Asymmetric epoxidation of unfunctionalized olefins catalyzed by Jacobsen's catalyst on alkoxyl-modified zirconium poly (styrene-phenylvinylphosphonate)-phosphate (ZPS-PVPA)

Article abstract of DOI:10.1016/j.jorganchem.2016.06.005

New chiral Jacobsen's catalysts grafted onto alkoxyl-modified ZPS-PVPA are synthesized and applied in asymmetric epoxidations of unfunctionalized olefins. Specially, the supported catalysts indicate excellent catalytic activities (conv%, up to 96; sele%, up to 96; ee%, up to >99) in the absence of N-methylmorpholine N-oxide (NMO) by virtue of the special configurations of the catalysts. The superior stability (recycling for ten times) and the comfortable dispositions in large-scale reactions (such as 200 times) grant the potential application in industry to the heterogeneous catalysts.

Full text of DOI:10.1016/j.jorganchem.2016.06.005

Journal of Organometallic Chemistry 819 (2016) 20e26
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Asymmetric epoxidation of unfunctionalized olefins catalyzed by
Jacobsen’s catalyst on alkoxyl-modified zirconium poly (styrene-
phenylvinylphosphonate)-phosphate (ZPS-PVPA)
,
b
,
c
,
,
, b
Jing Huang a
*, Yan Luo d **, Jiali Cai e, Xiaohong Chen a
a Research Center for Advanced Computation, Xihua University, Chengdu 610039, PR China
b College of Science, Xihua University, Chengdu 610039, PR China
c Institute for Clean Energy & Advanced Materials, Southwest University, Chongqing 400715, PR China
d College of Materials and Chemical Engineering, Chongqing University of Arts and Science, Chongqing 402160, PR China
e College of Rongchang, Southwest University, Chongqing, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
New chiral Jacobsen’s catalysts grafted onto alkoxyl-modified ZPS-PVPA are synthesized and applied in
asymmetric epoxidations of unfunctionalized olefins. Specially, the supported catalysts indicate excellent
catalytic activities (conv%, up to 96; sele%, up to 96; ee%, up to >99) in the absence of N-methyl-
morpholine N-oxide (NMO) by virtue of the special configurations of the catalysts. The superior stability
(recycling for ten times) and the comfortable dispositions in large-scale reactions (such as 200 times)
grant the potential application in industry to the heterogeneous catalysts.
Received 2 December 2015
Received in revised form
24 May 2016
Accepted 5 June 2016
Available online 11 June 2016
© 2016 Elsevier B.V. All rights reserved.
Keywords:
Asymmetric epoxidation
Unfunctionalized olefins
Jacobsen’s catalyst
Heterogeneous catalyst
Alkoxyl-modified
1. Introduction
High enantioselection has been achieved with homogeneous cat-
alysts, yet separation, recovery, and reuse remain arduous. A
Enantioselective reactions promoted by chiral catalysts are of
great importance in current chemical research [1,2]. Catalytic
asymmetric epoxidation is an important transformation in organic
synthesis since it can generate up to two stereogenic centres as well
as the reactive three membered epoxide ring [3e6]. Salen-type li-
gands are particularly attractive because they can be easily modi-
fied in terms of their structure [7,8]. The most widely utilized salen
based catalyst system is undoubtedly the manganese (III) complex
of the salen ligand known as Jacobsen’s epoxidation catalyst to
promote the asymmetric epoxidation of alkenes and led to excel-
lent results in terms of both activity and enantioselectivity [9e11].
number of approaches have been developed for the design of
immobilized homogeneous chiral catalysts or heterogeneous chiral
catalysts [12e18].
We have devoted ourselves to immobilizing Jacobsen’s catalyst
on
a
series of hybrid materials, such as zirconium
oligostyrenylphosphonate-phosphate (ZSPP) and zirconium poly
(styrene-phenylvinylphosphonate)-phosphate (ZPS-PVPA) and zinc
poly(styrene-phenylvinyl- phosphonate)-phosphate (ZnPS-PVPA)
as well as calcium poly(styrene-phenylvinylphosphonate)-phos-
phate (CaPS-PVPA). Moreover, the heterogeneous Jacobsen’s cata-
lysts indicate superior dispositions in asymmetric epoxidation of
unfunctionalized olefins [19e26].
