Synthesis, crystal structure and immobilization of a new cobalt(ii) complex with a 2,4,6-tris(2-pyridyl)-1,3,5-triazine ligand on modified magnetic nanoparticles as a catalyst for the oxidation of alkanes

Article abstract of DOI:10.1039/c9nj02055a

A new Co(ii) complex with formula [Co(tptz)Cl₂]·2H₂O (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) has been synthesized and characterized by X-ray crystallography, elemental analyses and spectroscopic methods. It was then supported on modified Fe₃O₄ nanoparticles using tetraethylorthosilicate (TEOS) and (3-aminopropyl)trimethoxysilane (APTMS) and designated as a Fe₃O₄@SiO₂@APTMS@complex nanocatalyst. The prepared nanocatalyst was characterized by means of FT-IR, Raman, XPS, EDX, XRD, VSM, SEM and TEM studies. The catalytic activity of the [Co(tptz)Cl₂]·2H₂O complex and Fe₃O₄@SiO₂@APTMS@complex designated as catalysts A and B was used for oxidation of activated secondary alkanes such as fluorene, diphenyl methane, ethylbenzene, cyclooctane and adamantane. Observation of 39-99% conversions and 27-100% selectivities toward the corresponding ketones as well as the heterogeneity and reusability of the catalyst B seem promising.

Full text of DOI:10.1039/c9nj02055a

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New Journal of Chemistry
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Synthesis, crystal structure and immobilization of a new cobalt (II)
complex with 2,4,6-tris(2-pyridyl)-1,3,5-triazine ligand on
modified magnetic nanoparticles as a catalyst for the oxidation of
alkanes
View Article Online
DOI: 10.1039/C9NJ02055A
Received 00th January 20xx,
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Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
a
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a
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Zahra Azarkamanzad, Faezeh Farzaneh,* Mahboobeh Maghami and Jim Simpson
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A new Co(II) complex with formula [Co(tptz)Cl
characterized by X-ray crystallography, elemental analyses and spectroscopic methods. It was then supported on the
modified Fe nanoparticles using tetraethylorthosilicate (TEOS) and (3-aminopropyl) trimethoxysilane (APTMS) and
designated as Fe @SiO @APTMS@complex nanocatalyst. The prepared nanocatalyst was characterized by means of FT-
IR, Raman, XPS, EDX, XRD, VSM, SEM and TEM studies. The catalytic activity of [Co(tptz)Cl ]. 2H O complex and
Fe @SiO @APTMS@complex designated as catalysts A and B were used for oxidation of activated secondary alkanes
such as fluorene, diphenyl methane, ethylbenzene, cyclooctane and adamantane. Observation of 39–99% conversions and
7-100% selectivities toward the corresponding ketones as well as the heterogeneity and reusability of the catalyst B seem
promising.
2
]. 2H
2
O (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) has been synthesized and
3
O
4
3
O
4
2
2
2
3
O
4
2
2
2
1, 22
silica23 and silica
different supports including polymers,
2
4
gel, microporous and mesoporous materials such as zeolites,
Introduction
25-27
ion-exchange resins 28 and
MCM-41, SBA15 and MOF,
1
magnetic nanoparticles via non-covalent or covalent
interactions can generally produce effective heterogeneous
catalysts for numerous reactions including oxidation of alkanes
and alkenes.
The enzymatic role of cobalt compounds in biological reactions
has created a huge motivation in the design of new Co(II)
complexes. As a result, many research works have been
focused on the synthesis of new cobalt(II) compounds with
various ligands and investigation of their catalytic behaviour as
catalyst for oxidation either in homogeneous or
The recently used magnetic nanoparticles as support has some
advantages such as easy separation of catalyst by an external
1
, 29-36
1
magnetic field.
Such simple processes also avoid loss of
heterogeneous environment.
Cobalt complex compounds have been used as catalyst for
catalyst activity. Moreover, the product is un-contaminated
with a transition metal or ligand and allows the catalyst to be
recycled into the next reaction and improves its recovery rate
during separation process in comparison to conventional
centrifugation or filtration.
2
alkoxylation of aldehydes, oxidative esterification of
3
aldehydes,
dehydrogenation, transfer hydrogenation,
4
hydroboration and hydrosilylation. Oxidation of aromatic
5,
6
7
alcohols and sulphides,
cross coupling reactions,
8
9
It was also found that immobilized cobalt complex compounds
hydroformylation and C–C bond formations, catalysed by
cobalt(II)–Schiff base complexes have also been reported.10
on
Fe
the
@SiO
modified
@APTMS@complex (APTMS= (3-aminopropyl)
complex= [Co(2-hydroxy-1-
]),1
Fe @SiO
(PDMT)Cl
magnetic
particles
such
as
3
O
4
2
Oxidation is also an important technology that finds
applications in all kinds of chemical industry. It is well known
that oxidation of alkanes with high selectivity have been
accomplished with many metal ions as active species,
stabilized by coordination to a variety of ligands. The transition
metal complexes of first-row, such as iron and copper, are
trimethoxysilane,
naphthaldehyde)
2@APTMS@[Co
dimethylentriamine),
Fe @SiO
Met= metformin)
2
(DMF)
2
3
O
4
2
-
´
3
6
(PDMT= N,N ,N´´-tris(2-pyrimidinyl)
3
7
38
Fe
3
O
4
@APTMS@Co(acac) ,
2
3
O
4
2
-APTMS/CC/Met@Co(II) (CC= cyanuric chloride,
3
9
11, 12
and Co/Fe
3
O @C (Cobalt nanoparticles
4
known to catalyze the hydrocarbon oxidations.
Among
4
0
supported on magnetic core-shell structured carbon) are
active as oxidation catalysts.
them, cobalt serves as promising candidate in the C–H bond
13-16
functionalization
due to their plausible potential as
commercial catalysts, with less environmentally damaging and
quite a number of studies have been conducted.
Synthesis of a new Co(II) complex with formula [Co(tptz)Cl
2
].
2H O (tptz= 2,4,6-tris(2-pyridyl)-1,3,5-triazine) followed by
2
immobilization on the modified magnetic nanoparticles and
study of catalytic activity in the oxidation of some alkanes is
described in this presentation. Recall that (tptz) featuring three
2-pyridyl rings and a 1,3,5-triazine ring with an extended
conjugated π system, is a bulky heterocyclic organic
compound, was first synthesized by Case and Koft in 1959.41
Among the polypyridyl ligands, tptz has drawn much attention
Different Cobalt compounds such as cobalt(II) Schiff base
17,
18
complexes,
cobalt(II) porphyrins
phthalocyanine complexes have been prepared and used for
oxidation reactions.
