A new bidentate aminophosphole-olefin ligand for the rhodium-catalyzed hydroformylation of mono- And disubstituted olefins

Article abstract of DOI:10.1021/om060625r

Reaction of 1-bromo-2,5-diphenylphosphole with 10,11-dihydro-5H-dibenzo[b, f]azepine resulted in the formation of the corresponding aminophosphole 3, which was structurally characterized. Reaction of 3 with [Rh₂(μ-Cl) ₂(C₂H₄)₄] and [Rh(COD) ₂][BF₄] afforded the complexes [Rh₂(μ-Cl) ₂(3)₂] (4) and [Rh-(COD)(3)][BF₄] (5), respectively. In both complexes, characterized by NMR as well as by X-ray crystallography, ligand 3 behaves as a chelate through coordination of the phosphorus atom and the olefinic part of the ligand to the rhodium center. The activity of both complexes was tested in the hydroformylation of mono- and disubstituted olefins at 20 bar of CO/H₂ pressure. Complex 5 proves to be the most efficient catalyst.

Full text of DOI:10.1021/om060625r

5528
Organometallics 2006, 25, 5528-5532
A New Bidentate Aminophosphole-Olefin Ligand for the
Rhodium-Catalyzed Hydroformylation of Mono- and Disubstituted
Olefins
Guilhem Mora,† Steven van Zutphen,† Claire Thoumazet,† Xavier F. Le Goff,†
Louis Ricard,† Hansjorg Grutzmacher,‡ and Pascal Le Floch*,†
Laboratoire “He´te´roe´le´ments et Coordination”, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex,
France, and Department of Chemistry and Applied Biosciences (D-CHAB), ETH Ho¨nggerberg,
Wolfgang-Pauli Strasse, 8093 Zu¨rich, Switzerland
ReceiVed July 13, 2006
Reaction of 1-bromo-2,5-diphenylphosphole with 10,11-dihydro-5H-dibenzo[b,f]azepine resulted in
the formation of the corresponding aminophosphole 3, which was structurally characterized. Reaction of
3 with [Rh2(µ-Cl)2(C2H4)4] and [Rh(COD)2][BF4] afforded the complexes [Rh2(µ-Cl)2(3)2] (4) and [Rh-
(COD)(3)][BF4] (5), respectively. In both complexes, characterized by NMR as well as by X-ray
crystallography, ligand 3 behaves as a chelate through coordination of the phosphorus atom and the
olefinic part of the ligand to the rhodium center. The activity of both complexes was tested in the
hydroformylation of mono- and disubstituted olefins at 20 bar of CO/H2 pressure. Complex 5 proves to
be the most efficient catalyst.
was found to be of particular interest for Suzuki-Miyaura cross-
coupling in the synthesis of diaryl rings from halogenoaryls and
phenylboronic acids.5 The most significant features of this ligand
are the rigid concave bidentate binding site and its strong
π-accepting capacity, as it has been shown that TROPP ligands
are able to stabilize anionic rhodium complexes, a specific ability
of strongly electron withdrawing ligands.6
In the present paper we report the synthesis of a diphen-
ylphosphole tethered to a dibenzoazepine moiety. This ligand
also features a coordination site composed of a phosphole in
close proximity to an olefin. The nitrogen atom of the diben-
zoazepine is too close to the phosphole to coordinate a metal,
but it does allow a mild and straightforward ligand synthesis.
Interestingly, it was found that Rh(I) complexes of this new
ligand exhibit promising activity in the hydroformylation of both
mono- and disubstituted olefins.
Introduction
The electronic environment of the metal center in a transition-
metal catalyst is a determining factor for both the catalytic
performance and the selectivity of the catalyst. Careful ligand
design can be used to make subtle changes to this electronic
environment. Since the electronic properties of phosphine
derivatives, stable carbenes, and nitrogen-containing compounds
can be readily modified through changes to their substitution
patterns, they are commonly found in many ligands of transition-
metal catalysts. Recently it was shown that olefins, more
commonly considered as substrates, can be functionalized and
used as ligands in efficient catalytic systems.1 Inspired by these
results, we have been involved in the largely unexploited
synthesis and study of mixed bidentate ligands featuring a
phosphorus and an olefinic moiety,2,3 as TROPP ligands
discovered by Grutzmacher et al.4 We reported on the synthesis
of a dibenzo[a,d]cycloheptenyl dibenzophosphole ligand and
the catalytic activity of its palladium(II) complex. This complex
Results and Discussion
Ligand 3 was synthesized in a one-pot synthetic approach
from 1,1′-bis(2,5-diphenylphosphole) (1).7 The first step involves
the cleavage of the P-P bond with bromine in dichloromethane
at low temperature to afford the 1-bromophosphole 2.7 This
intermediate does not need to be isolated: addition of 1 equiv
of 10,11-dihydro-5H-dibenzo[b,f]azepine to the crude reaction
mixture in the presence of 2 equiv of triethylamine at low
temperature univocally yielded 3, which was recovered as a
yellow solid in 80% yield (Scheme 1). The solid phosphole 3
proved to be very stable to both air and moisture.
