Lithium complex of 2-amino-functionalized benzoylpyrrole: Synthesis, structure, and catalytic activity for the cyclotrimerization of isocyanates

Article abstract of DOI:10.1016/j.poly.2017.03.058

Lithium complex stabilised by 2-amino-functionalized benzoylpyrrole was synthesized, and its structural features were provided. The molecular structure shows a novel tetrameric cage structure, which includes a eight-membered (LiN)₄ ring and a e

Full text of DOI:10.1016/j.poly.2017.03.058

Accepted Manuscript
Lithium complex of 2-amino-functionalized benzoylpyrrole: Synthesis, struc-
ture, and catalytic activity for the cyclotrimerization of isocyanates
Zhiqiang Guo, Yakong Wang, Jihong Yang, Xuehong Wei
PII:
S0277-5387(17)30256-5
DOI:
http://dx.doi.org/10.1016/j.poly.2017.03.058
POLY 12573
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
16 February 2017
30 March 2017
30 March 2017
Please cite this article as: Z. Guo, Y. Wang, J. Yang, X. Wei, Lithium complex of 2-amino-functionalized
benzoylpyrrole: Synthesis, structure, and catalytic activity for the cyclotrimerization of isocyanates, Polyhedron
(
2017), doi: http://dx.doi.org/10.1016/j.poly.2017.03.058
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Lithium complex of 2-amino-functionalized benzoylpyrrole:
Synthesis, structure, and catalytic activity for the cyclotrimerization
of isocyanates
a*
Zhiqiang Guo, Yakong Wang, Jihong Yang, Xuehong Wei, *
b
b
a,b
a
Scientific Instrument Center, Shanxi University, Taiyuan, 030006, P. R. China
b
School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan,
030006, P. R. China
Abstract:
Lithium complex stabilised by 2-amino-functionalized benzoylpyrrole was
synthesized, and its structural features were provided. The molecular structure shows
a novel tetrameric cage structure, which includes a eight-membered (LiN)
4
ring and a
eight-membered (LiO) ring with the coordinating pyrrolyl ligands. It was proved to
4
an efficient catalyst for the cyclotrimerisation of isocyanates in good to excellent
yields under mild conditions.
Keywords: benzoylpyrrole, synthesis, cyclotrimerization, isocyanate.
1. Introduction
Due to stable six-cyclic structure without an active hydrogen atom, isocyanurates,
the typical isocyanate cyclotrimerized products, could enhance the physical properties
of polyurethanes, copolymer resins and coating materials [1], such as increased
thermal and chemical resistance, water-resistance, impact resistance, hydrolytic
stability, transparency, specific rigidity [2]. Because these products are of commercial
significance and are widely used in polymeric processes of industry, the
cyclotrimerization of isocyanate has been studied thoroughly and many new types of
catalysts have been developed to obtain the isocyanurates in quantitatively yields. For
example, traditional Lewis-basic catalysts including N-heterocyclic carbenes [3],

phosphines [4], amines [5], fluoride anions [6], p-toluenesulfinate [7] carbamate
anions [8] and alkoxyalkenes [9], metal catalysts including organozinc amines and
alkoxides [10], alkoxy niobium [11] and zirconium compounds [12], organotin (II)
3
and (IV) compounds [13] and Ti(bipyridyl) [14], copper and nickel halides [15], rare
earth metal amides [16], palladium (0) systems [17] and manganese (II) and iron(II)
diaryl complexes[18].
On the other hand, the chemistry and structural diversity of various metal
complexes incorporating pyrrole-based multifunctinal ligands have attracted
increasing attention. Such as alkylzinc complexes incorporating the corresponding
N,N-bifunctional ligand [19], N,O-didentate pyrrole-based ligand [20],
NNN-tridentate pyrrole-based ligand [21], pyrrole-based macrocyclic ligand [22] and
so on. Our previous studies also show that the substituted pyrroles are versatile
supporting proligands [23]. As a part of our ongoing interest in the development of
new reaction systems based on lithium complexes supported by multidentate
pyrrole-based ligands, herein we have focused on the versatile bonding modes of
monoanionic pyrrolate ligands, and demonstrated that lithium complex stabilised by
2
-amino-functionalized benzoylpyrrole is efficient precatalyst for the
cyclotrimerisation of isocyanates. It offers high activity, selectivity towards aryl
isocyanates, and high selectivity to the formation of isocyanurate products.
2. Experimental
2.1. General methods and materials
Unless otherwise noted, all syntheses and manipulations of air-sensitive materials
were performed under a purified nitrogen atmosphere using the standard Schlenk
techniques. Tetrahydrofuran and diethyl ether were distilled from
sodium-benzophenone under nitrogen. Hexane and toluene is dried using sodium
potassium alloy and distilled under nitrogen prior to use. All chemicals were
1
13
sublimed, recrystallized or distilled before use. H NMR (300 MHz), C NMR (75.5
7
MHz) and Li NMR (116.6 MHz) spectra of the compounds were recorded on a
Bruker DRX 300 instrument in CDCl or C D N at 298 K and referenced internally to
3
5
5
1
13
7
the residual solvent resonances ( H, C ) or externally ( Li). Elemental analyses were

