A PEG/copper(i) halide cluster as an eco-friendly catalytic system for C-N bond formation

Article abstract of DOI:10.1039/c8dt01310a

The catalytic activities of eight copper(i) halide clusters assembled from copper(i) halide and ferrocenyltelluroethers, 1-8, were investigated in C-N formation under various conditions. A catalytic procedure using poly(ethylene glycol) (PEG-400) as a gre

Full text of DOI:10.1039/c8dt01310a

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January 2016 Pages 1–398
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PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
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a Zr-metal–organic
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PEG/copper(I) halide cluster as an eco-friendly catalytic system
for C-N bond formation
a,⊥
a,⊥
a,b
,a
c
,d
ChengꢀAn Li , Wei Ji , Jian Qu , Su Jing* , Fei Gao , DunꢀRu Zhu*
____________________________________________________________________
a
School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing
11816, China. Eꢀmail: sjing@njtech.edu.cn.
2
b
c
Institute of Advanced Materials, Nanjing Tech University, Nanjing 210009, China.
Jiangsu Key Laboratory of Vehicle Emissions Control Center of Modern Analysis,
Nanjing University, Nanjing 210093, China.
d
College of Chemical Engineering, Nanjing Tech University, Nanjing 210009, China.
Eꢀmail: zhudr@njtech.edu.cn.
⊥These authors made equal contributions to this work.
Electronic supplementary information (ESI) available. CCDC 1823302ꢀ1823308.
†
For ESI and crystallographic data in CIF or other electronic format see DOI:
ABSTRACT
The catalytic activities of eight copper(I) halide clusters assembled from copper(I)
halide and ferrocenyltelluroethers, 1ꢀ8, were investigated in CꢀN formation under
various conditions. A catalytic procedure using poly(ethylene glycol) (PEGꢀ400) as a
greener alternative of organic solvent has been developed. PEGꢀ400/5 system can
achieve 99% targeted yield in mild reaction temperature and short reaction time. After
the isolation of the products by extraction with diethyl ether, this PEGꢀ400/cluster
system could be easily recycled. Spectroscopic studies elucidate a stepwise
mechanism: firstly, protonꢀcoupled electron transfer (PCET) involving the transfer of
+
electron from Cu and proton from imidazole results in the formation of the labile
2
+
pentaꢀcoordinated Cu and aryl radical; the following effective electron transfer from
2
+
ferrocene unit reduces Cu and forms the target product; finally, ferrocenium unit is
ꢀ
reduced by I anion. The merit of this ecoꢀfriendly synthesis is the efficient utilization

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of reagents and easy recyclability.
KEYWORDS
Ferrocenyltelluroether, copper(I) halide cluster, PEGꢀ400, CꢀN crossꢀcoupling
reaction, mechanism
INTRODUCTION
The catalytic CꢀN formation has been the subject of intense research due to its various
1
ꢀ3
biological applications. As compared to palladium, the low cost price of copper
endows the copperꢀcatalyzed CꢀN system a distinct financial advantage on an
4
ꢀ5
industrial scale, though the required high reaction temperatures, long reaction time,
ecologically harmful organic solvents and high catalyst loadings are still the major
6ꢀ9
drawbacks in the development of moreꢀefficient and milder methods. Also, several
computational derived mechanisms and experimentally obtained mechanistic
information suggest debated oxidative addition/reductive elimination or the radical
10ꢀ18
mechanism.
To construct and characterize simple and stable catalyst models have
been key to shed more light on the copper species involved in the reactions.
Multinuclear copper(I) halide clusters, a special kind of the copper(I) complexes
which have been proved to have rich and stable structure on account of the interaction
19ꢀ29
between copper centers, show a great potential in the field of catalysis.
openꢀcubane Cu tetramer bearing tripyrazolyl methane and a Cu cluster bearing
Nꢀorganic ligands were reported to show catalytic property in CꢀN crossꢀcoupling
An
4
I
4
2 2
I
3
0, 31
reactions.
Considering stable copper(I) complexes based upon soft Se or Te donor
atoms, our group is interested in the structureꢀproperty relation study of copper(I)
halide clusters based upon neutral ferrocenylchalcogenoethers. In our previous work,
2 2
we found that an 1D chain Cu X cluster of ferrocenyltelluromethane displayed a
good performance with target product in 91.3% yield in Ullmann crossꢀcoupling
3
2
reaction. And the introduction of ferrocene group into these copper(I) halide clusters
resulted in the enhancement of the catalytic reactivity and stability of these copper(I)

