Syntheses, structures and catalytic activities of low-coordinated rare-earth metal complexes containing 2,2′-pyridylpyrrolides

Article abstract of DOI:10.1002/aoc.5275

Reactions of the ligand precursors 2-(2′-pyridyl)-3,5-Me₂-pyrrole (L¹H) and 2-(2-pyridyl)-3,4,5-Me₃-pyrrole (L²H) with [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ in toluene afforded a series of low-coordinated rare-earth metal bis-amido complexes L¹RE[N(SiMe₃)₂]₂ [RE = Y (1a), Dy (1b), Er (1c), Yb (1d)] and L²RE[N(SiMe₃)₂]₂ [RE = Y (2a), Dy (2b), Er (2c), Yb (2d)]. With the ionic radius of rare-earth metal increasing, the reaction of L¹H and [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ gave dinuclear complexes (L¹)₂RE(μ-Cl)(μ-η⁵:η¹:η¹-L¹)RE(L¹)[N(SiMe₃)₂]₂ [RE = Sm (1e), Pr (1f)]; however, the reaction of L²H and [(Me₃Si)₂N]₃Sm(μ-Cl)Li(THF)₃ afforded (L²)₂Sm[N(SiMe₃)₂]₂ (2e). Results indicated that the ionic radius of rare-earth metal and subtle change in the ligands have substantial effects on the structure and bonding mode of complexes. The complexes showed a high catalytic activity for the ring-opening reaction of cyclohexene oxide with amines to afford various β-aminoalcohols under mild solvent-free conditions.

Full text of DOI:10.1002/aoc.5275

Received: 2 August 2019
DOI: 10.1002/aoc.5275
Revised: 9 September 2019
Accepted: 11 September 2019
F U L L P A P E R
Syntheses, structures and catalytic activities of low‐
coordinated rare‐earth metal complexes containing 2,2′‐
pyridylpyrrolides
Jun Du1 | Shuangliu Zhou1
| Xiuli Zhang1 | Lijun Zhang1 | Peng Cui1 |
Zeming Huang1 | Yun Wei1 | Xiancui Zhu1 | Shaowu Wang1,2
1 Laboratory of Functionalized Molecular
Reactions of the ligand precursors 2‐(2′‐pyridyl)‐3,5‐Me2‐pyrrole (L1H) and
Solids, Ministry of Education, Anhui
Laboratory of Molecule‐based Materials,
College of Chemistry and Materials
Science, Anhui Normal University, Wuhu,
China
2 State Key Laboratory of Organometallic
Chemistry, Shanghai Institute of Organic
Chemistry, Shanghai, China
2‐(2‐pyridyl)‐3,4,5‐Me3‐pyrrole (L2H) with [(Me3Si)2N]3RE(μ‐Cl)Li(THF)3 in
toluene afforded a series of low‐coordinated rare‐earth metal bis‐amido
complexes L1RE[N(SiMe3)2]2 [RE = Y (1a), Dy (1b), Er (1c), Yb (1d)] and
L2RE[N(SiMe3)2]2 [RE = Y (2a), Dy (2b), Er (2c), Yb (2d)]. With the ionic
radius of rare‐earth metal increasing, the reaction of L1H and
[(Me3Si)2N]3RE(μ‐Cl)Li(THF)3 gave dinuclear complexes (L1)2RE(μ‐Cl)(μ‐η5:-
η1:η1‐L1)RE(L1)[N(SiMe3)2]2 [RE = Sm (1e), Pr (1f)]; however, the reaction of
L2H and [(Me3Si)2N]3Sm(μ‐Cl)Li(THF)3 afforded (L2)2Sm[N(SiMe3)2]2 (2e).
Results indicated that the ionic radius of rare‐earth metal and subtle change
in the ligands have substantial effects on the structure and bonding mode of
complexes. The complexes showed a high catalytic activity for the ring‐
opening reaction of cyclohexene oxide with amines to afford various
β‐aminoalcohols under mild solvent‐free conditions.
Correspondence
Shuangliu Zhou, Peng Cui, and Shaowu
Wang, Laboratory of Functionalized
Molecular Solids, Ministry of Education,
Anhui Laboratory of Molecule‐based
Materials, College of Chemistry and
Materials Science, Anhui Normal
University, Wuhu, Anhui 241000, China.
Email: slzhou@ahnu.edu.cn; pcui@ahnu.
edu.cn; swwang@ahnu.edu.cn
KEYWORDS
Funding information
2,2'‐pyridylpyrrolide, catalysis, rare‐earth metal complex, X‐ray analysis
Anhui Normal University; National Natu-
ral Science Foundation of China, Grant/
Award Number: 21672009, 21602004,
21702004 and 21861162009
1 | INTRODUCTION
binding properties of 2‐(2′‐pyridyl)pyrroles in a 1,4‐
relationship,[3] which is similar to the α‐diimine ligands,
Pyrrole and its derivatives have been widely used in rare‐
earth organometallic chemistry, exhibiting increased
reactivity toward electrophiles owing to their π‐electron
excessive properties.[1] However, pyridine is π‐electron
deficient but exhibits Lewis basicity because of its avail-
able lone‐pair electrons. Owing to the complementary
properties of pyridine and pyrrole, pyridylpyrrolide
ligands can potentially generate push/pull interaction
between the pyridyl and pyrrolide halves to exhibit the
intramolecular excited‐state proton transfer.[2] In particu-
lar, there has been significant interest in the metal‐
such as 2,2′‐bipyridine. Additionally, 2‐(2′‐pyridyl)pyr-
roles can coordinate to metal, forming a five‐membered
chelate metallacycle, which is typical for many stable
photoactive molecular materials.[4] Although various
2,2′‐pyridylpyrrolide metal complexes for late transition
metals have been reported to exhibit rich redox
chemistry[5] and photoluminescent properties,[6] only a
few reports are available for early transition metals.[7] It
has been reported that the titanium complex bearing
2,2′‐pyridylpyrrolyl ligand could highly catalyze the
multicomponent coupling of alkynes, isonitriles and
Appl Organometal Chem. 2019;e5275.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5275

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DU ET AL.