* To whom correspondence should be addressed. Tel: +33 1 69 33 45
70. Fax: +33 1 69 33 39 90. E-mail: lefloch@poly.polytechnique.fr.
† Ecole Polytechnique.
‡ ETH Ho¨nggerberg.
(1) (a) Evans, W. J.; Kozimor, S. A.; Hillman, W. R.; Ziller, J. W.
Organometallics 2005, 24, 4676-4683. (b) Gareau, D.; Sui-Seng, C.; Groux,
L. F.; Brisse, F.; Zargarian, D. Organometallics 2005, 24, 4003-4013. (c)
Lail, M.; Bell, C. M.; Conner, D.; Cundari, T. R.; Gunnoe, T. B.; Petersen,
J. L. Organometallics 2004, 23, 5007-5020. (d) Alias, F. M.; Daff, P. J.;
Paneque, M.; Poveda, M. L.; Carmona, E.; Perez, P. J.; Salazar, V.;
Alvarado, Y.; Atencio, R.; Sanchez-Delgado, R. Chem. Eur. J. 2002, 8,
5132-5146.
(2) (a) Piras, E.; La¨ng, F.; Ru¨egger, H.; Stein, D.; Wo¨rle, M.; Gru¨tzma-
cher, H. Chem. Eur. J 2006, 12, 5849-5858. (b) Shintani, R.; Duan, W.
L.; Okamoto, K.; Hayashi, T. Tetrahedron: Asymmetry 2005, 16, 3400-
3405. (c) Maire, P.; Deblon, S.; Breher, F.; Geier, J.; Bohler, C.; Ruegger,
H.; Schonberg, H.; Grutzmacher, H. Chem. Eur. J. 2004, 10, 4198-4205.
(d) Barbaro, P.; Ienco, A.; Mealli, C.; Peruzzini, M.; Scherer, O. J.; Schmitt,
G.; Vizza, F.; Wolmershauser, G. Chem. Eur. J. 2003, 9, 5195-5210. (e)
Park, Y. A. W.; Meek, D. W. Bull. Korean Chem. Soc. 1995, 16, 524-
528. (f) Tau, K. D.; Meek, D. W.; Sorrell, T.; Ibers, J. A. Inorg. Chem.
1978, 17, 3454-3460.
(4) Thomaier, J.; Boulmaaz, S.; Schonberg, H.; Ruegger, H.; Currao,
A.; Grutzmacher, H.; Hillebrecht, H.; Pritzkow, H. New J. Chem. 1998,
22, 947-958.
(5) Thoumazet, C.; Ricard, L.; Grutzmacher, H.; Le Floch, P. Chem.
Commun. 2005, 1592-1594.
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Grutzmacher, H. New J. Chem. 2001, 25, 83-92. (b) Scho¨nberg, H.;
Boulmaaˆz, S.; Wo¨rle, M.; Liesum, L.; Schweiger, A.; Gru¨tzmacher, H.
Angew. Chem., Int. Ed. 1998, 37, 1423-1426.
(7) Charrier, C.; Bonnard, H.; Mathey, F.; Neibecker, D. J. Organomet.
Chem. 1982, 231, 361-367.
(3) Laporte, U.; Bohler, C.; Schonberg, H.; Grutzmacher, H. J. Orga-
nomet. Chem. 2002, 641, 227-234.