performed on a Vario EL-III instrument. Melting points were determined on a
STUART SMP10 melting point apparatus and uncorrected. The IR spectra were
determined on a FTIR8400S IR spectrophotometer (SHIMADZU) by dispersing
samples in KBr disks.
2
.2. Synthesis of phenyl-(5-piperidin-1-ylmethyl-1H-pyrrol-2-yl)-methanone
LH)
The ligand was prepared by published procedures [19]. 83.4% yield, mp
(
1
1
02-103°C, H NMR (300MHz, CDCl
H, C ), 7.44-7.57 (m, 3H, C ), 6.79 (d, J = 3.3, 1H, C
N), 3.51 (s, 2H, CH ), 2.40 (s, 4H, C 10N), 1.55-1.60 (m, 4H, C
10N); C NMR (300MHz, CDCl ): δ (ppm) 25.1 (C 10N), 26.9 (C
10N), 56.9 (CH ), 110.8 (C N), 121.1(C N), 129.2 (C ), 129.8
), 131.3 (C ), 132.5 (C N), 139.1 (C ), 139.5 (C ), 185.2 (C=O).
IRνmax (KBr, cm ): 3249.8, 2935.5, 1612.4, 1573.8, 1496.7, 1407.9, 1338.5, 1230.5,
041.5, 983.6, 883.3, 811.9, 723.3, 698.2, 682.8. Anal. Calc. for C17 O: C, 76.09;
H, 7.51; N, 10.44. Found: C, 75.90; H, 7.38; N, 10.21.
.3. Synthesis of lithium complex (LLi)
3
): δ (ppm) 9.76 (br, 1H, NH), 7.87 (d, J = 6.9,
N), 6.12 (d, J = 3.0, 1H,
10N), 1.45 (s,
2
6
H
5
6
H
5
4 2
H
C
4
H
2
2
5
H
5
H
1
3
2
H, C
5
H
3
5
H
5
H10N),
55.6 (C
5
H
2
4
H
2
4
H
2
6
H
5
(
C
6
H
5
6
H
5
4
H
2
6
H
5
6
H
5
-1
1
20 2
H N
2
An n-BuLi hexane solution (3.0 mmol, 2.2 M) was added dropwise to a hexane
o
(
20 mL) solution of LH (g, 3.0 mmol) at 0 C under nitrogen. After the reaction
mixture was stirred at room temperature for 3 h. The white solid was isolated by
filtration and recrystallized from a saturated hexane/Et
2
O solution to yield colorless
), 7.42 (m, 3H,
-), 2.44 (m, 4H,
10N); C NMR (75MHz, C N):
), 138.99 (C ), 128.60 (C N),
-), 53.48 (C
N): δ(ppm) 0.71. Anal.
1
crystals of 1. H NMR (300MHz, C
5
D
5
N): δ(ppm) 8.23 (m, 2H, C
N), 6368 (d, 1H, C N), 3.73 (s, 2H, -CH
10N), 1.31 (m, 4H, C
N), 140.38 (C
6 5
H
C
6
5
H
5
), 7.35 (d, 1H, C
4
H
2
4
H
2
2
1
3
C
H
10N), 1.45 (m, 4H, C
5
H
5
H
5 5
D
δ(ppm) 184.86 (CO), 149.62 (C
4
H
2
6
H
5
6
H
5
4
H
2
1
27.99 (C
6
H
5
), 126.58 (C
6
H
5
), 112.12 (C
4
H
2
N), 59.816 (-CH
2
5
H10N),
7
2
4.77 (C
5
H
10N), 23.21 (C
5
H
10N); Li NMR (116.6 MHz, C
5
D
5
4 8 4
Calc. for C71H83Li N O : C, 74.79; H, 7.34; N, 9.83. Found: C, 75.20; H, 7.38; N,
10.01.
2.4. X-ray crystallography

