Water-soluble metal complexes and catalysts: X. BIPHLOPHOS, a novel axially chiral diphosphine ligand: Preparation and application in the asymmetric rhodium-catalyzed hydroformylation of styrene

Article abstract of DOI:10.1016/S0022-328X(99)00036-4

A stereospecific synthesis of both enantiomers of the new axially chiral diphosphine ligand 2,2′-bis(diphenylphosphinomethyl)-4,4′,6,6′-tetrachloro-1, 1′-biphenyl 5 called BIPHLOPHOS, starting from the readily available pure enantiomers of 4,4′,6,6′-tetrachlorodiphenic acid, was developed. The (-)-enantiomer was then tested in the homogeneous rhodium-catalyzed asymmetric hydroformylation of styrene. The ligand was used to prepare the complex IrH(CO)(PPh₃)L₂ (L₂=5) 6, the crystal structure of which was determined and compared with the related complex RhH(CO)(PPh₃)(BISBI). Additionally, ligand 5 was sulfonated by classical methods to yield a uniform reaction product. This is in sharp contrast to the analogous ligands BISBI and NAPHOS, where sulfonation yields a complicated mixture of products. The sulfonated ligand is excellently water-soluble and shows activities and regioselectivities in the hydroformylation of styrene comparable to the well-investigated ligand BISBI.

Full text of DOI:10.1016/S0022-328X(99)00036-4

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 582 (1999) 204–210
Water-soluble metal complexes and catalysts
X. BIPHLOPHOS, a novel axially chiral diphosphine ligand:
preparation and application in the asymmetric rhodium-catalyzed
hydroformylation of styreneꢀ
Florian A. Rampf, Michael Spiegler, Wolfgang A. Herrmann *
Anorganisch-chemisches Institut, Technische Uni6ersita¨t Mu¨nchen, Lichtenbergstraße 4, D-85747 Garching, Germany
Received 30 December 1998
Abstract
A stereospecific synthesis of both enantiomers of the new axially chiral diphosphine ligand 2,2%-bis(diphenylphosphinomethyl)-
4,4%,6,6%-tetrachloro-1,1%-biphenyl 5 called BIPHLOPHOS, starting from the readily available pure enantiomers of 4,4%,6,6%-tetra-
chlorodiphenic acid, was developed. The (−)-enantiomer was then tested in the homogeneous rhodium-catalyzed asymmetric
hydroformylation of styrene. The ligand was used to prepare the complex IrH(CO)(PPh3)L2 (L2=5) 6, the crystal structure of
which was determined and compared with the related complex RhH(CO)(PPh3)(BISBI). Additionally, ligand 5 was sulfonated by
classical methods to yield a uniform reaction product. This is in sharp contrast to the analogous ligands BISBI and NAPHOS,
where sulfonation yields a complicated mixture of products. The sulfonated ligand is excellently water-soluble and shows activities
and regioselectivities in the hydroformylation of styrene comparable to the well-investigated ligand BISBI. © 1999 Elsevier Science
S.A. All rights reserved.
Keywords: Rhodium; Hydroformylation; Asymmetric catalysis; Diphosphines; Biphasic catalysis
ductions with rhodium-based catalyst systems were ob-
tained by Takaya et al. using phosphine–phosphite
ligands [6] of the BINAPHOS-type A (Scheme 1) or by
researchers at DuPont with diphosphite ligands [7].
Chirally modified platinum–tin catalysts have also been
known to induce high enantioselectivities [4,5]. How-
ever, all these catalysts suffer from the drawback of
limited stability in the presence of trace amounts of
water. On the other hand, very little is known about
water-stable rhodium–phosphine catalysts in asymmet-
ric hydroformylation. Most of the systems tested per-
formed rather poorly, yielding only around 20% ee in
the hydroformylation of the model substrate styrene
[4,5].
1. Introduction
Hydroformylation, the largest-volume technical pro-
cess of organometallic chemistry [1], has a long tradi-
tion in our research group [2,3]. Asymmetric
hydroformylation of styrene derivatives permits an in-
triguingly direct access to anti-inflammatory drugs on
the basis of 2-aryl-propionic acids, but has still re-
mained a challenging topic in enantioselective catalysis.