10.1021/om060625r CCC: $33.50 © 2006 American Chemical Society
Publication on Web 10/06/2006

A New Bidentate Aminophosphole-Olefin Ligand
Organometallics, Vol. 25, No. 23, 2006 5529
Table 1. Summary and of Data Collection and Structure
Refinement Details for 3 and 5
3
5
cryst size (mm)
empirical formula
0.20 × 0.20 × 0.20 0.22 × 0.11 × 0.09
C30H22NP
C38H34NPRhBF4‚
CH2Cl2
mol mass
cryst syst
space group
a (Å)
b (Å)
c (Å)
427.46
monoclinic
P21/n
9.1980(10)
12.9790(10)
18.7910(10)
90.00
103.1260(10)
90.00
774.83
monoclinic
P21/c
13.0450(10)
18.6660(10)
15.6270(10)
90.00
109.7510(10)
90.00
R (deg)
Figure 1. View of one molecule of 3. Thermal ellipsoids are drawn
at the 30% probability level. Hydrogen atoms are omitted for clarity.
Selected bond distances (Å) and angles (deg): P1-N1, 1.697(1);
P1-C1, 1.825(1); P1-C4, 1.817(1); C1-C2, 1.354(2); C2-C3,
1.447(2); C3-C4, 1.350(2); N1-P1-C1, 108.60(5); N1-P1-C4,
107.56(5); C1-P1-C4, 91.07(6); P1-C1-C2, 108.5(1); C1-C2-
C3, 115.1(1); C2-C3-C4, 115.3(1); C3-C4-P1, 108.8(1).
â (deg)
γ (deg)
V (Å3)
2184.7(3)
4
1.300
3581.3(4)
4
1.437
Z
calcd density (g cm-3
)
abs coeff (cm-1
)
0.144
0.646
θ
max (deg)
F(000)
30.03
896
30.03
1580
index ranges
-12 to +12;
-18 to +16;
-26 to +26
-18 to +18;
-23 to +26;
-22 to +21
18 499/10 414
7941
Scheme 1
no. of rflns collected/indep 11 759/6367
no. of rflns used
4830
Rint
0.0261
0.0213
abs cor: min, max
no. of params refined
no. of rflns/params
final R1a/wR2 (I > 2σ(I))b
goodness of fit on F2
0.9717, 0.9717
289
16
0.0422/0.1241
1.076
0.294(0.047)/
-0.404(0.047)
0.8710, 0.9442
435
18
0.0463/0.1503
1.054
0.609(0.090)/
-0.740(0.090)
diff peak/hole (e Å-3
)
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) (∑w||Fo| - |Fc|| /∑w|Fo| )1/2
.
Scheme 2
Ligand 3 was fully characterized by NMR spectroscopy,
elemental analysis, and X-ray crystallography. A view of one
molecule of 3 is presented in Figure 1, with the most significant
metric parameters listed in the corresponding legend. Crystal
data and structure refinement details are presented in Table 1.
The solid-state structure of 3 does not deserve special comment,
and all data compare with those obtained for similar 2,5-
diphenylphosphole derivatives.5,8
dichloromethane under reflux. In this case, the major product,
however, gave rise to a doublet at 157.9 ppm. This major
product could be crystallized from the crude reaction mixture
using hexanes and isolated in 65% yield as an air- and moisture-
stable solid (4; Scheme 2). Using NMR spectroscopy, 4 was
fully characterized. It compromises a dimeric structure, resulting
from the displacement of the two ethylene ligands by 3.
Complex 4 proved to be sensitive to neither air nor moisture.
The proposed structure of 4, on the basis of the NMR data,
was confirmed by an X-ray crystal structure analysis. Its
structure contains two square-planar rhodium centers bridged
by two chloride atoms. A plot of the structure and the
corresponding tables are presented in the Supporting Informa-
tion.
Finally, reaction of 3 with [Rh(COD)2][BF4] in dichlo-
romethane at room temperature cleanly yielded complex 5,
which was isolated as an air- and moisture-stable orange solid
(Scheme 3). Coordination of the phosphorus atom was observed
in the 31P NMR spectrum and that of the olefin moiety in both
the 1H and the 13C NMR spectrum. In the 1H NMR spectrum a
high-frequency shift is observed for the vinylic protons: from
δ 6.04 ppm in 3 to δ 6.94 ppm in 5. In the 13C NMR spectrum,
a low-frequency shift is observed for these two vinylic carbon
atoms: from δ 131.1 ppm in 3 to δ 100.0 ppm in 5. Similar
Three different rhodium precursors were used in an attempt
to synthesize the corresponding Rh(I) complexes of 3: [Rh2-
(µ-Cl)2(C2H4)4], [Rh(COD)2][BF4], and the dimeric [Rh2(µ-Cl)2-
(COD)2] complex. Unfortunately, reaction of 3 with [Rh2(µ-
Cl)2(COD)2] did not proceed cleanly and afforded a mixture of
products. A detailed examination of the different coupling
patterns observed in the 31P NMR spectrum was used to
elucidate the structure of the major product. The 31P NMR
signals of this species consist of a classical ABX spin system,
1
2
with JPRh ) 158.0, 110 Hz and the large value JPP ) 401.0
Hz, which strongly suggest that two phosphorus atoms are
coordinated to the metal in a trans fashion. We believe this to
be due to the coordination of two ligand molecules, one probably
behaving as a bidentate chelate and the second one as a
monodentate ligand through coordination of the phosphorus
atom only. We were not able to isolate this product from the
reaction mixture.
