Synthesis, characterization and crystal structure of a diketone based Cu(II) complex and its catalytic activity for the synthesis of 1,2,3-triazoles

Article abstract of DOI:10.1016/j.ica.2016.09.048

The synthesis and characterization of complex [Cu(dppo)₂] (dppo?=?1,3-diphenylpropane-1,3-dione) is reported. The complex has been fully characterized by FT-IR, UV–vis, elemental analysis and Cyclic Voltammetry. The paramagnetic nature of the c

Full text of DOI:10.1016/j.ica.2016.09.048

Accepted Manuscript
Research paper
Synthesis, characterization and crystal structure of a diketone based Cu(II) com-
plex and its catalytic activity for the synthesis of 1,2,3-triazoles
Samaresh Layek, Shweta Kumari, Anuradha, Bhumika Agrahari, Rakesh
Ganguly, Devendra D. Pathak
PII:
S0020-1693(16)30633-8
http://dx.doi.org/10.1016/j.ica.2016.09.048
ICA 17293
DOI:
Reference:
Inorganica Chimica Acta
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21 May 2016
23 September 2016
30 September 2016
Please cite this article as: S. Layek, S. Kumari, Anuradha, B. Agrahari, R. Ganguly, D.D. Pathak, Synthesis,
characterization and crystal structure of a diketone based Cu(II) complex and its catalytic activity for the synthesis
of 1,2,3-triazoles, Inorganica Chimica Acta (2016), doi: http://dx.doi.org/10.1016/j.ica.2016.09.048
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Synthesis, characterization and crystal structure of a diketone based Cu(II)
complex and its catalytic activity for the synthesis of 1,2,3-triazoles
Samaresh Layeka, Shweta Kumaria, Anuradhaa, Bhumika Agraharia, Rakesh Gangulyb, Devendra D. Pathaka*
a Department of Applied Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004,
India
b Division of Chemistry & Biological Chemistry, Nanyang Technological University
Singapore-639798
Email: ddpathak@yahoo.com
*Phone number: +91 9431126250
Abstract
The synthesis and characterization of complex [Cu(dppo)2] (dppo = 1,3-diphenylpropane-1,3-
dione) is reported. The complex has been fully characterized by FT-IR, UV-Vis, elemental
analysis and Cyclic Voltammetry. The paramagnetic nature of the complex was confirmed by
magnetic measurement and the square planar geometry was ascertained by single crystal X-ray
determination. The complex has been found to be a good homogeneous catalyst for the
synthesis of 1,2,3-triazole derivatives via one-pot reaction of arylboronic acids, sodium azide
and alkynes in DMF.
Keywords: Copper complex, cycloaddition, 1,2,3-triazoles
Introduction
1,2,3-Triazoles, a nitrogen-containing five membered heterocyclic compounds have
received much interest in the field of medicinal and material chemistry [1]. These compounds
have also found applications in synthesis of various agrochemicals, dyes, corrosion inhibitors,
biochemicals, polymers and other functional materials like photo-stabilizers and photographic
materials [2]. A literature survey indicates that there are several methods available for the
synthesis of 1,2,3-triazole derivatives (Scheme 1) [3-10]. The classical method involves the
thermal 1,3-dipolar cycloaddition of organic azides with alkynes, discovered by Huisgen in 1963
[11]. Owing to elevated temperature, low yields and lack of selectivity, Sharpless [12] and
Meldal [13] modified the method and found that 1,3-dipolar cycloaddition of organic azides with
alkynes could be accelerated by using Cu(I) complexes as catalyst [14]. Although initial reports
were based on the active Cu(I) catalysts, other workers also used Cu(II) species in these
1

