Water-soluble-phosphines-assisted cobalt separation in cobalt-catalyzed hydroformylation

Article abstract of DOI:10.1021/om400579f

The hydroformylation of octene-1 and the removal of Co₂(CO) ₈ and HCo(CO)₄ from the reaction products including commercial C9 OXO-product were studied under biphasic conditions using an aqueous solution of different electr

Full text of DOI:10.1021/om400579f

Article
pubs.acs.org/Organometallics
Water-Soluble-Phosphines-Assisted Cobalt Separation in Cobalt-
Catalyzed Hydroformylation
Laszlo T. Mika,†,‡ Laszlo Orha,† Eddie van Driessche,⊥ Ron Garton,⊥ Katalin Zih-Perenyi,†
́
́
́
́
́
and Istvan T. Horvath*,†,§
́
́
†Institute of Chemistry, Eotvos University, Paz
́ ́ ́ ́ ́
many Peter setany 1/A, H-1117 Budapest, Hungary
̈
̈
‡Department of Chemical and Environmental Process Engineering, Budapest University of Technology and Economics, Budafoki str.
8, H-1111 Budapest, Hungary
§Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong, China
⊥ExxonMobil Chemical Europe, Hermeslaan 2, 1831 Machelen, Belgium
ABSTRACT: The hydroformylation of octene-1 and the removal of Co2(CO)8 and HCo(CO)4 from the reaction products
including commercial C9 OXO-product were studied under biphasic conditions using an aqueous solution of different electron-
donating sulfonated phosphine RnP(C6H4-m-SO3Na)2 (n = 0, 1, 2; R = Me, Bu, Cp) ligands. Depending on the electronic and
steric properties of the phosphines, 6−70 ppm residual cobalt concentrations could be achieved in the organic phase under 10
bar of CO/H2 (1:1) at 75 °C. The formation of several water-soluble-phosphine-substituted cobalt carbonyl species including
Co2(CO)6(TPPTS)2, HCo(CO)3(TPPTS), HCo(CO)2(TPPTS)2, and [Co(CO)3(TPPTS)2]+[Co(CO)4]− were identified and
monitored by in situ IR and NMR spectroscopy.
modified rhodium catalyst was commercialized by Union-
Carbide (now Dow Chemical) and has become the most
frequently used technology for the selective hydroformylation
of α-olefins to linear oxo-aldehydes.5
INTRODUCTION
■
The hydroformylation of olefins to aldehydes (oxo-aldehydes)
has become one of the most important industrial homogeneous
catalytic processes (Scheme 1).1 Although different transition
The efficient separation of the homogeneous oxo catalysts
has been a formidable challenge for all commercial systems; a
significant part of the research work has been directed toward
the development of novel catalytic systems with facile catalyst
recycling through molecular level control. Biphasic systems
based on water,6 fluorous7 and ionic liquids,8 and supercritical
carbon dioxide9 have been tested successfully as reaction media
to facilitate catalyst recycling.10
Tertiary phosphines (PR3) are the most important and
widely used ligands to modify the properties of transition metal
catalysts. The physical and chemical properties including the
solubilities of phosphine ligands can be fine-tuned by
controlling the structure of their substituents.11 The first
industrial aqueous biphasic system using the trisulfonated-
triphenylphosphine (TPPTS)-modified rhodium catalyst, the
Scheme 1. Hydroformylation Reaction
metals can be used as catalysts,2 cobalt and rhodium have been
the preferred commercial catalysts in the absence or the
presence of phosphine ligands.3 The unmodified cobalt catalyst
was discovered by Otto Roelen 75 years ago and has been used
for the hydroformylation of olefin mixtures successfully to
produce oxo-aldehydes by Esso (now ExxonMobil) for decades.
The alkyl-phosphine-modified cobalt catalyst process was
developed by Shell, which resulted in the in situ hydrogenation
of the oxo-aldehydes to oxo-alcohols.4a In the case of rhodium-
based systems, the unmodified rhodium catalyst was used
commercially by ICI for decades.3 The triphenylphosphine-
Received: June 19, 2013
© XXXX American Chemical Society
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heart of the Rurhchemie/Rho
Article
̂
ne-Poulenc process (Scheme 2),
The unmodified cobalt-based catalyst has been used for the
hydroformylation of olefins to oxo-aldehydes with a typical
normal/iso (or n/i) ratio of 2. The three main cobalt species of
the organic phase of any unmodified cobalt-based process are
HCo(CO)4, Co2(CO)8, and the acyl-Co(CO)4 species, which
could be formed by the reaction of HCo(CO)4 and α-olefins.22
Since the α-olefins react faster than the internal olefins,
HCo(CO)4 and Co2(CO)8 are the only observable species at
high conversion level in a typical reaction mixture. While the
volatile HCo(CO)4 can be removed at lower pressures, the
separation of Co2(CO)8 from the reaction mixture is difficult.