A similar ABX spin system was observed in the product of
1
the reaction of 3 with
/
equiv of [Rh(η2-C2H4)2Cl]2 in
2
(8) Melaimi, M.; Thoumazet, C.; Ricard, L.; Le Floch, P. J. Organomet.
Chem. 2004, 689, 2988-2994.

5530 Organometallics, Vol. 25, No. 23, 2006
Mora et al.
Scheme 4
Scheme 5
Figure 2. View of one molecule of 5. The numbering is arbitrary
and different from that used in NMR spectra. Thermal ellipsoids
are drawn at the 30% probability level. Hydrogen atoms are omitted
for clarity. Selected bond distances (Å) and angles (deg): Rh1-
C17, 2.341(3); Rh1-C18, 2.286(3); Rh1-C31, 2.191(3); Rh1-
C32, 2.185(3); Rh1-C35, 2.322(3); Rh1-C36, 2.308(3); Rh1-
P1, 2.2116(7); C31-C32, 1.375(5); C35-C36, 1.353(5); C17-
C18, 1.389(4); P1-N1, 1.717(2); P1-C1, 1.821(3); P1-C4,
1.833(3); C1-C2, 1.351(4); C2-C3, 1.455(4); C3-C4, 1.356(4);
N1-P1-C1, 104.7(1); N1-P1-C4, 103.2(1); C1-P1-C4, 94.0-
(1); P1-C1-C2, 107.0(2); C1-C2-C3, 115.9(2); C2-C3-C4,
117.5(2); C3-C4-P1, 105.6(2).
Table 2. Catalysis Results from Hydroformylation of
Styrene with 20 bar of CO/H2 (1/1) in Toluene ([styrene] )
0.28 M), with Complex 5 as Catalyst
temp (°C)
cat. (%)
yield (%)
TOF (h-1
)
b/l
room temp
room temp
40
1
0.5
0.5
75
75
80
3.75
7.5
8
96/4
94/6
90/10
Scheme 3
with a 94/6 branched/linear ratio (b/l). Increasing the catalyst
charge to 1% led to a similar conversion in 20 h with a b/l ratio
of 96/4. The results of these experiments are reported in Table
2. Complex 4 did not promote this particular reaction. We also
found that using Rh(acac)(CO)2 precursor in the presence of
an excess amount of ligand (20 equiv) yielded significant
amounts of aldehyde, albeit at a lower conversion. We therefore
did not further pursue this method.
displacements were observed in Rh(I) complexes of the TROPP
ligands and their functional derivatives.3,6a
The substrates cyclohexene and cyclooctene were used to
investigate the conversion of disubstituted olefins by catalysts
4 and 5 (Scheme 5, eqs 1 and 2). As expected, complex 5 turned
out to be the most efficient catalyst. With a low CO/H2 pressure
of 20 bar at 80 °C, the conversion of cyclohexene proceeded
with a 40% yield using only 0.025 mol % of catalyst at TOF )
400 h-1. This performance compares with those of known
catalytic systems.9,10 Less satisfying results were obtained with
dimer 4, which only yielded a TOF of 137.5. A TON of 290
was obtained in the conversion of cyclooctene into cyclooc-
tanecarbaldehyde (29% of conversion in 24 h at 80 °C using
0.1% of catalyst). Results obtained in the conversion of
cylohexene and cyclooctene are presented in Table 3. Finally,
we tested the activity of complex 4 and 5 in the isomerization/
hydroformylation process of the tetrasubstituted tetramethyl-
ethylene into 3,4-dimethylpentanal (Table 3; Scheme 5, eq 3).