In this design, we have attempted to synthesize alkoxyl-
modified chiral Jacobsen’s catalyst immobilized on ZPS-PVPA for
asymmetric epoxidations of unfunctionalized olefins. Apart from
this, we contemplate to investigate the catalytic activity system-
atically and to interpret the epoxidation reaction mechanism in m-
CPBA/NMO system.
* Corresponding author. Research Center for Advanced Computation, Xihua
University, Chengdu 610039, PR China; College of Science, Xihua University,
Chengdu 610039, PR China.
** Corresponding author.
E-mail address: hj41012@163.com (J. Huang).
http://dx.doi.org/10.1016/j.jorganchem.2016.06.005
0022-328X/© 2016 Elsevier B.V. All rights reserved.

J. Huang et al. / Journal of Organometallic Chemistry 819 (2016) 20e26
21
2. Experiment
n ¼ 8.2, Mw/Mn ¼ 2.
2.1. Materials and instruments
2.2.2. Synthesis of zirconium
poly(styrenephenylvinylphosphonate)-phosphate (ZPS-PVPA, 1)
All chemicals and reagents in this work were analytical grade
and used as received. All the solvents were further purified before
use. Chiral salen ligand and chiral homogeneous catalyst salen
Mn(III) were synthesized according to the standard literature pro-
cedures [27], and further identified by analysis and comparison of
IR spectra with literature [28].
PS-PVPA (5.18 g, 8 mmol), zirconyl chloride (13.47 g, 24.3 mmol)
and sodium orthophosphate (23.52 g, 16 mmol) were used to
synthesize ZPS-PVPA (22.11 g in 90% yield) according to the liter-
ature [21]. IR (KBr): 3060, 3026, 2925 (CH), 1632, 1494, 1453, 757,
699(-C6H5), 1029 (P¼O) cmꢁ1. Found: C, 64.58; H, 5.46. Calc. for
C147H151O22P6Zr3: C, 64.72; H, 5.54%.
FT-IR spectra were recorded from KBr pellets using a Bruker
RFS100/S spectrophotometer (USA) and diffuse reflectance UVevis
spectra of the solid samples were recorded in the spectrophotom-
eter with an integrating sphere using BaSO4 as standard. 1H NMR
and 31P NMR were performed on AV-300 NMR instrument at
ambient temperature at 300 and 121 MHz, respectively. All of the
chemical shifts were reported downfield in ppm relative to the
hydrogen and phosphorus resonance of TMS and 85% H3PO4,
respectively. Number- and weight-average molecular weights (Mn
and Mw) and polydispersity (Mw/Mn) were estimated by Wa-
ters1515 gel permeation chromatograph (GPC; against polystyrene
standards) using THF as an eluent (1.0 mL min-1) at 35 ꢀC. X-ray
photoelectron spectrum was recorded on ESCALab250 instrument.
The interlayer spacings were obtained on DX-1000 automated X-
2.2.3. Synthesis of chloromethyl-zirconium
poly(styrenephenylvinylphosphonate)-phosphate (ZCMPS-PVPA, 2)
Chloromethyl methyl ether (9.3 mL), anhydrous zinc chloride
(1.92 g, 14.18 mmol) and ZPS-PVPA (6.0 g, 8.55 mmol) were mixed
and stirred at 45 ꢀC for 8 h. Then the mixture was filtered, washed
and dried in vacuo to obtain 2 (ZCMPS-PVPA) (7.43 g in 90.3% yield).
