Hybrid NS ligands supported Cu(i)/(ii) complexes for azide-alkyne cycloaddition reactions

Article abstract of DOI:10.1039/c3dt50247c

Three copper complexes of nitrogen-sulfur donor ligands, [CuBr ₂(L1)] (1), [CuCl₂(L2)₂] (2) and [Cu ₂I₂(L3)]_n (3) (L1 = bis(2- cyclohexylsulfanylethyl)amine, L2 = 2-(benzylsulfanylmethyl)pyridine and L3 = 2-(4-pyridylsulfanylmethyl)pyridine), have been synthesized and characterized by single-crystal X-ray diffraction (XRD), powder XRD and TGA analysis. Complexes 1 and 2 are mononuclear Cu(ii) complexes and are EPR active with distorted square-pyramidal and octahedral geometry, respectively. Complex 3 is a two-dimensional tetrahedral Cu(i) coordination polymer with 16- and 20-membered metallocycles. These complexes show good catalytic activities for one-pot azide-alkyne cycloaddition reactions in CH₃OH-H₂O.

Full text of DOI:10.1039/c3dt50247c

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Hybrid NS ligands supported Cu(I)/(II) complexes for
azide–alkyne cycloaddition reactions†
Cite this: Dalton Trans., 2013, 42, 11319
Shi-Qiang Bai,*a Lu Jiang,b Jing-Lin Zuoc and T. S. Andy Hor*a,b
Three copper complexes of nitrogen–sulfur donor ligands, [CuBr2(L1)] (1), [CuCl2(L2)2] (2) and
[Cu2I2(L3)]n (3) (L1 = bis(2-cyclohexylsulfanylethyl)amine, L2 = 2-(benzylsulfanylmethyl)pyridine and L3 =
2-(4-pyridylsulfanylmethyl)pyridine), have been synthesized and characterized by single-crystal X-ray dif-
fraction (XRD), powder XRD and TGA analysis. Complexes 1 and 2 are mononuclear Cu(II) complexes and
are EPR active with distorted square-pyramidal and octahedral geometry, respectively. Complex 3 is a
two-dimensional tetrahedral Cu(I) coordination polymer with 16- and 20-membered metallocycles.
These complexes show good catalytic activities for one-pot azide–alkyne cycloaddition reactions in
CH3OH–H2O.
Received 24th January 2013,
Accepted 4th June 2013
DOI: 10.1039/c3dt50247c
www.rsc.org/dalton
(chiral and photoluminescent) coordination polymers.10 We
herein report three NS donor-based copper complexes (1–3)
Introduction
The copper-catalyzed azide–alkyne cycloaddition (CuAAC) reac- and their catalytic activities in the AAC reaction.
tion has become one of the most attractive click reactions due
to its green catalytic features and very mild reaction con-
ditions.1 The reaction tolerates a wide range of functional
groups and affords high yields of regiospecific 1,4-disubsti-
Experimental section
Materials and physical measurements
tuted-1,2,3-triazoles. It has emerged as a powerful tool for the
construction of functional 1,2,3-triazole molecules, polymers
and hybrid materials.2 Various types of copper catalysts have
been explored for this reaction, such as simple Cu(II) salts with
a reducing agent, organometallic Cu(I) precatalysts, and nano-
structured copper catalysts.1–3 For the well-defined catalyst
system, phosphine-,4 N-heterocyclic carbene-,5 imidazole-,6 sul-
fated-,7 nitrogen-based molecules8 are among the most used
ligands. Meanwhile, hybrid nitrogen–sulfur (NS) ligands are
promising in catalytic reactions because of the mix of hard
and soft donors and hemilabile functions.9 Typical examples
are NS ligands in Cu(II) mediated oxidation of di-tert-butyl cate-
chol,9k SNS ligands in Cr(III) catalyzed selective ethylene tri-
merizations,9f,g Pd(II) catalyzed Suzuki–Miyaura coupling
reactions,9j and the early investigations of CuAAC reactions.9l
A series of hybridized 1,2,3-triazoles have also been explored
in CuAAC reactions and used as building blocks for functional
Sodium azide is potentially explosive. Only micro-scaled reac-
tions may be performed, and all operations must be handled
with necessary precautionary measures. All the starting chemi-
cals were used as received. The ligands L1–L3 were prepared
based on literature procedures.11 Elemental analyses were per-
formed on a Vario MICRO Elementar system. Infrared spectra
were obtained on a Varian 3100 FT-IR spectrometer from
samples in a KBr disc. Electrospray ionization mass spectra
(ESI-MS) were recorded in positive ion mode using a thermo
Finnigan LCQ mass spectrometer and a Shimadzu LCMS-IT-
TOF mass spectrometer. NMR spectra were measured at r.t.
using a Bruker 400 MHz NMR spectrometer. Powder X-ray
diffraction data were collected on a SIEMENS D5005 X-ray dif-
fractometer with Cu-Kα radiation (λ = 1.5406 Å). EPR spectra
were measured using a Bruker ER 200-D-SRC spectrometer for
solid samples at r.t. Thermogravimetric analyses (TGA) were
carried out in air (for 1 and 3) or N2 (for 2) stream using TA
Instruments SDT 2960 simultaneous DTA-TGA equipment with
a heating rate of 10 °C min−1. Catalytic reactions were per-
formed on a MultiMax reactor system.
aInstitute of Materials Research and Engineering, A*STAR (Agency for Science,
Technology and Research), 3 Research Link, Singapore 117602, Singapore.
