Thermoregulated phase-transfer ligands and catalysis. Part VI. Two-phase hydroformylation of styrene catalyzed by the thermoregulated phase-transfer catalyst OPGPP/Rh

Article abstract of DOI:10.1016/S0022-328X(98)00887-0

A novel nonionic water-soluble octylpolyglycol-phenylene-phosphite (OPGPP) was synthesized and the two-phase hydroformylation of styrene catalyzed by an OPGPP/Rh catalyst was investigated fully. The catalyst displayed excellent catalytic activity; high styrene conversion and high aldehyde yield (99.6 and 99.3%, respectively) were obtained at 80°C and 5.0 MPa, and the molar ratio of branched/normal aldehyde was 4.8. The experimental results revealed that there was a 'thermoregulated phase-transfer catalysis (TRPTC)' process present in the reactions.

Full text of DOI:10.1016/S0022-328X(98)00887-0

Journal of Organometallic Chemistry 571 (1998) 201–204
Thermoregulated phase-transfer ligands and catalysis. Part VI.
Two-phase hydroformylation of styrene catalyzed by the
thermoregulated phase-transfer catalyst OPGPP/Rh
Ruifang Chen, Xiaozhong Liu, Zilin Jin *
State Key Laboratory of Fine Chemicals, Dalian Uni6ersity of Technology, Dalian 116012, People’s Republic of China
Received 28 April 1998; received in revised form 27 July 1998
Abstract
A novel nonionic water-soluble octylpolyglycol-phenylene-phosphite (OPGPP) was synthesized and the two-phase hydroformy-
lation of styrene catalyzed by an OPGPP/Rh catalyst was investigated fully. The catalyst displayed excellent catalytic activity; high
styrene conversion and high aldehyde yield (99.6 and 99.3%, respectively) were obtained at 80°C and 5.0 MPa, and the molar ratio
of branched/normal aldehyde was 4.8. The experimental results revealed that there was a ‘thermoregulated phase-transfer catalysis
(TRPTC)’ process present in the reactions. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Water-soluble phosphine; Two-phase hydroformylation; Styrene; TRPTC
1. Introduction
It is well known that 2-arylpropionaldehyde is an
important starting material for cosmetics, polymers and
Comparing the anion water-soluble ligand TPPTS
pharmaceuticals [1]. A great deal of research interest
(trisodium salt of trisulfonated triphenylphosphine) and
has been focused on the homogenous hydroformylation
TPPMS
(sodium
salt
of
mono-sulfonated
of styrene catalyzed by Rh carbonyl complexes using
various phosphine ligands [2–6], whilst water-soluble
catalysts in a biphasic system has received little atten-
tion so far [7–9]. In a previous report [10], we reported
the synthesis of a series of water-soluble polyether-sub-
stituted triphenylphosphines (PETPPs) which exhibit
thermoregulated phase-transfer function, and success-
fully applied them to the biphasic hydroformylation of
higher olefins [11].
In this paper, two-phase hydroformylation of styrene
catalyzed by a new rhodium catalyst with octylpolygly-
col-phenylene-phosphite (OPGPP) as the ligand is
studied.
triphenylphosphine), the polyoxyethylene-modified
nonionic water-soluble phosphine OPGPP has a critical
solution temperature—‘cloud point (Tp)’—and mani-
fests a special property of inverse temperature-depen-
dent water-solubility similar to that of the nonionic
surfactants. As a result, the OPGPP/Rh catalyst is
soluble in the aqueous phase at lower temperatures and
it can transfer into the organic phase to catalyze the
hydroformylation reaction at temperatures higher than
Tp and return to the aqueous phase to be separated
from the production at temperatures lower than Tp.
The OPGPP/Rh catalyst also exhibits desirable cata-
lytic reactivity in the two-phase (water/organic) hydro-
formylation of styrene, with the conversion up to 99.6%
and the yield of aldehyde 99.3%.
* Corresponding author. Fax: +86 411 3633080.
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00887-0

