Catalytic Epoxidation Property of a Mn Complex
C
III
colour of the solution containing the Mn complex and the
substrate intensified after the addition of oxidant indicating the
collected using graphite-monochromatized MoKa radiation
˚
[15]
(l 0.71073 A) at 298(2) K by v scan mode. The program
SAINT was used for integration of the diffraction profiles.
Semi-empirical absorption corrections were applied using the
[
14]
formation of oxo-metallic intermediates of the catalyst. After
completion of the oxidation reaction of the alkene, the solution
regained its initial colour which suggests that regeneration of the
catalyst takes place. Because of the insolubility of the iodosy-
larenes in common organic solvents, we did not attempt to
[
16]
SADABS program.
methods using the SHELXS program of the SHELXTL package
The structure was solved by Patterson
and refined by full-matrix least-squares methods with
[17,18]
[
14]
determine the rate law.
The percentage of conversion of
SHELXL.
All non-hydrogen atoms were refined with ani-
styrene, selectivity for styrene oxide, yield of styrene oxide for
the complex, and reaction time to obtain maximum yield using
both the oxidants are given in Table 1. The results indicate that
the complex converts styrene most efficiently in the presence of
PhIO and NaOCl. The complex as a catalyst is selective towards
the formation of styrene epoxide despite the formation of by-
products such as benzaldehyde, phenylacetaldehyde, styrene
epoxide derivative, alcohols etc.
sotropic displacement coefficients. The hydrogen atoms were
included in geometric positions and given thermal parameters
equivalent to 1.2 or 1.5 times those of the atom to which they
were attached. Crystallographic data and refinement parameters
are given in Table 2, and important inter-atomic distances and
angles are given in Table 3.
Catalytic Epoxidation of Styrene
The epoxidation reaction was carried out at room temperature in
acetonitrile under nitrogen atmosphere with constant stirring.
The composition of the reaction mixture was 2.00 mmol of
styrene, 2.00 mmol of chlorobenzene (internal standard),
Experimental
Materials and Methods
Manganese perchlorate, 5-methylsalicylaldehyde, and ethane-
1
,2-diamine were purchased from Sigma Aldrich and used as
0
.10 mmol of the manganese complex (catalyst), and 2.00 mmol
received. All other reagents were of analytical reagent grade.
Elemental analyses (C, H, and N) were performed using a
Perkin–Elmer 240C elemental analyser. IR spectra in a KBr
iodosylbenzene or sodium hypochlorite (oxidant) in 5.00 mL of
acetonitrile. When the oxidant was sodium hypochlorite, the
solution was buffered to pH 11.2 with NaH PO and NaOH. The
composition of the reaction medium was determined by GC with
styrene and styrene epoxide quantified by the internal standard
method (chlorobenzene). All other products detected by GC
were mentioned as others. The reaction time for maximum
2
4
ꢁ1
pellet (4500–500 cm ) were recorded using a Perkin–Elmer
RXI FT-IR spectrophotometer. UV-vis spectra were recorded
on a Lambda 900 spectrometer. Gas chromatography (GC)
analysis was performed with an Agilent Technologies 6890 N
network GC system equipped with a fused silica capillary col-
umn (30 m ꢂ 0.32 mm) and a FID detector.
Caution! Perchlorate and azide complexes of metal ions are
potentially explosive. Only a small amount of material should be
prepared, and it should be handled with great care.
Table 2. Crystal data and structure refinement for the complex
Parameter
Complex
2 4 14 16
72Cl Mn N O
Synthesis of the Complex
Empirical Formula
Formula weight
Temperature [K]
C
72
H
5
-Methylsalicylaldehyde (2.0 mmol, 272 mg) and ethane-1,2-
diamine (1.0 mmol, 61 mg) were mixed in a methanol solution
50 mL). The mixture was refluxed for 30 min and cooled to
1680.1
298(2)
0.71073
˚
Wavelength [A]
(
Crystal size [mm]
Crystal system
0.17 ꢂ 0.15 ꢂ 0.12
Triclinic
room temperature to give yellow precipitation. To the mixture
was added solid manganese perchlorate (1.0 mmol, 362 mg)
with magnetic stirring. The colour of the reaction mixture
changed from yellow to deep brown. Sodium azide (1.0 mmol,
Space group
P-1
Unit cell dimensions
˚
a [A]
˚
b [A]
11.925(1)
16.356(2)
21.971(2)
96.807(3)
101.857(3)
111.205(3)
3821.7(7)
2
6
3
5 mg) was then added to the mixture, and further stirred for
0 min. The filtrate was slow evaporated to give block single
c [ A˚ ]
crystals. Yield, 27 %. Anal. Calc. for C H Cl Mn N O : C
2
a [deg.]
b [deg.]
g [deg.]
7
2
72
4 14 16
5
1.47, H 4.32, N 11.67. Found: C 51.30, H 4.55, N 11.83 %. n
max
ꢁ
1
(KBr)/cm 2070 n(N ), 1620 n(C¼N), 1540, 1465, 1437, 1377,
3
˚
Volume [A ]
3
1
328, 1289, 1222, 1167, 1085 n(ClO ), 1065 n(ClO ), 1051 n
4 4
Z
(
ClO ), 973, 824, 808, 776, 738, 619.
4
ꢁ3
D
c
[g cm
]
1.460
ꢁ
1
m [mm
F(000)
]
0.790
X-Ray Crystallographic Data Collection and Refinements
1728
Single crystal X-ray data for the complex were collected on a
Bruker SMART APEX CCD diffractometer. Intensity data were
Tmin
0.8773
T
max
0.9111
Index ranges
ꢁ14 # h # 13, ꢁ19 # k # 19,
26 # l # 26
35394
ꢁ
Table 1. Catalytic epoxidation results
Measured reflections
Observed reflections [I $ 2s(I)]
Data/restraints/parameters
6374
13681/0/980
1.000
Time [h] Oxidant Conversion [%] Epoxide yield [%] Selectivity [%]
Epoxide Other
2
Goodness of fit on F
A
Final R indices [I $ 2s(I)]
R indices (all data)
R
R
1
¼ 0.0775, wR
2
2
¼ 0.1559
¼ 0.2017
A
¼ 0.2012, wR
2
3
.5
.0
PhIO
91
83
78
65
86
78
14
22
1
NaOCl
P||Fo| ꢁ |Fc||/
P
¼ [P
P
A
2
2 2
2 2 1/2
R
1
¼
|Fo|, wR
2
w(Fo ꢁ Fc ) / w(Fo ) ]
.