Synthesis, structure, and catalytic activity of rare-earth metal amides with a neutral pyrrolyl-functionalized indolyl ligand

Article abstract of DOI:10.1007/s11426-014-5150-7

The reactions of neutral pyrrolyl-functionalized indole with rare-earth metal amides [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF) ₃ produced the rare-earth metal complexes [(Me₃Si) ₂N]₂RE([η¹:μ-η²-3-(2-(N- CH₃)C₄H₃NCH=N-CH₂CH ₂)C₈H₅N])(μ-Cl)Li(THF) (RE = Er, Y) having indolyl ligand η¹ bonded to rare-earth metal ion and η² bonded to lithium ion. The catalytic activities of these lanthanide amido complexes for addition of terminal alkynes to aromatic nitriles were explored. Results reveal that these complexes displayed a good catalytic activity for the addition reaction under mild conditions.

Full text of DOI:10.1007/s11426-014-5150-7

SCIENCE CHINA
Chemistry
August 2014 Vol.57 No.8: 1090–1097
doi: 10.1007/s11426-014-5150-7
• ARTICLES •
Synthesis, structure, and catalytic activity of rare-earth metal
amides with a neutral pyrrolyl-functionalized indolyl ligand
YANG Song1, ZHU XianCui1*, ZHOU ShuangLiu1, WANG ShaoWu1,2*, FENG ZhiJun1,
WEI Yun1, MIAO Hui1, GUO LiPing1, WANG FenHua1, ZHANG GuangChao1,
GU XiaoXia1 & MU XiaoLong1
1Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, School of Chemistry
and Materials Science, Anhui Normal University, Wuhu 241000, China
2State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, China
Received February 28, 2014; accepted March 21, 2014; published online June 23, 2014
The reactions of neutral pyrrolyl-functionalized indole with rare-earth metal amides [(Me3Si)2N]3RE(-Cl)Li(THF)3 produced
the rare-earth metal complexes [(Me3Si)2N]2RE([1:-2-3-(2-(N–CH3)C4H3NCH=N–CH2CH2)C8H5N])(-Cl)Li(THF) (RE =
Er, Y) having indolyl ligand 1 bonded to rare-earth metal ion and 2 bonded to lithium ion. The catalytic activities of these
lanthanide amido complexes for addition of terminal alkynes to aromatic nitriles were explored. Results reveal that these com-
plexes displayed a good catalytic activity for the addition reaction under mild conditions.
terminal alkyne, aromatic nitrile, ynone, rare-earth metal
presence of a palladium catalyst through decarboxylative
1 Introduction
coupling is noteworthy [18]. Another method started from
reactions of terminal alkynes and acyl chlorides with em-
ployment of a palladium catalyst system [19–25]. Corrosive
acyl chlorides or strictly prepared carbon monoxide as sub-
strates, as well as indispensable stoichiometric amounts of
bases, should be used in this method. A method for avoiding
the use of bases was developed, based on an iron-catalyst
system for the coupling reactions between the silylated al-
kynes and acyl chlorides for the preparation of ynones [26],
but this reaction requires low temperature (15 °C), and
must be carried out in toxic MeNO2. The direct additions of
terminal alkynes to aromatic nitriles to produce conjugated
ynones in the presence of lanthanide amides as catalysts
were reported very recently [27, 28]; to date, these are only
two reports based on rare-earth metal catalysts. Thus the
need to development of new rare-earth catalysts for the
preparation of conjugated ynones by reaction of aromatic
nitriles with terminal alkynes remains.
Conjugated ynones are important building blocks widely
found in bioactive and synthetic materials [1–4] and are
important synthons in synthetic chemistry especially for
syntheses of heterocylic compounds [5–9]. Development of
synthetic methods for the prepration of an ynones system
based on transition metal-catalyzed cross-coupling reactions
has attracted much attention, and several successful meth-
ods are documented. Original works started from reactions
of aryl derivatives and terminal alkynes under CO atmos-
phere in the presence of palladium catalysts. The aryl hal-
ides were used in the reactions from the very beginning;
aryl triflates or aryl amines were developed as substrates
[10–17]. The method by which alkynyl carboxylic acids
reacted with aryl iodides under a CO atmosphere in the
Dedicated to Professor Qian Changtao on the occasion of his 80th birthday.
*Corresponding authors (email: zxc5872271@126.com; swwang@mail.ahnu.edu.cn)
Because electronic and steric properties of the amido
© Science China Press and Springer-Verlag Berlin Heidelberg 2014
chem.scichina.com link.springer.com