19
and Co(II)
20
In order to heterogenized the homogeneous cobalt complexes,
a. Department of Chemistry, Faculty of Physics & Chemistry, Alzahra University,
P.O.Box 1993891176, Vanak, Tehran, Iran. Email address:
faezeh_farzaneh@yahoo.com: farzaneh@alzahra.ac.ir; Tel +9821 88258977; fax:
because of its multiple coordination sites (major, middle, and
minor) and large stabilizing π systems.42 Many transition metal
complexes of tptz also have gained much attention because of
+
9821 88041344
b.
c.
Department of Chemistry, University of Otago, PO Box 56, Dunedin 9054, New
Zealand.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
their physical, magnetic, photoluminescence properties and
43-45
their biological activities.
These complexes can also be
used in a variety of electrocatalytic and photocatalytic
reactions. In addition, several mononuclear and heteronuclear

Pl eNa es we dJ oo u nr no at l ao df jCu hs et mm i as tr rgy ins
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crystal complexes with the tptz ligand are known including
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difference Fourier map and their coordinates refinVieedw Awrtiictlhe OUnleinqe
DOI: 10.1039/C9NJ02055A
and Co2+ = 1.5 Ueq(O). The chloride ligand Cl1 was disordered over two
3
+
3+
3+
2+
2+
3+
2+
3+
Tb , Gd /Tb , Cu , Ni , Eu , Ru , Fe
4
3-45
complexes.
sites with an occupancy ratio 0.69(6):0.31(6). The minor
The homogeneity as well as the instability of reusing the disorder component was very poorly resolved suggesting that
Co(tptz)Cl ]. 2H O complex as oxidation catalyst prompted us the disorder model was less than ideal but a better model
[
2
2
to modify it by immobilizing the complex on magnetic
nanoparticles. As such, the obtained product could be used as
a novel heterogeneous and reusable catalyst for oxidation of
alkanes. Herein, we report the catalytic activity of
could not be designed. This and potential unresolved disorder
in both solvent water molecules undoubtedly contribute
significantly to the relatively poor final residuals, R1 = 10.46%.
However the structure of the complex was solved and refined
without difficulty to provide a clear picture of the complex
molecule and the uncertainties quoted for the bond distances
and angles reflect the poor residuals. The data were deposited
in Cambridge Crystallographic Data Center with deposition
number CCDC 969755. The molecular plot and packing
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Fe
3
O
4
@SiO @APTMS@complex on the oxidation of alkanes
2
such as fluorene, diphenyl methane, ethylbenzene,
cyclooctane and adamantine.
Experimental
Materials and instrumentation
5
0
diagram were drawn using Diamond and Mercury. Additional
metrical data were calculated using PLATON51 and tabular
Material and instrumentation are explained in supporting
information.
material was produced using WINGX.52 Details of the X‐ray
measurements and crystal data for complex is given in Table 1,
selected bond distances and angles in Table 2 and hydrogen
bonds are detailed in Table S1.
Preparation of [Co(tptz)Cl2]. 2H2O complex (tptz = 2,4,6-tris(2-
pyridyl)-1,3,5-triazine)
[
Co(tptz)Cl
mmol) of TPTZ in 50 mL EtOH and adding to a solution of 240 magnetite nanoparticles SCMNPs and modified SCMNPs
mg (1 mmol) of CoCl .6H O in EtOH (50 mL) with constant (Fe3O4@SiO2@APTMS)
2
]. 2H O was synthesized by dissolving 310 mg (1 Preparation of magnetic nanoparticles Fe3O4 (MNPs), silica coated
2
2
2
stirring for 2h. The reaction mixture was refluxed on a water
bath for 3h and then left to cool at 25 °C. The product was
These compounds were prepared according to the previously
reported procedures.36, 53
filtered off, washed several times with EtOH and Et O, and air
2
dried, the solid complex yield was 85% (407 mg). The green
precipitate was recrystallized by diffusion of ether into a 2:1:1
Preparation of magnetic nanoparticles Fe
In order to prepare magnetite nanoparticles Fe
solution of FeCl .4H O (0.004 mmol, 860 mg) and FeCl
3
O
4
(MNPs)
(MNPs), a
(0.008
3
O
4
CH
room temperature, dark green crystals of the complex
Co(tptz)Cl ]. 2H O formed and were filtered. Decomp. Point.
88 °C. Anal. Calc. for C18 Co N (MW = 478.20): C,
5.17; H, 3.35; N, 17.57. Found: C, 44.87; H, 3.23; N, 17.77%. IR
3
CN/MeOH/EtOH solution of the complex. After 5 days at
2
2
3
mmol 1400 mg) in deionized water (40 mL) was stirred at 85°C
for 30 minutes under nitrogen gas. Upon addition of ammonia
(25 %, 3 mL), the solution color turned from light brown to
black. After stirring for 20 minutes under these conditions, the
solution was cooled to room temperature followed by
[
2
2
3
4
H
16 Cl
2
6
O
2
-
1
(KBr pellet, cm ): 775 (—H bending mode of the aromatic
hydrogen atoms), 1558, 1530, 1482 and 1374 (C=N) and (C=C).
filtration. The magnetite precipitate was washed with H
2
O and
‐1
‐1
UV–Vis: λ max (nm) (ε, M L cm ) (MeOH): 374 (270), 291
22600), 255 (10400), 205 (15800).
36
sodium chloride solution (0.02 M).
(
Preparation of silica coated magnetite nanoparticles SCMNPs
For preparation of SCMNPs, the magnetite nanoparticles (1 g)
X-ray crystallography
X-ray crystal structure determination. Dark green crystals of were dispersed in deionized water in a 250 mL round-bottom
[Co(tptz)Cl ]. 2H O (1) were grown by diffusion of ether into a flask with sonication and then an aqueous solution of TEOS
2:1:1 CH
CN/MeOH/EtOH solution of the complex. X-ray (10% (v/v), 80 mL) was added, followed by glycerol (50 mL).
2
2
3
measurements were carried out on a Bruker APEXII CCD area The pH of the suspension was adjusted to 4.5 using glacial
detector diffractometer using graphite-monochromated MoKα acetic acid, and the mixture was then stirred and heated at 90
radiation (λ = 0.71073 Å). Intensity data were collected with
˚C for 2 h under a nitrogen atmosphere. After cooling to room
temperature, the silica coated magnetite nanoparticles was
separated from the reaction mixture using a permanent
magnet and washed several times with distilled water and
methanol.36
the APEX2 program and processed with SAINT and with
absorption corrections applied using SADABS.46 The structure
was solved by direct methods using SHELXS-9747 and refined
by full-matrix least‐squares on F2 using SHELXL‐2018/148 and
TITAN2000.49 All non‐hydrogen atoms were refined
anisotropically and all hydrogen atoms bound to carbon were
placed in the calculated positions, and their thermal
parameters were refined isotropically with Ueq = 1.2 Ueq(C).