monosubstituted hydrazines to generate substituted
pyrazoles.[7a] Recently, the group 4 metal complexes bear-
ing 2,2′‐pyridylpyrrolyl ligands were reported to exhibit
photoluminescence in solution and facilitate photoredox
processes as a photosensitizer.[7b–d] However, the rare‐
earth metal complexes containing 2,2′‐pyridylpyrrolyl
ligands remain unexplored. We herein report the synthe-
ses and structural characterizations of a series of
2,2′‐pyridylpyrrolyl ligand‐supported rare‐earth metal
complexes. The resulting bis‐amido complexes featured
relatively low coordination number and the catalytic
activities of all of the obtained complexes toward the
ring‐opening reaction of cyclohexene oxide with various
amines were studied
rare‐earth metals Sm and Pr were employed, the reaction
of [(Me3Si)2N]3RE(μ‐Cl)Li(THF)3 with 2 equiv. of L1H
afforded dinuclear complexes (L1)2RE(μ‐Cl)(μ‐η5:η1:η1‐
L1)RE(L1)[N(SiMe3)2]2 [RE = Sm (1e), Pr (1f)]; however,
the reaction of [(Me3Si)2N]3Sm(μ‐Cl)Li(THF)3 with
2 equiv. of L2H gave the mononuclear amido complex
(L2)2Sm[N(SiMe3)2] (2e) (Scheme 1). These results
suggest that the structures and bonding modes of the
complexes are largely affected by the ionic radius of
rare‐earth metal; however, a slight variation of the ligand
by addition of a methyl group on the 4‐position of the
pyrrole backbone also subtly affects the resulting
complexes, as in the case of 1e and 2e. These complexes
are extremely sensitive to air and moisture, and they are
soluble in THF, toluene and n‐hexane. All of the com-
plexes were fully characterized by NMR spectroscopic
methods (for 1a and 2a), elemental analyses and X‐ray
crystallographic analyses.
2 | RESULTS AND DISCUSSION
X‐ray diffraction analyses revealed that complexes
1a–1d were isostructural tetra‐coordinated rare‐earth
metal bis‐amido complexes adopting distorted tetrahedral
geometries, and a representative structure diagram of
complex 1c is shown in Figure 1. Compounds 1e and 1f
were dinuclear complexes with two metal centers bridged
by one μ‐Cl ligand and one pyrrolide moiety in a μ‐η5:η1:-
η1 mode, and only one amido group coordinated to the
metal center with the μ‐η5 bridged pyrrolide. The repre-
sentative structure diagram of complex 1e is shown in
Figure 2. X‐ray diffraction analyses revealed that
2.1 | Syntheses and characterization of
rare‐earth metal complexes containing
2,2′‐pyridylpyrrolyl ligands
The reaction of 2‐(2'‐pyridyl)‐3,5‐Me2‐pyrrole (L1H) and
2‐(2'‐pyridyl)‐3,4,5‐Me3‐pyrrole (L2H) with 1 equiv. of
[(Me3Si)2N]3RE(μ‐Cl)Li(THF)3 in toluene afforded a
series of low‐coordinated rare‐earth metal bis‐amido com-
plexes L1RE[N(SiMe3)2]2 [RE = Y (1a), Dy (1b), Er (1c),
Yb (1d)] and L2RE[N(SiMe3)2]2 [RE = Y (2a), Dy (2b),
Er (2c), Yb (2d)], respectively (Scheme 1). When the light
SCHEME 1 Syntheses of rare‐earth
metal complexes

DU ET AL.
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FIGURE 1 Representative molecular
structure of complex 1c. Hydrogen atoms
are omitted for clarity.
FIGURE 2 Representative molecular structure of complex 1e. Hydrogen atoms are omitted for clarity.
complexes 2a–2d were also isostructural with distorted
tetrahedral geometries, and a representative structure
diagram of complex 2c is shown in Figure 3. The mono‐
amido complex 2e adopted a penta‐coordinated square‐
based pyramidal configuration, and the structure diagram
is shown in Figure 4. The selected bond distances and
angles are listed in Tables 1–3.
As shown in Tables 1–3, the average RE(1)–Nav bond
distances in complexes 1a–1d are comparable with those
in complexes 2a–2d, and both series are also consistent
with the trend in ionic radius of the corresponding rare‐
earth metals. The RE(1)–N(2) bond lengths in complexes
1a–1d and 2a–2d were slightly longer than those of
RE(1)–N(1), N(3) and N(4), as expected, as the donation

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DU ET AL.
FIGURE 3 Representative molecular
structure of complex 2c. Hydrogen atoms
are omitted for clarity.
FIGURE 4 Molecular structure of
complex 2e. Hydrogen atoms are omitted
for clarity.
from the neutral pyridine donor is weaker than those
from the anionic pyrrolide and amido donors in the
molecules. In the π coordinated pyrrolyl ring of 1e, the
bond distances between samarium ions with the five‐
membered pyrrolyl ring range from 2.760(5) to 2.967(5)
Å, with the average value of 2.858(5) Å, comparable with

DU ET AL.