Reflection intensity data for compounds were collected on a Bruker Smart Apex
CCD diffractometer using monochromated Mo Kα radiation, λ = 0.71073 Å. Each
2
structure was solved by direct method and refined on F by full matrix least squares
(
SHELX97) [24] using all unique data. Then the remaining non-hydrogen atoms were
obtained from the successive difference Fourier map. All non-hydrogen atoms were
refined with anisotropic displacement parameters, whereas the hydrogen atoms were
constrained to parent sites, using a riding mode (SHELXTL) [25]. Crystal and
structure refinement data are shown in Table 1. Selected bond lengths and bond angles
are ruled out in Table 2.
Table 1 Crystal data and structure refinement details of and ligand its complexes.
Ligand
Lithium complex
Empirical formula
Formula weight
Crystal system
Space group
a/Å
C
17
H
20
N
2
O
71 4 8 4
C H83Li N O
268.35
1140.21
Triclinic
P-1
Monoclinic
C2/c
25.743(4)
6.1040(8)
20.136(3)
90.00
12.206(3)
12.637(3)
21.775(5)
83.740(5)
88.999(4)
77.255(4)
b/Å
c/Å
o
α ( )
o
β ( )
107.317(2)
90.00
o
γ ( )
3
Volume (Å ), Z
3020.6(7), 8
1.18
3256.2(13), 2
1.163
-3
ρcalc/g cm
-1
µ/mm
0.074
0.072
F(000)
1152
1218
o
θ range/
2.12-25.05
8034
0.94 to 25.05
14330
Reflections collected
Independent reflections
2637 [R(int) = 0.0279]
11534 [R(int) = 0.0252]

Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2s (I)]
R indices (all data)
2673 / 0 / 182
11534 / 0 / 785
1.016
1.010
R1 = 0.0404, wR2= 0.0982
R1 = 0.0584, wR2= 0.1080
R1 = 0.0526, wR2 = 0.1209
R1 = 0.1167, wR2 = 0.1571
o
Table 2 Selected bond lengths (Å) and angles ( ) for complexes
Ligand
N1-C4
N1-C1
N2-C5
N2-C10
N2-C6
O1-C11
C1-C2
C3-C4
C4-C5
1.352(18)
1.372(19)
1.458(2)
1.457(2)
1.459(2)
1.234(17)
1.385(2)
1.377(2)
1.491(2)
C4-N1-C1
C5-N2-C10
C5-N2-C6
C10-N2-C6
N1-C1-C11
N1-C4-C5
N2-C5-C4
O1-C11-C1
O1-C11-C12
C1-C11-C12
110.34(13)
109.87(13)
111.31(13)
110.78(14)
121.37(13)
122.09(15)
112.92(14)
121.36(14)
119.70(13)
118.91(13)
Lithium complex
Li1-O4
1.957(4)
2.096(4)
2.245(5)
2.251(5)
2.263(5)
1.338(3)
1.394(3)
1.458(3)
1.471(3)
O4-Li1-N5
O4-Li1-O1
O1-Li1-N5
O4-Li1-N1
O1-Li1-N1
N5-Li1-N1
O4-Li1-N6
O1-Li1-N6
N5-Li1-N6
94.95(19)
137.2(2)
83.86(17)
88.49(19)
77.85(16)
156.3(2)
123.2(2)
99.28(18)
83.39(17)
Li1-O1
Li1-N5
Li1-N1
Li1-N6
N1-C4
N1-C1
N2-C6
N2-C5

O1-C11
C1-C2
C2-C3
1.267(3)
1.407(3)
1.376(4)
N1-Li1-N6
N1-Li4-N2
Li4-N1-Li1
114.15(19)
84.25(17)
81.12(18)
3
3
3
. Results and discussion
.1. Crystal structures
.1.1. Crystal structure of LH
Fig. 1 (a) The ORTEP view of LH at the 25% probability level with hydrogen atoms
omitted for clarity. (b) The Npyrrole-H···O hydrogen bridges of HL.
The single crystals of LH suitable for X-ray diffraction studies were obtained by
recrystallization from a saturated THF/hexane solution at room temperature, and the
ORTEP drawing is presented in Fig. 1(a), along with selected bond lengths and angles
Table 2. The crystal structure of HL reveals an intermolecular Npyrrole-H-O hydrogen
bond using oxygen atom of the carboxyl group as the hydrogen-bonding receptor, the
pyrrole rings are well-established as hydrogen-bonding donors and are largely
employed for anion bonding. The N-H-O bonds [H(N)-O(1) = 2.045 Å, N(1)-H-O(1)