Yang S, et al. Sci China Chem August (2014) Vol.57 No.8
1091
ligand can be easily tuned, trivalent rare-earth-metal amido
complexes have been reported to show broaden applications
in catalytic transformations of unsaturated compounds
[29–37] or as catalysts in synthetic chemistry [38–44]. Re-
cently, due to their bonding capability, functionalized pyr-
roles and indoles have received particular attention as ver-
satile ligands in rare-earth metal chemistry, and are antici-
pated as alternatives to cyclopentadienyl or indenyl ligands
[45–49]. In our recent studies, we found that reactions of
different functionalized pyrroles or indoles with rare-earth
metal amides displayed different bonding modes and dif-
ferent reactivities. Reactions of 3-t-butylimino-functional-
ized indole with rare-earth metal amides [(Me3Si)2N]3RE(-
Cl)Li(THF)3 (RE = Yb, Y) produced novel rare-earth metal
complexes containing an unusual indolyl-1,2-dianion
bonded to the metals in a novel 1:(2-1:1) mode through
imino-directed C–H bond activation [50]. In addition, the
reaction of [(Me3Si)2N]3LnIII(-Cl)Li(THF)3 with 2 equiv.
of 3-(CyNHCH2)C8H5NH in toluene produced the amino-
coordinate-lithium bridged bis(indolyl) lanthanide amides
[-{[1:1:1:1-3-(CyNHCH2)Ind]2Li}RE[N(SiMe3)2]2]
(Cy = cyclohexyl, Ind = Indolyl) [51]. Recently, we found
that reaction of 2-(2,6-diisopropylphenylaminomethylene)
indole 2-(2,6-iPr2C6H3NHCH2)C8H5NH with europium am-
ide [(Me3Si)2N]3Eu(-Cl)Li(THF)3 afforded a novel euro-
pium(II) complex formulated as {[-6:1:1-2-(2,6-
iPr2C6H3N=CH)C8H5N]Eu[2-(2,6-iPr2C6H3N=CH)-
C8H5N]}2 and having a bridged indolyl ligand in novel
-6:1:1 hapticities with the reduction of europium(III)
to europium(II), oxidation of the amino to imino groups. In
addition, reactivity studies led to findings of novel bonding
modes of the indolyl ligands with europium(II) metal [52].
We also found that reactions of N-((1H-pyrrol-2-yl)-
methylene)-2-(1H-indol-3-yl)-ethanamine 3-(2-C4H3NHCH=
NCH2CH2) C8H5NH with rare-earth metal amides
[(Me3Si)2N]3RE(-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y)
afforded a series of novel trinuclear rare-earth metal amido
complexes that incorporate indolyl ligand in -5:1 bond-
ing modes and a 3-O group [37]. Here we report the syn-
thesis of the trivalent rare-earth-metal amido complexes
supported by neutral pyrrolyl-functionalized indolyl ligand
and their catalytic activity of addition of terminal alkynes to
nitriles.
before use. Other reagents were used as commercial ones
without further purification unless otherwise noted.
[(Me3Si)2N]3RE(-Cl)Li(THF)3 (RE = Yb, Dy, Er, Y) were
prepared according to literature methods [53, 54]. The lig-
and 3-(2-(N–CH3)C4H3NCH=NCH2CH2)–C8H5NH (1) and
the complexes (2 for Yb, and 3 for Dy) were also prepared
according to literature methods [37]. 1H NMR and 13C NMR
spectra were recorded on a Bruker AV-300 NMR spectrom-
eter (300 MHz for 1H; 75.0 MHz for 13C in C6D6 for lantha-
nide complexes and in CDCl3 for organic compounds.
Chemical shifts () were reported in ppm and relative to
TMS. IR spectra were recorded on a Shimadzu FTIR-8400s
spectrometer (KBr pellet). Elemental analyses data were
obtained on a Perkin-Elmer 2400 Series II elemental ana-
lyzer for CHN analysis. Melting points were determined in
sealed capillaries without correction. High-resolution mass
spectra (HRMS) were obtained on an Agilent 6200 MS in-
strument.
2.2 Synthesis of the complexes
[(Me3Si)2N]2Er[1:-2-3-(2-(N–CH3)C4H3NCH=N–CH2–
CH2)C8H5N])(-Cl)Li(THF) (4)
To a toluene (10.0 mL) solution of 3-(2-(N–CH3)C4H3-
NCH=NCH2CH2)C8H5NH (0.253 g, 1.00 mmol) we added a
toluene (20.0 mL) solution of [(Me3Si)2N]3Er(-Cl)Li-
(THF)3 (0.908 g, 1.00 mmol) at room temperature and ob-
tained a clear light-brown solution. As the reaction mixture
was heated at 75 °C for 36 h, the color gradually changed to
a darker brown. The solvent was evaporated under reduced
pressure. The residue was extracted with n-hexane (2  15.0
mL). The combined extractions were concentrated to about
10.0 mL. Pink crystals were obtained at room temperature
overnight (0.664 g, 78% yield), m.p. 173–178 °C. max (KBr,
cm1): 2929 s, 2881 s, 1633 s, 1535 m, 1512 s, 1388 m,
1226 s, 1215 s, 1147 s, 1068 w, 935 w. Found: C, 45.05; H,
7.04; N, 7.97. Calc. for C32H60ClLiN5OSi4Er: C, 45.07; H,
7.09; N, 8.21%.
[(Me3Si)2N]2Y[1:-2-3-(2-(N–CH3)C4H3NCH=N–CH2–
CH2)C8H5N])(-Cl)Li(THF) (5)
This compound was isolated as colorless crystals in 73%
yield by treatment of a toluene (10.0 mL) solution of ligand
1 (0.253 g, 1.00 mmol) with [(Me3Si)2N]3Y(-Cl)Li-
(THF)3 (0.830 g, 1.00 mmol) following procedures similar
to the preparation of 4. m.p. 177–181 °C (dec.). max (KBr,
cm1): 2934 s, 2878 s, 1631 s, 1541 m, 1509 s, 1383 m,
1233 s, 1224 s, 1139 s, 1061 w, 927 w. Found: C, 50.48; H,
8.12; N, 8.90. Calc. for C32H60ClLiN5OSi4Y·0.25C6H14: C,
50.55; H, 8.04; N, 8.80%. H (300 MHz, C6D6, ppm): 8.44
(m, 1H), 7.85 (m, 1H), 7.39–7.34 (m, 1H), 7.20–7.06 (m),
6.91 (s), 6.66 (s), 3.97 (m, 3H), 3.47 (s, 2H), 3.08 (m, 2H),
2.47, 1.82 (m, 4H), 1.63–0.91 (hexane), 0.65 (s), 0.27 (s),
2 Experimental
2.1 General information
All syntheses and manipulations of air- and moisture-sensi-
tive materials were performed under a purified Ar atmos-
phere using standard Schlenk techniques or in a glovebox.
Hexane, toluene, and THF were refluxed and distilled from
sodium benzophenone ketyl under Ar prior to use. All al-
kynes and nitriles were predried, recrystallized or redistilled