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TABLE 1 Selected bond length (Å) and bond angle (deg) of
complexes 1a–1d
TABLE 3 Selected bond length (Å) and bond angle (deg) of
complexes 2a–2e
2a (Y) 2b (Dy) 2c (Er) 2d (Yb) 2e (Sm)
1a (Y)
1b (Dy)
1c (Er)
1d (Yb)
RE(1)–N(1)
RE(1)–N(2)
RE(1)–N(3)
RE(1)–N(4)
RE(1)–N(5)
RE(1)–Nav
2.266(7) 2.299(7) 2.263(10) 2.236(2) 2.390(8)
RE(1)–N(1)
2.282(8) 2.278(6)
2.422(7) 2.450(6)
2.200(7) 2.222(9)
2.260(6)
2.442(6)
2.195(6)
2.233(4)
2.398(4)
2.165(4)
2.176(4)
2.243(4)
71.67(15)
93.80(14)
2.440(4) 2.454(7) 2.420(6)
2.396(2) 2.501(8)
RE(1)–N(2)
2.195(6) 2.216(7) 2.196(10) 2.166(2) 2.369(7)
RE(1)–N(3)
2.204(7) 2.224(7) 2.203(9)
2.182(2) 2.481(7)
2.255(7)
RE(1)–N(4)
2.204(7) 2.228(10) 2.204(6)
2.277(8) 2.298(10) 2.275(6)
RE(1)–Nav
2.276(7) 2.298(7) 2.271(10) 2.245(2) 2.399(8)
N(1)–RE(1)–N(2)
N(2)–RE(1)–N(3)
70.4(3)
93.8(2)
70.0(3)
93.6(3)
70.9(2)
95.0(2)
N(1)–RE(1)–N(2) 70.4(2) 70.1(2) 71.3(3)
N(2)–RE(1)–N(3) 93.3(2) 93.3(3) 94.3(3)
71.85(8) 66.4(3)
93.85(8) 89.3(3)
N(3)–RE(1)–N(4) 116.8(2) 117.6(3)
N(4)–RE(1)–N(1) 106.4(3) 106.3(3)
115.9(2) 115.90(14)
106.1(2) 106.00(15)
N(3)–RE(1)–N(4) 117.4(3) 117.5(2) 116.1(4) 115.98(8) 67.4(2)
N(1)–RE(1)–N(4) 106.1(3) 99.5(2) 105.6(4) 106.09(8)
N(4)–RE(1)–N(5)
N(1)–RE(1)–N(5)
129.7(2)
109.4(3)
TABLE 2 Selected bond length (Å) and bond angle (deg) of
complexes 1e–1f
1e (Sm)
1f (Pr)
2.2 | Catalytic activity of rare‐earth metal
complexes containing 2,2'‐pyridylpyrroly
ligands.
RE(1)–N(1)
RE(1)–N(2)
RE(1)–N(3)
RE(1)–N(4)
RE(1)–N(5)
RE(1)–N(6)
RE(2)–C(23)
RE(2)–C(24)
RE(2)–C(25)
RE(2)–C(26)
RE(2)–N(5)
RE(2)–Pyrav
RE(2)–N(7)
RE(2)–N(8)
RE(2)–N(9)
RE(1)–Cl(1)
RE(2)–Cl(1)
2.384(4)
2.532(3)
2.415(3)
2.581(3)
2.487(3)
2.575(3)
2.760(5)
2.822(5)
2.967(5)
2.934(4)
2.806(3)
2.858(5)
2.376(4)
2.514(4)
2.279(3)
2.854(1)
2.804(1)
2.412(6)
2.573(8)
2.491(8)
2.641(8)
2.542(8)
2.672(8)
2.784(9)
2.876(9)
2.973(9)
2.878(9)
2.769(7)
2.874(9)
2.399(8)
2.602(8)
2.310(7)
2.913(2)
2.850(3)
The ring opening of epoxides with aromatic amines is an
important and well‐defined route for the synthesis of
β‐amino alcohols, which are versatile intermediates for
the synthesis of natural products and bioactive mole-
cules.[10] Various catalysts including metal triflates,[9,11]
metal halides,[12] metal alkoxides,[13] metal amides[14]
and other catalysts[15] are employed to achieve the prod-
ucts in high conversion and selectivity. However, these
catalytic systems usually require elevated temperature,
high pressure, stoichiometric amounts of catalyst and
long reaction times. Recently, a green method for the syn-
thesis of β‐aminoalcohols was developed using a reusable
catalyst or under solvent‐free and mild reaction condi-
tions.[16] Here, the rare‐earth metal amido complexes
containing 2,2′‐pyridylpyrrolyl ligands as catalysts for
the ring‐opening reaction of cyclohexene oxide with
amines were examined. The ring‐opening reaction of
cyclohexene oxide with aniline was initially investigated
as the template reaction in the presence of 1 mol% of
complex 1a (entries 1–5, Table 4). Under solvent‐free
conditions at room temperature, the reaction afforded
2‐phenylaminocyclohexanol 4a in a 95% yield (entry 5,
Table 4), which was identified as the trans isomer with
characteristic 1H NMR signals appearing at at 3.35
(ddd, J = 10.0, 9.5 and 4.5 Hz, 1H) for the CHOH and δ
3.14 (ddd, J = 11.0, 9.5 and 4.0 Hz, 1H) for the CHNH
protons.[11c,12b] Further examination of the different com-
plexes as catalysts showed that all of the complexes effec-
tively catalyzed the reactions (entries 7–16, Table 4).
