M.R. Maurya et al. / Inorganica Chimica Acta xxx (2013) xxx–xxx
3
1
Table 1
1,2-Dibromo-1-phenylethane: H NMR (CDCl
5
): d = 7.29–7.39 (m,
3
Crystal data and structure refinement for 3aꢀDMSO.
H, aromatic), 5.11–5.13 (q, 1 H, CH), 3.97–4.06 (septet, 2 H,
CH ) ppm.
-Phenylethane-1,2-diol: H NMR (CDCl
3
aꢀDMSO
2
1
1
3
): d = 7.29–7.39 (m, 5 H,
), 3.6 (q, 1 H of CH ),
Formula
Formula weight
T (K)
15 17 4 4
C H N O SV
400.33
100(2)
0.71073
monoclinic
P2 /n
9.5772(8)
aromatic), 4.9 (q, 1 H, CH), 3.5 (q, 1 H of CH
2.7 (br, 1 H, OH) ppm.
2
2
k (Å)
-Bromo-1-phenylethane-1-ol: 1H NMR (CDCl
2
(
3
): d = 7.29–7.39
Crystal system
Space group
a (Å)
m, 5 H, aromatic), 5.1 (q, 1 H, CH), 3.9 (septate, 2 H, CH ) ppm.
2
1
b (Å)
c (Å)
14.3085(13)
12.2414(10)
90.607(5)
1677.4(2)
4
1.585
0.745
824
0.22 ꢁ 0.20 ꢁ 0.19
2.19–24.71
ꢂ11 6 h 6 11,
ꢂ16 6 k 6 15,
ꢂ14 6 l 6 13
18198
These data match well with those reported earlier [26,27].
b (°)
2
.5.2. Oxidative bromination of trans-stilbene
Similar procedures as outlined for styrene were applied for the
oxidative bromination of trans-stilbene: trans-stilbene (0.90 g,
5 mmol), catalyst precursor (0.015 g), KBr (2.38 g, 20 mmol), 30%
3
V (Å )
Z
ꢂ3
D
calc (g cm
)
ꢂ1
Absorption coefficient (mm
F(000)
Crystal size (mm
h range for data colletion (hMin/hMax) (°)
)
aqueous H
added in four equal portions at time intervals (t = 0, 30, 60 and
0 min. of reaction time) were taken in CHCl /H O (40 mL, v/v).
2 2 4
O (2.27 g, 20 mmol) and 70% HClO (2.86 g, 20 mmol,
ꢂ3
)
9
3
2
Index ranges
After 2 h of stirring at room temperature the orange colored organ-
ic layer was separated using a separatory funnel, washed with
water and dried. The crude mass was redissolved in CH Cl ; insol-
2 2
Reflections collected
Independent reflections
2859
0.0698
uble trans-stilbene oxide was separated by filtration and then the
R
int
Completeness%/(h)
Refinement method
Restraints/parameters
99.8/(24.71°)
full-matrix least-squares on F
2859/0/256
1.047
0.0407
0.1323
solvent was evaporated. Other reaction products were separated
using a silica gel column. Elution of the column with 1% CH Cl
2 2
in n-hexane first separated a mixture of mono derivative followed
2
2
Goodness-of-fit (GOF) on F
a
by the dibromo derivative. The products were identified by GC–MS
R
1
1
(all data)b
and H NMR spectra.
wR
2
ꢂ3
1H NMR spectral data of reaction products are as follows:
Largest differences peak and hole (e Å
)
0.969 and ꢂ0.410
a
R
wR
1
=
R
= {
||F
R
o
| ꢂ |F
c
||/
R
ꢂ |F
|F
o
|.
,3-Diphenyloxirane: 1H NMR (CDCl
aromatic); 5.5 (d, 2H, CH).
-Bromo-1,2-diphenylethanol: 1H NMR (CDCl
OH); 7.37–7.52 (m, 10 H, aromatic); 5.5 (d, 2H, CH).
2
3
): d = 7.35–7.55 (m, 10 H,
b
2
2
2
4)]}1/2
.