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clusters. However, these reported catalytic systems still cannot get rid of harmful and
uneasily recoverable organic solvents such as DMSO and DMF.
In concern of recyclability and environment protection, exploring the efficient
strategy to avoid using ecologically harmful organic solvents has aroused an
increasing interest in recent years. Solidꢀliquid phase transfer catalyst PEG has been
demonstrated as a greener alternative in organic synthesis because of its readily
availability, low cost, thermally stability, recoverability, biodegradability, and low
3
3ꢀ35
toxicity.
Buchwald and coꢀworkers reported that the addition of PEGꢀ400 in the
organic media increases the solubility of substrates and accelerates copperꢀcatalyzed
36, 37
Nꢀarylation under mild conditions.
With these in mind, we continued the systematic design of copper(I) halide
clusters constructed with ferrocenyltelluroethers and studied their catalytic activities.
Herein, eight copper(I) halide clusters 1ꢀ8 with diversity of nuclearity and geometries
were studied as catalysts in Ullmann CꢀN crossꢀcoupling reaction. Notably, cluster 5
showed the highest catalytic activity. Furthermore, the PEGꢀ400/copper(I) clusters
were found to catalyze Ullmann CꢀN crossꢀcoupling reaction under organic
solventꢀfree condition in high yield, mild reaction temperature and short reaction time.
The mechanistic insights provide applicable principles for future design of more
efficient catalysts in CꢀN formation.
RESULTS AND DISCUSSION
Synthesis and single crystal structural analysis
32
The clusters 1-8 were synthesized via the method shown in Scheme 1. Crystal
structures of L3, L4 and new copper(I) clusters 4ꢀ8 were determined by Xꢀray
crystallography (Scheme 1, Fig. S1 and Tables S1 and S2). Crystal data and structure
refinement detail of 4-8 are presented in Table 1.
ꢀ
Structural analysis revealed that 4 and 5 crystallize in the triclinic P1ꢁ space
group with a discrete Cu
2
X
2
cluster. The L3 displays a bidentate coordination mode to
+
+
chelate two Cu ions in 4 in contrast to its chelating one Cu ion in 5. Both 6 and 7

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crystallize in monoclinic P2
1
/n space group showing a 2D brickꢀwall network built
from Cu cluster (X = Br for 6 and X = I for 7). In both 6 and 7, four rhomboidꢀlike
2
X
2
neutral Cu
macrocycle. While 8 crystallizes in the triclinic P1ꢁ space group and contains one
extended 1D loop chain constructed from Cu clusters and bidentate bridgeꢀlinking
L5 ligands. All Cu(I) ions are fourꢀcoordinated with a tetrahedral configuration
Te /X ) in 4ꢀ8.
The CuꢀTe bond lengths and Cu⋯Cu distances in 1ꢀ8 are summarized in Table 2,
CuꢀTe bond length in 5 is found to be the longest one compares with the known CunIn
2 2
X clusters are linked by four L4 ligands in a bidentate mode to form a
ꢀ
2 2
I
(
2
2
3
2
clusters with ferrocenyltelluroethers. In our previous studies of catalytic CꢀN bond
formation, it has shown that steric hindrance of copper(I) clusters is an important
32
factor in the formation of intermediates during catalytic procedure. With the less
steric hindrance around copper(I) center, 5 should have the potential to behave the
best catalytic activity among these clusters.

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Scheme 1. Synthetic routes and structures of copper(I) halide clusters 1-8.