1092
Yang S, et al. Sci China Chem August (2014) Vol.57 No.8
0.07 (s). 13C NMR (75 MHz, C6D6, ppm): C 146.1, 146.0,
129.2, 125.2, 125.2, 124.5, 120.9, 120.5, 66.5, 36.95, 36.4,
21.6, 17.0, 16.6, 1.4.
Table 1 Crystallographic data for complexes 4 and 5
Compounds
Formula
Formula wt
Cryst system
Space group
a (Å)
4
5
C32H60ClErLiN5OSi4 C35H67ClYLiN5OSi4
852.86
triclinic
P1
817.60
monoclinic
P21/n
2.3 X-ray structure determination and refinement
13.198(3)
17.905(4)
21.327(4)
105.859(2)
94.948(3)
102.857(2)
4667.9(17)
4
16.2287(12)
15.9464(12)
18.3705(14)
90
A suitable crystal of complexes 2–5 was mounted in a
sealed capillary. Diffraction was performed on a Bruker
SMART APEX II CCD area detector diffractometer (Bruker
AXS GmbH, Germany) using graphite-monochromated
Mo-Kα radiation ( = 0.71073 Å), temperature 293(2) K,
and - and -scan technique. An empirical absorption cor-
rection was applied using the SADABS program [55]. All
structures were solved by direct methods, completed by
subsequent difference Fourier syntheses, and refined aniso-
tropically for all non-hydrogen atoms by full-matrix
least-squares calculations based on F2 using the SHELXTL
program package (Bruker AXS Inc., USA) [56]. The hy-
drogen atom coordinates were calculated with SHELXTL
using an appropriate riding model with varied thermal pa-
rameters. During refinement, constraints are used because
of the presence of well-known disordered groups such as
THF, ethylene group and terminal methyl group. All disor-
dered parts based on ideal structures were restrained by us-
ing DFIX, DELU, or SIMU instructions to make the geo-
metrical configurations and the displacement parameters
more reasonable. The residual electron densities were of no
chemical significance. Crystal data and details of the data
collection and structure refinements are given in Table 1.
CCDC 988915 and 988916 for 4 and 5 contain the supple-
mentary crystallographic data for this paper. Please note
that these data can be obtained free of charge from the
Cambridge Crystallographic Data Centre (www.ccdc.cam.
ac.uk/data_request/cif), and are also given in the Supporting
Information online.
b (Å)
c (Å)
()
()
92.9840(10)
90
()
Volume (Å3)
4747.6(6)
4
Z
Dcalcd (gcm3)
 (mm1)
F(000)
1.214
1.144
1.984
1.415
1756
1740
1.33 to 26.00
1.63 to 27.00
range ()
16  h  15
22  k  22
20  h  20
20  k  20
23  l  21
39164/10310
[R(int) = 0.0712]
10310/18/447
Limiting indices
23  l  26
35026/17916
[R(int) = 0.0428]
17916/38/785
Reflections collected/unique
Data/restraints/parameters
GOF
1.020
1.039
Final R indices
[I > 2σ(I)]
R indices
R1 = 0.0671
wR2 = 0.1909
R1 = 0.1175
wR2 = 0.2092
R1 = 0.0531
wR2 = 0.1090
R1 = 0.1375
wR2 = 0.1390
(all data)
Largest diff. peak/hole (e/Å3)
0.973 and 1.196
0.473 and 0.300
3 Results and discussion
3.1 Synthesis and characterization of rare-earth metal
complexes
In our previous study, reactions of neutral pyrrolyl-func-
tionalized indole (2-(3-C8H5NHCH2CH2N=CH)C4H3NCH3)
(1) with [(Me3Si)2N]3RE(-Cl)Li(THF)3 (RE = Yb, Dy) in
toluene afforded the hetero-nuclear bimetallic complexes
1:1-[1-3-(2-(N–CH3)C4H3N–CH=NCH2CH2)C8H5N]Li
[-2:1-3-(2-(N–CH3)C4H3NCH=N–CH2CH2)C8H5N])RE-
[N(SiMe3)2]2 (RE = Yb(2), Dy(3)) (Scheme 1, path (a)) [37].
However, by further expansion of this reaction to rare-earth
metal Er and Y, different hetero-nuclear bimetallic com-
plexes [(Me3Si)2N]2RE([1:-2-3-(2-(N–CH3)C4H3NCH
=NCH2CH2)C8H5N])(-Cl)Li(THF) (RE = Er(4), Y(5))
(Scheme 1, path (b)) were obtained. With treatment of 1
with 0.5 equiv. of [(Me3Si)2N]3RE(-Cl)Li(THF)3 (RE = Er,
Y) under the same conditions, the same bimetallic com-
plexes 4 and 5 were isolated. Adding excess amount of lig-
and had no influence on the coordination method. These
results imply that different ionic radii of rare-earth metals
had an effect on the coordination patterns of these types of
rare-earth complex. Complexes 4 and 5 are sensitive to air
and moisture, but remain stable for months in an inert at
2.4 General experimental procedure for the addition of
alkyne to nitrile
A 25.0 mL Schlenk tube under dried Ar was charged with
complex 4 (42.6 mg, 0.05 mmol), alkynes (5 mmol), and
solvent-free or toluene (3.0 mL). Benzonitrile (1 mmol) was
then added to the mixture. The resulting mixture was stirred
at 40 °C for 36 h and then quenched with 0.5 mol/L H2SO4,
extracted with diethyl ether, dried over anhydrous sodium
sulfate, and filtered. After the solvent was removed under
reduced pressure, the final products were further purified by
flash column chromatography to afford the desired products.
Flash column chromatography was performed over silica
gel (300–400 mesh) using a mixture of petroleum ether
(30–60 °C) and ethyl acetate (15:1, 10:1) as effluent.

