2
J. Adhikary et al. / Inorganica Chimica Acta 406 (2013) 1–9
that shortcoming here we introduce a new methodology to
heterogenize homogenous catalysts. First of all we have synthes-
ised Mn(III), Fe(III) and Co(III) complexes of a salen type ligand
2.2. Materials
All chemicals were obtained from commercial sources and used
as received. Solvents were dried according to standard procedure
and distilled prior to use. Styrene, (E)-stilbene, cyclooctene,
1-octene, tert-butyl hydrogen peroxide (TBHP) were purchased
from Aldrich and used in epoxidation experiments without further
purification. Polyethylene glycol dodecyl ether (Brij-35), tetrame-
thylammoniumhydroxide (TMAOH) were purchased from Aldrich.
3-aminopropyltriethoxysilane (3-APTES), cetyl trimethyl ammo-
nium bromide (CTAB) were purchased from Spectochem and
Tartaric acid (TA) from Merck.
0
1
N,N -ethylenebis(3-formyl-5-methylsalicylaldimine) (L ) as homo-
geneous epoxidation catalyst where the salen ligand contains two
uncoordinated formyl groups. Then heterogenization of these three
structurally characterized homogeneous catalysts has been done
following the steps as schematically represented in Scheme 1.
The heterogenized catalysts thus obtained have been explored as
epoxidation catalysts employing (E)-stilbene, styrene, cyclooctene
and 1-octene as substrates in presence of tert-butyl hydrogen
peroxide (TBHP) and PhIO as terminal oxidants in two solvents,
acetonitrile and dichloromethane and their activities have been
compared with their homogeneous counterpart. Here it is to note
2.3. Preparation of the functionalized mesoporous material (M-II)
that syntheses of Mn complex and analogous complex of Fe with
ꢁ
ClO
4
as counter anion and some of their catalytic activity were
The functionalized mesoporous material (M-II) was prepared by
following the reported method [27].
reported earlier [25,26].
2
. Experimental
1
2
.4. Synthesis of ligand (L ) and homogenous catalysts
2
.1. Methods
2
, 6-Diformyl-4-methylphenol was prepared according to the
0
literature method [28]. The Schiff-base N,N -ethylenebis(3-for-
myl-5-methylsalicylaldimine) (L ) was synthesized following the
similar procedure as we reported earlier [25].
Elemental analyses (carbon, hydrogen and nitrogen) were per-
1
formed using a Perkin–Elmer 240 °C elemental analyzer. Infrared
ꢁ1
spectra (4000–500 cm ) were recorded at 27 °C using a Perkin–
Elmer RXI FT-IR spectrophotometer with KBr pellets. Electronic
spectra (800–200 nm) were obtained at 27 °C using a Shimadzu
UV-3101PC with methanol as solvent and reference. The H NMR
spectra were recorded on a Bruker AC300 spectrometer. Magnetic
2
2
.5. Synthesis of homogenous catalysts (HmC)
1
1
.5.1. MnL Clꢀ2H
2 2
O(1.2 H O) (HmC-1)
susceptibilities were measured at 27 °C using an EG and G PAR 155
vibrating sample magnetometer with Hg[Co(SCN) ] as reference;
4
HmC-1 was synthesized and characterized according to same
procedure as reported earlier [25].