Under optimized conditions, using 0.5 mol% of complex
N(1)–RE(1)–N(2)
N(3)–RE(1)–N(4)
N(5)–RE(1)–N(6)
N(7)–RE(2)–N(8)
67.45(13)
67.19(11)
64.36(11)
66.90(13)
65.2(3)
65.3(3)
62.6(3)
64.2(3)
that of 2.874(3)
Å
in calix[4]‐pyrrolyl complex
(η5:η1:η5:η1‐Me8‐calix[4]‐pyrrolyl){SmN(SiMe3)2}2,[8] but
slightly longer than those of 2.810 (3) and 2.796(4) Å in
{2‐[(2,6‐Me2C6H3)NCH2](C4H3N)SmN(SiMe3)2}2
{2‐[(2,4,6‐Me3C6H2)NCH2](C4H3N)SmN(SiMe3)2}2.[9]
[1l]
and

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DU ET AL.
TABLE 4 Optimization of the reaction conditiona
TABLE 5 Ring‐opening reaction of cyclohexene oxide with dif-
ferent aminesa
Loading
Entry Catalyst (mol%) Time (h) Solvent Yield (%)b
Entry
R1R2NH2
Product
4a
Yield (%)b
1
1a
1a
1a
1a
1a
—
1b
1c
1d
1e
1f
1
1
10
10
10
10
10
24
10
10
10
10
10
10
10
10
10
10
10
10
8
Toluene 70
THF 67
Hexane 53
1
91
2
2
3
4
5
4b
4c
4d
4e
82
91
91
70
3
1
4
1
PhCl
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
Free
65
95
Trace
91
90
92
94
93
89
91
87
90
87
90
78
92
92
91
79
5
1
6
—
1
7
8
1
9
1
10
11
12
13
14
15
16
17
18
19
20
21
22
1
6
7
4f
90
88
1
2a
2b
2c
2d
2e
1a
1a
1a
1a
1a
1a
1
4g
1
1
8
9
4h
4i
87
89
1
1
0.5
0.25
0.5
0.5
0.5
0.5
10
11
4j
84
91
6
4k
4
2
12
13
4l
58c
63c
aThe reaction was performed by treating 1 equiv. of amines with 2 equiv. of
epoxides under the given conditions.
4m
bIsolated yield.
14
4n
69c
1a under solvent‐free conditions in 4 h, the reaction of
cyclohexene oxide with aniline afforded the correspond-
ing ring‐opening product in a 91% yield (Entries 7–16,
Table 4).
15
16
4o
4p
97
98
Complex 1a was selected as the catalyst for the follow-
ing experiments to examine the ring‐opening reaction of
cyclohexene oxide with various amines, and results are
presented in Table 5. The results showed that high yields
were achieved under mild reaction condition (0.5 mol%
cat., solvent‐free at r.t.) for a wide range of different
amines. It was also found that both the electronic and
the steric properties of the substrates affected the reactiv-
ity. In the case of ortho‐substituted anilines, the ring‐
opened products were obtained in slightly lower yield
(entries 2, 5 and 10, Table 5). For aryl amines bearing a
strong electron‐withdrawing substituent such as NO2 or
17
18
4q
4r
93
91
19
4s
96
aReaction conditions: complex 1a (0.05 mol), amines (1.0 mmol), epoxides
(2.0 mmol), solvent‐free, room temperature.
bIsolated yields.
cToluene as solvent, 70°C, 4 h.

DU ET AL.
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CF3, the ring‐opened products 4l–4n were also obtained
in lower yields of 58–69%, even at 70°C (entries 12–14,
Table 5). The ring‐opened products 4o–4s were obtained
in satisfactory yields for the aliphatic primary and sec-
ondary amines (entries 15–19, Table 5). The probable
reaction mechanism was that the complexes functioned
as Lewis acid catalysts, the cyclohexene oxide was acti-
vated through the coordination of cyclohexene oxide oxy-
gen atom to the rare‐earth metal center, then amine as a
nucleophile attacked to afford the desired product.[12c, 17]
The low‐coordinated bis‐amido rare‐earth complexes
exhibited slightly high catalytic activity probably owing
to the steric effect around the rare‐earth metals.
L2H (0.19 g, 1.00 mmol), [(Me3Si)2N]3RE(μ‐Cl)Li(THF)3
(1.00 mmol) and toluene (30.0 ml) at room temperature.
The reaction mixture was stirred at 100°C for 12 h, and
the solvent was evaporated under reduced pressure. The
residue was extracted with n‐hexane (15.0 ml), and the
crystals were obtained by cooling the solution at 0°C for
several days.
4.2.1 | Complex 1a
1
Yellow crystals (0.49 g, 85% yield). M.p.: 167–169°C. H
NMR (500 MHz, C6D6): δ 7.90 (d, J = 5.5 Hz, 1H, ArH),
7.24 (d, J = 8.6 Hz, 1H, ArH), 6.91–6.88 (m, 1H, ArH),
6.18 (t, J = 6.5 Hz, 1H, ArH), 6.02 (s, 1H, pyrrole‐H),
2.57 (s, 3H, CH3), 2.25 (s, 3H, CH3), 0.26 (s, 36H, SiCH3).
