Copper complexes bearing C-scorpionate ligands: Synthesis, characterization and catalytic activity for azide-alkyne cycloaddition in aqueous medium

Article abstract of DOI:10.1016/j.ica.2018.08.052

Reactions of CuX (X = Br or I) and [Cu(MeCN)₄][BF₄] with the neutral C-scorpionates HC(3,5-Me₂pz)₃ and HC(3-Phpz)₃ (Tpm^? and Tpm^Ph, respectively) proceed readily at room temperat

Full text of DOI:10.1016/j.ica.2018.08.052

InorganicaChimicaActa483(2018)371–378
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Copper complexes bearing C-scorpionate ligands: Synthesis,
characterization and catalytic activity for azide-alkyne cycloaddition in
aqueous medium
Abdallah G. Mahmouda,b, Luísa M.D.R.S. Martinsa,⁎, M. Fátima C. Guedes da Silvaa,⁎
,
Armando J.L. Pombeiroa
a
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa Av. Rovisco Pais, 1049-001 Lisboa, Portugal
b
Department of Chemistry, Faculty of Science, Helwan University, Ain Helwan, 11795 Cairo, Egypt
A R T I C L E I N F O
A B S T R A C T
Keywords:
Copper
Reactions of CuX (X = Br or I) and [Cu(MeCN)4][BF4] with the neutral C-scorpionates HC(3,5-Me2pz)3 and
HC(3-Phpz)3 (Tpm∗ and TpmPh, respectively) proceed readily at room temperature to give the neutral copper(I)
complexes [CuBr(TpmPh)] (1), [CuI(TpmPh)] (2), [CuBr(Tpm∗)] (3), [CuI(Tpm∗)] (4) and the cationic [Cu
(TpmPh)(NCMe)][BF4] (5), [Cu(Tpm∗)(NCMe)][BF4] (6) and [Cu(Tpm∗)2][BF4]2 (7), the latter also obtained
from 6 after some time in air. Compounds 1–7 act as homogeneous catalysts for the low-power microwave-
assisted three component (alkyne, bromobenzyl, sodium azide) cycloaddition reaction (CuAAC) to afford 1,4-
disubstituted-1,2,3-triazoles, with 7 as the best catalyst. The catalytic reaction evolves well in ROH/H2O solu-
tion, depends on the R group and proceeds better when R = Me, here achieving yields up to 94%. The alcohol
plays a role in the Cu(II)-to-Cu(I) Glaser-type induction period, therefore avoiding a reducing agent in the
system.
C-scorpionate
Click chemistry
Aqueous medium
Cycloaddition
Catalysis
Triazoles
1. Introduction
a ligand [16,19], (b) electrochemically generated Cu(I) species [20], (c)
supported Cu(I) on an immobilized phase [21,22], (d) Cu-containing
Copper species play a very essential role in several enzymes and
catalytic systems, which leads to a significant interest to develop new
copper models for catalysis [1–4]. Among the most interesting copper
species applications in catalysis is the copper catalyzed azide-alkyne
cycloaddition reaction (CuAAC, Scheme 1). Since its discovery [5,6],
this reaction has become the most genuine example of “click chemistry”
[7] and constituted a powerful tool for the synthesis of 1,2,3-triazoles
with growing applications in materials science, molecular biology,
polymer and medicinal chemistry [8–10].
Due to the explosive nature of organic azides, their isolation and
purification can be problematic [11,12]. Therefore, intensive attention
has been devoted to a new one-pot procedure of three components
reaction (alkyne, organic halide and sodium azide) [13–16], which
involves in-situ generation of organo azides followed by addition to an
alkyne to produce the corresponding 1,2,3-triazole (Scheme 2).
The most common procedure for CuAAC is the in situ generation of
Cu(I) from a mixture of Cu(II) salt (e.g., CuSO4) and sodium ascorbate as
reducing agent in aqueous medium [6,17,18]. Other catalytic systems
have been developed including the use of (a) Cu(I) salts with addition of
nanoparticles [23] and, to a lower extent, (e) well-defined Cu(I) com-
plexes [15,24–31] where the main role of the ligand is to stabilize the
Cu(I) centres. In this respect, tris(triazoles) [15,24], phosphines
[25–28], tetramines [29], and N-heterocyclic carbenes [30,31] are
successfully used ligands under different conditions.
In 2006 [32], Kantam et al. reported the first example of using so-
lely a Cu(II) salt (i.e., Cu(OAc)2, OAc = acetate) without reducing
agents or additional bases for the CuAAC reaction, in aqueous medium,
and postulated a direct participation of Cu(II) in the catalytic process.
Considering the extremely high efficiency of Cu(I) for the CuAAC re-
action at less than 0.01 equiv., as well as many studies providing the
essentiality of the presence of Cu(I) for the catalysis process
[5,6,25,26,29–31,17–24], it is more persuasive to ascribe catalysis to
small amounts of Cu(I) present or somehow generated in the reaction
mixture. Brotherton et al. [33] suggested that, in the presence of Cu(II),
Cu(I) may be generated during an oxidative homocoupling of terminal
alkynes (Eq. (1)), the process then pursuing as Glaser reaction [34].
This assumption has been confirmed by several spectroscopic, me-
chanistic and computational studies on different Cu(II) salts and
⁎
Corresponding authors.
E-mail address: luisammartins@tecnico.ulisboa.pt (L.M.D.R.S. Martins).
https://doi.org/10.1016/j.ica.2018.08.052
Received 10 July 2018; Received in revised form 23 August 2018; Accepted 27 August 2018
Availableonline29August2018
0020-1693/©2018ElsevierB.V.Allrightsreserved.

A.G. Mahmoud et al.
InorganicaChimicaActa483(2018)371–378
in a few hours, a colour which is typical of a Cu(II) derivative. Com-
plexes 1–4 are soluble in MeCN, CH2Cl2 and DMSO, 3 and 4 also having
good solubilities in MeOH. They present a half-sandwich structure with
one κN3-coordinated TpmPh (1, 2) or Tpm* (3, 4) ligand, their for-
mulations being confirmed by spectroscopic and analytical data (see
below). The structures of 1 and 4 have also been established by single
crystal X-ray diffraction. However, since the structure of the former is of
very low quality (see Supplementary Information) and the structure of
4 has already been reported [46], none will be discussed.
Scheme 1. Copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction.
The coordination of TpmPh and Tpm* ligands to the Cu(I) centre in
1–4 was confirmed by the downfield shift of resonances for the pyr-
azolyl ring protons of the ligands in their 1H NMR spectra (see the
Experimental Section, and Figs. S1 and S2). Both their 1H NMR and 13
C
Scheme 2. Three components catalyzed CuAAC reaction.