Yang S, et al. Sci China Chem August (2014) Vol.57 No.8
1093
Scheme 1 Preparation of complexes.
mosphere. They are soluble in polar solvents but hardly
soluble in nonpolar solvents. All complexes were charac-
terized by elemental analyses, as well as IR and X-ray anal-
yses. The representative molecular structure of complexes 4
and 5 are shown in Figure 1, Figures S1 and S2 (see the
Supporting Information online).
X-ray analyses revealed that complexes 4 and 5 are
isostructural hetero-nuclear structures. In complexes 4 and 5,
the rare-earth metal ion coordinated with one nitrogen atom
of the indolyl ring, two nitrogen atoms of N(SiMe3)2 group,
and a bridged chloride, to form a distorted tetrahedral ge-
ometry. The molecular structure was stabilized by a bridged
chloride and the lithium ion adoption of another triangular
pyramid. In 2 and 3, however, the rare-earth metal ion coor-
dinated with two nitrogen atoms from the indolyl ring and
two nitrogen atoms from the N(SiMe3)2 groups, to form a
distorted tetrahedral geometry. The lithium ion occupying
the apical position of another triangular pyramid stablized
the molecular structure [37]. The selected bond lengths and
angles of complexes 4 and 5 are listed in Table 2.
As seen in Table 2, the average distances between a rare-
earth metal ion and an N atom of an indolyl ring, 2.301(6) Å
in 4 and 2.280(3) Å in 5, are slightly shorter than 2 (2.257(3)
Å) and 3 (2.315(7) Å) [37]; this difference can be explained
by taking into consideration the change in the ionic radii of
the RE(III) ions. The average distances between a rare-earth
metal ion and an N atom in the N(SiMe3)2 group, which are
2.2305(6) Å in 4 and 2.221(3) Å in 5, are also slightly
shorter than 2 (2.2035(3) Å) and 3 (2.252(7) Å) [37]; this
difference can also be explained by taking into considera-
tion the change in the ionic radii of the RE(III) ions. The
above deviation perhaps results from the different electronic
effects and coordination environments of rare-earth metal
Table 2 Selected bond lengths (Å) and angles (°) for complexes 4 and 5
Compounds
RE(1)–Cl(1)
4
5
2.6180(18)
2.301(6)
2.232(6)
2.229(6)
2.502(14)
2.522(14)
2.043(14)
2.366(13)
1.911(15)
87.41(14)
101.16(14)
118.60(16)
114.1(2)
108.7(2)
121.9(2)
2.6212(12)
2.280(3)
2.214(3)
2.228(3)
2.459(9)
2.582(9)
2.051(7)
2.422(7)
1.864(8)
87.67(8)
121.32(8)
102.88(8)
107.75(11)
111.64(11)
120.78(10)
RE(1)–N(1)
RE(1)–N(4)
RE(1)–N(5)
Li(1)C(1)
Li(1)–C(2)
Li(1)–N(2)
Li(1)–Cl(1)
Li(1)–O(1)
N(1)–RE(1)–Cl(1)
N(4)–RE(1)–Cl(1)
N(5)–RE(1)–Cl(1)
N(4)–RE(1)–N(1)
N(5)–RE(1)–N(1)
N(5)–RE(1)–N(4)
Figure 1 Molecular structural representation of complexes 4 and 5. Hy-
drogen atoms are omitted for clarity.