transformations [15]. These reactions were catalyzed by a variety of Cu(II) catalysts or catalytic
mixtures such as CuSO4-ascorbate [16], immobilized Cu(II) on polymers or zeolites [17-20],
metallic copper turnings [21], and copper nanoparticles [22-23] etc. However, these methods
suffered from several drawbacks such as, explosive nature and relative instability of organic
azides [24]. The alternative approach involved an in situ generation of organic azides [25] from
aryl halides or aryl boronic acids and sodium azide.
The development of well characterized homogeneous catalysts for these organic
transformations is one of the frontier areas of current research in Chemistry. Due to different
interesting properties such as antioxidant, anti-leukemia, antimicrobial, anticancer activities and
chelating power of β-Diketones [26], herein we describe the synthesis of a copper(II) complex
[Cu(dppo)] from copper chloride and 1,3-diphenyl propane 1,3-dione(dppo) and its application
in the synthesis of 1,2,3-triazoles via one-step reaction from an arylboronic acid with sodium
azide in DMF, followed by a cyclization process with an alkyne under mild reaction conditions.
Scheme 1
Experimental
Materials and instrumentations:
All reagents and solvents for the synthesis and analysis were purchased from
commercially sources and used as received without further purification. 1,3-diphenylpropane-
1,3-dione (dppo), various phenyl boronic acids and alkynes were purchased from Merck and
Sigma Aldrich.
FT-IR spectra were recorded on a Perkin Elmer Spectrometer between 400-4000 cm-1 using KBr
pellets. Electronic absorption spectral analysis was recorded on a Shimadzu UV-1800
Spectrophotometer in the wave length range of 200-1100 nm. Elemental analyses 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 CDCl3 using TMS
as the internal Standard. ESI-MS were recorded by using a model Waters UPLC-TQD. Melting
points were recorded with Yazawa micro melting point apparatus. The electrochemical
experiments were performed on a CHI660C electrochemical analyzer under oxygen-free
conditions. The electrochemical behavior of the dppo ligand (10–3 M) and [Cu(dppo)2] complex
(10–3 M) was investigated by Cyclic Voltammetry (CV) technique using 0.1M [nBu4N][ClO4] as
a supporting electrolyte in DMF solvent at an scan rate of 100 mV S-1. The three-component
2

electrode consisted of a glassy carbon working electrode, a SCE reference electrode, and
platinum wire as counter electrode.
Synthesis of [Cu(dppo)2] complex
A methanolic solution of ligand 1,3-diphenylpropane-1,3-dione (dppo) (0.224g, 1.00 mmol) was
added dropwise to a clear solution of copper (II) chloride (0.173g, 0.5 mmol) in methanol (10
mL). The resultant mixture was stirred at room temperature for 12 h to produce a greenish
precipitate which was filtered and dried under vacuum. Yield: 0.208g (70 %), M.p: 230o C. The
diffraction quality crystals were obtained by slow evaporation of greenish methanolic solution of
the complex at room temperature. Anal. Calc. for C30H22CuO4: C, 70.25; H, 4.62. Found: C,
70.65; H, 4.35. Selected FT-IR (KBr), cm-1: ν(partial C=O) 1536, ν(C-C) 1311, ν(Cu-O) 556.
UV-Vis [ λ max(nm), ԑ ( L mol-1 cm-1)]: 277 (13550), 354 (17250), 642 (64).
Synthesis of 1,2,3-triazole derivatives
In a 25-mL round-bottom flask, phenylboronic acid (1.0 mmol), NaN3 (1.5 mmol) were
dissolved in DMF (3.5 mL) by stirring for 30 minutes. After this period, an alkyne (1.0 mmol)
dissolved in 1mL DMF was added slowly via syringe, followed by addition of 2 mol% of the
complex [Cu(dppo)2]. The contents were stirred for 8-12 h at room temperature. The progress of
the reaction was monitored by TLC. After completion of the reaction, the product was extracted
with ethyl acetate (3 x10 mL) from aqueous phase. The combined organic fractions were dried
over Na2SO4 and the solvent removed under reduced pressure to afford a crude product, which
after purification over Column chromatography using petroleum ether/ethyl acetate in 4:1 as
eluting solvents to yielded the pure product as colorless solid.
Single crystal X-ray structure determination of [Cu(dppo)2] complex
The X-ray diffraction intensity data were measured at 103 K with a Bruker Kappa
diffractometer equipped with a CCD detector, employing Mo K α radiation ( λ = 0.71073 Å),
with the SMART suite of programs [27a]. All data were processed and corrected for Lorentz and
polarization effects with SAINT and for absorption effects with SADABS [27b]. Structural
solution and refinement were carried out with the SHELXTL suite of programs [27c]. The
integration of the data using a monoclinic unit cell yielded a total of 9213 reflections to a
3