2
[w(||F
o
|
c
| |) ]|/
R
[w(F
o
2
3
): d = 8.0 (s, 1 H,
2
.5. Catalytic studies
1
3
1,2-Dibromo-1,2-diphenylethane: H NMR (CDCl ): d = 7.1–7.4
V
(m, 10 H, aromatic); 6.15 (d, 2H, CH).
The polymer-anchored complexes PS-im[V O
2
(acpy-bhz)] (4),
V
V
2 2
PS-im[V O (acpy-inh)] (5), PS-im[V O (acpy-nah)] (6) were used
2
.5.3. Oxidation of benzoin
Benzoin (1.06 g, 5 mmol), 30% aqueous H O (1.71 g, 15 mmol),
2 2
as catalyst precursors to carry out the oxidative bromination of sty-
rene and trans-stilbene, as well as of oxidation of benzoin. Each
catalyst was allowed to swell in suitable solvent (mentioned be-
low) prior to its use.
and catalyst precursor (0.030 g) in 10 mL methanol were stirred at
reflux temperature. The progress of the reaction was monitored by
withdrawing samples at different time intervals and analyzing
them quantitatively by gas chromatography. The identities of the
products were confirmed by GC–MS. The effect of various parame-
ters such as temperature, amount of oxidant and catalyst were
checked to optimize the conditions for the best performance of
the catalyst.
2
.5.1. Oxidative bromination of styrene
Warning! HClO is potential oxidant, hence it must be handled
4
carefully: Complexes 4–6 were used as catalyst precursors to carry
out the oxidative bromination of styrene. In a typical reaction, sty-
rene (1.04 g, 10 mmol) was added to an aqueous solution (20 mL)
of KBr (3.57 g, 30 mmol) in a 100 mL reaction flask, and then
The products mainly obtained are benzil, methylbenzoate, ben-
zoic acid and benzaldehyde-dimethylacetal.
2
0 mL CH
added. After adding 70% HClO
cursors (0.0010 g), the reaction mixture was stirred at room tem-
perature. Three additional 10 mmol portions of 70% HClO were
2
Cl
2
and 30% aqueous H
2 2
O (3.40 g, 30 mmol) were
4
(1.43 g, 10 mmol) and catalyst pre-
3. Results and discussion
4
3.1. Synthesis, reactivity and solid state characteristics
further added after every 15 min with continuous stirring. The
experimental conditions (e.g. stirring speed, size of magnetic bar
and reaction flask) in all batches were kept as similar as possible.
After 1 h the orange colored organic layer was separated using a
separatory funnel, washed with water and dried. The crude mass
2 2
Complexes [VO (acpy-bhz] (1) and [VO (acpy-inh)] (2) were re-
V
2 2
ported to be mononuclear while [{V O(acpy-nah)} (l-O) ] (3) to
be dinuclear [16].
We obtained the monomeric form of 3 {[VO
2
(acpy-nah)]ꢀDMSO
was re-dissolved in CH
2
Cl
2
and insoluble material, if any, was re-
(3aꢀDMSO)}, from dimethylsulfoxide, as yellow prisms suitable for
single crystal X-ray diffraction analysis. Fig. 1 shows an ORTEP repre-
sentation of 3aꢀDMSO and Table 2 presents selected bond lengths
and angles. The complex presents an intermediate structure be-
tween the idealized square-pyramidal and trigonal–bipyramidal
extremes. In fact, the geometry around the vanadium atom can
moved by filtration. The solvent was evaporated and the reaction
products were separated using a silica gel column. Elution of the
column with 1% CH Cl in n-hexane first separated a mixture of
2 2
bromo derivatives, followed by 1-phenylethane-1,2-diol. The two
bromo derivatives were finally separated from each other using an-
other silica gel column and eluted with pure n-hexane. The prod-
be described as a distorted square-pyramidal (
monobasic tridentate acpy-nah ligand binding V through the
s
= 0.357) [28], the
1
ꢂ
V
ucts were identified by GC–MS and H NMR spectra.
1
H NMR spectral data of reaction products are as follows:
pyridine-N, imine-N and the amide-O and two oxido-O ligands.