=
158.06] responsible for the crystal packing of the ligand compound.
3.1.2. Crystal structure of LLi
(
a)
(
b)
(c)
Fig. 2 (a) The ORTEP view of LLi at the 25% probability level with hydrogen atoms
and solvent omitted for clarity. (b) Alternative views showing the core structure of
LLi.
Lithium complex stabilised by 2-amino-functionalized benzoylpyrrole (LLi)
were crystallized from a saturated Et
2
O/hexane solution, as illustrated in Fig. 2a. In
the solid state, it is a novel tetrameric cage structure, which includes a

eight-membered (LiN)
4
ring and a eight-membered (LiO)
4
ring with the coordinating
ring
pyrrolyl ligands. Different from the common tetrameric eight-membered (LiN)
4
motifs of lithium amides [26], all three donor atoms of the O,N,N-ligand coordinate to
a lithium and each sodium is coordinated by three nitrogen and two bridging oxygen
atoms. The eight-membered (LiO)
4
ring exhibits an interesting V-shaped (Fig. 2b).
o
The Li-O-Li bond angle range is between 84.37(17) and 88.55(18) and the Li-O bond
lengths range from 1.951(5) to 2.249(5) Å, which fall within the normal range found
in lithium oxide compounds. In addition, the Li-N distances within eight-membered
(
LiN)
4
ring range from 2.078(4) to 2.251(5) Å. The Li-N-Li bond angles fall in the
o
range of 79.93(17) - 81.12(18) , which are much smaller than those in (LiO)
4
ring.
3.2 lithium complex (LLi) catalyzed cyclotrimerization of isocyanates
Although cyclotrimerization of isocyanates have been studied by us utilizing
different type pyrrolyl lithium complexes as catalysts. [23e, 23f] For exploiting new
reaction systems based on lithium complexes supported by multidentate pyrrole-based
ligands, the above lithium complex stabilised by 2-amino-functionalized
benzoylpyrrole as catalysts for cyclotrimerization reactions were studied, and the
results are listed in Table 3. The reaction can work well producing the isocyanurate
product by carrying out the reaction in different solvents at room temperature for 0.5
h in the presence of 1 mol% of the above lithium complex as the catalyst (Table 3,
entries 1-5), indicating the solvent compatibility of the catalysts though the best result
was obtained when diethyl ether was employed as solvent. Pleasingly, the title
complex can promoted this reaction almost quantitatively at the 0.1 to 1.0 mol%
loadings (Table 3, entries 6-9). It is worth noting that the cyclotrimerization reaction
also can afford 98% isolated yield after 3h when the loading of catalyst is decreased
to 0.05% (Table 3, entry 10). Under the optimized reactions, the representative
isocyanates, 4-chloro, 4-methyl and 4-methoxyphenyl isocyanate, were also examined
using above lithium complex as a catalyst at 0.05 mol % loading (Table 3, entries
11-13). These results were comparable with those obtained by using the bidentate
pyrrolyl lithium complexes [Li{C N(CH NHCMe )-2} Li(THF) and
4
H
3
2
3
2
2
]

[
2 4 3 2 2 2
Li(OEt ){C H N(CH NMe )-2}] [23e] as catalysts. A proposed mechanism for the
cyclotrimerization of isocyanates catalyzed by this complex would be similar to the
reaction catalyzed by Lewis base [23e].
a
Table 3. Lithium complex catalyzed cyclotrimerization of isocyanates
R
O
N
O
O
Cat.
R
N C O
Solvent, r.t.
N
N
R
R
Catalyst loading
Yield
Isocyanates
Entry
Solvent
b
(
mol %)
1.0
(%)
0
.5
.5
.5
.5
.5
.5
.5
.5
1
2
3
4
5
6
7
8
9
Et
2
O
>99
90
93
99
99
99
99
97
99
98
95
97
96
0
0
0
0
0
0
0
1.0
1.0
THF
Hexane
Toluene
None
1.0
1.0
0.5
Et
Et
Et
Et
Et
Et
Et
Et
2
2
2
2
2
2
2
2
O
O
O
O
O
O
O
O
0.25
0.1
3
0.1
3
3
3
3
1
1
1
0
1
2
3
0.05
0.05
0.05
0.05
1
a
b
Reaction conditions: isocyanate (30 mmol), room temperature, Isolated yield