maximum θ angle of 26.47° (0.80 Å resolution), of which 2345 were independent (average
redundancy 3.929, completeness = 99.6%, R int = 5.67%, R sig = 5.24%) and 1875 (79.96%) were
greater than 2σ(F2). A summary of the crystallography data is given in table 1.
Table 1
Results and discussion
The [Cu(dppo)2] complex was synthesized by the reaction of ligand 1,3-diphenylpropane-
1,3-dione (dppo) and copper(II)chloride in a 2:1 ratio in methanol at room temperature (Scheme
2). The product was obtained as a greenish solid, insoluble in common solvents but soluble in
DMF and DMSO only. The complex was characterized by FT-IR, UV-Vis, Cyclic Voltamogram
analysis and the structure was determined by single crystal X-ray crystallography.
The FT-IR spectra of the dppo ligand (Fig. 1) exhibited a strong characteristic peak at
1549 cm-1 which is attributed to νC=O. There is also characteristic OH stretching frequency in
the enol form of 1,3diphenylpropane 1,3-dione appears as a weak and very broad band at about
3400 cm-1 region due to intramolecular hydrogen bond [28a]. The FT-IR spectrum of
[Cu(dppo)2] exhibited a peak at 1536 cm-1 due to ν
stretching. The lowering in the νC=O
stretching by 13 Cm-1 indicates that the CO group is coordinated to the metal [28b]. The FT-IR
spectrum of the free ligand indicates a νC-C stretching frequency at 1217 cm-1, however, in the
complex this stretching was obtained at 1311 cm-1. An increase in νC-C in the complex may be
ascribed to the partial double bond character of C-C bond in the ligand due to delocalization. The
band at 556 cm-1 was attributed to the νCu-O bonds, and confirmed the coordination of copper
with oxygen atom of the dppo ligand [28c].
Fig. 1
The UV-Visible spectra of the dppo ligand and its copper complex are depicted in Fig 2.
The dppo ligand shows two absorption bands at 241 nm (ԑ = 6560 L mol-1 cm-1) and 332 nm (ԑ
= 18400 L mol-1 cm-1), due to π-π* and n-π* transition of aromatic ring and C=O chromophore,
respectively. The electronic spectra of complex are characterized by bathochromic shift in the
position of these bands due to metal to ligand charge transfer [29]. An additional characteristic
band at 642 nm due to d-d transitions suggests the square planar geometry of the complex.
Generally, copper (II) square planar complexes are expected to show three spin allowed
2
2
2
2
2
2
2
2
transitions namely, B1g → 2A1g (dx - y → dz2), B1g → B2g (dx - y → dxy) and 2B1g → 2Eg (dx -
4

2
→ dxz, dyz) in the ground state [30a]. These three bands may overlap together to give a single
y
broad band at 642 in the complex [30b].
Fig. 2
The electrochemical behavior of the dppo ligand (10–3 M) and [Cu(dppo)2] complex (10–3 M)
was investigated by Cyclic Voltammetry (CV) technique using 0.1M [nBu4N][ClO4] as a
supporting electrolyte in DMF solvent at an scan rate of 100 mV S-1 (Fig. 3). The Cyclic
Voltammogram of the ligand shows a reversible peak at E1/2= -1.44 V vs. SCE (Epc=-1.48V and
Epa=-1.40V) and one
irreversible oxidation peak appears at 1.47 V vs. SCE. But in case of
copper complex, the ligand based reversible peak shifted to E1/2= -1.40 V vs. SCE along with an
irreversible oxidation peak appears at 1.52 V vs. SCE. In the Cyclic Voltammogram of the
[Cu(dppo)2] complex, it was noticed that the resting potential was at -0.022 V vs. SCE which
indicates that copper complex is in +2 oxidation state which undergoes an irreversible cathodic
reduction at E= -0.79V vs. SCE followed by the corresponded oxidation peaks at -0.1 V vs. SCE
and +0.54 V vs. SCE respectively due to the slow electron transfer process. The above
mentioned process only noticed when the Cyclic Voltammogram window was set to -1.0 V vs.
SCE to +1.0 V vs. SCE (Fig. 3c). However, upon the full scan range -1.7 V vs. SCE to -1.7 V vs.
SCE. A sharp peak at 0.173 V vs. SCE observed which may be attributed due to the formation of
radical cation at the ligand centre [31].
Fig. 3
The magnetic moment (µ) of the complex was determined on a Sherwood Scientific
magnetic balance and found to be 2.03 B.M, corresponding to one unpaired electron [32].
Therefore, the complex was paramagnetic in nature.
X-ray Crystal Study
Diffraction quality crystals were obtained by the slow evaporation of methanolic solution
of complex at room temperature and the structure of the complex has been elucidated by single-
crystal X-ray diffraction. The unit of the complex is composed of one Cu(II) ion and two 1,3-
diphenylpropane-1,3-dionate units and the complex displays a nearly ideal square planar
geometry with monoclinic shape. An ORTEP plot of this complex is shown in fig. 4. All non
hydrogen atoms were refined with anisotropic thermal parameters (Fig. 4). The selected bond
lengths and angles are given in Table 2. The structure shows that the two molecules of 1,3-
5