Very few catalysts are able to promote this reaction. To the
best of our knowledge, the most efficient system was reported
by Breit in 2004 using 2,6-disusbtituted phosphinines (TOF )
118 h-1 under 60 bar of syngas at 100 °C in toluene).10 More
recently we reported on the use of a (η5-cyclophosphahexadi-
enyl)rhodium complex to catalyze this transformation, albeit
with a lower TOF.11 Complex 5 catalyzes the transformation
Crystals of 5, suitable for X-ray crystal structure analysis,
were obtained by slow diffusion of hexanes into a dichlo-
romethane solution of the complex at 4 °C. A view of one
molecule of 5 is presented in Figure 2, and the most significant
bond lengths and bond angles are listed in the corresponding
legend. Crystal data and structural refinement details are
presented in Table 1. As can be seen, the overall geometry
around the central rhodium is planar, and both the phosphorus
and the olefinic part of the ligand are coordinated in a cis
fashion. Metric parameters in 5 compare with those recorded
for other TROPP Rh(I) complexes. At 2.2116(7) Å the Rh(1)-
P(1) bond compares with similar Rh-P bonds in other reported
TROPP derivatives such as the complexes [Rh(MeTROPP)2]+
(2.226(1) and 2.260(1) Å) and [Rh(bis{TROPphenylphosphano}-
ethane)2]+ (2.208(2) and 2.227(2) Å).3,6a Similar conclusions
can be drawn for the coordinated CdC bond, which is
lengthened (1.389(4) Å in 5 vs 1.339(2) in 3).
The catalytic activity of complexes 4 and 5 was investigated
in the hydroformylation of several olefins. No reaction was
observed when the olefin ligand was used as a substrate using
0.5% amount of catalyst at 80 °C for 24 h. In experiments using
1-octene as a substrate, the catalysts showed encouraging
turnover rates but little or no selectivity toward the branched
or the linear product. Preliminary tests on styrene revealed that
complex 5 is a moderately active yet highly selective catalyst
(Scheme 4). When the reaction was carried out at room
temperature with low CO/H2 pressure (20 bar) and a catalyst
charge of 0.5%, a conversion of 75% was reached after 20 h
(9) (a)Breit, B.; Fuchs, E. Chem. Commun. 2004, 694-695. (b) Poyatos,
M.; Uriz, P.; Mata, J. A.; Claver, C.; Fernandez, E.; Peris, E. Organome-
tallics 2003, 22, 440-444. (c) Ungvary, F. Coord. Chem. ReV. 2004, 248,
867-880. (d) Vanrooy, A.; Orij, E. N.; Kamer, P. C. J.; Vanleeuwen, P.
Organometallics 1995, 14, 34-43.
(10) Breit, B.; Winde, R.; Mackewitz, T.; Paciello, R.; Harms, K. Chem.
Eur. J. 2001, 7, 3106-3121.

A New Bidentate Aminophosphole-Olefin Ligand
Organometallics, Vol. 25, No. 23, 2006 5531
Table 3. Catalysis Results from Hydroformylation of
Cyclohexene, Cyclooctene, and 2,3-Dimethylbut-2-ene with
20 bar of CO/H2 (1/1) in Toluene ([cyclohexene] )
[cyclooctene] ) 1.66 M and [2,3-dimethylbut-2-ene] ) 1.38
M) with Catalysts 4 and 5
and triethylamine (711 µL, 5.102 mmol) in dichloromethane (5 mL)
was slowly added to the bromophosphole solution at -78 °C. The
reaction was complete after 30 min, as observed by 31P NMR. The
reaction mixture was concentrated in vacuo, washed with hydro-
chloric acid, extracted with DCM (2 × 15 mL), and dried (MgSO4),
and the solvent was removed under reduced pressure to yield crude
3 as a yellow solid. Washing with methanol afforded the purified
ligand 3 in 80% yield. Anal. Calcd for C30H22NP: C, 84.29; H,
5.19. Found: C, 84.15; H, 5.21. 1H NMR (C6D6): δ 6.04 (s, 2 H,
temp
(°C)
time
(h)
cat.