The H atoms of the solvent water molecules were located in a
preparation
(Fe @SiO
of
aminoropropyl
modified
SCMNPs
3
O
4
2
@APTMS)
The obtained SCMNPs (2 g) were suspended in ethanol (100
mL) and then aminopropyltrimethoxysilane (APTMS) (2 mL)
was added under dry nitrogen atmosphere. The mixture was
2
| J. Name., 2012, 00, 1-3
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heated at reflux for 12 h and the resultant solid was It was readily recrystallized by diffusion of ether into a 2:1:1
View Article Online
DOI: 10.1039/C9NJ02055A
magnetically separated, washed with methanol to remove the CH
unreacted residue of silylating reagent and then dried at 80
3
CN/MeOH/EtOH solution of the complex.
5
3
˚
C.
Immobilization of [Co(tptz)Cl2]. 2H2O complex onto
Fe3O4@SiO2@APTMS)
The complex was characterized by FT-IR, UV–Vis, TGA,
elemental analysis and X-ray crystallography. The elemental
analysis results for complex were found to be entirely
consistent with its composition as determined by X-ray
crystallography.
(
To a stirring solution of prepared complex (1 mmol, 478.20
mg) in 20 mL ethanol, Fe @SiO @APTMS (1 g) was added
and the mixture heated at 90 °C for 12 h. The solid was then
magnetically separated, washed with ethanol and dried at
room temperature to afford Fe
as a brown solid and designated as catalyst B.
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Molecular and crystal structure. The crystal structure of complex
with atom-numbering is shown in Figure 1. Basic crystal data,
diffraction description and details of the structure refinement
are given in Table 1. Selected bond distances and angels are
presented in Table 2.
This complex crystallizes in the triclinic space group P -1, and
the cobalt coordination is a distorted square-pyramid. In the
structure of complex species (Figure 1), a single Co(II) metal
center binds to the tptz ligand in a tridentate fashion through a
single N atom from the central triazine ring and N atoms from
two of the three pyridyl rings in a basal disposition. Two
chloride ions complete the coordination sphere of the Co(II)
cation. one of its chloride ions (Cl2) occupying one of the basal
positions of the square pyramid. The apical site is occupied by
the other chloride ions (Cl1).
3
O
4
@SiO @APTMS@complex
2
Catalytic procedure
Catalytic experiments were carried out in a 10 mL round
bottomed flask equipped with a magnetic stirrer and a water
condenser. In a typical procedure, catalyst B (70 mg) was
dissolved in 5 ml acetonitrile. Then, alkanes (1 or 10 mmol)
and TBHP solution 70% in H
2
O (1.2 mmol, 0.16 mL or 12 mmol,
1
.6 mL) were added and the mixture heated at reflux for 12 h.
The reaction was monitored at periodic time intervals using
gas chromatography. The oxidation products were identified
by comparison of their retention times with those of the
authentic samples. At the end of the reaction, the catalyst was
separated by means of an external magnet, washed with
acetonitrile, diethyl ether and then air dried. The catalyst was
reused at least three times with slight decrease in catalytic
conversion and selectivity.
However, a more precise description of the geometry can be
obtained by calculating the τ5 index. The trigonality–index
Addison Parameter) τ = 0.14 [= (β–α)/60°, where α, β are the
two largest L–M–L angles of the coordination sphere, with τ =
and 1 for perfect square pyramid and trigonal bipyramid
55
(
0
geometries, respectively] confirms the square pyramidal
environment for Co1.
Results and discussions
Description of [Co(tptz)Cl2]. 2H2O complex structure
In this instance β is the angle N1—Co1—Cl2 = 154.2(4) see
Table 2 and α is N5—Co1—N4 = 145.7(5). Hence τ = 0.14,
closer to the value 0 required for a perfect square pyramidal
structure, which further supports the description of the
coordination geometry as a distorted square pyramid, Figure
S1. As observed in similar complexes, the tptz ligand is close
to planar with a rms deviation of 0.0688 Å from the best fit
plane through all 24 ligand atoms. The ligand plane also lies
close to the equatorial plane of the complex defined by the
Cl2, N1, N4 and N5 donor atoms with a dihedral angle of
Complex was synthesized based on our previously reported
5
4
procedure with some modification with high purity in high
yield by combination of an ethanolic solution of CoCl . 6H
2
2
O
5
6
and tptz in a stoichiometric ratio of 1:1 at room temperature.
9
.3(3)° between them. Within the tptz ligand itself the central
triazine ring subtends angles of 6.4 (7)° and 6.4 (7)° to the
coordinated N4 and N5 pyridyl rings respectively and 6.4 (6)°
to the pendant N6 ring. The N1 —Co—N4 and N1 —Co—N5
bite angles 72.8(5) and 76.6(5) are significantly smaller than
the ideal value of 90º because of the constraint imposed by
the five membered chelate rings. However these compare well
with the average value of 74.4(3) found for the 11 Co(II) tptz
complexes found in the Cambridge Structural Database.57
Other similarities to previously reported Co(II) tptz complexes
include the short Co1—N1 bond, 2.060(13) Å compared to
Co1—N4, 2.156(13) and Co1—N5, 2.136(12) involving the two
pyridyl rings. Furthermore, the Co1—Cl2 bond at 2.268(4) Å is
significantly shorter than Co1—Cl1 2.325(9) Å, a similar bond
Figure 1. The molecular structure of complex showing the atom numbering, with
ellipsoids drawn at the 50% probability level.
length variation was found in the only other CoCl complex of
2
5
8
the tptz ligand to be reported in the literature.
This journal is © The Royal Society of Chemistry 20xx
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Table 1. Selected crystallographic data and details for the structuVrieewreAfritnicelme Oenntlinoef
Co(tptz)Cl2]∙2H2O.
[
DOI: 10.1039/C9NJ02055A
Empirical formula
Formula weight
Temperature (K)
Wavelength (Ǻ)
C
18
H
16 Cl
2
Co N
6
O
2
478.20
94(2)
0.71073
Crystal system; space group
Triclinic, P -1
8.678(3)
8.791(3)
13.536(5)
101.547(12)
99.354(11)
103.124(10)
961.6(6)
2
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
0
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0
3
V (Å )
Z
-
1
Absorption coeff. (mm )
F(000)
1.199
486
1.651
-
3
D
x
(Mg m )
R
int
0.0645
0.20 × 0.11 × 0.09
2.45-25.33
3
Crystal size (mm )
θ Range for collection (°)
Index ranges
Figure 2. Overall packing of complex, viewed along the b axis direction. Hydrogen
bonds are drawn as blue dashed lines. Only one, representative example of a π…π
interaction is shown for clarity.
-8 ≤ h ≤9
9 ≤ k ≤ 8
15 ≤ l ≤ 12
6479
-
-
In the crystal, adjacent complexes are linked in a head-to tail
fashion by π…π interactions between the central triazine ring
Reflections collected
Independent reflections
Independent reflections [I > 2σ (I)]
Max. and min. transmission
Data / restraints / parameters
2078
1557
(centroid Cg3) and the pendant N6 ring (centroid Cg6) with an
inter-centroid distance Cg3-Cg6= 3.794(9) Å 6 = 2-x, 3-y, 1-z,
Figure S2, Table S1. An extensive range of O-H…Cl, O-H…O, C-
H…Cl and C-H…O hydrogen bonds, Table S1, combine with the
π…π stacking interactions form interlocking stacks of complex
and water molecules along the b axis direction, Figure 2.