NMR spectra show the equivalence of the three pyrazolyl rings by ex-
hibiting a single resonance for each type of protons or carbons, ac-
cording to the N,N,N– coordination mode to the Cu(I) centre. The IR
spectra of the compounds exhibit a set of bands with diverse intensities
typical of TpmPh and Tpm* ligands [42,48], in particular the C]N
stretching vibrations at 1532, 1524, 1562 and 1557 cm−1. The co-
ordination of the halide (Br− or I−) was confirmed by the typical bands
complexes, clearly revealing that Cu(I) species are generated in a short
induction period from alkyne-alkyne homocoupling [33,35,36].
Thereafter, Cu(II) salts [37] or complexes [35,38,39] and immobilized
Cu(II) species [36,40] have been successfully applied for reducing
agents free ACC reaction.
(1)
Since the discovery of tris(pyrazol-1-yl)methane (Tpm) compounds
(C-scorpionates) [41] and the improvement of their synthetic proce-
dures [42,43], a significant number of copper complexes bearing these
ligands have been synthesized, used as catalysts for several processes
and, most notably, in CeH bond activation methods [44]. Due to the
ability of Tpm ligands to form stable copper complexes [45–49], they
would be promising candidates for CuAAC processes. However, to our
knowledge, the reported CuAAC processes catalyzed by Cu-Tpm com-
pounds is limited to just one Cu(I) example [50]. Herein we report the
catalytic performance of well-defined Cu(I) and Cu(II) complexes with
Tpm ligands, viz tris(3,5-dimethyl-1-pyrazolyl)methane, HC(3,5-
Me2pz)3 or Tpm*, and tris(3-phenylpyrazolyl)methane, HC(3-Phpz)3 or
TpmPh, (pz = pyrazol-1-yl; Fig. 1) for three-components CuAAC pro-
cess. The microwave assisted efficiency of such catalytic systems was
also investigated, confirming the already proven [14,15] great increase
of the CuAAC reaction rate under such experimental conditions.
in the 213–224 cm−1 range.
ESI(+)MS spectra for 1–4 were obtained in acetonitrile solution,
showing in all cases the base peak corresponding to the
[M − X + MeCN]+ fragment.
Reaction of [Cu(MeCN)4][BF4] with TpmPh in air, under mild con-
ditions, yields the Cu(I) complex [Cu(TpmPh)(NCMe)][BF4] (5)
(Scheme 4). By mixing equimolar amounts of [Cu(MeCN)4][BF4] and
Tpm* in degassed CH2Cl2, under inert N2-atmosphere, [Cu(Tpm*)
(NCMe)][BF4] (6) was afforded as an off-white powder in high yield
(Scheme 4, route 1). Compound 6 is stable as a solid in air, but is un-
stable in solution as it is oxidized to the green coloured Cu(II) complex
[Cu(Tpm*)2][BF4]2 (7) in a few hours (Scheme 4). Compound 7 can also
be obtained following the same procedure as for compound 6 synthesis,
using CH2Cl2 solvent in open air (Scheme 4, route 2). This compound
has already initially been obtained [51] following a 1:2 reaction of the
2. Results and discussion
Reaction of Cu(I) bromide or iodide with TpmPh or Tpm* in an
equimolar amount proceeds readily at room temperature to give the
respective [CuBr(TpmPh)] (1), [CuI(TpmPh)] (2), [CuBr(Tpm*)] (3) and
[CuI(Tpm*)] (4) colourless complexes in good yield (Scheme 3). Com-
plexes 1, 2 and 4 are air stable both in solid state and in solution, but 3
is stable in air only in the solid state since its solution changes to green
Fig. 1. Structures of C-scorpionate ligands employed in this work: (a) tris(3-
phenylpyrazolyl)methane HC(3-Phpz)3 (pz = pyrazol-1-yl), TpmPh; (b) tris(3,5-
dimethyl-1-pyrazolyl)methane HC(3,5-Me2pz)3, Tpm*.
Scheme 3. Synthesis of Cu(I) complexes [CuBr(TpmPh)] (1), [CuI(TpmPh)] (2),
[CuBr(Tpm*)] (3) and [CuI(Tpm*)] (4).
372

A.G. Mahmoud et al.
InorganicaChimicaActa483(2018)371–378
entries 7, 11–13, Fig. 2-b).
The effect of temperature has also been studied (Table 1, entries 7
and 14–16). With 10 W of microwave power, raising the temperature
from 75 °C up to 125 °C increased the yield from 78% to 88% (Table 1,
entries 7, 14 and 15). Higher temperature of 150 °C resulted in di-
minished yield of 84% (Table 1, entry 16).
The reaction was also carried out in various solvents used in-
dividually (Table 1, entries 17–21) or as 1:1 mixtures with water
(Table 1, entries 22–25), the former giving significant lower product
yields than the latter. Since water is necessary to dissolve NaN3 and the
organic solvent is vital for solubilization of the other reactants as well
as the catalyst, using mixtures of water and an organic solvent enhance
the homogeneity of the reaction system and the efficiency of the cata-
lysis. When mixtures of water with different alcohols were employed
(Table 1, entries 22–25), the obtained yields using oxidizable alcohols
(i.e., iPrOH, EtOH or MeOH) are higher than that obtained using tBuOH.
According to the literature [33,52], the presence of oxidizable alcohols
may enhance the reduction of Cu(II) to Cu(I) species (the Glaser in-
duction period), which is necessary for the catalytic CuAAC reaction to
proceed (Eq. (2)).
(2)
Consequently, the best experimental conditions for the three-com-
ponent CuAAC reaction to afford 1,4-disubstituted-1,2,3-triazoles in-
volve using 1.5 mol% of Cu(II)-compound 7 as pre-catalyst, in (1:1)
H2O:MeOH mixtures, under microwave irradiation at 125 °C in air for
30 min. Using these conditions, the scope of our catalytic system with 7
as pre-catalyst for one-pot three-component cycloaddition reaction was
expanded to several other terminal alkynes (Table 2). In all cases, the
reaction proceeded to afford the corresponding triazoles with yields
ranging from 68 to 95%.
Scheme 4. Synthesis of compounds [Cu(TpmPh)(NCMe)][BF4] (5), [Cu(Tpm*)
(NCMe)][BF4] (6) and [Cu(Tpm*)2][BF4]2 (7).
Cu(BF4)2 hydrated salt and Tpm*. Compounds 5–7 display a good so-
lubility in MeOH, DMSO, MeCN, and chlorinated solvents such as
CH2Cl2 and CHCl3.
The cationic complexes 5–7 were characterized by ESI-MS spec-
trometry, elemental analysis, FT-IR and NMR (1H and 13C{1H}, except
for 7) spectroscopies, which support the proposed formulations (see
experimental section) and the results are consistent with the data al-
Complex 7 displays a relatively high activity for the CuAAC reaction
as, e. g., a yield up to 94% could be achieved in water:methanol medium
under microwave irradiation (table 1, entry 25), which is similar to
other reported catalytic systems [14,15]. However, our experimental
conditions are comparatively milder since only 10 W MW radiation was
used, in a relatively short reaction time (30 min.) and in the absence of
reduction agents. In addition, our complex reveals a higher selectivity
when compared to a reported system for catalytic AAC reaction be-
tween phenylacetylene and N-sulfonyl azide using a Cu(I)-Tpm*Br
complex [Tpm*Br = HC(4-Br-3,5-Me2pz)3] [50]. Yet, in this case,
chloroform was used as solvent and tosylamide was a byproduct the
concentration of which increased considerably upon addition of water.