(%)
yield
(%)
TOF
cat.
substrate
(h-1
)
5
4
5
5
5
4
80
80
80
90
90
90
cyclohexene
cyclohexene
cyclooctene
C2Me4
C2Me4
C2Me4
4
4
24
48
24
24
0.025
0.1
0.1
0.1
0.1
40
55
29
24
14.5
12
400
137.5
290
5
6
3
CHdCH), 6.44 (d, JHP ) 10.2 Hz, 2 H, Hâ-phosphole), 6.75-6.89
(m, 4 H, Hphenyl), 6.97-7.06 (m, 2 H, Hphenyl), 7.14 (m, 2 H, Hphenyl),
3
7.23 (m, 4 H, Hphenyl), 7.33 (m, 2 H, Hphenyl), 7.60 (d, JHH ) 7.2
0.1
5
Hz, 4 H, Hphenyl). 13C NMR (C6D6): δ 126.0 (Cphenyl), 127.2 (Cphenyl),
127.8 (d, JCP ) 2.7 Hz, Cphenyl), 128.4 (Cphenyl), 128.9 (Cphenyl), 129.0
using a CO/H2 pressure of 20 bar at 90 °C. The TOF observed
is modest but encouraging, considering the milder experimental
conditions in comparison to those reported earlier.
2
(Cphenyl), 129.1 (Cphenyl), 131.1 (CHdCH), 131.6 (d, JCP ) 13.4
2
1
Hz, Câ-phosphole), 135.8 (d, JCP ) 1.6 Hz, Cipso), 137.9 (d, JCP
)
17.6 Hz, CR-phosphole), 147.3 (d, JCP ) 8.8 Hz, Cphenyl), 150.0 (d,
In conclusion, we succeeded in the synthesis of a mixed
bidentate aminophosphole-alkene ligand. Importantly, this new
ligand, when coordinated to the cationic [Rh(COD)]+ fragment,
proves to be an efficient hydroformylation catalyst, especially
in the case of 1,2- and 1,1-disubstituted olefin derivatives. To
the best of our knowledge, similar ligands were never employed
in homogeneous catalyzed hydroformylations. Theoretical stud-
ies are currently ongoing, but one may propose that the good
activity of ligand 3 results from the strong π-accepting capacities
of both the phosphorus and the olefin moiety of the ligand.
Further studies exploring the use of our ligand in other synthetic
transformations are also underway, and the results will be
reported in due course.
JCP ) 3.8 Hz, Cphenyl). 31P NMR (C6D6): 62.9 (d, 3JPH ) 10.2 Hz).
Synthesis of Complex 4. To a solution of [Rh(C2H4)2Cl]2 (22.7
mg, 0.058 mmol) in dichloromethane (2 mL) was added a solution
of 3 (50 mg, 0.117 mmol) in dichloromethane (3 mL) dropwise at
room temperature. The mixture was refluxed for 2 h and then cooled
to 4 °C. Complex 4 was then isolated by slow diffusion of hexanes
into the crude reaction mixture. After filtration, the red-orange
powder was dried under vacuum (43 mg, 65%). Anal. Calcd for
C60H44Cl2N2P2Rh2: C, 63.68; H, 3.92. Found: C, 63.31; H, 3.91.
1H NMR (CD2Cl2): δ 4.89 (s, 4 H, HCdCH), 6.62-6.74 (m, 8 H,
H
phenyl), 6.79-6.85 (m, 4 H, Hphenyl), 6.90 (d, 4 H, 3JPH ) 26.7 Hz,
3
Hâ-phosphole), 7.13-7.32 (m, 16 H, Hphenyl), 8.13 (d, 8 H, JHH
)
7.1 Hz, Hphenyl). 13C NMR (CD2Cl2): 62.5 (d, JCRh ) 15.1 Hz,
HCdCH), 127.6 (d, JCRh ) 2.1 Hz, Cphenyl), 128.1 (Cphenyl), 128.4
(d, JCP ) 4.6 Hz, Cphenyl), 128.7 (d, JCRh ) 3.4 Hz, Cphenyl), 129.1
(Cphenyl), 129.5 (Cphenyl), 129.7 (d, JCP ) 3.5 Hz, Cphenyl), 134.1 (d,
2JCP ) 16.8 Hz, Câ-phosphole), 135.8 (d, 2JCP ) 13.3 Hz, Cipso), 141.4
1
Experimental Section
All reactions were routinely performed under an inert atmosphere
of argon or nitrogen by using Schlenk and glovebox techniques
and dry deoxygenated solvents. Dry hexanes were obtained by
distillation from Na/benzophenone. Dry dichloromethane was
distilled on P2O5, dry triethylamine on KOH, and dry toluene on
metallic Na. Nuclear magnetic resonance spectra were recorded on
a Bruker AC-300 SY spectrometer operating at 300.0 MHz for 1H,
75.5 MHz for 13C, and 121.5 MHz for 31P. Solvent peaks are used
as internal reference relative to Me4Si for 1H and 13C chemical shifts
(ppm); 31P chemical shifts are relative to an 85% H3PO4 external
reference. Coupling constants are given in hertz. The following
abbreviations are used: s, singlet; d, doublet; t, triplet; m, multiplet.