diphenylpropane-1,3-dione ligand are coordinated to copper in the bidentate fashion. It forms
two six-member chelate rings with O1A-Cu-O2A and O1A-Cu1-O2A bite angles of 93.11(7)
and 86.89(7), respectively. The structure of the complex adopts a square planar geometry with
O1A-Cu1-O1A and O2A-Cu1-O2A bond angles of 180 to each which are comparable with
reported square planar Cu(II) complexes [33, 34]. The bond length of Cu(1)-O(1)A and Cu(1)-
O(2)A was found to be 1.8997(17) Å and 1.9149(17), respectively, which lies in the range of
previously reported Cu(II) complexes such as, [Cu(L)(H2O)](ClO4)] and [Cu(L1)(H2O)2] [35,
36]. Where L and L1 are the abbreviations of ligands 2-[(3-methoxypropyl)thio]aniline and
pyridine-2,6-di carboxylic acid respectively. The C1-C2 and C2-C3 bond lengths were found to
be 1.398 Å and 1.396 Å respectively. These values are typical of C-C partial double bonds [37].
Table 2
Fig. 4
Catalytic Studies
The catalytic potential of the complex [Cu(dppo)2] was explored in a cycloaddition
reaction of an arylboronic acid (1 mmol) and substituted phenylacytylene (1 mmol) with NaN3
(1.5 mmol) at room temperature to form 1,2,3-triazole (Scheme 3). Initially, phenylboronic acid
and phenylacetylene were chosen as a model reactant to optimize the reaction conditions. When
the reaction was carried out with 1 mol% catalyst loading (Table 1, entry 2) under room
temperature, product is isolated in 50 % yield. It was observed that the reaction was completed in
8-10 h using 2 mol % [Cu(dppo)2] as a catalyst in DMF under atmospheric conditions at room
temperature. No significant improvement in yield of triazole was noticed when the catalyst
loading was increased from 2 mol% to 5 mol% under optimized reaction conditions (Table 3,
entry 3-4). The reaction was carried out in various solvents such as H2O, CH3CN, DCE, PhCH3
and CH3OH (Table 3). The best yield was obtained in DMF (Table 3, entry 4). All other
reactions were carried out with 2 mol % of catalyst under optimized conditions.
Scheme 3
Table 3
Different phenylboronic acids, bearing electron-donating and electron-withdrawing and
two alkynes were used (Table 4). It was found that both electron withdrawing and electron
donating groups at para position in boronic acids could be efficiently converted to the desirable
products (Table 4, entry 2-4). On the other hand, between phenylacetylene and p-tolyl
6