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Table 1 Crystal data and refinement details for 4-8.
Complexes
4
5
6
7
8
Empirical formula
C
46
H48Cu Br Fe Te
2 2 4 4
C
46
2
H48Cu I
2
Fe
Te
4 4
C
28
H
26CuBrFe
2
Te
2
C
28
H26CuIFe Te
2 2
C
28 2 2
H26CuIFe Te
Formula weight
Crystal system
1621.54
Triclinic
1715.52
Triclinic
872.84
919.83
919.83
Monoclinic
Monoclinic
Triclinic
ꢀ
P1
ꢀ
P1
ꢀ
P1
Space group
P2
1
/n
P2
1
/n
T /K
293
293
298
299
293
Wavelength / Å
0.71073
0.71073
0.71073
12.3650(6)
10.8200(5)
20.1765(9)
90
0.71073
12.4891(5)
10.9033(5)
20.1461(9)
90
0.71073
9.440(9)
9.571(9)
15.338(15)
90.472(12)
90.454(13)
94.755(12)
1381(2)
2
a /Å
b /Å
c /Å
α/°
10.623(2)
11.340(3)
12.013(3)
98.094(3)
10.5780(9)
11.4374(10)
11.7238(11)
100.572(3)
107.192(2)
110.620(2)
1200.84(19)
1
β/°
113.331(2)
110.988(2)
1171.3(5)
1
90.3880(10)
90
90.8190 (10)
90
γ/°
V /Å
3
2699.3(2)
4
2743.1 (2)
4
Z
ꢀ3
Dcalcd /Mg·m
ꢀ
2.299
2.372
2.148
2.227
2.212
ꢀ1
/mm
6.277
5.744
5.456
5.038
5.004
F(000)
764
800
1656
1728
864
Reflections/Unique
Parameters/Restraints
θ range /°
8335/4085
263/0
10263/5660
262/0
20868/6077
307/21
2.136ꢀ27.356
0.0350
0.0387
0.0941
27137/8437
307/6
9705/4803
307/0
1.956ꢀ25.005
0.1219
2.236ꢀ28.340
0.0236
2.124ꢀ30.700
0.0365
2.135ꢀ25.004
0.0220
R
R
int
[I > 2σ(I)]
[I > 2σ(I)]
0.0626
0.0251
0.0429
0.0217
1
wR
2
0.1592
0.0634
0.1090
0.0593

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GOF
Residuals /e·Å
1.027
1.106
0.579/ꢀ0.981
1.061
1.030
1.013
−
3
2.147/ꢀ2.498
1.365/ꢀ0.591
1.841/ꢀ0.851
1.055/ꢀ0.806
CCDC 1823304 (4), 1823305 (5), 1823306 (6), 1823307 (7), 1823308 (8) contain the supplementary crystallographic data for this paper.
Table 2 CuꢀTe bond distances (Å) and Cu⋯Cu distances (Å) in 1ꢀ8.
Complexes
CuꢀTe
1
2
3
4
5
6
7
8
2.590
.598
2.603
2.633
2.574
2.605
2.558
2.580
2.577
2.680
2.551
2.589
2.578
2.619
2.567
2.586
2
Cu
⋯Cu
2.813(7)/3.392(6)
2.848(6)
2.804(4)
2.696(7)
2.757(7)
2.906(6)
2.908(6)
3.472(23)

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Catalytic study
In our previous report, telluroetherꢀbased copper(I) clusters 1ꢀ3 units were effective
catalyst precursors in the Ullmann CꢀN crossꢀcoupling reaction. This model substrate
was chosen again to screen clusters 1ꢀ8, using 10 mol% Cu of cluster as the
precatalyst, and 2 equiv. of base (relative to the amount of iodobenzene) at 110°C. In
Table 3, the isolation yields of Nꢀ(4ꢀphenyl)imidazole are listed. Cluster 5 presented
the best catalytic activity and 99% yield of the target product (Table 3, entry 5).
Organic base, tꢀBuOLi, showed a better efficiency as compared to inorganic ones,
KOH (Table 3, entry 14), Cs CO (Table 3, entry 15) and K PO (Table 3, entry 16).
2
3
3
4
The solubility of base influences mass transfer and significantly affects the rate of
6, 10, 38ꢀ41
deprotonation.
Investigation of organic solvents (Table 3, entries 9ꢀ12) and
reaction temperatures (Table 3, entries 10 and 11) revealed the same trend as our
previous results.
To avoid using ecologically harmful organic solvents, PEGꢀ400 was investigated
instead of DMSO in the catalytic system based on 1ꢀ8, and the CꢀN coupling reaction
was performed using 10 mol% Cu of cluster as the precatalyst, and 2 equiv. of
tꢀBuOLi (relative to the amount of iodobenzene) at 85 °C for 12 h. A homogeneous
mixture was observed during the reaction process. By extraction with diethyl ether,
and the similar or better yields of targeted products were obtained as shown in Table 3
(entries17ꢀ24).Notably, PEGꢀ400/5 system shows 99% yield of the target product.
After the extraction of the products with diethyl ether, the PEGꢀ400/5 system was
reused for the next cycle by charging with imidazole and iodobenzene. The results of
five runs showed that they maintain high yields (99, 98, 97, 96, 96% respectively)
(Fig. 1 and Fig. S2). We were pleased to observe that this ecoꢀfriendly catalytic
system has the advantages of efficient utilization of all the reagents and easy
recyclability of the catalysts.
Next, the Nꢀsubstrate scopes of catalytic CꢀN bond formation under same
conditions were investigated. Three Nꢀsubstrates with electronꢀdonating group
performed well in the reaction catalyzed by PEGꢀ400/5, affording the corresponding
products in yields ranging from 88 to 96% (Table 4, entries 2ꢀ4).