Two processes have been developed for the removal of cobalt
at the industrial scale. The first involves the decobalting of the
crude oxo mixture after depressurization by the addition of
oxygen and organic acid (HCOOH or AcOH).23 The second
method starts with the treatment of the crude reaction mixture
with a diluted aqueous solution of NaHCO3 to convert
HCo(CO)4 to Na[Co(CO)4], which can be then protonated
by the controlled addition of diluted sulfuric acid.24
The tributyl-phosphine-modified cobalt catalyst system was
developed in the late 1950s,4 which forms an active and stable
catalyst even at lower syngas pressures (20−100 bar) and
produces alcohols rather than aldehydes.25,26 The concen-
tration of branched alcohols and aldehydes can be decreased by
increasing the concentration of PBu3.27 Because of the higher
thermal stability of the tributyl-phosphine-modified cobalt
catalyst, the hydroformylation can be performed at higher
temperatures, which assists the formation of alcohols with
similar selectivity. Although, the higher syngas pressure should
favor the aldehyde formation, this influence could be
compensated by applying higher hydrogen partial pressure.28
Water has been shown to have dramatic effects on the tributyl-
phosphine-modified cobalt catalyst including a higher rate of
alcohol formation and a water-dependent alcohol/aldehyde
ratio. It was shown that the maximum alcohol concentration
can be achieved at 14 v/v % of water.29
Similarly to the biphasic rhodium recycling, several
approaches based on biphasic catalysis have been reported for
cobalt separation,30 including aqueous31 and fluorous sys-
tems.32 Since TPPTS has been the most widely used water-
soluble phosphine ligand, the synthesis of its cobalt complexes
has been also reported including HCo(CO)3(TPPTS), HCo-
( C O ) 2 ( T P P T S ) 2 , [ C o ( C O ) 3 ( T P P T S ) ] − , a n d
Co2(CO)6(TPPTS)2.33 The reaction of Co2(CO)8 with
TPPTS results in the formation of [Co(CO)3(TPPTS)][Co-
(CO)4]. The relatively stable Co2(CO)6(TPPTS)2 undergoes
base-induced disproportionation above pH = 10 to yield
[Co(CO)3(TPPTS)]− as the only carbonyl-containing species.
While the Co/TPPTS catalyst is less active than the Rh/
TPPTS catalyst, it is superior for the hydroformylation of
internal olefins under 20−105 bar of H2/CO (1:1) and at 130−
was developed by Kuntz12 and commercialized by Cornils.13
Scheme 2. The Rurhchemie/Rhone-Poulenc Process
̂
A typical plant produces more than 6 × 105 tons of butanal
annually, and depending on the propene quality, a conversion
of 99% with an n/i ratio of approximately 95:5 of the crude
butanal can be maintained. The process successfully utilizes the
high and low solubility of propene or normal- and iso-butanals
in water, respectively. The catalyst leaching has been kept at a
very low level because of the easy and efficient aqueous/organic
phase separation.13
The use of aqueous systems is limited by the solubility of the
olefins in water, which depends on the structure of the
olefins.14 The replacement of the water-soluble ligands of
HRh(CO)(TPPTS)3 with a fluorous phosphine P-
[CH2CH2(CF2)5CF3]3 led to the development of the first
fluorous biphasic hydroformylation system.15 The HRh(CO)-
(P[CH2CH2(CF2)5CF3]3)3 was successfully tested in the
continuous hydroformlyation of decene-1 using the toluene/
C6F11CF3 system as the reaction media. The normal/iso ratio
of 8:1 was achieved, and the fluorous system efficiently
moderated the rhodium loss at the 1 ppm rhodium per mole
of aldehyde level. The rhodium leaching was further reduced by
the application of the P[p-C6H4-(CH2)8(C6F13)]3 ligand.16 The
use of fluorous-phosphine-modified Rh catalysts for the
hydroformylation of octene-1 in supercritical carbon dioxide
has resulted in a homogeneous environment, in which many
low- or medium-polarity olefins and catalysts can be dissolved
(Scheme 3).9b Although the supercritical fluid can readily be
removed at lower pressures, it does not overcome the original
catalyst/product separation problem.
Due to the very low vapor pressure of ionic liquids, they have
been used as alternative solvents.17 The first hydroformylation
reaction in molten salts using a Pt-based catalyst was reported
by Parshall in 1972.18 Both the Rh(CO)2(acac)/PPh3 system
and the rhodium complex of the sodium salt of the sulfonated-
phenylphosphines were found to be active hydroformylation
catalysts applying ionic liquids as solvents as well;19,20 however
the conversions were very low. The immobilization of the
solution of rhodium catalysts in an ionic liquid−organic
biphasic environment was reported by Mehnert.21
Scheme 3. Hydroformylation in Supercritical Carbon Dioxide
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190 °C. Aldehyde yields up to 75% could be realized with an n/
i ratio between 1 and 3. Depending on the reaction conditions,
between 9 and 60 ppm of the total cobalt was found in the oxo-
product phase after catalyst separation. The biphasic hydro-
formylation of hexene-1 to heptanals using
Co2(CO)6(TPPTS)2 resulted in 0.5−10% Co leaching;
however, the application of glass as a catalyst support could
reduce this value to 0.1%.31 Although various types of
sulfonated and carboxylated aryl phosphines have been tested
for the hydroformylation of hexene-1,34 the application of
water-soluble-alkylphosphine-modified cobalt catalysts has not
been studied yet.