The strong absorption peak of 716 cmꢁ1 in IR spectrum is ascribed
to the stretching vibration of C-Cl bond. IR (KBr): 3026, 2925 (CH),
2337 (O¼P-OH), 1605, 1545, 1512, 1495 (-C6H5), 1271 (P¼O), 716 (C-
Cl) cmꢁ1. Found: C, 59.02; H, 4.99%. Calc. for C156H160O22P6 Cl9Zr3: C,
59.10; H, 5.05%.
ray power diffractometer, using Cu Ka radiation and internal silicon
2.2.4. Synthesis of alkomethyl-zirconium
powder standard with all samples. The patterns were generally
measured between 3.00ꢀ and 80.00ꢀ with a step size of 0.02ꢀ minꢁ1
and X-ray tube settings of 36 kV and 20 mA. C, H and N elemental
analysis was obtained from an EATM 1112 automatic elemental
analyzer instrument (Thermo, USA). TG analyses were performed
on a SBTQ600 thermal analyzer (USA) with the heating rate of
20 ꢀC minꢁ1 from 25 to 1000 ꢀC under flowing N2 (100 mL minꢁ1).
Mn contents of the catalysts were determined by a TAS-986G
(Pgeneral, China) atomic absorption spectroscopy. SEM were per-
formed on KYKY-EM 3200 (KYKY, China) micrograph. TEM were
obtained on a TECNAI10 (PHILIPS, Holland) apparatus. Nitrogen
adsorption isotherms were measured at 77 K on a 3H-2000I (Hui-
haihong, China) volumetric adsorption analyzer with BET method.
The racemic epoxides were prepared by epoxidation of the corre-
sponding olefins by 3-chloroperbenzoic acid in CH2Cl2 and
confirmed by NMR (Bruker AV-300), and the gas chromatography
(GC) was calibrated with the samples of n-nonane, olefins and
corresponding racemic epoxides. The conversions (with n-nonane
as internal standard) and the ee values were analyzed by gas
chromatography (GC) with a Shimadzu GC2010 (Japan) instrument
poly(styrenephenylvinylphosphonate)-phosphate (ZAMPS-PVPA, 3)
Proportional amount of ethylene glycol was blended with
ZCMPS-PVPA (1 g), Na2CO3 (1.06 g, 0.01 mol), and THF 50 mL (the
mol ratio of dihydric alcohol to chlorine element in ZCMPS-PVPA
was 10:1), and the mixture was stirred and kept at 70 ꢀC for 24 h.
After the reaction, the solvent was vaporized under decompression.
Subsequently, the product 3a was filtered and washed with
deionized water and dried in vacuo. The products 3b-f were pre-
pared according to the similar course. Reaction yields varied from
65% to 82%. 3a, Found: C, 61.23; H, 5.96%. Calc. for C175H206O40P6Zr3:
C, 61.51; H, 6.05%. 3b, Found: C, 63.04; H, 6.48%. Calc. for
C193H243O40P6Zr3: C, 63.21; H, 6.63%. 3c, Found: C, 64.25; H, 7.02%.
Calc. for C212H280O40P6Zr3: C, 64.69; H, 7.13%. 3d, Found: C, 58.36; H,
6.15%. Calc. for C193H252O50P6Zr3: C, 56.18; H, 6.32%. 3e, Found: C,
61.23; H, 5.96%. Calc. for C212H289O59P6Zr3: C, 56.25; H, 6.41%. 3f,
Found: C, 54.29; H, 6.32%. Calc. for C230H326O68P6Zr3: C, 54.48; H,
6.43%.
2.2.5. Synthesis grafting chiral salen Mn(III) catalyst onto ZAMPS-
PVPA (4)
equipped
using
a
chiral
column
(HP19091G-B213,
30 m ꢂ 30 m ꢂ 0.32 mm ꢂ 0.25
m
m) and FID detector, injector
Chiral salen Mn(III) (2.5 g, 3.94 mmol) in 10 mL of THF was
added dropwise to the solution of 3a (0.5 g) pre-swelled in THF for
30 min and Na (0.1 g, 4.35 mmol) with stirring. Then the mixture
was refluxed for 24 h. After cooling down, the solution was
neutralized and the solvent was evaporated. The dark brown
powder 4a was obtained by filtration and washed thoroughly with
CH2Cl2 and deionized water respectively until no Mn could be
detected by AAS. 4b-g were obtained according to the same pro-
cess. Mn contents of 4a-g were 0.48, 0.52, 0.60, 0.56, 0.67,
0.72 mmol/g, respectively. 4a, Found: C, 67.95; H, 7.46; N, 2.76%.