phenylacetylene, the later gave better yield in less time (Table 4, entry 5-7). However, meta-
substituted phenylboronic acid gave a low yield of the product as compared to para substituted
ones (Table 4, entry 8). The products were obtained as white solids, soluble in common organic
1
solvents and fully characterized by melting point, H NMR and Mass spectra. All data matches
with the literature values [38, 39]. The spectra are given in the supporting information.
Furthermore, the catalyst [Cu(dppo)2] was compared with previously reported catalysts [40] for
the synthesis of 1,2,3-triazole in terms of temperature, catalytic loading, and time etc (Table 5).
The earlier reported catalytic systems required large mol % of catalyst, high temperature and
prolong reaction time for completion of the reaction. But our catalyst [Cu(dppo)2] gave better
yields (up to 86 %) at room temperature using substantially low (only 2 mol %) catalyst loading.
The ease of synthesis, low catalyst loading, less reaction time, and high yields of the products at
just room temperature make the complex a “good catalyst”.
Table 4
Table 5
A plausible mechanism for Cu(II)-catalysed synthesis of 1,2,3-triazoles cycloaddition is
proposed in Scheme 4, based on earlier reports [41]. The proposed mechanism entails the in situ
generation of Cu(I) from Cu(II) by sodium azide. The next step of the mechanism involves the
formation of a copper(I) acetylenide complex through the coordination with alkyne. Then the in
situ generated aryl azide from arylboronic acid and sodium azide, reacts with copper(I)
acetylenide complex followed by cyclization. The last step of the catalytic cycle is the exclusion
of the Cu(I) through reductive elimination, to give the desired 1,4-disubstituted 1,2,3-triazoles.
Scheme 4
Conclusion
A new copper(II) complex [Cu(dppo)2] (dppo =1,3-diphenylpropane-1,3-dione ) has been
synthesized and fully characterized by various physicochemical and spectroscopic techniques
including single crystal X-ray diffraction. The complex has square planer geometry as confirmed
by the single crystal X-ray structure determination. The square plane is made up of four donor
oxygen atoms of the ligand, 1,3-diphenylpropane-1,3-dione. The complex has been found to be
an economic and efficient homogeneous catalyst for the synthesis of 1,2,3-triazole derivatives
via one-step reaction from an arylboronic acid, sodium azide and alkyne. The procedure does not
7

require isolation of the azide intermediates and afforded good-to-excellent yields at room
temperature without addition of any additives.
Acknowledgment
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. Samaresh Layek, Anuradha and Bhumika Agrahari acknowledge
the receipt of IIT (ISM) fellowship.
Supplementary data
CCDC 1441959 contains the supplementary crystallographic data for this paper. This
data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or mail
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List of Scheme’s caption
Scheme 1. General Methods for synthesis of 1,2,3-triazoles
Scheme 2. Synthesis of [Cu (dppo)2] complex
Scheme 3. Synthesis of 1,2,3-triazole derivatives
Scheme 4. Plausible mechanism for the synthesis of 1,2,3-triazole
List of figure’s caption
Fig. 1. FT-IR spectra of dppo ligand and [Cu(dppo)2] complex
Fig. 2. (a) UV-Vis spectra of dppo ligand (b) [Cu(dppo)2] complex and, (c) d-d transition in
UV-Vis spectrum of complex
Fig.3 (a) Cyclic Voltamogram of the ligand (dppo) , (b) [Cu(dppo)2] complex and (c)
[Cu(dppo)2] complex in the range of -1.0 V vs. SCE to +1.0 V vs. SCE at scan rates of 100 mV/s
Fig.4. ORTEP diagram of complex [Cu(dppo)2] with the atom labeling scheme (Thermal
ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity)
11

List of Table’s caption
Table 1. Crystal data and refinement parameters of [Cu (dppo)2] complex
Table 2. Some selected bond lengths (Å) and selected bond angles(°) of [Cu(dppo)2]
Table 3. Study of reaction optimization conditions
Table 4. Synthesis of 1,2,3-triazole derivatives from various arylboronic acid and alkynes in
presence of Cu(II) catalyst under the optimized reaction conditions
Table 5. A comparison study of catalyst [Cu(dppo)2] with the previous reported catalysts in
synthesis of 1,2,3-triazole
Scheme 1. General methods for synthesis of 1,2,3-triazole
Scheme 2. Synthesis of [Cu(dppo)2] complex
Scheme 3. Synthesis of 1,2,3-triazole derivatives
12

Scheme 4. Plausible mechanism of 1,2,3-triazole synthesis
Fig.1. FT-IR spectra of dppo ligand and [Cu(dppo)2] complex
Fig. 2a
Fig. 2b
Fig. 2c
13