E-mail: bais@imre.a-star.edu.sg; Tel: +(65) 65141515
bDepartment of Chemistry, National University of Singapore, 3 Science Drive 3,
Singapore 117543, Singapore. E-mail: andyhor@nus.edu.sg; Fax: (+)65-6873-1324
cState Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical
Synthesis of [CuBr2(L1)] (1). A CH3OH solution (5 mL) of
CuBr2 (0.1 mmol, 22 mg) was added to a CH3OH solution
(5 mL) of ligand L1 (0.1 mmol, 30 mg). The mixture was stirred
for 5 min at r.t. Slow evaporation of the resulting solution
afforded green crystals of 1 within a day. Yield: 0.045 g (85%).
Engineering, Nanjing University, Nanjing 210093, China
†CCDC 809868–809870 and 918965. For crystallographic data in CIF or other
electronic format see DOI: 10.1039/c3dt50247c
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Anal. Calcd for C16H31Br2CuNS2 (524.90): C, 36.61; H, 5.95; N, For 1-(4-tert-butylbenzyl)-4-hexyl-1H-1,2,3-triazole. 1H-NMR
2.67%. Found: C, 36.75; H, 5.89; N, 2.68%. IR bands (cm−1): (CDCl3, 400.1 MHz, δ): 7.39 and 7.37 (d, 2H, J = 8 Hz), 7.19 (s,
3449(m) (νN–H), 3049(m), 2929(s), 2853(m), 2361(m), 1634(m), 1H, triazole), 7.18 (s, 2H), 5.45 (s, 2H, phenyl-CH2), 2.69, 2.67
1447(s), 1342(m), 1262(m), 1209(m), 1086(m), 997(m), 887(m), and 2.65 (t, 2H, triazole-CH2–CH2, J = 8 Hz), 1.66–1.59 (m, 2H,
809(m) and 725(m). ESI-MS (m/z, %): [L1 + H]+ (302, 100); triazole-CH2–CH2), 1.30–1.25 (m, 15H, CH2CH2CH2CH3 and
[Cu(L1)]+ (364, 60) and [CuBr(L1)]+ (443, 10).
C(CH3)3), 0.87, 0.86 and 0.84 (t, 3H, CH2CH3, J = 6 Hz). 13C-NMR
Synthesis of [CuCl2(L2)2] (2). Complex 2 was prepared simi- (CDCl3, 100.6 MHz, δ): 151.9, 149.0, 132.2, 127.9, 126.1 and
larly to 1 using ligand L2 (0.2 mmol, 43 mg) and CuCl2·2H2O 120.6 for the C of phenyl and triazole groups; 53.8 (phenyl–
(0.1 mmol, 17 mg) as substrates. Yield: 0.045 g (80%). Anal. CH2–triazole), 34.8, 31.7, 31.4, 29.5, 29.1, 25.9, 22.7 and 14.1
Calcd for C26H26Cl2CuN2S2 (565.05): C, 55.26; H, 4.64; N, for the C of hexyl and tert-butyl groups. ESI-MS (m/z): 300.2.
4.96%. Found: C, 55.10; H, 4.48; N, 4.87%. IR bands (cm−1):
X-ray crystallography
3059m, 3027m, 2914m, 1601s, 1570m, 1484s, 1433s, 1394m,
1316m, 1267m, 1153m, 1068m, 1027m, 759s, 720s, 699s,
568m, 471m and 439m. ESI-MS (m/z, %): [L2 + H]+ (216, 35);
[Cu(L2)2]+ (493, 100) and [CuCl(L2)2]+ (528, 30).
All measurements were conducted on a Bruker AXS SMART
APEX diffractometer equipped with a CCD area-detector using
Mo-Kα radiation (λ = 0.71073 Å) (Table 1). The collecting
frames of data, indexing reflection and determination of
lattice parameters and polarization effects were performed
with the SMART suite programs.12 The integration of intensity
of reflections and scaling was carried out by SAINT.12 The
empirical absorption correction was performed by SADABS.13
The space group determination, structure solution and least-
squares refinements on |F|2 were carried out with the
SHELXS-97 and SHELXL-97.14 The structures were solved by
direct methods to locate the heavy atoms, followed by differ-
ence maps for the light non-hydrogen atoms. Anisotropic
thermal parameters were refined for the rest of the non-hydro-
gen atoms. Hydrogen atoms were placed geometrically and
refined isotropically. CCDC reference numbers: 809868 (1),
809869 (2), 809870 (3) and 918965 (4).
Synthesis of [Cu2I2(L3)]n (3). A CH3CN solution of CuI
(0.2 mmol, 38 mg) was added to a test tube. A mixture of
CH3CN–Et2O (1 : 1, 6 mL) was carefully layered on top, followed
by addition of a layer of an Et2O solution (5 mL) of ligand L3
(0.1 mmol, 20 mg). Slow diffusion resulted in yellow plate crys-
tals of 3 after about two weeks. Yield: 44 mg (75%). Anal. Calcd
for C11H10Cu2I2N2S (583.15): C, 22.65; H, 1.73; N, 4.80%.
