Pd Cl
N
N
Cl
2
1a
1b
Cazin, 2a
Å for complex
3. The coordinated behavior of complex 1b was
observed and similar to complex 1a
.
N
N
N
N
N
N
Cl
Pd
Cl
Pd
Cl Pd Cl
N
Cl
2
N
2b
Ying, 3
Navarro, 4
N
N
N
N
Cl
Pd
Cl Pd Cl
N
N
Cl
Organ,
5
6
Nolan,
Figure 4. High efficiency (NHC)PdCl2 complexes compared activities
Figure 2. Crystal structure of 1a with thermal ellipsoids drawn at
the 50% probability level. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (o): Pd(1)−C(1) 1.957(6),
in this study.
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Following this preliminary screening of conditions, when using Suzuki-Miyaura cross-coupling reactions have been carried out
K3PO4/EtOH complex 1a achieved 99% yields for 15 min (entry 1); using 1:1.2 stoichiometric ratio of aryl chlorides and phenylboronic
with saturated backbone complex 1b gave 80% yield for 60 min acid and 1.2 equiv. K3PO4 in without the use of anhydrous and air-
(entry 3). For the Cazin group used [Pd(μ-Cl)Cl(IPr)]2 2a45 showed free ethanol medium at room temperature loading 1mol% complex
good activities at room temperature in Suzuki reaction or [Pd(μ- 1a as pre-catalyst. The reactions between aryl chlorides and
Cl)Cl(SIPr)]2 2b have been examined to achieve completion yield phenylboronic acid were found to proceed smoothly and very
within 1h (entries 13-14). Complex 3 was used instead of 1a, but shorter time to obtain corresponding coupled products. All
didn’t work even the reaction time extended to 360 min, complex 4 reactions were carried out at room temperature and also in air
showed 95% yield for 45 min, IPr-PEPPSI complex 5 showed 80% in operation process. Under these conditions allowed the coupling of
60 min and complex 6 loaded 2 mol% catalyst dosage to reach 95% unactivated aryl chlorides (entries 3-6); heterocyclic ( entries 2, 8),
for 90 min (entries 15-18). Only complex 1a allowed for the and monosubstituted (entries 4-8 and 18); di-ortho-substituted
coupling to proceed in high yield in shorter reaction time at room (entries 10-13) and tri-ortho-substituted (entries 14-17), all reaction
temperature than other previously reported high active catalysts time fall into 5 to 60 min to afford more than 90% yield, only
and this result also proved without orthometallated lead to phenylboronic acid equipped with withdraw functional groups
shortening the pre-activated time.
needed elongated time of 113 min to achieve 90% yield (entries 16-
In spite of which of the pathways for the N-donor elimination 17), and 2-chloroaniline as start material owing to its coordination
is preferred, the observation in shortening of the Pd-Ccarbene ability to palladium centre led to more reaction time to reach good
distances reveals to correlate with an easier activation process, yield by 360 min in 88% yield. After these substrates were surveyed,
leading to
a
[(IPr)-Pd(0)] species.15 We tried to collect the complex 1a demonstrated very active abilities for Suzuki-Miyaura
differences and relationship between these structures. To cross-coupling reaction than other high efficiencies (NHC)PdCl2
determine if this feature allowed for a more facile activation step complexes shown in Figure 4. This result also is better than the
leading to a more active catalytic system, these complexes have Ying’s NHC palladacycle complex16 or Herrmann et. al has done by
tested in Suzuki-Miyaura cross-coupling reactions. In complex 1a, using 3 mol% NHC-Pd(0)-NHC catalyst. 46
the Pd-Ccarbene showed the shortest bond distance of 1.957Å
Table 2. Results of Suzuki-Miyaura coupling of aryl chlorides with
phenylboronic acida
compared with the other five complexes. All the other four
complexes bond lengths of the Pd-Ccarbene was 1.964 Å for 1b; 1.996
Å for 3; 1.969 Å for 4 and 1.968 Å for 5. These catalytic behaviors
consisted of the series of bond distances of Pd-Ccarbene
.
Time
(min)
Yield
Entry
R1-Cl
R2-B(OH)2
(%)b
Table 1. Optimum conditions of Suzuki-Miyaura coupling of aryl
chlorides with phenylboronic acida
1
2
3
4
10
20
5
99(96)
99(95)
93(91)
97(96)
Entry Cat. Solvent Base
Time (min)
Yield (%) b
1
2
3
4
5
6
7
8
9
10
11
12
13c
14c
15
16
17
18d
1a
1a
1b
1a
1a
1a
1a
1a
1a
1a
1a
1a
2a
2b
3
EtOH
EtOH
EtOH
THF
Tol
THF
IPA
DME
Tol
K3PO4
NaOtBu
K3PO4
KOtBu
KOtBu
K3PO4
NaOH
NaOH
K3PO4
NaOtBu
NaOtBu
K2CO3
K3PO4
K3PO4
K3PO4
NaOH
K3PO4
KOtBu
15
60
60
60
60
60
60
60
60
60
60
60
60
60
360
45
60
90
99
99
86
<1
<1
<1
<1
<1
23
6
9
5
6
7
10
15
10
99(96)
99(96)
99(96)
THF
DME
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
IPA
7
76
98
95
<1
95
80
95
8
9
30
30
20
99(95)
99(97)
93(92)
4
5
6
a Reaction conditions: 0.5 mmol 2-chloroanisole, 0.6 mmol phenylboronic
acid, 1.2 equiv. base, 1 mol% catalyst, and 1 mL solvent, 25 oC. b Determined
by GC-MS, average of 2 runs. c 0.5 mol% catalyst loading. d 2 mol% catalyst
loading.