The application of in situ spectroscopy could provide the
molecular level information under reaction conditions in real
time to structurally identify key intermediates of the catalytic
cycle and develop the reaction network between substrates,
catalyst precursor(s), intermediates, products, and side-
products.35 Although, several water-soluble-phosphines-modi-
fied cobalt carbonyl species have been prepared and
characterized,33 no in situ spectroscopic studies have been
reported on their transformations yet.
First, a single-phase cobalt-catalyzed hydroformylation of
octene-1 was performed for comparison. A solution of 25 mL of
octene-1 in 30 mL of n-hexane was placed in a 250 mL high-
pressure reactor, equipped with a high-pressure SiComp IR
probe attached to a ReactIR 1000 in situ reaction analysis
instrument. The reaction mixture was pressurized with CO/H2
(1:1) to reach 100 bar at 100 °C. The presence of a band of 1-
octene at 1656 cm−1 was observed (Figure 2a). After the
addition of a solution of 0.982 g (2.87 mmol) of Co2(CO)8 in
10 mL of n-hexane under 102 bar of CO/H2 (1:1), the bands at
2070 and 2030 cm−1 appeared due to Co2(CO)8 and
HCo(CO)4. After a few minutes new peaks appeared at 2005
and 2103 cm−1, indicating the formation of the acyl-cobalt
species. The band at 1733 cm−1 showed the formation of the
nonanals (Figure 2a). The n/i ratio was 2.1 at 95% olefin
conversion after 1.5 h.
RESULTS AND DISCUSSION
■
We report here the modification of the cobalt oxo process by
the introduction of water-soluble phosphine ligands to assist
the recycling of the cobalt catalyst and the in situ partial
conversion of the aldehydes to the alcohols. The separation of
the cobalt is based on the facile substitution of the carbonyl
ligands of various cobalt carbonyls, mostly HCo(CO)4 and
Co2(CO)8, by water-soluble phosphines, making all cobalt
species preferentially water-soluble at lower syngas pressure
(Scheme 4).
Scheme 4. Substitution Reactions of Cobalt-Carbonyls
We also investigated the possible effect of changing the order
of the addition of octene-1 and Co2(CO)8. A solution of 1.04 g
(3.04 mmol) of Co2(CO)8 in 55 mL of n-hexane was placed in
a 250 mL high-pressure reactor, equipped with a high-pressure
SiComp IR probe attached to a ReactIR 1000 instrument. The
reaction mixture was pressurized with CO/H2 (1:1) to reach
100 bar at 100 °C. The formation of HCo(CO)4 could be
observed by the appearance of the bands at 2030, 2053, and
2117 cm−1. After reaching the equilibrium between Co2(CO)8
and HCo(CO)4, 25 mL (160 mmol) of octene-1 was added,
resulting in the transient formation of the acyl-cobalt species
(2005 and 2103 cm−1) and the formation of nonanals (1733
cm−1) with the same conversion and selectivity (Figure 2b) as
observed in the previous experiment. Thus, we have confirmed
that the order of the addition of the olefin and the catalyst has
no effect on product formation, as expected.
After the separation of the oxo product, the repressurization
of the aqueous phase leads to the re-formation of the organic-
soluble cobalt carbonyls and free water-soluble phosphines,
which can be recycled to the oxo reactor (Figure 1). The
presence of water and the water-soluble phosphine could
provide additional benefits including better hot-spot control, in
situ hydrogenation of the aldehydes to alcohols, and
suppression of the side reactions involving the formation of
water.
Next, we studied the biphasic hydroformylation of octene-1
(64 mmol) with TPPTS-modified cobalt catalyst using
Co2(CO)8 (2.9 mmol) in 45 mL of n-hexane and TPPTS
(5.8 mmol) in 10 mL of water under 100 bar CO/H2 (1:1) at
100 °C (TPPTS/Co = 1). While the in situ IR studies have
Figure 1. Proposed process for water-soluble-phosphine-assisted cobalt recycling.
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Figure 2. One-phase hydroformylation reactions of octene-1.
shown the full conversion of octene-1 to nonanals, GC-MS
measurements confirmed the formation of normal- and iso-
nonanals (n/i = 3.2). Only trace amounts of nonanols and
nonanoic acids could be detected. After the phase separation of
the reaction mixture, the aqueous phase was reused as the
catalyst phase under the same conditions, which resulted in
similar product composition with full conversion of octene-1.