1094
Yang S, et al. Sci China Chem August (2014) Vol.57 No.8
of the catalysts in hexane (Table 3, entry 20). The highest
yield can be obtained under solvent-free conditions rather
than in polar solvents (Table 3, entries 16, 18 and 19).
Therefore, we further explored the addition reaction was
using complex 4 as a catalyst (5 mol%) at 40 °C under sol-
vent-free conditions. The yield increased with the increase
of the molar ratio of alkyne to nitrile; the ratio of 5:1 proved
to be the optimum choice (Table 3, entry 13). The excess
amount of acetylene can be easily recovered.
Next, we examined the substrate scope and limitation of
this methodology (Table 4). The location of the substituent
on the phenyl ring of alkyne and nitrile had a significant
effect on this reaction. For example, the reaction of phe-
nylacetylene with ortho-substituted benzonitrile hardly gave
the desired product under the given conditions (Table 4,
entries 4 and 5), bearing either an electron-donating sub-
stituent or an electron-withdrawing substituent. The addi-
tion of o-fluorophenylacetylene to benzonitrile could pro-
vide corresponding product in lower yield (Table 4, entry 14),
perhaps because of the steric effect of the ortho-substituent
groups. As for the electronic properties of aromatic alkynes
and nitrile, there were scarcely any effects on the yields of
ynones (Table 4, entries 1–7, 9, 12, and 13). Aliphatic al-
kynes and benzonitrile proceeded smoothly to produce
the desired products in moderate yields (Table 4, entry 15).
However, the heteroaromatic alkyne and the aliphatic nitriles
ions. The distances between a lithium ion and an -position
carbon atom in an indolyl ring of 2.502(14) and 2.459(9) Å
in complexes 4 and 5, respectively, are slightly shorter than
between a lithium ion and a -position carbon atom of
2.522(14) and 2.582(9) Å. The distances between a lithium
ion and a -position carbon atom of an indolyl ring are
comparable to [-{[1:1:1:1-3-(CyNHCH2)-Ind]2Li}Ln-
[N(SiMe3)2]2] (Cy = cyclohexyl, Ind = Indolyl, Ln = Sm
(2.531(4) Å), Eu (2.522(9) Å), Dy (2.534(11) Å), and Yb
(2.528(8) Å)) [51].
3.2 Catalytic addition of alkyne to nitrile
The addition reaction of phenylacetylene (6) to benzonitrile
(7) was first examined as a model reaction using rare-earth
metal amido complexes 2–5 as catalysts; the results are
summarized in Table 3. Here we see that all of these com-
plexes can catalyze this addition reaction to afford conju-
gated ynones at room temperature under solvent-free condi-
tions or in polar solvents. In loading 5 mol% catalyst under
solvent-free conditions, complex 4 showed the highest ac-
tivity for this reaction (Table 3, entry 6). We also found that
the yield of product decreased at elevated temperature (Ta-
ble 3, entries 6 and 8–10) and the maximum yield was ob-
tained at 40 °C (Table 3, entry 8). The addition reaction
cannot proceed in hexane, probably due to the insolubility
Table 3 Optimizations of the reaction conditions
Entry
1
Catalyst
Catalyst loading (mol%)
Time (h)
24
T (°C)
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
40
60
0
6a/7a
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
2:1
3:1
5:1
8:1
5:1
5:1
5:1
5:1
5:1
5:1
Solvent
Yield (%) a)
trace
42
3
3
3
3
2
4
5
4
4
4
4
4
4
4
4
4
4
4
4
4
1
2.5
5
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
THF
2
24
3
24
47
4
10
5
24
49
5
24
48
6
5
24
53
7
5
24
27
8
5
24
56
9
5
24
21
10
11
12
13
14
15
16
17
18
19
20
5
24
33
5
24
40
40
40
40
40
40
40
40
40
40
60
5
24
69
5
24
71
5
24
72
5
12
41
5
36
74
5
48
68
5
36
52
5
36
toluene
66
5
36
hexane
trace
a) Isolated yield based on nitrile.

Yang S, et al. Sci China Chem August (2014) Vol.57 No.8
Table 4 The addition of alkynes to nitriles catalyzed by complex 4 a)
1095
Entry
1
R1
Ph
R2
Ph
Solvent
Product
8a
8b
8c

Yield (%) b)
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
toluene
74
2
Ph
4-MeC6H4
3-MeC6H4
2-MeC6H4
2-O2NC6H4
4-F3CC6H4
4-ClC6H4
n-Pr
73
3
Ph
70
4
Ph
no reaction
5
Ph
no reaction

6
Ph
8d
8e

72
7
Ph
68
8
Ph
no reaction
9
4-FC6H4
4-FC6H4
4-FC6H4
4-MeC6H4
3-MeC6H4
2-FC6H4
n-Bu
Ph
8f
71
10
11
12
13
14
15
16
4-MeC6H4
4-F3CC6H4
Ph
toluene
8g
8h
8i
69
toluene
72
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
67
Ph
8j
66
41
Ph
8k
8l
Ph
61
2-thienyl
Ph
no reaction