Calc. for C506H676N18O59P6 Zr3Mn9: C, 68.14; H, 7.58; N, 2.89%. 4b,
230 ꢀC, detector 230 ꢀC. Ultrapure nitrogen was used as the carrier
(rate 34 mL/min) with carrier pressure 39.1 kPa and the injection
pore temperature was set at 230 ꢀC.
2.2. Synthesis of the catalysts (Scheme 1)
2.2.1. Synthesis of styrene-phenylvinylphosphonic acid copolymer
(PS-PVPA)
1-Phenylvinyl phosphonic acid (PVPA) was synthesized ac-
cording to the literature [29] and its structures were confirmed by
1H NMR, 31P NMR and FT-IR. 1H NMR (CDCl3): 6.06 (d, 1H), 6.23 (d,
1H), 7.26e7.33 (m, 3H), 7.48 (m, 2H). 31P NMR (CD3OD): 15.9. IR
(KBr): 2710, 2240, 1500, 1200, 1040, 950, 780, 720, 700 cmꢁ1. Yield:
90%.
Found: C, 68.51; H, 7.62; N, 2.73%. Calc. for
C524H712
N18O59P6Zr3Mn9: C, 68.63; H, 7.77; N, 2.81%. 4c, Found: C, 68.92; H,
7.86; N, 2.67%. Calc. for C543H749N18O59P6Zr3Mn9: C, 69.1; H, 7.95; N,
2.73%. 4d, Found: C, 66.25; H, 7.63; N, 2.63%. Calc. for
1-Phenylvinyl phosphonic acid (4 g, 21.7 mmol), styrene (20 mL,
173.9 mmol), ethyl acetate (150 mL) and benzoyl peroxide (BPO,
1.0 g, 4.7 mmol) were used for the preparation of PS-PVPA (7.52 g in
47% yield) as the literature [21]. GPC: Mn ¼ 39,729.43, m ¼ 38.3,
C524H731N18O68P6Zr3Mn9: C, 66.43; H, 7.71; N, 2.72%. 4e, Found: C,
64.68; H, 7.53; N, 2.48%. Calc. for C543H768N18O77P6Zr3Mn9: C,
64.97; H, 7.66; N, 2.57%. 4f, Found: C, 63.46; H, 7.52; N, 2.36%. Calc.
for C561H804N18O86P6Zr3Mn9: C, 63.67; H, 7.61; N, 2.44%.

22
J. Huang et al. / Journal of Organometallic Chemistry 819 (2016) 20e26
PO3H2
C
H2
C
H2
C
PO3H2
H
C
*
n
8H2O
ZrOCl2
NaH2PO4, THF
BPO
m
EtOAC
PVPA
St-PVPA
PO3
C
H2
C
H2
C
H
C
CH3OCH2Cl
ZnCl2
NaH, THF
RH2
Zr(HPO4)1.35
xH2O
*
*
CH2Cl
n
0.65/m
1
2
4a R = -O(CH2)2O-
4b R = -O(CH2)4O-
4c R = -O(CH2)6O-
4d R = -O(CH2CH2O)2-
4e R = -O(CH2CH2O)3-
4f R = -O(CH2CH2O)4-
N
O
N
O
Mn
THF Na
salen Mn(III)
t-Bu
t-Bu
RH
R
t-Bu
t-Bu
3
4
(
ZPS-PVPA )
=
Scheme 1. Synthesis of the heterogeneous catalysts.
Br
salen Mn(III)
RH
THF, Na
N
O
N
O
THF, Na
t-Bu
Mn
R
t-Bu
t-Bu
t-Bu
5
5a R = -O(CH2)2OCH3
5b R = -O(CH2CH2O)2CH3
6a R = -O(CH2)2OCH3
6b R = -O(CH2CH2O)2CH3
6
Scheme 2. Synthesis of homogeneous catalysts.
2.3. Synthesis of alkoxyl-modified chiral salen Mn(III) (Scheme 2)
next run. In every run the same proportion of the substrate-to-
catalyst and solvent-to-catalyst was retained.
