A new mononuclear nickel complex with 5,5′-dimethyl-2,2′-bipyridine: Synthesis, structural investigation and catalytic properties

Full text of DOI:10.1016/j.molstruc.2020.128572

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A new mononuclear nickel complex with 5,5′-dimethyl-2,2′-bipyridine: Synthesis,
structural investigation and catalytic properties
Rim Jaballi, Dhieb Atoui, Wassim Maalej, Artem Babaryk, Patricia Horcajada, Ridha
Ben Salem, Zakaria Elaoud
PII:
S0022-2860(20)30897-8
DOI:
https://doi.org/10.1016/j.molstruc.2020.128572
MOLSTR 128572
Reference:
To appear in: Journal of Molecular Structure
Received Date: 22 February 2020
Revised Date: 24 April 2020
Accepted Date: 29 May 2020
Please cite this article as: R. Jaballi, D. Atoui, W. Maalej, A. Babaryk, P. Horcajada, R. Ben Salem,
Z. Elaoud, A new mononuclear nickel complex with 5,5′-dimethyl-2,2′-bipyridine: Synthesis, structural
investigation and catalytic properties, Journal of Molecular Structure (2020), doi: https://doi.org/10.1016/
j.molstruc.2020.128572.
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Graphical Abstract
A new mononuclear nickel complex with 5,5’-dimethyl-2,2’-bipyridine:
Synthesis, Structural investigation and Catalytic properties
Rim JABALLI ,Dhieb ATOUI, Wassim MAALEJ, Artem BABARYK , Patricia HORCAJADA,
Ridha BEN SALEM , and Zakaria ELAOUD
Synopsis
Mononuclear Ni(II) complex with 5,5’dimethyl-2,2-bipyridine has been synthesized and
structurally characterized using single‐crystal X‐ray diffraction studies. Reactivity studies
indicate that the mononuclear complex is an unusually active catalyst for the Heck and
sonogaschira reaction.
TOC graphic
Crystal structure and catalyst activity of a cobalt complex, [Ni(dmbpy))(H O) ]SeO
4
2
4

A new mononuclear nickel complex with 5,5’-dimethyl-2,2’-bipyridine:
Synthesis, Structural investigation and Catalytic properties
1
2
1,*
3
3
Rim JABALLI , Dhieb ATOUI , Wassim MAALEJ , Artem BABARYK, Patricia HORCAJADA, Ridha
2
1
BEN SALEM, and Zakaria ELAOUD
1
Laboratory of Physical and Chemistry of Solid State, University of Sfax, Faculty of Sciences of Sfax,
B.P. 1171, 3000 Sfax. Tunisia.
2
Organic Chemistry Laboratory (LR17/ES08), University of Sfax, Faculty of Sciences of Sfax, B.P.
1
171, 3000 Sfax,Tunisia.
3
Advanced Porous Materials Unit, IMDEA Energy, Avda. Ramón de la Sagra, 3 28935 Móstoles-
Madrid, Spain.
AUTHOR INFORMATION
*
Corresponding author: Wassim Maalej
E-mail address: maalej_wassim@yahoo.fr
1

Abstract
The new [Ni(dmbpy)(H O) ]SeO complex (dmbpy = 5,5'-dimethyl-2,2'-bipyridine or
2
4
4
C H N ), based on mononuclear nickel(II) and bi-atomic bridging ligands has been
12
12
2
successfully synthesized by hydrothermal method. The crystals are characterized by X‐ray
single-crystal diffraction, crystallizing in the monoclinic system, space group P2 /c. Their
1
crystal structure consists of metallic cations octahedrally coordinated by four water molecules
and two nitrogen atoms coming from the organic molecule [NiN O ], and a selenate anion
2
4
2
-
(
SeO ) . Their crystal packing is ensured by a three-dimensional network of O-H…O
4
hydrogen bonds between the cation and anion moieties, and π…π interactions between the
pyridine rings of the organic moieties of the same layer. The thermal analysis discloses
dehydration between 148°C and 210°C, leading to an anhydrous compound [Ni(dmbpy]SeO4.
The study of vibrational absorption and Raman scattering spectra allows bringing additional
information to those obtained by X-ray diffraction. The optical band gap was calculated from
the UV-Vis absorbance spectra using classical Tauc relation which was found to be 3.58 eV.
The catalytic evaluation of [Ni(dmbpy)(H O) ]SeO on Heck and Sonogashira coupling
2
4
4
reactions, activated by ultrasonic irradiation, results in encouraging yields for a very short
times with a remarkable selectivity of the form (E) with respect to (Z) during the arylation of
styrene, making this complex a promising catalyst for both types of reactions. The coupling
products
of
the
Heck
and Sonogashira coupling
reaction
((Z)-
/(E)-
1
3
1
Stilbene and Diphenylacetylene, respectively) were examined by C NMR and H NMR.
These spectroscopic measurements provide extremely valuable information on the structure of
the molecules obtained
.
Keywords:
Hydrothermal synthesis, Crystal structure, X-Ray diffraction, Catalytic
evaluation
2