a) The molar ratio of terminal alkynes to aromatic nitriles is 5:1; b) isolated yield based on nitrile.
Rhodium-catalyzed enantioselective synthesis, crystal structures, and
photophysical properties of helically chiral 1,1′-bitriphenylenes. J Am
Chem Soc, 2012, 134: 4080–4083
hardly produced the target product under the given condi-
tions (Table 4, entries 8 and 16).
2
3
McLeod MC, Wilson ZE, Brimble MA. Formal synthesis of berkelic
acid: a lesson in -alkylation chemistry. J Org Chem, 2012, 77: 400–
416
Plażuk D, Zakrzewski J, Nakatani K, Makal A, Woźniak K, Do-
magała S. Electronic and molecular structures and bulk second-order
nonlinear optical properties of ferrocenyl ynones. RSC Adv, 2012, 2:
3512–3524
Tsvetkov NP, Bayir A, Schneider S, Brewer M. A ring fragmentation
approach to medium-sized cyclic 2-alkynones. Org Lett, 2012, 14:
264–267
Moteki SA, Han JW, Arimitsu S, Akakura M, Nakayama K, Maruoka
K. An achiral-acid-induced switch in the enantioselectivity of a chiral
cis-diamine-based organocatalyst for asymmetric aldol and Mannich
reactions. Angew Chem Int Ed, 2012, 51: 1187–1190
Ramachary DB, Venkaiah C, Krishna PM. Discovery of
2-aminobuta-1,3-enynes in asymmetric organocascade catalysis: con-
struction of drug-like spirocyclic cyclohexanes having five to six
contiguous stereocenters. Chem Commun, 2012, 48: 2252–2254
Shi SL, Kanai M, Shibasaki M. Asymmetric synthesis of dihydropy-
ranones from ynones by sequential copper(I)-catalyzed direct aldol
and silver(I)-catalyzed oxy-Michael reactions. Angew Chem Int Ed,
2012, 51: 3932–3935
Yamamoto A, Ueda A, Brémond P, Tiseni PS, Kishi Y. Total synthe-
sis of Halichondrin C. J Am Chem Soc, 2012, 134: 893–896
Jiang HF, Pan XY, Huang LB, Zhao J, Shi DB. Synthesis of
4H-cyclopenta[c]furans via cooperative PdCl2-FeCl2 catalyzed cas-
cade cyclization reaction involving a novel acyl rearrangement pro-
cess. Chem Commun, 2012, 48: 4698–4700
4 Conclusions
We found that different central rare-earth metals had dif-
ferent coordination modes with the indolyl group in the re-
actions of neutral pyrrolyl-functionalized indoles with the
rare-earth metal amides [(Me3Si)2N]3RE(-Cl)Li(THF)3.
These complexes exhibited a catalytic activity for the addi-
tion of terminal alkynes to aromatic nitriles to produce the
corresponding ynones in moderate to good yields. The cat-
alytic reaction is well suited for a wide range of terminal
alkynes and aromatic nitriles under environmentally benign
conditions. The influence of the steric effects of aromatic
alkynes and aromatic nitriles was more powerful than the
influence of the electronic properties on this reaction. These
advantages of these complexes imply the potential applica-
tions of other rare-earth metal amides in this field. Further
works on catalytic properties of other rare-earth metal am-
ides are now in progress.
4
5
6
7
8
9
This work was supported by the National Natural Science Foundation of
China (21202002, 21372010), the National Basic Research Program of
China (2012CB821600), and grants from the Ministry of Education
(20103424110001) and Anhui Province (KJ2012A138). We are grateful to
Professor Jiping Hu and Professor Gaosheng Yang for their help in run-
ning NMR spectra.
10 Wu XF, Neumann H, Beller M. A general and convenient palladium-
catalyzed carbonylative Sonogashira coupling of aryl bromides.
Chem Eur J, 2010, 16: 12104–12107
11 Wu XF, Neumann H, Beller M. Convenient and general palladium-
catalyzed carbonylative Sonogashira coupling of aryl amines. Angew
Chem Int Ed, 2011, 50: 11142–11146
1
Sawada Y, Furumi S, Takai A, Takeuchi M, Noguchi K, Tanaka K.
12 Wu XF, Sundararaju B, Neumann H, Dixneuf PH, Beller M. A gen-

