Synthesis, characterization and crystal structure of Cu(II) complex of trans-cyclohexane-1,2-diamine: Application in synthesis of symmetrical biaryls

Article abstract of DOI:10.1016/j.molstruc.2016.12.053

A new Cu(II) complex [Cu(cyhxn)₂(H₂O)₂][OTf]₂ was synthesised by the reaction of ligand cyhxn (cyhxn?=?trans-cyclohexane-1,2-diamine) with Cu(OTf)₂ in methanol at room temperature. The complex was fully characterized by elemental analysis (CHN), FT-IR, UV–Vis and EPR spectroscopic techniques. The structure of the complex was confirmed by single crystal X-ray diffraction study. The EPR spectrum is isotropic type having g_iso?=?2.078, which indicates a distorted octahedral geometry of the complex. The complex was found to be an active homogeneous catalyst for the homocoupling reactions of arylboronic acid to obtain symmetrical biaryls at room temperature in methanol without the use of any additives such as a base and or an oxidant.

Full text of DOI:10.1016/j.molstruc.2016.12.053

Journal of Molecular Structure 1134 (2017) 85e90
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Synthesis, characterization and crystal structure of Cu(II) complex of
trans-cyclohexane-1,2-diamine: Application in synthesis of
symmetrical biaryls
a
a
a
a
b
Bhumika Agrahari , Samaresh Layek , Shweta Kumari , Anuradha , Rakesh Ganguly ,
a, *
Devendra D. Pathak
Department of Applied Chemistry, Indian Institute of Technology (ISM), Dhanbad, 826004, India
a
b
Division of Chemistry & Biological Chemistry, Nanyang Technological University, 639798, Singapore
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 October 2016
Received in revised form
A new Cu(II) complex [Cu(cyhxn) (H O) ][OTf] was synthesised by the reaction of ligand cyhxn
2
2
2
2
(
cyhxn ¼ trans-cyclohexane-1,2-diamine) with Cu(OTf)
2
in methanol at room temperature. The complex
was fully characterized by elemental analysis (CHN), FT-IR, UVeVis and EPR spectroscopic techniques.
The structure of the complex was confirmed by single crystal X-ray diffraction study. The EPR spectrum is
isotropic type having giso ¼ 2.078, which indicates a distorted octahedral geometry of the complex. The
complex was found to be an active homogeneous catalyst for the homocoupling reactions of arylboronic
acid to obtain symmetrical biaryls at room temperature in methanol without the use of any additives
such as a base and or an oxidant.
20 December 2016
Accepted 20 December 2016
Available online 24 December 2016
Keywords:
Copper complex
Crystal structure
Biaryls
©
2016 Elsevier B.V. All rights reserved.
CeC coupling
Homogenous catalyst
1. Introduction
stability and non-toxic nature [17].
In 1996, the homocoupling of arylboronic acids was first re-
ported by Moreno-Manas et al. using palladium complexes of
monodentate phosphines [18]. Consequently, homocoupling of aryl
boronic acid using palladium-based catalysts are frequently used
[19]. However, reported methods have some limitations. Palladium
is expensive and requires additional ligands [20] and stoichiometric
amount of oxidants to stabilize and, to restore the catalytically
active palladium(II) species, respectively [21]. The reaction often
requires a base [22] and generally needs high temperature [23].
Other catalysts based on Au [24], Rh [25], Ni [26], Cr [27] and Cu
[28e35] also have been reported to facilitate the homocoupling of
arylboronic acids. Recently, Singh et al. reported Ru-catalyzed
oxidative homocoupling of arylboronic acid [36]. However, Cu-
The coupling reactions are one of the most important tool in
organic synthesis for formation of CeC and CeX bonds (X ¼ N, O, S
etc) [1,2]. During the last two decades, the CeC bond formations
have allured much interest and revolutionized the organic syn-
thesis [3]. The CeC bond formation has emerged as an important
synthetic methodology for generating more complicated organic
compounds from simpler ones [4]. Specifically, the CeC coupling
products, symmetrical and unsymmetrical biaryls, are in huge de-
mand in synthesis of natural products, fine chemicals [5e11], ag-
rochemicals and optically active ligands [12]. They are synthesised
by various methods reported in literature such as, Suzuki reaction
[
[
13], Ullmann reaction [14], and Kumada-Corriu-Tamao reaction
15] etc. Suzuki coupling reaction is one of the most important
based catalysts such as Cu(OAc)
Cu( -OH)} Cl ]$3H [29], CuSO
nanoparticles-supported Cu(II)- -cyclodextrin complex [32], Cu
2
[28], [{(1,10-phenanthroline)
methodology for synthesis of symmetrical biaryls from a single aryl
precursor [16]. Arylboronic acids are most extensively used as a
precursor for coupling reactions owing to their ease of availability,
m
2
2
2
O
4
[30], CuCl [31], Fe
3 4
O
b
terephthalate metal organic frameworks [33], nano rod CuO [34]
and CuFAP [35] have emerged as cheap catalysts for obtaining
symmetrical biaryls by the homocoupling reaction of arylboronic
acids.