1
. Introduction
The chemistry of organic-inorganic compounds has been the focus of great interest for
numerous years, owing to the significant structural diversity such materials exhibit. In other
hand, they have gained divers physical properties thanks to their ability to modify optical
activity, dielectric, and magnetism properties [1-3].
In the last few years, specific interest in a category of N, N’‐bidentate ligand, owing to
their nitrogen-free doublet, they have the power to easily form a coordination bond with the
transition metals, and their interactions with selenic acid having one or more lone pairs
2
-
contribute to the production of hybrid complexes whose anions’ formula [SeO ] [4,5]. These
4
types of complex based on N, N’‐bidentate ligand is attracting much attention particularly, for
catalytic activity [6-8]. Thus, the cross-coupling reaction and the construction of a new C-C
bond has appeared in the catalysis of nickel. The latter has gained success. It possesses great
properties such as easy oxidative addition and access to multiple oxidation states, which
allowed the development of several and ingenious reactions. The cross-coupling reaction is
considered as one among the reactions catalyzed by transition metals currently developed.
These reactions are generally carried out in the presence of palladium. However, due to its
bad complications, either because of its toxicity or its high cost [9,10]. Several current
research teams are interested in studying new complexes based on other more abundant and
less expensive transition metals whose aim is to reduce the cost of reaction [11-15].
Accordingly, different metals were examined. Among these, nickel is the most brilliant.
Although the first investigation using Ni as a catalyst was initially conducted by Wenkert in
1
979 [16], its interest did not grow up to 2004 when Dankwardt et al. [17] reported a
significant increased catalytic efficiency using a Ni (0) / PCy3 system. Meanwhile, it was not
until 2008 when nickel was proposed as catalyst for the highly relevant cross-coupling
reaction [18], examining a wide range of organoboron reagents, and other nucleophiles (e.g.
3

organozinc reagents, amines, hydrosilane, and the like. Hydrogen was coupled with aryl
ethers from average to good yields [19]. Despite these results, progress within this field
remained relatively weak until the preparation of complexes based on nitrogenized ligands
that opened a new catalytic strategy, increasing the efficiency of certain reactions catalyzed
[
20, 21]. Inspired by these pioneering works, we report the synthesis of new Ni complex
based on the nitrogenized ligand 5,5'-dimethyl-2,2'-bipyridine (dmbpy or C H N ) as an
1
2
12
2
efficient catalyst in Heck and Sonogashira coupling reactions. Thus, its characterization
structural, thermal and spectroscopic) is studied here, together with the evaluation of its
catalytic activity.
. Materials and Method
(
2
2.1. Reagents and chemicals
5
,5′-Dimethyl-2,2′- dipyridine, Nickel(II) nitrate hexahydrate, Selenic acid, Styrene,
Phenylacetylene, n-hexane, Chlorobenzene, Sodium Chloride, Sodium Sulfate, Acetonitrile,
N, N-Dimethylformamide, Dimethyl sulfoxide, Tetrahydrofuran, Sodium carbonate,
Potassium carbonate, Sodium hydroxide, Triethylamine, tributylamine were purchased from
Sigma-Aldrich and used without further purification.
2
.2. Chemical preparation of [Ni(C H N )(H O) ]SeO .
12 12 2 2 4 4
Tetraaqua (5,5'-dimethyl-2,2'-bipyridine) nickel (II) selenate was prepared from 0.290
g (1 mmol) of nickel nitrate hexahydrate dissolved in 5mL of distilled water with an
equivalent amount of 5,5 '-dimethyl-2,2'-bipyridine (1 mmol, 0.18 g) previously dissolved in
7
mL of CH CN (acetonitrile) acidified with selenic acid (0.13mL, 2M).
3
The mixture was transferred to a Teflon-lined autoclave and heated at 413 K for 3 days.
The autoclave was then allowed to cool down to ambient temperature. The reaction scheme of
synthesis is shown below (Scheme 1):
2.3. General Procedure for Heck Cross-Coupling Reaction.
A mixture of 0.012 mmol of catalyst, 1.5 mmol of the base, 1 mmol of aryl halide, 1
mmol of styrene and 6 mL of the solvent was introduced in a 25 mL beaker and sonicated.
4