Although in situ IR did not show the presence of HCo(CO)4 in
the organic phase, the octene-1 could be converted to nonanals
in the presence of the Co/TPPTS catalyst system operating at
100 bar of CO/H2 (1:1) and 100 °C. 31P NMR of the aqueous
phase revealed the presence of several TPPTS-containing
cobalt species including Co2(CO)6(TPPTS)2 at 70.0 ppm,
[Co(CO)3(TPPTS)2]+[Co(CO)4]− at 57.5 ppm, HCo-
(CO)3(TPPTS) at 58.4 ppm, HCo(CO)2(TPPTS)2 at 56.6
ppm, HCo(CO)(TPPTS)3 at 55.6 ppm, TPPTS-oxide at 35.6
ppm, and TPPTS at −4.2 ppm.33 It should be noted that the
substitution of HCo(CO)4 with TPPTS was performed in THF
containing 5−10% H2O as solvent, and no biphasic system was
reported.33
Figure 3. Removal of 1.54 mmol of HCo(CO)4 in 5 mL of n-hexane
by the addition of an aqueous solution of TPPTS (1 mmol and then
0.875 mmol) under 1 bar of CO at room temperature.
can be removed from the organic phase by using an aqueous
solution of more than one equivalent of TPPTS under biphasic
conditions.
In order to observe the formation of these cobalt species, we
have monitored the reaction of HCo(CO)4, the precursor of
the catalytically active unsaturated cobalt carbonyl {HCo-
(CO)3}, with TPPTS by in situ IR under carbon monoxide at
room temperature. A solution of 1.54 mmol of HCo(CO)4 in 5
mL of n-hexane was prepared by the reaction of NaCo(CO)4
and gaseous HCl at −78 °C under nitrogen. After the removal
of NaCl by filtration and warming the solution to room
temperature, the solution was first treated with less than one
equivalent (1 mmol) of TPPTS dissolved in 5 mL of water.
While the color of the aqueous phase changed from colorless to
light orange and then to dark brown, the rapid decrease of the
amount of HCo(CO)4 in the organic phase could be observed.
All HCo(CO)4 could be removed from the solution by the
addition of 1 mL of an aqueous solution of 0.875 mmol of
TPPTS, resulting in a P/Co ratio of 1.21 (Figure 3 and Figure
4).
Although the formation of Co2(CO)2 was not observed in
the organic phase, the possibility of its removal by TPPTS was
also confirmed by the addition of 5 mL of an aqueous solution
of 0.4 mmol of TPPTS to 0.2 mmol of Co2(CO)8 in 5 mL of n-
octane under 1 bar of CO/H2 (1:1) at 50 °C (Figure 5). The
31P NMR of the aqueous phase indicated that the main cobalt
species were Co2(CO)6(TPPTS)2 (69.6 ppm) and [Co-
(CO)3(TPPTS)2]+[Co(CO)4]− (58.3 ppm).
Thus, we have demonstrated that both HCo(CO)4 and
Co2(CO)8 can be removed from the organic phase with an
aqueous solution containing at least one equivalent of TPPTS
with respect to cobalt under biphasic conditions. On the basis
of our in situ IR results and the relevant reported reactions of
cobalt carbonyls with tertiary phosphines,33,36 the proposed
reactions of the aqueous cobalt recycling can be summarized as
depicted in Scheme 5. In the absence of α-olefins, the two main
cobalt species are HCo(CO)4 and Co2(CO)8 under oxo
conditions, both of which can be converted to water-soluble
TPPTS-containing cobalt species by substitution reactions at
lower syngas pressures and transfer of the cobalt from the
product organic phase to the aqueous phase. Since these
substitution reactions are reversible, both HCo(CO)4 and
Co2(CO)8 can be regenerated at higher syngas pressures,
resulting in the transfer of the cobalt from the aqueous phase to
the organic phase.
The 31P NMR measurement of the aqueous phase indicated
the formation of Co2(CO)6(TPPTS)2 (69.6 ppm), HCo-
(CO)3(TPPTS) (61.0 ppm), [Co(CO)3(TPPTS)2]+[Co-
(CO)4]− (58.3 ppm), and HCo(CO)2(TPPTS)2 (57.2 ppm).
Free TPPTS could not be observed, as expected. The addition
of 0.875 mmol of TPPTS resulted in the formation of
Co2(CO)6(TPPTS)2 (69.7 ppm), HCo(CO)2(TPPTS)2 (57.2
ppm), and [Co(CO)3(TPPTS)2]+[Co(CO)4]− (58.3 ppm).
The excess of TPPTS at −4.8 ppm and the presence of TPPTS
oxide at 35.4 ppm could also be detected. Thus, HCo(CO)4
The facile removal of cobalt from the products of industrial
hydroformylation is indeed one of the key issues concerning
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Figure 4. Removal of HCo(CO)4 (1.54 mmol) from n-hexane with an aqueous solution of TPPTS (5 mL) under 1 bar of CO at room temperature.
