A practical synthesis of unsymmetrical triarylphosphines by heterogeneous palladium(0)-catalyzed cross-coupling of aryl iodides with diphenylphosphine

Article abstract of DOI:10.1016/j.jorganchem.2018.04.018

The heterogeneous cross-coupling reaction of aryl iodides with diphenylphosphine was achieved in DMAc at 130 °C in the presence of 1.0 mol% of MCM-41-supported tridentate nitrogen palladium(0) complex [MCM-41-3N-Pd(0)] with KOAc as base, yielding a variety of unsymmetrical triarylphosphines in good to excellent yields. The turnover frequency (TOF) of the catalyst can reach 30.67 h^?1. This new heterogeneous palladium(0) catalyst could easily be prepared by a simple procedure from commercially readily available reagents, and exhibited the same catalytic activity as homogeneous Pd(OAc)₂ or Pd(PPh₃)₄, and could be recovered by filtration of the reaction solution and recycled at least seven times without significant loss of catalytic activity.

Full text of DOI:10.1016/j.jorganchem.2018.04.018

Journal of Organometallic Chemistry 866 (2018) 50e58
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Note
A practical synthesis of unsymmetrical triarylphosphines by
heterogeneous palladium(0)-catalyzed cross-coupling of aryl iodides
with diphenylphosphine
,
*
Zhaotao Xu a, Pingping Wang b, Qiurong Chen a, Mingzhong Cai a
a Key Laboratory of Functional Small Organic Molecule, Ministry of Education and College of Chemistry & Chemical Engineering, Jiangxi Normal University,
Nanchang, 330022, PR China
b Department of Chemistry, Jiujiang University, Jiujiang, 332000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
The heterogeneous cross-coupling reaction of aryl iodides with diphenylphosphine was achieved in
DMAc at 130 ꢀC in the presence of 1.0 mol% of MCM-41-supported tridentate nitrogen palladium(0)
complex [MCM-41-3N-Pd(0)] with KOAc as base, yielding a variety of unsymmetrical triarylphosphines
in good to excellent yields. The turnover frequency (TOF) of the catalyst can reach 30.67 hꢁ1. This new
heterogeneous palladium(0) catalyst could easily be prepared by a simple procedure from commercially
readily available reagents, and exhibited the same catalytic activity as homogeneous Pd(OAc)2 or
Pd(PPh3)4, and could be recovered by filtration of the reaction solution and recycled at least seven times
without significant loss of catalytic activity.
Received 29 January 2018
Received in revised form
4 April 2018
Accepted 11 April 2018
Available online 12 April 2018
Keywords:
Palladium
Triarylphosphine
Cross-coupling
MCM-41
© 2018 Elsevier B.V. All rights reserved.
Heterogeneous catalysis
1. Introduction
copper- [25e28], and nickel [29e34]-catalyzed phosphinations of
aryl iodides/bromides or aryl triflates for the synthesis of tertiary
Tertiary arylphosphines have widely been applied in many
organic transformations catalyzed by transition metals as one of
the most useful ligands and are ubiquitous in organometallic
chemistry [1e7]. Besides, triarylphosphines can also be used as
catalysts [8e10] and fundamental building blocks [11,12] in organic
synthesis. The traditional routes to arylphosphines involve re-
actions of phosphine halides with arylmagnesium or aryllithium
reagents, and are therefore intolerant to a wide range of functional
groups [1e3]. Among various methods for the preparation of
arylphosphine ligands, direct carbon-phosphorous (CeP) bond
formation via transition metal-catalyzed cross-coupling between
unprotected secondary phosphines and aryl halides/triflates is one
of the most valuable and highly efficient routes due to the tolerance
of a wide variety of functional groups. Since Stelzer and coworkers
first reported the palladium-catalyzed cross-couplings between
aryl iodides/bromides and diarylphosphines [13,14], considerable
effort has been devoted to the development of palladium- [15e24],
phosphines. Recently, catalytic reduction of tertiary phosphine
oxides has also proven to be an alternative method for the synthesis
of tertiary phosphines [35e38].
Despite significant progress made in homogeneous Pd-, Cu- and
Ni-catalyzed synthesis of triarylphosphines, the use of expensive
palladium catalysts as well as difficult recovery and non-
recyclability of the metal catalysts make these methods of limited
synthetic utility from environmental and economic points of view
[39]. What's more, homogeneous catalysis might result in heavy
metal contamination of the desired isolated product due to the easy
formation of complexes of palladium, nickel and copper with tri-
arylphosphines. Recycling of homogeneous metal catalysts is a task
of great economic and environmental importance in the chemical
and pharmaceutical industries, especially when expensive and/or
toxic heavy metal complexes are utilized [40]. The heterogenization
of the existing homogeneous metal catalysts appears to be a logical
solution to these problems [41,42]. In recent years, heterogeneous
palladium catalysts have been successfully applied in carbon-
carbon and carbon-heteroatom bond formation reactions [43,44].
However, to the best of our knowledge, no examples of heteroge-
neous palladium-catalyzed CeP bond construction via direct
* Corresponding author.
E-mail addresses: caimzhong@163.com, mzcai@jxnu.edu.cn (M. Cai).
https://doi.org/10.1016/j.jorganchem.2018.04.018
0022-328X/© 2018 Elsevier B.V. All rights reserved.

Z. Xu et al. / Journal of Organometallic Chemistry 866 (2018) 50e58
51
coupling of secondary phosphines with aryl halides/triflates have
been described until now.
In a small Schlenk tube,1.70 g of the above-functionalized MCM-
41 (MCM-41-3 N) was mixed with 0.177 g (1.0 mmol) of PdCl2 in
40 mL of dry acetone. The mixture was refluxed for 72 h under an
argon atmosphere. The solid product was filtered, washed with
distilled water (2 ꢂ 10 mL) and ethanol (2 ꢂ 10 mL), and dried un-
der vacuum. The yellow solid was then mixed with hydrazine hy-
drate (1.5 mL) in ethanol (20 mL) at 30 ꢀC for 5 h. The resulting
product was filtered, washed with distilled water (3 ꢂ 10 mL) and
acetone (2 ꢂ 10 mL) and dried under vacuum at 60 ꢀC for 5 h to
afford 1.82 g of a gray palladium(0) complex [MCM-41-3N-Pd(0)].
The nitrogen and palladium contents were found to be
2.36 mmol/g and 0.49 mmol/g, respectively.