4. Conclusions
In summary, a new lithium complex stabilised by 2-amino-functionalized
benzoylpyrrole was synthesized and characterised. The X-ray diffraction analyses of
the complex indicated that it is a novel tetrameric cage structure, which includes a
4 4
eight-membered (LiN) ring and a eight-membered (LiO) ring with the coordinating
pyrrolyl ligands. The results demonstrated that the title complex has good
compatibility for cyclotrimerisation of various aryl isocyanate in different solvents,
and it is an efficient precatalyst for the cyclotrimerisation of isocyanates.
Acknowledgements
Financial supports from the National Natural Science Foundation of China (No.
20572065), the Coal-based Key Scientific and Technological Project (No.
MH2014-07), the Special Fund for Agro-scientific Research in the Public Interest (No.
2
01303106) and the Natural Science Foundation of Shanxi Province (No.
011021011-1, 2014011049-26) are gratefully acknowledged.
2
Appendix A. Supplementary data
CCDC (1530934 and 1530935) contains the supplementary crystallographic data
for LH and LLi, respectively. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html,
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
or
from
the
Cambridge
1
References
[
1] a) I.S. Lin, J.E. Kresta, K.C. Frisch, Reaction Injection Molding and Fast
Polymerization Reactions; Plenum Publishing: New York, 1982, p147;
b) Z. Wirpsza, Polyurethanes: Chemistry, Technology and Application, Ellis
Horwood: London, 1993.

[
2] a) T.S. Leu, J. Appl. Polym. Sci., 102 (2006) 2470;
b) G.Q. Xiao, S.Q. Gao, X.L. Xie, M.C. Xu, Polym. Adv. Technol., 20 (2009)
1157;
c) W. Sun, X. Yan, X. Zhu, J. Appl. Polym. Sci., 122 (2011) 2359;
d) M.H. Sun, X.M. Zhang, W.X. Chen, L.F. Feng, J. Appl. Polym. Sci., 133 (2016)
43327.
[
[
3] H.A. Duong, M.J. Cross, J. Louie, Org. Lett., 6 (2004) 4679.
4] a) J. Tang, T. Mohan, J.G. Verkade, J. Org. Chem., 59 (1994) 4931;
b) J. Tang, J.G. Verkade, Angew. Chem., Int. Ed. Engl., 32 (1993) 896;
c) X. Liu, Y. Bai, J.G. Verkade, J. Organomet. Chem., 582 (1999) 16;
d) S.M. Raders, J.G. Verkade, J. Org. Chem., 75 (2010) 5308.
[
5] a) Y. Tagachi, I. Shibaya, Y. Yasumoto, K. Ynoemoto, Bull. Chem. Soc. Jpn., 63
(
1990) 3486;
b) F.M. Moghaddam, M.G. Dekamin, G.R. Koozehgari, Lett. Org. Chem., 2
2005) 734.
(
[
[
6] Y. Nambu, T. Endo, J. Org. Chem., 58 (1993) 1932.
7] F.M. Moghaddam, M.G. Dekamin, M.S. Khajavi, S. Jalili, Bull. Chem. Soc. Jpn.,
75 (2002) 851.
[
[
[
[
8] M.S. Khajavi, M. Dakamin, H. Hazarkhani, J. Chem. Res. Synop., 3 (2000) 145.
9] J. Mizuya, T. Yokozawa, T. Endo, J. Polym. Sci., Polym. Chem., 29 (1991) 1545.
10] J.G. Noltes, J. Boersma, J. Organomet. Chem., 7 (1967) 6.
11] M. Ozaki, Y. Obora, Y. Tada, Y. Ishii, J. Organomet. Chem., 741-742 (2013)
109.
[
[
12] Y. Li, H. Matsumura, M. Yamanaka, T. Takahashi, Tetrahedron, 60 (2004) 1393.
13] a) I. Wakeshima, H. Suzuki, I. Kijima, Bull. Chem. Soc. Jpn., 48 (1975) 1069;
b) A.J. Bloodworth, A.G. Davies, J. Chem. Soc., (1965) 6858;
c) S.R. Foley, G.P.A. Yap, D.S. Richeson, Organometallics, 18 (1999) 4700.
14] A. Flamini, A.M. Giuliani, N. Poli, Tetrahedron Lett., 28 (1987) 2169.
15] J.F. Villa, H.B. Powell, Synth. React. Met.-Org. Chem., 6 (1976) 59.
[
[