13C{1H} NMR (125 MHz, C6D6): δ 157.0 (ArC), 146.2
(ArC), 141.7 (ArC), 139.3 (ArC), 131.5(ArC), 127.4
(pyrrole‐C), 119.9 (pyrrole‐C), 115.9 (pyrrole‐C), 115.7
(pyrrole‐C), 17.6 (CH3), 15.8 (CH3), 4.4 (SiCH3). Elemen-
tal analysis calcd (%) for C23H47N4Si4Y⋅0.3 hexane: C
49.23, H 8.59, N 9.19; found: C 49.11, H 8.78, N 9.42.
3 | CONCLUSIONS
In summary, a series of the rare‐earth metal complexes
bearing 2,2′‐pyridylpyrrolides have been synthesized and
characterized. The X‐ray diffraction studies showed that
the structure of the resulted complexes were affected by
the ionic radius of rare‐earth metal, and a subtle change
of ligand from L1H to L2H. The four coordinated
bis‐amido rare‐earth complexes exhibited high catalytic
activity for the ring‐opening reaction of cyclohexene
oxide with various aromatic and aliphatic amines, which
provided a facile synthesis of the β‐aminoalcohols under
mild solvent‐free conditions.
4.2.2 | Complex 1b
Yellow crystals (0.58 g, 88% yield). M.p.: 154–156°C. IR
(KBr pellets, cm−1): ν 1586 (s), 1555 (s), 1502 (s), 1461
(m), 1277 (s), 1149 (m), 1093 (s), 838 (s). Elemental anal-
ysis calcd (%) for C23H47N4Si4Dy⋅0.5 hexane: C 44.77, H
7.80, N 8.03; found: C 44.50, H 7.55, N 8.34.
4 | EXPERIMENTAL
4.1 | General remarks
4.2.3 | Complex 1c
All syntheses and manipulations of air‐ and moisture‐
sensitive materials were performed under dry argon and
oxygen‐free atmosphere using standard Schlenk tech-
niques or in a glovebox. Solvents were refluxed and dis-
tilled over sodium/benzophenone under argon prior to
Pink crystals (0.55 g, 83% yield). M.p.: 151–153°C. IR (KBr
pellets, cm−1): ν 1590 (s), 1559 (s), 1504 (s), 1456 (m),
1269 (s), 1183 (m), 1092 (s),846 (s). Elemental analysis
calcd (%) for C23H47N4Si4Er: C 41.90, H 7.19, N 8.50;
found: C 41.80, H 7.08, N 8.74.
use. Compounds L1H and L2H,[18] [(Me3Si)2N]3RE(μ‐Cl)
[19]
Li(THF)3
were prepared according to literature
methods. IR spectra were recorded on Shimadzu FTIR‐
4.2.4 | Complex 1d
1
8400S spectrometer. H NMR and 13C NMR spectra for
analyses of compounds were recorded on a Bruker
AV‐400 or 500 NMR spectrometer in C6D6 for lanthanide
complexes and in CDCl3 for organic compounds.
Red crystals (0.59 g, 89% yield). M.p.: 156–158°C. IR
(KBr pellets, cm−1): ν 1589 (s), 1559 (s), 1504 (s), 1456
(m), 1269 (s), 1183 (m), 1092 (s), 846 (s). Elemental anal-
ysis calcd (%) for C23H47N4Si4Yb⋅0.5 hexane: C 44.10, H
7.69, N 7.91; found: C 43.90, H 7.69, N 8.05.
4.2 | General synthesis of L1REN(SiMe3)2
and L2REN(SiMe3)2
4.2.5 | Complex 2a
Under an argon atmosphere, an oven‐dried 50.0 ml
Schlenk flask equipped with a magnetic stir bar was
charged with the compound L1H (0.17 g, 1.00 mmol) or
1
Yellow crystals (0.48 g, 80% yield). M.p.: 142–144°C. H
NMR (500 MHz, C6D6): δ 7.87 (d, J = 5.5 Hz, 1H, ArH),

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DU ET AL.
7.29 (d, J = 8.5 Hz, 1H, ArH), 6.92–6.88 (m, 1H, ArH),
6.17–6.14 (m, 1H, ArH), 2.53 (s, 3H, CH3), 2.17 (s, 3H,
CH3), 2.02 (s, 3H, CH3), 0.27 (s, 36H, SiCH3). 13C{1H}
NMR (125 MHz, C6D6): δ 156.9 (ArC), 146.2 (ArC),
139.4 (ArC), 139.2 (ArC), 130.8 (ArC), 125.4 (pyrrole‐C),
119.8 (pyrrole‐C), 119.6 (pyrrole‐C), 115.6 (pyrrole‐C),
15.9 (CH3), 13.6 (CH3), 10.0 (CH3), 4.4 (SiCH3). IR
(KBr pellets, cm−1): ν 1591 (s), 1517 (s), 1466 (s), 1272
(s), 1152 (s), 976 (s), 779 (s), 746 (s). Elemental analysis
calcd (%) for C24H49N4Si4Y⋅0.5 hexane: C 50.83, H 8.85,
N 8.78; found: C 50.30, H 8.81, N 9.10.
4.3.1 | Complex 1e
Yellow crystals (0.36 g, 61% yield). M.p.: 164–166°C. IR
(KBr pellets, cm−1): ν 1591 (s), 1560 (s), 1504 (s), 1463
(m), 1262 (s), 1149 (m), 1093 (s), 797 (s). Elemental anal-
ysis calcd (%) for C51H65ClN9Si2Sm2⋅hexane: C 53.38, H
6.21, N 9.83; found: C 53.19, H 5.51, N 10.18.