Found: C, 22.20; H, 1.75; N, 4.78%. IR bands (cm−1): 1581m,
1472m, 1411m, 1214m, 1055m, 1010m, 893m, 808m, 767m,
716m and 496m. ESI-MS (m/z, %): [L3 + H)]+ (203, 100) and
[Cu(L3)2]+ (467, 40).
Synthesis of [Cu2I2(L4)2]n·n(CH3CN) (4). Complex 4 was pre-
pared similarly to 3 using catalytic product 1-(4-picolyl)-4-
phenyl-1H-1,2,3-triazole (L4, in Entry 6 of Table 3) (0.1 mmol,
24 mg) and CuI (0.1 mmol, 19 mg) as substrates. Yield: 25 mg
(55%). Anal. Calc. for dried sample C28H24Cu2I2N8 (853.44): C,
39.40; H, 2.83; N, 13.13%. Found: C, 39.49; H, 2.89; N, 13.24%.
IR bands (cm−1): 3089m, 2932m, 1612m, 1466m, 1421s,
Results and discussion
1365m, 1224m, 1071m, 1054m, 973m, 826m, 798m, 765s, The ligands L1–L3 with hard–soft donors can be easily syn-
694m, 588m and 483m. ESI-MS (m/z, %): [Cu(L4)2]+ (535, 100).
thesized with high yields. The coordination reactions with the
NMR spectra and ESI-MS data for selective catalytic corresponding copper precursors under mild conditions
products. For 1-(2,6-difluorobenzyl)-4-hexyl-1H-1,2,3-triazole. produce stable complexes with coordination modes shown in
1H-NMR (CDCl3, 400.1 MHz, δ): 7.36–7.32 (m, 1H), 7.28 (s, 1H, Scheme 1.
triazole), 6.97, 6.95 and 6.93 (t, 2H, J = 8 Hz), 5.57 (s, 2H,
The IR spectrum of 1 shows a prominent band in the
phenyl-CH2). 2.68, 2.66 and 2.64 (t, 2H, triazole-CH2–CH2, J = ∼3449 cm−1 region attributed to the N–H group of ligand L1.
8 Hz), 1.65–1.58 (m, 2H, triazole-CH2–CH2), 1.32–1.25 (m, 6H, Complexes 1–3 were structurally characterised by single-crystal
CH2CH2CH2CH3), 0.87, 0.85 and 0.84 (t, 3H, CH3, J = 6 Hz). X-ray crystallography (see below). Their X-ray powder diffrac-
13C-NMR (CDCl3, 100.6 MHz, δ): 162.9, 160.3, 149.0, 131.3, tion patterns show some disagreement with their simulated
120.6, 112.0 and 111.8 for the C of phenyl and triazole groups; patterns, especially in 1 (Fig. 1), suggesting that phase purity
41.3 (phenyl–CH2–triazole), 31.7, 29.5, 29.0, 25.8, 22.6 and ranges from good in 3 to fair in 1. The thermogravimetric (TG)
14.1 for the C of hexyl group. ESI-MS (m/z): 280.1. For 1-(4-iso- curves over 25–800 °C are given in Fig. 2. Complexes 1–3 are
propylbenzyl)-4-hexyl-1H-1,2,3-triazole.
1H-NMR
(CDCl3, stable to ∼150, 160 and 190 °C, followed by steady decline
400.1 MHz, δ): 7.22–7.16 (m, 5H, phenyl and triazole), 5.44 (s, until reaching a residual weight at ∼580, 690 and 620 °C,
2H, phenyl-CH2), 2.95–2.84 (m, 1H, CH(CH3)2), 2.68, 2.67 and respectively. Solid X-band EPR spectra were recorded for Cu(II)
2.65 (t, 2H, triazole-CH2–CH2, J = 6 Hz), 1.66–1.58 (m, 2H, tria- complexes 1 and 2 at 298 K (Fig. 3). Complex 1 shows an axial
zole-CH2–CH2), 1.28–1.22 (m, 12H, CH2CH2CH2CH3 and CH symmetry EPR pattern with g1 = 2.12 and g2 = 2.05. Complex 2
(CH3)2), 0.87, 0.85 and 0.84 (t, 3H, CH2CH3, J = 6 Hz). 13C-NMR reveals three g-value anisotropic EPR spectra with g1 = 2.26, g2
(CDCl3, 100.6 MHz, δ): 149.5, 149.0, 132.5, 128.1, 127.2 and = 2.08 and g3 = 2.04, which is consistent with the tetragonally
120.5 for the C of phenyl and triazole groups; 53.9 (phenyl– distorted Cu(II).15 A one-dimension coordination polymer 4
CH2–triazole), 33.9, 31.6, 29.5, 29.0, 25.9, 24.0, 22.6 and 14.1 (ave dCu–Cu = 2.78 Å) has also been obtained from L4 with CuI.