After the reaction, the mixture was cooled and the organic phase extracted with n-hexane and,
then, with a saturated NaCl solution [6,12,14,22]. The obtained adduct was then dried using
Na SO and ultimately, filtered. The solvent was evaporated using a rotary evaporator.
2
4
2.4. General Procedure for Sonogashira Cross-Coupling Reaction.
The mixture, obtained by adding 0.012 mmol of catalyst, 1.5 mmol of the base, 1
mmol of aryl halide, 1 mmol of phenylacetylene and 6 mL of solvent in a beaker of 25 mL,
was sonicated and the adduct followed the same procedure of extraction, filtration and
purification as that of the Heck coupling reaction [6, 23-24].
3
. Characterizations.
The data were collected at room temperature, using a Bruker Kappa APEXII equipped
with Photon II CMOS detector diffractometer with Cu Kα radiation, (λ = 1.54184 Å) at 293
2) K in the range of 78.5°<θ< 4.6° using the ω and φ scan technique. The structures were
(
solved using the SHELXS-97 program, [25] included in the WinGX program suite [26]. The
resolution of the structure was obtained using the Patterson method to locate Ni and Se atoms.
Nitrogen, carbon and oxygen atoms were found from successive Fourier calculations using
SHELXL-97 [25] via anisotropic thermal parameters. The hydrogen atoms belong to all water
molecules were found via Fourier difference maps, then restraint at fixed position and refined
isotopically. H atoms bonded to C atoms were geometrically positioned and allowed to ride
on their parent atoms, with C‐H bonds fixed at 0.93 Å. The structure was developed in the
monoclinic symmetry, with space group P2 /c. The DIAMOND 2.0 package [27] was used for
1
molecular graphics. Crystallographic data are given in Table 1. Bond distances and angles,
calculated from the final atomic coordinates, as well as probable hydrogen bonds, are listed in
Tables 2 and Tables 3. The Fractional atomic coordinates and equivalent isotropic
displacement parameters, atomic displacement parameters are in Table S1 and S2,
respectively.
5

Thermal analysis for [Ni(dmbpy)(H O) ]SeO was carried out by Differential Thermal
2
4
4
Analysis (DTA) and Thermogravimetric Analysis (TGA). The TGA was achieved under
flowing nitrogen at 20 mL/min and heated from 323 K to 923 K at 10°C/min. The DTA was
used toper form thermal treatment on the new material. The scan was carried in flowing air
with a ramp rate of 5°C/min and in the temperature range 298-873 K.
Infrared spectra were collected at room temperature on a Perkin Elmer Spectrum TM
-1
1
00 FT-IR spectrometer in the 4000-400 cm region. Raman spectra were recorded with a
LABRAM-JobinYvon setup. The incident laser power was operated about 5 mW to avoid
sample heating degradation. The excitation line was 630 nm from a Neon laser. Vibrational
frequencies of different bonding of the molecule were assigned by comparison with the
spectrum of other compounds, already published [6, 28-29].
UV–Visible absorption spectra were performed at room temperature, within the range
of 300–1100 nm, employing a Lambda 1050 UV/Vis/NIR spectrometer. BaSO was used as
4
reference. This technique makes it possible to determine the absorbance (A) and the
reflectance (R). The optical absorption spectrum of the [Ni(dmbpy)(H O) ]SeO compound
2
4
4
was recorded at room temperature in powder used in the form of pastille.
1
13
H NMR and C NMR spectra of the synthesized compounds were recorded on a
Bruker AC 400 apparatus with Fourier transform and a nominal frequency of 100 MHz.
Chemical shifts are expressed in parts per million (ppm) relative to tetramethylsilane (TMS),
used as an internal reference.
Gas chromatographic (GC) analyzes were performed using a Shimadzu GC-2014
device, to which a WBI-2014 injector and an FID-2014 detector were connected with a DB-5
capillary column. The carrier gas was nitrogen. All analyzes were processed with GC-solution
software.
6

Irradiation was guaranteed by using an ultrasonic probe (Sonopuls HD 3200 model, 20
kHz, 200 W) with an ultrasonic generator (Sonics VC 505, 300 W). The ultrasonic probe (Φ =
3
mm) was immersed directly in the reactor. The sonication was carried out at a low
frequency of 20 kHz at room temperature.
. Results and discussion
4
4.1. SEM Observations.
Hydro/solvothermal synthesis is an effective method for the synthesis of inorganic-
organic hybrid compound. In order to verify the morphology of our compound, an analysis by
scanning electron microscope (SEM), and polarizing microscope are performed. As it can be
seen in Figure S1. a/b and Figure S2 a micrograph obtained by (SEM/EDS) that appears
homogeneous in color and a picture taken by polarizing microscope of the synthesized
compound in the form of a prism.
The percentages of organic elemental analysis CHNS of [Ni(dmbpy)(H O) ]SeO is in
2
4
4
agreement with their proposed structure; Anal. Calcd. for C H NiN O Se: C, 31.44; H, 4.36;
1
2
20
2
8
N, 6.11%; found: C, 31.71 (1); H, 4. 29 (3); N, 6.49 (1)%.
.2. Crystal structure description.
The structure of [Ni(dmbpy)(H O) ]SeO compound was determined by X-ray
4
2
4
4
diffraction analysis. At room temperature, data were consistent with the monoclinic space
group P2 /c, with unit cell parameters a = 9.691 (2) Å, b = 9.753 (2) Å, c = 17.824 (4) Å, β =
1
9
3.20° (Table 1). As it can be seen in Figure 1, the asymmetric unit of title compound
contains 24 non-hydrogen atoms, including one nickel atom, one selenium atom, two nitrogen
atom, twelve carbon atoms and eight oxygen atoms. The crystal structure of
2
-
2+
[
Ni(C H N )(H O) ]SeO consists of discrete (SeO ) anions and [Ni(C H N )(H O) ]
12 12 2 2 4 4 4 12 12 2 2 4
complex cations. Ni (II) ions are octahedrally coordinated by a bidentate chelating 5,5’-
dimethyl-2,2’-bipyridine ligand and four aqua ligands in a bidentate fashion. Within the
slightly distorted octahedra of nickel, the Ni–N and Ni–OW distances vary from 2.067 (2) Å
7