4-methoxy-1-butanol (20 mmol), Na2CO3 (0.848 g, 8 mmol)
were blended with Benzyl bromide at 70 ꢀC for 6 h to gain the
compound 6a. Then, the subsequent procedure was similar to the
heterogeneous catalyst (in section 2.2.5). IR (KBr):Vmax/cmꢁ1 2840,
2930 (-CH3), 2339 (O¼P-OH), 1650, 1542, 1510, 1493 (-C6H5), 1630(-
C¼N), 1440(-CH-), 1262 (P¼O), 520 (-Mn-N-) cmꢁ1. 6a, Found: C,
72.16; H, 8.42; N, 6.85. Calc. for C46H65N2O4Mn: C, 72.25; H, 8.51; N,
3.67%. 6b, Found: C, 71.06; H, 8.51; N, 3.37%. Calc. for
3. Results and discussion
3.1. Characterizations of the heterogeneous chiral catalysts
3.1.1. IR spectroscopy and UVevis spectroscopy
All the heterogeneous catalysts 4a-f and Jacobsen’s catalyst have
indicated the same band at 1630 cmꢁ1 (Fig. S1) owing to the
azomethene(C¼N) stretching band. The common prominent bands
at 1145, 1089, and 986 cmꢁ1 are due to R-PO23- phosphonate
stretching vibrations. The band at 523 cmꢁ1 is attributed to the
stretching vibration of Mn-O. The stretching vibration at 1030 cmꢁ1
which is ascribed to characteristic vibrations of the phosphonate
and phosphate in ZPS-PVPA, is obviously weakened owing to the
electronic structure changes for the host-guest interaction.
The spectra of 4b and 4g have shown similar features to Jacob-
sen’s catalyst at 252, 430 and 500 nm (Fig. S2). According to the
supported catalysts, the bands at 320 nm and the bands at 430,
C
48H70N2O5Mn: C, 71.20; H, 8.65; N, 3.46%.
2.4. Asymmetric epoxidation
As for m-CPBA/NMO, the activities of the prepared catalysts
were tested with alkene (1 mmol), n-nonane (internal standard,
1 mmol), NMO (5 mmol), homogeneous (5 mol%) or heterogeneous
salen Mn(III) catalysts (5 mol%) and m-CPBA (2 mmol) for the
epoxidation of unfunctionalized olefins in CH2Cl2. After the reac-
tion, Na2CO3 (2 mL, 1.0 M) was added to quench the reaction.
2.5. The reusability of the catalyst
505 nm are ascribed to
p
-
p
* and DMSO-d6 transition of C¼N
respectively; and the bands at 253 nm are due to the transition of
benzene ring. While for Jacobsen’s catalyst, the corresponding
bands indicate red shifts to 335, 433, 510, 259 nm, due to the
interaction between the salen Mn(III) complex and the alkoxyl-
modified ZPS-PVPA.
In a typical recirculation, the equal volume of hexane was added
to the mixture after the reaction. Subsequently, the organic phase
was separated, and the catalyst was washed, and dried over vac-
uum at 60 ꢀC. The recovered catalyst was weighed and reused in the

J. Huang et al. / Journal of Organometallic Chemistry 819 (2016) 20e26
23
which is be incongruous with the most articles reported such as the
catalysts anchored onto ZSPP [19]. Based on this, it could be
deduced that Jacobsen’s catalysts are either immobilized on the
external surface of ZPS-PVPA or introduced into the channels and
holes.
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
100
90
80
70
60
50
40
30
22
6.916%
00
-2
-4
-6
-8
-1
54.43%
3.1.4. Analysis of surface morphology
According to ZPS-PVPA (Fig 3A), the structure is loose and
amorphous. While for the catalyst 4f, the morphology is trans-
formed tremendously, for instance the smooth anomalous struc-
ture resides in the catalyst 4f (Fig 3B) by virtue of the
immobilization of chiral salen Mn (III). Apart from this, many small
caves and channels with irregular shapes also exist. Amorphous
morphology and porous structure of the catalysts together could
facilitate the substrates approaching the catalytic active sites.
On account of TEM images in Fig 4, both the catalyst 4d (Fig 4A)
and 4f (Fig 4B) indicate loose configurations which contain the
channels, the holes and the cavums. The similar morphologies also
demonstrate that the dispositions of the linkers hardly contribute
to the morphology. On the other hand, the special configurations of
the catalysts could be beneficial to the substrates approaching the
internal catalytic active sites and supply further space for asym-
metric epoxidations of unfunctionalized olefins.