1096
Yang S, et al. Sci China Chem August (2014) Vol.57 No.8
eral palladium-catalyzed carbonylative Sonogashira coupling of aryl
Soc, 2010, 132: 16368–16371
triflates. Chem Eur J, 2011, 17: 106–110
34 Zhou SL, Wu ZS, Rong JW, Wang SW, Yang GS, Zhu XC, Zhang
LJ. Highly efficient hydrophosphonylation of aldehydes and unacti-
vated ketones catalyzed by methylene-linked pyrrolyl rare earth metal
amido complexes. Chem Eur J, 2012, 18: 2653–2659
13 Delude L, Masdeu AM, Alper H. Coupling and carbonylation of io-
doaromatics and terminal alkynes or alkynols catalyzed by a dimeric
palladium hydroxide. Synthesis, 1994, 11: 1149–1151
14 Ahmed MSM, Mori A. Carbonylative Sonogashira coupling of ter-
minal alkynes with aqueous ammonia. Org Lett, 2003, 5: 3057–3060
15 Rahman MT, Fukuyama T, Kamata N, Sato M, Ryu I. Low pressure
Pd-catalyzed carbonylation in an ionic liquid using a multiphase mi-
croflow system. Chem Commun, 2006, 21: 2236–2238
16 Liu JM, Peng XG, Sun W, Zhao YW, Xia CG. Magnetically separable
Pd catalyst for carbonylative Sonogashira coupling reactions for the
synthesis of α,β-alkynyl ketones. Org Lett, 2008, 10: 3933–3936
17 Wang Y, Liu JH, Xia CG. Cross-linked polymer supported palladium
catalyzed carbonylative Sonogashira coupling reaction in water.
Tetrahedron Lett, 2011, 52: 1587–1591
35 Zhou SL, Wang HY, Ping J, Wang SW, Zhang LJ, Zhu XC, Wei Y,
Wang FH, Feng ZJ, Gu XX, Yang S, Miao H. Synthesis and charac-
terization of organolanthanide complexes with a calix[4]-pyrrolyl
ligand and their catalytic activities toward hydrophosphonylation of
aldehydes and unactivated ketones. Organometallics, 2012, 31:
1696–1702
36 Nako AE, White AJP, Crimmin MR. A metal-amide dependent, cat-
alytic C–H functionalisation of triphenylphosphonium methylide.
Chem Sci, 2013, 4: 691–695
37 Yang S, Zhu XC, Zhou SL, Wang SW, Feng ZJ, Wei Y, Miao H,
Guo LP, Wang FH, Zhang GC, Gu XX, Mu XL. Synthesis, structure,
and catalytic activity of novel trinuclear rare-earth metal amido com-
plexes incorporating -5:1 bonding indolyl and μ3-oxo groups.
Dalton Trans, 2014, 43: 2521–2533
18 Park A, Park K, Kim Y, Lee S. Pd-catalyzed carbonylative reactions
of aryl iodides and alkynyl carboxylic acids via decarboxylative cou-
plings. Org Lett, 2011, 13: 944–947
19 Alonso DA, Nájera C, Pacheco MC. Synthesis of ynones by palla-
dium-catalyzed acylation of terminal alkynes with acid chlorides. J
Org Chem, 2004, 69: 1615–1619
20 Chen L, Li CJ, A remarkably efficient coupling of acid chlorides with
alkynes in water. Org Lett, 2004, 6: 3151–3153
38 Hong S, Marks TJ. Organolanthanide-catalyzed hydroamination. Acc
Chem Res, 2004, 37: 673–686
39 Zhang WX, Nishiura M, Hou ZM. Catalytic addition of terminal al-
kynes to carbodiimides by half-sandwich rare earth metal complexes.
J Am Chem Soc, 2005, 127: 16788–16789
21 Cox RJ, Ritson DJ, Dane TA, Berge J, Charmant JPH, Kantacha A.
Room temperature palladium catalysed coupling of acyl chlorides
with terminal alkynes. Chem Commun, 2005: 1037–1039
22 Palimkar SS, Kumar PH, Jogdand NR, Daniel T, Lahoti RJ, Sriniva-
san KV. Copper-, ligand- and solvent-free synthesis of ynones by
coupling acid chlorides with terminal alkynes. Tetrahedron Lett, 2006,
47: 5527–5530
23 Baxendale IR, Schou SC, Sedelmeier J, Ley SV. Multi-step synthesis
by using modular flow reactors: the preparation of ynones and their
use in heterocycle synthesis. Chem Eur J, 2010, 16: 89–94
24 Santra S, Dhara K, Ranjan P, Bera P, Dash J, Mandal SK. A sup-
ported palladium nanocatalyst for copper free acyl Sonogashira reac-
tions: one-pot multicomponent synthesis of N-containing heterocy-
cles. Green Chem, 2011, 13: 3238–3247
25 Bakherad M, Keivanloo A, Bahramian B, Jajarmi S. Synthesis of
ynones via recyclable polystyrene-supported palladium(0) complex
catalyzed acylation of terminal alkynes with acyl chlorides under
copper- and solvent-free conditions. Synlett, 2011, 3: 311–314
26 Gandeepan P, Parthasarathy K, Su TH, Cheng CH. Iron-catalyzed
synthesis of β-chlorovinyl and α,β-alkynyl ketones from terminal and
silylated alkynes with acid chlorides. Adv Synth Catal, 2012, 354:
457–468
27 Shen QS, Huang W, Wang JL, Zhou XG. Ln[N(SiMe3)2]3/RNH2 cat-
alyzed monoaddition of terminal alkynes to nitriles: a novel and con-
cise access to the synthesis of ynones. Organometallics, 2008, 27:
301–303
28 Ding H, Lu CR, Hu XL, Zhao B, Wu B, Yao YM. Addition of ter-
minal alkynes to aromatic nitriles catalyzed by divalent lanthanide
amides supported by amidates: synthesis of ynones. Synlett, 2013, 24:
1269–1274
29 Oyamada J, Hou ZM. Regioselective C–H alkylation of anisoles with
olefins catalyzed by cationic half-Sandwich rare earth alkyl com-
plexes. Angew Chem Int Ed, 2012, 51: 12828–12832
30 Pan Y, Xu T, Yang GW, Jin K, Lu XB. Bis(oxazolinyl)phenyl-
ligated rare-earth-metal complexes: highly regioselective catalysts for
cis-1,4-polymerization of isoprene. Inorg Chem, 2013, 52: 2802–2808
31 Dunne JF, Fulton DB, Ellern A, Sadow AD. Concerted C−N and
C−H bond formation in a magnesium-catalyzed hydroamination. J
Am Chem Soc, 2010, 132: 17680–17683
40 Zhang LJ, Wang SW, Sheng EH, Zhou SL. A solvent-free synthesis
of α,α′-bis(substituted benzylidene) cycloalkanones catalyzed by lan-
thanide amides [(Me3Si)2N]3Ln(-Cl)Li(THF)3 under microwave ir-
radiation. Green Chem, 2005, 7: 683–686
41 Zhang LJ, Wang SW, Zhou SL, Yang GS, Sheng EH. Cannizzaro-
type disproportionation of aromatic aldehydes to amides and alcohols
by using either a stoichiometric amount or a catalytic amount of lan-
thanide compounds. J Org Chem, 2006, 71: 3149–3153
42 Zhou SL, Wang SW, Yang GS, Li QH, Zhang LJ, Yao ZJ, Zhou ZK,
Song HB. Synthesis, structure, and diverse catalytic activities of
[ethylenebis(indenyl)]lanthanide(III) amides on N−H and C−H
addition to carbodiimides and -caprolactone polymerization.
Organometallics, 2007, 26: 3755–3761
43 Li QH, Wang SW, Zhou SL, Yang GS, Zhu XC, Liu YY. Highly
atom efficient guanylation of both aromatic and secondary amines
catalyzed by simple lanthanide amides. J Org Chem, 2007, 72:
6763–6767
44 Casely IJ, Ziller JW, Evans WJ. C–H activation via carbodiimide in-
sertion into yttrium-carbon alkynide bonds: an organometallic alder-
ene reaction. Organometallics, 2011, 30: 4873-4881
45 Dubé T, Conoci S, Gambarotta S, Yap GPA, Vasapollo G. Stick-
stoffixierung: reduktion von N2 durch vier metallfragmente unter
bildung eines vierkernigen Samarium-Distickstoffkomplexes. Angew
Chem, 1999, 111: 3890–3892
46 Ganesan M, Gambarotta S, Yap GPA. Highly reactive SmII macrocy-
clic clusters: precursors to N2 reduction. Angew Chem Int Ed, 2001,
40: 766–769
47 Yang Y, Cui DM, Chen XS. The behavior of pyrrolyl ligands within
the rare-earth metal alkyl complexes. Insertion of C=N and C=O
double bonds into Ln--C bonds. Dalton Trans, 2010, 39: 3959–3967
48 Zhou SL, Wu SH, Zhu H, Wang SW, Zhu XC, Zhang LJ, Yang GS,
Cui DH, Wang HY. Synthesis, structure and catalytic activity of al-
kali metal-free bent-sandwiched lanthanide amido complexes with
calix[4]-pyrrolyl ligands. Dalton Trans, 2011, 40: 9447–9553
49 Liu C, Zhou SL, Wang SW, Zhang LJ, Yang GS. Rare earth metal
bis(trimethylsilyl)amido complexes bearing pyrrolyl-methylamide
ligand. Synthesis, structure, and catalytic activity towards guany-
lation of amines. Dalton Trans, 2010, 39: 8994–8999
50 Zhu XC, Zhou SL, Wang SW, Wei Y, Zhang LJ, Wang FH, Wang
SY, Feng ZJ. Rare-earth metal complexes having an unusual indolyl-
1,2-dianion through C–H activation with a novel 1:(2–1:1) bond-
ing with metals. Chem Commun, 2012, 48: 12020–12022
32 Reznichenko AL, Hultzsch KC. C1-symmetric rare-earth-metal ami-
nodiolate complexes for intra- and intermolecular asymmetric hy-
droamination of alkenes. Organometallics, 2013, 32: 1394–1408
33 Roux EL, Liang YC, Storz MP, Anwander R. Intramolecular hy-
51 Zhu XC, Wang SW, Zhou SL, Wei Y, Zhang LJ, Wang FH, Feng ZJ,
Guo LP, Mu XL. Lanthanide amido complexes incorporating amino-
droamination/cyclization
Ln[N(SiMe3)2]3 grafted onto periodic mesoporous silicas. J Am Chem
of
aminoalkenes
catalyzed
by

