Selectivity in sulfonation of triphenyl phosphine

Article abstract of DOI:10.1021/op0000226

The selectivity of triphenyl phosphine sulfonation using 34% SO₃ to triphenyl phosphine trisulfonate (TPPTS) was studied. Several side products such as mono-and disulfonate, sulfonated phosphine oxide, and sulfonated phosphine Sulfides were also observed. Reaction conditions were optimised to give 90% pure TPPTS. Agitation speed, mode of agitation and temperature have a strong influence on activity and selectivity of reaction. The TPPTS formed was tested for its activity in hydroformylation of ethylene and octene-1 in biphasic mode using [Rh-(COD)Cl]₂.

Full text of DOI:10.1021/op0000226

Organic Process Research & Development 2000, 4, 342−345
Technical Notes
Selectivity in Sulfonation of Triphenyl Phosphine
B. M. Bhanage, S. S. Divekar, R. M. Deshpande,* and R. V. Chaudhari
Homogeneous Catalysis DiVision, National Chemical Laboratory, Pune 411 008, India
Abstract:
such as triphenylphosphine monosulfonate (TPPMS), tri-
The selectivity of triphenyl phosphine sulfonation using 34%
SO to triphenyl phosphine trisulfonate (TPPTS) was studied.
3
phenyl phosphine disulfonate (TPPDS), triphenylphosphine
trisulfonate oxide (OTPPTS), and triphenylphosphine trisul-
fonate sulfide (STPPTS) in reasonable quantities (see Figure
1). Further, isolation of pure TPPTS is tedious. Herrmann
et al. have proposed sulfonation of triphenyl phosphine in
Several side products such as mono- and disulfonate, sulfonated
phosphine oxide, and sulfonated phosphine sulfides were also
observed. Reaction conditions were optimised to give 90% pure
TPPTS. Agitation speed, mode of agitation and temperature
have a strong influence on activity and selectivity of reaction.
The TPPTS formed was tested for its activity in hydroformy-
lation of ethylene and octene-1 in biphasic mode using [Rh-
1
5
3 2 4 3 3
superacid medium using SO /H SO /H BO . This method
reduces the formation of OTPPTS considerably. However,
selectivity towards TPPTS is very poor. The intermediate
TPPDS is formed selectively even under conditions of high
temperature (120 °C) and longer reaction times (72 h).
TPPTS is formed on further sulfonation of TPPDS, with
oleum.
2
(COD)Cl] .
There is thus a definite scope for improvement in the
existing procedure for the synthesis of TPPTS by sulfonation.
It is also essential to obtain TPPTS in an acceptable yield
and purity. The reaction conditions for the synthesis,
particularly the reaction period, temperature, and the ratio
of triphenyl phosphine to oleum are extremely important.
In this study we have investigated the role of mixing,
temperature, and reaction time on activity and selectivity to
TPPTS. The optimum conditions have been arrived at to
obtain TPPTS of suitable purity and high yield.
Introduction
Biphasic catalysis using metal complex catalysts involving
water soluble ligands is considered a major advancement in
catalyst product separation techniques. The use of water as
a solvent has numerous advantages, particularly considering
the environmental issues with conventional organic solvents.
In addition the facile separation strategy ensures efficient
recycle of catalyst, thereby avoiding highly involved separa-
tion techniques, reducing waste, and making the process
1
-5
ecofriendly.
Sulfonated phosphines have been applied
extensively in a variety of biphasic reactions due to their
very high solubility in water. The high solubility of the ligand
enables stabilization of the catalyst in the aqueous phase as
the ligand-to-metal ratio can be very high [triphenyl phos-
phine trisulfonate sodium (TPPTS) solubility in water is
Experimental Section
Materials. The ligand triphenyl phosphine (PPh ) was
procured from Fluka AG, Switzerland. Sulfuric acid (SD,
India), and sodium hydroxide (SD, India) of high purity were
purchased and used as received. All operations were per-
formed under argon atmosphere. Oleum of 65% strength was
prepared from 20% oleum by distillation. Distilled deionized
water was used in all operations. All solvents including water
were degassed prior to use.
3
=
1.1, kg/L]. Water soluble sulfonated phosphines are
generally synthesized by a sulfonation route which has many
advantages such as one-step synthesis, good yields, etc.
However, there are many other disadvantages of direct
sulfonation besides handling oleum, which also should be
considered. The major ones include poor selectivity, forma-
tion of side products, sensitivity towards air, etc. Since,
TPPTS is a component for catalyst synthesis, a relatively
pure compound is desired. However, the synthesis as
described earlier in Table 1, also gives numerous by-products
(6) Gaertner, R.; Cornils, B.; Springer, H.; Lappe P. U.S. Patent 4,483,802,
1984.
(7) Bahrmann, H.; Cornils, B.; Lappe, P.; Springer, H. U.S. Patent 4,710,321,
1
987.
(8) Bahrmann, H.; Cornils, B.; Lappe, P.; Springer, H. U.S. Patent 4,673,535,
987.
9) Kuntz, E. U.S. Patent 4,248,802, 1981.
10) Arhancet, J. P.; Davis, M. E.; Merola, J. S.; Hanson, B. E. J. Catal. 1990,
21, 327.
1
(
(
1
*
Author for correspondence. Telephone/Fax: +91 20 5893260. E-mail:
(11) Ahrland, S.; Chatt, J.; Davies, N. R.; Williams, A. A. J. Chem. Soc. 1958,
276.
rmdesh@ems.ncl.res.in.
(
1) Cornils, B.; Herrmann, W. A. Applied Homogeneous Catalysis with
organometallic compounds; VCH: 1996.
(12) Jenck, J.; Morel, D. U.S. Patent 4,668,824, 1987.
(13) Larpent, C.; Patin, H.; Thilmant, N.; Valdor, J. F. Synth. Commun. 1991,
21, 495.
(14) Bartik, T.; Bartik, B.; Hanson, B. E.; Glass, T.; Bebout, W. Inorg. Chem.
1992, 31, 2667.
(
(
(
2) Joo, F.; Katho, A. J. Mol. Catal. 1997, 116, 3
3) Cornils, B.; Wiebus, E. CHEMTECH 1995, 33.
4) Herrmann W. A.; Kohlpaintner C. W. Angew. Chem., Int. Ed. Engl. 1993,
3
2 1524.
(15) Herrmann, W. A.; Albanese, G. P.; Manetsberger, R. B.; Lappe, P.;
Bahrmann, H. Angew. Chem., Int. Ed. Engl. 1995, 34, 811.
(
5) Kalck, P.; Monteil, F. AdV. Organomet. Chem, 1992, 34, 219.
3
42
•
Vol. 4, No. 5, 2000 / Organic Process Research & Development
10.1021/op0000226 CCC: $19.00 © 2000 American Chemical Society and The Royal Society of Chemistry
Published on Web 07/19/2000