TG
DTG
DSC
6.818%
0
0
200
400
600
800
11000
Temperature(? )
Fig. 1. TG curve of the catalyst 4f.
3.1.2. Thermal gravimetric analysis
As described in Fig 1, the initial weight loss is 6.92% below
160 ꢀC, owing to surface-bound or intercalated water in this stage.
And then, the organic moieties decompose with 54.43% weight loss
in the temperature range of 160e700 ꢀC. At length, the small
weight losses in the scope of 700e1000 ꢀC are ascribed to the
dehydration changes from Zr(HPO4)2 to ZrP2O7. Obviously, the
catalyst 4f could still retain superior stability lower than 160 ꢀC,
which contributes to the potentiality in asymmetric epoxidations.
3.2. Catalytic epoxidation of unfunctionalized olefins
As for asymmetric epoxidation of indene (Table 2), ee values
increase from 65% to 85% or 90% (Jacobsen’s vs 6a vs 6b, entry 1 vs
10 vs 12) owing to the modification of alkoxy and further increase
even up to >99% (6a vs 3a, 85% vs 93%, entry 10 vs 2; 6b vs 4d, 90%
vs 95%, entry 12 vs 6) upon anchoring on ZPS-PVPA. The similar
trend also has been presented according to asymmetric epoxida-
3.1.3. Nitrogen adsorption-desorption isotherms
The nitrogen adsorption-desorption isotherms of the catalyst 4f
are characteristic type V (Fig. 2), accompanied with a distinct hys-
teresis loop (type H1). On account of the desorption isotherm (Fig
2), BJH analysis indicates a broad and non-uniform distribution of
pore size (in the range 2e20 nm), which demonstrates that the
catalyst is provided with the mesoporous structure. In addition, the
pore diameters of the particles are mainly varied from 1 nm to
20 nm, and a small quantity of the particles are below 1 nm as well
as the less is distributed over 50 nm in diameter.
The corresponding textural parameters calculated by N2
adsorption-desorption isotherms are presented in Table 1.
By means of the chloromethylation and the alkoxylation as well
as the immobilization, the corresponding textural parameters are
obvious decreased, such as in BET surface area (1 vs 2 vs 3f vs 4f,180
vs 120.3 vs 84.8 vs 66.0 m2/g), and in the pore volume (1 vs 2 vs 3f
vs 4f, 3.5 vs 2.7 vs 1. 9 vs 1.1 ꢂ 10ꢁ2 cm3/g) as well as in average pore
diameter (1 vs 2 vs 3f vs 4f, 46.8 vs 38.1 vs 30.8 vs 25.2 nm). The
occupations of caves and channels result in the phenomenon,
tion of a-methylstyrene. In other words, the synergistic effect of
ZPS-PVPA and the linker alkoxy as well as the chiral ligand
contribute to the superior activities. Apart from this, the catalysts
indicate superior catalytic disposition only after 1 h, compared with
the reported catalysts with MCM-41, ITQ-2 and IT-6 as the supports
which indicate merely 56% ee values even after for 70 h [30].
Shown in Table 2, ee values increase from 93% to 99% according
to indene (entry 2e4, 6e8) and vary from 56% to 82% for a-meth-
ylstyrene (entry 15e17, 19e21), which demonstrates that the cat-
alytic activities are increasing with the carbon number of linkage
[31,21]. In the same way, the phenomenon happens to asym-
metric epoxidation of styrene and 1-octene (entry 28e35, 37e44).
The phenomenon might be interpreted that the augmentation of
the linkage makes for the heterogeneous salen Mn(III) complexes
approaching the active intermediates of salen Mn(V) or their
transition states more easily.