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R. Chen et al. / Journal of Organometallic Chemistry 571 (1998) 201–204
2. Experimental
a stirred solution of polyether-substituted 1-octanol (14
g, 0.02 mol) in 10 ml toluene. After the addition, the
mixture was stirred at refluxing for 4 h. Toluene was
drawn out under vacuum. The crude product OPGPP
14.9 g (85%) was dissolved in 20 ml diethylether to
All solvents and styrene are distilled prior to use.
Distilled deionized water was used and the
Rh(acac)(CO)2 was purchased from the Beijing Re-
search Institute of Chemical Industry.
1
further purification. H-NMR/CDCl3: l(ppm) 0.9(3H,
CH3), 1.3(12H, CH2), 3.5(52H, C2H4O,), 4.4(2H,
OCH2), 6.8–8.1(4H, Ph). FT-IR (cm−1): w(C–O–C)
1116, w(P–O–C(alkyl)) 1035, w(P–O–C(aromatic))
975.
2.1. Hydroformylation experiments
Hydroformylation of styrene was carried out in a
stainless steel autoclave of 75 ml capacity, which was
placed in an oil bath containing
a
thermostat.
2.5. Preparation of OPGPP/Rh(acac)(CO)2
Rh(acac)(CO)2, OPGPP, water, organic solvent, styrene
and the internal standard decane were placed in the
autoclave and were flushed four times with 2.0 MPa of
CO. The reactor was pressurized with synthesis gas
(CO/H2=1/1) up to the reaction pressure and held at
the designated temperature with magnetic stirring for a
fixed time. After cooling, the reactor was discharged
and the reaction solution was siphoned into a separa-
tory funnel. After phase separation, the organic layer
was washed with distilled water and dried over anhy-
drous magnesium sulfate and subjected to GC analysis.
The catalyst was generated in situ with
Rh(acac)(CO)2 as a catalyst precursor and OPGPP as a
ligand.
3. Results and discussion
3.1. Styrene hydroformylation
The hydroformylation of styrene was carried out
using Rh/OPGPP as a catalyst. The influences of ligand
OPGPP to rhodium molar ratio, temperature, total
pressure and organic solvents were assessed concerning
this reaction.
2.2. Preparation of polyether-substituted 1-octanol
[C8H17(OCH2CH2)13OH]
Ethoxylation was carried out in a 100 ml glass auto-
clave equipped with an apparatus for continuous
ethoxylation. 1-Octanol (7 g, 0.054 mol) together with a
catalytic amount of anhydrous sodium acetate (0.056 g,
0.8%) was charged in the autoclave. The system was
purged with nitrogen and heated to 130°C. Then the
desired amount of ethylene oxide (EO) was added to
maintain a pressure of 0.4 MPa (EO/N2=3/1) for the
required period of time. After ethoxylation was com-
plete, C8H17(OCH2CH2)nOH was obtained, and could
be used without further purification. The average length
The effect of OPGPP/Rh molar ratio on the styrene
conversion and the yield of aldehyde are shown in
Table 1. The conversion and yield of aldehyde increase
remarkably when OPGPP/Rh ratio varies from 2 to 13.
At P/Rh=13, the styrene conversion reaches 99.6%,
the yield of aldehyde is 99.3%. If P/Rh ratio is above
13, the yield of aldehyde does not change greatly.
Therefore, the ratio of 13 seems to be an optimum
result at these hydroformylation conditions. In addi-
tion, the branched/normal (i.e. b/n) ratio of aldehyde
slightly decreases with an increase in the P/Rh ratio.
The influence of reaction temperature has been inves-
tigated (Table 2). Under the experimental conditions,
the conversion of styrene and the yield of aldehyde
increase with temperature. In addition, the b/n ratio
1
of polyether chain (n=13) was determine by H-NMR
spectroscopy.
2.3. Preparation of o-phenylene chlorophosphite
(o-C6H4O2PCl)
Table 1
A total of 65 ml (0.75 mol) of PCl3 was added to a
250-ml, round-bottom flask which contained 55 g (0.5
mol) catechol over a 30 min period. After the addition,
the mixture was stirred at refluxing for 2 h. Distillation
of the reaction mixture afforded 74.2 g (85%) of o-
phenylene chlorophosphite, b.p. 98°C/25 mmHg.
Effect of P/Rh mol ratio on the two-phase hydroformylation of
styrene
P/Rh
Conversion (%)
Yield of aldehyde (%)
b/na
2
8
13
20
52.1
91.3
99.6
99.8
51.4
88.9
99.3
98.9
5.6
4.9
4.8
4.7
2.4. Preparation of octylpolyglycol-phenylene-phosphite
(OPGPP)
Reaction conditions: T=80°C, P=5.0 MPa (CO/H2=1), styrene 1
ml, styrene/Rh=1000 (molar ratio), H2O 2 ml, organic solvent
n-heptane 2 ml, reaction time t=6 h.
A solution of o-phenylene chlorophosphite (7 g, 0.04
mol) in 5 ml toluene was added over a 30 min period to
a b/n, branched/normal aldehyde ratio.