4.3.2 | Complex 1f
Yellow crystals (0.37 g, 63% yield). M.p.: 169–171°C. IR
(KBr pellets, cm−1): ν 1594 (s), 1558 (s), 1499 (s), 1466
(m), 1280 (s), 1154 (m), 1009 (s), 782 (s). Elemental anal-
ysis calcd (%) for C51H65ClN9Si2Pr2: C 52.02, H 5.56, N
10.71; found: C 52.17, H 5.94, N 10.72.
4.2.6 | Complex 2b
Yellow crystals (0.58 g, 87% yield). M.p.: 137–139°C. IR
(KBr pellets, cm−1): 1589 (s), 1513 (s), 1460 (s), 1269
(s),1150 (s), 932 (m), 782 (s), 736 (s). Elemental analysis
calcd (%) for C24H49N4Si4Dy: C 43.12, H 7.39, N 8.38;
found: C 43.44, H 7.47, N 8.34.
4.4 | Synthesis of L2SmN(SiMe3)2 (2e)
A similar method for preparation of complex 2e was used
for the treatment of L2H (0.19 g, 1.00 mmol),
[(Me3Si)2N]3Sm(μ‐Cl)Li(THF)3 (0.50 mmol) and toluene
(30.0 ml) at room temperature. Yellow crystals were
obtained upon cooling the solution at 0°C for several days
(0.22 g, 65% yield). M.p.: 137–139°C. IR (KBr pellets,
cm−1): 1594 (s), 1517 (s), 1468 (s), 1264 (s), 1149 (s), 930
(s), 785 (s), 739 (s). Elemental analysis calcd (%) for
C30H44N5Si2Sm: C 52.89, H 6.51, N 10.28; found: C
53.48, H 6.73, N 10.12.
4.2.7 | Complex 2c
Pink crystals (0.55 g, 82% yield). M.p.: 137–139°C. IR
(KBr pellets, cm−1): ν 1594 (s), 1514 (s), 1461 (s), 1274
(s), 1160 (s), 935 (s), 780 (s), 735 (s). Elemental analysis
calcd (%) for C24H49N4Si4Er⋅0.5 hexane: C 45.27, H 8.88,
N 7.82; found: C 45.02, H 8.02, N 7.90.
4.5 | X‐ray crystallography
Suitable crystals of complexes 1a–1f and 2a–2e were each
mounted in a sealed capillary. Diffraction was performed
on a Burker SMART CCD area detector diffractometer
using graphite‐monochromated Mo‐Kα radiation (λ =
0.71073 Å); an empirical absorption correction was
applied using the SADABS program. All structures were
solved by direct methods, completed by subsequent differ-
ence Fourier syntheses, refined anisotropically for all
nonhydrogen atoms by full‐matrix least‐squares calcula-
tions on F 2 using the SHELXTL program package. All
hydrogen atoms were refined using a riding model. See
Supporting Information for crystallographic parameters
and data collection and refinement information.
4.2.8 | Complex 2d
Red crystals (0.57 g, 84% yield). M.p.:139–141°C. IR
(KBr pellets, cm−1): ν 1591 (s), 1514 (s), 1463 (s), 1267
(s), 1154 (s), 932 (s), 774 (s), 734 (s). Elemental analysis
calcd (%) for C24H49N4Si4Yb⋅0.5 hexane: C 44.91, H 7.82,
N 7.76; found: C 44.63, H 7.78, N 8.05.
4.3 | General synthesis of 1e and 1f
Under an argon atmosphere, an oven‐dried 50.0 ml
Schlenk flask equipped with a magnetic stir bar was
charged with the compound L1H (0.17 g, 1.00 mmol),
[(Me3Si)2N]3RE(μ‐Cl)Li(THF)3 (0.50 mmol) and toluene
(30.0 ml) at room temperature. The reaction mixture
was stirred at 100°C for 12 h, and the solvent was evapo-
rated under reduced pressure. The residue was extracted
with n‐hexane (15.0 ml) and the crystals were obtained
by cooling the solution at 0°C for several days.
4.6 | General procedure for the ring
opening reaction of cyclohexene oxide with
amines
Under an argon atmosphere, an oven‐dried 20.0 ml
Schlenk flask equipped with a magnetic stir bar was

DU ET AL.
9 of 10
[3] a)C. L. Perry, J. H. Weber, J. Inorg. Nucl. Chem. 1971, 33, 1031.
b)B. Chiswell, Inorg. Chim. Acta 1972, 6, 629. c)Y. Chi, P.‐T.
Chou, Chem. Soc. Rev. 2007, 36, 1421. d)Y. Chi, P.‐T. Chou,
Chem. Soc. Rev. 2010, 39, 638. e)J. A. Flores, J. G. Andino, N.
P. Tsvetkov, M. Pink, R. J. Wolfe, A. R. Head, D. L.
Lichtenberger, J. Massa, K. G. Caulton, Inorg. Chem. 2011, 50,
8121.
charged with complex 1a (3.0 mg, 0.005 mmol) and the
amine (1.0 mmol). Cyclohexene oxide (0.202 ml, 2.0
mmol) was added and the resulting mixture was stirred
under solvent‐free conditions for 4 h. At completion, the
crude product was purified by column chromatography
on silica gel using ethyl acetate–petroleum ether
(1:5, v/v) as the eluent to afford the final product.
[4] a)A. T. Luedtke, K. I. Goldberg, Inorg. Chem. 2007, 46, 8496. b)
J.‐L. Chen, C.‐H. Lin, J.‐H. Chen, Y. Chi, Y.‐C. Chiu, P.‐T.