*
Corresponding author.
E-mail address: ddpathak@yahoo.com (D.D. Pathak).
http://dx.doi.org/10.1016/j.molstruc.2016.12.053
022-2860/© 2016 Elsevier B.V. All rights reserved.
0

86
B. Agrahari et al. / Journal of Molecular Structure 1134 (2017) 85e90
Table 1
2. Experimental
Crystal data and refinement parameters of [Cu(cyhxn)
2 2
(H O)
2
][OTf]
2
complex.
CCDC deposition number
Chemical formula
Formula weight
Temperature
Wavelength
Crystal size
Crystal system
Space group
1473725
2.1. Materials and instrumentations
C
14
H32CuF
6
N
4
O
8
S
2
626.09 g/mol
103(2) K
1.54178 Å
All reagents and solvents for the synthesis and analysis were
purchased from commercially sources. Trans-cyclohexane-1,2-
diamine (cyhxn), phenylboronic acids and other required chem-
icals were purchased from Merck and Sigma Aldrich and used as
received without further purifications.
0.080 ꢂ 0.120 ꢂ 0.180 mm
Monoclinic
P2(1)/c
Unit cell dimensions
a (Å)
b (Å)
FT-IR spectra were recorded on a Perkin Elmer Spectrometer
10.0558(2)
10.2611(2)
25.0451(4)
90
99.2522(9)
90
2550.62(8)
4
1.630 g/cm
3.576 mm
1292
0.0398
0.0445
0.1092
ꢀ
1
(Model: Cary 660) in the range of 4000e400 cm using KBr pellets
c (Å)
in which MCT used as a detector with scan number 20, and reso-
O
ꢀ1
a
b
g
( )
lution 8 cm . Electronic absorption spectral analysis was recorded
O
ꢁ
( )
on a Shimadzu UV-1800 Spectrophotometer in the wave length
range of 200e1100 nm using methanol as solvent. Elemental ana-
lyses were carried out using a Heraeus CHN-Rapid elemental
analyzer. The NMR spectra of the isolated products were recorded
on a Bruker AvIII HD-300 MHz and 400 MHz spectrometer in CDCl
using TMS as the internal Standard. Melting points were recorded
on a Yazawa micro melting point apparatus.
O
( )
3
V(Å )
Z
3
Density (calculated)
Absorption coefficient
F(000)
ꢀ
1
3
R
R
int
1
[I > 2
d(I)]
wR
2
(all data)
ꢀ
3
Largest diff. peak and hole
R.M.S. deviation from mean
0.654 and ꢀ0.492 eÅ
ꢀ3
0.071 eÅ
2 2 2 2
2.2. Synthesis of [Cu(cyhxn) (H O) ][OTf] complex
A methanolic solution of ligand trans-cyclohexane-1,2-diamine
0.1142 g, 1 mmol) was added dropwise to a clear solution of
(
Copper(II) trifluoromethanesulfonate (0.1808 g, 0.5 mmol) in
methanol (10 mL). The resultant solution was stirred at room
temperature for 6 h to produce a dark blue coloured solution. The
diffraction quality crystals of the titled complex were obtained
directly by slow evaporation of the deep bluish methanolic solution
ꢁ
at room temperature. Yield: 0.272 g, 75%, m.p: 258 C, Anal. Calc. for
C
5
2
14
H
32CuF
.32, N, 8.78. Selected FT-IR (KBr), cm
967e2861, (OH) 3463, (CueN) 628,
6 4 8 2
N O S : C, 26.86; H, 5.15; N, 8.95. Found: C, 26.54; H,
ꢀ
1
:
n
(NH
2
) 3332e3279,
n
(CH
2
)
n
n
n
(CueO) 514. UVeVis [
l
ꢀ
1
ꢀ1
max(nm), ε (L mol cm )]: 243 (8940), 548 (89).
2 2 2 2
Scheme 1. Synthesis of [Cu(cyhxn) (H O) ][OTf] complex.