to 2.070 (2) Å and from 2.034 (2) Å to 2.068 (2) Å, respectively (Table 2). The equatorial
plane of the nickel octahedra is constituted by two-donor nitrogen atoms from the organic
ligand and two water molecules (H O2W, H O3W). The two additional water molecules
2
2
(H O1W, H O4W) are located at the axial sites, exhibiting shorter distances than the others
2 2
(
H O1W, H O4W, N1, N2). This fact could justify the distortion observed from the ideal
2
2
octahedral geometry of the transition metal. Therefore, this is ascribed to the heterogeneous
environment; it is similar to those usually found for reported nickel complexes [6, 30-31]. The
shortest distance between the nickel (II) ions is equal to 7.12 (1) Å, hence, the complex
displays no significant Ni...Ni interactions. Each metallic octahedron is surrounded by four
selenate groups H-bonded in a bidentate manner (Figure 2). The structure can be described as
a succession of an equivalent organic-inorganic layers perpendicular to the crystallographic
axis (Figure 3) in the ABAB… fashion. The mineral framework of this complex is formed by
nickel octahedra and selenate tetrahedra. These layers are trapped in nitrogen pairs of the
organic molecule. They are located at y = 0.25 and y = 0.75 and those for organic chains at y
=
0 and y = 0.5 in the (b,c) planes. This type of structure exhibits remarkable similarities with
those observed in other 5,5’-dimethyl-2,2’-bipyridine template iron, zinc and nickel sulfates
6, 32-33]. It is noteworthy that the structure can also be described as alternated layers
propagating parallel to the (a, c) plane.
[
2
-
As far as the geometry of the [SeO ] anions is concerned, the Se-O bond lengths are
4
in the range 1.635 (2)–1.642 (2) Å, being comparable to those frequently found for analogous
hybrid materials [34-36]. The selenate (II) anions in the crystal present a slightly deformed
tetrahedral geometry with two bond angles distinguished from the others, 108.77 (9)° and
2
-
1
10.74 (9)° by their convergent values [109.15(9)–109.57(9)°]. The SeO anions compensate
4
the positive charges of nickel ion, also insuring the cohesion and stability of the structure.
Thereby, all the oxygen atoms of the anion participate as acceptors in hydrogen bonds,
8

accepting hydrogen atoms bonded to all water molecules. Each oxygen atom is connected to
two hydrogen bonds of the water molecule in a bidentate manner (Figure 4).
The geometric characteristics of 5,5'-dimethyl-2,2'-bipyridine are shown in Table.2.
The parallel organic cations form layers by means of π…π interactions (between antiparallel
cations, with face‐to‐face), leading to the formation of neighboring 2D layers. The planes of
the pyridines are separated by inter-planar distances of approximately 3.745 Å, lower than the
maximum value accepted for π…π interactions, i.e. around 3.8 Å [37]. Furthermore, the
crystallographic study of the title compound at room temperature clearly reveals that the
interactions are dominated by hydrogen bonds of type OW-H---O. These interactions play an
important role in the cohesion of the structure and on the formation of a three-dimensional
framework. As a result, we could identify eight different OW...O distances, varying from
2
.693 (3) Å to 2.791 (2) Å and the OW-H-O angles occurring between 169 (4)° and 179 (4)°
(Table 3).
4.3. Thermal behavior.
The thermal stability of complex Tetraaqua (5,5'-dimethyl-2,2'-bipyridine) nickel (II)
selenate was studied using thermogravimetric measurements and Differential Thermal
Analysis. The results are shown in Figure 5. Moreover, the TGA curve of
[
Ni(dmbpy)(H O) ]SeO shows that the weight loss occurs in two steps, in the temperature
2 4 4
range 25-600°C. The first step is carried out rapidly between 150°C and 210°C, and
corresponds to loss of four molecules of water, thus, leading to the anhydrous phase
[
Ni(dmbpy)]SeO , is accompanied by a low endothermic peak observed on the DTA curve at
4
1
80°C. The second step begins at 320°C and ends at 575 °C, corresponding to 59,39% weight
loss, which is the equivalent of departure an organic molecule C H N , with two exothermic
1
2
12
2
peaks observed on the DTA curve at 320°C and 444°C.
.4. Vibrational study.
4
9