Chou, C.‐H. Lai, G.‐H. Lee, A. J. Carty, Inorg. Chem. 2008, 47,
5154. c)D. Pucci, I. Aiello, A. Aprea, A. Bellusci, A. Crispini,
M. Ghedini, Chem. Commun. 2009, 1550.
ACKNOWLEDGEMENTS
This work is supported by the National Natural Science
Foundation of China (21672004, 21602004, 21702004
and 21861162009) and the Special and Excellent Research
Fund of Anhui Normal University.
[5] a)K. Searles, M. Pink, K. G. Caulton, D. J. Mindiola, Dalton
Trans. 2012, 41, 9619. b)N. P. Tsvetkov, C.‐H. Chen, J. G.
Andino, R. L. Lord, M. Pink, R. W. Buell, K. G. Caulton, Inorg.
Chem. 2013, 52, 9511.
[6] a)S. F. Liu, Q. Wu, H. L. Schmider, H. Aziz, N. X. Hu, Z.
Popovic, S. Wang, J. Am. Chem. Soc. 2000, 122, 3671. b)P.‐I.
Shih, C.‐H. Chien, C.‐Y. Chuang, C.‐F. Shu, C.‐H. Yang, J.‐H.
Chen, Y. Chi, J. Mater. Chem. 2007, 17, 1692. c)J. L. McBee,
T. D. Tilley, Organometallics 2010, 29, 184. d)M. L. Clement,
K. A. Grice, A. T. Luedtke, W. Kaminsky, K. I. Goldberg, Chem.
– Eur. J. 2014, 20, 17287. e)Y.‐P. Wang, X.‐H. Hu, Y.‐F. Wang, J.
Pan, X.‐Y. Yi, Polyhedron 2015, 102, 782. f)H. Xu, J. B.
Diccianni, J. Katigbak, C. Hu, Y. Zhang, T. Diao, J. Am. Chem.
Soc. 2016, 138, 4779. g)J. A. Flores, J. G. Andino, R. L. Lord, R.
J. Wolfe, H. Park, M. Pink, J. Telser, K. G. Caulton, Eur. J.
Inorg. Chem. 2018, 4893.
CONFLICTS OF INTEREST
There are no conflicts of interest to declare.
ORCID
Shuangliu Zhou https://orcid.org/0000-0002-0103-294X
REFERENCES
[7] a)A. A. Dissanayake, A. L. Odom, Chem. Commun. 2012, 48,
440. b)Y. Zhang, T. S. Lee, J. L. Petersen, C. Milsmann,
J. Am. Chem. Soc. 2018, 140, 5934. c)Y. Zhang, N. G.
Akhmedov, J. L. Petersen, C. Milsmann, Chem. – Eur. J. 2019,
25, 3042. d)G. Li, M. Lamberti, M. Mazzeo, P. Pappalardo, C.
Pellecchia, J. Mol. Catal. a: Chem. 2013, 370, 28.
[1] a)T. Dubé, S. Conoci, S. Gambarotta, G. P. A. Yap, G.
Vasapollo, Angew. Chem. Int. Ed. 1999, 38, 3657. b)M. Ganesan,
S. Gambarotta, G. P. A. Yap, Angew. Chem. Int. Ed. 2001, 40,
766. c)Y. Yang, S. Li, D. Cui, X. Chen, X. Jing, Organometallics
2007, 26, 671. d)L. Xiang, Q. Wang, H. Song, G. Zi, Organome-
tallics 2007, 26, 5323. e)Q. Wang, L. Xiang, H. Song, G. Zi,
Inorg. Chem. 2008, 47, 4319. f)G. Zi, Q. Wang, L. Xiang, H.
Song, Dalton Trans. 2008, 5930. g)J. J. Hao, H. B. Song, C. M.
Cui, Organometallics 2009, 28, 3970. h)J. J. Hao, H. B. Song,
C. M. Cui, Organometallics 2009, 28, 3100. i)Y. Yang, D. Cui,
X. Chen, Dalton Trans. 2010, 39, 3959. j)S. Zhou, S. Wu, H.
Zhu, S. Wang, X. Zhu, L. Zhang, G. Yang, D. Cui, H. Wang,
Dalton Trans. 2011, 40, 9447. k)Q. Li, J. Rong, S. Wang, S.
Zhou, L. Zhang, X. Zhu, F. Wang, S. Yang, Y. Wei, Organome-
tallics 2011, 30, 992. l)S. Zhou, Z. Wu, J. Rong, S. Wang, G.
Yang, X. Zhu, L. Zhang, Chem. – Eur. J. 2012, 18, 2653. m)Q.
Li, S. Zhou, S. Wang, X. Zhu, L. Zhang, Z. Feng, L. Guo, F.
Wang, Y. Wei, Dalton Trans. 2013, 42, 2861. n)Z. Feng, Y.
Wei, S. Zhou, G. Zhang, X. Zhu, L. Guo, S. Wang, X. Mu,
Dalton Trans. 2015, 44, 20502. o)J. Li, J. Hao, C. Cui, Dalton
Trans. 2015, 44, 767. p)G. Zhang, B. Deng, S. Wang, Y. Wei,
S. Zhou, X. Zhu, Z. Huang, X. Mu, Dalton Trans. 2016, 45,
15445. q)W. Wang, X. Wang, S. Zhou, X. Xu, J. Du, L. Zhang,
X. Mu, Y. Wei, X. Zhu, S. Wang, Inorg. Chem. 2018, 57,
10390. r)X. Zhu, Y. Li, D. Guo, S. Wang, Y. Wei, S. Zhou,
Dalton Trans. 2018, 47, 3947.