1,1′-Bis(2,5-diphenylphosphole) (1) was prepared by following a
published procedure,7 and its precursor, the 1,2,5-triphenylphos-
phole, is easily available on a multigram scale from the simple
reaction of dichlorophenylphosphine with 1,4-diphenyl-1,3-buta-
diene.12 All other reagents and chemicals were obtained com-
mercially and used as received. Elemental analyses were performed
by the “Service d’analyse du CNRS”, at Gif sur Yvette, France.
Hydroformylation reactions were performed in a stainless steel
autoclave, equipped with a magnetic stirrer, and heated by an oil
bath. Hydrogen and carbon monoxide were purchased from Air
Liquide. The GC yields were determined on a PERICHROM 2100
gas chromatograph equipped with a 30 m × 0.22 mm PER-
ICHROM column (SILICONE OV1, CP-SIL 5 CB).
1
(d, JCP ) 52.7 Hz, CR-phosphole), 141.9 (d, JCP ) 8.9 Hz, Cphenyl),
143.6 (Cphenyl). 31P NMR (CD2Cl2): 157.95 (dt, JPH ) 26.7 Hz,
3
1JPRh ) 196.8 Hz).
Synthesis of Complex 5. A solution of 3 (50 mg, 0.117 mmol)
in dichloromethane (3 mL) was added dropwise at room temperature
to a solution of [Rh(COD)2][BF4] (47.5 mg, 0.117 mmol) in
dichloromethane (3 mL). After 20 min, the reaction mixture was
concentrated in vacuo. Hexane (20 mL) was added, and the mixture
was stirred for 1 h. The resultant orange-brown solid was filtered
off, washed with hexane, and dried (82 mg, 97%). Anal. Calcd for
C38H34BF4NPRh: C, 62.92; H, 4.72. Found: C, 63.02; H, 4.78.
1H NMR (CD2Cl2): δ 2.26-2.74 (m, 8 H, CH2 of COD), 4.74-
4.77 (m, 2 H, CH of COD), 5.92-5.96 (m, 2 H, CH of COD),
6.94 (d, 2JHRh ) 1.1 Hz, 2 H, CHdCH), 7.0 (d, 3JPH ) 26.7 Hz, 2
H, Hâ-phosphole), 7.06-7.16 (m, 8 H, Hphenyl), 7.37-7.40 (m, 4 H,
Hphenyl), 7.57 (d, J ) 7.3 Hz, 2 H, Hphenyl), 7.76-7.83 (m, 4 H,
H
phenyl). 13C NMR (CD2Cl2): δ 28.0 (CH2 of COD), 29.3 (CH2 of
1
COD), 29.7 (CH2 of COD), 31.4 (CH2 of COD), 96.5 (d, JCRh
9.7 Hz, CHcis-P of COD), 100.1 (d, 1JCRh ) 6 Hz, CHdCH), 116.1
)
1
1
(dd, JCRh ) 9.7 Hz, JCP ) 4.5 Hz, CHtrans-P of COD), 127.6 (d,
JCP ) 5.2 Hz, Cphenyl), 128.5 (Cphenyl), 129.2 (Cphenyl), 129.3 (d, JCP
) 1.4 Hz, Cphenyl), 129.7 (Cphenyl), 130.6 (d, JCP ) 3.8 Hz, Cphenyl),
2
131.4 (Cphenyl), 133.4 (d, JCP ) 13 Hz, Cphenyl), 135.5 (d, JCP
)
2
3
Synthesis of Phosphole 3. To a solution of the bis(phosphole)
1 (600 mg, 1.275 mmol) in dichloromethane (5 mL) was added
bromine (66 µL, 1.275 mmol) at -78 °C. The solution turned from
orange to red and was stirred at room temperature for 30 min.