Majority of reported approaches involves the use of stoichio-
metric amount of catalyst, oxidant, co-catalyst, malodorous solvent,
a base and require high temperature and prolong reaction time for
completion of the reaction. In order to circumvent these inherited
drawbacks, a quest for the rational design of new catalyst capable of
catalyzing the reaction at room temperature without the use of a
base or oxidant, was realized. Herein, we describe the synthesis and
2.3. General procedure for synthesis of biaryls
In a 25-mL round-bottomed flask, a solution of copper(II)
complex (2 mol %) and substituted phenylboronic acid (1.5 mmol)
in methanol (5 mL) was stirred at room temperature for 3e4 h. The
progress of the reaction was monitored by TLC. After completion of
the reaction, the solvent was removed and the product was washed
with water and extracted with ethyl acetate (3 ꢂ 10 mL). The
combined organic layers were dried over Na SO and the solvent
removed under reduced pressure to give crude product which was
purified by column chromatography by using petroleum ether/
ethyl acetate (4:1) as an eluent.
2 2 2
characterization of a new Cu(II) complex, [Cu(cyhxn) (H O) ][OTf]2,
and its application in the synthesis of symmetrical biaryls by
homocoupling reaction of arylboronic acids without the use of a
base and oxidant at room temperature.
2
4
Fig. 1. (a) ORTEP diagram of complex [Cu(cyhxn)
clarity.) (b) Packing structure of complex.
2 2 2 2
(H O) ][OTf] (Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and triflate anions are removed for

B. Agrahari et al. / Journal of Molecular Structure 1134 (2017) 85e90
87
Table 2
Table 3
ꢁ
Selected bond distances (Å) and bond angles ( ) of
Study of reaction optimization conditions.
[
2 2 2 2
Cu(cyhxn) (H O) ] [OTF] .
Entry
Solvent
Catalyst loading (mol %)
Time (h)
Yield, %a
Bond distances
Cu1eN1
Cu1eN2
Cu1eN3
Cu1eN4
Cu1eO1
Cu1eO2
C1eN1
C2eN2
1
2
3
4
5
6
7
8
9
CH
CH
CH
CH
3
3
3
3
OH
OH
OH
OH
e
1
2
5
2
2
2
2
2
24
05
03
03
08
08
12
12
12
00
70
85
75
40
70
53
25
25
2.036(2)
2.013(2)
2.036(2)
2.009(2)
2.442(19)
2.455(19)
1.487(5)
1.546(5)
1.536(5)
1.484(5)
2
H O
C
C
6
H
H
5
CH
CN
3
6
5
DCM
DMF
C7eN3
C8eN4
a
Isolated yield.
Bond angles
N1eCu1eN2
N1eCu1eN3
N2eCu1eN3
N1eCu1eN4
N2eCu1eN4
N3eCu1eN4
N1eCu1eO1
N2eCu1eO1
N3eCu1eO1
N4eCu1eO1
84.28(9)
179.71(9)
95.47(9)
95.89(9)
179.80(9)
84.36(9)
86.90(9)
88.27(9)
93.23(9)
91.63(9)
temperature (Scheme 1) afford the complex [Cu(cyhxn)
2 2 2
(H O) ]
[
OTf] as a deep blue crystalline solid. Block shaped crystals, suit-
2
able for X-ray crystallography were obtained by slow evaporation of
the blue solution at room temperature. The complex was fully
characterized by elemental analysis (CHN), FT-IR, UVeVis and EPR
analysis and the structure was confirmed by single crystal X-ray
diffraction study.
3.1. X-ray crystal study
2.4. Single crystal X-ray structure determination of copper(II)
complex
The diffraction quality crystals were obtained by the slow
evaporation of methanolic solution of complex at room tempera-
ture. The structure of the complex was elucidated by single crystal
X-ray diffraction. Fig.1 represent an ORTEP view and atom-labelling
The X-ray diffraction intensity data were measured at 103 K
with a Bruker Kappa diffractometer equipped with a CCD detector,
employing Cu radiation (
programs [37]. All data were processed and corrected for Lorentz
and polarization effects with SAINT and for absorption effects with
SADABS [38]. All the calculation were carried out using the
SHELXTL suite of programs [39]. The integration of the data using a
2
þ
l
¼ 1.54178 Å), with the SMART suite of
scheme of the dicationic [Cu(cyhxn)
2
(H
2
O)
2
]
complex. The
structure reveals a six-coordinated species with a distorted octa-
hedral geometry. Selected bond distances and bond angles are lis-
ted in Table 2. The four nitrogen atoms of two cyclohexyldiamine
molecules bind in an equatorial fashion to the copper ion which
forms two five-membered rings, while the two oxygen atoms of
weakly coordinated water molecules bind to copper ion in an axial
fashion. The CueO and CueN bond lengths of this complex are lies
in the range of 2.4425 (19) Å to 2.4555 (19) Å and 2.009 (2) Å to
2.036 (2) Å respectively, which are in close agreement with the
values of previously reported other copper(II) diamine complexes
[40,41]. The complex shows two types of NeCueN bond angles, in
the range of 84.28(9)-95.89(9) and 179.71(9)-179.80(9) which are
similar with previously reported Cu(II) complexes [42].