Not only must the enantioselectivity of the catalyst
system be high, but further problems arise from the
need for regio- and chemoselectivity, as non-racemic
aldehydes or hydrogenation products can be possible
by-products [4,5]. Remarkably high enantiomeric in-
Only recently, we described the use of the enan-
tiomerically pure NAPHOS ligand in the mono- and
biphasic hydroformylation of styrene, which for the
first time permits enantioselectivities of 34% ee [8]. In
contrast to most diphosphine ligands studied before,
the large natural bite angle of NAPHOS permits the
ꢀ Preceding communication in this series: R.W. Eckl, T. Priermeier,
W.A. Herrmann, J. Organomet. Chem. 532 (1997) 243–249.
* Corresponding author. Tel.: +49-89-289-13080; fax: +49-89-
289-13473.
E-mail address: lit@arthur.anorg.chemie.tu-muenchen.de (W.A.
Herrmann)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00036-4

F.A. Rampf et al. / Journal of Organometallic Chemistry 582 (1999) 204–210
205
Scheme 1. Biaryl ligands used together with rhodium in hydroformylation reactions.
formation of a nine-membered chelate ring with the
2.1. Stereospecific ligand synthesis
rhodium centre. The size of the chelate ring has a
strong influence on the coordination mode of the ligand
during the catalytic cycle. The recent work of our group
concerning the mechanism of rhodium-BINAPHOS
catalyzed asymmetric hydroformylation directs utmost
attention to the coordination of the diphosphine ligand
at the metal centre [9,10]. Therefore, we have continued
our studies of chiral large-bite angle diphosphine
ligands.
One of the outstanding properties of our BINAS
ligand (the sulfonated ligand NAPHOS B) is the oppor-
tunity of hydroformylation in biphasic systems with
a water-based catalyst phase, as the ligand can be
made completely water-soluble by sulfonation of the
aromatic backbone. However, a complicated mixture of
sulfonation products is formed due to the multifunc-
tionality of the polyaromatic molecule towards sul-
fonating reagents [11]. We now present a new chiral
diphosphine ligand with a large natural bite angle,
which can be selectively sulfonated to a water-soluble
product.
Starting with 4,4%,6,6%-tetrachlorodiphenic acid, which
was easily synthesized and separated into its enan-
tiomers according to well-established literature meth-
ods, we developed a classical stereospecific synthetic
route to both enantiomers of the optically pure ligand
2,2%-bis(diphenylphosphinomethyl)-4,4%,6,6%-tetrachloro-
1,1%-biphenyl (Scheme 2). As the (−)-enantiomer of
4,4%,6,6%-tetrachlorodiphenic acid is obtained more eas-
ily using the cheap and non-toxic chiral auxiliary dehy-
droabietylamine, we describe here the synthesis of the
chiral ligand derived from that precursor. The other
enantiomer can be prepared with comparable ease from
(+)-4,4%,6,6%-tetrachlorodiphenic acid, the isolation of
which involves brucine as chiral auxiliary. Because of
the toxicity of the latter we limited ourselves to demon-
strating the feasibility of the ligand synthesis from the
(+)-precursor and continued our investigations with
the other enantiomer of the ligand.
(−)-4,4%,6,6%-Tetrachlorodiphenic acid was quantita-
tively converted to the acid chloride by refluxing it
in excess SOCl2 for 2 h. The acid chloride was reduced
2. Results and discussion
2,2%-Bis(diphenylphosphinomethyl-)1,1%-biphenyl,
called BISBI C [12], was originally described by re-
searchers at the Kodak company as an efficient ligand
for the rhodium-catalyzed hydroformylation of a-
olefins with a high selectivity for straight-chain alde-
hydes. It is the biphenyl homologue of the
aforementioned ligand NAPHOS. In contrast to
NAPHOS, its axial chirality is not stable at room
temperature, and substituents in the 6,6%-positions
are required if the enantiomers are to be separated.
Although the preparation of 2,2%,6,6%-tetrasubstituted
1,1%-biphenyls is well established, no chiral BISBI-
analogous diphosphine ligand has been described up to
now.