1.00-0.5499
2078 / 72 / 284
Final R indices [I > 2σ (I)]
R indices (all data)
R1 = 0.1046
wR2 = 0.2536
R1 = 0.1336
wR2 = 0.2658
FT‐IR spectra. The FT-IR data of the complex are listed in the
experimental section. Meaningful information regarding the
bonding sites of the ligand molecule can be obtained by
comparing the IR spectra of the complex with free ligand. The Table 2. Selected bond lengths (Å) and angles (°) for [Co(tptz)Cl2]∙2H2O.
FT‐IR spectra of free 2,4,6‐ tris(2‐pyridyl)‐1,3,5‐ triazine (tptz)
Bond lengths (Å)
and [Co(tptz)Cl
2
]∙2H
2
O complex are shown in Figure 3a and b,
Co(1)-N(1)
Co(1)-N(4)
Co(1)-N(5)
Co(1)-Cl(2)
Co(1)-Cl(1)
2.060(13)
2.156(13)
2.136(12)
2.268(4)
2.325(9)
respectively. Free tptz displays three bands at 1524, 1468 and
‐1
‐1
1
402 cm and an intense band at 1367 cm . Observation of
these bands may be due to either C=N and C=C vibrations of
triazine and polypyridyl rings, respectively. The observed
vibrations are consistent with those reported before.44, 45, 58
The FT-IR spectrum of the complex [Co(tptz)Cl
2
]. 2H
2
O is
Bond angles (°)
N(1)-Co(1)-N(5)
N(1)-Co(1)-N(4)
N(5)-Co(1)-N(4)
N(1)-Co(1)-Cl(2)
N(5)-Co(1)-Cl(2)
N(4)-Co(1)-Cl(2)
N(1)-Co(1)-Cl(1)
N(5)-Co(1)-Cl(1)
N(4)-Co(1)-Cl(1)
Cl(2)-Co(1)-Cl(1)
similar to that of the free tptz ligand. The C=N and C=C
stretching vibrations modes of the triazine and the polypyridyl
rings of the coordinated tptz ligand appear at 1558, 1530, 1482
and 1374 cm , respectively. Compared to the free ligand,
slight shifts and splitting are observed due to the triazine and
76.6(5)
72.8(5)
145.7(5)
154.2(4)
100.3(3)
100.4(4)
97.8(4)
95.6(5)
103.5(5)
108.1(3)
-
1
4
4, 59
pyridyl nitrogens coordinated to the metal ion.
The band
-1
appearing at 3414 or 3538 cm with medium intensity is
assigned to the O—H vibration of water molecules that exist in
crystal structure.5
4
4
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Journal Name
ARTICLE
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
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6
View Article Online
DOI: 10.1039/C9NJ02055A
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
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7
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9
0
1
2
3
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7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 5. TGA/DTG curves of the complex (catalyst A)
4
00–560 ͦC temperature range. These peaks are associated
with the beginning of weight loss due to the decomposition of
some tptz ligand.54
Observation of about 44% weight loss at 700 °C is associated
with the complete removal or decomposition of tptz ligand.
The final residue is CoCl (obs.: 26% and calcd.: 27.15%).
Figure 3. The FT‐IR spectra of (a) 2,4,6‐ tris(2‐pyridyl)‐1,3,5‐triazine (tptz) and (b)
Co(tptz)Cl2]. 2H2O complex (catalyst A).
[
2
UV spectra. The electronic absorption spectrum of
[Co(tptz)Cl ]. 2H O is shown in Figure 4 exhibits three intense
absorption bands at 205, 255 and 291 nm. These sharp bands
ligand-centered (LC) are due to π π* or n π* transitions of
2
2
Characterization Fe3O4@SiO2@APTMS@ [Co(tptz)Cl2]. 2H2O
complex


the metal-bound tptz chromophores, which are somewhat Magnetite particles were synthesized as previously reported in
4
5, 54
perturbed by complexation.
at 374 nm with low intensity should be due to the d–d basic solution under nitrogen atmosphere. Subsequently,
transition.
Fe @SiO core‐shell particles obtained by addition of the
silica were modified with aminopropyl trimethoxysilane
TGA/DSC curves. As is observed in the TGA/DTG of (APTMS) and designated as Fe @SiO @APTMS. Finally,
[Co(tptz)Cl ]. 2H
O shown Figure 5, the total weight loss of the immobilization of the prepared complex on
sample is about 74%. The weight loss of the sample from 75 to Fe @SiO @APTMS resulted in the formation of the desired
100
C which is about 8% is due to the water losing in the product designated as Fe @SiO @APTMS@complex or
Observation of a broad band the literature by precipitation of iron (II) and iron (III) ions in
5
3
3
O
4
2
3
O
4
2
2
2
3
O
4
2
ͦ
3
O
4
2
complex. The sample also shows about 22% weight loss in the catalyst B (Scheme 1). The chemical analysis determination
showed 0.30% Co and 77.64% Fe in magnetic nanoparticles.
Scheme 1. Preparation steps of Fe3O4@SiO2@APTMS@complex (catalyst B).
(
tetraethyl orthosilicate (TEOS) and aminopropyl trimethoxysilane (APTMS).
Figure 4. Electronic spectra of complex (5×10-5 and 10-3 M in MeOH at 25 °C)
This journal is © The Royal Society of Chemistry 20xx
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ARTICLE
Journal Name
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
The FT-IR spectra of Fe
3
O
4
, Fe
3
O
4
@SiO
2
, Fe
3
O
4
@SiO @APTMS
2
View Article Online
DOI: 10.1039/C9NJ02055A
are shown in Figure S1, and the spectra of complex (catalyst
A), Fe @SiO @APTMS@complex (catalyst B) before and
after using as catalyst are shown in Figure 6a c, respectively.
3
O
4
2
‐
Upon immobilization of the Co complex on the modified
magnetic nanoparticles, several changes can be observed in all
frequency ranges. The appearance of vibrational bands at
-1
1
559, 1531 and 1381 cm due to the C=N and C=C vibrations
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
of triazine and polypyridyl rings for the immobilized complex,
respectively, confirms the occurrence of immobilization.