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a
Table 3 Screening of catalysts in different conditions .
Entry
Catalyst
Solvent
Temp
°C)
Base
Time
(h)
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
12
12
12
12
12
12
12
12
Yield
[%]
b
(
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
5
5
5
5
5
5
5
5
1
2
3
4
5
6
7
8
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
110
110
110
110
110
110
110
110
110
80
40
100
90
110
110
110
85
85
85
85
85
85
85
85
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
KOH
89
95
85
81
99
43
80
45
trace
trace
0
1
1
0
1
MeCN
THF
1
1
1
1
1
1
1
1
2
2
2
2
2
2
3
4
5
6
7
8
9
0
1
2
3
4
H O
0
2
DMSO
DMSO
DMSO
76
94
33
23
92
96
88
85
99
80
85
82
Cs
K
3
2
CO
PO
3
DMSO
4
PEGꢀ400
PEGꢀ400
PEGꢀ400
PEGꢀ400
PEGꢀ400
PEGꢀ400
PEGꢀ400
PEGꢀ400
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
tꢀBuOLi
[a
] Reaction conditions: iodobenzene (0.25 mmol), imidazole (0.375 mmol), base (0.5 mmol),
copper(I) cluster (0.0125 mmol), solvent (2.0 mL), PEGꢀ400 (1.0 mL). [ ] Isolated yield.
b

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Fig. 1. Recycle procedure of the PEG/5 system.

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a
Table 4 Ullmann CꢀN crossꢀcoupling reaction of iodobenzene with different Nꢀsubstrates .
Entry
1
2
3
4
NꢀSubstrate
b
Product
c
Yield [%]
99
96
87
88
[a
] Reaction conditions: iodobenzene (0.25 mmol), Nꢀsubstrate (0.375 mmol),
t
ꢀBuOLi (0.5
mmol), copper(I) cluster (0.0125 mmol), PEGꢀ400 (1.0 mL), 12h, under air atmosphere. [
b
] The
1
13
H and C NMR spectra of desired products are shown in Fig. S3ꢀS6. [c] Isolated yield.
Identification of mechanism
With the aforementioned encouraging results, we further explored the catalytic
mechanism to gain insight into the reaction pathway. It was found that when adding
imidazole into DMSO solution of 5, the color of solution changed from yellowish
orange to green, in accordance with blueꢀshift absorption maxima, which can be
2
+ 42
ascribed to the existence of Cu . The ongoing addition of tꢀBuOLi into the
solution resulted in darker green with the absorptions maxima at 700 nm, which
+
can be ascribed to the formation of ferrocenium ion (fc1 , the oxidized form of
43ꢀ46
ꢀ
+
ferrocene) (Fig. 2)
shown in Fig. S7
.
Subsequent addition of I was found to reduce fc1 to fc1,
.
Fig. 2. UVꢀVis spectra of DMSO solution of 5 before (black line), after the addition of imidazole.