Table 1. Sulfonation of triphenyl phosphine
sr
TPP,
g
H
2
SO
g
4
oleum
g
temp.
time
h
o
no.
C
product
TPPDS
separation
extraction with
triisooctylamine in toluene
same as above
ref
1
2
105
105
960
960
320 (30%)
320 (30%)
15-20
3.5
6-8
(
64%)
TPPDS
33%)
TPPTS
53%)
20
24
8
(
(
3
4
5
100
8
10
1000 (20%)
72 (71%)
38 (20%)
20-40
20-25
25
15-25
19
2
TPPTS
TPPTS
TPPMS
methanol extraction
tributyl phosphate extraction
ethanol extraction
9
10
11
2
(65%)
6
7
8
9
20
20
10
3
112 (65%)
194 (65%)
200 (20%)
40 (65%)
22
50
76
24
150
112
TPPTS
OTPPTS
TPPTS
TPPDS
tributyl phosphate extration
reduced to TPPTS
methanol extraction
methanol extraction
12
13
14
15
40 +
58
3 3
H BO
4
.8
Figure 1. Typical reactions in sulfonation of triphenyl phosphine
Reactor/Apparatus. A double-jacketed 1 L glass reactor
equipped with a high-speed half-moon stirrer and a provision
for monitoring bulk liquid temperature was used. This reactor
was designed so that operations under argon atmosphere were
possible. The temperature was controlled by circulation of
a constant temperature fluid. A similar reactor of larger
volume was used for neutralization of the crude reaction
mixture.
homogeneous yellow-colored solution of triphenyl phosphine
in sulfuric acid was formed. Then 280 g, (141.48 mL; d )
1.98 at 35 °C) of 65% oleum (SO content: 2.275 mol) was
3
introduced into the reactor over a period of 40-45 min, at
a temperature of 15 °C. The temperature of the reaction
mixture was then raised to 22 °C ((0.5) and was maintained
for 76 h. Thereafter, the temperature of the reaction was
lowered to ∼10 °C and the reaction quenched by slow
addition of 50 g of distilled water. The solution of sulfonated
triphenyl phosphine in sulfuric acid thus obtained was further
diluted to approximately 800 mL by addition of cold water
(10 °C). The diluted solution was neutralised (up to a pH of
7-7.2) with a solution of 50% (w/w) degassed sodium
hydroxide. The temperature is maintained at about 10 °C
Synthesis of TPPTS. The following procedure was
standardized for the preparation of TPPTS. Sulfuric acid
(98%, AR) 200 g, was introduced into the sulfonation reactor.
The acid was cooled to 12-15 °C, and 50 g of solid triphenyl
phosphine (190.75 mmol) was introduced at 15 °C over the
course of 30-45 min, for proper temperature control. A
Vol. 4, No. 5, 2000 / Organic Process Research & Development
•
343