Notably, ee values increase from 25% to 97% and conversions
from 43% to 96% (entry 5 vs 4) in asymmetric epoxidation of indene
without the addition of NMO. The similar results happen to the
epoxidation of a-methylstyrene (ee%, 15 vs 75; conv.%, 43 vs > 99;
entry 17 vs 18) and the alkoxyl-modified catalyst 6a (conv%, 85 vs
76; ee%, 95 vs 24; entry 10 vs 11). Based on the results reported
[32,33], it could be deduced that the special phenomenon has no
concern with the support ZPS-PVPA. The coordination complexes
such as Mn(salen)OPh and Mn(salen)OP as well as alkoxy-Mn
(salen) could afford superior properties in the absence of NMO,
which is not fit for N-Mn (salen) complexes. The following three
factors may contribute to this particular phenomenon in this
context. Firstly, when hexamethylene diamine and NMO approach
Mn center simultaneously, the spatial repellant and the formative
Mn-O ionic bond may put effect on the bond length of Mn(V)¼O
and further induce the axial ligand NMO deviating from the plane
of salicylaldehyde. As a result, the stability of reactive intermediate
Fig. 2. The nitrogen adsorption-desorption isotherm and pore distribution of the
catalyst 4f.

24
J. Huang et al. / Journal of Organometallic Chemistry 819 (2016) 20e26
Table 1
The physical properties of 1, 2, 3f and 4f.
Sample
Surface area (m2/g)
Pore volume (ꢂ10ꢁ1 cm3/g)
Average pore size (nm)
1
2
3f
4f
180
3.5
2.7
1.9
1.1
46.8
38.1
30.8
25.2
120.3
84.8
66.0
Fig. 3. SEM photograph of (A) ZPS-PVPA and (B) the catalyst 4f.
Fig. 4. TEM photograph of (A) the catalyst 4d; (B) the catalyst 4f.
or transition state may step down, accompanying with the lower ee
value [34]. Secondly, the alkoxy linker groups as the axial coordi-
nating group for the supported catalysts 4a-f have similar proper-
ties with O-coordinating axial base NMO in electronic structure and
coordination performance. When N-oxide ligand (NMO) is added to
the catalytic system, the well-defined molecular geometry and the
conformation of the immobilized chiral salen Mn (III) catalysts may
be interfered with. Accordingly, the optimal geometric configura-
tion of the reactive intermediate salen Mn(V)¼O would be altered
and further lead to the decrease of the conversion and chirality
recognization. Thirdly, a balance transformation (Fig. 5) between
Mn (V)¼O and Mn (Ⅲ) coordination complex lies in asymmetric
epoxidation of unfunctionalized olefins [35]. Meanwhile, NMO
binds to unsaturated Mn (Ⅲ) coordination compound by means of
coordination bond. When NMO is added, this type of coordination
would be destroyed owing to Mn (Ⅲ) bonded to alkoxyl-modified
ZPS-PVPA, accompanying with the increase of the concentration
of Mn (Ⅲ) and the decrease of Mn (V)¼O. The lower ee values
would be obtained spontaneously.
3.3. The reusability of the catalysts
As described in Fig 6, the catalytic disposition merely decreases
slightly for the first seven runs (conv.%: from 96 to 88; ee%: from
>99 to 98) and is still superior to that of the homogeneous coun-
terpart even after recycling for twelve (ee%: 82 vs 65; 4f vs Jacob-
sen’s). The high stability may be partly attributed to the special
configuration of ZPS-PVPA which combines dual properties of hy-
drophobic polystyrene parts and hydrophilic zirconium phospho-
nate parts. Moreover, the initial configuration such as layered
structure and the channels as well as the caves could be approxi-
mately revived upon self-assembly in aqueous phase, which make
for the predominant virtue of reusability.