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(red line) and tꢀBuOLi (blue line).
Ethyl ether was then added into DMSO solution of 5 and imidazole to precipitate
the intermediate product, 5i. From Xꢀray photoelectron spectra shown in Fig. 3, it can
+
2+
be safely concluded the coexistence of Cu /Cu in 5i. The well fitted main peak of
Cu 2p3/2 at 934.6 eV and the wellꢀmarked satellite peak at 942.5 eV in 5i verify that
47
most of Cu are in +2 oxidation state (Fig. 3d). By comparing the ratio of intensity of
48, 49
satellite peak to that of the main peak (Isat/Imain= 0.74),
a weak peak at 932.9 eV is
acquired. According to the peak of Cu 2p3/2 in cluster 5 (Fig. 3c), this indicates the
+
existence of Cu in 5i. Furthermore, the highꢀfield shift of binding energy of Te 3d of
50
5
i as compared to that of 5 also supports the conclusion (Fig. 3f). The coordination
of N atom with Cu center in 5i was confirmed by the Fourier Transform infrared
51
ꢀ1
spectra (FTIR), the vCꢀN of free imidazole observed at 1052 cm and vring of
ꢀ1
ꢀ1
imidazole at 1444 cm shifted to 1083 and 1474 cm , respectively (Fig. S8). No
similar phenomena were observed when only adding iodobenzene into DMSO
solution of 5.
Fig. 3. XPS spectra of 5 (black line) and intermediate 5i (red line).
Based on the above observations, the proposed mechanism is shown in Scheme 2.
When adding imidazole, a dynamic equilibrium via a PCET process happened (cycle
I). As an effective approach, PCET can stabilize the intermediate redox products and

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5
2
avoid the highꢀenergy intermediates. In the current system, PCET process concludes
+
electron transfer from Cu , coupling of proton from imidazole, which leads to the
2+
ꢀ
formation of pentaꢀcoordinated Cu complex with two tellurium atoms, two I anion
+
ꢀ
and one imidazolate anion. Through the fast H /e recombination step, imidazolate is
+
released due to the tetraꢀcoordinated mode of Cu . In comparison, the rate of electron
2
+
transfer from ferrocene to Cu is too slow to be the dominating step. This dynamic
+
equilibrium is broken when adding tꢀBuOLi, H is then consumed into H
2
O and the
+
ꢀ
electron provided by Cu centre attacks the aryl halide to give aryl radical and I
2+
+
(
cycle II). The ongoing electron transfer from ferrocene to Cu recovers Cu and
releases imidazolate. The reactive imidazolate combines phenyl radical group to form
+
ꢀ
the target product (cycle II). Finally, fc1 is reduced to fc1 by I .
Scheme 2 Proposed mechanism for 5 catalyzed CꢀN formation
.
In the above proposed mechanism, the effective electron transfer from ferrocene to
2
+
Cu is important for the whole catalytic procedure. Clusters 4 and 5 have similar

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structure, though their catalytic properties are quite different. Cyclic voltammetry (CV)
was then performed to investigate redox properties of ferrocene in these two clusters.
Ferrocene moiety in 5 is found to be oxidized more easily than that in 4 (Table S3 and
2
+
Fig. S9), indicating that electron transfer from ferrocene to Cu in 5 occurs easier.
CONCLUSION
In the current study, five new copper(I) halide clusters 4ꢀ8 have been successfully
constructed from copper(I) halide and ferrocenyltelluroethers. The catalytic activities
of eight copper(I) halide clusters, 1ꢀ8, were investigated in CꢀN formation under
various conditions. An ecoꢀfriendly reusable catalytic procedure has been developed
using PEGꢀ400/copper(I) halide clusters. It’s found that the best performed system is
PEGꢀ400/5, in which, a target product in 99% yield can be obtained in mild reaction
temperature and shorter reaction time. Mechanistic study shows a concerted PCET
process with Cu center as an electron donor and imidazole as a proton donor, which
facilitates the activation under mild catalytic conditions. The electron transfer from
2+
ferrocene group to Cu center results in the release of reactive intermediate due to the
+
2+
different coordination modes of Cu and Cu centers. The merits of this catalytic
system are efficient utilization of all the reactants, easy recyclability of the catalysts,
and good performance in Nꢀsubstrates with electronꢀdonating group.
EXPERIMENTAL SECTION
General procedures
Ferrocene,
imidazole, tellurium, 4ꢀmethylimidazole, 4ꢀphenylimidazole, benzimidazole,
ꢀnitroimidazole, iodobenzene, bromobenzene, sodium borohydride, lithium
dibromopropane,
α,α'ꢀdibromoꢀpꢀxylene,
α,α'ꢀdibromoꢀmꢀxylene
4
tertꢀbutoxide, CuX (X = Br or I), PEGꢀ400 are of AR grade. All solvents used were
1
purified and dried following standard procedures prior to use. H NMR spectra were
recorded on a Bruker DRX spectrometer (400 MHz) at ambient temperature. Mass
spectra were recorded on positiveꢀion electrospray (ES). Melting points were
determined using the cover glass and uncorrected. Elemental analyses of C, H and N
were performed on a PerkinꢀElmer 2400 CHN elemental analyzer. Electrochemical