[8] S. Zhou, H. Wang, J. Ping, S. Wang, L. Zhang, X. Zhu, Y. Wei,
F. Wang, Z. Feng, X. Gu, S. Yang, H. Miao, Organometallics
2012, 31, 1696.
[9] a)M. Chini, P. Crotti, L. Favero, F. Machhia, M. Pine‐schi,
Tetrahedron Lett. 1994, 35, 433. b)J. Auge, F. Leroy, Tetrahe-
dron Lett. 1996, 37, 7715. c)G. Sekar, V. K. Singh, J. Org.
Chem. 1999, 64, 287. d)J. S. Yadav, A. R. Reddy, A. V. Narsaiah,
B. V. S. Reddy, J. Mol. Catal. a: Chem. 2007, 261, 207.
[10] C. Liu, S. Zhou, S. Wang, L. Zhang, G. Yang, Dalton Trans.
2010, 39, 8994.
[11] a)D. J. Ager, I. Prakash, D. R. Schaad, Chem. Rev. 1996, 96, 835.
b)K. Mori, M. Sakakibara, K. Okada, Tetrahedron 1984, 40,
1767. c)A. Sekine, T. Ohshima, M. Shibasaki, Tetrahedron
2002, 58, 75. d)G. Li, H. T. Chang, K. B. Sharpless, Angew.
Chem. Int. Ed. 1996, 35, 45. e)E. J. Corey, F. Zhang, Angew.
Chem. Int. Ed. 1999, 38, 1931. f)S. Zhu, L. Meng, Q. Zhang, L.
Wei, Bioorg. Med. Chem. Lett. 2006, 16, 1854.
[12] a)J. Iqbal, A. Pandey, Tetrahedron Lett. 1990, 31, 575. b)A. K.
Chakraborti, A. Kondaskar, Tetrahedron Lett. 2003, 44, 8315.
c)B. Shivani, A. K. Pujala, J. Chakraborti, Org. Chem. 2007,
72, 3713.
[2] a)M. Kijak, Y. Nosenko, A. Singh, R. P. Thummel, J. Waluk,
J. Am. Chem. Soc. 2007, 129, 2738. b)P. J. Morgan, A. J.
Fleisher, V. Vaquero‐Vara, D. W. Pratt, R. P. Thummel, M.
Kijak, J. Waluk, J. Phys. Chem. Lett. 2011, 2, 2114.
[13] a)S. Sagava, H. Abe, Y. Hase, T. Inaba, J. Org. Chem. 1999, 64,
4962. b)S. Rampalli, S. S. Chaudhari, K. G. Akamanchi,

10 of 10
DU ET AL.
Synthesis 2000, 78. c)Y. Li, Y. Tan, E. Herdtwick, M. Cokoja, F.
[18] J. J. Klappa, A. E. Rich, K. McNeill, Org. Lett. 2002, 4, 435.
E. Kühn, Appl. Catal. a 2010, 384, 171.
[19] a)S. Zhou, S. Wang, G. Yang, X. Liu, E. Sheng, K. Zhang, L.
Cheng, Z. Huang, Polyhedron 2003, 22, 1019. b)E. Sheng, S.
Wang, G. Yang, S. Zhou, L. Cheng, K. Zhang, Z. Huang,
Organometallics 2003, 22, 684.
[14] a)L. E. Overman, L. A. Flippin, Tetrahedron Lett. 1981, 22, 196.
b)M. C. Carre, J. P. Houmounou, P. Caubere, Tetrahedron Lett.
1985, 26, 3107. c)Y. Yamamoto, N. Asao, M. Meguro, N.
Tsukade, H. Nemoto, N. Adayari, J. G. Wilson, H. Nakamura,
J. Chem. Soc., Chem. Commun. 1993, 1201. d)J. Cossy, V.
Bellosta, C. Hamoir, J.‐R. Desmurs, Tetrahedron Lett. 2002,
43, 7083.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
[15] a)G. H. Posner, D. Z. Roger, J. Am. Chem. Soc. 1977, 99, 8208.
b)M. D. Pujol, Y. Harrak, Tetrahedron Lett. 2002, 43, 819. c)
P.‐Q. Zhao, L.‐W. Xu, C.‐G. Xia, Synlett 2004, 846. d)A. K.
Chakraborti, S. Rudrawar, A. Kondaskar, Org. Biomol. Chem.
2004, 2, 1277. e)R. I. Kureshy, S. Singh, N. H. Khan, S. H. R.
Abdi, E. Suresh, R. V. Jasra, J. Mol. Catal. a: Chem. 2007, 264,
162. f)A. Najmodin, R. S. Mohammad, Org. Lett. 2005, 17, 3649.
How to cite this article: Du J, Zhou S, Zhang X,
et al. Syntheses, structures and catalytic activities of
low‐coordinated rare‐earth metal complexes
containing 2,2′‐pyridylpyrrolides. Appl
Organometal Chem. 2019;e5275. https://doi.org/
10.1002/aoc.5275
[16] a)K. Tanaka, S. Oda, M. Shiro, Chem. Commun. 2008, 820. b)S.
Roy, B. Banerjee, N. Salam, A. Bhaumik, S. M. Islam,
ChemCatChem 2015, 7, 2689. c)S. Roy, S. S. Piyali Bhanja, A.
Islam, S. M. I. Bhaumik, Chem. Commun. 2016, 52, 8171. d)
M. Karimi, T. Hajiashrafi, A. Heydari, T. A. Azhdari, Appl.
Organometal. Chem. 2017, 31, e3866.
[17] S. Yadav, S. Kumar, R. Gupta, Eur. J. Inorg. Chem. 2015, 5534.