By analogy with previous reports [6,17], a plausible mechanism for
the Cu(II)-catalyzed cycloaddition to the synthesis of 1,2,3-triazoles is
depicted in Scheme 5. The reaction begins with Cu(II) promoted alkyne-
alkyne homocoupling to generate the Cu(I) catalytic active species [34].
Then the reaction proceeds in a stepwise manner as described by
Sharpless and coworkers [6], which involves the coordination of the
alkyne to the Cu(I) species to form the Cu(I)-acetylenide complex, fol-
lowed by its cyclization with the in situ generated organic azide to
produce the Cu(I)-tryazolyl intermediate. Finally, the 1,4-disubstituted
1,2,3-triazole product is afforded by protonation of the the Cu(I)-trya-
zolyl intermediate to complete the catalytic cycle.
ready reported when [PF6]− is the counter anion (i.e., [Cu(TpmPh
)
(NCMe)][PF6] and [Cu(Tpm*)(NCMe)][PF6]) [47]. The crystal struc-
ture of 7 agreed with the already established one [51].
Azide-alkyne cycloaddition in aqueous-three component catalytic
system
The catalytic performances of compounds 1–7 were investigated
towards the three component CuAAC reaction. Under low power (10 W)
microwave (MW) irradiation and in homogeneous conditions, taking
the reaction between phenylacetylene, benzyl bromide and sodium
azide to afford 1-benzyl-4-phenyl-1H-1,2,3-triazole as a model (see
Table 1, inset reaction). The reaction product could be easily isolated by
filtration and no byproducts were identified. In order to optimize the
reaction conditions a series of experiments was performed to study the
influence of variables such as type and amount of catalyst, solvent and
reaction time (Table 1).
The catalytic reactivity of compounds 1–7 for the indicated CuAAC
reaction was initially tested (Table 1, entries 1–7), using 1.5 mol% of
catalyst, in water:MeCN (1:1) mixture, under MW irradiation (10 W) for
30 min, to produce 1-benzyl-4-phenyl-1H-1,2,3-triazole as unique pro-
duct with yield in the 18–88% range. Compound 7 revealed the highest
activity and was thus used for the optimization of the reaction condi-
tions.
3. Conclusions
Increasing the catalyst loading from 0.5 mol% to 1.5 mol% raised
the isolated yield sharply from 36% to 88% (Table 1, compare entries 7
and 8). However, a further increase in the amount of catalyst did not
have a significant effect on the yield (Table 1, entries 9 and 10, Fig. 2-
a). Extending the reaction time from 15 to 30 min increased the yield
from 56% to 88%, and no significant change in yield was observed with
further extending the reaction time up to 90 min (Table 1, compare
A set of well-defined scorpionate copper complexes 1–7 were pre-
pared by direct reaction of commercially available Cu(I) salts with
neutral HC(3,5-Me2pz)3 (Tpm*) and HC(3-Phpz)3 (TpmPh) under mild
conditions. The possibility of employing such complexes as catalyst
precursors for the three-component (alkyne, organic halide and sodium
azide) CuAAC in aqueous medium was investigated. The obtained
copper complexes, in particular [Cu(Tpm*)2][BF4]2 (7), act as
373

A.G. Mahmoud et al.
InorganicaChimicaActa483(2018)371–378
Table 1
Three-component catalytic CuAAC reaction of phenylacetylene, benzyl bromide and sodium azide to produce 1-benzyl-4-phenyl-1H-1,2,3-triazole, under microwave
irradiation, catalyzed by 1–7.a
Entry
Catalyst
Cat. loadb
(mol%)
Solvent
Temperature
(oC)
Time (min)
Yieldc (%)
TONd
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
1.5
1.5
1.5
1.5
1.5
1.5
1.5
0.5
3
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
H2O:MeCN
DMSO
125
125
125
125
125
125
125
125
125
125
125
125
125
75
100
150
125
125
125
125
125
125
125
125
125
30
30
30
30
30
30
30
30
30
30
15
60
90
30
30
30
30
30
30
30
30
30
30
30
30
18
22
64
81
65
27
88
36
90
90
56
89
89
78
79
84
14
17
22
27
63
82
87
89
94
12
15
42
54
43
18
59
73
30
18
37
59
59
52
52
56
9
11
15
18
42
55
58
59
63
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
DMF
MeCN
MeOH
H2O
H2O:tBuOH
H2O:iPrOH
H2O:EtOH
H2O:MeOH
a
Reaction conditions: phenylacetylene (0.33 mmol), benzyl bromide (0.3 mmol, limiting reactant), sodium azide (0.33 mmol), 1.5 mL of solvent (1:1 in case of
solvent mixtures), MW irradiation (10 W), 125 °C.
b
Calculated on the basis of benzyl bromide.
Isolated yield; calculated on the basis of benzyl bromide.
Number of moles of product (1-benzyl-4-phenyl-1H-1,2,3-triazole) per mol of catalyst.
c
d
homogeneous catalysts for the reaction under low power (10 W) mi-
crowave irradiation to afford, in 30 min., the 1,4-disubstituted-1,2,3-
triazoles in pure form with yields up to 94%.
4. Experimental
4.1. General procedures and instrumentation
A comparison of our catalytic system with already reported similar
ones proved that it was highly efficient under milder conditions and in
the absence of added reducing agent. In addition, it also showed that
the properties of the C-scorpionate compounds are easily tunable and
their usage as ligands can contribute for the optimization of the cata-
lytic behaviour of their metal complexes, a research route that deserves
to be further explored.
All operations were carried out in open air, unless stated otherwise.
All solvents and reagents were obtained from commercial sources and
used without further purifications. Tris(3-phenylpyrazoyl)methane
[42], tris(3,5-dimethyl-1-pyrazoyl)methane [48] and complex 4 [46]
were prepared according to literature procedures. Synthesis under mi-
crowave irradiation were carried out in an Anton Paar (Monowave 300)
apparatus. The reactions were performed in 10 mL cylindrical pyrex
Fig. 2. Plots of yields of 1-benzyl-4-phenyl-1H-1,2,3-triazole vs. catalyst amount (a) and reaction time (b) for the CuAAC reaction in (1:1) water:MeCN mixtures using
1.5 mol% of catalyst 7 at 125 °C under microwave irradiation (10 W).
374

A.G. Mahmoud et al.
