Note: Descriptions are shown in the official language in which they were submitted.
2~2~3
Sulfonated propylphenylphosphines,
their preparation and use
The invention relates to novel sulfonated propylphenyl-
phosphines, the preparation of these compounds and their
use as a constituent of catalyst systems.
The preparation of sulfonated phenylphosphines is known.
The sodium salt of m-sulfophenyldiphenylphosphine is thus
obtained by reacting triphenylphosphine with oleum,
heating the reaction mixture on a water bath, diluting
the reaction product with water and neutralizing the
mixture with sodium hydroxide. The desired compound then
crystallizes out of the mixture ~J. Chem. Soc. 1958, page
281/282).
The sodium salts of di~m-sulfophenyl)phenylphosphine and
tri(m-sulfophenyl)phosphine are also obtained by sLmilar
processes. The starting substance in both cases is again
triphenylphosphine, which is reacted with oleum at
temperatures between 18 and 40C over a period of 15 to
; 20 63 hours. The reaction product is likewise diluted with
water and neutralized with sodium hydroxide, and it
should be ensured that temperatures b010w 20C are
maintained in the mixture during the addition of the
sodium hydroxide (German Patent 2,627,354).
Treatment of the sodium salts with a cation exchanger
resin gives the free acids, which can be reacted with
various bases to give other salts. The barium and the
tetraethylammonium salt of tri(m-sulfophenyl)phosphine,
for example, can be prepared by this route (German Patent
2,627,354).
Sulfonated arylphosphines are employed, inter alia, as
components of catalyst systems~ Org nic phosphines which
also additionally contain alkyl radicals bonded directly
to phosphorus, as well aq sulfonated phenyl radicals,
have not been described to date.
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The invention relates to representatives o~ this novel
class of substance, namely the compounds n-propyl(phenyl)-
(m-sulfophenyl)phosphinel (n~C~H7)(C6H5)(C6H4-m-SO~H)P,
n-propyldi(m-sulfophenyl)phosphine~ (n-C3H7)(C6H4-m-SO3H)2P,
the sodium salts o~ n-propyl(phenyl)(m-sulfophenyl)-
phosphine, (n-C3H7)(C6H5)(C6H4-m-SO3Na)P and of n-propyl-
di(m-sulfophenyl)phosphine, (n-C3H~)(C6H4-m-SO3Na)2P, and
the sodium salts of n-propyl(phenyl)(m-sulfophenyl)-
phosphine oxide, (n-C3H7)(C6H~)C6H4-m-SO3Na)PO and of
n-propyldi(m-sulfophenyl)phosphine oxide,
(n-C3H7~(C6H4-m-SO3-Na)2PO-
The invention further~[lore relates to a process for the
preparation of the novel compounds. It comprises
sulfonating propyldiphenylphosphine with oleum at tem-
peratures below 10C, hydrolyzing the sulfonation pro-
duct, neutralizing the hydrolyzed product with an alkali
metal carbonate or alkali metal hydroxide, separating off
the alkali metal sulfate, concentrating the aqueous
solution, extracting the sulfonated propylphenylphos-
phines from the dry residue, separating the mono- and
disulfonated product by gel chromatography and if approp-
riate converting the salts of the mono- and disulfo-
phenylphosphine into the free sulfonic acids by ic n
exchange or into the corresponding phosphine oxides by
oxidation.
.
The propyldiphenylphosphine required for the preparation
of the novel compounds is obtained from diphenylphosphine
and propyl bromide in the presence of a suitable base,
for example gOH (cf. Tsvetkov et al., Synthesis 1986,
page 198 et seq.). Diphenylphosphine is accessible from
chlorodiphenylphosphine by reaction with lithium aluminum
hydride at 0C and subsequent hydrolytic working up
(Ruchen et al., Chem. Ber. 91, 2871 (1958)~.
To introduce the sulfonic acid groups into the phenyl
radicals, the alkyldiarylphosphine is treated with excess
sulfur trioxide in the form of oleum as the sulfonating
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-- 3 --
agent. It has proved appropriate to employ oleum which
contains 10 to 65 and in particular 20 to 30~ by weight
of ~free~ sulfur trioxide. The sulfonating agent is to be
used in excess, relative to the phenyl radicals. 1 to
200, preferably 3 to 30, mol o~ S03 are advantageously
employed per mol of phenyl radical. In practice, the
oleum is initially introduced and the phosphine is added
in portions, in order to ensure a constant SO3 excess.