monoclinic unit cell yielded a total of 9213 reflections to a
ꢁ
maximum
q
angle of 26.47 (0.80 Å resolution), of which 2345 were
independent (average redundancy 3.929, completeness ¼ 99.6%, R
int ¼ 5.67%, R sig ¼ 5.24%) and 1875 (79.96%) were greater than
2
2
c
s
(F ). The final cell constants of a ¼ 10.0558(2) Å, b ¼ 10.2611(2) Å,
ꢁ
ꢁ
ꢁ
90 ,
¼
25.0451(4) Å,
a
3
¼
90 ,
b
¼
99.2522(9) ,
g
¼
volume ¼ 2550.62(8) Å , are based upon the refinement of the XYZ-
centroids of 8003 reflections above 20 (I) with
< 133.2 . All non hydrogen atoms were refined with
s
ꢁ
.909 < 2q
ꢁ
8
anisotropic thermal parameters. The cyclohexane rings are disor-
dered, these are modelled in two alternative sites with equivalent
occupancy of 0.5. Appropriate restraints (SIMU and ISOR) were
applied for C3, C6, C3A and C6A atoms. A summary of the crystal-
lographic and refinement data are given in Table 1.
The FT-IR spectra of free ligand and complex are shown in Fig. S1
(See Supporting information). The FT-IR spectrum of free ligand
ꢀ
1
shows characteristics band at 3355-3279 cm
and 2924-
) respectively [43]. A
band at 3463 cm in the spectrum of the complex was assigned to
the presence of coordinated H O [44]. The intense band in the IR
ꢀ
1
2 2
2851 cm assignable to n(NH ) and n(CH
ꢀ
1
2
ꢀ1
spectrum around 1320-1170 cm confirms the presence of triflate
3
. Results and discussion
anion [45]. A comparison of the IR spectrum of the complex with
ꢀ1
ꢀ1
.
the ligand indicated two new bands at 628 cm and 514 cm
These bands were assigned to (CueN) and (CueO) vibrations,
respectively [46]. Presence of these bands confirms the
The reaction of ligand trans-cyclohexane-1,2-diamine and Cop-
n
n
per(II) trifluoromethanesulfonate in 2:1 ratio in methanol at room
Scheme 2. Synthesis of biaryl derivatives.

Table 4
Synthesis of biaryls from various arylboronic acid in presence of Cu(II) catalyst under the optimized reaction conditions.
Entry
1
Boronic acid
Product
Time
3
Yielda
85
2
3
2
3
80
75
4
3
80
5
6
2.5
3
85
65
7
3
80
8
9
3
75
70
2.5
1
1
0
1
2.5
75
60
3
1
2
3
3
3
40b
1
50b
a
Isolated yield after work up.
By-product naphthalene.
b

B. Agrahari et al. / Journal of Molecular Structure 1134 (2017) 85e90
89
Table 5
A comparison study of catalyst [Cu(cyhxn)
2 2
(H O)
2
][OTf]
2
with the previous reported catalysts in synthesis of biaryls.
ꢁ
Entry
Catalyst
Au/CeO
Additive
Base
Temp ( C)
Catalyst loading (mol %)
Time (h)
Yield (%)
Ref.
1
2
3
4
5
6
2
e
e
2
K CO
3
3
60
70
60
RT
70
RT
5
15
24
3
24
4
100
90
92
78
67
85
[24]
[31]
[20]
[27]
[35]
Fe eCu
Pd(OAc)
Cu(OAc)
3
O
4
2
e
b
eCD
e
10
3.6
50
2.5
2
2
[Bmim]PF
e
6
2
K CO
2
e
Ru catalyst
[Cu(cyhxn)
Cu(OAc)
2
Na
e
2 3
CO
2
(H
2
O)
2
] [OTf]
2
e
3
Present work
Scheme 3. Tentative mechanism for synthesis of biaryl derivatives.
coordination of copper with N and O atoms of the ligand and H
molecule, respectively.