Reaction profiles of the bands of HCo(CO)4.
Figure 5. Removal of Co2(CO)8 from n-octane with an aqueous solution of TPPTS.
concentration is dictated by the required process performance,
the total concentration of the water-soluble ligand can be
adjusted to maximize the removal of the cobalt. We have
therefore investigated the cobalt removal at two different
concentrations of TPPTS while keeping the cobalt concen-
trations the same. Since the formation of phosphine-substituted
cobalt carbonyls is strongly dependent on the concentration of
carbon monoxide and the phosphine ligand, the cobalt
concentration in the organic phase was also measured at a
lower pressure of syngas and a higher concentration of TPPTS.
Furthermore, our investigations were performed at 75 °C to
enhance the formation of cobalt-phosphine species but operate
at an easily and economically maintainable temperature by
using industrial process water.
Scheme 5. Proposed Mechanism of the Aqueous Cobalt
Recycling Using TPPTS under CO and H2
The biphasic mixture of a solution of 1.62 mmol of
Co2(CO)8 in 55 mL of C9 OXO-product and an aqueous
phase containing 4.6 mmol of TPPTS in 10 mL of water was
heated under 100 bar of CO/H2 (1:1) at 75 °C for 2 h. A
sample taken from the organic phase showed 138 ppm cobalt
(Table 1, entry 1). When the pressure was decreased from 100
product quality and process simplicity. We have investigated
the removal of cobalt with water-soluble phosphines in
commercial C9 OXO-product, which is a mixture of C8-alkanes
and branched olefins (10%), C9-aldehydes, C9-alcohols, and C9-
formate esters (53%), C9-ethers (1%), ether alcohols (3%), C9-
acetals (31%), and other heavies (2%).37 While the total cobalt
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Table 1. Cobalt Removal from the Organic Phase at 75 °C
water
(mL)
[Co]total
(mol/L)
[Ligand]total
(mol/L)
[Co]organic phase at 100 bar
(ppm)
[Co]organic phase at 10 bar
(ppm)
entry
organic phase/mL
C9 OXO-product/55
1
2
3
10
10
10
0.05
0.05
0.025
TPPTS/0.07
TPPTS/0.14
TPPTS/0.07
138
111
37
70
54
19
C9 OXO-product/55
C9 OXO-product/45 + 10 mL n-
hexane
4
5
6
7
C9 OXO-product/55
C9 OXO-product/55
C9 OXO-product/55
C9 OXO-product/55
5
5
5
5
0.025
0.025
0.025
0.025
TPPTS/0.07
109
107
90
45
43
35
6
CpDPPDS/0.07
BuDPPDS/0.07
Me2MPPMS/0.07
8
to 10 bar of CO/H2 (1:1) at 75 °C, the cobalt concentration
decreased in the organic phase to 70 ppm, as expected.
By increasing the total TPPTS concentration in the reactor
from 0.07 mol/L to 0.014 mol/L, the residual cobalt
concentrations decreased to 111 and 54 ppm cobalt in the
organic phase under 100 and 10 bar of CO/H2 (1:1) at 75 °C,
respectively (Table 1, entry 2). When the polarity of the
organic phase was decreased by the addition of n-hexane (10
mL) to the C9 OXO-product (45 mL), the residual cobalt
concentrations decreased significantly to 37 and 19 ppm in the
organic phase under 100 and 10 bar of CO/H2 (1:1) at 75 °C,
respectively (Table 1, entry 3).
Next, we lowered the total cobalt concentration from 0.05
mol/L to 0.025 mol/L and decreased the volume of the
aqueous phase from 10 mL to 5 mL. The residual cobalt
concentrations were 109 and 45 ppm in the organic phase
under 100 and 10 bar of CO/H2 (1:1) at 75 °C, respectively
(Table 1, entry 4). This is similar to the results obtained in the
presence 0.05 mol/L total cobalt concentration, indicating that
the residual cobalt concentration in organic phase primarily
depends on the Co/TPPTS ratio.