InorganicaChimicaActa483(2018)371–378
Table 2
One-pot multicomponent catalytic cycloaddition of benzyl bromide with several terminal alkynes and NaN3 catalyzed by 7 under optimized reaction conditions.a
Entry
1
Alkyne
Product
Yieldb
72
TONc
48
2
3
78
68
52
45
4
79
86
95
53
57
63
5
6d
a
Reaction conditions: alkyne (0.33 mmol), benzyl bromide (0.3 mmol, limiting reactant), sodium azide (0.33 mmol), 1.5 mL of solvent (H2O:MeOH, 1:1), under
MW irradiation (10 W) at 125 °C, 30 min.
b
Isolated yield; calculation based on benzyl bromide.
Number of moles of the 1,2,3-triazole product per mol of catalyst.
Benzyl bromide (0.6 mmol, limiting reactant), 1,4-diethynylbenzene (0.33 mmol) and sodium azide (0.62 mmol).
c
d
reported in δ (ppm). All spectra were internally referenced to residual
protio-solvent resonance and are reported relative to SiMe4.
Assignments of some 1H and 13C signals rely on g-COSY and g-HSQC
experiments. Elemental analyses (C, H, and N) were obtained by the
microanalytical services of the Instituto Superior Técnico. Infrared
spectra (4000–400 cm−1) were obtained in a Cary 630 FTIR spectro-
meter; wavenumbers are in cm−1; abbreviations: s, strong; m, medium;
w, weak. Far infrared spectra (400–180 cm−1) were recorded on a
Vertex 70 spectrophotometer in CsI pellets. Electrospray mass spectra
(ESI-Ms) were obtained on a Varian 500- MS LC Ion Trap Mass spec-
trometer equipped with an electrospray ion source. For electrospray
ionization, the drying gas and flow rate was optimized according to the
particular sample with 35p.s.i. nebulizer pressure. The scanning was
performed from m/z 100–1200 in acetonitrile solution. All compounds
were observed in the positive mode (capillary voltage = 80–105 V).
4.2. Synthesis of complexes 1 and 2
In a round bottom flask, copper(I) halide (0.1 mmol, CuBr for 1 or
CuI for 2) was dissolved in 2 mL of MeCN. Under continuous stirring, a
5 mL MeCN:EtOH (3:2) solution of HC(3-PhPz)3 (0.11 mmol, 50 mg)
was added dropwise. The produced light brown solution was stirred at
room temperature for 3 h, then its volume was reduced by evaporation
Scheme 5. Postulated mechanism of the Cu(II) catalyzed reaction.
Bn = Benzyl.
to ca. 2 mL. Hexane (10 mL) was added and the obtained precipitate
was filtered off, recrystallized from a mixture of CH2Cl2 and hexane
(1:1) to afford complexes 1 or 2 as colourless crystals.
[CuBr(TpmPh)] (1): Yield (45.9 mg) 78%. Elemental analysis calcd
tubes, sealed using a teflon crimp top. After the reaction, the vail was
cooled rapidly to ambient temperature by gas jet cooling.
(%) for C28H22BrCuN6·CH2Cl2: C 51.92, H 3.61, N 12.53; found: C
51.51, H 3.70, N 12.64. FTIR (KBr): ν (cm−1) = 1532 m, 1491 w,
1442 m, 1391 w, 1342 w, 1324 w, 1299 w, 1268 w, 1242 m, 1209 m,
1H and 13C NMR spectra were obtained using a Bruker Advance
300 MHz spectrometer, at ambient temperature. All chemical shifts are
375

A.G. Mahmoud et al.
InorganicaChimicaActa483(2018)371–378
1095 m, 1077 m, 1038 m, 798 m, 756 s, 688 s. Far IR (CsI):
ν
4.5. Synthesis of compound 6
(cm−1) = 221 m ν(Cu-Br). 1H NMR (300 MHz, DMSO‑d6, δ): 9.10 (s,
1H, HC(3-PhPz)3), 8.11 (br, 3H, 5-H-pz), 7.85 (br, 6H, o-H-Ph), 7.42
(br, 9H, m,p-H-Ph), 6.95 (br, 3H, 4-H-pz). 13C{1H} NMR (300 MHz,
DMSO‑d6, δ): 152.14 (3-C-pz), 132.20 (Cquat-Ph), 131.82 (5-C-pz)),
128.76 (m-C-Ph), 128.32 (p-C-Ph), 125.53 (o-C-Ph), 104.57 (4-C-pz),
82.09 (HC(3-Phpz)3). ESI(+)MS in MeCN (m/z assignment, % in-
Under a N2-atmosphere, a round bottom flask was charged with [Cu
(MeCN)4][BF4] (0.33 mmol, 0.1 g), HC(3,5-Me2Pz)3 (0.33 mmol, 0.1 g)
and 2 mL of degassed CH2Cl2. The produced yellow solution was stirred
under N2 at room temperature for 3 h, then 10 mL of hexane were
added, and the obtained precipitate was filtered off and washed re-
peatedly with hexane to afford 6 as an off-white powder.
tensity): 546 ({[HC(3-Phpz)3]Cu + MeCN}+
Phpz)3]Cu}+, 23).
, 100), 505 ({[HC(3-
[Cu(Tpm*)(NCMe)][BF4] (6): Yield (140.1 mg) 87%. Elemental
analysis calcd (%) for C18H25BCuF4N7: C 44.14, H 5.14, N 20.02; found:
C 44.63, H 5.41, N 19.86. FTIR (KBr): ν (cm−1) = 3582 m, 2962 m,
2928 m, 1559 m, 1450 m, 1412 m, 1389 m, 1300 s, 1245 s, 1032 s,
894 m, 847 s, 802 m, 698 s. 1H NMR (300 MHz, DMSO‑d6, δ): 7.84 (s,
1H, HC(3,5-Me2pz)3), 6.14 (s, 3H, 4-H-pz), 2.43, 2.24 (s, s, 9H, 9H, 3,5-
Me), 2.09 (s, 3H, NCCH3). 13C{1H} NMR (300 MHz, DMSO‑d6, δ):
149.62 (3-Cquat-pz), 140.71 (5-Cquat-pz), 115.31 (NCCH3), 106.37 (4-C-
pz), 70.24 (HC(3,5-Me2pz)3), 14.20,10.74 (3,5-Me), 1.27 (NCCH3). ESI
[CuI(TpmPh)] (2). Yield (51.7 mg) 82%. Elemental analysis calcd
(%) for C28H22CuIN6: C 53.13, H 3.50, N 13.28; found: C 52.84, H 3.62,
N 12.78. FTIR (KBr): ν (cm−1) = 1525 m, 1496 w, 1450 m, 1398 w,
1352 w, 1323 w, 1302 w, 1277 w, 1239 m, 1202 m, 1098 m, 1072 m,
1046 m, 796 m, 752 s, 692 s. Far IR (CsI): ν (cm−1) = 224 m ν(Cu-I). 1H
NMR (300 MHz, DMSO‑d6, δ): 9.10 (s, 1H, HC(3-Phpz)3), 8.12 (d,
JHH = 3 Hz, 3H, 5-H-pz), 7.86 (m, 6H, o-H-Ph), 7.43 (m, 6H, m-H-Ph),
7.34 (m, 3H, p-H-Ph), 6.96 (d, 3H, JHH = 3 Hz, 4-H-pz). 13C{1H} NMR
(300 MHz, DMSO‑d6, δ): 152.13 (3-C-pz), 132.19 (Cquat-ph), 132.07 (5-
C-pz), 128.75 (m-C-Ph), 128.32 (p-C-Ph), 125.52 (o-C-Ph), 104.56 (4-C-
pz), 82.09 (HC(3-Phpz)3). ESI(+)MS in MeCN (m/z assignment, % in-
(+)MS in MeCN (m/z assignment,
% intensity): 402 ({[HC(3,5-
Me2pz)3]Cu(MeCN)}+, 100), 361 ({[HC(3,5-Me2pz)3]Cu}+, 31).