Mesoporous MCM-41 materials have recently been shown to be
powerful supports for immobilization of homogeneous catalysts
[45e47]. So far, some functionalized MCM-41-immobilized palla-
dium [48e52], rhodium [53], molybdenum [54], gold [55,56], and
copper [57,58] complexes have been successfully used as highly
efficient and recyclable catalysts in organic reactions. In continuing
our efforts to develop greener synthetic pathways for organic
transformations [50e52,57,58], herein we report the first synthesis
of an MCM-41-supported tridentate nitrogen palladium(0) com-
plex [MCM-41-3N-Pd(0)] and its successful application to cross-
coupling of aryl iodides with diphenylphosphine leading to a va-
riety of unsymmetrical triaylphosphines in good to excellent yields
(Scheme 1).
2.3. General procedure for CeP coupling reaction of various aryl
iodides with diphenylphosphine
MCM-41-3N-Pd(0) (21 mg, 0.01 mmol), KOAc (1.5 mmol) and
aryl iodide 1 (1.0 mmol) (if solid) were placed in an oven-dried
20 mL Schlenk tube, the reaction vessel was evacuated and filled
with argon for three times. Then aryl iodide 1 (1.0 mmol) (if liquid),
diphenylphosphine (1.2 mmol) and DMAc (1 mL) were added with
a syringe under a counter flow of argon. The reaction mixture was
stirred at 130 ꢀC for 3 h. After completion of the reaction, the
mixture was cooled to room temperature and diluted with CH2Cl2
(20 mL) and filtered. The MCM-41-3N-Pd(0) catalyst was washed
with distilled water (2 ꢂ 5 mL) and ethanol (2 ꢂ 5 mL), and reused
in the next run. The filtrate was concentrated in vacuo and the
residue was purified by flash column chromatography on silica gel
to provide the product 2.
2. Experimental
2.1. General remarks
All chemicals were reagent grade and used as purchased. The
mesoporous material MCM-41 was prepared according to a litera-
ture procedure [45]. The products were purified by flash chroma-
tography on silica gel. Mixture of CH2Cl2 and hexane was generally
used as eluent. All coupling products were characterized by com-
parison of their spectra and physical data with authentic samples.
1H NMR spectra were recoded on a Bruker Avance 400 MHz spec-
trometer with TMS as an internal standard in CDCl3 as solvent. 13
C
NMR spectra (100 MHz) were recorded on a Bruker Avance
400 MHz spectrometer in CDCl3 as solvent. 31P NMR spectra
(121 MHz) were recorded on a Bruker Avance 400 MHz spectrom-
eter in CDCl3 as solvent. Palladium content was determined with
inductively coupled plasma atom emission Atomscan16 (ICP-AES,
TJA Corporation). X-ray powder diffraction patterns were obtained
on Damx-rA (Rigaku). Nitrogen adsorption/desorption isotherms
were obtained using a Bel Japan Inc. Belsorp-HP at 77 K. Prior to gas
adsorption measurements materials were degassed for 6 h at 423 K.
TEM images were recorded in a transmission electron microscope
operated at an accelerated voltage of 200 kV. X-ray photoelectron
spectra were recorded on XSAM 800 (Kratos).
2.3.1. Triphenylphosphine, 2a [26]
White solid, m.p.: 79e80 ꢀC. 1H NMR (400 MHz, CDCl3):
d
¼ 7.44e7.23 (m, 15H); 13C NMR (100 MHz, CDCl3):
¼ 137.3, 137.2,
d
133.9, 133.7, 128.8, 128.6, 128.5; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ5.45 (s).
2.3.2. Diphenyl(4-methylphenyl)phosphine, 2b [26]
White solid, m.p.: 68e69 ꢀC. 1H NMR (400 MHz, CDCl3):
d
d
¼ 7.37e7.14 (m, 14H), 2.34 (s, 3H); 13C NMR (100 MHz, CDCl3):
¼ 138.9, 137.5, 137.4, 134.1, 133.9, 133.7, 133.6, 129.5, 129.4, 128.7,
128.5, 128.4, 21.4; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ6.30 (s).
2.2. Preparation of MCM-41-3N-Pd(0) complex
2.3.3. Diphenyl(4-methoxyphenyl)phosphine, 2c [59]
A
solution of 1.54 g of 3-(2-aminoethylamino)propyl-
White solid, m.p.: 67e68 ꢀC. 1H NMR (400 MHz, CDCl3):
trimethoxysilane in 18 mL of dry CHCl3 was added to a suspension
of 2.2 g of the MCM-41 in 180 mL of dry toluene under Ar. The
mixture was stirred at 100 ꢀC for 24 h. Then the solid was filtered
and washed by CHCl3 (2 ꢂ 20 mL), and dried in vacuum at 160 ꢀC for
5 h. The dried white solid (1.725 g) was then reacted with pyridine-
2-carboxaldehyde (0.251 g, 2.34 mmol) in 10 mL of dry ethanol at
80 ꢀC for 24 h. The solid product was filtered, washed with ethanol
(3 ꢂ 20 mL) and diethyl ether (20 mL), and dried in vacuum at
120 ꢀC for 5 h to obtain 1.813 g of hybrid material MCM-41-3 N. The
nitrogen content was found to be 2.62 mmol/g by elemental
analysis.
d
¼ 7.25e7.16 (m, 12H), 6.82 (d, J ¼ 8.0 Hz, 2H), 3.73 (s, 3H); 13C NMR
(100 MHz, CDCl3):
d
¼ 160.4, 137.8, 137.7, 137.6, 135.8, 135.6, 133.6,
133.4, 128.6, 128.5, 128.4, 114.3, 114.2, 55.2; 31P NMR (121 MHz,
CDCl3):
¼ ꢁ7.10 (s).
d
2.3.4. Diphenyl(3-methylphenyl)phosphine, 2d [60]
White solid, m.p.: 50e51 ꢀC. 1H NMR (400 MHz, CDCl3):
d
d
¼ 7.42e7.06 (m, 14H), 2.30 (s, 3H); 13C NMR (100 MHz, CDCl3):
¼ 138.1, 137.1, 134.6, 134.4, 133.9, 133.7, 132.1, 130.9, 130.7, 129.6,
128.7, 128.5, 128.4, 21.5; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ5.23 (s).
Scheme 1. Heterogeneous Pd(0)-catalyzed CeP coupling of aryl iodides with Ph2PH.

52
Z. Xu et al. / Journal of Organometallic Chemistry 866 (2018) 50e58
2.3.5. Diphenyl(3,5-dimethylphenyl)phosphine, 2e [13]
Colorless oil. 1H NMR (400 MHz, CDCl3):
¼ 7.25e7.12 (m, 10H),
6.89e6.83 (m, 3H), 2.16 (s, 6H); 13C NMR (100 MHz, CDCl3):
2.3.15. Methyl 4-(diphenylphosphino)benzoate, 2o [26]
d
White solid, m.p.: 103e104 ꢀC. 1H NMR (400 MHz, CDCl3):
d
¼ 7.97 (d, J ¼ 7.2 Hz, 2H), 7.41e7.28 (m, 12H), 3.91 (s, 3H); 13C NMR
d
¼ 138.1, 138.0, 137.3, 137.2, 135.1, 133.9, 133.7, 131.7, 131.5, 130.8,
(100 MHz, CDCl3):
d
¼ 166.9, 144.1, 144.0, 136.2, 136.1, 134.1, 133.9,
128.7, 128.5, 128.4, 21.4; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ5.28 (s).