The sulfonation is carried out at low temperatures, i.e.
at temperatures <15C, preferably at 0 to 8C. It has
proved appropriate to cool the reactor well and to
introduce the phosphine slowly and in small portions into
the oleum, so that the heat of reaction can be removed
without effort. This means that the sulfonation does not
proceed in an uncontrolled manner, but in each case only
one -SO3H group enters into one or into both phenyl
radicals, and in paxticular mainly in the meta-position.
After addition of all the phosphinet the after-reaction
can be carried out at room temperature and essentially
without external cooling. However, it is advantageous to
stir the reaction mixture so that any heat of reaction
possibly still arising can be uniformly distribut~d and
removed without delay. Longer reaction times are neces-
sary, corresponding to the low temperature. In general,
the reaction has ended after 20 to 100 hours, usually
after 40 to 60 hours, in the temperature ranges
mentioned.
After the sulfonation~ the reaction solution is diluted
(hydrolyz~d) with ice-water. During this process step it
should ~e ensured that a temperature of about 30C is not
exceeded, and it i advantageous to maintain temperatures
in the range from 0 to 10C. The dilute solution, essen-
tially containing the sulfonation product and sulfuric
- acid, is then neutralized. Sui~able alkaline reagen~s are
the alkali metal hydroxides and the alkali metal carbon-
ates, and it is advantageous to employ sodium hydroxide.
To avoid a further increase in the volume of the reaction
~3~3
-- 4 --
mixture and to achieve a substantial deposition of the
alkali metal sulfate which forms, the neutralizing agent
is used as a highly concentrated solution or in undis-
solved solid form, for example caustic soda flakes or
granules.
Most of the alkali metal sulfate is removed from the
solution by cooling, on the basis of it~ lower solubility
at low temperatures. The suitable temperatures depend on
the concentration of the sulfate in the solution and its
solubility as a function of the temperature. The most
favorable conditions are therefore to be determined rom
case ~o case by experiments. The sulfate can be removed
in one or more stages, and it has proved advantageous to
carry out the crystallization in two stages.
After khe deposition of the alkali metal sulfate, the
solution i concentrated to dryness, preferably in the
vacuum of an oil pump. The sulfonated propylphenylphos-
phines are extracted from the crystal magma. Suitable
extraction agents are mixture of lower alcohols, such as
methanol, ethanol and propanol, with water. A mixture of
7 parts by volume of methanol and 5 parts by volume of
water, for example, has proved to be a suitable extxac-
tion agent. The extraction is carried out by conventional
processes in one or more stages, preferably two to our
- 25 stages. The extracts are combined and concentrated to
dryness. The residue essentially consists of the mono-
sulfonated compound (n-C3H7)P(C6H5~(C6H4-m-S03Na) and the
disulfonated compound (n-C3H7)P(C6H4-m-S03Na~2
The mixture of sulfonat~d alkylarylphosphines is separa-
ted by gel chromatoyraphy, a process which is described
in German Patent Application P 3,822,036.9. Modified
organic polymers are employed as stationary solid phases,
and dextran~ crosslinked with epichlorohydrin (commerci-
ally available under the name Sephadex) and oligoethylene
glycol/glycidyl dLmethacrylate/pentaerythritol dimetha-
crylake copclymer~ (commercially availablè under the name
~32~
-- 5 --
Fractogel) have proved to be particularly appropriate.
Water or water/solvent mixtures are used as the liquid
phase, "solvent" being a water-miscible organic solvent,
preferably methanol and other lower alcohols.
The free acids can be prepared from the salt3 by treat-
ment of the solutions of the sodium salts of the
sulfonated alkylarylphosphines with a cation exchanger in
the H+ form, and they can be isolated in bulk by concen-
trating the aqueous solutions. Other salts of the novel
sulfonated alkylarylphosphines can be prepared from the
acids by reaction with hydroxides, carbonates, ammonia or
amines.