2
O
It can be concluded that the nature of the substituent, either
electron donating or withdrawing groups, did not show a signifi-
cant change in the overall yields (Table 4, entries 2e11). However,
para- and meta-substituted arylboronic acids afforded biaryls in
good yield (Table 4, entries 2e10). On the contrary, ortho-
substituted arylboronic acids resulted in relatively lower yield of
the product (Table 4, entries 11e12). Bulky acids afforded low yields
which may be ascribed to steric effects. The reaction of 1-napthyl-
and 2-napthylboronic acids yielded the expected homocoupled
products in 40e50% yield only, along with protodeboronation by-
products (Table 4, entries 12e13). These observations are in
consonance with the previous observations [28]. The organic
products were soluble in common organic solvents and fully
The UVeVis spectra of ligand and complex are shown in Fig. S2
(
See Supporting information). The UVeVis spectra of ligand
*
depicted a strong peak at 219 nm due to nꢀ
s
transition of NeC
bond. However, UV spectra of the complex showed a slight shift in
the position and intensity of this band at around 243 nm. The
spectrum of the complex also shows an additional broad band at
2
2
5
48 nm, assignable to
1g g
B / E transition of a tetragonally dis-
torted Cu(II) in Octahedral geometry [47].
3.2. EPR study
1
13
characterized by melting point, H and C NMR and FT-IR spectra.
The spectra are given in the supporting information
The EPR spectrum of the complex recorded at room temperature
is shown in the Fig.S3 (See Supporting information). The EPR
spectrum of the powdered complex [Cu(cyhxn) (H O) ][OTf] at
00 K, revealed an isotropic behaviour with broad signal having
iso ¼ 2.078 with no hyperfine structure and confirmed a six-
coordinated distorted octahedral geometry of the complex [48].
(Fig. S4eFig. S25). In order to establish the efficacy of the new
2
2
2
2
catalyst [Cu(cyhxn) (H O) ][OTf] , a comparison was made with
2
2
2
2
3
g
the previously reported catalysts for the synthesis of biaryls in
terms of temperature, time, catalyst loading etc (Table 5). The re-
sults indicate that our catalytic system exhibits better catalytic
activity as compared to other reported catalysts.
A tentative mechanism for synthesis of biaryls is proposed in
Scheme 3. We speculate that the reaction proceeds by coordination
of aryl groups to Cu(II) centre by displacement of labile water
molecules from octahedral Cu(II) complex [49], generating aryl-
copper intermediate which undergoes oxidation by air to give a
putative Cu(III) intermediate. This intermediate undergoes reduc-
tive elimination to give Cu(I) and the desired homocoupled product
3.3. Catalytic studies
The catalytic activity of the complex was screened for the syn-
thesis of biaryls (Scheme 2). Various phenylboronic acids were
chosen as substrates. Several parameters such as catalyst loading,
solvent and time were studied and optimized. The results are
summarised in Table 3. Initially phenylboronic acid was chosen as
an ideal substrate. On stirring a methanolic solution (without
catalyst) of phenylboronic acid for 24 h at room temperature did
not yield any product (Table 3, entry 1). However, when the reac-
tion was carried out in presence of 1 mol % of the catalyst, 70% yield
of the desired product was obtained in 5 h (Table 3, entry 2).
Increasing the catalyst loading to 2 mol % resulted in 85% yield of
the desired product in 3 h (Table 3, entry 3). However, no significant
improvement in yield was observed by further increasing the
amount of catalyst to 5 mol % (Table 3, entry 4). It indicated that
(biaryl), as reported earlier [30,34].
4. Conclusion
2 2 2 2
In conclusion, a new complex [Cu(cyhxn) (H O) ][OTf] has
been synthesized and fully characterised by various spectroscopic
techniques (Elemental analysis (CHN), FT-IR, UVeVis, EPR) and by
single crystal X-ray structure determination. The catalytic applica-
tion of the complex has been demonstrated in the synthesis of
symmetrical biaryls from arylboronic acids. The homocoupling
reaction proceeds smoothly in methanol at room temperature at a
low catalyst loading (2 mol %) and without the use of any additives
and bases.
2
mol % of the catalyst is optimum. In order to found the best sol-
vent, the reaction was carried out in different solvents such as,
CH OH, H O, C CH3, CH CN, DCM and DMF (Table 3) at room
temperature. Among all the solvents used, CH OH (Table 3, entries
e4) was found to be the best solvent.