Here, vibrational absorption and Raman scattering techniques were used to
characterize the complex. In both cases, there is an exchange of molecular energy of
vibrations.
For visual comparison, IR and Raman spectra of the [Ni(dmbpy)(H O) ]SeO are
2
4
4
depicted in Figure 6 and Figure 7. All the bands were attributed by comparison with the
spectrum of other metal-organic compounds [38-40]. A very broad band with a strong
-1
intensity is observed within the range 3285-3152 cm , being consistent with the displacement
of the O-H bonds due to the hydrogen bonding. However, they are not observed in Raman
-1
spectra. In addition, the bands observed in the range 1600-1400 cm are assigned to υ(C=N)
and υ(C=C) vibrations [41]. On the other hand, we detect, in the Raman spectrum, numerous
-1
-1
absorption bands with different intensity in the region 1592-1605 cm and 1220 cm and
-1
1
510 cm , assigned to stretching vibrations of C = C and C = N bonds, respectively.
According to the literature, [42-44] four modes of vibration characteristic of the group
2
-
SeO4 are observed. In our studied phase, the symmetric bending vibration υ is seen at 355
2
-1
cm with a weak band in the Raman spectrum. The asymmetric bending vibration υ is
4
-1
-1
observed in the Infrared spectrum as two peaks at 418 cm and 402 cm . Moreover, the
-1
-1
stretching mode υ of Se-O is traced at 997 cm and 839 cm in both IR and Raman,
3
2
-
respectively. In addition, the symmetric stretching vibration υ of SeO is noted in the
1
4
-1
infrared spectrum by a small band at 842 cm . In the Raman spectrum, the vibrational
-1
frequencies of Ni-O and Ni-N stretching modes in the solid phase appear at 234 cm and 348
-
1
cm .
4
.5. Optical properties.
The optical properties of nickel complexes afford a great means for the discussion of
the energy band structure. The optical absorption spectrum, given in Figure 8, indicates that
1
0

there is a series of strong absorption bands at 307 nm and 320 nm. These results can be
assigned to nitrogen-containing aromatic systems or electronic excitation in this region [27,
4
5]. In addition, a band centered at 562 nm exhibit d-d electronic transitions. The optical
energy band gap for the title compound was determinate by classical Tauc relation [46] as
written below:
n
αhυ= A(hυEg)
*
*
A is a constant called the band tailing parameter.
hν is the photon energy.
*
*
Eg is the band gap energy of the material.
is the absorption coefficient given by a= 2.303(Ab/t),(Ab is the absorbance and t is the
thickness of pastille which is 0.5 cm in our case).
n= (1/2, 3/2, 2 or 3) is the power factor of the transition mode, which is dependent upon the
*
nature of the material
The value of n = 1/2 is used for the direct transition, thus, giving direct a band gap.
2
Consequently, the plotting (αhυ) versus the photon energy (hυ), gives a straight line in a
certain region. The extrapolation of this straight line intercepts the photo energy (hυ) axis to
determinate the value of the direct optical energy gap (Eg) (Figure 9). The direct optical band
gap of the compound is found to be 3.58 eV. This value indicates that
[
Ni(dmbpy)(H O) ]SeO could be a sign of their semiconductor nature.
2 4 4
4.6. Catalytic reactivity Study.
[
Ni(dmbpy)(H O) ]SeO was studied as a catalyst for Heck and Sonogashira coupling
2
4
4
reactions. The two reaction scheme of Heck and Sonogashira coupling is shown below
scheme 2:
Currently, these reactions present the most interesting route for the synthesis of
diverse pharmaceutical and therapeutic molecules.
1
1

In the first stage, we started by the optimization of certain ultrasonic parameters. Both
reactions were tested with different amplitude values. The results found (Figure S4 (a) and
Figure S4 (b)) show that yields increase with amplitude up to a maximum value. Afterward,
these start decreasing once again. The most plausible explanation may be mainly at the
maximum rate of the gas in the reaction medium. Thus, the creation of an ultrasonic wave,
within a medium, generates the variation of pressure. At minimal pressure, the liquid can
vaporize forming gas bubbles, called cavitations. The greater the amplitude is, the higher the
rate of cavitation. The collapse of bubbles can release heat within the medium that activates
the reaction. At a maximum value, the amount of heat becomes very important. This can
cause degradation of some organic compounds accounting for the decrease of yield by
exceeding 50%.
The study of the influence of pulsation time was examined during short pulsation times, in
order to avoid sonotrode corrosion (Figure S5). Among the periods (t )/(t ) tested, 3/2 and 3/3
E
A
(s) can be considered as the best conditions with yields above 80%. The use of shorter pulse
times is not sufficient to activate the reaction even after one hour. The pulse period should be
short to avoid corrosion and can get fast to minimize the possibility of cooling the medium.
Thus, the higher the pulsation in operation (t ), the longer the creation time of the gas
E
bubbles in the medium. Therefore, the liberated heat becomes more important and can
degrade the reagents. Conversely, at a long time (t ), the mixing temperature decreases thanks
A
to the stop of the creation of bubbles, responsible for the activation of reaction. Accordingly,
the progress of the reaction decreases.
In addition, we examined [Ni(dmbpy)(H O) ]SeO as a catalyst for the chlorobenzene
2
4
4
coupling reaction with styrene in the presence of different bases in various solvents (Table 4).
Based on our latest studies, the polar solvent is the solvent of choice for this type of reaction
[
6]. The results obtained during this work are complementary. Thus, the yield found using
1
2