Scheme 2. Reagents and conditions: (i) SOCl2, reflux, 2 h; (ii)
Li[AlH4], Et2O, −78°C, 12 h; (iii) MsCl, NEt3, CH2Cl2, −30°C, 1 h;
(iv) K[PPh2], THF, −78°C, 12 h. Abbreviations: Ph=C6H5, Ms=
SO2CH3.

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F.A. Rampf et al. / Journal of Organometallic Chemistry 582 (1999) 204–210
ligand. The bite angle of the chelating ligand 6 in this
complex is 124.2°, which is very similar to the bite angle
of 124.8° Casey observed in the analogous model com-
plex RhH(CO)(TPP)L2 (L2=BISBI) [14] (Table 1).
Thus, the chloro substituents in the 6,6%-positions of the
biphenyl backbone do not seem to hinder the flexibility
of the ligand and hence influence the coordination
behavior of the ligand with respect to BISBI.
The crystal structure is in full agreement with the
1
NMR spectra obtained from 6 in C6D6. The H-NMR
spectrum shows a doublet of triplets at −11.1 ppm (dt,
J(H–P3) 16.1 Hz, J(H–P1/P2) 24.2 Hz) caused by the
coupling of the hydride ligand to the three coordinated
phosphorus atoms. The 31P-NMR spectrum reveals a
complicated
ABX
coupling
pattern
of
the
diastereotopic chelating phosphorus atoms with the
triphenylphosphine.
2.3. Sulfonation of (9)-5
Fig. 1. PLATON plot and numbering scheme of the crystal structure of
IrH(CO)(TPP)L2 6. All hydrogens except for the hydride have been
Sulfonation of NAPHOS yields complicated mixtures
of water-soluble sulfonated phosphine ligands, which—
depending on the reaction conditions—consist of re-
gioisomers of several products with a variable degree of
sulfonation, ranging from two to eight [8,15]. On the
contrary, sulfonation of the ligand 5 yields a highly
water-soluble, uniform product.
,
omitted for clarity. Important dimensions include; bond lengths (A):
Ir–P(1) 2.2772(7), Ir–P(2) 2.2965(7), Ir–P(3) 2.3058(7), Ir–C(1)
1.903(3), Ir–H 1.57(4); bond angles (°): P(1)–Ir–P(2) 124.23(2),
P(1)–Ir–P(3) 121.52(2), P(2)–Ir–P(3) 110.17(2), C1–Ir–H 174.9(15).
to 4,4%,6,6%-tetrachloro-2,2%-bibenzylic alcohol with Li-
[AlH4] in diethyl ether in excellent yield. Then, its
hydroxo functionalities were converted to leaving
groups by mesyl chloride in CH2Cl2 using triethylamine
as a base, which yielded considerably better results than
the reaction with tosyl chloride in pyridine [13]. The
reaction of the diol with HBr or PBr3 was also studied,
but did not prove better than introducing the mesyl
group. The dimesylate was subsequently reacted with a
0.5 M stock solution of potassium diphenylphosphide
in THF at low temperature (−78°C) to give the desired
diphosphine in moderate yield. Recrystallisation from
ethanol gave a colorless, analytically pure powder.
Direct sulfonation of the racemic ligand was per-
formed as previously described [11], using fuming sulfu-
ric acid with
a content of free SO3 of 30%.