It should be emphasized that the removal of various cobalt
species from the organic phase is the result of the substitution
of their carbonyl ligands by water-soluble phosphines. The
effectiveness of this step will depend on the basicity and the size
of the phosphine.30 The use of much more basic phosphines
that have a small cone angle should result in even lower cobalt
levels. The basicity of a phosphine with respect to TPPTS can
be simply increased by the replacement of one or two of the m-
sulfonatophenyl groups with one or two alkyl substituents.38
While the incorporation of appropriate alkyl substituent(s) can
result in optimal basicity and steric property, the remaining m-
sulfonatophenyl group can ensure good solubility in protic
media.38 Consequently, the sodium salts of cyclopentylbis(m-
sulfonatophenyl)phosphine {C5H9P(C6H4-m-SO3Na)2 or
CpDPPDS}, n-butylbis(m-sulfonatophenyl)phosphine {n-BuP-
(C6H4-m-SO3Na)2 or BuDPPDS}, and dimethyl(m-
sulfonatophenyl)phosphine {(CH3)2P(C6H4-m-SO3Na) or
Me2MPPMS} ligands were investigated for the removal of
cobalt from C9 OXO-product. There was no significant
difference between the final cobalt concentration levels by
using the TPPTS (45 ppm)- and the CpDPPDS (43 ppm)-
modified catalyst system (Table 1, entries 4 and 5). Although
there is a difference between their electronic parameters (χTPPTS
= 15.3 and χCpDPPDS = 11.3), their steric properties are similar
(θTPPTS = 173° and θCpDPPDS = 172°),38 which could have
influenced the equilibria between various cobalt carbonyl- and
phosphine-substituted species. The electronic parameter of
BuDPPDS (χBuDPPDS = 12.5) is similar to both TPPTS and
CpDPPDS, but the cone angle is smaller (θBuDPPDS = 153°),
which resulted in better cobalt removal, indicating the beneficial
role of sterics in this reaction. Finally, by using the more
electron-donating and less bulky Me2MPPMS (χ = 10.8,
θMe2MPPMS = 140°) the final cobalt concentration can be
reduced to 6.0 ppm in the organic phase.
CONCLUSIONS
■
It was demonstrated that Co2(CO)8 and HCo(CO)4 can be
removed from the hydroformylation product phase including
the commercial C9 OXO-product by using a sulfonated water-
soluble tertiary phosphine ligand under biphasic conditions.
The efficiency of the separation is strongly affected by the
electronic and steric properties of the phosphine ligands, the
Co/phosphine ratio, the polarity of the organic phase, and the
total syngas pressure. Depending on the nature of the
phosphines, 6−70 ppm cobalt concentrations could be achieved
in the organic phase under 10 bar of CO:H2 (1:1) at 75 °C. It
was confirmed that the order of the addition of cobalt and
olefin has no effect on the product formation in cobalt-
catalyzed hydroformylation. The formation of several cobalt
carbonyls including Co2 (CO)6 (TPPTS)2 , HCo-
(CO)3(TPPTS), HCo(CO)2(TPPTS)2, and [Co-
(CO)3(TPPTS)2]+[Co(CO)4]− was observed by investigating
the reaction of Co2(CO)8 and HCo(CO)4 with TPPTS using
in situ IR and NMR spectroscopy.
EXPERIMENTAL SECTION
■
Hexane, methanol, and hydrochloric acid were obtained from Molar
Chemicals Ltd., Budapest, Hungary. The octane and octene-1 were
purchased from Aldrich Chemical and used as received without further
purification. Co2(CO)8 was obtained from Strem Chemical Co. and
purified by recrystallization from deoxygenated n-hexane under carbon
monoxide atmosphere. 31P{1H} NMR spectra were recorded on a
Bruker-Avance 250 MHz NMR instrument using H3PO4 as reference.
GC measurements were performed on an HP-5890 GC with an HP-5
capillary column equipped with an FID detector using cyclohexane as
internal standard. GC-MS was performed on an HP-6890 instrument
equipped with 5973 MSD. In situ IR measurements were performed by
using a ReactIR 1000 infrared instrument equipped with a SiComp
probe head (ASI, a Mettler Toledo Company). The AAS measure-
ments were performed on a Perkin-Elmer 310 atomic absorption
spectrometer at an atomization temperature of 2500 °C and at a
detection wavelength of 240.7 nm.
35a
TPPTS39 and HCo(CO)4 were prepared by published methods.
The disodium salt of butylbis(m-sulfonatophenyl)phosphine (Bu-
DPPDS), the sodium salt of dimethyl(m-sulfonatophenyl)phosphine
(Me2MPPMS), and the disodium salt of cyclopentylbis(m-
sulfonatophenyl)phosphine (Cp-DPPDS) were prepared according
to our previous work11 (detailed experimental procedure and
characterization of the disodium salt of cyclopentylbis(m-
sulfonatophenyl)phosphine in ref 38). All manipulations were
performed by using standard Schlenk techniques.
Hydroformylation of Octene-1 in Organic/Aqueous Biphasic
Conditions with in Situ IR Measurement. The two-phase
F
dx.doi.org/10.1021/om400579f | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
hydroformylation reaction consisting of 1.04 g (2.9 mmol) of
Co2(CO)8 in 45 mL of n-hexane and 3.3 g (5.8 mmol) of TPPTS
in 10 mL of water was placed in a 250 mL high-pressure reactor,
equipped with a high-pressure IR probe attached to a ReactIR 1000
infrared instrument. The reaction mixture was pressurized with CO/
H2 (1:1) to reach 100 bar at 100 °C. After 2 h 10 mL of 1-octene was
added to the reaction mixture. The reaction mixture was cooled to
room temperature after 3 h. The two phases were separated and
analyzed by GC and NMR. The aqueous phase was used as catalyst
phase without any further modification in the next investigation of
hydroformylation of 20 mL (128 mmol) of 1-octene in 30 mL of n-
hexane (100 bar of CO/H2).