4. Conclusion
In general, chiral Jacobsen’s catalysts anchored on alkoxyl-
modified zirconium poly (styrene-phenylvinylphosphonate)-
phosphate (ZPS-PVPA) have been synthesized and employed in
asymmetric epoxidation of olefins. The heterogeneous catalysts

J. Huang et al. / Journal of Organometallic Chemistry 819 (2016) 20e26
25
Table 2
Asymmetric epoxidation of alkenes catalyzed by catalysts 4a-f and 6a-b.a
Entry
Substrateb
Catalyst
Oxidant
Conv.(%)c
sele.(%)d
ee.(%)
TOFg ꢂ 10ꢁ3 (sꢁ1
)
1
2
3
4
5
6
7
8
A
A
A
A
A
A
A
A
A
A
A
A
A
Jacobsen’s
m-CPBA/NMO
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
m-CPBA
m-CPBA/NMO
m-CPBA
>99
93
95
96
43
94
93
96
46
95
24
84
52
>99
94
93
96
99
93
95
96
>99
73
90
26
97
65e
93e
96e
97e
25e
95e
98e
>99e
33e
85e
76e
90e
70e
5.50
5.17
5.27
5.33
2.39
5.22
5.17
5.33
2.56
5.27
1.33
4.67
2.89
4a
4b
4c
4c
4d
4e
4f
9
4f
10
11
12
13
6a
6a
6b
6b
m-CPBA/NMO
14
15
16
17
18
19
20
21
22
23
24
25
26
B
B
B
B
B
B
B
B
B
B
B
B
B
Jacobsen’s
m-CPBA/NMO
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
m-CPBA
m-CPBA/NMO
m-CPBA
>99
>99
>99
>99
43
>99
>99
>99
51
89
37
98
44
99
63
61
63
60
56
61
62
52
22
31
25
58
52f
56f
67f
75f
15f
66f
78f
82f
28f
91f
25f
96f
37f
5.50
5.50
5.50
5.50
2.39
5.50
5.50
5.50
2.83
4.94
2.05
5.44
2.43
4a
4b
4c
4c
4d
4e
4f
4f
6a
6a
6b
6b
m-CPBA/NMO
27
28
29
30
31
32
33
34
35
C
C
C
C
C
C
C
C
C
Jacobsen’s
m-CPBA/NMO
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
98
82
87
91
96
83
85
90
95
96
81
86
90
97
84
86
91
96
47
56
64
72
5.6
58
65
68
4.8
5.44
4.55
4.83
5.05
5.33
4.61
4.72
5.00
5.27
4a
4b
4c
4c
4d
4e
4f
4f
36
37
38
39
40
41
42
43
44
D
D
D
D
D
D
D
D
D
Jacobsen’s
m-CPBA/NMO
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
90
86
92
98
>99
84
89
96
>99
86
85
89
97
>99
85
87
95
>99
40
65
72
81
6.2
63
69
79
5.4
5.00
4.77
5.11
5.44
5.55
4.66
4.94
5.33
5.55
4a
4b
4c
4c
4d
4e
4f
4f
a
Reactions were carried out at 0 ꢀC in CH2Cl2 (3.0 mL) with alkene (0.5 mmol), m-CPBA (1.0 mmol), NMO (340.0 mg, 2.50 mmol), nonane (internal standard, 90.0
mL,
0.5 mmol) and salen Mn(III) catalysts (0.0250 mmol, 5.0 mol%).
b
A ¼ indene, B ¼ -methylstyrene, C ¼ styrene, D ¼ 1-octene.
a
c
d
e
f
Conversions were determined by GC with a chiral capillary column (HP19091G-B233, 30 m ꢂ 0.32 mm ꢂ 0.25
mm).
Selectivities were determined by GC, by integration of product peaks against an internal quantitative standard (nonane), correcting for response factors.
Epoxide configuration 1S, 2R.
Epoxide configuration S.
g
Turnover frequency (TOF) is calculated by the expression of [product]/[catalyst] ꢂ time (sꢁ1).
OL
O
O
IV
L
IV
V
Mn
MnIII
Cl
III
Mn
Mn Cl
Cl Mn
Ο
+
MnV
+
Cl
Cl
Cl
Fig. 5. The scheme of concentration equilibria.
could effectively participate in the reaction, owing to congenerous
effect of ZPS-PVPA and the linker alkoxy as well as the chiral ligand.
Moreover, the supported catalysts could still keep their activities
even after recycling for ten times. Notably, the heterogeneous
catalysts could indicate distinguished increases of activities for
asymmetric epoxidation of olefins without the addition of
expensive NMO, which paves the way for the potential applications
in industry.
Acknowledgement
This work is financially supported by the Fundamental Research

26
J. Huang et al. / Journal of Organometallic Chemistry 819 (2016) 20e26
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