133.3, 133.1, 130.0, 129.4, 129.3, 129.2, 128.8, 128.7, 52.2; 31P NMR
(121 MHz, CDCl3):
¼ ꢁ5.05 (s).
d
2.3.6. Diphenyl(4-aminophenyl)phosphine, 2f [13]
White solid, m.p.: 37e38 ꢀC. 1H NMR (400 MHz, CDCl3):
¼ 7.23e7.12 (m, 10H), 7.06 (t, J ¼ 7.6 Hz, 2H), 6.54 (d, J ¼ 7.6 Hz,
2.3.16. Ethyl 4-(diphenylphosphino)benzoate, 2p [64]
White solid, m.p.: 83e84 ꢀC. 1H NMR (400 MHz, CDCl3):
d
d
¼ 7.98
2H), 3.43 (br, 2H); 13C NMR (100 MHz, CDCl3):
d
¼ 147.2, 138.3,
(d, J ¼ 8.4 Hz, 2H), 7.42e7.24 (m,12H), 4.36 (q, J ¼ 7.2 Hz, 2H),1.37 (t,
135.8, 135.6, 133.5, 133.3, 128.4, 128.3, 124.8, 115.3, 115.2; 31P NMR
(121 MHz, CDCl3):
¼ ꢁ6.61 (s).
J ¼ 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3):
d
¼ 166.4, 143.9, 143.8,
d
136.3, 136.2, 134.1, 133.9, 133.3, 133.1, 130.4, 129.3, 129.2, 129.1,
128.7, 128.6, 61.0, 14.3; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ5.07 (s).
2.3.7. 4-(Diphenylphosphino)biphenyl, 2g [61]
White solid, m.p.: 83e84 ꢀC. 1H NMR (400 MHz, CDCl3):
d
¼ 7.58
2.3.17. Diphenyl(2-chlorophenyl)phosphine, 2q [66]
(t, J ¼ 8.0 Hz, 4H), 7.45e7.32 (m, 15H); 13C NMR (100 MHz, CDCl3):
White solid, m.p.: 103e104 ꢀC. 1H NMR (400 MHz, CDCl3):
¼ 7.34e7.15 (m, 12H), 7.06 (t, J ¼ 7.4 Hz, 1H), 6.69e6.65 (m, 1H);
d
¼ 141.5, 140.6, 137.3, 137.2, 136.2, 136.1, 134.3, 134.1, 133.9, 133.7,
d
128.8, 128.6, 128.5, 127.5, 127.2, 127.1; 31P NMR (121 MHz, CDCl3):
¼ ꢁ5.99 (s).
13C NMR (100 MHz, CDCl3):
d
¼ 139.3, 139.1, 137.0, 136.9, 135.7,
d
135.6, 134.1, 133.9, 130.0, 129.6, 129.1, 128.7, 128.6, 126.8; 31P NMR
(121 MHz, CDCl3):
¼ ꢁ10.87 (s).
d
2.3.8. Diphenyl(4-fluorophenyl)phosphine, 2h [62]
White solid, m.p.: 53e54 ꢀC. 1H NMR (400 MHz, CDCl3):
2.3.18. Diphenyl(2-methylphenyl)phosphine, 2r [26]
d
¼ 7.35e7.24 (m, 12H), 7.03 (t, J ¼ 8.6 Hz, 2H); 13C NMR (100 MHz,
White solid, m.p.: 65e66 ꢀC. 1H NMR (400 MHz, CDCl3):
CDCl3):
d
¼ 164.6,162.2,136.0,135.9,133.7,133.5,128.8,128.6,128.5,
d
¼ 7.35e7.21 (m, 12H), 7.15e7.04 (m, 1H), 6.79e6.73 (m, 1H), 2.39
(s, 3H); 13C NMR (100 MHz, CDCl3):
¼ 142.4, 142.1, 139.0, 136.4,
136.3, 130.2, 130.1, 128.8, 128.7, 128.6, 126.1, 21.3; 31P NMR
(121 MHz, CDCl3):
¼ ꢁ13.27 (s).
115.9, 115.8, 115.7, 115.6; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ6.57 (d).
d
2.3.9. Diphenyl(4-chlorophenyl)phosphine, 2i [59]
d
White solid, m.p.: 44e45 ꢀC. 1H NMR (400 MHz, CDCl3):
¼ 7.31e7.20 (m, 12H), 7.14 (t, J ¼ 7.4 Hz, 2H); 13C NMR (100 MHz,
d
2.3.19. Diphenyl(2-methoxyphenyl)phosphine, 2s [26]
CDCl3):
d
¼ 136.7, 136.6, 136.0, 135.9, 135.1, 134.9, 133.8, 133.6, 129.0,
White solid, m.p.: 122e123 ꢀC. 1H NMR (400 MHz, CDCl3):
128.8, 128.7, 128.6; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ6.50 (s).
d
¼ 7.45e7.27 (m, 11H), 6.91e6.85 (m, 2H), 6.73e6.68 (m, 1H), 3.75
(s, 3H); 13C NMR (100 MHz, CDCl3):
¼ 161.3, 161.1, 136.7, 136.6,
134.0, 133.8, 133.7, 130.4, 128.6, 128.4, 128.3, 125.6, 125.5, 121.1,
110.3, 55.6; 31P NMR (121 MHz, CDCl3):
¼ ꢁ16.61 (s).
d
2.3.10. Diphenyl(4-bomophenyl)phosphine, 2j [59]
White solid, m.p.: 78e79 ꢀC. 1H NMR (400 MHz, CDCl3):
d
¼ 7.45
d
(d, J ¼ 7.6 Hz, 2H), 7.35e7.24 (m, 10H), 7.15 (t, J ¼ 7.6 Hz, 2H); 13C
NMR (100 MHz, CDCl3):
d
¼ 136.7, 136.6, 135.4, 135.2, 133.9, 133.7,
2.3.20. 2-(Diphenylphosphino)biphenyl, 2t [67]
131.8, 131.7, 129.1, 128.7, 128.6, 123.5; 31P NMR (121 MHz, CDCl3):
¼ ꢁ6.44 (s).