General Procedure for Cobalt Removal from C9 OXO-
Product under Biphasic Conditions. In a typical experiment 1.6
mmol of Co2(CO)8 was dissolved in 55 mL of C9 OXO-product
under nitrogen at room temperature. The solution was combined with
5 mL of an aqueous solution of 4.9 mmol of TPPTS followed by
transfer with vacuum into the 100 mL stainless steel reactor equipped
with a Parr 4870 temperature controller. The water was treated and
has been stored under nitrogen, preventing a solution of CO2 and
oxygen. The reaction mixture was pressurized with CO/H2 (1:1) to
reach 100 bar at 100 °C. The reaction mixture was cooled to the
desired temperature (e.g., 75 °C) after 2 h stirring under 100 bar of
syngas. A sample was taken to determine the initial Co concentration
in the organic phase. Then the pressure was decreased to 10 bar. The
stirring was stopped for 2 min to allow phase separation in the reactor,
and a 50 μL sample was taken from the lower aqueous phase of the
reaction mixture by a deep leg. The sample was diluted to 10 mL with
MeOH/HCl (9:1). The parallel calibration of AAS was performed by
using solutions of either Co(NO3)2 or Co2(CO)8 in MeOH/HCl in
the concentration range 12.5−50 ppb. A 20 μL sample was used for
the AAS measurement.
(8) Wasserscheid, P.; Keim, W. Angew. Chem., Int. Ed. 2000, 39, 3772.
(9) (a) Leitner, W. Acc. Chem. Res. 2002, 35, 746. (b) Koch, D.;
Leitner, W. J. Am. Chem. Soc. 1998, 120, 1398.
(10) Cole-Hamilton, D. J. Science 2003, 299, 1702.
(11) Mika, L. T.; Orha, L.; Farkas, N.; Horvat
2009, 28, 1593.
́
h, I. T. Organometallics
(12) Kuntz, E. G. CHEMTECH 1987, 17, 570.
(13) Cornils, B.; Wiebus, E. CHEMTECH 1995, 25, 33.
(14) Horvat
(15) Horvat
́
h, I. T. Catal. Lett. 1990, 6, 43.
h, I. T.; Kiss, G.; Stevens, P. A.; Bond, J. E.; Cook, R. A.;
́
́
Mozeleski, E. J.; Rabai, J. J. Am. Chem. Soc. 1998, 120, 3133.
(16) Forster, D. M.; Gudmunsen, D.; Adams, D. J.; Stuart, A. M.;
Hope, E. G.; Cole-Hamilton, D. J.; Schwarz, G. P.; Pogorzelec, P.
Tetrahedron 2002, 58, 3901.
(17) Keim, W.; Wasserscheid, P. Angew. Chem., Int. Ed. 2000, 39,
3772.
(18) Parshall, G. W. J. Am. Chem. Soc. 1972, 94, 8716.
(19) Chauvin, Y.; Mussmann, L.; Olivier, H. Angew. Chem., Int. Ed.
1995, 34, 2698.
(20) Brasse, C. C.; Englert, U.; Salzer, A.; Waffenschmidt, H.;
Wasserscheid, P. Organometallics 2000, 19, 3818.
(21) Mehnert, C. P.; Cook, R. A.; Dispenziere, N. C.; Mozeleski, E. J.
Polyhedron 2004, 23, 2679.
(22) Pino, P.; Major, A.; Spindler, F.; Tannenbaum, R.; Bor, G.;
́
Horvath, I. T. J. Organomet. Chem. 1991, 417, 65.
(23) Nienburg, H. J.; Kummer, R.; Hohenschutz, H.; Strohmeyer, M.
Ger. Patent DE2206252, 1973.
(24) (a) Lemke, H. Hydrocarbon Process., Int. Ed. 1966, 45, 148.
(b) van Driessche, E.; van Vliet, A.; Caers, R. F.; Beckers, H.; Garton,
R.; Da Cruz, B.; Lepagnol, M.; Kooke, E. Patent Appl. WO2008/
122526A1, 2008.
(25) Tucci, E. Ind. Eng. Chem. Prod. Res. Dev. 1970, 9, 516.
(26) Tucci, E. R. Ind. Eng. Chem. Prod. Res. Dev. 1969, 8, 215.
(27) Tucci, E. Ind. Eng. Chem. Prod. Res. Dev. 1968, 7, 32.
(28) Tucci, E. Ind. Eng. Chem. Prod. Res. Dev. 1968, 7, 125.