The novel compounds are colorless, crystalline sub-
stances. The sodium salts contain up to one molecule of
water per sodium ion, depending on the degree of drying.
Complete deh~dration is possible by heating of the
hydrate forms at 60 to 100C, preferably 65 to 80C, in
a high vacuum for several hours (3 to 15 hours). The
protection claimed therefore extends both to the hydrated
and to the anhydrous compounds.
The novel compounds ha~e proved suitable as components of
catalyst systems, in particular those which contain
metals of group VIII ~ of the Periodic Table and wat~r-
so~uble phosphines. They contribute towards increasing
the thermal sta~ility of such systems.
The pr~paration of the novel compounds is described in
the following e~ample.
Example
Sulfonation of (n-propyl)diphenylphosphine
- 30 29.1 g (128 mmol) of propyldiphenylphosphine are added
dropwise to 290 ml of oleum (S03 content: 20% by weight~
in a 500 ml three-necked flask fitted with an internal
thermometer and dropping funnel at 5~C under temperature
20323~3
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control in the course of one hour. The mixture is cooled
in an ice-bath so that the internal temperature does not
exceed 8C during the phosphine addition. The reaction
mixture is stirred at room temperature for two days and
then poured onto 3 kg of crushed ice for hydrolysis of
the excess oleum. It is then ne11tralized with 0.45 kg of
sodium hydroxide in 1 1 of water and the solution is
brought to a pH of about 7 by addition of sulfuric acid
and stored at 6C for three days. The crystallization of
sodium sulfate is then started by stirring and the salt
is filtered off and washed with ice-water. The filtrate
and wash water are concentrated in the vacuum of a rotary
oil pump over a cold trap. The mono- and disulfonated
product are separated from one another by gel chromato-
lS graphy. Sodium sulfate run the fastest. This is followedby the disulfonated product, which thus forms the second
zone. The monosulfonation product finally runs as the 3rd
zone. Detection of the product is by W/VIS spectroscopy
or by refractometry. The products are dried in the vacuum
of an oil pump in a water bath (28C) for 10 hours.
a) (n-C3H7)P(C6H5)(C6H4-m-SO3Na) ~ HzO
Characterization:
31P-NMR (109.3 MHz, D2O, 5C): ~ = -15.51 (s)
lH-NMR (270 MHz, D20, 28C: ~ = 0.61 ppm (br, 3H),
~ = 1.05 ppm (br, 2H)
= 1.66 ppm (br, 2H), ~ = 6.g6 - 7.72 ppm
(m, 9H) - abbreviation: br = broad signal form.
Elemental analysis: (Cl5H18NaO4PS; 348.32)
calculated C 51.72 H 5.21 O 18.37 P 8.89 S 9.19
found C 52.96 H 5.0~ O 18.10 P 9.06 S 9.02
b) (n-C3H~)P~C~H4-m-SO3Na)2 2 H2O
Characterization:
31P-NMR (109.3 MHz, D2O, 5C): ~ = 15.05 ppm (s)
2 ~ 3
Elemental analysis: ~C15H1gNa2O8PS2; 468.99)
calculated C 38.42 H 4.08 O 27.29 P 6.60 S 13.67
found C 38.30 H 4.11 O 27.91 P 6.53 S 14.20
The two propyldiarylphosphines can be oxidized quantita-
tively to the corresponding phosphine oxides with excess
30% strength hydrogen peroxide in aqueous solution if the
components are heated at about 80C for 5 minutes. If the
pure propyldiarylphosphines are used as the starting
substances (see above), further purification of the
phosphine oxides (for example by gel chromatography,
which is possible in principle), is no longer necessary.
The phosphine oxides are characterized in a simple manner
by 31P-N~ spectroscopy in D2O solution at 21C and a
measurement frequency of 109.3 MHz:
(n-c3H7)(c6Hs)(c6H4-m-so3Na)p=o = 41.58 ppm (singlet)
(n-C3H7)(c6H4-m-so3Na)2p=o = 41.08 ppm (singlet)
These are colorless substances which are stable in air
and heat-stable to far above 100C.
