Synthesis and characterization of a new enantiopure hydroxylated phosphine, its rhodium(I) and (III) complexes and their performance in catalytic carbonylation

Article abstract of DOI:10.1016/S0957-4166(03)00488-9

The enantiomerically pure hydroxylated phosphine (1S,2S,5R)-1-diphenylphosphinomethyl-2-isopropyl-5-methyl-cyclohexanol 3 was prepared in a two-step stereoselective process from the commercially available and low cost (-)-menthone. Reaction of this new li

Full text of DOI:10.1016/S0957-4166(03)00488-9

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 14 (2003) 2529–2538
Synthesis and characterization of a new enantiopure
hydroxylated phosphine, its rhodium(I) and (III) complexes and
their performance in catalytic carbonylation
Josep Duran,a Daniel Oliver,a Alfonso Polo,a,* Julio Real,b Jordi Benet-Buchholzc and
Xavier Fontrodonac
aDepartament de Qu´ımica, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain
bDepartament de Qu´ımica, Universitat Auto`noma de Barcelona, 08193 Bellaterra, Spain
cBayer AG, Bayer Industry Services, Analytics X-ray Laboratory, Geb. Q18, Raum 490, D-51368 Leverkusen, Germany
Received 30 March 2003; accepted 29 May 2003
Abstract—The enantiomerically pure hydroxylated phosphine (1S,2S,5R)-1-diphenylphosphinomethyl-2-isopropyl-5-methyl-cyclo-
hexanol 3 was prepared in a two-step stereoselective process from the commercially available and low cost (−)-menthone. Reaction
of this new ligand with the appropriate rhodium precursor gave the respective Rh(I) and Rh(III) complexes. For rhodium(I), the
binuclear complex trans-P,P-bis-{m-chlorocarbonyl[(1S,2S,5R)-1-diphenylphosphinomethyl-2-isopropyl-5-methyl-cyclohexanol-
P]rhodium(I)} 6 was obtained by reaction with [Rh(m-Cl)(CO)2]2. For Rh(III), two isomeric edge-sharing bioctahedral (ESBO)
complexes,
trans-O,O-trans-P,P-bis{(OC-6-32)-m-chlorodichloro[(1S,2S,5R)-1-diphenylphosphinomethyl-2-isopropyl-5-methyl-
cyclohexanol-O,P]rhodium(III)} 7a and trans-O,O-cis-P,P-bis{(OC-6-32)-m-chlorodichloro[(1S,2S,5R)-1-diphenylphosphi-
nomethyl-2-isopropyl-5-methyl-cyclohexanol-O,P]rhodium(III)} 7b, and the partially hydrolyzed product, trans-O,O-cis-P,P-
(OC-6-32)-{m-chloro-m-hydroxo-tetrachlorobis[(1S,2S,5R)-1-diphenylphosphinomethyl-2-isopropyl-5-methyl-cyclohexanol-O,P]-
dirhodium(III)}8 were characterized in solid state by single-crystal X-ray diffraction analysis. The O-axial-P-equatorial trans-O,O
arrangements observed in compounds 7a,b and 8 are preferred over the more common O-equatorial-P-equatorial structure,
presumably due to the stereo-electronic coordination preferences of the chiral hydroxylated phosphine. To the best of our
knowledge, the ligand arrangement observed in 7b and 8 is unique among ESBO complexes. The rhodium(I) complex 6 is active
as a catalyst precursor in the hydroformylation of styrene, yielding initial turnover frequencies up to 440 h−1 and selectivities up
to 74% in the branched aldehyde. Unfortunately, no enantiomeric excesses have been observed within experimental error.
© 2003 Elsevier Ltd. All rights reserved.
1. Introduction
introduction of hydroxyl groups increases the
hydrophilicity and allows to obtain water-soluble
ligands.7
Although chelating diphosphines are the prevalent chi-
ral bidentate ligands to achieve catalytic asymmetric
transformations, the ever increasing need for new cata-
lytic systems has led to the development of mixed-
donor ligands such as (P,O), (P,N) and (P,S) donors.1
Hydroxylated phosphines, a class of hemilabile (P,O)-
mixed-donor ligands, have attracted considerable inter-
est in recent years mainly because of their application
in homogeneous catalytic reactions,1–5 with the excep-
tion of catalytic carbonylation for which few studies
have been described.6 It is also of interest that the
Enantiomerically pure hydroxylated phosphines have
been obtained from diastereoselective multi-step synthe-
sis starting from simple aldehydes,8,9 by resolution of
the racemate10,11 and, more efficiently, by nucleophilic
ring-opening of chiral epoxides with phosphides, as this
reaction
shows
high
regioselectivity
and
stereoselectivity.12,13
Using the epoxide-opening reaction we have developed
a two-step stereoselective synthesis for a new enantio-
pure hydroxylated phosphine derived from the commer-
cially available, low cost (−)-menthone. Herein we
report the synthesis and characterization of this new
* Corresponding author. Fax: +34 (9)72418150; e-mail: alfons.polo@
udg.es
0957-4166/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0957-4166(03)00488-9

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J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
Scheme 1. Synthetic routes for the new enantiopure hydroxylated phosphine 3. Reagents and conditions: (a) (CH3)3SOI/NaH,
DMSO, rt; (b) KPPh2, THF, rt; (c) CH3)3SI/NaH, DMSO, rt; (d) (C6H5)3PCH3Br/NaNH2, THF, 0°C; (e) m-CPBA/NaHCO3,
CH2Cl2/H2O, rt.
enantiomerically pure hydroxylated phosphine, the
study of the stereoelectronic effects of this ligand in its
rhodium(I) and rhodium(III) coordination complexes,
and the performance of the Rh(I) complex as a catalyst
precursor in the hydroformylation of styrene.
and 4 was obtained by epoxidation of the olefin 5,
conveniently prepared by a Wittig reaction on (−)-men-
thone 1.