DMSO, DMF and MeCN are greater than 85%. However, the use of water results from
different stilbene side products. The most plausible explanation may be attributed to its protic
property [47]. A very remarkable preference of the transforms with respect to cis-stilbene.
This can be explained by the electron and steric effect of the ligand which involves the
insertion of the complex on the internal position of styrene.
Stilbene formation is elucidated by the catalytic cycle proposed by Scheme 3. Thanks to
the addition of the aryl halide to the initial complex, the degree of oxidation of nickel
increases to (IV) [48-50]. The dissociation of one of two nitrogen ligands helps the insertion
of styrene into complex (1) which results in the formation of a new unstable C-C bond (3).
Then, an internal rotation around this bond occurs, which promotes the β-elimination stilbene
and the hydride (5). At the end, the base breaks down this hydride by regenerating the initial
complex.
The study of the Sonogashira reaction, in the presence of [Ni(dmbpy)(H O) ]SeO , was
2
4
4
tested in various polar solvents (Table 5). Among them, DMF results in the highest yields that
reached 99% in the presence of Et N, 92% using Bu N and 87% with Na CO . These yields
3
3
2
3
decrease in DMSO and THF and vanish in water with a change in the reaction mixture color
that confirms the presence of side reaction caused by the protic nature of water.
In order to explain the mechanism of the chlorobenzene coupling reaction with
phenylacetylene in the presence of [Ni(dmbpy)(H O) ]SeO , we proposed the catalytic cycle
2
4
4
presented by Scheme 4. After the oxidative addition of the aryl halide to the initial complex,
nickel changes from oxidation state (II) to (IV). The dissociation of one of two nitrogen
ligands results in the complex formation (2') by increasing the acidity of the phenylacetylene
proton relative to its free state [51]. This facilitates its deprotonation by generating the
complex (3'). This latter gives rise to a reductive elimination by giving diphenylacetylene and
the regeneration of the initial state of the catalyst.
1
3

(E)-Stilbene:
1
H NMR (400 MHz, CDCl ) δ (ppm) = 7.54 (d, 4H, J =7.54 Hz), 7.39 (t, 4H, J = 7.39 Hz),
3
1
3
7
1
.29 (t, 2H, J = 7.29), 7.14 (s, 2H); C NMR (100 MHz, CDCl3) δ (ppm) = 137.37, 128.73,
28.68, 127.62, 126.52.
(Z)-Stilbene:
1
H NMR (400 MHz, CDCl ) δ (ppm) = 7.51 (d, 4H, J = 7.51 Hz), 7.35 (t, 4H, J = 7.36 Hz),
3
1
3
7
.30–7.17 (m, 2H), 7.10 (t, 2H, J= 7.12 Hz); C NMR (100 MHz, CDCl3) δ (ppm) = 137.45,
1
28.82, 127.77, 126.65.
Diphenylacetylene:
1
13
H NMR (400 MHz, CDCl ) δ (ppm) = 7.68–7.64 (m, 4H), 7.46–7.41 (m, 6H); C NMR (100
3
MHz, CDCl3) δ (ppm) = 131.73, 128.46, 128.36, 123.43, 89.56.
5
. Conclusion
In summary, the structural analyses of the new mononuclear nickel complex template
,5’-dimethyl-2,2’-bipyridine was investigated. The X‐ray diffraction of
Ni(dmbpy)(H O) ]SeO shows the distorted octahedral geometry of the nickel atoms. The
5
[
2
4
4
molecular arrangement of the complex exhibits a three-dimensional framework manifested by
the hydrogen bonds type O—H---O, giving their structural stability. Furthermore, the thermal
stability of the compound was studied DTA and TGA analysis. These measurements reveal
that the complex undergoes two thermal phenomena (dehydration and decomposition of the
organic molecule). Moreover, the spectral characterization was accomplished using FT-IR
and Raman spectroscopic studies to confirm the functional groups present in the solid phase.
Again, the optical band gap energy (Eg) of this complex is determinate by UV-Vis spectral
analysis with a value 3.58 eV. This value shows that this compound could be a sign of their
semiconductor nature. The catalytic study of Heck and Sonogashira coupling reactions in the
1
4

presence of [Ni(dmbpy)(H O) ]SeO was examined under different experimental conditions.
2
4
4
Hence, this study opens up new ways to develop Ni-complexes organic–inorganic compounds
accompanied by important catalytic properties.
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3
1
8