Fig.2. (a) UV-Vis spectra of dppo ligand (b) [Cu(dppo)2] complex and, (c) d-d transition in UV-
Vis spectrum of complex
Fig.3. (a) Cyclic Voltamogram of the ligand (dppo), (b) [Cu(dppo)2] complex and (c)
[Cu(dppo)2] complex in the range of -1.0 V vs. SCE to +1.0 V vs. SCE at scan rates of 100 mV/s
Fig.4. ORTEP diagram of complex [Cu(dppo)2] (Thermal ellipsoids are drawn at the 50 %
probability level. Hydrogen atoms have been omitted for clarity)
Table 1. Crystal data and refinement parameters of [Cu(dppo)2] complex
Chemical formula
Formula weight
Temperature
C30H22CuO4
510.01 g/mol
103(2) K
Wavelength
0.71073 Å
Crystal size
0.100 x 0.120 x 0.220
mm
14

Crystal habit
yellow block
monoclinic
C2/c
Crystal system
Space group
Unit cell dimensions
a = 25.626(3) Å
b = 6.0009(5) Å
c = 16.1255(17) Å
α = 90°
β = 114.092(3)°
γ = 90°
Volume
2263.8(4) Å3
Z
4
Density (calculated)
Absorption coefficient
R int
1.496 g/cm3
1.002 mm-1
0.0567
R1[I>2δ(I)]
wR2 (all data)
0.0513
0.1145
Table 2. Selected bond lengths(Å) and bond angles(°) of [Cu(dppo)2]
Length(Å)
Bond
Bond
Angles(°)
Cu1-O1A 1.8997(17) O1A-Cu1-O1A
Cu1-O2A 1.9149(17) O1A-Cu1-O2A
180.0
93.11(7)
86.89(7)
180.0
C1-O1A
C1-C2
C2-C3
C1-C4
C3-O2A
C4-C5
C5-C6
C7-C8
1.278(3)
O1A-Cu1-O2A
1.398(3) O2A-Cu1O2A
1.396(4)
1.500(4)
1.283(3)
1.395(4)
1.385(4)
1.387(4)
O1A-Cu1-O2A
O1A-C1-C2
C2-C1-C4
86.90(7)
124.7(2)
120.8(2)
124.6(2)
120.7(2)
122.8(2)
O2A-C3-C2
C2-C3-C10
C5-C4-C1
Table 3. Study of reaction optimization conditions
15

Entry
Solvent
Catalyst
Loading
(mol %)
2
Time
(h)
Yield,
%
a
1
2
3
4
5
6
7
8
Water
DMF
12
12
8
21
50
78
75
35
53
45
25
1
2
5
5
5
5
5
DMF
DMF
8
Methanol
Acetonitrile
Toluene
12
24
18
24
1,2-Dichloroethane
a Isolated yields
Table 4. Synthesis of 1,2,3-triazoles from various arylboronic acid and alkynes in presence of
Cu(II) catalyst under the optimized reaction conditions
Entry Boronic
Acid
Phenyl-
acetylene
Products
Time
(h)
Yield*
%
1.
2.
9
8
82
86
8.5
9.5
8.5
75
70
70
3.
4.
5.
16

9
74
68
65
6.
10
12
7.
8.
*Isolated yield after work up.
Table 5. A comparison study of catalyst [Cu(dppo)2] with the previous reported catalysts in
synthesis of 1,2,3-triazole
Entry
Catalyst
Catalytic Temperature Time (h) Yield/Conv.
Ref.
loading
(mol %)
20
(oC)
(%)
1
2
3
4
Cu/SiO2
[Cu(tzol)2]
[Cu(tzol)2]
CuSO4-
70
70
70
80
12
12
12
8.5
93
47
96
89
[40a]
[40b]
[40b]
[40c]
2.0
2.4
10
sodium
ascorbate
[Cu(dppo)2]
5
2.0
RT
8.0
86
This Work
17

Graphical Abstract
18

ꢀ [Cu(dppo)2] complex was easily synthesized from CuCl2.2H2O and ligand 1,3-
diphenylpropane-1,3-dione (dppo) and the structure determined by single crystal X-ray
studies.
ꢀ The complex is used as a homogeneous catalyst for the one pot synthesis of 1,4-
disubstituted-1,2,3-triazoles from an arylboronic acids, sodium azide and alkynes.
ꢀ Good to excellent yields have been achieved at room temperature in less time.
19