The
Fe
catalyst B) are shown in Figure 7a‐c, respectively. Raman
characteristics of cobalt(II) complex (catalyst A) (Figure 7a)
Raman
spectra
of
complex
(catalyst
A),
3
O
4
@SiO @APTMS and Fe
2
3
O
4
@SiO @APTMS@complex
2
(
−
1
shows four peaks in the regions of 100-200 cm and 200-300
−
1
−1
cm . The bands in the regions 100-300 cm are tentatively
assigned to metal-N and metal-Cl stretching vibrations and
usually the frequencies of metal-N and metal-Cl vibrations are
quite close.60-62 So, these peaks can be attributed to Co-N and
Co-Cl stretching vibrations. The peaks observed at 367, 500
Figure 7. The Raman spectra of (a) complex (catalyst A), (b) Fe3O4@SiO2@APTMS,
(
c) Fe3O4@SiO2@APTMS@complex (catalyst B).
respectively. The magnetization curve of Fe
superparamagnetic property with saturation magnetization of
about 62 emu/g. The silica coated Fe magnetite
nanoparticles and Fe @SiO nanoparticles coated with
3
O
4
exhibits
–
1
and 669 cm in the Raman spectrum of Fe
3
O
4
@SiO @APTMS
2
3
O
4
(Figure 7b), can be attributed to the symmetric and
6
3
3
O
4
2
asymmetric stretching of Fe−O and Fe−O−Si vibrations. The
Raman spectrum of Fe @SiO @APTMS@complex (Figure
c) displays four peaks at 125, 192, 350, 497, and 706 cm .
aminosilane agent also show superparamagnetic behavior with
decreased saturation magnetization to about 60.84 and 59.20
emu/g, respectively. Immobilization of complex within the
3
O
4
2
−
1
7
−
1
The presence of two peaks at 125, 192 cm due to the
complex confirms the successful immobilization of
Fe
3
O
4
@SiO
2
@APTMS surface exhibits
a
decrease in
superparamagnetic property of saturation magnetization to
about 56.80 emu/g. Recall that the superparamagnetic
[Co(tptz)Cl
2
]. 2H
2
O complex on the Fe
3
O
4
@SiO @APTMS
2
particles.
property
of
Fe
3
O
4
@SiO
2
@APTMS@complex
prevents
The relationship between the magnetization (M) and magnetic
field (H) at room temperature is evident in the hysteresis loops
shown in Figure 8.
aggregation and enables it to disperse rapidly when the
5
3, 64
magnetic field is removed.
The XRD patterns of bare magnetite and magnetite decorated
with silica, APTMS and complex before and after using as
catalyst are shown in Figure S4. As shown in Figure S4a, the
Magnetization
curves
of
Fe
3
O
4
,
Fe
3
O
4
@SiO ,
2
Fe @SiO @APTMS and Fe
3
O
4
2
3
O
4
@SiO
2
@APTMS@complex
before and after using as catalyst are shown in Figure 8a‐e,
obtained Fe
agree with the standard Fe
3
O
4
has highly crystalline cubic spinel structure in
(cubic phase) XRD spectrum
3
O
4
Figure 8. Magnetization curves of (a) Fe3O4, (b) Fe3O4@SiO2, (c)
Fe3O4@SiO2@APTMS, (d) Fe3O4@SiO2@APTMS@complex (catalyst B) before and
(e) after using as catalyst.
Figure 6. (a) Complex (catalyst A), (b, c) Fe3O4@SiO2@APTMS@complex (catalyst
B) before and after using as catalyst.
6
| J. Name., 2012, 00, 1-3
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Journal Name
JCPDSNo.19‐0629).64, 65 Magnetite has 2 theta peaks located
at 30.04°, 35.28°, 43.00°, 53.84° and 56.84°corresponding to
the (220), (311), (411), (422) and (511) faces of the crystal
structure, respectively.
ARTICLE
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
View Article Online
DOI: 10.1039/C9NJ02055A
The similar set of characteristic peaks observed for
Fe
3
O
O
4
@SiO
@SiO
2
,
Fe
3
O
4
@SiO
2
@APTMS,
Fe
3
4
2
@APTMS@complex (Figure S4b‐e) indicates the
stability of the crystalline phase of silica coating and surface
functionalization.
The EDX of the prepared nanocatalyst is shown in Figure 9a.
The presence of Co, Cl, and Fe are observed in this pattern.
The core and shell of nanocatalyst with average size are shown
in TEM images (Figure 9b). Scanning electron microscopy
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
(
SEM) images of nanoparticles Fe
catalyst B) is shown in Figure S5.
3
O
4
@SiO @APTMS@complex
2
The X-ray photoelectron spectroscopy (XPS) was used to
determine the chemical composition of the
Fe @SiO @APTMS@complex within binding energies of 0–
200 eV. The XPS spectrum of Fe @SiO @APTMS@complex
as nanocatalyst is shown in Figure 10. The presence of Fe, O, C,
Figure 10. XPS spectra of Fe3O4@SiO2@APTMS@complex (catalyst B): (a) survey
(
b) Fe 2p, (c) Cl 2p (d) Co 2p.
3
O
4
2
1
0b). Observation of characteristic C, Si, N, Co and Cl peaks
1
3
O
4
2
suggests that each step of the modification has been carried
out successfully. The positions of the Cl 2p peaks (Figure 10c) is
consistent with Co-Cl species, and the peaks appeared with
binding energies of 194.48 eV and 199.38 eV correspond to Cl
3/2 and Cl 2p1/2, respectively. The peak displaying at binding
energy of 781 eV can be attributed to the Co 2p3/2 line in
Si,
Fe
N,
@SiO
Co
@APTMS@complex is seen in this sample. In
is confirmed by the two peaks
observed at 709.88 and 723.58 eV, corresponding to Fe 2p3/2
and Fe 2p1/2 of Fe , respectively in the XPS spectrum (Figure
and
Cl
elements
in
the
3
O
4
2
addition, the presence of Fe
3
O
4
2
p
II
3
O
4
6
6, 67
accordance with earlier literature data.
not properly shaped perhaps due to the less amount of cobalt
present in Fe @SiO @APTMS@complex. As shown in Figure
0d, the Auger peaks associated with the Fe clearly overlap at
84 eV, in close proximity with the Co 2p3/2 at 781 eV, alludes
The wavy peak is
3
O
4
2
1
7
6
8
to its predominant presence in the sample. Hence, the XPS-
measurement confirms the successful synthesis of
Fe
3
O
4
@SiO @APTMS@complex.
2
Catalytic studies
Co(tptz)Cl2].2H2O (complex, designated as catalyst A) was
synthesized based on our modified previously reported
[
5
4
procedure.
The
catalytic
activity
of
[
Co(tptz)(CH3OH)Cl2].CH3OH.0.5H2O as reported before and the
prepared [Co(tptz)Cl2].2H2O were tested in the oxidation of some
alkanes in acetonitrile using TBHP as oxidant. It is important to
point out that the [Co(tptz)(CH3OH)Cl2].CH3OH.0.5H2O complex is
not active as a catalyst, whereas [Co(tptz)Cl2].2H2O, was active for
alkane oxidation.
The catalytic activity of [Co(tptz)Cl2].2H2O as catalyst A and
Fe3O4@SiO2@APTMS@complex as catalyst B were studied in the
oxidation of some alkanes in acetonitrile using TBHP as oxidant.