Table captions
Table 1. Crystal data and structure refinement details for [Ni(C H N )(H O) ]SeO .
12
12
2
2
4
4
Table 2. Selected bond distances (Å) and angles (°) for [Ni(C H N )(H O) ]SeO
4
1
2
12
2
2
4
Table 3. Hydrogen-bonding geometry (Å, °) for [Ni(C H N )(H O) ]SeO
4.
1
2
12
2
2
4
Table 4. Heck coupling reaction catalyzed by [Ni(C H N )(H O) ]SeO .
1
2
12
2
2
4
4
Table 5. Sonogashira coupling reaction in presence of [Ni(C H N )(H O) ]SeO .
1
2
12
2
2
4
4

Figure captions
Figure 1. The asymmetric unit of the [Ni(C H N )(H O) ]SeO crystal.
12
12
2
2
4
4
Figure 2. Neighboring selenate in the environment of the NiN OW octahedron in the phase
2
4
[
Ni(C H N )(H O) ]SeO .
12 12 2 2 4 4
Figure 3. The atomic arrangement of [Ni(C H N )(H O) ]SeO in projection along the a‐
1
2
12
2
2
4
4
axis.
Figure 4. Neighboring water molecules in the environment of the SeO tetrahedron in the
4
phase [Ni(C H N )(H O) ]SeO .
1
2
12
2
2
4
4
Figure 5. Thermogravimetric and Differential Thermal Analysis plot for
Ni(C H N )(H O) ]SeO .
[
12
12
2
2
4
4
Figure 6. Experimental IR spectrum of the Ni(C H N )(H O) ]SeO .
1
2
12
2
2
4
4
Figure 7. Experimental Raman Spectrum of the Ni(C H N )(H O) ]SeO .
1
2
12
2
2
4
4
Figure 8. UV–Vis absorption spectrum of the [Ni(C H N )(H O) ]SeO .
1
2
12
2
2
4
4
Figure 9. Determination of the optical band gap of [Ni(C H N )(H O) ]SeO by UV–Vis
12
12
2
2
4
4
absorption spectrum.

Scheme captions
Scheme 1. The synthesis reaction of [Ni(C H N )(H O) ]SeO
4
1
2
12
2
2
4
Scheme 2. Reaction scheme of Heck and Sonogashira coupling.
Scheme 3. Proposed general catalytic mechanism of the Heck coupling reaction catalyzed by
[
Ni(C H N )(H O) ]SeO
12 12 2 2 4 4
Scheme 4. Proposed general catalytic mechanism of the Sonogashira coupling reaction
catalyzed by [Ni(C H N )(H O) ]SeO
4
1
2
12
2
2
4

Table 1. Crystal data and structure refinement details for [Ni(C H N )(H O) ]SeO .
12
12
2
2
4
4
Color/Shape
formula
Prism, light blue
[Ni(C H N )(H O) ]SeO
4
12
12
2
2
4
Mr
457.97
Crystal system
Space group
Temperature (K)
a (Ǻ)
Monoclinic
P2 /c
1
293(2)
9.6916 (2)
9.7534 (2)
17.8240 (4)
93.20°
b (Ǻ)
c (Ǻ)
β (°)
3
Volume(Å )
1682.20 (6)
4
Z
-1
µ( mm )
4.55
Crystal size (mm)
F (000)
0.13 × 0.12 × 0.11
928
No. of measured, independent and
observed [I >2σ(I)] reflections
Radiation, λ(Å)
Rint
48664, 3579, 3575
Cu Kα radiation, λ = 1.54184 Å
0.037
Range of h, k, l
−11/12, -12/12, -22/22
2
2
R[F > 2σ(F )]
0.032
0.085
1.08
2
wR(F )
S
No. of reflections
3579
No. of parameters
Δρmax, Δρmin (e Å )
CCDC no.
249
0.41, -1.04
1887612
-3