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measurement was recorded using a CHI660D electrochemical workstation of
Shanghai CH Instruments Co. A three electrode arrangement was used with a Pt
+
working electrode, a Pt wire counter electrode, and an Ag/Ag (0.01 M AgNO
3
in
CH
3
CN, referenced against ferrocene/ferrocenium) reference electrode. It was
performed at room temperature in a dry MeCN containing a 0.1 M [nꢀNBu ][PF ]
4
6
ꢀ1
electrolyte, with the sweep rate 100 mV S for cyclic voltammetry. XPS was
performed on a PHI 5000 Versa Probe system; all binding energies were referenced to
C1s peak at 284.6 eV. UVꢀvis absorption spectra were recorded on a HITACHI
spectrophotometer UVꢀ3900. IR spectra were recorded on a Thermo Scientific Nicolet
ꢀ1
IS10 FTIR spectrometer using KBr pellets within the 400ꢀ4000 cm region. Synthesis
of L1-L3 and 1ꢀ3, and single crystal structures of L1-L2 and 1ꢀ3 have been reported
32, 53
before by our group.
-8 were synthesized and characterized.
Synthesis of L4ꢀL5 and 4-8
Following the same procedure, ligands L4ꢀL5 and clusters
3
2
4
α,α'ꢀDi(ferrocenyltelluro)ꢀpꢀxylene (L4). The target product was obtained as an
1
orange solid in the yield of 58%. H NMR (δ, ppm): 6.87 (C
6
H
4
, s, 4H), 4.22 (C
5
H
4
, s,
8
H), 4.12 (C
5
5 2
H , s, 10H), 3.91 (TeCH , s, 4H). Elemental Analysis Calcd (%) for
+
C
28
H
26Fe
2
Te
2
: C 46.10, H 3.59; found: C 46.32, H 3.70. ESMS: 728.8 ([M ]).
IR(KBr): v= 2962(m), 2343(w), 1652(m), 1458(w), 1409(w), 1383(w), 1261(vs),
1097(s), 1018(s), 802(s), 705(m), 576(w), 493(w).
α,α'ꢀDi(ferrocenyltelluro)ꢀmꢀxylene (L5). The target product was obtained as an
1
orange solid in the yield 60%. H NMR (δ, ppm): 6.95 (C H , t, H), 6.81 (C H , d,
6
4
6
4
2
H), 6.74 (C
6
H
4
, s, H), 4.22 (C
5
4
H , m, 4H), 4.20 (C
5
4
H , m, 4H), 4.12 (C
5
H
5
, s, 10H),
3
.86 (TeCH
2
, s, 4H). Elemental Analysis Calcd(%) for C28H26Fe Te : C 46.10, H 3.59;
2 2
+
found: C 46.35, H 3.73. ESMS:729 ([M ]). IR(KBr): v = 2916(m), 2364(m), 1652(s),
1
135(m), 1103(m), 1047(m), 1012(m), 869(w), 806(s), 667(w), 488(s).
Cu Br (L3) ] (4). Pure needle crystals of 4 were obtained with 22% yield based
on Cu. IR(KBr): v = 1408(w), 1345(w), 1152(m), 1113(m), 1052(s), 1016(m), 877(m),
25(vs), 752(m), 609(w). M.p. 162ꢀ163 °C. Elemental Analysis Calcd (%) for
Fe Br Te : C 34.07, H 2.98; found: C 34.38, H 3.19.
[
2
2
2
8
C
46
H
48Cu
2
4
2
4