3
2
6
H
5
3
3
2

90
B. Agrahari et al. / Journal of Molecular Structure 1134 (2017) 85e90
Acknowledgment
and aryltrifluoroborates in DMF and/or water, Eur. J. Org. Chem. 27 (2008)
567e4570.
4
[
22] M.S. Wong, X.L. Zhang, Ligand promoted palladium-catalyzed homo-coupling
We are thankful to the SAIF Panjab University, Chandigarh and
IISER, Bhopal for providing help in the analysis of the samples and
we also grateful to NTU, Singapore for the single crystal X-ray
analysis. Bhumika Agrahari, Samaresh Layek and Anuradha
acknowledge the receipt of IIT (ISM), Dhanbad fellowship.
of arylboronic acids, Tetrahedron Lett. 42 (2001) 4087e4089.
[23] A. Prastaro, P. Ceci, E. Chiancone, A. Boffi, G. Fabrizi, S. Cacchi, Homocoupling
of arylboronic acids and potassium aryltrifluoroborates catalyzed by protein-
stabilized palladium nanoparticles under air in water, Tetrahedron Lett. 51
(2010) 2550e2552.
[24] S. Carrettin, J. Guzman, A. Corma, Supported gold catalyzes the homocoupling
of phenylboronic acid with high conversion and selectivity, Angew. Chem. Int.
Ed. 44 (2005) 2242e2245.
Appendix A. Supplementary data
[
[
[
25] T. Volgler, A. Studer, Rhodium-catalyzed oxidative homocoupling of boronic
acids, Adv. Synth. Catal. 350 (2008) 1963e1967.
2 2
26] G.Y. Liu, Q.L. Du, J.J. Xie, K.L. Zhang, X.C. Tao, NiCl .6H O catalyzed homo-
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.molstruc.2016.12.053.
coupling of arylboronic acids, Chin. J. Catal. 27 (2006) 1051e1052.
27] J.R. Falck, S. Mohapatra, M. Bondlela, S.K. Venkataraman, Homocoupling of
alkyl-, alkenyl-, and arylboronic acids, Tetrahedron Lett. 43 (2002)
8
149e8151.
References
[
[
[
28] A.S. Demir, O. Reis, M. Emrullahoglu, Role of copper species in the oxidative
dimerization of arylboronic acids: synthesis of symmetrical biaryls, J. Org.
Chem. 68 (2003) 10130e10134.
29] N. Kirai, Y. Yamamoto, Homocoupling of arylboronic acids catalyzed by 1,10-
phenanthroline-ligated copper complexes in air, Eur. J. Org. Chem. (2009)
[
1] C.J. Li, Quasi-nature Catalysis: developing C-C bond formations catalyzed by
late transition metals in air and water, Acc. Chem. Res. 35 (2002) 533e538.
2] S. Layek, S. Kumari, B. Anuradha, B. Agrahari, R. Ganguly, D.D. Pathak, Syn-
thesis, characterization and crystal structure of a diketone based Cu(II) com-
plex and its catalytic activity for the synthesis of 1,2,3-triazoles, Inorg. Chim.
Acta 453 (2016) 735e741.
[
1864e1867.
30] B. Kaboudin, T. Haruki, T. Yokomatsu, CuSO4-mediated homocoupling of
arylboronic acids under ligand- and base-free conditions in air, Synthesis
[3] H. Prokopcov, C.O. Kappe, Copper-catalyzed C-C coupling of thiol esters and
(2011) 91e95.
boronic acids under aerobic conditions, Angew. Chem. Int. Ed. 47 (2008)
[
[
31] G. Cheng, M. Luo, Homocoupling of arylboronic acids catalyzed by CuCl in air
at room temperature, Eur. J. Org. Chem. (2011) 2519e2523.
32] B. Kaboudin, R. Mostafalu, T. Yokomatsu, Fe
3674e3676.
[
[
[
4] C.J. Li, Organic reactions in aqueous media with a focus on carbon-carbon
bond Formations: a decade update, Chem. Rev. 105 (2005) 3095e3166.
5] A. Corma, H. Garcia, F.X.L. Xamena, Engineering metal organic frameworks for
heterogeneous catalysis, Chem. Rev. 110 (2010) 4606e4655.