for the C of hexyl and isopropyl groups. ESI-MS (m/z): 286.2. It exhibits a solid state emission band centered at 475 nm
11320 | Dalton Trans., 2013, 42, 11319–11326
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Table 1 Summary of crystallographic data for 1–4
Complex
1
2
3
4
Formula
MW
C
16H31Br2CuNS2
C26H26Cl2CuN2S2
565.05
C11H10Cu2I2N2S
583.15
C30H27Cu2I2N9
894.49
524.90
T/K
100(2)
293(2)
223(2)
293(2)
Crystal size/mm3
0.80 × 0.20 × 0.14
Monoclinic
P21/c
0.54 × 0.30 × 0.18
Triclinic
ˉ
P1
0.40 × 0.04 × 0.03
Triclinic
ˉ
P1
0.48 × 0.20 × 0.10
Triclinic
ˉ
P1
Crystal system
Space group
a/Å
b/Å
c/Å
α/°
12.1800(7)
6.6097(4)
25.400(1)
8.6863(4)
12.0925(6)
13.6748(6)
69.563(1)
86.265(1)
70.457(1)
1266.3(1)
2
7.7667(4)
8.2376(4)
12.2411(6)
92.526(1)
93.782(1)
109.716(1)
733.82(6)
2
10.1742(4)
11.7158(5)
13.8012(5)
95.619(1)
90.223(1)
94.108(1)
1632.9(1)
2
β/°
100.959(1)
γ/°
V/Å3
2007.6(2)
4
1.737
Z
Dcalc/g cm−3
1.482
1.256
2.639
7.229
1.819
3.228
μ/mm−1
5.273
θ range/°
1.63–27.50
13 643
4595 [0.0299]
203
1.91–27.50
16 552
5816 [0.0266]
301
1.67–27.50
9485
3358 [0.0300]
163
1.48–27.50
21 424
7492 [0.0354]
383
Reflections collected
Independent reflections [Rint
Parameters
GOF
]
1.031
1.041
1.054
1.029
R1(I > 2σ(I))
wR2(all data)
0.0313
0.0781
0.0322
0.0845
0.0219
0.0550
0.0322
0.0819
Scheme 1 Coordination modes of ligands L1–L3 in 1–3, respectively.
Fig. 2 TGA curves of 1–3.
Fig. 1 Powder XRD patterns of 1–3 (T = theoretical profile referenced to the
experimentally determined structure by single-crystal XRD; E = experimental
data).
(excitation at 337 nm) at r.t. (Fig. 4). The emission could be
attributed to metal-to-ligand charge-transfer (MLCT) and/or
ligand-to-ligand charge transfer (XLCT) excited states.16
Similar Cu(I) 4-py functionalized 1,2,3-triazole complexes have
been described.
Fig. 3 EPR spectra of the solid samples of complexes 1 and 2 with frequency
at 9.7771 and 9.7751 GHz, respectively.
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Single-crystal structures
21.2–29.0°, centroid–centroid distance19 3.87 Å) between two
pyridyl rings of neighboring Cu1 and Cu2 units result in
supramolecular structure.
Complex 1 is a mononuclear five-coordinated Cu(II) complex
with a distorted square-pyramidal geometry (Fig. 5). The SNS
donors of ligand L1 and one terminal Br ligand form the basal
plane, leaving the remaining terminal Br ligand perched at the
apical position. The average chelating angle formed by the
pincer ligand L1 is 85.4° and the structural index τ17 is 0.13,
which are comparable with those (84.8° and 0.12) of ligand bis-
(2-(benzylsulfanyl)ethyl)amine in a CuBr2 complex.9l Similar
coordination modes are also found in Cr(III) and Pd(II) com-
plexes.9f,g,j The crystal framework is stabilised by intermolecu-
lar H-bonding interactions between the skeletal secondary
amine N–H of L1 and the apical bromide of neighboring units
(N⋯Br 3.26, N–H 0.82, Br⋯H 2.46 Å and ∠NHBr 167°).
Complex 3 is a two-dimensional coordination polymer with
two Cu(I) centers (Cu1 and Cu2) in their independent units
(Fig. 7). Both are tetrahedral surrounded by two μ2-I ligands,
one N and one S donor. Ligand L3 is chelating (N2py and S) at
Cu1. L3 also coordinates to Cu2 through its N donor N4py. Cu2
is further stabilised by a S donor from neighboring L3. The S
donor shows unique dual chelating and bridging modes
between neighboring copper centers. The structure is further
stabilised by intramolecular π⋯π interactions (displace-
ment angle19 12.4–16.3°, centroid–centroid distance19 3.70 Å)
between the 4- and 2-pyridyl rings of neighboring L3 ligands.
Complex 2 is a mononuclear octahedral Cu(II) complex
(Fig. 6). There are two dependent centric symmetric Cu(II)
coordination units (Cu1 and Cu2) in one unit cell. Two L2
ligands are chelating on [CuCl2] with the S atoms trans
oriented at the axis positions with different Cu–S lengths (2.79
and 2.97 Å). The chelate angles (79.0 and 75.7°) of ligands L2
are comparable with that of the N2S2 ligand (78.5°) on a CuCl2
1-D coordination polymer.18 They are smaller than those of
the pincer SNS ligand on the CuCl2 complex (ave 85.3°).9l Inter-
molecular π⋯π stacking interactions (displacement angle19
Fig. 6 Molecular structure of 2 with intermolecular π⋯π stacking interactions.
(Cu1⋯Cu2 8.34 Å).
Fig. 4 Solid state excitation (left) and photoluminescent (right) spectra of 4.