Compounds 2–5 were characterized by NMR spec-
troscopy. In compound 3, the methylenic protons near
2
the phosphine group are diastereotopic, showing a J
2. Synthesis of (1S,2S,5R)-1-diphenylphosphinomethyl-
coupling constant with the phosphorus atom, as it can
be seen in the 1H and 1H{31P} NMR spectra (Fig. 1). In
the 13C{1H} NMR spectrum, the four aliphatic carbons
close to the phosphine group (C1, C2, C3, C7) appear as
doublets by coupling to the phosphorus atom. In the
31P{1H} NMR spectrum, compound 3 shows a single
resonance at −24.87 ppm.
2-isopropyl-5-methyl-cyclohexanol, 3
Ligand 3 was prepared from commercially available
(−)-menthone 1 in a two-step synthesis according to
Scheme 1. In the first step, reaction of 1 with dimethyl-
sulfoxonium methylide, prepared in situ upon treatment
of trimethylsulfoxonium iodide with sodium hydride,
gave
the
(1S,4S,7R)-4-isopropyl-7-methyl-1-oxa-
spiro[2.5]octane 2 in good yield (80%). Epoxide 2 pre-
sents the transferred methylene in an equatorial
position, according to previously reported results using
other cyclohexanones.14 Treatment of oxirane 2 with 1
equiv. of potassium diphenylphosphide in THF gave
the (1S,2S,5R)-1-diphenylphosphinomethyl-2-isopro-
pyl-5-methyl-cyclohexanol 3, in 76% yield. The
attempts to obtain the epoxide isomer 4 via the reaction
of (−)-menthone 1 with dimethylsulfonium methylide
(Scheme 1), in which the insertion of methylene into the
CO double bond is proposed to give preferentially an
axial carbonꢀcarbon bond,14 gave a mixture of the two
diastereomeric oxiranes, with oxirane 2 being the major
product, surprisingly. It seems that the diastereoselec-
tivity of the reaction is controlled by the configuration
of the tertiary carbon near the carbonyl group. Alterna-
tively, an almost equimolecular mixture of oxiranes 2
Figure 1. 1H (a) and 1H{31P}, (b) NMR spectra of chiral
hydroxylated phosphine 3 and its rhodium(I) complex 6.

J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
2531
3. Coordination of (1S,2S,5R)-1-diphenylphosphino-
of time, resulted in the oxidation of the metal, loss of
CO and crystallization of the edge-sharing bioctahedral
(ESBO) Rh(III) complex [Rh(m-Cl)Cl2(3)]2 7 with the
P,O-chelated chiral hydroxylated phosphine. This com-
pound can also be obtained, in a 38% yield, by addition
of 1 equiv. of ligand 3 to an ethanol solution of
RhCl3·xH2O at room temperature. In comparison with
the Rh(I) complex 6, the non requirement for p-accep-
tor ligands to stabilize the higher oxidation state of the
metal in 7 promotes the coordination of the hydroxyl
group in this case.
methyl-2-isopropyl-5-methyl-cyclohexanol 3 to Rh(I)
Addition of 1 equiv. of ligand 3 to a solution of
[Rh(m-Cl)(CO)2]2 at room temperature yields a rhodium
complex 6 carrying the enantiopure hydroxylated phos-
phine. The spectroscopic characteristics of complex 6
are in agreement with a dimeric rhodium(I) structure in
which only the phosphine group is coordinated to the
metal (Scheme 2). The IR spectrum of complex 6 shows
an intense w(CO) absorption at 1975 cm−1, in agreement
with terminal trans-coordinated carbonyls (Scheme 2),
and a sharp w(OH) at 3546 cm−1 showing that the
hydrogen of the hydroxyl group remains in the ligand.
Complex 7 is not soluble enough to obtain quality
measurements of its 13C{1H} NMR. Furthermore, its
1H NMR spectrum is too complex to extract useful
structural information. However, freshly prepared
CD2Cl2 solutions of the product show, mainly, two
resonances, at lP 47.68 (1JPꢀRh=110.8 Hz) and 38.16
ppm (1JPꢀRh=123.8 Hz) in ca. 1:1 intensity ratio, in the
31P{1H} spectrum, suggesting the existence in solution
of the two isomeric complexes 7a and 7b (Scheme 3)
that have been characterized in solid state (vide infra).
1
In the H NMR spectrum, the methylenic protons near
the phosphine group are also diastereotopic (Fig. 1).
One of them is a doublet of doublets owing to coupling
to both the geminal proton and the phosphorus center.
The second resonance consists of a triplet of doublets,
arising from two similar coupling constants to the
geminal hydrogen and to the phosphorus atom, and a
third smaller coupling constant. In the 13C{1H} NMR
spectrum, three aliphatic carbons (C1, C3, C7) appear as
doublets by coupling to the phosphorus atom. In the
31P{1H} NMR spectrum, compound 6 shows a doublet
by coupling to rhodium (1JPꢀRh=162.1 Hz) at 57.95
ppm. This coupling constant is in agreement with a
square-planar rhodium(I) complex with a cis geometry
between the higher trans-influence ligand (CO) and the
phosphine group.15
1
The JPꢀRh are in agreement with octahedral rhodi-
um(III) complexes with
a
O,P-chelated ligand.15
Although there is not sufficient experimental data to
make a definitive assignment of the phosphorus reso-
1
nances to 7a and 7b, the signal with a smaller JPꢀRh
(110.8 Hz, at 47.68 ppm) could be related to isomer 7b,
since the p-donor ability of a bridging chloride in trans
to both phosphine groups should not be as large as that
of a bridging chloride in trans to a single phosphine 7a.
Aged CD2Cl2 solutions of complex 7 develop a yellow
precipitate, with the 31P{1H} NMR spectrum showing
the disappearance of the signal at 47.68 ppm suggesting
that a fractional crystallization has occurred. Unfortu-
nately, these crystals were not of sufficient quality to
determine their structure in solid state by XRD
methods.
Attempts to obtain Rh(I) P,O-chelated complexes with
the enantiopure hydroxylated phosphine, by substitu-
tion of the chloride ligands by different non-coordinat-
ing anions in the presence of PPh3 or CO have failed.