Figure 2. Sulfonation of triphenyl phosphine: Typical concentration-time profile Charge: Triphenyl phosphine: 50 g; Oleum
65% SO ): 280 g; H SO : 200 g; Agitation speed: 1000 rpm; Temperature: 22 °C.
(
3
2
4
Table 2. Effect of temperature on sulfonation of triphenyl
phosphine
during the entire operation. During the course of neutrali-
sation, sodium sulfate precipitated from the solution. This
reaction mixture containing sodium sulfate/TPPTS was
III
PV,%
P , %
serial temp.
9
processed by the method reported by Kuntz. (This involved
o
no
C
TPPMS TPPDS TPPTS OTPPTS STPPTS
concentration of the neutralised solution, and separation of
the sodium sulfate by addition of methanol. This exercise
was repeated a few times and the final extract was with hot
methanol. The methanolic solution was evaporated to dry-
ness. The TPPTS was purified by washing with ethanol and
1
2
3
20
22
30
10.2
6.1
3.4
84.6
90.1
84.4
4.8
3.8
12.2
a
Charge: triphenyl phosphine: 50 g; oleum (65% SO
g; agitation speed: 1000 rpm; time: 76 h.
3 2 4
): 280 g; H SO : 200
characterised.) For the kinetic studies, periodic samples were
1
withdrawn, quenched with water and D
2
O, and 3 P NMR
spectra recorded for the quantification of the products.
typical consecutive reaction with sequential formation of
mono-, di-, and trisulfonated products. TPPMS is formed
very rapidly in the initial stages and passes through a
maximum at around 12 h where 55% of TPPMS was
observed. The formation of TPPDS was about 42% which
increases to 65% in 24 h. Formation of TPPTS was observed
at 12 h. At 24 h most of TPPMS is consumed and only
TPPDS and TPPTS are major products. At 76 h the
maximum TPPTS is formed (90%). At this point 6% TPPDS
was also present. The remainder was OTPPTS. On prolonged
reaction for 105 h both TPPDS and TPPTS dropped with a
subsequest rise in oxide. The formation of STPPTS is also
observed in minor quantities (1%). Sulfonated phosphines
are very sensitive to traces of oxygen, and they are easily
oxidized to the corresponding oxides, formed during syn-
thesis of TPPTS as:
31
1
Typical NMR signals were obtained as P{ H NMR (D
2
O,
III
V
2
00 MHz, 25 °C), δ -4.8 (P ) and δ 34.2 (P ) which are
14,15
consistent with literature.
Results and Discussion
TPPTS was obtained by treating triphenylphosphine with
oleum and by subsequent neutralization of the reaction
mixture with saturated sodium hydroxide solution. The
reaction scheme is shown in Figure 1. The following
conditions were chosen from the literature for carrying out
the sulfonation reaction12
Reaction charge:
(
(
(
1) SO /TPP ) 12 molar ratio
3
2) SO /(SO + H SO + TPP) ) 34% (w/w)
3
3
2
4
TPPXS + O f OTPPXS
2
3) H SO /(SO + H SO + TPP) ) 56% (w/w)
2
4
3
2
4
Temperature: 22 °C
where X ) mono-, di-, or trisulfonate.
These oxides are inactive as ligands and thus the presence
of these in small quantities in the final TPPTS solution does
not pose any problem in catalytic activity. The formation of
Agitation speed: 1000, rpm
The results are presented in Figure 2. Sulfonation is a
344
•
Vol. 4, No. 5, 2000 / Organic Process Research & Development