Table 2. Selected bond distances (Å) and angles (°) for [Ni(C H N )(H O) ]SeO .
1
2
12
2
2
4
4
O1W—Ni
O2W—Ni
O3W—Ni
O4W—Ni
N1—Ni
N2—Ni
O1—Se
O2—Se
O3—Se
O4—Se
C1—N1
C5—N1
C6—N2
C10—N2
C2—C1
O1W—Ni—N1
O1W—Ni—N1
O1W—Ni—O4W
O1W—Ni—O3W
O1W—Ni—N2
O1W—Ni—O2W
O2W—Ni—N1
O3W—Ni—N1
O3W—Ni—O2W
O3W—Ni—N2
O4W—Ni—N1
O4W—Ni—N2
O4W—Ni—O3W
O4W—Ni—N1
N2—Ni—N1
O4W—Ni—O2W
N2—Ni—O2W
C10—N2—Ni
C6—N2—Ni
C1—N1—Ni
O1—Se—O3
O2—Se—O1
O2—Se—O3
O4—Se—O3
O4—Se—O2
O4—Se—O1
2.034 (2)
2.068 (2)
2.061 (2)
2.047 (2)
2.070 (2)
2.067 (2)
1.637 (2)
1.636 (2)
1.642 (2)
1.635 (2)
1.337 (3)
1.352 (3)
1.350 (3)
1.342 (3)
1.390 (3)
92.81 (1)
92.81 (1)
173.28 (1)
89.39 (9)
91.31 (9)
88.24 (9)
176.00 (8)
95.38 (8)
88.49 (7)
175.36 (8)
92.69 (9)
93.44 (8)
86.26 (8)
92.69 (9)
80.00 (8)
86.53 (8)
96.12 (8)
126.83 (2)
114.27 (2)
126.85 (2)
108.77 (9)
109.17 (9)
109.15 (9)
109.40 (9)
110.74 (9)
109.57 (9)
C2—C11
C4—C3
C5—C4
C6—C5
C7—C6
C8—C7
C9—C8
C10—C9
C9—C12
C6—N2
C10—N2
C2—C1
C2—C11
C4—C3
C5—C4
N1—C1—C2
N1—C5—C6
N1—C5—C4
N2—C6—C5
N2—C6—C7
N2—C10—C9
C1—C2—C11
C1—N1—C5
C3—C2—C1
C3—C2—C11
C3—C4—C5
C4—C3—C2
C4—C5—C6
C6—C7—C8
C7—C6—C5
C8—C9—C12
C8—C9—C10
C8—C9—C12
C9—C8—C7
C10—N2—C6
1.504 (4)
1.380 (4)
1.384 (3)
1.484 (3)
1.383 (3)
1.388 (4)
1.386 (4)
1.387 (3)
1.504 (4)
1.350 (3)
1.342 (3)
1.390 (3)
1.504 (4)
1.380 (4)
1.384 (3)
123.60 (2)
115.70 (2)
120.70 (2)
115.90 (2)
120.90 (2)
123.70 (2)
120.50 (3)
119.00 (2)
116.70 (2)
122.90 (2)
119.30 (2)
120.60 (2)
123.50(2)
119.50 (2)
123.20 (2)
122.60 (2)
116.90 (2)
122.60 (2)
120.10 (2)
118.90 (2)

Table 3. Hydrogen-bonding geometry (Å, °) for [Ni(C H N )(H O) ]SeO
1
2
12
2
2
4
4.
D—H···A
D—H
H···A
D···A
D—H···A
O1W—H1A···O4
0.70 (4)
0.68 (4)
0.89 (4)
0.85 (4)
0.84 (4)
0.79 (4)
0.78 (4)
0.69 (4)
2.02 (4)
2.01 (4)
1.89 (4)
1.94 (4)
1.94 (4)
1.99 (4)
1.92 (4)
2.03 (4)
2.715 (3)
2.693 (3)
2.769 (2)
2.791 (2)
2.769 (3)
2.769 (3)
2.706 (3)
2.726 (3)
172 (4)
174 (5)
172 (3)
176 (4)
169 (4)
173 (3)
179 (4)
175 (4)
i
O1W—H1B···O1
O2W—H2A···O3
iii
O2W—H2B···O2
i
O3W—H3A···O4
ii
O3W—H3B···O1
iii
O4W—H4A···O3
ii
O4W—H4B···O2
Symmetry codes : (i) −x+2, y−1/2, −z+1/2; (ii) x, y−1, z; (iii) −x+1, y−1/2,
z+1/2.
−

Table 4. Heck coupling reaction catalyzed by [Ni(C H N )(H O) ]SeO .
12
12
2
2
4
4
a
Entry
Solvent
Base
Yield (%) E/Z
1
2
3
4
5
6
7
DMSO
DMSO
DMSO
DMF
Na CO
88/11
86/13
95/4
91/9
87/11
-
2
3
Bu N
3
K CO
2
3
Na CO
2
3
DMF
NaOH
H O
2
Na CO
2
3
MeCN
Na CO
94/6
2
3
0
2
.012 mmol of catalyst, 1.5 mmol of base, 1 mmol of aryl halide, 1 mmol of styrene, 6 mL of solvent, US,
5 °C for 1h. the yields were measured by GC using dichloromethane as solvent.
a

Table 5. Sonogashira coupling reaction in presence of [Ni(C H N )(H O) ]SeO .
1
2
12
2
2
4
4
a
Entry
Solvent
DMF
Base
Yield (%)
1
Na CO
87
2
3
2
3
4
5
6
7
8
DMF
DMF
Et N
99
92
46
63
55
-
3
Bu N
3
DMSO
DMSO
THF
NaOH
Bu N
3
Bu N
3
H O
2
NaOH
H O
2
Bu N
-
3
0
6
.012 mmol of catalyst, 1.5 mmol of base, 1 mmol of aryl halid, 1 mmol of phenylacetylene,
mL of solvent, US, 25 °C. the yields were measured by GC using dichloromethane as solvent.
a