The greater stabilization of the low oxidation state of
the metal produced by coordination to the highly p-
acceptor ligands, in comparison with the potential sta-
bilization produced by the chelate effect, could be the
cause of the observed results.
After different crystallizations of complex 7, crystals of
three habits could be distinguished under the micro-
scope. Subsequent crystallographic analysis revealed
that they had different unit cell parameters. Three
crystals, one of each type, were subjected to XRD
crystal structure determination (see Section 6). Selected
distances and angles are listed in the captions of Fig-
ures 2, 3 and 4. The crystal structure of 7a·12H2O,
although of somewhat low quality (Fig. 2), revealed an
ESBO rhodium(III) complex with two chlorides in the
bridging positions and the hydroxylated phosphine act-
ing as a chelate ligand with the hydroxyl and phosphine
groups in axial and equatorial positions respectively.
The O-donor groups are mutually in trans positions
across the dimer, and the same arrangement was
observed for the phosphorus atoms resulting in a global
structure of type II (Scheme 4). The molecule is C1
symmetry because the inversion center symmetry is
broken by the menthane cycles, owing to the stereoelec-
tronic preference of the chelate rings to adopt the l
conformation (vide infra). The crystal structure of
7b·12C6H14 (Fig. 3) differs from the previous one in the
4. Coordination of (1S,2S,5R)-1-diphenylphosphino-
methyl-2-isopropyl-5-methyl-cyclohexanol 3 to Rh(III)
Attempts to obtain X-ray quality crystals of complex 6
by recrystallization in CHCl3/hexane for long periods
Scheme 2. Proposed structure for the chiral hydroxylated
phosphine rhodium(I) complex 6.

2532
J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
Scheme 3. Structure of the chiral hydroxylated phosphine rhodium(III) complexes (7a, 7b and 8) characterized in solid state.
relative positions of the phosphine groups, which in this
case are in cis, adopting a structure of type V and
pseudo C2 symmetry (Scheme 4). To the best of our
knowledge, this ligand arrangement is unique among
comparable edge-sharing bioctahedral complexes.
Finally, the crystal structure of 8 (Fig. 3) revealed, as in
the case of 7b, an ESBO rhodium(III) complex with the
unusual geometry type V but where a bridging chloride
has been replaced by a bridging hydroxo ligand. Com-
plex 8 is most likely a product of partial hydrolysis of
7b in the lengthy crystallization process, but the factors
that determine the formation of this product, and not
other, are still under study as hydrolysis products may
still be relevant in water-containing catalytic processes
catalyzed by rhodium complexes (e.g. biphasic
catalysis).
phosphinothioether complex [Rh(m-I)I2(o-MeSC6H4-
18
,
PPh2)]2 (2.27 A) than to those in the above-mentioned
chloro-bridged diphosphine and monophosphine com-
16,17
,
plexes (2.38 and 2.39 A, respectively).
Finally, the
Rh-Cl(bridging) distances are longer than the Rh-
Cl(terminal) distances and are consistent with the trans
influences of their respective trans ligands.
These ESBO rhodium(III) complexes of type [RhX3L]2
(L=bidentate ligand) are of interest from several differ-
ent perspectives, including stereoisomerism19 and stereo
and regiospecificity in ligand substitution reactions.20 In
this class of compounds, the bridging positions are
always occupied by the X ligands and the distribution
of the eight terminal positions can lead, in principle, to
numerous stereoisomers. However, the few examples
that have been described show structures of type I, for
the bridging diphosphine Ph2PCH2PPh2,16 and II, for
the chelating phosphinothioether o-MeSC6H4PPh2.18 In
ESBO complexes of other transition metals (groups
IV–VII) with chelating diphosphines the equatorial–
equatorial arrangement (type III) is normally preferred,
rather than axial–equatorial structures (types II and
IV), since close contacts of axial phosphine groups are
thus avoided.21–32 Only for bridging-chelating
tetraphosphines33,34 and for less hindered bidentate lig-
ands, such as dithioethers, axial-equatorial arrange-
ments (type IV or V, respectively) have been regularly
observed.35,36
In structures 7a,b and 8 the geometry about each
rhodium(III) atom is approximately octahedral, how-
ever, the planarity of the Rh2Cl2 core is slightly dis-