Fig. 5 Molecular structure of 1 with intermolecular H-bonding interactions.
(Cu⋯Cu 6.61 Å).
Fig. 7 (a) Molecular structure of 3. (b) 2-D polymeric structure of 3 with
16- and 20-membered metallocycles.
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Scheme 2 Coordination modes of 4-py functionalized 1,2,3-triazoles in Cu(I)
complexes. (R1 = n-hexyl, n-pentyl or n-butyl; R2 = 2-pyridylsulfanylmethyl; R3
=
phenyl).
Neighboring copper units are further bridged by two μ2-I
ligands to give symmetric [Cu2I2] units, which extend to a 2-D
polymeric layer in the ac plane with two types of (16- and
20-membered) metallocycles.
4-Pyridyl(Py) functionalized 1,2,3-triazoles exhibit a few
coordination modes in Cu(I) complexes with different R
pendant substituents. (Scheme 2) When the R group is a flex-
ible alkyl, the ligands adopt coordination mode I to support 3-
D Cu(I) polymeric structures.10a,c When the R group is 2-pyri-
dylsulfanylmethyl, it coordinates with mode II and forms a
1-D coordination polymer with 18-metallocycle.8n In the coordi-
nation reaction of CuI with 1-(4-picolyl)-4-phenyl-1H-1,2,3-tria-
zole (L4) (entry 6 of Table 3), the ligand adopts mode III to
form a 1-D structure (4) with 16-membered metallocycle.
(Fig. 8) All Cu(I) are tetrahedral and the complexes are lumi-
nescent active.10a,c,8n The coordination modes and structures
are dependent on the substituent.
Weak secondary interactions (e.g. intramolecular π⋯π inter-
actions (ave displacement angle19 21.9°, ave centroid–centroid
distance19 3.45 Å) between two pyridyl rings in 4) also appear
to have influence on the coordination alignment.
Fig. 8 (a) Symmetric units of 4 with intramolecular π⋯π stacking interactions.
(b) 1-D structure of 4.
Table 2 Catalyst optimization
Catalytic investigation
The one-pot azide–alkyne cycloaddition reactions were
screened with complexes 1–3. The reactions were conducted
on a MultiMax reactor that is equipped with parallel reaction
tubes at 35 °C. The catalytic conditions were optimized by
benzyl chloride, sodium azide and phenylacetylene in CH3CN–
H2O, CH3OH–H2O mixtures or H2O at different catalyst load-
ings (1 or 2 mol%) (Table 2). Under optimized conditions
(CH3OH–H2O, 1 : 1, 2 mL; 15 h; 35 °C), the reaction scope was
studied under different substrates (Table 3). The reaction
between phenylacetylene and 1-octyne was chosen as a model
for examination under different alkyl azides (generated in situ
from alkyl bromides with NaN3). The formations of 1-benzyl-4-
phenyl-1H-1,2,3-triazole and 1-(4-tert-butylbenzyl)-4-phenyl-1H-
1,2,3-triazole under catalytic 1–3 are shown in Fig. 9. 4-tert-
Butylbenzyl bromide is slightly more active than benzyl chlor-
ide under similar conditions.
Entry
Solvent
Catalyst
GC-MS conversion (%)
1
2
3
4
5
6
7
8
CH3CN–H2O = 1 : 1
H2O
1
1
1
30
15
62
72
99 (81)
38
12
45
64
99
10
41
46
53
96
CH3OH–H2O = 1 : 1
1a
1a,b
2
CH3CN–H2O = 1 : 1
H2O
2
2
9
CH3OH–H2O = 1 : 1
2a
2a,b
3
10
11
12
13
14
15
CH3CN–H2O = 1 : 1
H2O
3
3
CH3OH–H2O = 1 : 1
3a
3a,b
Apart from the 4-picoly bromide substrate (with 40–70%
isolated yields), all other bromides (Table 3) show moderate to
quantitative conversions towards the product of 1,4-disubsti-
tuted-1,2,3-triazoles. Trace amounts of homocoupling products
a Loading: 2 mol%. b 15 h. Isolated yield in parentheses.
of dialkynes were detected by GC-MS. The 1,4-disubstituted- single-crystal XRD analysis (Fig. 10).5,8,20 Minor side products
1,2,3-triazoles were confirmed by NMR spectral analysis. The of 1,4,5-trisubstituted-1,2,3-triazoles were detected by GC-MS
catalytic products 1-(4-tert-butylbenzyl)-4-phenyl-1H-1,2,3-tria- when fluoro-, alkyl–benzyl and 2-picolyl bromides were used
zole and 1-(4-cyanobenzyl)-4-phenyl-1H-1,2,3-triazole (entries 4 as substrates (entries 1–4, 8–11, 12 (for 2), Table 3). There
and 7 of Table 3) were isolated and their structures verified by are two reported synthetic methods for 1,4,5-trisubstituted
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Table 3 Reaction scope at 2 mol% catalyst loading
Fig. 10 Single-crystal structures of 1-(4-tert-butylbenzyl)-4-phenyl-1H-1,2,3-
triazole and 1-(4-cyanobenzyl)-4-phenyl-1H-1,2,3-triazole.