White solid, m.p.: 60e61 ꢀC. 1H NMR (400 MHz, CDCl3):
d
d
¼ 7.33e7.09 (m, 18H), 7.00e6.96 (m, 1H); 13C NMR (100 MHz,
CDCl3):
d
¼ 148.5, 148.2, 141.8, 141.7, 137.8, 137.7, 136.0, 135.9, 134.1,
2.3.11. Diphenyl(4-cyanophenyl)phosphine, 2k [63]
134.0, 133.8, 130.2, 130.1, 129.8, 129.7, 128.7, 128.5, 128.4, 128.3,
127.6, 127.4, 127.2; 31P NMR (121 MHz, CDCl3):
¼ ꢁ13.33 (s).
White solid, M.p. 86e87 ꢀC. 1H NMR (400 MHz, CDCl3)
d
¼ 7.55
d
(dd, J ¼ 8.4, 1.6 Hz, 2H), 7.38e7.29 (m, 12H). 13C NMR (100 MHz,
CDCl3)
d
¼ 145.2, 145.1, 135.5, 135.4, 134.2, 134.0, 133.6, 133.5, 131.8,
2.3.21. Methyl 2-(diphenylphosphino)benzoate, 2u [59]
White solid, m.p.: 97e98 ꢀC. 1H NMR (400 MHz, CDCl3):
129.6, 129.0, 128.9, 118.8, 111.9.31P NMR (121 MHz, CDCl3)
(s).
d
¼ ꢁ4.46
d
¼ 8.05
(d, J ¼ 2.8 Hz, 1H), 7.38e7.23 (m, 12H), 6.94 (m, 1H), 3.73 (s, 3H); 13
C
NMR (100 MHz, CDCl3):
d
¼ 167.3, 140.6, 140.4, 137.9, 137.8, 134.3,
2.3.12. Diphenyl(4-acetylphenyl)phosphine, 2l [26]
134.0, 133.8, 132.0, 130.7, 128.7, 128.6, 128.5, 128.3, 52.1; 31P NMR
(121 MHz, CDCl3):
¼ ꢁ4.26 (s).
White solid, m.p.: 121e122 ꢀC. 1H NMR (400 MHz, CDCl3):
¼ 7.80 (d, J ¼ 7.2 Hz, 2H), 7.35e7.15 (m, 12H), 2.50 (s, 3H); 13C NMR
d
d
(100 MHz, CDCl3):
d
¼ 197.8, 144.5, 144.4, 136.9, 136.2, 136.1, 134.1,
2.3.22. 1-(Diphenylphosphino)naphthalene, 2v [26]
133.9, 133.5, 133.3, 129.2, 128.8, 128.7, 128.1, 128.0, 26.6; 31P NMR
(121 MHz, CDCl3):
¼ ꢁ5.07 (s).
White solid, m.p.: 122e123 ꢀC. 1H NMR (400 MHz, CDCl3):
d
d
¼ 7.84 (t, J ¼ 8.8 Hz, 2H), 7.49e7.23 (m, 15H); 13C NMR (100 MHz,
CDCl3):
d
¼ 136.4, 136.3, 135.4, 135.2, 134.3, 134.1, 133.5, 133.4, 132.1,
2.3.13. Diphenyl(3-trifluoromethylphenyl)phosphine, 2m [64]
Colorless oil. 1H NMR (400 MHz, CDCl3):
¼ 7.60e7.56 (m, 2H),
7.44e7.41 (m, 2H), 7.37e7.28 (m, 10H); 13C NMR (100 MHz, CDCl3):
129.5, 128.9, 128.8, 128.7, 128.6, 126.3, 126.0, 125.6; 31P NMR
(121 MHz, CDCl3):
¼ ꢁ14.13 (s).
d
d
d
¼ 139.3, 139.2, 136.8, 136.7, 136.1, 136.0, 133.9, 133.8, 131.0, 130.9,
2.3.23. 2-(Diphenylphosphino)pyridine, 2w [68]
130.7, 130.6, 130.3, 130.1, 129.3, 128.9, 128.8, 125.5, 125.4, 122.7; 31
NMR (121 MHz, CDCl3):
¼ ꢁ5.30 (s).
P
White solid, m.p.: 82e83 ꢀC. 1H NMR (400 MHz, CDCl3):
d
¼ 8.72
d
(d, J ¼ 3.6 Hz, 1H), 7.57 (t, J ¼ 7.6 Hz, 1H), 7.40e7.25 (m, 10H), 7.18 (t,
J ¼ 5.8 Hz, 1H), 7.08 (d, J ¼ 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3):
2.3.14. Diphenyl(4-nitrophenyl)phosphine, 2n [65]
d
¼ 164.0, 150.4, 150.3, 136.2, 136.1, 135.8, 134.3, 134.1, 129.1, 128.7,
Yellow solid, M.p. 134e135 ꢀC.1H NMR (400 MHz, CDCl3)
d
¼ 8.14
128.6, 127.9, 127.8, 122.2; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ4.06 (s).
(d, J ¼ 7.6 Hz, 2H), 7.42e7.27 (m, 12H). 13C NMR (100 MHz, CDCl3)
d
¼ 147.8, 135.3, 135.2, 134.2, 134.0, 133.8, 133.6, 129.6, 129.0, 128.9,
2.3.24. 2-(Diphenylphosphino)thiophene, 2x [26]
123.2, 123.1.31P NMR (121 MHz, CDCl3)
d
¼ ꢁ4.48 (s).
White solid, m.p.: 44e45 ꢀC. 1H NMR (400 MHz, CDCl3):
d
¼ 7.58

Z. Xu et al. / Journal of Organometallic Chemistry 866 (2018) 50e58
53
(d, J ¼ 3.2 Hz, 1H), 7.48e7.06 (m, 12H); 13C NMR (100 MHz, CDCl3):
d
¼ 138.0, 137.9, 136.5, 136.3, 133.2, 133.0, 132.1, 128.9, 128.6, 128.5,
128.4, 128.1, 128.0; 31P NMR (121 MHz, CDCl3):
d
¼ ꢁ19.99 (s).
3. Results and discussion
3.1. Synthesis and characterization of MCM-41-3N-Pd(0) complex
Although the phosphine ligands can stabilize palladium and
affect its catalytic activity, undoubtedly, the simplest and cheapest
palladium catalysts are of course phosphine-free systems. A novel
MCM-41-supported tridentate nitrogen palladium(0) complex
[MCM-41-3N-Pd(0)] was easily prepared according to the proced-
ure as shown in Scheme 2. First, the mesoporous MCM-41 [45] was
condensed with 3-(2- aminoethylamino)propyltrimethoxysilane in
toluene under reflux for 24 h to afford the bidentate nitrogen-
functionalized MCM-41 [MCM-41-2 N]. The latter was reacted
with pyridine-2-carboxaldehyde in dry ethanol at reflux for 24 h to
give the tridentate nitrogen-functionalized MCM-41 [MCM-41-
3 N]. The MCM-41-3 N was then treated with PdCl2 in acetone at
reflux for 72 h, followed by reduction with hydrazine hydrate in
ethanol at 30 ꢀC for 5 h to generate the MCM-41-supported tri-
dentate nitrogen palladium(0) complex [MCM-41-3N-Pd(0)] as a
gray powder.