torted in 7a,b, owing most probably to packing forces
in the solid state. For complexes 7a,b the RhꢀRh
,
distances (3.553(3) and 3.584(1) A, respectively) are
greater than in the chloro-bridged diphosphine complex
16
,
(3.43 A), as it could be
[Rh(m-Cl)Cl2(dppm)]2
expected, but shorter than in the monophosphine com-
plex [Rh(m-Cl)Cl2(PEt3)2]2 (3.74 A) with an axial–
17
,
axial–equatorial–equatorial arrangement of type VI
(Scheme 4). This suggests that the less hindered O-
donor ligand allows a greater approach of the two
octahedral units, compared to a phosphine group. In
complex 8, with a smaller bridging ligand, the Rh—Rh
In our case, the hydroxylated phosphine 6 cannot act as
a bridging ligand (type I), since the observed bite angle
(ca. 84°) is incompatible with the RhꢀRh distances, and
compounds 7a,b and 8 prefer the O-axial-P-equatorial
,
distance is consequently shorter (3.28 A). Owing to the
,
chelating effect, the RhꢀP distances in 7a,b (2.23 A) and
,
8 (2.22 A) are more similar to those in the chelating

J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
2533
Figure 2. ORTEP plot (50%) of complex 7a, hydrogen atoms
and aryl rings are omitted to fully appreciate the geometry of
Figure 3. ORTEP plot (50%) of complex 7b, hydrogen atoms
and aryl rings are omitted to fully appreciate the geometry of
,
the complex. Selected distances (A) and angles (°): P1ꢀRh1
2.252(8), O1ꢀRh1 2.13(17), Rh1ꢀCl4 2.288(7), Rh1ꢀCl3
2.324(10), Rh1ꢀCl2 2.356(9), Rh1ꢀCl1 2.513(8), Cl1ꢀRh2
2.344(9), Rh2ꢀO2 2.081(17), Rh2ꢀP2 2.206(11), Rh2ꢀCl5
2.299(11), Rh2ꢀCl6 2.311(7), Rh2ꢀCl2 2.455(8), O1ꢀRh1ꢀP1
83.5(5), O1ꢀRh1ꢀCl4 178.6(8), P1ꢀRh1ꢀCl4 96.6(3),
O1ꢀRh1ꢀCl3 91.0(7), P1ꢀRh1ꢀCl3 93.4(4), Cl4ꢀRh1ꢀCl3
,
the complex. Selected distances (A) and angles (°): Rh1ꢀO1
2.084(5), Rh1ꢀP1 2.239(2), Rh1ꢀCl4 2.285(2), Rh1ꢀCl3
2.297(2), Rh1ꢀCl2 2.357(2), Rh1ꢀCl1 2.481(2), Cl2ꢀRh2
2.343(2), Rh2ꢀO2 2.106(5), Rh2ꢀP2 2.230(2), Rh2ꢀCl6
2.296(2), Rh2ꢀCl5 2.302(2), Rh2ꢀCl1 2.475(2), O1ꢀRh1ꢀP1
84.74(14), O1ꢀRh1ꢀCl4 176.98(14), P1ꢀRh1ꢀCl4 97.37(8),
O1ꢀRh1ꢀCl3 88.40(15), P1ꢀRh1ꢀCl3 86.88(8), Cl4ꢀRh1ꢀCl3
89.56(8), O1ꢀRh1ꢀCl2 90.13(15), P1ꢀRh1ꢀCl2 94.45(7),
Cl4ꢀRh1ꢀCl2 91.85(8), Cl3ꢀRh1ꢀCl2 177.92(9), O1ꢀRh1ꢀCl1
86.98(14), P1ꢀRh1ꢀCl1 171.38(8), Cl4ꢀRh1ꢀCl1 91.00(8),
Cl3ꢀRh1ꢀCl1 95.29(8), Cl2ꢀRh1ꢀCl1 83.16(7), Rh2ꢀCl2ꢀRh1
99.37(7), O2ꢀRh2ꢀP2 83.19(14), O2ꢀRh2ꢀCl6 177.97(16),
P2ꢀRh2ꢀCl6 98.33(8), O2ꢀRh2ꢀCl5 90.34(16), P2ꢀRh2ꢀCl5
88.05(8), Cl6ꢀRh2ꢀCl5 91.07(8), O2ꢀRh2ꢀCl2 89.06(16),
P2ꢀRh2ꢀCl2 95.15(7), Cl6ꢀRh2ꢀCl2 89.45(8), Cl5ꢀRh2ꢀCl2
176.65(8), O2ꢀRh2ꢀCl1 87.04(14), P2ꢀRh2ꢀCl1 170.16(8),
Cl6ꢀRh2ꢀCl1 91.42(8), Cl5ꢀRh2ꢀCl1 93.12(8), Cl2ꢀRh2ꢀCl1
83.56(7), Rh2ꢀCl1ꢀRh1 92.65(7).
90.4(3),
O1ꢀRh1ꢀCl2
86.3(7),
P1ꢀRh1ꢀCl2
91.9(3),
Cl4ꢀRh1ꢀCl2 92.3(3), Cl3ꢀRh1ꢀCl2 173.7(3), O1ꢀRh1ꢀCl1
88.6(5), P1ꢀRh1ꢀCl1 171.5(3), Cl4ꢀRh1ꢀCl1 91.2(3),
Cl3ꢀRh1ꢀCl1 89.9(3), Cl2ꢀRh1ꢀCl1 84.3(3), Rh2ꢀCl1ꢀRh1
93.9(2),
O2ꢀRh2ꢀP2
85.4(6),
O2ꢀRh2ꢀCl5
91.9(7),
P2ꢀRh2ꢀCl5 87.6(4), O2ꢀRh2ꢀCl6 175.5(8), P2ꢀRh2ꢀCl6
96.5(4), Cl5ꢀRh2ꢀCl6 92.3(4), O2ꢀRh2ꢀCl1 85.0(7),
P2ꢀRh2ꢀCl1 97.1(4), Cl5ꢀRh2ꢀCl1 174.1(3), Cl6ꢀRh2ꢀCl1
90.6(4), O2ꢀRh2ꢀCl2 88.7(6), P2ꢀRh2ꢀCl2 173.2(4),
Cl5ꢀRh2ꢀCl2 89.1(3), Cl6ꢀRh2ꢀCl2 89.6(3), Cl1ꢀRh2ꢀCl2
85.9(3), Rh1ꢀCl2ꢀRh2 95.2(3).
trans-O,O arrangements (types II and V) in front of the
more sterically unstable cis-O,O geometry (type IV).
However, differentiation between the preferred arrange-
ments and the O-equatorial-P-equatorial (type III)
needs a deeper discussion on the stereochemistry of the
chiral ligand.
the pseudo-planar Rh2Cl2 core (Fig. 5). Alternatively,
in an hypothetical equatorial–equatorial arrangement
(type III) the preferred chelate ring conformation
would also locate the menthane cycles parallel to each
other, but crossing the Rh2Cl2 plane (Fig. 5), as we
have recently observed for the related ligand,
(1R,2S,5R)-1-diphenylphosphinomethyl-2-isopropyl-5-
methyl-cyclohexanethiol, in its trans-bis(phosphinothio-
lato)palladium(II) and platinum complexes.38 Thus, the
stereoelectronic preference of the chelate ring to adopt
the l conformation gives rise to an appreciable differ-
ence in the structure and stability between complexes
with O-axial-P-equatorial coordination and complexes
with O-equatorial-P-equatorial disposition. The experi-
mental observations seem to indicate that the last situa-
tion is energetically disfavored.