10
11
12
20
28
98(95)
88(86)
With the initial optimum conditions studies, using K3PO4/EtOH
showed the best performance to give the high yield when using 2-
chloroanisole and phenylboronic acid as start materials (Table 1).
The coupling between the range of aryl chlorides and functionalized
phenylboronic acid was examined systematically (Table 2). ¶ All
13
70
90(87)
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6
R. H. Crabtree and M. P. Mingos, in C-C Bond Formation by
Cross-Coupling, eds. O. Navarro and S. P. Nolan, Elsevier Science
New York,, 2007.
N. Miyaura, K. Yamada and A. Suzuki, Tetrahedron Lett., 1979,
20, 3437-3440.
M. Kosugi, K. Sasazawa, Y. Shimizu and T. Migita, Chem. Lett.,
1977, 6, 301-302.
D. Milstein and J. K. Stille, J. Am. Chem. Soc., 1978, 100, 3636-
3638.
14
15
16
50
60
97(90)
94(93)
92(90)
7
8
9
113
10 H. A. Dieck and F. R. Heck, J. Organomet. Chem., 1975, 93, 259-
263.
11 K. Sonogashira, Y. Tohda and N. Hagihara, Tetrahedron Lett.,
1975, 16, 4467-4470.
12 E.-i. Negishi, in Aspects of Mechanism and Organometallic
Chemistry, ed. J. H. Brewster, Springer US, Boston, MA, 1978, pp.
285-317.
13 A. F. Littke and G. C. Fu, Angew. Chem. Int. Ed., 2002, 41, 4176-
4211.
17
18
113
360
90(85)
88(87)
a Reaction conditions: 0.5 mmol arylchloride, 0.6 mmol arylboronic acid, 1.2
equiv. K3PO4, 1 mol% 1a, and 1 mL EtOH, 25 oC. b Determined by GC-MS,
average of 2 runs; values in brackets referred for isolated yield after column
chromatography.
14 O. Navarro, R. A. Kelly, 3rd and S. P. Nolan, J Am Chem Soc, 2003,
125, 16194-16195.
In summary, a very mild and easy conditions catalytic system
for Suzuki-Miyaura cross-coupling reaction is described. Under
these conditions, sterically hindered unactivated aryl chlorides
couple with sterically hindered boronic acids led to di- and tri-ortho-
substituted biaryls in completion yields in very shorter reaction time
at room temperature in air. Moreover, for green chemistry claim,
no heating, and environmental friendliness solvent-ethanol are
used to make this system very attractive in view of its low cost.
Studies aimed at elucidating without orthometalled N-donor NHC
palladium complexes shorten pre-activation step time to enhance
the catalytic activities are presently being examined with this and
showed remarkable active results than related NHC palladacycles.
We are grateful to the Ministry of Science and Technology of
Taiwan for financial support (grant number MOST 106-2113-M-126-
001-MY2).
15 N. Marion, O. Navarro, J. Mei, E. D. Stevens, N. M. Scott and S. P.
Nolan, J. Am. Chem. Soc., 2006, 128, 4101-4111.
16 G.-R. Peh, E. A. B. Kantchev, J.-C. Er and J. Y. Ying, Chem. Eur. J.,
2010, 16, 4010-4017.
17 M. T. Chen, D. A. Vicic, M. L. Turner and O. Navarro,
Organometallics, 2011, 30, 5052-5056.
18 A. d. Meijere, S. Bräse and M. Oestreich, Metal-Catalyzed Cross-
Coupling Reactions and More, Wiley-VCH Verlag GmbH & Co.
KGaA, Boschstr. 12, 69469 Weinheim, Germany, 2014.
19 M. G. Organ, S. Çalimsiz, M. Sayah, K. H. Hoi and A. J. Lough,
Angew. Chem. Int. Ed., 2009, 48, 2383-2387.
20 M. T. Chen, D. A. Vicic, W. J. Chain, M. L. Turner and O. Navarro,
Organometallics, 2011, 30, 6770-6773.
21 L. Wu, E. Drinkel, F. Gaggia, S. Capolicchio, A. Linden, L. Falivene,
L. Cavallo and R. Dorta, Chem. Eur. J., 2011, 17, 12886-12890.
22 A. Chartoire, M. Lesieur, L. Falivene, A. M. Z. Slawin, L. Cavallo, C.
S. J. Cazin and S. P. Nolan, Chem. E. J., 2012, 18, 4517-4521.
23 W.-X. Chen and L.-X. Shao, J. Org. Chem., 2012, 77, 9236-9239.
24 L. Benhamou, C. Besnard and E. P. Kündig, Organometallics,
2013, 33, 260-266.