Fig. 1. Small angle XRD patterns of MCM-41 (1) and MCM-41-3N-Pd(0) (2).
X-ray powder diffraction (XRD) patterns of the parent MCM-41
and the modified material MCM-41-3N-Pd(0) are displayed in Fig.1.
Small angle X-ray diffraction of MCM-41 gave the peaks corre-
sponding to hexagonally ordered mesoporous phases. For the
MCM-41-3N-Pd(0) complex, the (100) reflection of the parent
MCM-41 with decreased intensity was remained after grafting
palladium complex, while the (110) and (200) reflections became
weak and diffuse, which may be mainly due to contrast matching
between the silicate framework and organic moieties which are
located inside the channels of MCM-41. These results indicate that
the mesoporous structure of the parent MCM-41 remains intact
through the grafting procedure and the forma-tion of the palladium
complex has taken place preferentially inside the pore system of
MCM-41.
The N2 adsorption-desorption isotherms and pore size distri-
butions for the parent MCM-41 and the MCM-41-3N-Pd(0) com-
plex are illustrated in Fig. 2 and Fig. 3, respectively. The isotherms in
Fig. 2 have remarkable changes before and after grafting the
palladium complex as expected because the organic moieties
entered the channels, but both samples showed type IV isotherms,
Fig. 2. N2 adsorption/desorption isotherms of MCM-41 and MCM-41-3N-Pd(0).
Scheme 2. Preparation of MCM-41-3N-Pd(0) complex.

54
Z. Xu et al. / Journal of Organometallic Chemistry 866 (2018) 50e58
41. The wide angle XRD pattern of MCM-41-3N-Pd(0) complex is
presented in Fig. 5. The MCM-41-3N-Pd(0) exhibited characteristic
peaks of palladium(0) nanoparticles with diffraction peaks at 2q of
ca. 39.0ꢀ, 45.3ꢀ, and 66.1ꢀ where these peaks correspond to (111),
(200), and (220) reflections, respectively [69].
Elemental analyses and X-ray photoelectron spectroscopy (XPS)
were also used to characterize the MCM-41-supported tridentate
nitrogen palladium(0) complex. The N: Pd mole ratio of the MCM-
41-3N-Pd(0) was determined to be 4.81. The XPS data for MCM-41-
3N-Pd(0) (fresh), MCM-41-3N-Pd(II), MCM-41-3 N, PdCl2, metal Pd,
and MCM-41-3N-Pd(0) (used) are listed in Table 1. It can be seen
that the binding energies of Si2p and O1s of MCM-41-3N-Pd(II) are
similar to those of MCM-41-3 N. However the difference of N1s
binding energies between MCM-41-3N-Pd(II) and MCM-41-3 N is
0.8 eV. The binding energy of Pd3d5/2 in MCM-41-3N-Pd(II) is 0.7 eV
less than that in PdCl2, but 2.2 eV larger than that in metal Pd. These
results show that a coordination bond between N and Pd is formed
in MCM-41-3N-Pd(II). The binding energy of Pd3d5/2 in MCM-41-
3N-Pd(0) (fresh) is 1.8 eV less than that in MCM-41-3N-Pd(II) and
similar to that in metal Pd, which indicating that the oxidation state
of palladium in freshly prepared MCM-41-3N-Pd(0) was Pd(0) [70].
The difference of N1s binding energies between MCM-41-3N-Pd(0)
(fresh) and MCM-41-3 N is 0.6 eV, which can be attributed to the
formation of coordination bonds between N and Pd in MCM-41-3N-
Pd(0) (fresh). In addition, the binding energy of Cl2p in the MCM-
41-3N-Pd(0) (fresh) cannot be detected, together with the change
in color (from light yellow to gray) also suggests that the reduction
of the starting MCM-41-3N-Pd(II) to the MCM-41-3N-Pd(0) has
taken place.
Fig. 3. Pore size distributions of MCM-41 and MCM-41-3N-Pd(0).
characteristic of mesoporous materials according to the IUPAC
classification. As shown in Fig. 3, the pore volume and size of the
MCM-41-3N-Pd(0) complex reduced apparently compared with
the parent MCM-41, also indicating the organic moieties were
introduced into the inner channels, but the pore still remained a
narrow distribution. After the grafting the tridentate nitrogen
palladium(0) complex onto MCM-41, the surface area and pore
diameter decreased from 906 m2/g and 2.7 nm to 652 m2/g and
2.2 nm, respectively, indicating that the ordered mesostructure of
the parent MCM-41 remained almost unchanged.
Fig. 4 shows the transmission electron micrograph (TEM) image
of MCM-41-3N-Pd(0) complex. The highly ordered structure with a
hexagonal ordered porous parallel channels can be clearly observed
in this figure, which indicating that the Pd complex grafting did not
cause a drastic change on the mesoporous structure of parent
MCM-41. In addition, we can easily observe the palladium(0)
nanoparticles as black dots either inside the pore of the meso-
porous MCM-41 or impregnated on the external surface of MCM-
3.2. Heterogeneous palladium(0)-catalyzed cross-coupling reaction
of aryl iodides with diphenylphosphine
The MCM-41-supported tridentate nitrogen palladium(0) com-
plex was then used as catalyst for the CeP coupling reaction of aryl
iodides with diphenylphosphine. Initial experiments with iodo-
benzene (1a) and diphenylphosphine were performed to optimize
the reaction conditions, and the results are summarized in Table 2.
At first, the effect of base on the model reaction was examined with
DMAc as solvent at 120 ꢀC (Table 2, entries 1e5). For the bases
evaluated [Cs2CO3, K2CO3, KOAc, K3PO4 and n-Bu3N], KOAc gave the
best result, while other bases were substantially less effective.
When DMAc was replaced by other solvents, DMF and NMP also
Fig. 4. TEM image of MCM-41-3N-Pd(0).
Fig. 5. Wide angle XRD patterns of MCM-41-3N-Pd(0).

Z. Xu et al. / Journal of Organometallic Chemistry 866 (2018) 50e58
55
Table 1
catalytic system involved the use of MCM-41-3N-Pd(0) (1 mol%),
KOAc as base in DMAc at 130 ꢀC under Ar for 3 h (Table 2, entry 10).