On account that the preferred conformation for the
chiral chelate ring depends on the configuration of the
stereogenic carbon, the more voluminous substituent
being placed in an equatorial position,37 the chelate
rings of complexes 7a,b and 8 adopt invariably the l
conformation placing both tertiary carbons of the men-
thane cycle, carrying the isopropyl groups, in equatorial
positions. For the observed structures 7a,b and 8 (types
II and V) the preferred conformation of the chelate
rings places the menthane cycles in a pseudo-parallel
arrangement, but with each one on a different side of

2534
J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
Figure 5. The stereo-electronic preference to place the tertiary
carbon of the menthane cycle, carrying the isopropyl group,
in equatorial position should produce a dramatic difference in
the structure and stability between complexes with O-axial-P-
equatorial coordination (7a (a) and 7b (b)) and complexes
with an hypothetical O-equatorial-P-equatorial coordination
of the hydroxylated phosphine (c). Hydrogen atoms and aryl
rings are omitted to fully appreciate the geometry of the
ligand arrangements.
Figure 4. ORTEP plot (50%) of complex 8, hydrogen atoms
and aryl rings are omitted to fully appreciate the geometry of
,
the complex. Selected distances (A) and angles (°): Rh1ꢀO1
2.062(3), Rh1ꢀO2 2.081(3), Rh1ꢀP2 2.219(2), Rh1ꢀCl2
2.296(2), Rh1ꢀCl3 2.317(2), Rh1ꢀCl1 2.431(2), O1ꢀRh1ꢀO2
86.93(13), O1ꢀRh1ꢀP2 97.50(10), O2ꢀRh1ꢀP2 83.49(12),
O1ꢀRh1ꢀCl2 90.58(5), O2ꢀRh1ꢀCl2 176.66(14), P2ꢀRh1ꢀCl2
99.08(7), O1ꢀRh1ꢀCl3 175.99(13), O2ꢀRh1ꢀCl3 91.36(13),
P2ꢀRh1ꢀCl3 85.92(7), Cl2ꢀRh1ꢀCl3 90.96(7), O1ꢀRh1ꢀCl1
84.73(13), O2ꢀRh1ꢀCl1 89.54(11), P2ꢀRh1ꢀCl1 172.54(5),
Cl2ꢀRh1ꢀCl1 87.99(5), Cl3ꢀRh1ꢀCl1 91.62(6).
the hydroxylated phosphine complexes of rhodium(I) as
precursors in the catalytic hydroformylation of styrene
with carbon monoxide and hydrogen. Catalytic systems
formed by the addition of one equivalent of hydroxyl-
ated phosphine 3 to the metal precursor [Rh(m-
Cl)(CO)2]2 showed to be highly active in the carbonyla-
tion of this vinyl aromatic. Conversions are practically
complete after 5–6 h of reaction, except at low temper-
ature (Fig. 6), with initial turn over frequencies up to
440 h−1, although in some cases an activation period
(ca. 15 min.) was observed. GC–MS analysis of the
final solutions showed that aldehydes were the only
5. Evaluation of the new chiral hydroxylated phosphine
rhodium(I) complexes in the catalytic hydroformylation
of styrene
In Table 1 we offer the first data on the evaluation of
Scheme 4. Structures described for the edge-sharing bioctahedral (ESBO) complexes of transition metals (groups IV–VIII).

J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
2535
Table 1. Hydroxylated phosphine 3 complexes of rhodium(I) as catalyst precursors in the hydroformylation of styrene with
CO and H2 to give 2-phenylpropanal (iso) and 3-phenylpropanal (n)a
3/Rh ratio
Temperature (°C)
Pressure (bar)
H2/CO ratio
TOF (h−1 b
)
n/iso ratio
1
1
1
2
1
80
80
60
80
80
10
20
20
20
20
1/1
1/1
1/1
1/1
2/1
100
440
120c
269
315c
49/51
37/63
26/74
36/64
39/61
a Reaction conditions: styrene, 10.0 mmol; [Rh2Cl2(CO)4], 0.025 mmol; toluene, 27.6 mL; reaction time, 24 h.
b Initial turnover frequency measured in the first 30 min of reaction.
c Initial turnover frequency measured in the first 30 min after the activation period.
lated phosphine in the reaction conditions. This ligand
effect is not fully understood on the molecular level and
is still under study.
6. Experimental
All reactants were commercially obtained and used
without further purification. Compounds 2–7 were syn-
thesized using standard Schlenk techniques under nitro-
gen atmosphere. Solvents were dried by standard
methods and distilled and deoxygenated before use.
Elemental analyses were performed on a Fisons EA-
1108 analyzer. Infrared spectra of samples in KBr
pellets were recorded on a Mattson Satellite FTIR
spectrophotometer. Deuterated solvents for NMR mea-
surements were dried over molecular sieves. Proton
NMR spectra were recorded at 200 MHz on a Bruker
DPX-200 spectrometer. Peak positions are relative to
tetramethylsilane as internal reference. 31P{1H} NMR
spectra were recorded on the same instrument operating
at 81.0 MHz, chemical shifts are relative to external
85% H3PO4, with downfield values reported as positive.
13C{1H} NMR spectra were recorded on the same
instrument operating at 50.3 MHz, chemical shifts are
relative to tetramethylsilane as the internal reference.
Gas chromatography analyses were performed on a
Shimatzu GC-17A in a Tracer TRB-5 capillary column
(30 m×0.25 mm diameter) or in a chiral J&W Scientific
CYCLODEXB (30 m×0.25 mm diameter), incorporat-
ing FID detector. Optical rotations of the products
were measured on a kru¨ss P3002 electronic polarimeter
equipped with a sodium light source (589 nm). The
identification of GC peaks was done by GC–MS analy-
ses on a Thermo Quest Trace GC 2000 in a J&W
Scientific DB-5 capillary column (30 m×0.25 mm
diameter), incorporating MS detector. Flash chro-
matography was performed on silica gel 60 A CC.
Solvents for chromatography were distilled at atmo-
spheric pressure prior to use. Microdistillation proce-
dures were performed on a Buchi GK-R-51.
Figure 6. Conversion of styrene into aldehydes versus time.
Reaction conditions are indicated in Table 1 (ꢀ entry 1; ꢁ
entry 2; ꢂ entry 3; ꢃ entry 4; 2 entry 5).
products, only traces of alcohols (<0.5%) were detected.