Reversed-phase HPLC experiments showed that a sin-
gle product had formed, accompanied only by small
amounts (about 6%) of the phosphine oxide of the
sulfonated species. Comparison of its retention time
under the conditions used with authentic samples of
other two- to eightfold sulfonated ligands of the TPP-,
BISBI- and NAPHOS type allowed the conclusion that
the product bears two sulfonato groups. As the tetra-
chlorobiphenyl backbone of the ligand is stable against
electrophilic substitution by sulfonato groups (the start-
ing material 4,4%,6,6%-tetrachlorodiphenic acid is recrys-
tallized from concentrated sulfuric acid at 150°C), the
substitution must take place at the phenyl rings of the
diphenylphosphino moieties. Assuming a uniform dis-
tribution of the sulfonato groups over the phenyl rings,
2.2. Synthesis and structure of an
iridium–BIPHLOPHOS complex
The complex IrH(CO)(TPP)L2 6 (TPP=P(C6H5)3,
L2=5) was synthesized as a stable model substance for
the catalytically active rhodium hydrido dicarbonyl
complex. When equimolar amounts of IrH(CO)(TPP)3
and 5 were stirred in CH2Cl2 overnight, a complete
exchange of two TPP ligands with 5 occurred. After
washing with methanol, the pure complex 6 could be
isolated as a yellow solid. Crystallisation from CH2Cl2/
pentane yielded crystals suitable for X-ray analysis
(Fig. 1). The ligand spans two equatorial positions in
the trigonal bipyramidal complex. The third equatorial
position is taken by triphenylphosphine, whereas the
two apical positions are taken by a hydrido and a CO
Table 1
Comparison of bond angles of IrH(CO)(TPP)L2 (L2=5) and
RhH(CO)(TPP)L2 (L2=BISBI) (P1, P2, P3 numbered as in Fig. 1)
Bond angles (°)
IrH(CO)(TPP)L2 (L2=5)
RhH(CO)(TPP)L2 (L2=BISBI)
P(1)–Ir–P(2)
P(1)–Ir–P(3)
P(2)–Ir–P(3)
124.23(2)
110.17(2)
121.52(2)
P(1)–Rh–P(2)
P(2)–Rh–P(3)
P(1)–Rh–P(3)
124.8(1)
122.6(1)
108.0(1)

F.A. Rampf et al. / Journal of Organometallic Chemistry 582 (1999) 204–210
207
Table 2
Rhodium-catalyzed hydroformylation of styrenea
Ligand
Solvent
Temperature (°C)
% Convertedb
Regioselectivity i/nc
% ee
BISBI
(9)-5
Sulfonated BISBI
Sulfonated (9)-5
(−)-5
Toluene
Toluene
Toluene/water
Toluene/water
Toluene
40
40
40
40
40
80
56
52
21
16
49
68
4.7
4.4
4.8
4.6
4.5
4.2
–
–
–
–
15
–
(−)-5
Toluene
a Standard conditions: substrate/Rh ratio: 300/1; ligand/Rh ratio: 2/1; pressure: 50 bar (1:1 mixture of H2 and CO); reaction time: 16 h.
b Determined by GC.
c i/n=branched/linear.
the two phosphorus atoms should become stereogenic
centres due to their three different substituents, result-
ing in the formation of eight stereoisomers because of
the chirality of the backbone. However, neither HPLC
nor NMR analysis, as we used them, were capable of
separating the different diastereomers.
the biphenyl backbone. However, the optical induction
of this ligand in the asymmetric hydroformylation of
styrene is inferior to the known diphosphine ligand
NAPHOS, its binaphthyl analogue. In contrast to
NAPHOS, the described ligand shows complete selec-
tivity to a twofold sulfonated product in sulfonation
with fuming sulfuric acid, thus simplifying the analysis
of the product properties enormously. Further work on
the new atropisomeric diphosphine ligand is underway.
2.4. Catalytic performance
The described ligands were tested and compared to
the BISBI ligand in homogeneous and bisphasic (water/
organic) rhodium-catalyzed hydroformylation of
styrene. BISBI and sulfonated BISBI were compared to
the racemic diphosphine 5 and the sulfonated racemic
ligand 5 with respect to their activity and i/n-selectivity.
Subsequently, (−)-5 was tested in the homogeneous
hydroformylation of styrene (Table 2).
The comparison with BISBI showed high similarity
in all cases. Both activity and selectivity for the favored
product hydratropaldehyde compare very well. Only
the activity of sulfonated 5 is somewhat lower than that
of sulfonated BISBI. When the nonracemic diphos-
phine (−)-5 was used at temperatures up to 40°C, an
enantiomeric excess of 15% of (S)-hydratropaldehyde
could be observed, whereas only racemic product was
detected, when the reaction was conducted at 80°C.
This compares to 34% ee obtained with enantiopure
NAPHOS under very similar conditions [8]. So the
asymmetry of the binaphthyl backbone in NAPHOS
seems to have a more pronounced effect on the optical
induction than that of the substituted biphenyl back-
bone. This can reasonably be attributed to its higher
steric constraint.