With the optimized conditions established, we tried to investi-
gate the scope and limitations of this heterogeneous palladium(0)-
catalyzed CeP coupling reaction and the results are summarized in
Table 3. As shown in Table 3, both electron-rich and electron-
deficient aryl iodides 1b-1u proved to be suitable coupling part-
ners and gave the corresponding unsymmetrical triarylphosphines
2b-2u in good to excellent yields. For instance, aryl iodides bearing
various electron-donating groups 1b-1g underwent the cross-
coupling reaction smoothly to give the desired products 2b-2g in
79e92% yields. For electron-deficient aryl iodides having either
weak electron-withdrawing groups such as fluoro, chloro and
bromo 1h-1j or strong electron-withdrawing groups such as cyano,
acetyl, trifluoromethyl, nitro, and ester 1k-1p, the cross-coupling
reactions also proceeded effectively to afford the corresponding
triarylphosphines 2h-2p in 77e87% yields. These results indicate
that the electronic nature of the substituent on the benzene ring
has limited influence on the heterogeneous palladium-catalyzed
CeP bond formation reaction. Base-sensitive functional groups
such as methyl ketone (1l) and esters (1o, 1p) are tolerated by this
method. In addition, the sterically congested o-substituted aryl
iodides such as 2-chloroiodobenzene 1q, 2-iodotoluene 1r, 2-
iodoanisole 1s, 2-iodobiphenyl 1t and methyl 2-iodobenzoate 1u
were also coupled with diphenylphosphine effectively to furnish
the desired coupled products 2q-u in 61e83% yields. It is note-
worthy that the bulky 1-iodonaphthalene 1v showed high reac-
tivity and produced the desired product 2v in 90% yield.
Heteroatoms turned out to be compatible with the employed re-
action conditions, the reactions of 2-iodopyridine 1w and 2-
iodothiophene 1x with diphenylphosphine afforded the corre-
sponding products 2w and 2x in 80 and 84% yields, respectively.
Encouraged by the above results, we attempted to perform the
XPS data for MCM-41-3N-Pd(0) (fresh), MCM-41-3N-Pd(II), MCM-41-3 N, PdCl2,
metal Pd and MCM-41-3N-Pd(0) (used).a
Sample
Pd3d5/2
N1s
Si2p
O1s
Cl2p
MCM-41-3N-Pd(0) (fresh)
MCM-41-3N-Pd(II)
MCM-41-3 N
PdCl2
Metal Pd
335.6
337.4
400.4
400.6
399.8
103.2
103.3
103.2
533.3
533.3
533.4
199.2
199.3
338.1
335.2
335.5
MCM-41-3N-Pd(0) (used)
400.5
103.3
533.4
a
The binding energies are referenced to C1s (284.6 eV) and the energy differences
were determined with an accuracy of 0.2 eV.
provided good results, whilst DMSO and toluene gave lower yields
(Table 2, entries 6e9), so DMAc was the best choice, which may be
due to the good solubility of KOAc in DMAc (Table 2, entry 3). Our
next studies focused on the effect of reaction temperature on the
model reaction. When reaction temperature was raised to 130 ꢀC,
the yield of 2a was improved to 86% within 3 h (Table 2, entry 10),
but further raising temperature to 140 ꢀC resulted in a slightly
decreased yield due to the easy oxidation of diphenylphosphine at
high temperature (Table 2, entry 11). When a homogeneous
Pd(OAc)2 or Pd(PPh3)4 was used as the catalyst, the desired product
2a was also isolated in 87 and 86% yield, respectively (Table 2,
entries 12 and 13), which indicating that catalytic activity of MCM-
41-3N-Pd(0) was comparable to that of homogeneous Pd(OAc)2 or
Pd(PPh3)4. Finally, the amount of the supported palladium catalyst
was screened, and 1 mol% loading of palladium was found to be
optimal, a lower yield was observed and a longer reaction time was
required when the amount of the catalyst was decreased to 0.5 mol
% (Table 2, entry 14). Increasing the amount of the palladium
catalyst could shorten the reaction time, but did not improve the
yield of 2a significantly (Table 2, entry 15). Therefore, the optimal
Table 2
Optimization of reaction conditions for the cross-coupling of iodobenzene with diphenylphosphine.a
Entry
Base
Solvent
Temp. (ºC)
Time (h)
Yield (%)b
1
2
3
4
5
6
7
8
Cs2CO3
K2CO3
KOAc
K3PO4
n-Bu3N
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMF
120
120
120
120
120
120
120
120
120
130
140
130
130
130
130
12
12
6
12
12
6
45
33
74
22
51
67
70
49
43
86
83
87
86
73
87
NMP
6
DMSO
toluene
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
12
12
3
2
3
3
7
2
9
10
11
12c
13d
14e
15f
a
Reaction was performed with 1a (1.0 mmol), Ph2PH (1.2 mmol), base (1.5 mmol) and MCM-41-3N-Pd(0) (0.01 mmol, 1 mol%) in solvent (1 mL) under Ar.
b
c
d
e
f
Isolated yield based on 1a.
Pd(OAc)2 (1 mol%) was used.
Pd(PPh3)4 (1 mol%) was used.
0.5 mol% MCM-41-3N-Pd(0) was used.
2 mol% MCM-41-3N-Pd(0) was used.

56
Z. Xu et al. / Journal of Organometallic Chemistry 866 (2018) 50e58
Table 3
Heterogeneous palladium-catalyzed synthesis of unsymmetrical triarylphosphines via cross-coupling of aryl iodides with Ph2PH.a,b
reaction of bromobenzene with diphenylphosphine under the
same conditions, unfortunately, only a trace of the desired product
2a was detected, so 4-bromoiodobenzene 1j was selectively sub-
jected to the CeP coupling reaction to give the desired product 2j in
83% yield. Even if 4-nitrobromobenzene bearing a strong electron-
withdrawing group was used as substrate, the desired product 2n
was obtained in only 12% isolated yield after 24 h. The present
protocol provides a quite general and practical route for the syn-
thesis of a wide variety of unsymmetrical triarylphosphines having
various functionalities.
contribution to the observed catalysis from a homogeneous palla-
dium species demonstrating that the MCM-41-3N-Pd(0) catalyst
In order to determine whether the observed catalysis was due to
the heterogeneous catalyst MCM-41-3N-Pd(0) or to a leached
palladium species in solution, the reaction of iodobenzene 1a with
diphenylphosphine was carried out until an approximately 30%
conversion of iodobenzene 1a was reached. Then MCM-41-3N-
Pd(0) catalyst was removed from the reaction mixture by hot
filtration [71] and the filtrate was allowed to react further at 130 ꢀC
under Ar atmosphere for 3 h. In this case, no significant increase in
conversion of iodobenzene 1a was observed, indicating that
leached palladium species from the supported catalyst (if any) are
not responsible for the observed activity. It was also confirmed by
ICP-AES analysis that no palladium species could be detected in the
filtrate (below the detection limit). These results rule out any
Fig. 6. Recycle of MCM-41-3N-Pd(0) catalyst.