GC-MS conversion (%)
Entry
1
Alkyne
Bromide
1
2
3
1,2,3-triazoles, from tandem reaction and alkynylation with
1,4-products.1–8
98
91
89 (58)
These copper complexes with hybrid NS ligands are new
well-defined active catalysts for azide–alkyne cycloaddition
reactions. These complexes are air stable and can be easily syn-
thesized. The catalytic activities are comparable to other nitro-
gen-based ligand coordinated Cu(I) catalysts,8 but less
favourable than many Cu(I) phosphine and NHC carbene cata-
lysts.4,5 There are also shortcomings in the selective pro-
duction of 1,4-disubstituted-1,2,3-triazoles, especially for
substrates with fluoro- and alkyl-substituents.
2
93
91 (76)
89
3
4
99
99
96 (71)
98
97
96 (78)
5a
6a
99
99 (79)
(50)
99 (93)
(70)
(40)
7
8
99
95
99
91
99
89
Conclusions
The hybrid nitrogen–sulfur ligands show diverse coordination
motifs supporting different copper assemblies that are active
in one-pot cycloaddition reactions of alkynes, alkyl bromides
and sodium azide. Successful use of click product 1-(4-picolyl)-
4-phenyl-1H-1,2,3-triazole as a ligand to prepare a Cu(I) coordi-
nation polymer points to a pathway for new polymeric
materials and new generations of click catalysts. These results
have promoted us to investigate other uses for these hybri-
dized triazole-based molecular materials.
9
98
82 (74)
82
10
11
93
93
83 (70)
91
80
83
12a
13a
96
94 (68)
(61)
99 (89)
(57)
(50)
Acknowledgements
14
99 (92)
99
99
We are grateful to Dr L. L. Koh, G. K. Tan and Y. M. Hong for
X-ray diffractometry measurement assistance. This work was
supported by National University of Singapore, Ministry of
Education of Singapore and the Institute of Materials Research
and Engineering, A*STAR Singapore.
a Na2CO3 (1 mmol) was used. Isolated yields in parentheses.
Notes and references
1 (a) R. Huisgen, G. Szeimies and L. Möbius, Chem. Ber.,
1967, 100, 2494–2507; (b) V. V. Rostovtsev, L. G. Green,
V. V. Fokin and K. B. Sharpless, Angew. Chem., Int. Ed.,
2002, 41, 2596–2599; (c) C. W. Tornøe, C. Christensen and
M. Meldal, J. Org. Chem., 2002, 67, 3057–3064;
(d) M. Meldal and C. W. Tornøe, Chem. Rev., 2008, 108,
2952–3015; (e) J. E. Hein and V. V. Fokin, Chem. Soc. Rev.,
2010, 39, 1302–1315.
2 (a) J. E. Moses and A. D. Moorhouse, Chem. Soc. Rev., 2007,
36, 1249–1262; (b) W. H. Binder and R. Sachsenhofer,
Macromol. Rapid Commun., 2007, 28, 15–54; (c) T. Devic,
O. David, M. Valls, J. Marrot, F. Couty and G. Férey, J. Am.
Chem. Soc., 2007, 129, 12614–12615; (d) J. A. Johnson,
Fig. 9 Formation of (1-benzyl-4-phenyl-1H-1,2,3-triazole and 1-(4-tert-butyl-
benzyl)-4-phenyl-1H-1,2,3-triazole) (determined by GC-MS) over 15 h.
11324 | Dalton Trans., 2013, 42, 11319–11326
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
M. G. Finn, J. T. Koberstein and N. J. Turro, Macromol.
Rapid Commun., 2008, 29, 1052–1072; (e) P. M. E. Gramlich,
C. T. Wirges, A. Manetto and T. Carell, Angew. Chem., Int.
Ed., 2008, 47, 8350–8358; (f) Y. Goto, H. Sato, S. Shinkai
and K. Sada, J. Am. Chem. Soc., 2008, 130, 14354–14355;
(g) C. L. Droumaguet, C. Wang and Q. Wang, Chem. Soc.
Rev., 2010, 39, 1233–1239; (h) G. Aromí, L. A. Barrios,
O. Roubeau and P. Gamez, Coord. Chem. Rev., 2011, 255,
485–546; (i) L. Liang and D. Astruc, Coord. Chem. Rev.,
2011, 255, 2933–2945; ( j) S.-Q. Bai, D. J. Young and
T. S. A. Hor, Chem.–Asian J., 2011, 6, 292–304; (k) L. Zhao,
T. Chano, S. Morikawa, Y. Saito, A. Shiino, S. Shimizu,
T. Maeda, T. Irie, S. Aonuma, H. Okabe, T. Kimura,
T. Inubushi and N. Komatsu, Adv. Funct. Mater., 2012,
22, 5107–5117; (l) C. B. Anderson, A. B. S. Elliott,
C. J. McAdam, K. C. Gordon and J. D. Crowley, Organo-
metallics, 2013, 32, 788–797.
3 (a) F. Alonso, Y. Moglie, G. Radivoy and M. Yus, Eur. J. Org.
Chem., 2010, 1875–1884; (b) T. Jin, M. Yan and Y. Yamamoto,
ChemCatChem, 2012, 4, 1217–1229; (c) P. Abdulkin,
Y. Moglie, B. R. Knappett, D. A. Jefferson, M. Yus, F. Alonso
and A. E. H. Wheatley, Nanoscale, 2013, 5, 342–350.