6] E. Jeong, W.R. Lee, D.W. Ryu, Y. Kim, W.J. Phang, E.K. Koh, C.S. Hong, Reversible
structural transformation and selective gas adsorption in a unique aqua-
bridged Mn(II) metal-organic framework, Chem. Commun. (2013)
3 4
O nanoparticle-supported Cu(II)-
b-cyclodextrin complex as a magnetically recoverable and reusable catalyst
for the synthesis of symmetrical biaryls and 1,2,3-triazoles from arylboronic
acids, Green Chem. 15 (2013) 2266e2274.
[
[
[
33] P. Puthiaraj, P. Suresha, K. Pitchumani, Aerobic homocoupling of arylboronic
acids catalysed by copper terephthalate metal-organic frameworks, Green
Chem. 16 (2014) 2865e2875.
2329e2331.
34] P.K. Raul, A. Mahanta, U. Bora, A.J. Thakur, V. Veer, In water homocoupling of
arylboronic acids using nano-rod shaped and reusable copper oxide(II) cata-
lyst at room temperature, Tetrahedron Lett. 56 (2015) 7069e7073.
35] S.A.R. Mulla, S.S. Chavan, M.Y. Pathan, S.M. Inamdar, T.M.Y. Shaikh, Ligand-,
base-, co-catalyst-free copper fluorapatite (CuFAP) as a versatile, ecofriendly,
heterogeneous and reusable catalyst for an efficient homocoupling of aryl-
boronic acid at ambient reaction conditions, RSC Adv. 5 (2015) 24675e24680.
36] D. Tyagi, C. Binnani, R.K. Rai, A.D. Dwivedi, K. Gupta, P.Z. Li, Y. Zhao, S.K. Singh,
Ruthenium-catalyzed oxidative homocoupling of arylboronic acids in water:
ligand tuned reactivity and mechanistic study, Inorg. Chem. 55 (2016)
[
[
[
7] K. Sumida, D.L. Rogow, J.A. Mason, T.M. McDonald, E.D. Bloch, Z.R. Herm,
T.H. Bae, J.R. Long, Carbon dioxide capture in metal-organic frameworks,
Chem. Rev. 112 (2012) 724e781.
8] N. Stock, S. Biswas, Synthesis of metal-organic frameworks (MOFs): routes to
various MOF topologies, morphologies, and composites, Chem. Rev. 112
(
2012) 933e936.
9] L. Alaerts, E. Seguin, H. Poelman, F.T. Starzyk, P.A. Jacobs, D.E. Devos, Probing
the lewis acidity and catalytic activity of the metal-organic framework
[
3
[Cu (btc)
2
]
(BTC¼Benzene-1,3,5-tricarboxylate), Chem. Eur. J. 12 (2006)
7353e7363.
6332e6343.
[
10] M. Yoon, R. Srirambalaji, K. Kim, Homochiral metal-organic frameworks for
asymmetric heterogeneous catalysis, Chem. Rev. 112 (2012) 1196e1231.
11] M.J. Beier, W. Kleist, M.T. Wharmby, R. Kissner, B. Kimmerle, P.A. Wright,
J.D. Grunwaldt, A. Baiker, Aerobic epoxidation of olefins catalyzed by the
cobalt-based metal-organic framework STA-12(Co), Chem. Eur. J. 18 (2012)
[
[
[
[
37] SMART Version 5.628, Bruker AXS Inc., Madison, WI, USA, 2001.
38] G.M. Sheldrick, SADABS, University of G o€ ttingen, G o€ ttingen, Germany, 1996.
39] SHELXTL Version 5.1, Bruker AXS Inc., Madison, WI, USA, 1997.
40] C. Pariya, F.L. Liao, S.L. Wang, C.S. Chung, Syntheses, crystal structure and solid
state thermochromism of copper (II) complexes of trans 1,2-
diaminocyclohexane, Polyhedron 17 (1998) 547e554.
[
887e898.
[
[
12] J.P. Corbet, G. Mignani, Selected patented cross-coupling reaction technolo-
gies, Chem. Rev. 106 (2006) 2651e2710.
13] N. Marion, O. Navarro, J. Mei, E.D. Stevens, N.M. Scott, S.P. Nolan, Modified
[
[
[
41] L. Fabbrizzi, M. Micheloni, P. Paoletti, Continuous and discontinuous ther-
mochromism of copper(II) and nickel(II) complexes with N,
N dieth-
ylethylenediamine, Inorg. Chem. 13 (1974) 3019e3021.