Z. Xu et al. / Journal of Organometallic Chemistry 866 (2018) 50e58
57
was stable during the reaction and the observed catalysis was
References
intrinsically heterogeneous. In order to further examine the sta-
bility of MCM-41-3N-Pd(0) complex at the catalytic temperature of
130 ꢀC, the XPS analysis of the used MCM-41-3N-Pd(0) was per-
formed and the results are also listed in Table 1. As shown in Table 1,
the binding energies of Pd3d5/2 and N1s of the used MCM-41-3N-
Pd(0) are similar to those of the fresh one, which indicating that
the MCM-41-3N-Pd(0) complex is stable at the reaction tempera-
ture and is in this form but not metal Pd(0) alone. The mechanism
for this heterogeneous palladium-catalyzed CeP coupling reaction
could follow the proposal made by Buchwald and Beller for the
palladium-catalyzed amination of aryl bromides [72,73].
[1] G.M. Kosolapoff, L. Maier, Organic Phosphorous Compounds, second ed., vol. 1,
Wiley-Interscience, New York, 1972.
[2] Organophosphorous Chemistry, The Royal Society of Chemistry, vols. 1e15,
1969-1983. London.
[3] I.P. Beletskaya, M.A. Kazankova, Russ. J. Org. Chem. 38 (2002) 1391e1430.
[4] I. Ojima, N. Clos, C. Bastos, Tetrahedron 45 (1989) 6901e6939.
[5] J.P. Wolfe, S. Wagaw, J.-F. Marcoux, S.L. Buchwald, Acc. Chem. Res. 31 (1998)
805e818.
[6] J.F. Hartwig, Acc. Chem. Res. 31 (1998) 852e860.
[7] I. Ojima, Catalytic Asymmetric Synthesis, VCH, New York, 1993.
[8] F. Zheng, T.-F. Leung, K.-W. Chan, H.H.Y. Sung, L.D. Williams, Z. Xie, G. Jia,
Chem. Commun. 52 (2016) 10767e10770.
[9] U.P.N. Tran, K.J. Hock, C.P. Gordon, R.M. Koenigs, T.V. Nguyen, Chem. Commun.
53 (2017) 4950e4953.
[10] H.-W. Shin, J.A. Prescher, J. Am. Chem. Soc. 137 (2015) 10036e10039.
[11] F.K. Kwong, K.S. Chan, Organometallics 19 (2000) 2058e2060.
[12] H. Zhou, J. Li, H. Yang, C. Xia, G. Jiang, Org. Lett. 17 (2015) 4628e4631.
[13] O. Herd, A. Hessler, M. hingst, M. Trepper, O. Stelzer, J. Organomet. Chem. 522
(1996) 69e76.
[14] P. Machnitzki, T. Nickel, O. Stelzer, C. Landgrafe, Eur. J. Inorg. Chem. (1998)
1029e1034.
[15] D. Gelman, L. Jiang, S.L. Buchwald, Org. Lett. 5 (2003) 2315e2318.
3.3. Recycling of the catalyst
For the practical application of a supported precious metal cata-
lyst, its stability and recyclability are important factors. We next
examined the recycle of the MCM-41-3N-Pd(0) complex by using
cross-coupling reaction of 4-iodobenzenamine (1 mmol) and
diphenylphosphine (1.2 mmol) in DMAc (1 mL) with KOAc
(1.5 mmol) as base in the presence of 1.0 mol% of MCM-41-3N-Pd(0)
at 130 ꢀC under argon atmosphere for 3 h. After completion of the
reaction, the catalyst was separated by a simple filtration of the re-
action solution and washed with distilled water and ethanol. After
being air-dried, it can be reused directly without further purification.
The recovered catalyst was used in the next run, and almost the same
yield of 2f was observed for 8 consecutive cycles (Fig. 6). In order to
show that the catalyst remains the same after each run of catalytic
cycle, palladium leaching in the heterogeneous catalyst was also
determined by ICP-AES analysis on the recovered catalyst after each
run, the palladium content was found to be 0.48, 0.49, 0.47, 0.48,
0.48, 0.47, and 0.48 mmol/g respectively, which revealing almost the
same palladium content as the fresh one. In our opinion, the high
catalytic activity and excellent recyclability of the palladium catalyst
may be due to the efficient site isolation, to the optimal dispersion of
the active sites on the inner channel walls and to the relatively strong
interaction between the tridentate nitrogen ligand and the palla-
dium centre supported on the MCM-41. The result is important from
the standpoint of green and sustainable chemistry.
[16] L.J. Gooben, M.K. Dezfuli, Synlett (2005) 445e448.
[17] S. Thielges, P. Bisseret, J. Eustache, Org. Lett. 7 (2005) 681e684.
[18] M. Kalek, J. Stawinski, Organometallics 26 (2007) 5840e5847.
[19] M. Kalek, A. Ziadi, J. Stawinski, Org. Lett. 10 (2008) 4637e4640.
[20] Y. Belabassi, S. Alzghari, J.M. Montchamp, J. Organomet. Chem. 693 (2008)
3171e3178.
[21] A. Bessmertnykh, C.M. Douaihy, S. Muniappan, R. Guilard, Synthesis (2008)
1575e1579.
[22] M. Kalek, M. Jezowska, J. Stawinski, Adv. Synth. Catal. 351 (2009) 3207e3216.
[23] D. Hockova, M. Dracinsky, A. Holy, Eur. J. Org Chem. (2010) 2885e2892.
[24] E.L. Deal, C. Petit, J.L. Montchamp, Org. Lett. 13 (2011) 3270e3273.
[25] T. Ogawa, N. Usuki, N. Ono, J. Chem. Soc. Pekin Trans. 1 (1998) 2953e2958.
[26] D. Van Allen, D. Venkataraman, J. Org. Chem. 68 (2003) 4590e4593.
[27] D. Gelman, L. Jiang, S.L. Buchwald, Org. Lett. 5 (2003) 2315e2318.
[28] H.H. Rao, Y. Jin, H. Fu, Y.Y. Jiang, Y.F. Zhao, Chem. Eur J. 12 (2006) 3636e3646.
[29] D.J. Ager, S.A. Laneman, Chem. Commun. (1997) 2359e2360.
[30] F.Y. Kwong, A.S.C. Chan, K.S. Chan, Tetrahedron 56 (2000) 8893e8899.
[31] M. Jahjah, R. Jahjah, S. Pellet-Rostaing, M. Lemaire, Tetrahedron: Asymmetry
18 (2007) 1224e1232.
[32] J. Horn, W. Bannwarth, Eur. J. Org Chem. (2007) 2058e2063.
[33] D. Marcoux, A.B. Charette, Adv. Synth. Catal. 350 (2008) 2967e2974.