tensity): 546 ({[HC(3-Phpz)3]Cu + MeCN}+
Phpz)3]Cu}+, 10).
,
100), 505 ({[HC(3-
4.6. Synthesis of compound 7
A
round bottom flask was charged with [Cu(MeCN)4][BF4]
4.3. Synthesis of complex 3
(0.33 mmol, 0.1 g), HC(3,5-Me2Pz)3 (0.33 mmol, 0.1 g) and 2 mL
CH2Cl2 and stirred in open air, at room temperature, overnight. 2 mL of
MeOH were then added to the produced green solution and left for slow
evaporation in open air. Green crystals of 7 suitable for single crystal X-
ray diffraction analysis were obtained after 2 days.
In a round bottom flask, copper(I) bromide (0.3 mmol, 0.043 g) was
dissolved in 5 mL of degassed MeCN. Under continuous stirring and in a
N2-atmosphere, a 2 mL degassed NCMe solution of HC(3,5-Me2pz)3
(0.33 mmol, 0.1 g) was added dropwise. The mixture was stirred at
room temperature for 3 h, then its volume was reduced to ca. 2 mL by
evaporation. Hexane (10 mL) was added, and the obtained precipitate
was filtered off and recrystallized from a mixture if CH2Cl2 and hexane
(1:1) to afford complexes 3 as off-white powder.
[Cu(Tpm*)2][BF4]2 (7): Yield (103.4 mg) 38%. Elemental analysis
calcd (%) for C32H44B2CuF8N12: C 46.09, H 5.32, N 20.16; found: C
45.90, H 5.16, N 19.75. FTIR (KBr): ν (cm−1) = 3141 w, 2923 w, 2966
w, 1561 m, 1460 m, 1444 m, 1413 m, 1386 m, 1312 m, 1257 m, 1027 s,
906 m, 855 s, 816 m, 699 s. ESI(+)MS in MeCN (m/z assignment, %
[CuBr(Tpm*)] (3): Yield (108.9 mg) 82%. Elemental analysis calcd
(%) for C16H22BrCuN6: C 43.49, H 5.02, N 19.02; found: C 43.45, H
5.51, N 19.62. FTIR (KBr): ν (cm−1) = 3397 m, 2962 m, 2925 m,
1562 s, 1455 s, 1412 s, 1383 s, 1303 s, 1239 s, 1153 w, 1112 w, 1035 m,
intensity): 745 ({[HC(3,5-Me2pz)3]2Cu[BF4]}+
, 100). The crystal
structure of the compound agrees with the already reported one [51].
4.7. General procedure for three-component azide alkyne cycloaddition
reaction
980 m, 905 m, 845 s, 824 m, 796 m, 695 s. Far IR (CsI):
ν
(cm−1) = 216 m ν(Cu-Br). 1H NMR (300 MHz, DMSO‑d6, δ): 7.83 (s,
1H, HC(3,5-Me2pz)3), 6.04 (s, 3H, 4-H-pz), 2.40, 2.22 (s, s, 9H, 9H, 3,5-
Me). 13C{1H} NMR (300 MHz, DMSO‑d6, δ): 149.12 (3-Cquat-pz), 140.28
(5-Cquat-pz), 106.44 (4-C-pz), 70.67 (HC(3,5-Me2pz)3), 13.48,10.37
(3,5-Me). ESI(+)MS in MeCN (m/z assignment, % intensity): 204
A mixture of benzyl bromide (0.3 mmol, 1 equiv.), acetylene deri-
vative (0.33 mmol, 1.1 equiv.), NaN3 (0.33 mmol, 1.1 equiv.) and
1.5 mL of solvent was charged to a 10 mL pyrex vial equipped with a
magnetic stirring bar. The catalyst (0.5–5 mol%) was then added, the
vial tightly sealed, placed in the microwave reactor and irradiated
(10 W) at 125 °C for the periods of time indicated in Tables 1 and 2. A
precipitate was formed, the reaction mixture was cooled to ambient
temperature and 5 mL of water were added to force a complete pre-
cipitation of the triazole product. The product was filtered off, washed
repeatedly with petroleum ether and dried in vacuum.
({[HC(3,5-Me2pz)3]Cu + MeCN}+
Me2pz)3]Cu}+, 26).
,
100),
361
({[HC(3,5-
4.4. Synthesis of compound 5
A
round bottom flask was charged with [Cu(MeCN)4][BF4]
(0.12 mmol, 0.038 g), HC(3-PhPz)3 (0.11 mmol, 50 mg) and 2 mL of
CH2Cl2. The produced yellow solution was stirred at room temperature
for 1 h, then 10 mL of hexane were added and the obtained precipitate
was filtered off and recrystallized from a mixture of CH2Cl2 and hexane
(1:1) to afford 5 as an off-white powder.
1,4-bis(1-benzyl-1H-1,2,3-triazol-4-yl)benzene (Table 2, entry 6)
was prepared according to the general procedure described above ex-
cept 0.6 mmol of benzyl bromide, 0.33 mmol of 1,4-diethynylbenzene
and 0.62 mmol of sodium azide were used.
The 1H and 13C NMR spectroscopic data of all 1,2,3-triazol products
are in agreement with those already reported [14,25,29,53–56].
[Cu(TpmPh)(NCMe)][BF4] (5): Yield (61 mg) 80%. Elemental
analysis calcd (%) for C30H25BCuF4N7: C 56.84, H 3.98, N 15.47; found:
C 55.91, H 4.14, N 14.97. FTIR (KBr): ν (cm−1) = 1531 m, 1496 m,
1462 m, 1430 m, 1367 m, 1341 m, 1300 w, 1280 w, 1237 s, 1070 s,
1012 s, 856 m, 796 s, 752 s, 686 s. 1H NMR (300 MHz, DMSO‑d6, δ):
9.18 (s, 1H, HC(3-Phpz)3), 8.16 (s, 3H, 5-H-pz), 7.86 (m, 6H, o-H-Ph),
7.43 (m, 9H, m,p-H-Ph), 6.95 (s, 3H, 4-H-pz), 2.06 (s, 3H, NCCH3).