[
16] a) X.C. Zhu, J.X. Fan, Y.J. Wu, S.W. Wang, L.J. Zhang, G.S. Yang, Y. Wei,
C.W. Yin, H. Zhu, S.H. Wu, H.T. Zhang, Organometallics, 28 (2009) 3882;
b) Y.J. Wu, S.W. Wang, X.C. Zhu, G.S. Yang, Y. Wei, L.J. Zhang, H.B. Song,
Inorg. Chem., 47 (2008) 5503.
[
[
[
17] F. Paul, S. Moulin, O. Piechaczyk, P. Le Floch, J. A. Osborn, J. Am. Chem. Soc.,
129 (2007) 7294.
18] H.R. Sharpe, A.M. Geer, H.E.L. Williams, T.J. Blundell, W. Lewis, A. J. Blake,
D.L. Kays, Chem. Comm., 53 (2017) 937.
19] a) B. Vidjayacoumar, D. J. H. Emslie, J. M. Blackwell, S. B. Clendenning
and J. F. Britten, Chem. Mater., 22 (2010) 4854;
b) J. Lewinski, K. Suwala, T. Kaczorowski, M. Galezowski, D. T. Gryko, I.
Justyniak and J. Lipkowski, Chem.Commun., 2 (2009) 215;
c) J. Lewinski, M. Dranka, I. Kraszewska, W. Sliwinski and I. Justyniak,
Chem.Commun., 39 (2005) 4935.
[20] Z. Wrobel, I. Justyniak, I. Dranka and J. Lewinski, Dalton.Trans., 45 (2016)
7240.
[
21] a) J. Lewinski, M. Koscielski, K. Suwala and I. Justyniak, Angew. Chem. Int.
Ed., 48 (2009) 7017;
b) N. Komine, R. W. Buell, C. H. Chen, A. K. Hui, M. Pink and K. G.
Caulton, Inorg. Chem.,53 (2014) 1361;
c) K.-M. Chien, T.-C. Hu, C.-H. Lin, Y.-C. Lo, T.-Y. Lee and J.-H. Huang,
J. Organomet. Chem.,779 (2015) 39.
[
[
22] T. Cadenbach, J. R. Pankhurst, T. A. Hofmann, M. Curcio, P. L. Arnold and J. B.
Love, Organometallics., 34 (2015) 2608.
23] a) Z.Q. Guo, X.H. Wei, Y.P. Hua, J.B. Chao, D.S. Liu, Tetrahedron Lett., 56
(
2015) 3919;
b) Z.Q. Guo, X.H. Wei, H.B. Tong, J.B. Chao, D.S. Liu, J. Organomet. Chem.,
83 (2015) 73;
c) Z.Q. Guo, X.H. Wei, H.B. Tong, D.S. Liu, J. Organomet. Chem., 776 (2015)
36;
7
1

d) Z.Q. Guo, Q. Liu, X.H. Wei, Y.B. Zhang, H.B. Tong, J.B. Chao, J.P. Guo, D.S.
Liu, Organometallics. 32 (2013) 4677;
e) Z.Q. Guo, S. Wang, H.B. Tong, J.B. Chao, X.H. Wei, Inorg. Chem. Commun.,
3
3 (2013) 68;
f) Q. Liu, Z.Q. Guo, H.F. Han, H.B. Tong, X.H. Wei, Polyhedron, 85 (2015) 15.
24] Sheldrick, G. M. Program for Crystal Structure Refinement; University of
[
Göttingen: Göttingen, Germany, 1997.
25] Program for Crystal Structure Refinement; Bruker Analytical X-ray Instruments
Inc.: Madison, WI, USA, 1998.
26] M. Lappert, A. Protchenko, P. Power, A. Seeber, Metal Amide Chemistry , John
Wiley & Sons, Ltd. 2009.
[
[

Lithium complex of 2-amino-functionalized benzoylpyrrole:
Synthesis, structure, and catalytic activity for the cyclotrimerization
of isocyanates
a*
Zhiqiang Guo, Yakong Wang, Jihong Yang, Xuehong Wei, *
b
b
a,b
a
Scientific Instrument Center, Shanxi University, Taiyuan, 030006, P. R. China
b
School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan,
030006, P. R. China
Graphical abstract