Yang S, et al. Sci China Chem August (2014) Vol.57 No.8
1097
coordinate-lithium bridged bis(indolyl) ligands: synthesis, character-
ization, and catalysis for hydrophosphonylation of aldehydes and al-
dimines. Inorg Chem, 2012, 51: 7134–7143
= Nd, Sm, Eu). Polyhedron, 2003, 22: 1019–1024
54 Xie MH, Liu XY, Liu L, Wu YY, Wang, SW, Zhou SL, Sheng EH,
Yang GS, Huang ZX. Synthesis, structure and catalytic activity
comparison of tris-and tetracoordinated lanthanide amides. Chin J
Chem, 2004, 22: 678–682
55 Sheldrick GM. SADABS: program for empirical absorption correc-
tion of area detector data. Göttingen: University of Göttingen, 1996
56 Sheldrick GM. SHELXTL 5.10 for Windows NT: structure determi-
nation software programs. Madison: Bruker Analytical X-ray Sys-
tems, Inc., 1997
52 Feng ZJ, Zhu XC, Wang SY, Wang SW, Zhou SL, Wei Y, Zhang GC,
Deng BJ, Mu XL. Synthesis, structure, and reactivity of lanthanide
complexes incorporating indolyl ligands in novel hapticities. Inorg
Chem, 2013, 52: 9549–9556
53 Zhou SL, Wang SW, Yang GS, Liu XY, Sheng EH, Zhang KH,
Cheng L, Huang ZX. Synthesis, structure, and catalytic activity of
tetracoordinate lanthanide amides [(Me3Si)2N]3Ln(µ-Cl)Li(THF)3 (Ln
ZHU XianCui received a BSc degree from Anhui University in 1998, MSc and PhD degrees from
Anhui Normal University in 2008 and 2012, respectively. She worked in Wuhu Teachers College
from 1998, and then joined the faculty of Anhui Normal University in 2005. Her research interests
cover the synthesis and application of organolanthanide complexes.
WANG ShaoWu received his BSc and MS degrees from Anhui Normal University in 1985 and
1992, respectively. After obtaining a PhD from The Chinese University of Hong Kong in 1999, he
spent one year as a postdoctoral fellow at The Chinese University of Hong Kong (supervisor: Pro-
fessor Zuowei Xie). He then joined the faculty of the Anhui Normal University as a full professor of
chemistry. He serves as the vice-president of the Anhui Normal University since June 2009, and has
co-authored about 110 publications in peer-reviewed journals, 5 patents, and received two 2nd prize
awards from the State Commission of Education and Anhui Province. His research interests include
organolanthanide chemistry and organic synthesis.