Flourene served for our early exploration of alkane oxidation in
order to find the optimum reaction conditions. Various parameters
such as the effect of catalyst amount, reaction time and solvent
were evaluated.
To optimize the catalyst amount, reaction was carried out using 10,
0, 50 mg of catalyst A within 4 to 10 h (Table 3) and 30, 50, 70 mg
of catalyst B within 6 to 12 h (Table 4), respectively in refluxing
acetonitrile. As seen in these Tables, whereas increasing the
amount of catalyst A from 10 to 50 mg within 10 h increases the
3
Figure 9. (a) EDX and (b) transmission electron microscopy (TEM) images of
nanoparticles Fe3O4@SiO2@APTMS@complex (catalyst B)
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ARTICLE
Journal Name
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Table 3. Effect of the amount of catalyst [Co(tptz)Cl2].2H2O complex (catalyst A) and
time on fluorene oxidationa.
It was found that whereas reaction proceeds about 13% using
View Article Online
DOI: 10.1039/C9NJ02055A
H
2
O
2
, no conversion occurred in the presence of O .
2
Finally, the effect of solvent either protic or aprotic on the
oxidation of fluorene either catalysed by [Co(tptz)Cl ].2H
complex (catalyst A) or Fe @SiO @APTMS@complex
Entry
Amount of
Catalyst (mg)
Time (h)
Conversion
Selectivity of
fluorenone (%)
(%)b
b
2
2
O
3
O
4
2
1
2
3
4
5
6
7
8
9
10
10
10
10
30
30
30
30
50
50
50
50
4
6
8
10
4
6
8
10
4
6
8
22
39
54
61
43
57
65
78
59
75
90
99
100
100
100
100
100
100
100
100
100
100
100
100
(catalyst B) is shown in Figures 11 and 12, respectively.
Based on the results indicated in these Figures, whereas
methanol and ethanol as protic solvents are not suitable,
higher conversions and selectivities toward the formation of
fluorenone occurs in aprotic solvents such as chloroform and
dichloromethane. Acetonitrile was shown as the most efficient
solvent (Figures 11 and 12).
Having established the optimal reaction conditions, we
examined the generality of this oxidation on other substrates
such as diphenylmethane, ethylbenzene, cyclooctane and
adamantane in refluxing acetonitrile using 50 mg of catalyst A
within 10 h or 70 mg of catalyst B within 12 h, respectively
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
1
0
1
12
10
a
Reaction conditions: fluorene (1 mmol), TBHP (1.2 mmol 70 wt%), CH3CN (5 mL).
b
Conversion (%) and selectivity (%) were determined by GC and GC-Mass.
(
Table 5). In order to avoid any overestimation of the catalytic
activity of the systems under investigation, the catalytic
activity (TON) of catalysts A and B have been calculated and
included in Table 5. As can be seen in Table 5, whereas
fluorene and diphenylmethane having one set of secondary
hydrogens are selectively oxidized to the corresponding
ketones (entries 1-2, Table 5), oxidation of ethylbenzene,
adamantane and cyclooctane which contain either primary
and secondary hydrogens, eight set of secondary hydrogens
and secondary or tertiary hydrogens respectively, are not
selective (entries 3-5, Table 5). Compared to catalyst A which
exhibit low TON’s, the TON’s of catalyst B are significantly
higher (Table 5).
conversion from 61 to 99% with 100% selectivity toward the
fluorennone (Table 3), increasing the amount of catalyst B
from 30 to 70 mg within 12 h increases the conversion from 19
to 42% with 100% selectivity toward the fluorennone (Table 4).
We have included the effect of either Fe
3
O
4
@SiO
2
or
Fe @SiO @APTMS in Table 4 for comparison of the effect of
3
O
4
2
complex on the oxidation conversion. As indicated in entry 13
of Table 4, no oxidation conversion is observed in the presence
of either Fe
are void of complex. Therefore, the key role effect of complex
on the oxidation reaction is concluded.
3
O
4
@SiO
2
or Fe
3
O
4
@SiO @APTMS as catalyst which
2
O
2
and H
2
2
O were used as oxidant in the oxidation of flourene.
Table 4. Effect of the amount of catalyst Fe3O4@SiO2@APTMS@complex (catalyst B)
and time on fluorene oxidationa.
Entry
Amount of
Time (h)
Conversion
Selectivity of
fluorenone (%)
(%)b
6
b
Catalyst (mg)
1
2
3
4
5
6
7
8
9
30
30
30
30
50
50
50
50
70
70
70
70
70
6
8
10
12
6
100
100
100
100
100
100
100
100
100
100
100
100
0
10
15
19
11
17
21
26
14
24
32
42
0
8
10
12
6
Figure 11. The effect of solvent on the conversion and selectivity of fluorene using
[
Co(tptz)Cl2].2H2O complex (catalyst A)
1
1
1
0
1
2
8
10
12
12
c
13
a
b
c
Reaction conditions: fluorene (1 mmol), TBHP (1.2 mmol 70 wt%), CH
3
CN (5 mL).
Conversion (%) and selectivity (%) were determined by GC and GC-Mass.
Fe @SiO or Fe @SiO @APTMS were used as catalyst.
3
O
4
2
3
O
4
2
Figure 12. The effect of solvent on the conversion and selectivity of fluorene using
Fe3O4@SiO2@APTMS@complex (catalyst B)
8
| J. Name., 2012, 00, 1-3
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Journal Name
ARTICLE
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Table 5 Results obtained for the oxidation of different alkanes in the presence of
complex1 (catalyst A) and Fe3O4@SiO2@APTMS@complex (catalyst B).
View Article Online
DOI: 10.1039/C9NJ02055A
Substrate conversion a (%)
Catalyst A Catalyst B
Product selectivity (%)
Entry
Ketone (TON)b
Catalyst A
Catalyst B
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
Fluorene
9
9
42
100 (10)
100 (6)
100 (118)
100 (112)
2
3
Figure 13. The effect of recycling of Fe3O4@SiO2@APTMS@complex as catalyst B
on oxidation of fluorene.
Diphenyl methane
40
6
4
both soluble salts were lower than that of catalyst A. This
difference should be due to the coordination of the electron-
rich tptz to Co complex. This in turn increases the oxidation
2
+
3+
ability of Co oxidation to Co accordingly.