25 R. S. Sprick, M. Hoyos, M.-T. Chen, M. L. Turner and O. Navarro,
J. Polym. Sci., Part A: Polym. Chem., 2013, 51, 4904-4911.
26 Z.-Y. Wang, Q.-N. Ma, R.-H. Li and L.-X. Shao, Org. Biomol. Chem.,
2013, 11, 7899-7906.
Notes and references
‡ Complexes 1a-b experimental and spectral data are listed in
ESI.
†Crystallographic data 1a
are summarized in the supporting information.
For reactions were carried out under aerobic conditions, all
-b (CCDC numbers 1553847-1553848)
¶
27 P. Huang, Y.-X. Wang, H.-F. Yu and J.-M. Lu, Organometallics,
2014, 33, 1587-1593.
solids were weighed in air. The solvents were used without any
purification and all liquids were injected in vials opened to air.
28 M. Pompeo, J. L. Farmer, R. D. J. Froese and M. G. Organ, Angew.
Chem. Int. Ed., 2014, 53, 3223-3226.
29 F. Rajabi and W. R. Thiel, Adv. Synth. Catal., 2014, 356, 1873-
1877.
1
E.-i. Negishi and A. de Meijere, Handbook of Organopalladium
Chemistry for Organic Synthesis, John Wiley & Sons, Inc., New
York., 2002.
2
J. Tsuji, Palladium Reagents and Catalysts New Perspectives for
the 21st Century, John Wiley & Sons Ltd, The Atrium, Southern
Gate, Chichester, West Sussex PO19 8SQ, England, 2004.
J. Tsuji, ed., Palladium in Organic Synthesis, Springer
International Publishing AG, 2005.
A. d. Meijere and F. Diederich, Metal-Catalyzed Cross-Coupling
Reactions 2nd Edition, WILEY-VCH Verlag GmbH & Co. KGaA,
Weinheim, 2014.
30 X.-X. He, Y. Li, B.-B. Ma, Z. Ke and F.-S. Liu, Organometallics,
2016, 35, 2655-2663.
31 X.-B. Lan, F.-M. Chen, B.-B. Ma, D.-S. Shen and F.-S. Liu,
Organometallics, 2016, 35, 3852-3860.
32 K.-T. Chan, Y.-H. Tsai, W.-S. Lin, J.-R. Wu, S.-J. Chen, F.-X. Liao, C.-
H. Hu and H. M. Lee, Organometallics, 2009, 29, 463-472.
33 O. Diebolt, V. c. Jurčík, R. Correa da Costa, P. Braunstein, L.
Cavallo, S. P. Nolan, A. M. Z. Slawin and C. S. J. Cazin,
Organometallics, 2010, 29, 1443-1450.
3
4
5
Á. Molnár, Palladium-Catalyzed Coupling Reactions, Wiley-VCH
Verlag GmbH & Co. KGaA, Boschstr. 12, 69469 Weinheim,
Germany, 2013.
34 P. V. Kumar, W.-S. Lin, J.-S. Shen, D. Nandi and H. M. Lee,
Organometallics, 2011, 30, 5160-5169.
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35 T. E. Schmid, D. C. Jones, O. Songis, O. Diebolt, M. R. L. Furst, A.
M. Z. Slawin and C. S. J. Cazin, Dalton Trans., 2013, 42, 7345-
7353.
36 M. S. Viciu, R. F. Germaneau, O. Navarro-Fernandez, E. D.
Stevens and S. P. Nolan, Organometallics, 2002, 21, 5470-5472.
37 S. Meiries, K. Speck, D. B. Cordes, A. M. Z. Slawin and S. P. Nolan,
Organometallics, 2012, 32, 330-339.
38 G. Bastug and S. P. Nolan, Organometallics, 2014, 33, 1253-1258.
39 M. Micksch, M. Tenne and T. Strassner, Organometallics, 2014,
33, 3966-3976.
40 J. Yang, P. Li, Y. Zhang and L. Wang, Dalton Trans., 2014, 43,
14114-14122.
41 M. Beller, H. Fischer, W. A. Herrmann, K. Öfele and C. Brossmer,
Angew. Chem. Int. Ed., 1995, 34, 1848-1849.
42 R. B. Bedford, Chem. Commun., 2003, 1787-1796.
43 M. T. Chen, K. M. Wu and C. T. Chen, Eur J Inorg Chem, 2012,
720-726.
44 E. A. B. Kantchev and J. Y. Ying, Organometallics, 2009, 28, 289-
299.
45 O. Diebolt, P. Braunstein, S. P. Nolan and C. S. J. Cazin, Chem.
Commun., 2008, 3190-3192.
46 C. W. K. Gstöttmayr, V. P. W. Böhm, E. Herdtweck, M. Grosche
and W. A. Herrmann, Angew. Chem. Int. Ed., 2002, 41, 1363-
1365.
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