Acknowledgements
This work has been partially supported by the Fundação para a
Ciência e a Tecnologia, Portugal (FCT), (UID/QUI/00100/2013 and
PTDC/QEQ-ERQ/1648/2014), Portugal. A. G. M. is thankful to the
CATSUS doctoral program of FCT for his PhD fellowship (SFRH/BD/
106006/2014). The authors acknowledge the Portuguese NMR
Network (IST-UL Centre) for access to the NMR facility and the IST
Node of the Portuguese Network of Mass-spectrometry for the ESI-MS
measurements.
13C{1H} NMR (300 MHz, DMSO‑d6, δ): 151.89 (3-C-pz), 132.04 (Cquat
-
ph), 131.41 (5-C-pz), 128.26 (m-C-Ph), 128.01 (p-C-Ph), 125.23 (o-C-
Ph), 115.05 (NCCH3), 104.20 (4-C-pz), 80.88 (HC(3-Phpz)3), 1.44
(NCCH3). ESI(+)MS in MeCN (m/z assignment, % intensity): 546
({[HC(3-Phpz)3]Cu(MeCN)}+, 100), 505 ({[HC(3-Phpz)3]Cu}+, 10).
376

A.G. Mahmoud et al.
InorganicaChimicaActa483(2018)371–378
Appendix A. Supplementary data
CuAAC reactions, Catal. Sci. Technol. 2 (2012) 195–200, https://doi.org/10.1039/
C1CY00297J.
[25] J. García-Álvarez, J. Díez, J. Gimeno, A highly efficient copper(i) catalyst for the
1,3-dipolar cycloaddition of azides with terminal and 1-iodoalkynes in water: re-
gioselective synthesis of 1,4-disubstituted and 1,4,5-trisubstituted 1,2,3-triazoles,
Green Chem. 12 (2010) 2127–2130, https://doi.org/10.1039/c0gc00342e.
[26] S. Lal, S. Díez-González, [CuBr(PPh 3) 3 ] for Azide−Alkyne Cycloaddition
Reactions under Strict Click Conditions, J. Org. Chem. 76 (2011) 2367–2373,
https://doi.org/10.1021/jo200085j.
Proton NMR spectra (selected region) of 1-6 and triazole products are
presented, as well as the crystal structure (low quality) of complex 1.
Supplementary data associated with this article can be found, in the
online version, at https://doi.org/10.1016/j.ica.2018.08.052.
[27] J. García-Álvarez, J. Díez, J. Gimeno, F.J. Suárez, C. Vincent, (Iminophosphorane)
copper(I) complexes as highly efficient catalysts for 1,3-dipolar cycloaddition of
azides with terminal and 1-iodoalkynes in water: One-pot multi-component reac-
tion from alkynes and in situ generated azides, Eur. J. Inorg. Chem. (2012)
5854–5863, https://doi.org/10.1002/ejic.201200789.
[28] A.G. Mahmoud, M.F.C. Guedes da Silva, J. Sokolnicki, P. Smoleński,
A.J.L. Pombeiro, Hydrosoluble Cu(i)-DAPTA complexes: synthesis, characteriza-
tion, luminescence thermochromism and catalytic activity for microwave-assisted
three-component azide–alkyne cycloaddition click reaction, Dalt. Trans. 47 (2018)
7290–7299, https://doi.org/10.1039/C8DT01232F.
References
[1] M.C. Linder, M. Hazegh-Azam, Copper biochemistry and molecular biology, Am. J.
Clin. Nutr. 63 (1996) 797S–811S, https://doi.org/10.1093/ajcn/63.5.797.
[2] I.P. Beletskaya, A.V. Cheprakov, Copper in cross-coupling reactions: The post-
Ullmann chemistry, Coord. Chem. Rev. 248 (2004) 2337–2364, https://doi.org/10.
1016/J.CCR.2004.09.014.
[3] S.E. Allen, R.R. Walvoord, R. Padilla-Salinas, M.C. Kozlowski, Aerobic copper-cat-
alyzed organic reactions, Chem. Rev. 113 (2013) 6234–6458, https://doi.org/10.
1021/cr300527g.
[29] N. Candelon, D. Lastécouères, A.K. Diallo, J. Ruiz Aranzaes, A highly active and
reusable copper(i)-tren catalyst for the “click” 1,3-dipolar cycloaddition of azides
and alkynes, Chem. Commun. 41 (2008) 741–743, https://doi.org/10.1039/
B716306A.
[4] J. Moegling, A. Hoffmann, S. Herres-Pawlis, Insights into copper-poly(pyrazolyl)
methane-catalyzed reactions for organic transformations, Synthesis (Stuttg). 49
(2017) 225–236, https://doi.org/10.1055/s-0036-1588892.
[5] C.W. Tornøe, C. Christensen, M. Meldal, Peptidotriazoles on Solid Phase: [1,2,3]-
Triazoles by Regiospecific Copper(I)-Catalyzed 1,3-Dipolar Cycloadditions of
Terminal Alkynes to Azides, J. Org. Chem. 67 (2002) 3057–3064, https://doi.org/
10.1021/JO011148J.
[30] S. Díez-González, S.P. Nolan, [(NHC) Cu]X Complexes as Efficient Catalysts for
2
Azide-Alkyne Click Chemistry at Low Catalyst Loadings, Angew. Chemie. 120
(2008) 9013–9016, https://doi.org/10.1002/ange.200803289.
[31] A. Makarem, R. Berg, F. Rominger, B.F. Straub, A Fluxional Copper Acetylide
Cluster in CuAAC Catalysis, Angew. Chemie Int. Ed. 54 (2015) 7431–7435, https://
doi.org/10.1002/anie.201502368.
[32] K.R. Reddy, K. Rajgopal, M.L. Kantam, Copper(II)-Promoted Regioselective
Synthesis of 1,4-Disubstituted 1,2,3-Triazoles in Water, Synlett. (2006) 957–959,
https://doi.org/10.1055/s-2006-933134.
[33] W.S. Brotherton, H.A. Michaels, J.T. Simmons, R.J. Clark, N.S. Dalal, L. Zhu,
Apparent Copper(II)-Accelerated Azide−Alkyne Cycloaddition, Org. Lett. 11
(2009) 4954–4957, https://doi.org/10.1021/ol9021113.
[34] P. Siemsen, R.C. Livingston, F. Diederich, Acetylenic coupling: a powerful tool in
molecular construction, Angew. Chemie Int. Ed. 39 (2000) 2632–2657, https://doi.
org/10.1002/1521-3773(20000804)39:15<2632::AID-ANIE2632>3.0.CO;2-F.