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DOI: 10.1039/C8DT01310A
2 2 2
[Cu I (L3) ] (5). Pure cube crystals of 5 were obtained with 11% yield based on
Cu. IR (KBr): v = 1406(m), 1147(m), 1105(m), 1000(s), 867(w), 814(vs), 752(w),
6
33(w). M.p. 160ꢀ161 °C. Elemental Analysis Calcd (%) for C46
2.21, H 2.82; found: C 32.43, H 2.96.
2 4 2 4
H48Cu Fe I Te : C
3
[
Cu Br (L4) ] (6). Pure tabular crystals of 6 were obtained with 18% yield
2 2 2 n
based on Cu. IR (KBr): 1411(m), 1133(m), 1121(m), 1008(s), 967(w), 810(vs),
42(w), 621(w). M.p. 175ꢀ176 °C. Elemental Analysis Calcd (%) for
7
C
28
H
26CuFe
2
BrTe
2
: C 38.53, H 3.00; found: C 38.74, H 3.22.
[Cu
2
I
2
(L4)
2
]
n
(7). Pure tabular crystals of 7 were obtained with 9.2% yield based
on Cu. IR (KBr): v = 1408(w), 1340(w), 1158(m), 1118(m), 1032(s), 1014(m), 873(w),
20(vs), 748(m), 612(w). M.p. 178ꢀ179 °C. Elemental Analysis Calcd (%) for
8
C H CuFe ITe : C 36.56, H 2.85; found: C 36.75, H 2.96.
28
26
2
2
[Cu
2
I
2
2 n
(L5) ] (8). Pure cube crystals of 8 were obtained with 20.4% yield based
on Cu. IR (KBr): v = 3093(m), 1600(m), 1482(m), 1440(w), 1407(m), 1377(w),
139(s), 1103(m), 1062(w), 1022(s), 1000(s), 929(w), 873(s), 819(vs), 734(w),
01(w), 688(s), 496(vs). M.p. 182ꢀ183 °C. Elemental Analysis Calcd (%) for
Fe Te : C 36.56, H 2.85; found: C 36.67, H 2.98.
1
6
C
56
H
52Cu
2
4
I
2
4
Catalytic reaction in organic solvents
The iodobenzene (0.25 mmol), imidazole (0.375 mmol) and base (0.5 mmol) were
added to a 2 mL solution of the copper(I) cluster (0.0125 mmol). The vial was sealed
and heated at 110 °C for 24h. 10 mL water was added after the system cooled to room
temperature. The product was extracted with ethyl acetate. The combined organic
4
layer was dried over anhydrous MgSO and removed the solvent through evacuation.
The objective product was obtained by column chromatography elution with
hexane/ethyl acetate.
Catalytic reaction in PEG-400/cluster system
The Nꢀsubstrate (0.375 mmol), iodobenzene (0.25 mmol), base (0.5 mmol), the cluster
(0.0125 mmol copper(I) amount) and PEGꢀ400 (1.0 mL) were added into a 10 mL vial.
The vial was sealed and heated at 85°C for 12h. After cooling to room temperature,

Page 17 of 20
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DOI: 10.1039/C8DT01310A
the product was extracted with diethyl ether (5 mL). The separating diethyl ether
solvent was removed under vacuum. The object was obtained by column
chromatography elution with hexane/ethyl acetate.
Xꢀray crystallography
All singleꢀcrystal Xꢀray diffraction measurements were conducted using a Bruker
SMART APEX II CCD diffractometer with graphiteꢀmonochromated Mo K
α
radiation
(λ = 0.71073 Å) at ambient temperature. Multiꢀscan absorption corrections were
applied. The structures were solved by direct methods and refined by the fullꢀmatrix
2
leastꢀsquares based on F using SHELXLꢀ2014. All nonꢀhydrogen atoms were refined
anisotropically. Hydrogen atoms were placed on calculated positions (CꢀH 0.96 Å)
and assigned isotropic thermal parameters riding on their parent atoms. Diamond and
Mercury software were used in preparation of figures for all clusters.
Conflicts of interest
There are no conflicts to declare.
Acknowledgement
We gratefully acknowledge financial support from the National Natural Science
Foundation of China (Grant Nos. 21671101, 21476115 and 21171092) and Nanjing
Tech Research Foundation for Dr. Wei Ji.
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DOI: 10.1039/C8DT01310A
SYNOPSIS
PEG/ferrocenyltelluroether-based copper(I) halide cluster is eco-friendly system in C-N formation
with mild reaction condition, high yield and easy recyclability.