R. Chen et al. / Journal of Organometallic Chemistry 571 (1998) 201–204
203
Table 2
Table 4
Effect of reaction temperature on the two-phase hydroformylation of
styrene
Effect of organic solvent on the two-phase hydroformylation of
styrene
T (°C)
Conversion (%)
Yield of aldehyde (%)
b/n
Organic solvent Conversion (%)
Yield of aldehyde (%) b/n
40
60
80
22.5
78.4
99.6
99.8
22.0
77.6
99.3
98.4
14.6
7.7
4.8
1.6
Toluene
99.8
99.4
99.6
98.9
99.7
99.1
99.3
98.4
4.9
4.7
4.8
4.6
n-hexane
n-heptane
Cyclohexane
100
P/Rh=13; all other conditions are the same as in Table 1.
P/Rh=13; all other conditions are the same as in Table 1.
depends largely on temperature, decreasing sharply as
temperature increased. The optimum temperature for
the reaction is 80°C.
3.2. In6estigation of thermoregulated phase-transfer
function of OPGPP/Rh
The data in Table 3 indicates that the rate of hydro-
formylation increases with the total pressure (CO/H2=
1/1) whilst the aldehyde b/n ratio remains constant.
Only minor changes in the styrene conversion and the
aldehyde yield are observed above 5.0MPa. Therefore,
a pressure of 5.0 MPa is chosen for this hydroformyla-
tion reaction.
Table 4 shows the results of hydroformylation with
various organic solvents. Little effect on the catalytic
results is observed with different non-polar solvents.
However, after hydroformylation the color of organic
layer, which indicates the loss of Rh, had changed.
Using toluene as solvent, the organic layer after reac-
tion was yellow ash; whilst it was almost colorless if
n-heptane used as solvent, thus n-heptane is chosen in
order to reduce the Rh loss.
Four water-soluble catalysts for the two-phase hy-
droformylation of styrene are tested in Table 5. Poor
catalytic activity was obtained when the anion water
soluble phosphine ligand TPPTS was used and TPPMS
exhibits better activity because it is more soluble in the
organic phase than TPPTS. The noninic water-soluble
phosphine ligands polyether-substituted triphenylphos-
phine PETPPs (Ph2P[p-C6H4 (OCH2CH2)25OH]) and
OPGPP gave the best results. This attributed to the
thermoregulated phase-transfer function, i.e. the
OPGPP/Rh catalyst would transfer into organic phase
above its Tp temperature and, therefore, the hydro-
formylation of styrene occurs in the organic phase.
OPGPP has a distinct cloud point (Tp=56.5°C)
which indicated that it possessed a property termed as
‘inverse temperature-dependent water-solubility’. In or-
der to further investigate the thermoregulated phase-
transfer function of OPGPP/Rh catalyst, atmospheric
pressure hydrogenation experiments of allyl alcohol
with OPGPP/Rh were carried out in an aqueous
medium. As outlined in Fig. 1, an unusual inversely
temperature-dependent catalytic behavior was ob-
served. At 30°C, which is BTp, the hydrogenation
reaction proceeds (A region), since the uptake of hydro-
gen appeared; on heating of the sample to 70°C (T\
Tp), the reaction ceases (B region). Such an
anti-Arrhenius kinetic behavior could only be at-
tributed to the loss of catalytic activity of the Rh/
OPGPP catalyst when it precipitates from the aqueous
phase at the reaction temperature above its Tp. More-
over, the reactivity of the catalyst could be restored
since the phase separation process is reversible on cool-
ing to 30°C (C region) lower than the Tp. Obviously,
the existence of such an anti-Arrhenius phenomenon
provides fundamental support for the TRPTC of the
OPGPP/Rh catalyst.
In addition, the effects of Vwater/Vstyrene ratio on the
two-phase hydroformylation of styrene have been in-
vestigated (Table 6). Table 6 shows that the Vwater
/
Vstyrene ratio has no effect on the styrene conversion and
the yield of aldehyde. Conversely, the results would be
varied with the Vwater/Vstyrene ratio if TPPTS/Rh or
Table 5
Catalytic reactivity of different water-soluble catalysts in the two-
phase hydroformylation of styrene
Table 3
Effect of total pressure on the two-phase hydroformylation of styrene
Ligand
Conversion (%)
Yield of aldehyde(%)
b/n
P (MPa)
Conversion (%)
Yield of Aldehyde (%)
b/n
TPPTS
TPPMS
PETPPs
OPGPP
37.8
87
95.7
99.2
36.9
83
92.8
99.0
2.8
1.5
2.2
4.9
3.0
4.0
5.0
6.0
50.3
82.1
99.6
99.9
48.7
80.3
99.3
99.5
3.1
4.6
4.8
5.2
Reaction conditions: Rh(acac)(CO)2 0.01 mmol, P/Rh=12, styrene/
Rh=1000 (molar ratio), heptane 2.0 ml, H2O 3 ml, P=5.0 MPa
(CO/H2=1/1), T=80°C, t=5 h.
P/Rh=13; all other conditions are the same as in Table 1.