[35] K. Kamata, Y. Nakagawa, K. Yamaguchi, N. Mizuno, 1,3-Dipolar cycloaddition of
organic azides to alkynes by a dicopper-substituted silicotungstate, J. Am. Chem.
Soc. 130 (2008) 15304–15310, https://doi.org/10.1021/ja806249n.
[36] K. Yamaguchi, T. Oishi, T. Katayama, N. Mizuno, A supported copper hydroxide on
titanium oxide as an efficient reusable heterogeneous catalyst for 1,3-dipolar cy-
cloaddition of organic azides to terminal alkynes, Chem. – A Eur. J. 15 (2009)
10464–10472, https://doi.org/10.1002/chem.200901444.
[37] M. Vashist, K. Kushwaha, R. Kaushik, S.C. Jain, Synthesis of medicinally important
quinazolines decorated with 1,4-disubstituted-1,2,3-triazoles using CuSO 4 ·5H 2 O-
Et 3 N catalytic system, RSC Adv. 4 (2014) 23679–23684, https://doi.org/10.1039/
C4RA02123A.
[38] C. Zhou, J. Zhang, P. Liu, J. Xie, B. Dai, 2-Pyrrolecarbaldiminato–Cu(ii) complex
catalyzed three-component 1,3-dipolar cycloaddition for 1,4-disubstituted 1,2,3-
triazoles synthesis in water at room temperature, RSC Adv. 5 (2015) 6661–6665,
https://doi.org/10.1039/C4RA13423K.
[39] M. Bagherzadeh, A. Bayrami, R. Kia, M. Amini, L.J.K. Cook, P.R. Raithby, Two new
copper(II) complexes with chelating N, O-type bidentate ligands: Synthesis, char-
acterization, crystal structure and catalytic activity in azide–alkyne cycloaddition
reaction, Inorganica Chim. Acta. 466 (2017) 398–404, https://doi.org/10.1016/J.
ICA.2017.06.046.
[40] R.K. Reddy, K. Rajgopal, M.L. Kantam, Copper-alginates: a biopolymer supported
Cu(II) catalyst for 1,3-dipolar cycloaddition of alkynes with azides and oxidative
coupling of 2-naphthols and phenols in water, Catal. Letters. 114 (2007) 36–40,
https://doi.org/10.1007/s10562-007-9032-x.
[41] S. Trofimenko, Geminal poly(1-pyrazolyl)alkanes and their coordination chemistry,
J. Am. Chem. Soc. 92 (1970) 5118–5126, https://doi.org/10.1021/ja00720a021.
[42] D.L. Reger, T.C. Grattan, K.J. Brown, C.A. Little, J.J.S. Lamba, A.L. Rheingold,
R.D. Sommer, Syntheses of tris(pyrazolyl)methane ligands and {[tris(pyrazolyl)
methane]Mn(CO)3}SO3CF3 complexes: comparison of ligand donor properties, J.
Organomet. Chem. 607 (2000) 120–128, https://doi.org/10.1016/S0022-328X(00)
00290-4.
[43] D.L. Reger, T.C. Grattan, Synthesis of modified tris(pyrazolyl)methane ligands:
backbone functionalization, Synthesis (Stuttg). 2003 (2003) 350–356, https://doi.
org/10.1055/s-2003-37339.
[44] L.M.D.R.S. Martins, A.J.L. Pombeiro, Tris(pyrazol-1-yl)methane metal complexes
for catalytic mild oxidative functionalizations of alkanes, alkenes and ketones,
Coord. Chem. Rev. 265 (2014) 74–88, https://doi.org/10.1016/J.CCR.2014.01.
013.
[45] A.M. Kirillov, P. Smoleński, M. Haukka, M.F.C. Guedes da Silva, A.J.L. Pombeiro,
Unprecedented Metal-Free C(sp 3)−C(sp 3) Bond Cleavage: Switching from N
-Alkyl- to N -Methyl-1,3,5-triaza-7-phosphaadamantane, Organometallics 28 (2009)
1683–1687, https://doi.org/10.1021/om801026a.
[46] E. Haldón, E. Álvarez, M.C. Nicasio, P.J. Pérez, Copper(I) complexes with trispyr-
azolylmethane ligands: synthesis, characterization, and catalytic activity in cross-
coupling reactions, Inorg. Chem. 51 (2012) 8298–8306, https://doi.org/10.1021/
ic300843a.
[47] D.L. Reger, J.E. Collins, A.L. Rheingold, L.M. Liable-Sands, Synthesis and
Characterization of Cationic [Tris(pyrazolyl)methane]copper(I) Carbonyl and
[6] V.V. Rostovtsev, L.G. Green, V.V. Fokin, K.B. Sharpless, A Stepwise Huisgen
Cycloaddition Process: Copper(I)-Catalyzed Regioselective “Ligation” of Azides and
Terminal Alkynes, Angew. Chemie. 114 (2002) 2708–2711, https://doi.org/10.
1002/1521-3757(20020715)114:14<2708::AID-ANGE2708>3.0.CO;2-0.
[7] A set of fundamental requirements has to be fulfilled for a reaction procedure to be
applicable in this context: i) it must be wide in scope, ii) evince no sensitivity to-
wards oxygen or moisture, iii) proceed in absence of solvent or using a benign one,
iv) afford products in high yields and easily isolable, and v) be stereospecific.
[8] H.C. Kolb, K.B. Sharpless, The growing impact of click chemistry on drug discovery,
Drug Discov. Today. 8 (2003) 1128–1137, https://doi.org/10.1016/S1359-
6446(03)02933-7.
[9] J.E. Moses, A.D. Moorhouse, The growing applications of click chemistry, Chem.
Soc. Rev. 36 (2007) 1249–1262, https://doi.org/10.1039/B613014N.
[10] W.H. Binder, R. Sachsenhofer, ‘Click’ chemistry in polymer and materials science,
Macromol. Rapid Commun. 28 (2007) 15–54, https://doi.org/10.1002/marc.
200600625.
[11] E.F.V. Scriven, K. Turnbull, Azides: their preparation and synthetic uses, Chem. Rev.
88 (1988) 297–368, https://doi.org/10.1021/cr00084a001.
[12] S. Bräse, C. Gil, K. Knepper, V. Zimmermann, Organic azides: an exploding diversity
of a unique class of compounds, Angew. Chemie Int. Ed. 44 (2005) 5188–5240,
https://doi.org/10.1002/anie.200400657.
[13] A.K. Feldman, B. Colasson, V.V. Fokin, One-pot synthesis of 1,4-disubstituted 1,2,3-
triazoles from in situ generated azides, Org. Lett. 6 (2004) 3897–3899, https://doi.
org/10.1021/ol048859z.
[14] P. Appukkuttan, W. Dehaen, V.V. Fokin, E. Van der Eycken, A Microwave-Assisted
Click Chemistry Synthesis of 1,4-Disubstituted 1,2,3-Triazoles via a Copper(I)-
Catalyzed Three-Component Reaction, Org. Lett. 6 (2004) 4223–4225, https://doi.
org/10.1021/OL048341V.