(29) Bartik, T.; Bartik, B.; Hanson, B. E. J. Mol. Catal. 1993, 85, 121.
(30) Hebrand, F.; Kalck, P. Chem. Rev. 2009, 109, 4272.
AUTHOR INFORMATION
Corresponding Author
*E-mail: istvan.t.horvath@cityu.edu.hk.
■
Notes
(31) Guo, I.; Hanson, B. E.; Tot
Chem. 1991, 403, 221.
(32) Horvath, I. T.; Rab
1995.
́
h, I.; Davis, M. E. J. Organomet.
The authors declare no competing financial interest.
́
́
ai, J. (ExxonMobil) US Patent 5 463 082,
ACKNOWLEDGMENTS
■
This work was supported by ExxonMobil Chemicals Europe
and ExxonMobil Research and Engineering Company. The
donation of the ReactIR 1000 instrument by Applied Systems
Inc, a Mettler-Toledo Company, is greatly appreciated.
(33) Bartik, T.; Bartik, B.; Whitmire, K. H.; Guo, I. Inorg. Chem.
1993, 32, 5833.
(34) Sielcken, O. E.; Haasen, N. F. (DSM) Patent Appl. WO
9414747, 1994
(35) (a) Mika, L. T.; Tuba, R. T.; Pitter, S.; Tot
Organometallics 2011, 30, 4751. (b) Pusztai, Z.; Vlad
Horvath, I. T.; Laas, H. J.; Halpaap, R.; Richter, F. U. Angew. Chem.,
Int. Ed. 2006, 45, 107. (c) Tuba, R.; Mika, L. T.; Bodor, A.; Pusztai, A.;
Toth, I.; Horvath, I. T. Organometallics 2003, 22, 1582. (d) Csihony,
S.; Mika, L. T.; Vlad, G.; Barta, K.; Mehnert, C. P.; Horvath, I. T.
Collect. Czech. Chem. Commun. 2007, 72, 1094.
(36) Bartik, T.; Krummung, T.; Happ, B.; Sieker, A.; Marko,
́
h, I.; Horvat
́
h, I. T.
́
, G.; Bodor, A.;
REFERENCES
(1) Roelen, O. Ger. Patent DE849548, 1938
(2) Beller, M.; Cornils, B.; Frohning, C. D.; Kohlpaintner, C. J. Mol.
Catal. A 1995, 104, 17.
■
́
́
́
́
́
(3) Kohlpaintner, C. W. Hydroformylation − Industrial. In
́
Encyclopedia of Catalysis; Horvath, I. T., Ed.; Wiley: New York,
́
L.;
́
yi, G. Catal. Lett. 1993, 19, 383.
̈
2003; Vol. 3, p 787.
Boese, R.; Ugo, R.; Zucchi, C.; Pal
(4) (a) Slaugh, L. H.; Mullineaux, R. D. J. Organomet. Chem. 1968,
13, 469. (b) Slaugh, L. H.; Hill, P.; Mullineaux, R. D. (Shell) US
Patent 3239569, 1966. (c) Slaugh, L. H.; Hill, P.; Mullineaux, R. D.
(Shell) US Patent 3239570, 1966. (d) Slaugh, L. H.; Hill, P.;
Mullineaux, R. D. US Patent 3239571. (e) Slaugh, L. H.; Hill, P.;
Mullineaux, R. D. (Shell) US Patent 3239566, 1966.
(37) Garton, R. D.; van Driessche, E. D.; Reed, C. W. (ExxonMobil)
Patent Appl. WO2010022881, 2010.
(38) Tukacs, J. M.; Kiral
́ ́
y, D.; Stradi, A.; Novodarszki, G.; Eke, Z.;
Dibo, G.; Kegl, T.; Mika, L. T. Green Chem. 2012, 14, 2057.
́
́
(39) Herrmann, W. A.; Kohlpainter, C. W. Inorg. Synth. 1998, 32, 8.
(5) Weissermel, K.; Arpe, H.-J. Industrial Organic Chemistry; VCH:
Weinheim, Germany, 1988.
(6) (a) Joo,
́
F. In Aqueous Organometallic Catalysis, Catalysis by Metal
Complexes; James, B. R.; van Leeuwen, P. W. N. M., Eds.; Kluwer
́
́ ́
Academic Pub.: Dordrecht, 2001; Vol 23, p 152. (b) Joo, F.; Katho, A.
J. Mol. Catal. A: Chem. 1997, 116, 3. (c) Cornils, B.; Herrmann, W. A.,
Eds. Aqueous-Phase Organometallic Catalysis, 2nd ed.; Wiley-VCH:
Weinheim, 2004.
(7) (a) Horvat
́ ́
h, I. T. Acc. Chem. Res. 1998, 31, 641. (b) Horvath, I.
T.; Rabai, J. Science 1994, 266, 72.
́
G
dx.doi.org/10.1021/om400579f | Organometallics XXXX, XXX, XXX−XXX