Regarding the regioselectivity, the reaction preferen-
tially produced the branched aldehyde and the selectiv-
ity was very sensitive to the reaction temperature and
pressure. An increase in the regioselectivity was
observed with a decrease in the reaction temperature.
Conversely, a decrease in the total pressure produced
an equivalent amount of both aldehydes. Other
parameters such as the H2/CO ratio appreciably
affected neither the selectivity nor the activity of the
reaction. With regard to the enantioselectivity of the
reaction, no enantiomeric excess within the experimen-
tal error of measurement, were observed, suggesting a
monodentate behavior for ligand 3, at least in the
rhodium(I) intermediate species. This is in agreement
with the structural data discussed above. However, the
increase of the 3/Rh ratio produces inhibition of the
catalytic activity. This observation is surprising since
for monodentate ligands, an increase in the activity
with the L/Rh ratio is expected, at least up to a L/Rh
value of 4.39 On the other hand, the regio and enan-
tioselectivities do not vary, pointing to a similar cata-
lytic active species that is transformed into inactive
complexes in the presence of an excess of the hydroxy-
6.1. Preparation of (1S,2S,5R)-1-diphenylphosphino-
methyl-2-isopropyl-5-methyl-cyclohexanol 3
Step 1. A mixture of NaH (0.92 g, 21.0 mmol, 55%) and
(CH3)3SOI (4.62 g, 21.0 mmol) in anhydrous DMSO
(15 mL), under nitrogen atmosphere, was vigorously
stirred at rt for 2 h and placed in an ice bath. A

2536
J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
solution of (−)-menthone (3.84 mL, 20.0 mmol) in
anhydrous DMSO (5 mL) was gradually added over 10
min, the reaction mixture was then protected from light
and stirred at rt for 24 h. The reaction mixture was
poured on ice/water (80 mL) and the aqueous phase
extracted with diethyl ether (3×40 mL). The organic
phase was washed with water (2×20 mL), dried with
magnesium sulphate, filtered, evaporated to dryness,
and distilled (70–75°C, 0.1 Torr) to yield liquid
(1S,4S,7R)-4-isopropyl-7-methyl-1-oxa-spiro[2.5]octane
2 of purity >97% by GLC (2.69 g, 80%). 1H NMR
was slowly added to an ice-cold solution of a commer-
cial mixture of NaNH2 and (C6H5)3PCH3Br (14.47 g,
34.2 mmol) in anhydrous THF (15 mL), with stirring
under a nitrogen atmosphere. After 3 h, aqueous 25%
NaOH (15 mL) was added. The aqueous phase was
extracted with diethyl ether (3×10 mL). The organic
phase was washed with deoxygenated saturated ammo-
nium chloride aqueous solution until neutrality and
deoxygenated water (15 mL), dried with magnesium
sulphate, filtered and evaporated to dryness at 35°C.
Purification of the crude product by flash chromatogra-
phy (hexane) afforded liquid (1S,4R)-1-isopropyl-4-
methyl-2-methylene-cyclohexane 5 of purity >99% by
3
(CDCl3 sol.): l 0.80 (d, 3H, H10, J=6.8 Hz); 0.90 (d,
3
3
3H, H11, J=6.8 Hz); 0.91 (d, 3H, H9, J=6.5 Hz);
2
1
1.0-1.9 (m, 9H, H3-H8); 2.47 (d, 1H, H1, J=4.5 Hz);
GC (3.10 g, 88%). H NMR (CDCl3 sol.): l 0.7–0.9 (m,
2
2.90 (d, 1H, H1%, J=4.5 Hz). 13C{1H} NMR (CDCl3
9H, H9-H11); 1.0–1.7 (m, 7H, H3,H4-H7); 1.89 (psoct,
3
2
sol.): l 18.61 (s, C9); 21.83 (s, C10); 22.31 (s, CH11);
24.38 (s, C5); 25.88 (s, C8); 30.61 (s, C4); 33.94 (s, C6);
43.41 (s, C3); 44.81 (s, C7); 51.88 (s, C1); 61.05 (s, C2).).
MS: m/e 168 (M+, 5%); 153 (M+−15, 100%); 125 (M+−
43, 65%); 95 (75%); 81 (85%). [h]2D0=+7.7 (c 0.015,
CH2Cl2).
1H, H8, J:6.7 Hz); 2.28 (dd, 1H, H3%, J=11.9 Hz,
3J=3.6 Hz); 4.58 (br.s, 1H, H1); 4.70 (br.s, 1H, H1%).
13C{1H} NMR (CDCl3 sol.): l 18.98 (s, C9); 21.38 (s,
C10); 22.09 (s, CH11); 27.06 (s, C8); 27.37 (s, C5); 33.37
(s, C6); 33.99 (s, C4); 44.40 (s, C3); 49.36 (s, C7); 106.08
(s, C1); 151.16 (s, C2). IR (KBr): loop (ꢁCH2), 890 cm−1;
w(CꢁCH2), 1644 cm−1; w(ꢁCH2), 3086 cm−1.
Step
2.
(1S,4S,7R)-4-isopropyl-7-methyl-1-oxa-
spiro[2.5]octane 2 (200 mg, 1.19 mmol) was slowly
added to an ice-cold solution of potassium
diphenylphosphide (0.5 M in tetrahydrofuran, 12.7 mL,
6.38 mmol), while stirring under a nitrogen atmosphere.
The reaction mixture was then vigorously stirred at rt.