4 (a) F. Pérez-Balderas, M. Ortega-Muñoz, J. Morales-
Sanfrutos, F. Hernández-Mateo, F. G. Calvo-Flores, J. A. Calvo-
Asín, J. Isac-García and F. Santoyo-González, Org. Lett.,
2003, 5, 1951–1954; (b) J. García-Álvarez, J. Díez and
J. Gimeno, Green Chem., 2010, 12, 2127–2130; (c) D. Wang,
N. Li, M. Zhao, W. Shi, C. Ma and B. Chen, Green Chem.,
2010, 12, 2120–2123; (d) S. Lal and S. Díez-González, J. Org.
Chem., 2011, 76, 2367–2373; (e) J. García-Álvarez, J. Díez,
J. Gimeno, F. J. Suárez and C. Vincent, Eur. J. Inorg. Chem.,
2012, 5854–5863.
4680–4683; (h) F. Li and T. S. A. Hor, Chem.–Eur. J., 2009,
15, 10585–10592; (i) H. A. Michaels and L. Zhu, Chem.–
Asian J., 2011, 6, 2825–2834; ( j) W. S. Brotherton,
P. M. Guha, H. Phan, R. J. Clark, M. Shatruk and L. Zhu,
Dalton Trans., 2011, 40, 3655–3665; (k) G.-C. Kuang,
P. M. Guha, W. S. Brotherton, J. T. Simmons, L. A. Stankee,
B. T. Nguyen, R. J. Clark and L. Zhu, J. Am. Chem. Soc.,
2011, 133, 13984–14001; (l) L. Li, P. S. Lopes, V. Rosa,
C. A. Figueira, M. Amélia, N. D. A. Lemos, M. T. Duarte,
T. Avilés and P. T. Gomes, Dalton Trans., 2012, 41, 5144–
5154; (m) R. Yan, K. Sander, E. Galante, V. Rajkumar,
A. Badar, M. Robson, E. El-Emir, M. F. Lythgoe, R. B. Pedley
and E. Årstad, J. Am. Chem. Soc., 2013, 135, 703–709;
(n) L. Jiang, Z. Wang, S.-Q. Bai and T. S. A. Hor, Dalton
Trans., 2013, 42, 9437–9443.
9 (a) J. C. Bayón, C. Claver and A. M. Masdeu-Bultó, Coord.
Chem. Rev., 1999, 193–195, 73–145; (b) M. Albrecht and
G. van Koten, Angew. Chem., Int. Ed., 2001, 40, 3750–3781;
(c) D. B. Rorabacher, Chem. Rev., 2004, 104, 651–697;
(d) A. M. Arink, T. W. Braam, R. Keeris, J. T. B. H.
Jastrzebski, C. Benhaim, S. Rosset, A. Alexakis and G. van
Koten, Org. Lett., 2004, 6, 1959–1962; (e) T. Jerphagnon,
G. P. M. van Klink, J. G. de Vries and G. van Koten, Org.
Lett., 2005, 7, 5241–5244; (f) C. Temple, A. Jabri,
P. Crewdson, S. Gambarotta, I. Korobkov and R. Duchateau,
Angew. Chem., Int. Ed., 2006, 45, 7050–7053; (g) A. Jabri,
C. Temple, P. Crewdson, S. Gambarotta, I. Korobkov and
R. Duchateau, J. Am. Chem. Soc., 2006, 128, 9238–9247;
(h) Y. Lee, D.-H. Lee, A. A. N. Sarjeant, L. N. Zakharov,
A. L. Rheingold and K. D. Karlin, Inorg. Chem., 2006, 45,
10098–10107; (i) M. R. Maurya, A. K. Chandrakar and
S. Chand, J. Mol. Catal. A: Chem., 2007, 278, 12–21;
( j) S.-Q. Bai and T. S. A. Hor, Chem. Commun., 2008, 3172–
3174; (k) M. R. Malachowski, M. E. Adams, D. Murray,
R. White, N. Elia, A. L. Rheingold, L. N. Zakharov and
R. S. Kelly, Inorg. Chim. Acta, 2009, 362, 1247–1252;
(l) S.-Q. Bai, L. L. Koh and T. S. A. Hor, Inorg. Chem., 2009,
48, 1207–1213; (m) G. van Koten, Organometallics, 2012, 31,
7634–7646.
5 (a) S. Díez-González, A. Correa, L. Cavallo and S. P. Nolan,
Chem.–Eur. J., 2006, 12, 7558–7564; (b) S. Díez-González
and S. P. Nolan, Angew. Chem., Int. Ed., 2008, 47, 8881–
8884; (c) F. Lazreg, A. M. Z. Slawin and C. S. J. Cazin,
Organometallics, 2012, 31, 7969–7975.
6 (a) Y.-B. Zhao, Z.-Y. Yan and Y.-M. Liang, Tetrahedron Lett.,
2006, 47, 1545–1549; (b) W. Wang, J. Wu, C. Xia and F. Li,
Green Chem., 2011, 13, 3440–3445; (c) Y. M. A. Yamada, 10 (a) S.-Q. Bai, J. Y. Kwang, L. L. Koh, D. J. Young and
S. M. Sarkar and Y. Uozumi, J. Am. Chem. Soc., 2012, 134,
9285–9290.