4. Experimental
All reactions were carried out using standard Schlenk
technique in an oxygen-free nitrogen atmosphere. Sol-
vents were dried with standard methods and distilled
under nitrogen. IR spectra were recorded on a Perkin–
Elmer 1600 series FT-IR spectrometer, the 1H-, 13C-
and 31P-NMR spectra on a Jeol JNM GX 400 or a
Bruker AMX 400 instrument. Optical rotations were
measured on a Perkin–Elmer 241 polarimeter. The
purity of the sulfonated ligand was checked by re-
versed-phase HPLC on a C18-modified silica column
with UV detection and elution in gradient mode (H2O–
MeOH). The number of sulfonato-groups in the
product was determined by comparison with authentic
samples of two- to eightfold sulfonated derivatives of
triphenylphosphane, BISBI and NAPHOS with respect
to their retention times. Enantiomeric excesses of the
aldehydes were measured on a Chrompack CP 9000 gas
chromatograph (50 m Lipodex A column, carrier gas:
Helium, split injector, flame ionisation detector) after
reduction to the corresponding alcohols. Their absolute
configuration was determined by comparison with an
authentic sample of (R)-(+)-2-phenylpropanol. Hydro-
formylation experiments were performed in a Parr 300
ml stainless-steel autoclave, using dried and degassed
styrene and a 1:1 mixture of hydrogen and carbon
monoxide. Elemental analyses were carried out in the
microanalytical laboratory of our institute.
3. Conclusion
As compared to the racemic ligand BISBI, the coor-
dination behaviour of the new ligand BIPHLOPHOS
remains basically unaffected by the ortho substituents in

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F.A. Rampf et al. / Journal of Organometallic Chemistry 582 (1999) 204–210
4.1. Resolution of (9)-4,4%,6,6%-tetrachlorodiphenic
acid 1
mmol) of LiAlH4 in diethyl ether was added in portions.
Then, the mixture was allowed to warm to room temper-
ature and was stirred over night. After hydrolysis with
water and 10% H2SO4, the aqueous phase was extracted
with three portions of ether and the combined organic
phases washed with a saturated brine solution and dried
over MgSO4. After evaporation of the solvent the
product remained as a colorless foam (7.95 g, 22.6 mmol,
94%). [h]2D5=47.3° (c 0.165, CHCl3). IR (KBr, cm−1):
3295 (br, O–H); 2966 (w, aliph. C–H); 1015 (m, C–O).
1H-NMR (CDCl3): 7.47 ppm (s, arom. H, 4H); 4.22 ppm
(dd, CH2, 4H); 2.58 ppm (br, OH, 2H).
(9)-1 was prepared and separated into its enan-
tiomers according to the procedure of Atkinson et al. [16]
[17]. A boiling solution 22.6 g (79.2 mmol) of (+)-dehy-
droabietylamine (Merck–Schuchardt, 95%) in 360 ml of
95% ethanol was rapidly added to a boiling solution of
30 g (79.2 mmol) of (9)-1 in ethanol. The mixture was
boiled for an additional 10 min and then cooled to room
temperature in a covered Erlenmeyer flask, whereupon
a large amount of colorless needles precipitated. This was
collected on a Bu¨chner funnel and thoroughly washed
with ethanol and dried in vacuo to yield 10.6 g (15.9
mmol, 70.6%) of the dehydroabietylamine salt of (−)-1.
[h]2D5=38.6° (c 0.7, methanol). Anal. Found: H, 5.64; C,
61.08; N, 2.06; C34H37Cl4NO4 Calc.: H, 5.60; C, 61.36;
N, 2.10%. All mother liquors and washings were col-
lected and evaporated for the isolation of (+)-1 via the
brucine salt as described in the literature.
4.4. (+)-4,4%,6,6%-Tetrachloro-2,2%-
bis(methanesulfonatomethyl)-1,1%-biphenyl 4
A total of 7.95 g (22.6 mmol) of 3 was dissolved in 150
ml of CH2Cl2. After 5.5 g (54.3 mmol) of triethyl amine
had been added, the mixture was cooled to −40°C and
a solution of 5.7 g (49.6 mmol) of methanesulfonic acid
chloride was added from a dropping funnel. Stirring was
continued at −30°C for 1 h, before the reaction mixture
was washed with 250 ml of cold 1 N HCl, three 100 ml
portions of cold water and 100 ml of saturated brine
solution. The organic phase was dried over MgSO4 at
−30°C before the solvent was evaporated at room
temperature. The resulting colorless oil crystallized after
standing in the fridge overnight (10.6 g, 20.9 mmol, 92%).