After 3 h, deoxygenated methanol (3 mL), deoxy-
genated saturated ammonium chloride aqueous solu-
tion (3 mL), and deoxygenated water (5 mL) were
consecutively added to the reaction mixture. The
aqueous phase was extracted with diethyl ether (3×15
mL). The organic phase was washed with water (15
mL), dried with magnesium sulphate, filtered and evap-
orated to dryness. Purification of the crude product by
flash chromatography (hexane/ethyl acetate: 9/1)
afforded (1S,2S,5R)-1-diphenylphosphinomethyl-2-iso-
propyl-5-methyl-cyclohexanol 3 as an oil of purity
>99% by NMR (334.7 mg, 76%). 1H NMR (CDCl3
sol.): l 0.7–1.0 (m, 9H, H9-H11); 1.0-2.0 (m, 8H, H3-H6,
Step 2. A solution of m-CPBA (4.08 g, 23.7 mmol) in
CH2Cl2 (25 mL) was added to a mixture containing
(1S,4R)-1-isopropyl-4-methyl-2-methylene-cyclohexane
5 (1.08 g, 7.09 mmol), CH2Cl2 (15 mL) and aqueous
NaHCO3 (15 mL, 5%). The reaction mixture was pro-
tected from light and stirred for 4 h. The aqueous phase
was extracted with CH2Cl2 (2×10 mL). The organic
phase was washed with NaOH 2 M (2×20 mL) and
water (15 mL), dried with magnesium sulphate, filtered,
evaporated to dryness at 35°C and distilled (70–75°C,
0.1 Torr) to yield a liquid mixture of oxiranes 2 and 4
1
(1.04 g, 87.5%, 55:45). Data for 4: H NMR (CDCl3
3
sol.): l 0.78 (d, 3H, H10, J=6.8 Hz); 0.91 (d, 3H, H11,
3
3J=6.8 Hz); 0.95 (d, 3H, H9, J=6.7 Hz); 0.9–1.9 (m,
2
9H, H3-H8); 2.49 (d, 1H, H1, J=4.8 Hz); 2.75 (d, 1H,
2
H1%, J=4.8 Hz). 13C{1H} NMR (CDCl3 sol.): l 19.53
(s, C9); 21.67 (s, C10); 22.85 (s, CH11); 24.01 (s, C8);
24.90 (s, C5); 31.84 (s, C6); 32.82 (s, C4); 42.80 (s, C3);
46.03 (s, C7); 51.86 (s, C1); 60.22 (s, C2).
2
H8, OH); 2.17 (m, 1H, H7); 2.43 (dd, 1H, H1, J=14.4
Hz, 2JHꢀP=3.4 Hz); 2.69 (dd, 1H, H1%, 2J=14.4 Hz,
2JHꢀP=4.4 Hz); 7.2–7.8 (m, 10H, Har). 13C{1H} NMR
(CDCl3 sol.): l 18.05 (s, C9); 20.79 (s, C5); 22.17 (s,
C10); 23.35 (s, C11); 25.91 (s, C8); 28.02 (s, C4); 34.97 (s,
6.3. Preparation of trans-P,P-bis-{m-chlorocarbonyl-
[(1S,2S,5R)-1-diphenylphosphinomethyl-2-isopropyl-
5-methyl-cyclohexanol-P]rhodium(I)} 6
1
3
C6); 41.86 (d, C1, JCꢀP=15.5 Hz); 49.33 (d, C3, JCꢀP
=
3
12.1 Hz); 49.52 (d, C7, JCꢀP=4.7 Hz); 75.51 (d, C2,
2JCꢀP=13.7 Hz); 127–140 (Car). 31P{1H} NMR (CDCl3
sol.): l −24.87 (s). MS: m/e 354 (M+, 15%); 333 (M+−
18, 5%); 199 (100%); 186 (60%). [h]2D5=−8.8 (c 0.012,
CH2Cl2).
Ligand 3 (98 mg, 0.26 mmol) in CH2Cl2 (5 mL) was
added to a solution of [Rh2Cl2(CO)4] (51 mg, 0.13
mmol) also in CH2Cl2 (5 mL). The reaction mixture
was stirred at rt for 24 h. The volume was reduced to 3
mL and the product precipitated by the addition of
ethyl ether. 68 mg of complex 6 were obtained, 50%
yield, as an orange solid. 1H NMR (CDCl3 sol.): l
0.5–1.1 (m, 9H, H9-H11); 1.1–2.3 (m, 8H, H3-H6, H8);
6.2. Preparation of mixtures of (1S,4S,7R)-4-isopropyl-
7-methyl-1-oxa-spiro[2.5]octane 2 and (1R,4S,7R)-4-iso-
propyl-7-methyl-1-oxa-spiro[2.5]octane 4
2
2
2.65 (td, 1H, H1, J=14.2 Hz, JHꢀP=14.2 Hz, J=2.6
2
2
Method A. The procedure described to obtain epoxide 2
from (−)-menthone using (CH3)3SI as reactant pro-
duced a mixture of oxiranes 2 and 4 (95:5) in an 80%
yield.
Hz); 3.08 (dd, 1H, H1%, J=14.2 Hz, JHꢀP=8.0 Hz);
3.67 (br.s, 1H, OH) 7.3–8.2 (m, 10H, Har). 13C{1H}
NMR (CDCl3 sol.): l 18.77 (s, C9); 21.54 (s, C5); 22.25
(s, C10); 23.93 (s, C11); 26.73 (s, C8); 28.38 (s, C4); 34.54
(s, C6); 40.93 (d, C1, 1JCꢀP=25.2 Hz); 48.57 (d, C3,
3
Method B. Step 1. (−)-Menthone (4 mL, 23.15 mmol)
3JCꢀP=9.0 Hz); 49.71 (d, C7, JCꢀP=5.2 Hz); 88.40 (s,

J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
2537
C2); 127–137 (Car). 31P{1H} NMR (CDCl3 sol.): l 57.95
(d, JRhꢀP=162.1 Hz). Anal. found: C, 52.57; H, 5.69%.
Compound 7b: C52H74NCl6O2P2Rh2, Mr=1211.57;
1
,
orthorhombic; space group P212121, a=13.3659(7) A,
3
,
,
,
C48H62Cl2O4P2Rh2·CH2Cl2 calcd: C, 52.24; H, 5.73%.
b=16.5154(8) A, c=26.0653(13) A, V=5753.7(5) A ,
Z=4, zcalcd=1.399 Mg/m3, v=0.944 mm−1, 61730
reflections were collected of which 12515 are unique
(Rint=0.170), 6329 Fo>4|(Fo), 490 refined parameters,
R1=0.0559, wR2=0.1015, Goodness of fit on F2=
[h]2D5=−50.9 (c 0.011, CH2Cl2).
