J. Am. Chem. Soc. 1997, 119, 893-895
893
A Novel Water-Soluble Rhodium-Poly(enolate-co-vinyl
alcohol-co-vinyl acetate) Catalyst for the Hydroformylation of
Olefins
Jinhua Chen and Howard Alper*
Contribution from the Department of Chemistry, UniVersity of Ottawa, 10 Marie Curie PriVate,
Ottawa, Ontario, Canada K1N 6N5
ReceiVed July 11, 1996X
Abstract: The water-soluble polymer, poly(enolate-co-vinyl alcohol-co-vinyl acetate) (PEVV), prepared by controlled
oxidation of poly(vinyl alcohol-co-vinyl acetate), is a valuable ligand for the rhodium biphasic catalytic
hydroformylation of olefins. The average turnover frequency for the catalytic hydroformylation of 1-octene was
5.46 × 10-5 kmol (kg(Rh)s)-1 at 90 °C, and that of 1-dodecene was 2.36 × 10-4 kmol (kg(Rh) s)-1 at 60 °C.
Selective hydroformylation of styrene and its derivatives gave up to 97% of branched-chain aldehyde using Rh-
PEVV under biphasic reaction conditions but at low conversions.
Homogeneous catalysis has many advantages over hetero-
geneous catalysis.1 However, the recovery of homogeneous
catalysts from high-boiling products is difficult. The idea of
biphasic catalysis, which simplifies the separation of catalysts
from products by decantation, has attracted great attention in
recent years.2-6 Biphasic catalysis relies on the transfer of
organic substrates into the aqueous phase containing the catalyst.
The reaction rate could be reduced to such an extent that it
becomes unacceptable when the solubility of the substrates in
the aqueous phase is low, preventing adequate transfer of organic
substrates into the aqueous catalytic phase or at the phase
boundary.3 Therefore, studies have focused on improving the
affinities between the two phases.2,3 The addition of cosolvents,
such as alcoholic solvents, surfactants, and modified cyclodex-
trins, to enhance mutual solubility or mobility of the components
across the phase boundary can increase the reaction rate by more
than 10 times.2-5 Addition of water-soluble organic ligands,
such as P(Ph(SO3))3, and inorganic salts to increase the
concentration of the catalyst to the interface enhances the
catalytic reactivity as well.2-5 Extensive studies have been
undertaken to improve the ligands for these reactions. One
example is the use of a catalyst bearing partially fluorinated
“ponytail” ligands bound via phosphorus in a fluorous biphasic
system.7 The fluorous biphasic system becomes a one-phase
system by increasing the temperature.7 A similar idea for “smart
ligands” has been reported for biphasic hydrogenation.8 Re-
cently, ligands with surfactant structures, such as Ph2P(CH2)2-
C(O)NHC(CH3)2CH2SO3Li, P[(CH2)nC6H4SO3Na]3, P[C6H4-
(CH2)nC6H4SO3Na]3, (menthyl)P[(CH2)8C6H4-p-SO3Na]2, and
Ph2P(CH2)nSO3Na, have been used in catalytic hydroformyla-
tion.9 These ligands are superior to P(C6H4-p-SO3Na)3 (TPPTS)
for the catalytic hydroformylation of olefins.9 As the structure
of the surfactant ligands implies, the lipophilic phosphine ligand
coordinated to the catalytic active center is concentrated close
to the interface while the hydrophilic part of the component
aids in the solubilization of the catalyst into the aqueous solution.
This concept encouraged us to develop a water-soluble, polymer-
anchored, rhodium catalyst having a structure of a lipophilic
rhodium center and a hydrophilic long chain for the catalytic
hydroformylation of olefins. Such a catalyst, with the noted
features, could offer significant advantages over conventional
ligands in terms of regioselectivity, reactivity, and separation
of reaction mixtures. The chemical modifications of polymers
have been used to prepare polymers with various functional
groups.10 Therefore, a polymer composed of both lipophilic
and hydrophilic structures, such as lipophilic functionality
grafted polyvinyl alcohol (PVA), may be ideal for such a
purpose.
The controlled oxidation of PVA using sodium hypochlorite
has been reported to afford lipophilic poly(methylene ketone)
(PMK).11 Under basic conditions, tautomerization of PMK gave
the enolate which chelated metal ions such as nickel.11 Thus,
oxidation of PVA affords poly(vinyl alcohol-co-methylene
ketone) composed of both lipophilic and hydrophilic components
of methylene ketone and vinyl alcohol. The strong chelating
ability of the PMK enolate results in a rhodium complex which
can serve as a biphasic hydroformylation catalyst precursor,
while the unoxidized hydroxyl groups promote the dissolution
of the catalyst in aqueous solution.
Results and Discussion
(1) Preparation of Rhodium-Poly(enolate-co-vinyl alcohol-
co-vinyl acetate) (Rh-PEVV) Complexes. Oxidation of
secondary alcohols with NaOCl affords ketones in high yields.12
X Abstract published in AdVance ACS Abstracts, November 15, 1996.
(1) Parshall, G. W.; Ittel, S. D. Homogeneous Catalysis, 2nd ed.; John
Wiley: New York, 1992.
(2) Chaudhari, R. V.; Bhanage, B. M.; Deshpande, R. M.; Delmas, H.
Nature 1995, 373, 501.
(3) Cornils, B. Angew. Chem., Int. Ed. Engl. 1995, 34, 1575.
(4) Monteil, F.; Queau, R.; Kalck, P. J. Organomet. Chem. 1994, 480,
177.
(5) (a) Beller, M.; Cornils, B.; Frohning, C. D.; Kohlpaintner, C. W. J.
Mol. Catal. 1995, 104, 17 and references therein. (b) Cornils, B.; Kuntz,
E. G. J. Organomet. Chem. 1995, 502, 177.
(9) (a) Fremy, G.; Castanet, Y.; Grzybek, R.; Monflier, E.; Mortreux,
A.; Trzeciak, A. M.; Ziolkowski, J. J. J. Organomet. Chem. 1995, 505, 11.
(b) Burtik, T.; Bartik, B.; Hanson, B. E. J. Mol. Catal. 1994, 88, 43 (c)
Fell, B.; Papadogianakis, G. J. Prakt. Chem. 1994, 7, 591. (d) Abatjoglou,
A. G. U.S. Pat. 5180854, 1993. (e) Bartik, T.; Ding, H.; Bartik, B.; Hanson,
B. E. J. Mol. Catal. 1995, 98, 117.
(10) MacGrath, M. D.; Sall, E. D.; Tremont, S. J. Chem. ReV. 1995, 95,
381 and references therein.
(6) Kalck, P.; Monteil, F. AdV. Organomet. Chem. 1992, 34, 219.
(7) Horvath, I. T.; Rabai, J. Science 1994, 266, 72.
(8) Bergbreiter, D. E.; Zhang, L.; Mariagnanam, V. M. J. Am. Chem.
Soc. 1993, 115, 9295.
(11) Huang, S. J.; Wang, I.-F.; Quinga, E. In Modification of Polymers;
Canahes, C. E., Moore, J. E., Jr., Eds.; Plenum Press: New York, 1983; p
75.
(12) Nwaukwa, S. O.; Keehn, P. M. Tetrahedron Lett. 1982, 23, 35.
S0002-7863(96)02387-6 CCC: $14.00 © 1997 American Chemical Society