diamagnetic corrections were made using Pascal’s constants. Ther-
mal analyses (TG–DTA) were carried out on a Mettler Toledo (TGA/
SDTA851) thermal analyzer in flowing dinitrogen (flow rate:
1
2
.5.2. FeL (NO
3
)ꢀ3H
2
O (HmC-2)
3
ꢁ1
HmC-2 was synthesized by drop wise addition of an aqueous
solution (20 mL) of Fe(NO O (0.404 g, 1 mmol) to a heated
3
0 cm min ). The electrospray mass spectra were recorded on a
3
)
3
ꢀ6H
2
MICROMASS Q-TOF mass spectrometer. The cyclic voltammetric
measurements were carried out in dry acetonitrile solutions with
1
suspension of L (0.352 g,1 mmol) in ethanol (50 mL). A brown col-
or developed immediately upon dissolution of the ligand. The solu-
tion was allowed to stir open to the atmosphere for 6 h. A clear
deep brown solution was obtained. The solution was kept for crys-
tallization. After a few days, brown crystals of HmC-2 (0.38 g, 75%)
ꢁ1
0
.2 M TBAP as supporting electrolyte (scan rate = 10mV s )
employing a PAR potentiostat/galvanostat model Versa Stat-II. A
three electrode system was used in which the counter and working
electrodes were platinum foils and the reference electrode was a
saturated calomel electrode. Field Emission Scanning Electron
Microscope (FE-SEM) measurement was carried out with JEOL
JSM-6700F field-emission microscope. X-ray powder diffraction
suitable for X-ray data collection were separated out. Anal. Calc. for
1
FeL (NO
4
m
1
1
3
)ꢀ3H
2
O: C, 45.98; H, 4.59; N, 8.04. Found: C, 45.68; H,
ꢁ
1
ꢁ1
3ꢁ
.60; N, 8.01%. IR (KBr):
m(C@O) 1656 cm
;
m
(C@N) 1622 cm
;
)
ꢁ
1
ꢁ1
(skeletated vibration) 1544 cm
381. UV kmax (MeOH)/nm 333, 501sh (e/dm mol cm 7100,
m(H
2
O) 3403 cm
;
m
(NO
(
XRPD) was performed on a XPERT-PRO Diffractometer monochro-
3
ꢁ1
ꢁ1
mated Cu Ka radiation (40.0 kV, 30.0 mA) at room temperature.
137).
OH
OH
OH
EtO
EtO
EtO
1
Stirr, 12hr
O
O
O
2.5.3. CoL (NO
3
)ꢀ2H
2
O (HmC-3)
+
2 3
Si(CH ) NH2
Si(CH ) NH
2
HmC-3 was synthesized by drop wise addition of an aqueous
solution (20 mL) of Co(NO O(0.291 g, 1 mmol) to a heated
suspension of L (0.352 g, 1 mmol) in ethanol (50 mL). A reddish-
brown color developed immediately upon dissolution of the ligand.
The solution was allowed to stir open to the atmosphere for 6 h. A
brown complex (0.41 g, 80%) thus precipitated was isolated by
r.t, N
2
atm
2 3
3
)
2
ꢀ6H
2
1
Material-I
3-APTES
Material-II
filtration, washed with water and dried in vacuum. Anal. Calc. for
1
CoL (NO
3
)ꢀ2H
2
O: C, 47.33; H, 4.33; N, 8.28. Found: C, 47.32; H,
H O
ꢁ1
O
2
OH2
4.35;
1624.9 cm
1546.9 cm
N, 8.30%. IR (KBr):
m
(C@O) 1660.5 cm
;
m(C@N)
O
N
N
O
O
O
O
O
Si(CH ) N
N
N
O
O
O
2
3
Reflux, 12 hr,
ꢁ1
ꢁ1
;
;
m
(NO
(H
2
O) 3330.8 cm
;
m
(skeletated vibration)
M
M
ꢁ1
ꢁ
ꢁ1 1
Si(CH ) N
o
m
3
) 1384.5 cm . H NMR (300 MHz, D
6
-DMSO):
2 3
OH
60 C
O
O
2
d 11.09 (2H, s, Ar–CHO), 8.36 (2H, s, –CH@N–), 7.66 (4H, s, Ar–H),
.18 (4H, s, N–CH –CH –N), 2.04 (6H, s, Ar–CH ). UV kmax (MeOH)/
nm 324, 410, 608sh ( /dm mol cm 22,000, 37500, 4000). TG
OH
2
4
2
2
3
3
-1
-1
HtC-1 , M=Mn
HtC-2 , M=Fe
HtC-3 , M=Co
e
HmC-1 , M=Mn
HmC-2 , M=Fe
HmC-3 , M=Co
analysis: 0.923 mg weight loss (7.22% of 12.77 mg complete: ex-
pected weight loss 7.1%) at 125 °C ESI-MS: m/z = 477.93 amu corre-
1
+
Scheme 1. Synthetic out-line of the catalysts.
sponds to [CoL ꢀ2H
2
O + MeOH] .