6.4. Preparation of bis{(OC-6-32)-m-chlorodichloro-
[(1S,2S,5R)-1-diphenylphosphinomethyl-2-isopropyl-5-
methyl-cyclohexanol-O,P]rhodium(III)} 7
0.858, Flack parameter −0.03(4), maximum residual
−3
,
electron density 0.569 (−0.575) e A .
Ligand 3 (111 mg, 0.30 mmol) in ethanol (5 mL) was
added to a solution of RhCl3·xH2O (77.2 mg, 0.30
mmol) also in ethanol (15 mL). The reaction mixture
was stirred at rt. After 24 h the volume was reduced to
10 mL and the orange precipitate that appeared, was
filtered and washed with cold ethanol (2 mL). The
recovered solid shows a low carbon and hydrogen
analysis suggesting that some unreacted RhCl3 was also
precipitated with the desired product. By successive
solid–liquid extractions with CH2Cl2 and evaporation
of the solvent, a solid (64 mg, 38%) with satisfactory
elemental analysis (vide infra) were obtained. 31P{1H}
NMR (CD2Cl2 sol.): l 47.68 (1JPꢀRh=110.8 Hz); 38.16
(1JPꢀRh=123.8 Hz). Anal. found: C, 48.23; H, 5.70%.
C46H62Cl6O2P2Rh2·21H2O calcd: C, 48.61; H, 5.59%.
Compound
8:
C23H31.50Cl12.50O1.50P1Rh1,
Mr=
(554.49)×2; tetragonal; space group P41212, a=
3
,
,
,
14.0399(11) A, c=26.401(3) A, V=5204.2(8) A , Z=8,
zcalcd=1.415 Mg/m3, v=0.988 mm−1, 55517 reflections
were collected of which 5133 are unique (Rint=0.18),
3789 Fo>4|(Fo), 266 refined parameters, R1=0.0481,
wR2=0.0952, Goodness of fit on F2=1.038, Flack
parameter 0.01(5), maximum residual electron density
0.399 (−0.649) e A .
−3
,
Crystallographic data (excluding structure factors) for
the structures in this paper have been deposited with
the Cambridge Crystallographic Data Centre as supple-
mentary publication numbers CCDC 206965, CCDC
206964 and CCDC 206963. Copies of the data can be
obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK [fax: +44(0)-
1223-336033 or e-mail: deposit@ccdc.cam.ac.uk].
6.5. X-Ray structure determinations
Compound 7a crystallizes from CH2Cl2 giving non
homogeneous crystals of poor quality. Only after sev-
eral attempts, a small crystal could be measured leading
to the structure described. No better data set of 7a
could be obtained. Suitable crystals of 7b were grown
by slow evaporation of a chloroform/n-hexane mixture
1:1 at 60°C. Crystals of 8 were obtained by slow
evaporation of chloroform at rt. All three compounds
lead to soft crystals which are difficult to handle and
decompose upon manipulation. All measured crystals
diffracted giving broad reflections with somewhat low
resolution.
6.6. Hydroformylation experiments
A toluene (27.6 mL) solution of styrene (10 mmol),
previously stirred with alumina for 24 h at −24°C,
[Rh(m-Cl)(CO)2]2 (0.025 mmol) and the corresponding
amount of the hydroxylated phosphine, prepared under
nitrogen atmosphere was introduced into an evacuated
reactor Chemipress (Trallero & Schlee S. L.) and heated
with stirring. Once the system reached thermal equi-
librium, the gas mixture was introduced to reach the
working pressure. During the reaction, the pressure was
maintained at a constant by introducing a gas mixture
from a gas ballast. The drop of pressure in the ballast
was monitored using a pressure transducer connected
to an electronic measurement and printing unit. After
each run, the reactor was cooled, its contents removed
and analyzed by GC–MS. In order to measure the
enantiomeric excess of the reaction, a sample of the
freshly obtained reaction mixture (2 mL) was slowly
added to a suspension of LiAlH4 (50 mg) in anhydrous
THF (5 mL). After 15 min, methanol (2 mL) and
aqueous HCl (0.5 M, 10 mL) were consecutively added.
The aqueous phase was extracted with dichloromethane
(3×10 mL) and the organic phase was dried with mag-
nesium sulphate and analyzed by GC in a J&W Scien-
tific CYCLODEXB (30 m×0.25 mm diameter) column.
Measurements were made on a Siemens P4 diffractome-
ter equipped with a SMART-CCD-1000 area detector,
MoKa radiation from a MACScience Co rotating
anode source,
a graphite monochromator and a
Siemens low temperature device LT2 (T=−120°C). The
measurements were made in the range 1.65–30.07°. Full
sphere data was collected, v and 8 scans. Programs
used: Data collection, Smart 5.625 (Bruker-AXS 2001);
data reduction, Saint Plus Version 1.6 (Bruker-Nonius
2002); absorption correction, SADABS V. 2.03 (2002)
and structure solution and refinement, SHELXTL Ver-
sion 6.12 (Sheldrick, 2000).
Compound 7a: C46H60Cl6O2.5P2Rh2, Mr=1133.40;
,
monoclinic; space group P21, a=11.685(2) A, b=
,
,
16.840(3) A, c=13.192(2) A, i=103.294(5)°, V=
2526.2(8) A , Z=2, zcalcd=1.490 Mg/m3, v=1.070
3
,
mm−1, 19161 reflections were collected of which 8512
were unique (Rint=0.173), 3545 Fo>4|(Fo), 490 refined
parameters, R1=0.095, wR2=0.2177, Goodness of fit
Acknowledgements
on F2=1.036, Flack parameter 0.05(15), maximum
This work was financially supported by the DGESIC,
projects PB98-0913-C02 and BQU2002-04070-C02-01.
−3
,
residual electron density 1.565 (−1.604) e A .

2538
J. Duran et al. / Tetrahedron: Asymmetry 14 (2003) 2529–2538
20. Cotton, F. A.; Eglin, J. L.; Kang, S.-J. J. Am. Chem. Soc.
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