[15] S. Özçubukçu, E. Ozkal, C. Jimeno, M.A. Pericàs, A Highly Active Catalyst for
Huisgen 1,3-Dipolar Cycloadditions Based on the Tris(triazolyl)methanol−Cu(I)
Structure, Org. Lett. 11 (2009) 4680–4683, https://doi.org/10.1021/ol9018776.
[16] F. Li, T.S.A. Hor, Facile Synthesis of Nitrogen Tetradentate Ligands and Their
Applications in Cu I -Catalyzed N-Arylation and Azide-Alkyne Cycloaddition, Chem.
– A Eur. J. 15 (2009) 10585–10592, https://doi.org/10.1002/chem.200901014.
[17] F. Himo, T. Lovell, R. Hilgraf, V.V. Rostovtsev, L. Noodleman, K.B. Sharpless,
V.V. Fokin, Copper(I)-catalyzed synthesis of azoles. DFT study predicts un-
precedented reactivity and intermediates, J. Am. Chem. Soc. 127 (2005) 210–216,
https://doi.org/10.1021/ja0471525.
[18] X. Zhang, H. Li, L. You, Y. Tang, R.P. Hsung, Copper salt-catalyzed azide-[3 + 2]
cycloadditions of ynamides and bis-ynamides, Adv. Synth. Catal. 348 (2006)
2437–2442, https://doi.org/10.1002/adsc.200600404.
[19] J.E. Hein, J.C. Tripp, L.B. Krasnova, K.B. Sharpless, V.V. Fokin, Copper(I)-Catalyzed
Cycloaddition of Organic Azides and 1-Iodoalkynes, Angew. Chemie Int. Ed. 48
(2009) 8018–8021, https://doi.org/10.1002/anie.200903558.
[20] V. Hong, A.K. Udit, R.A. Evans, M.G. Finn, Electrochemically protected copper(I)-
catalyzed azide-alkyne cycloaddition, ChemBioChem. 9 (2008) 1481–1486,
https://doi.org/10.1002/cbic.200700768.
[21] C. Girard, E. Önen, M. Aufort, S. Beauvière, E. Samson, J. Herscovici, Reusable
polymer-supported catalyst for the [3+2] Huisgen cycloaddition in automation
protocols, Org. Lett. 8 (2006) 1689–1692, https://doi.org/10.1021/ol060283l.
[22] M. Chtchigrovsky, A. Primo, P. Gonzalez, K. Molvinger, M. Robitzer, F. Quignard,
F. Taran, Functionalized chitosan as a green, recyclable, biopolymer-supported
catalyst for the [3+2] huisgen cycloaddition, Angew. Chemie – Int. Ed. 48 (2009)
5916–5920, https://doi.org/10.1002/anie.200901309.
[23] G. Molteni, C.L. Bianchi, G. Marinoni, N. Santo, A. Ponti, Cu/Cu-oxide nanoparticles
as catalyst in the “click” azide–alkyne cycloaddition, New J. Chem. 30 (2006)
1137–1139, https://doi.org/10.1039/B604297J.
[24] E. Ozkal, S. Özçubukçu, C. Jimeno, M.A. Pericàs, Covalently immobilized tris
(triazolyl)methanol–Cu(i) complexes: highly active and recyclable catalysts for
377

A.G. Mahmoud et al.
InorganicaChimicaActa483(2018)371–378
Acetonitrile Complexes, Organometallics. 15 (1996) 2029–2032, https://doi.org/
IC0112645.
10.1021/OM960026S.
[52] N. Kirai, Y. Yamamoto, Homocoupling of arylboronic acids catalyzed by 1,10-
phenanthroline-ligated copper complexes in air, European J. Org. Chem. 2009
(2009) 1864–1867, https://doi.org/10.1002/ejoc.200900173.
[53] M.S. Raghavendra, Y. Lam, Regiospecific solid-phase synthesis of substituted 1,2,3-
triazoles, Tetrahedron Lett. 45 (2004) 6129–6132, https://doi.org/10.1016/j.tetlet.
2004.06.055.
[54] M.S.R. Murty, M.R. Katiki, D. Kommula, Multicomponent Click Synthesis of β-
Hydroxy/Benzyl 1,2,3- Triazoles Catalyzed by Magnetically Recyclable Nano Iron
Oxide in Water, Can. Chem. Trans. Year. 4 (2016) 47–61, https://doi.org/10.
13179/canchemtrans.2016.04.01.0270.
[48] R. Wanke, P. Smolenski, M.F.C. Guedes da Silva, L.M.D.R.S. Martins,
A.J.L. Pombeiro, Cu(I) Complexes Bearing the New Sterically Demanding and
Coordination Flexible Tris(3-phenyl-1-pyrazolyl)methanesulfonate Ligand and the
Water-Soluble Phosphine 1,3,5-Triaza-7-phosphaadamantane or Related Ligands,
Inorg. Chem. 47 (2008) 10158–10168, https://doi.org/10.1021/ic801254b.
[49] M. Cvetkovic, S.R. Batten, B. Moubaraki, K.S. Murray, L. Spiccia, Copper(I) tris
(pyrazolyl)methane complexes and their reactivity towards dioxygen, Inorganica
Chim. Acta. 324 (2001) 131–140, https://doi.org/10.1016/S0020-1693(01)
00565-5.
[50] I. Cano, M.C. Nicasio, P.J. Pérez, Copper(i) complexes as catalysts for the synthesis
of N-sulfonyl-1,2,3-triazoles from N-sulfonylazides and alkynes, Org. Biomol. Chem.
8 (2010) 536–538, https://doi.org/10.1039/B912835B.
[51] D.L. Reger, C.A. Little, M.D. Smith, G.J. Long, Solid-State Structural and Magnetic
Investigations of {M[HC(3,5-Me2pz)3]2}(BF4)2 (M = Fe Co, Ni, Cu): Observation
of a Thermally Induced Solid-State Phase Change Controlling an Iron(II) Spin-State
Crossover, Inorg. Chem. 41 (2002) 4453–4460, https://doi.org/10.1021/
[55] K. Kacprzak, Efficient one-pot synthesis of 1,2,3-triazoles from benzyl and alkyl
halides, Synlett. 2005 (2005) 0943–0946, https://doi.org/10.1055/s-2005-864809.
[56] J. Liu, M. Liu, Y. Yue, M. Yao, K. Zhuo, Environmental Friendly Azide-Alkyne
Cycloaddition Reaction of Azides, Alkynes, and Organic Halides or Epoxides in
Water: Efficient “Click”; Synthesis of 1,2,3-Triazole Derivatives by Cu Catalyst,
Chinese J. Chem. 30 (2012) 644–650, https://doi.org/10.1002/cjoc.201280012.
378