[h]D25=36.2° (c 0.77, CHCl3). [h]2D5=65.4° (c 0.673,
C6H6). m/z=352, 333, 317, 297, 282, 267, 246, 233, 207.
1H-NMR (CDCl3): 7.57 ppm (d, 3,3%-H, 2 H, J=1.8 Hz);
7.54 ppm (d, 5,5%-H, 2H, J=1.8 Hz); 4.77 ppm (dd, CH2,
4H) 2.89 ppm (s, CH3, 6H). 13C-NMR (CDCl3): 136.0,
135.0, 131.9, 130.3, 128.1, 125.9, 67.4, 37.9 ppm.
Free (−)-1 was prepared from its dehydroabietyl-
amine salt by slowly adding Na2CO3 to 150 ml of an
aqueous suspension of the salt (20 g, 30.0 mmol), covered
by a layer of 150 ml diethyl ether, until the pH of the
aqueous phase reached the value of 10. After separation
of the layers, the aqueous phase was extracted with three
50 ml portions of ether and subsequently stirred at 60°C
until the smell of ether had disappeared. Then, it was
acidified with the calculated amount of 1 N HCl until it
reached pH 2. The colorless precipitate was washed with
water and dried to yield 9.5 g (25 mmol, 83%) of (−)-1.
[h]2D5= −141.4° (c 1.3, CHCl3). M.p. 250–253°C. H-
1
NMR (d6-dmso): 7.96 ppm (d, 3,3%-H, 2H, J=2.1 Hz);
7.93 ppm (d, 5,5%-H, 2H, J=2.1 Hz). 13C-NMR (d6-
dmso): 165.0, 136.5, 134.6, 133.5, 133.3, 132.0, 128.7
ppm. IR (KBr, cm−1): 3500–500 (st, COOH); 1706 (st,
CꢀO). Anal. Found: H, 1.89; C, 44.15; O, 16.98;
C14H6Cl4O4. Calc.: H, 1.6; C, 44.46; O, 16.93%.
4.5. (−)-4,4%,6,6%-Tetrachloro-2,2%-
bis(diphenylphosphinomethyl)-1,1%-biphenyl 5
4.2. (+)-4,4%,6,6%-tetrachlorodiphenic acid chloride 2
A total of 10.6 g (20.9 mmol) of the mesylate 4 was
dissolved in 150 ml of THF and cooled to −78°C. An
83 ml volume of a 0.5 M solution of KPPh2 in THF was
slowly added from a dropping funnel. After stirring for
1 h at −78°C, the mixture was allowed to warm to room
temperature overnight. A 1 ml volume of degassed water
was added and the solvent removed in vacuo, whereupon
the residue was washed thoroughly with toluene. The
toluene washings were gathered and the solvent removed.
Chromatography on silica (pentane/toluene) yielded a
colorless oil, which gave a colorless powder after crys-
tallisation from degassed acetone (4.7 g, 6.82 mmol,
32.7%). [h]2D5= −18.4° (c 0.33, CH2Cl2). m/z: 654, 618,
A total of 9.5 g of (−)-1 was dissolved in 75 ml of
SOCl2 and refluxed for 2 h. After evaporation of SOCl2
in vacuo, the remaining off-white oil was dissolved in
diethyl ether. When the ether was pumped off, the
product remained as a slightly yellow powder (10.0 g,
23.9 mmol, 96%) [h]2D5=21.5° (c 0.233, CHCl3). IR (KBr,
cm−1): 3076 (w, aryl-H); 1758 (st, CꢀO). 1H-NMR
(CDCl3): 8.16 ppm (d, 3,3%-H, 2H, J=1.8 Hz); 7.71 ppm
(d, 5,5%-H, 2H, J=1.8 Hz). 13C-NMR (CDCl3): 165.5,
135.7, 135.5, 135.4, 135.1, 134.8, 131.9 ppm.
1
4.3. (+)-4,4%,6,6%-Tetrachloro-2,2%-bibenzylic alcohol 3
503, 468, 431, 308, 183. H-NMR (C6D6): 7.3–6.8 ppm
(m, aryl-C–H, 24H); 3.20 ppm (dd, CH2, 4H). 13C-NMR
(C6D6): 141.1–125.6 ppm, 35.32 ppm (dd, CH2). 31P-
NMR (C6D6): −13.3 ppm (s).