a
Table 3. Effect of agitation speed on sulfonation of
3
non uniform distribution of the highly reactive SO in
a
triphenyl phosphine
reaction medium. In a magnetically agitated system very poor
selectivity similar to that at lower agitation speed is observed.
Hydroformylation Reactions. The TPPTS synthesised
was tested for its activity in hydroformylation. For this
purpose a 50 mL stirred reactor was used, as described
III
PV, %
P , %
serial
no
agitation
speed, rpm TPPMS TPPDS TPPTS OTPPTS STPPTS
1
magnetically
agitated
300
600
1000
55.0
40.3
4.7
16
elsewhere.
2
3
4
42.1
25.1
6.1
58.0
71.5
90.1
2.3
3.4
3.8
(i) Hydroformylation of ethylene was carried out under
following conditions: temperature: 40 °C, solvent: toluene-
water system (aqueous phase hold-up 0.4), catalyst [Rh-
a
Charge: Triphenyl phosphine: 50 g; oleum (65% SO
3
2 4
): 280 g; H SO : 200
-
4
3
g; temperature: 22 °C; time: 76 h.
(COD)Cl]
2
: 5.0 × 10 kmol/m ; Rh:TPPTS, 1:6; and a
P
ethylene ) PCO ) PH2 of 0.669 Mpa for 1 h. The rate of
-
5
3
reaction was found to be 3.45 × 10 kmol/m /s, with 98%
oxides can be avoided by maintaining an argon atmosphere
during sulfonation reaction and by controlling reaction time.
The sulfide derivative is also observed after prolonged
reaction times. It is formed as per reaction shown in Figure
. Sulfides are known to poison the catalyst, and formation
of these must be avoided.
The selectivity profile of this reaction is extremely
sensitive to temperature (Table 2). A lowering of temperature
by 2 °C has a pronounced effect on the sulfonation rate, and
selectivity to propionaldehyde.
(ii) Hydroformylation of octene-1 was also undertaken
using the above synthesised TPPTS under the following
conditions: temperature: 100 °C, solvent: toluene-water
system (aqueous phase hold-up 0.4), catalyst [Rh(COD)Cl] :
2
1
-
2
3
1
0
.0 × 10 kmol/m ; Rh:TPPTS, 1:6; octene-1 concentration
3
.85 kmol/m ; PCO ) PH2 ) 2.07 Mpa for 9 h. The rate of
-6
3
reaction was found to be 5.36 × 10 kmol/m /s, with >95%
selectivity to aldehydes, and octene-1 conversion of 23%.
An n/iso ratio was found to be 1.02.
1
0% TPPDS is observed (as against 6% at 22 °C). Likewise
TPPTS formation is also reduced. At 30 °C, the oxide
formation is high (12% as against 4%) which indicates that
high temperatures favour the formation of OTPPTS.
Conclusions
The consecutive reaction of sulfonation of triphenyl
phosphine to TPPTS is found to be extremely sensitive to
the reaction temperature and agitation. The reaction time to
obtain TPPTS in acceptable yield and desirable purity has
been optimized. The TPPTS synthesized in combination with
Rh complex catalyst was active for hydroformylation in a
biphasic system.
3 2 4
The SO /H SO mixture is viscous at reaction temperature
(
22 °C), and thus to ensure the uniform reaction it is
necessary to have an efficient agitation. The effect of
agitation speed has been given in Table 3. It has been
observed that TPPTS selectivity is enhanced with increase
in the agitation speed. Although complete conversion of
TPPMS is observed under all agitation speed, subsequent
sulfonation needs an efficient mixing. This may be due to
Received for review February 24, 2000.
OP0000226
(
16) Bhanage, B. M. Ph.D. Thesis, University of Poona, 1995.
Vol. 4, No. 5, 2000 / Organic Process Research & Development
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