Completion of the reaction was confirmed by 31P NMR. A solution
of 10,11-dihydro-5H-dibenzo[b,f]azepine (495 mg, 2.551 mmol)
16.2 Hz, Câ-phosphole), 138.7 (dd, JCP ) 7.2 Hz, JCRh ) 1.2 Hz,
1
2
C
ipso), 141.5 (dd, JCP ) 49.3 Hz, JCRh ) 1.8 Hz, CR-phosphole),
142.3 (dd, JCP ) 3.2 Hz, JCRh ) 1.4 Hz, Cphenyl). 31P NMR (CD2-
3
1
Cl2): δ 141.35 (dt, JPH ) 26.7 Hz, JPRh ) 149.4 Hz).
X-ray Crystallography for Complexes 3 and 5. Yellow blocks
of 3 crystallized by slow diffusion of hexanes into a saturated
dichloromethane solution of 3. Orange needles of complex 5 were
obtained by diffusing hexanes at 4 °C into a dichloromethane
solution of complex 5. Data were collected on a Nonius Kappa
CCD diffractometer using a Mo KR (λ ) 0.710 73 Å) X-ray source
(11) Moores, A.; Mezailles, N.; Ricard, L.; Le Floch, P. Organometallics
2005, 24, 508-513.
(12) Campbell, I. G.; Cookson, R. C.; Hocking, M. B.; Hughes, A. N. J.
Chem. Soc. 1965, 2184-2193.

5532 Organometallics, Vol. 25, No. 23, 2006
Mora et al.
and a graphite monochromator at 150 K. Experimental details are
described in Table 1. The crystal structures were solved using SIR
9713 and SHELXL97.14 ORTEP drawings were made using ORTEP
III for Windows.15 These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ,
U.K.; fax, (internat.) +44-1223/336-033; e-mail, deposit@
ccdc.cam.ac.uk).
General Procedure for Styrene Hydroformylation. To a
solution of styrene (95 µL, 0.826 mmol) in toluene (3 mL) was
added the catalyst 5 (3 mg, 0.004 mmol for 0.5%; 6 mg, 0.008
mmol for 1%) under nitrogen. After complete dissolution of the
complex, the solution was placed in the high-pressure apparatus,
which was then charged with CO (10 bar) and then H2 (10 bar).
After the reaction time at the temperature indicated in Table 2, the
autoclave was cooled to room temperature and depressurized and
the reaction mixture was analyzed by GC with internal standard
and correction factors.
After complete dissolution of the complex, the solution was placed
in the high-pressure apparatus, which was then charged with CO
(10 bar) and then H2 (10 bar). After the reaction time at the
temperature indicated in Table 3, the autoclave was cooled to room
temperature and depressurized and the reaction mixture was
analyzed by GC with internal standard and correction factors.
General Procedure for 2,3-Dimethylbut-2-ene Hydroformyl-
ation. To a solution of 2,3-dimethylbut-2-ene (490 µL, 4.13 mmol)
in toluene (3 mL) was added the catalyst 5 (3 mg, 4.1 µmol for
0.1%) or the catalyst 4 (2.3 mg, 2.1 µmol for 0.1% in rhodium)
under nitrogen. After complete dissolution of the complex, the
solution was placed in the high-pressure apparatus, which was then
charged with CO (10 bar) and then H2 (10 bar). After the reaction
time at the temperature indicated in Table 3, the autoclave was
cooled to room temperature and depressurized and the reaction
mixture was analyzed by GC with internal standard and correction
factors.
General Procedure for Cyclohexene and Cyclooctene Hy-
droformylation. To a solution of cyclohexene (840 µL, 8.29 mmol)
or cyclooctene (1080 µL, 8.29 mmol) in toluene (5 mL) was added
catalyst 5 (1.5 mg, 2.1 µmol for 0.025%; 6 mg, 8.3 µmol for 0.1%)
or catalyst 4 (4.7 mg, 4.2 µmol for 0.1% in rhodium) under nitrogen.
Acknowledgment. This work was supported by the CNRS
(Centre National de la Recherche Scientifique), the Ecole
Polytechnique, the ETH Zu¨rich, and the Swiss National Science
Foundation.
(13) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo,
C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. SIR97, an
Integrated Package of Computer Programs for the Solution and Refinement
of Crystal Structures using Single-Crystal Data.
(14) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen, Go¨ttingen,
Germany, 1997.
Supporting Information Available: CIF files and tables giving
crystallographic data for 4 (including atomic coordinates, bond
lengths and angles, and anisotropic displacement parameters). This
material is available free of charge via the Internet at http://
pubs.acs.org.
(15) Farrugia, L. J. ORTEP-3; Department of Chemistry, University of
Glasgow.
OM060625R