To explore the reusability of catalyst B, the catalyst was
magnetically separated at the end of reaction and reused in
another reaction after washing several times with acetonitrile
and drying. It was found that the conversion of flourene
oxidation slightly dropped from 42 to 37% after four runs
Ethylbenzene
Cyclooctane
c
c
8
0
57
69 (8) 64 (160)
(
Figure 13). Moreover, atomic absorption spectroscopy (AAS)
with a GBC flame spectrophotometer analysis showed that the
Co content of catalyst B before and after using as catalyst were
0.30 and 0.27%, respectively. Particularly significant is that
4
5
d
d
9
4
39
87 (90)
74 (1096)
Adamantane
62 45
e
e
29 (6) 27 (126)
a
Reaction conditions: catalyst, (A: 50mg, B:70 mg), substrate (alkanes, 1mmol,
cyclooctane 10 mmol), TBHP (1.2 and 12 mmol), solvent (acetonitrile, 5 mL, reflux
at 80 °C), time (A: 10 h, B: 12 h).
b
TON is the mmol of product to mmol of cobalt present in catalyst.
c
Benzaldehyde (Cat A: 31%, Cat B: 36%) was identified as byproduct.
d
cyclooctanol (Cat A: 1%), cyclooctane dione (Cat A: 12%, Cat B:26%) were
identified as byproducts.
e
Adamantol (Cat A: 71%, Cat B: 73%) was identified as byproduct.
In order to compare the catalytic activity of soluble Co salts the reaction were
carried out under optimum reaction conditions, the conversion, selectivity and
TON for both are as follows:
2 2
For Co (acetate) : 53, 78, 3 and for Co(acac) : 47, 73, 2 respectively.
In order to see the effect of tptz ligand, the catalytic activity of
catalyst
Co(OAC)
A
.4H
with some soluble cobalt salts such as
O and Co(acac) were carried out under optimum
Scheme 2. Proposed reaction mechanism for the oxidation of alkane with the
catalyst A or B, (a) one electron oxidation-reduction of t-BuOOH with Co (II), (b)
oxidation of the alkane to the corresponding ketone.
2
2
2
reaction conditions. As seen in footnote of Table 5 and Table
S2 (see supplementary) the catalytic activity and selectivity of
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1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
utilization of the filtrate solution in a new oxidation run in the Additionally, oxidation of adamantane to the relevant alcohol
absence of catalyst did not show any catalytic activity. As such, and ketone as the major and minor products respectively
View Article Online
DOI: 10.1039/C9NJ02055A
no catalyst desorption to the solution is concluded. The hot (entry 5, Table 5) is another evidence of radical mechanism.69
filtration method was also used in order to explore the Therefore, initial coordination of TBHP to the cobalt centre of
leaching of the immobilized complex into the solution. catalyst and formation of t-BuOO and t-BuO radicals as the
Observation of no catalytic activity in the hot filtrate when reactive intermediates is conceivable (Scheme 2a). The
subjected to the reaction conditions excluded the catalyst generated t-BuO radical abstracts a hydrogen from alkane to
leaching.
afford the corresponding alkane radical (Scheme 2b). This
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
To further explore the stability of catalyst B, the FT-IR spectra radical then reacts with t-BuOO radical to give the alkyl
(
(
Figure 6b-c), VSM curves (Figure 8d-e) and XRD patterns peroxide, which finally undergo fragmentation either to
Figure S4 d-e) before and after using as catalyst were found to alcohol or ketone.38
be similar. Such observations clearly confirm the stability and Recall that rates of radical additions to alkanes are controlled
heterogeneity character of Fe
catalyst B).
3
O
4
@SiO
2
@APTMS@complex mainly by nucleophilic character of the radical and that of the
radicophile.70 It has been shown that partial polar effects are
(
experienced between the reaction centers in the resonance
To make insight into the reaction mechanism, oxidation of structure of H-atom abstraction transition state as shown in
flourene was carried out in the presence of diphenylamine as a Scheme 2.71 As such, the increasing effect of polar aprotic
radical scavenger. Observation of a decrease in the oxidation solvent on the reaction rate can be rationalized.
yield revealed that the reaction proceeds via a radical
mechanism (Scheme 2).
Table 6 Comparison of figure of merit of the present work (catalyst A and B) with other studies in the literature.
Entry
1
Catalyst
@APTMS@complex
Substrate
Flourene
Diphenyl methane
Flourene
Diphenyl methane
Flourene
Conversion (%)
Selectivity (%)
TON
65
Ref.
1
a
Fe
3
O
4
@SiO
2
40
100
88
86
65
42
40
55
64
57
100
100
98
97
90
100
100
63
82
64
65
2
1
2
3
Polymer anchored cobalt(II)
114
111
-
CoL@SMNPb
72
Fe
Fe
3
O
4
@SiO
2
@APTMS@complex (catalyst B)
Flourene
118
112
44
134
160
This
work
23
(
Present work)
Diphenyl methane
Ethylbenzene
Ethylbenzene
Ethylbenzene
4
5
Si/Al-pr-N=methyl-2-pyridylketone-Co
-APTMS-BPK-Coc
67
SiO
@SiO
2
/Al
2
O
3
3
O
4
2
@APTMS@complex (catalyst B)
(Present work)
-2@APTMS@[Co
@SiO @APTMS@complex (catalyst B)
This
work
6
7
Fe
Fe
3
O
4
@SiO
2
3
(PDMT)Cl
6
]d
Adamantane
Adamantane
37
45
26
27
100
126
37
3
O
4
2
This
(
Present work)
L1-Co(II)e
L2-Co(II)
work
73
Cyclooctane
Cyclooctane
1.25
1.95
94
48
31
87
-
-
[
Co(tptz)Cl
Present work)
N] HPW11Co(H O)O39.3H
Co(tptz)Cl ]. 2H O (catalyst A)
Present work)
C(NH )NC(ONCMe
Co(TPFPP)(CF SO
)f
Co(tptz)Cl ]. 2H O (catalyst A)
Present work)
2
]. 2H
2
O (catalyst A)
90
This
(
work
74
8
9
[(n-C
4
H
9
)
4
4
2
2
O
ethylbenzene
ethylbenzene
17.5
80
88
69
-
[
2
2
8
This
(
work
7
5
[Co{C
6
H
4
2
2
)
2
](NO
3
)
2
Adamantane
Adamantane
Adamantane
18.9
62
62
1
>1
29
57
3.1
6
75
10
3
3
[
2
2
This
(
work
a
b
c
d
e
f
Complex 1: [Co(2-hydroxy-1-naphthaldehyde)
2 2
(DMF) ]
SMNP: (γ-Fe , MNP) coated with starch, L: Schiff base ligand with (3-oxopropyl) trimethoxy silan and ethanol amine
2 3
O
APTMS: trimethoxysilylpropylamine; BPK: bipyridylketone
PDMT: N,N´,N´´-tris(2-pyrimidinyl)dimethylentriamine
4
L1, L2: N O
4
type bis(diazoimine)
TPFPP: meso-tetrakis(pentafluorophenyl)porphinato dianion
1
0 | J. Name., 2012, 00, 1-3
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1
2
3
4
View Article Online
DOI: 10.1039/C9NJ02055A
Journal Name
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
ARTICLE
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
11.
0.
M. Sarkheil and M. Lashanizadegan, J. Serb. Chem. Soc., 2016, 81, 369-382.
R. Shang, L. Ilies and E. Nakamura, Chemical reviews, 2017, 117, 9086-
Comparison with other reported systems
[
Co(tptz)Cl
Fe @SiO
with other reported systems for the oxidation of alkanes
Table 6). It was found that the catalyst B was superior to 14.