7 W. Wang, S. Hong, A. Tran, H. Jiang, R. Triano, Y. Liu,
X. Chen and P. Wu, Chem.–Asian J., 2011, 6, 2796–2802.
8 (a) T. R. Chan, R. Hilgraf, K. B. Sharpless and V. V. Fokin,
Org. Lett., 2004, 6, 2853–2855; (b) B. Gerard, J. Ryan,
T. S. A. Hor, Dalton Trans., 2010, 39, 2631–2636;
(b) S.-Q. Bai, S. Leelasubcharoen, X. Chen, L. L. Koh,
J.-L. Zuo and T. S. A. Hor, Cryst. Growth Des., 2010, 10,
1715–1720; (c) S.-Q. Bai, A. M. Yong, J. J. Hu, D. J. Young,
X. Zhang, Y. Zong, J. Xu, J.-L. Zuo and T. S. A. Hor, Cryst-
EngComm, 2012, 14, 961–971.
A. B. Beeler and J. A. Porco Jr., Tetrahedron, 2006, 62, 6405– 11 (a) N. Aoi, G.-E. Matsubayashi and T. Tanaka, Polyhedron,
6411; (c) V. O. Rodionov, S. I. Presolski, S. Gardinier,
Y.-H. Lim and M. G. Finn, J. Am. Chem. Soc., 2007, 129,
12696–12704; (d) N. Candelon, D. Lastécouères,
A. K. Diallo, J. R. Aranzaes, D. Astruc and J.-M. Vincent,
1987, 6, 943–946; (b) G. Tresoldi, L. Baradello, S. Lanza and
P. Cardiano, Eur. J. Inorg. Chem., 2005, 2423–2435;
(c) S.-Q. Bai, G. Y. H. Quek, L. L. Koh and T. S. A. Hor, Cryst-
EngComm, 2010, 12, 226–233.
Chem. Commun., 2008, 741–743; (e) P. S. Donnelly, 12 SMART (Version 5.631) & SAINT (Version 6.63) Software Refer-
S. D. Zanatta, S. C. Zammit, J. M. White and S. J. Williams, ence Manuals, Bruker AXS GmbH, Karlsruhe, Germany, 2000.
Chem. Commun., 2008, 2459–2461; (f) M. Meldal, Macromol. 13 G. M. Sheldrick, SADABS: a Software for Empirical Absorption
Rapid Commun., 2008, 29, 1016–1051; (g) S. Özçubukçu,
E. Ozkal, C. Jimeno and M. A. Pericàs, Org. Lett., 2009, 11,
Correction, University of Göttingen, Göttingen, Germany,
2001.
This journal is © The Royal Society of Chemistry 2013
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Paper
Dalton Transactions
14 (a) G. M. Sheldrick, SHELXS-97, Program for Crystal Struc- 18 L. R. Hanton and K. Lee, J. Chem. Soc., Dalton Trans., 2000,
ture Solution, University of Göttingen, Göttingen,Germany, 1161–1166.
1997; (b) G. M. Sheldrick, SHELXL-97, Program for Crystal 19 C. Janiak, J. Chem. Soc., Dalton Trans., 2000, 3885–3896.
Structures Refinement, University of Göttingen, Göttingen, 20 Crystallographic data for 1-(4-tert-butylbenzyl)-4-phenyl-1H-
Germany, 1997.
1,2,3-triazole: Formula C19H21N3, 296(2) K, monoclinic
space group C2/c; a = 24.148(3), b = 6.0742(7), c = 22.759(3) Å,
β = 101.336(3)°, V = 3273.2(7) Å3, Z = 8, GOF = 1.030, reflec-
tions collected: 19 159, independent reflections of 2502
[Rint = 0.0386], R1 = 0.0648, wR2 = 0.2015. For 1-(4-cyano-
benzyl)-4-phenyl-1H-1,2,3-triazole: Formula C16H12N4, 296(2)
15 B. J. Hathaway and D. E. Billing, Coord. Chem. Rev., 1970, 5,
143–207.
16 (a) P. C. Ford, E. Cariati and J. Bourassa, Chem. Rev., 1999,
99, 3625–3647; (b) V. W.-W. Yam and K. K.-W. Lo, Chem.
Soc. Rev., 1999, 28, 323–334; (c) G. F. Manbeck,
W. W. Brennessel, C. M. Evans and R. Eisenberg, Inorg.
Chem., 2010, 49, 2834–2843.
17 A. W. Addison, T. N. Rao, J. Reedijk, J. van Rijn
and G. C. Verschoor, J. Chem. Soc., Dalton Trans., 1984,
1349–1356.
ˉ
K, triclinic space group P1; a = 5.7924(3), b = 7.4171(4),
c = 15.8778(8) Å, α = 88.051(1), β = 80.394(1), γ = 74.064(1)°,
V = 646.69(6) Å3, Z = 2, GOF = 1.060, reflections collected:
16 787, independent reflections of 2348 [Rint = 0.0176],
R1 = 0.0311, wR2 = 0.0877. CCDC 939885 and 939886.
11326 | Dalton Trans., 2013, 42, 11319–11326
This journal is © The Royal Society of Chemistry 2013