A total of 10.0 g (24 mmol) was dissolved in diethyl
ether and cooled to −78°C. A suspension of 1.21 g (31.9

F.A. Rampf et al. / Journal of Organometallic Chemistry 582 (1999) 204–210
209
4.6. Synthesis of Ir(H)(CO)(PPh3) 6
All water was removed at the rotary evaporator. Then,
the residue was stirred with 30 ml of degassed methanol
and washed several times with the same solvent. When
the solvent was evaporated, a slightly yellow, glassy
A total of 60 mg (0.087 mmol) of 5 and 88 mg of
Ir(H)(CO)(PPh3)3 was weighed into a Schlenck tube,
dissolved in 5 ml of CH2Cl2 and stirred overnight.
Then, the solvent was pumped off and the yellow
foamy residue washed three times with methanol
(Yield: 78 mg, 0.067 mmol, 76%). Crystals suitable for
X-ray crystallography were obtained from CH2Cl2/pen-
1
solid remained. Yield: 660 mg (0.74 mmol, 84%) H-
NMR (D2O): 7.6–6.7 ppm (m, phenyl- and biaryl-H,
22H); 3.23–3.05 ppm (m, CH2, 4H). 31P-NMR (D2O):
−10.69 ppm (s); 22.3 ppm (s, trace amounts of phos-
phine oxide). HPLC: P(V)/P(III)=5.7%, retention time
comparable to BISBI with two sulfonato groups.
1
tane. H-NMR (C6D6): 7.8–6.8 ppm (m, phenyl- and
biaryl-H, 24H); 4.31–3.51 ppm (m, CH2, 4H); −11.1
ppm (dt, J(H–P3) 16.1 Hz, J(H–P1/P2) 24.2 Hz).
31P-NMR (C6D6): (PPh3: P3; 5: P1 and P2): 8.842 ppm
(dd, J(P3–P2): 124.1 Hz, J(P3–P1): 109.0 Hz), 6.575–
2.854 ppm (m, J(P1–P2): 137.7 Hz). IR (KBr, cm−1):
2068 (m); 1928 (vs). Anal. Found: H, 3.84; C, 58.55; O,
1.32; C57H44Cl4IrOP3. Calc.: H, 3.79; C, 58.46; O,
1.37%.
5. Supplementary material
Crystallographic data (excluding structure factors)
for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre as supplementary publication CCDC No.
113563. Copies of the data may be obtained free of
charge from: The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336-033;
e-mail: teched@chemcrys.cam.ac.uk).
4.7. Crystal data for Ir(H)(CO)(PPh3) 6
(
C57H44Cl4IrOP3, M=1171.8, triclinic, P1, a=
,
,
,
11.2628(1) A, b=15.0054(2) A, c=17.5377(2) A,
h=74.1530(7)°, i=73.1160(6)°, k=70.2764(7), V=
2618.87(5) A , Z=2, zcalc=1.486 g cm−3, F(000)=
3
Acknowledgements
,
1168, v(Mo–Ka)=2.88 mm−1, u=0.71073 A, T=
,
This work was supported by the Bundesministerium
fu¨r Bildung und Forschung (Bonn, Germany), the
Fonds der Chemischen Industrie (Frankfurt, Germany),
Hoechst AG (Frankfurt, Germany), and Celanese
Deutschland GmbH (Oberhausen, Germany). We are
grateful to Petra Ankenbauer and Dipl. Chem. Robert
W. Eckl for experimental assistance and stimulating
discussions.
193(2) K. The 26 520 reflections measured on a Nonius
Kappa CCD area detector diffractometer [18] yielded
12 299 unique data (2qmax=61.08°, Rint=0.047). Pre-
liminary positions of heavy atoms were found by direct
methods [19], while positions of the other non-hydro-
gen atoms were determined from successive Fourier
difference maps coupled with initial isotropic least
square refinement [20]. The hydrogen atoms were
placed in calculated positions. They were included in
the structure factor calculation but not refined. A
highly disordered solvent molecule was dealt with by
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