[34] D. Cai, J.F. Payack, D.R. Bender, D.L. Hughes, T.R. Verhoeven, P.J. Reider, J. Org.
Chem. 59 (1994) 7180e7181.
[35] Y. Li, S. Das, S. Zhou, K. Junge, M. Beller, J. Am. Chem. Soc. 134 (2012)
9727e9732.
[36] Y. Li, L.-Q. Lu, S. Das, S. Pisiewicz, K. Junge, M. Beller, J. Am. Chem. Soc. 134
(2012) 18325e18329.
[37] M.-L. Schirmer, S. Jopp, J. Holz, A. Spannenberg, T. Werner, Adv. Synth. Catal.
358 (2016) 26e29.
[38] M. Kuroboshi, T. Kita, A. Aono, T. Katagiri, S. Kikuchi, S. Yamane, H. Kawakubo,
H. Tanaka, Tetrahedron Lett. 56 (2015) 918e920.
4. Conclusion
In conclusion, an efficient and phosphine-free MCM-41-3N-
Pd(0) catalyst has been synthesized by a simple procedure from
commercially readily available materials. The new heterogeneous
palladium catalyst was characterized by various characterization
techniques like elemental analysis, XRD, N2 sorption analyses, TEM
and XPS. We have shown that MCM-41-3N-Pd(0) can catalyze the
cross-coupling of various aryl iodides with diphenylphosphine to
yield a variety of unsymmetrical triarylphosphines in good to
excellent yields and exhibit the same catalytic activity as homo-
geneous Pd(OAc)2 or Pd(PPh3)4 complex. The reactions tolerated a
wide range of functional groups, including base-sensitive groups.
The catalyst can be easily recovered by a simple filtration and re-
used at least seven times without significant loss of activity, thus
making this procedure economically and environmentally more
acceptable. Further work is in progress to develop new carbon-
heteroatom bond formations catalyzed by this catalytic system.
[39] C.E. Garrett, K. Prasad, Adv. Synth. Catal. 346 (2004) 889e900.
[40] D.J. Cole-Hamilton, Science 299 (2003) 1702e1706.
[41] N.T.S. Phan, M.V.D. Sluys, C.W. Jones, Adv. Synth. Catal. 348 (2006) 609e679.
[42] M.J. Climent, A. Corma, S. Iborra, Chem. Rev. 111 (2011) 1072e1133.
[43] L. Yin, J. Liebscher, Chem. Rev. 107 (2007) 133e173.
[44] A. Molnar, Chem. Rev. 111 (2011) 2251e2320.
[45] C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli, J.S. Beck, Nature 359 (1992)
710e712.
[46] A. Taguchi, F. Schuth, Microporous Mesoporous Mater. 77 (2005) 1e45.
[47] R.M. Martin-Aranda, J. Cejka, Top. Catal. 53 (2010) 141e153.
[48] P.C. Mehnert, D.W. Weaver, J.Y. Ying, J. Am. Chem. Soc. 120 (1998)
12289e12296.
[49] K. Mukhopadhyay, B.R. Sarkar, R.V. Chaudhari, J. Am. Chem. Soc. 124 (2002)
9692e9693.
[50] M. Cai, G. Zheng, G. Ding, Green Chem. 11 (2009) 1687e1693.
[51] M. Cai, J. Peng, W. Hao, G. Ding, Green Chem. 13 (2011) 190e196.
[52] W. Hao, H. Liu, L. Yin, M. Cai, J. Org. Chem. 81 (2016) 4244e4251.
[53] S.-G. Shyu, S.-W. Cheng, D.-L. Tzou, Chem. Commun. (1999) 2337e2338.
[54] M. Jia, A. Seifert, W.R. Thiel, Chem. Mater. 15 (2003) 2174e2180.
[55] A. Corma, E. Gutierrez-Puebla, M. Iglesias, A. Monge, S. Perez-Ferreras,
F. Sanchez, Adv. Synth. Catal. 348 (2006) 1899e1907.
[56] G. Villaverde, A. Corma, M. Iglesias, F. Sanchez, ACS Catal. 2 (2012) 399e406.
[57] H. Zhao, W. He, R. Yao, M. Cai, Adv. Synth. Catal. 356 (2014) 3092e3098.
[58] H. Zhao, W. He, L. Wei, M. Cai, Catal. Sci. Technol 6 (2016) 1488e1495.
[59] S.E. Tunney, J.K. Stille, J. Org. Chem. 52 (1987) 748e753.
[60] E.A. Yakovleva, E.N. Tsvetkov, D.I. Kabahnik, A.I. Shatenshtein, Tetrahedron
Lett. (1966) 4161e4166.
Acknowledgements
We thank the National Natural Science Foundation of China (No.
21462021) and Key Laboratory of Functional Small Organic Mole-
cule, Ministry of Education (No. KLFS-KF-201704) for financial
support.
[61] M. Joshaghani, E. Faramarzi, E. Rafiee, M. Daryanavard, J. Xiao, C. Baillie, J. Mol.
Catal. Chem. 259 (2006) 35e40.

58
Z. Xu et al. / Journal of Organometallic Chemistry 866 (2018) 50e58
[62] S.I. Pombrik, V.F. Ivanov, A.S. Peregudov, D.N. Kravtsov, A.A. Fedorov,
E.I. Fedin, J. Organomet. Chem. 153 (1978) 319e326.
[69] S. Navaladian, B. Viswanathan, T.K. Varadarajan, R.P. Viswanath, Nanoscale
Res. Lett. 4 (2009) 181e186.
[63] F.Y. Kwong, C.W. Lai, M. Yu, K.S. Chan, Tetrahedron 60 (2004) 5635e5645.
[64] E.L. Gall, M. Troupel, J.-Y. Nedelec, Tetrahedron 59 (2003) 7497e7500.
[65] G.P. Schiemenz, Eur. J. Inorg. Chem. 99 (1966) 514e519.
[66] F.A. Hart, J. Chem. Soc. (1960) 3324e3328.
[67] E. Rafler, D.G. Gilheany, J.N.H. Reek, P.W.N.M. van Leeuwen, ChemCatChem 2
(2010) 387e391.
[70] P. Li, L. Wang, L. Zhang, G.-W. Wang, Adv. Synth. Catal. 354 (2012)
1307e1318.
[71] H.E.B. Lempers, R.A. Sheldon, J. Catal. 175 (1998) 62e69.
[72] A.S. Guram, R.A. Rennels, S.L. Buchwald, Angew. Chem. 107 (1995)
1456e1459.
[73] M. Beller, Angew. Chem. 107 (1995) 1436e1437.
[68] F.G. Mann, J. Watson, J. Org. Chem. 13 (1948) 502e531.