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R. Chen et al. / Journal of Organometallic Chemistry 571 (1998) 201–204
Table 6
Effect of Vwater/Vstyrene (v/v) ratio on the two-phase hydroformylation
of styrene catalyzed by OPGPP/Rh
Vwater
/
Conversion (%)
Yield of aldehyde (%)
b/n
Vstyrene
0
1
2
4
99.4
99.2
99.6
99.4
99.2
99.0
99.3
99.2
4.8
4.8
4.8
4.8
P/Rh=13; all other conditions are the same as in Table 1.
Fig. 1. Atmospheric-pressure hydrogenation of allyl alcohol using
OPGPP/Rh as the catalyst in water at different temperatures. Reac-
tion conditions: OPGPP 0.5 mmol, RhCl3 ·H2O 10.5 mg (0.04 mmol),
ally alcohol 0.58 g (10 mmol), H2O 25 ml.
ence Foundation of China (29792014) and Foundation
of SINOPEC and the International Cooperation Foun-
dation of Liaoning Province is gratefully acknowl-
edged.
TPPMS/Rh is employed as a catalyst under the same
conditions [12]. The usually two-phase (aqueous/or-
ganic) hydroformylation occurs in the aqueous phase or
at the aqueous/organic interface [13,14], and thus the
References
Vwater/Vstyrene ratio has obvious effects on the reaction
results; whilst the biphasic hydroformylation catalyzed
by OPGPP/Rh occurs in the organic phase when T\
Tp, so the Vwater/Vstyrene ratio has no influence on the
reaction results. This experimental result provides an
additional proof for the TRPTC process in the two-
phase hydroformylation of styrene catalyzed by
OPGPP/Rh catalyst.
[1] H. Siegel, W. Himmele, Angew. Chem. Int. Ed, Engl. 19 (1980)
178.
[2] B. El Ali, G. Vasapollo, H. Alper, J. Mol. Catal. A Chem. 112
(1996) 195.
[3] C. Basoli, C. Botteghi, M.A. Cabras, G. Chelucci, M. Marchetti,
J. Organomet. Chem. 488 (1995) C20.
[4] C. Abu-Gnim, I. Amer, J. Chem. Soc. Chem. Commun. 116
(1994) 115.
[5] T.J. Kwok, D.J. Wink, Organometallics 12 (1993) 1954.
[6] D.J. Wink, T.J. Kwok, US Pat. 5,179,055 (1993), and references
therein.
[7] P. Klack, F. Serein, New. J. Chem. 13 (1989) 515.
[8] T. Bartik, H. Ding, B. Bartik, B.E. Hanson, J. Mol. Catal. A.
Chem. 116 (1997) 54.
[9] J. Chen, H. Alper, J. Am. Chem. Soc. 119 (1997) 893.
[10] Z.L. Jin, X.L. Zheng, J. Mol. Catal. 116 (1997) 54.
[11] Z.L. Jin, X.L. Zheng, in: B. Cornils, W.A. Herrmann (Eds.),
Aqueous Phase Organometallic Catalysis—Concepts and Appli-
cations, Wiley-VCH, Weinheim, 1998, pp. 233–240.
[12] Y.Y. Yan, J.Y. Jiang, Z.L. Jin, Petrochem. Technol. (Chin.) 25
(1996) 89.
4. Conclusion
The water-soluble catalyst formed in situ from
OPGPP and Rh(acac)(CO)2 exhibits a thermoregulated
phase-transfer function, and a catalytic process named
TRPTC in the two-phase hydroformylation of styrene
is observed.
Acknowledgements
[13] A.F. Borowski, D.J. Cole-Hamilton, G. Wilkinson, Nouv. J.
Chem. 2 (1978) 137.
The financial support of the National Natural Sci-
[14] I.T. Horvath, Catal. Lett. 6 (1990) 43.
.