(
NHC)Pd(allyl)Cl (NHC
¼
N-Heterocyclic carbene) complexes for room-
42] N. Dege, G. Demirtas, H. Icbudak, trans-Bis(ethylenediamine-k2N,N )bis(6-
0
temperature suzuki-miyaura and Buchwald-Hartwig reactions, J. Am. Chem.
Soc. 128 (2006) 4101e4111.
6
methyl-2,2,4-trioxo-3,4-dihydro-1,2
ActaCryst 68 (2012) 47e48.
l
,3-oxathiazin-3-ido-kN)copper(II),
[
[
[
14] J. Hassan, M. Sevignon, C. Gozzi, E. Schulz, M. Lemaire, Aryl-aryl bond for-
mation one century after the discovery of the Ullmann reaction, Chem. Rev.
43] M. Lashanizadegan, S. Shayegan, M. Sarkheil, Copper(II) complex of (±)trans-
,2-cyclohexanediamine azo-linked Schiff base ligand encapsulated in the
nanocavity of zeolite-Y for the catalytic oxidation of olefins, J. Serb. Chem. Soc.
1 (2016) 153e162.
1
1
02 (2002) 1359e1470.
15] L. Monnereau, D. Semeril, D. Matt, L. Toupet, A. Motac, Efficient, nickel-
catalysed kumada-tamao-corriu cross-coupling with calix[4]arene-
8
a
[
[
[
44] M. Alias, H. Kassum, C. Shakir, Synthesis, physical characterization and bio-
logical evaluation of Schiff base M(II) complexes, J. Assoc. Arab Univ. Basic
Appl. Sci. 15 (2014) 28e34.
45] D.H. Johnston, D.F. Shiver, Vibrational study of the trifluoromethanesulfonate
anion: unambiguous assignment of the asymmetric stretching modes, Inorg.
Chem. 32 (1993) 1045e1047.
diphosphine ligand, J. Adv. Synth. Catal. 351 (2009) 1383e1389.
16] B. Mu, T. Li, Z. Fu, Y. Wu, Cyclopalladated ferrocenylimines catalyzed-
homocoupling reaction of arylboronic acids in aqueous solvents at room
temperature under ambient atmosphere, Catal. Commun. 10 (2009)
1497e1501.
[
17] S. Mori, M. Nagata, Y. Nakahata, K. Yasuta, R. Goto, M. Kimura, M. Taya,
Enhancement of incident photon-to-current conversion efficiency for
phthalocyanine-sensitized solar cells by 3D molecular structuralization, J. Am.
Chem. Soc. 132 (2010) 4054e4055.
46] S. Kumari, A. Shekhar, D.D. Pathak, Synthesis and characterization of a Cu(II)
Schiff base complex immobilized on graphene oxide and its catalytic appli-
cation in the green synthesis of propargylamines, RSC Adv.
5340e15344.
6 (2016)
1
[
[
[
[
18] M.M. Manas, M. Perez, R. Pleixats, Palladium-catalyzed suzuki-type self-
[
47] P. Sureshbabua, A.A.J.S. Tjakraatmadjab, C. Hanmandlua, K. Elavarasana,
Mononuclear Cu(II) and Zn(II) complexes with a simple diamine ligand:
synthesis, structure, phosphodiester binding and DNA cleavage studies, RSC
Adv. 5 (2015) 22405e22418.
48] V.P. Singh, Synthesis, electronic and ESR spectral studies on copper(II) nitrate
complexes with some acylhydrazines and Hydrazones, spectrochim, Acta, Part
A 71 (2008) 17e22.
49] C. Bodhak, A. Kundu, A. Pramanik, An efficient and recyclable chitosan sup-
ported copper(II) heterogeneous catalyst for C-N cross coupling between aryl
halides and aliphatic diamines, Tetrahedron Lett. 56 (2015) 419e424.
coupling of arylboronic acids. A mechanistic study, J. Org. Chem. 61 (1996)
2346e2351.
19] K. Mitsudo, T. Shiraga, H. Tanaka, Electrooxidative homo-coupling of aryl-
boronic acids catalyzed by electrogenerated cationic palladium catalysts,
Tetrahedron Lett. 49 (2008) 6593e6595.
[
[
20] K. Cheng, B. Xin, Y. Zhang, The Pd(OAc)
boronic acids in water and ionic liquid, J. Mol. Catal. A Chem. 273 (2007)
40e243.
21] C. Amatore, C. Cammoun, A. Jutand, Pd(OAc)
anaerobic electrooxidative homocoupling of arylboronic acids, arylboronates
2
-catalyzed homocoupling of aryl-
2
2
/p-Benzoquinone-Catalyzed