2
].2H
2
O
complex
(catalyst
A)
and
9
139.
3
O
4
2
@APTMS@complex (catalyst B) were compared 12.
W.-H. Rao and B.-F. Shi, Organic Chemistry Frontiers, 2016, 3, 1028-1047.
D. Tilly, G. Dayaker and P. Bachu, Catalysis Science & Technology, 2014, 4,
2756-2777.
1
3.
(
T. Yoshino and S. Matsunaga, Asian Journal of Organic Chemistry, 2018, 7,
1
193-1205.
many other reported catalysts in respect of conversion,
selectivity and specially TON, it was found that this catalyst
showed higher activity (TON) under reaction conditions.
15.
16.
17.
G. Pototschnig, N. Maulide and M. Schnürch, Chemistry–A European
Journal, 2017, 23, 9206-9232.
E. Tordin, M. List, U. Monkowius, S. Schindler and G. Knör, Inorganica
chimica acta, 2013, 402, 90-96.
M. F. Zaltariov, V. Vieru, M. Zalibera, M. Cazacu, N. M. Martins, L. M.
Martins, P. Rapta, G. Novitchi, S. Shova and A. J. Pombeiro, European
Journal of Inorganic Chemistry, 2017, 2017, 4324-4332.
W. Al Zoubi and Y. G. Ko, Applied Organometallic Chemistry, 2017, 31,
e3574.
M. Pereira, L. D. Dias and M. J. Calvete, ACS Catalysis, 2018.
A. Aktaş, E. T. Saka, Z. Bıyıklıoğlu, I. Acar and H. Kantekin, Journal of
Organometallic Chemistry, 2013, 745, 18-24.
S. M. Islam, K. Ghosh, R. A. Molla, A. S. Roy, N. Salam and M. A. Iqubal,
Journal of Organometallic Chemistry, 2014, 774, 61-69.
R. Wang, B. Gao and W. Jiao, Applied Surface Science, 2009, 255, 4109-
4113.
M. Arshadi, M. Ghiaci, A. Ensafi, H. Karimi-Maleh and S. L. Suib, Journal of
Molecular Catalysis A: Chemical, 2011, 338, 71-83.
Conclusions
18.
In this work, synthesis of a new Co(II) complex with formula
1
2
9.
0.
[
Co(tptz)Cl
2
]. 2H O (tptz= 2,4,6-tris(2-pyridyl)-1,3,5-triazine)
2
and characterization by elemental analyses, spectroscopic
methods, and X-ray crystallography was carried out. It was
found that this complex crystallizes in the triclinic space group
2
1.
22.
3.
-1
P , and the cobalt coordination is a distorted square-pyramid.
It was then successfully supported on the modified magnetic
2
nanoparticles using tetraethylorthosilicate (TEOS) and (3- 24.
aminopropyl) trimethoxysilane (APTMS) and designated as
L. Chen, B.-D. Li, Q.-X. Xu and D.-B. Liu, Chinese Chemical Letters, 2013, 24,
8
49-852.
2
5.
S. Bhunia, S. Jana, D. Saha, B. Dutta and S. Koner, Catalysis Science &
Technology, 2014, 4, 1820-1828.
Fe
homogeneous catalytic activity of [Co(tptz)Cl
catalyst A) and heterogeneous catalytic activity of
Fe @SiO @APTMS@complex (catalyst B) were evaluated by 28.
3
O
4
@SiO
2
@APTMS@complex
nanocatalyst.
The
2
]. 2H
2
O complex 26.
J. Gonzalez-Prior, J. I. Gutierrez-Ortiz, R. Lopez-Fonseca, E. Finocchio and B.
de Rivas, Catalysis Science & Technology, 2016, 6, 5618-5630.
J. Wu, M. Liu and H. Hou, Chemistry–A European Journal, 2018.
S. Nakagaki, K. M. Mantovani, G. Sippel Machado, K. A. Dias de Freitas
Castro and F. Wypych, Molecules, 2016, 21, 291.
Z. Azarkamanzad, F. Farzaneh, M. Maghami, J. Simpson and M. Azarkish,
Applied Organometallic Chemistry, 2018, 32, e4168.
F. Farzaneh, Y. Sadeghi, M. Maghami and Z. Asgharpour, Journal of Cluster
Science, 2016, 27, 1701-1718.
F. Farzaneh and Y. Sadeghi, Journal of Molecular Catalysis A: Chemical,
2015, 398, 275-281.
(
2
7.
3
O
4
2
the oxidation of fluorene with TBHP as oxidant in acetonitrile,
under reflux condition. Compared to the homogeneous
catalyst B, the heterogeneous catalyst A showed better 30.
catalytic activity. Finally, study of the catalyst reusability
revealed that at least four oxidation runs could be carried out
without significant reduction in catalytic activity.
2
9.
3
3
1.
2.
L. Hamidipour and F. Farzaneh, Comptes Rendus Chimie, 2014, 17, 927-
9
33.
33.
H. Veisi, A. Rashtiani, A. Rostami, M. Shirinbayan and S. Hemmati,
Polyhedron, 2019, 157, 358-366.
M. Sayyahia, M. Gorjizadehb and S. Sayyahia, Iranian Journal of Catalysis,
3
3
3
3
3
3
4.
5.
6.
7.
8.
9.
Acknowledgements
The authors would appreciate Alzahra University for financial
2
018, 8, 203-211.
S. Rayati, E. Khodaei, M. Jafarian and A. Wojtczak, Polyhedron, 2017, 133,
27-335.
3
support.
M. Mohammadikish, M. Masteri-Farahani and S. Mahdavi, Journal of
Magnetism and Magnetic Materials, 2014, 354, 317-323.
M. Sharbatdaran, F. Farzaneh, M. M. Larijani, A. Salimi, M. Ghiasi and M.
Ghandi, Polyhedron, 2016, 115, 264-275.
L. Hamidipour, F. Farzaneh and M. Ghandi, Reaction Kinetics, Mechanisms
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A. R. Faraji, S. Mosazadeh and F. Ashouri, Journal of colloid and interface
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New Journal of Chemistry
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DOI: 10.1039/C9NJ02055A
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Synthesis, crystal structure and immobilization of a new cobalt (II) complex
with 2,4,6-tris(2-pyridyl)-1,3,5-triazine ligand on modified magnetic
nanoparticles as a catalyst for the oxidation of alkanes
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Zahra Azarkamanzad, Faezeh Farzaneh, Mahboobeh Maghami and Jim Simpson
A new Co(II) complex with formula [Co(tptz)Cl
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]. 2H O (tptz= 2,4,6-tris(2-pyridyl)-1,3,5-triazine)
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has been synthesized and characterized, followed by supported on modified magnetic
nanoparticles as catalysts for the oxidation of alkanes.