Rhodium complexes with chiral counterions: Achiral catalysts in chiral matrices

Article abstract of DOI:10.1016/j.jorganchem.2003.12.012

The neutral complexes [Rh(I)(NBD)((1S)-10-camphorsulfonate)] (2) and [Rh(I)((R)-N-acetylphenylalanate)] (4) reacted with bis-(diphenylphosphino)ethane (dppe) to form the cationic Rh(I)(NBD)(dppe) complexes, 5 and 6, respectively, accompanied by their corresponding chiral counteranions. Analogously, 4 reacted with 4,4′-dimethylbipyridine to yield complex 7. Complexes 5 and 6 disproportionated in aprotic solvents to form the corresponding bis-diphosphine complexes 8 and 9, respectively. 8 was characterized by an X-ray crystal structure analysis. In order to form achiral Rh(I) complexes bearing chiral countercations new sulfonated monophosphines 13-16 with chiral ammonium cations were synthesized. Tris-triphenylphosphinosulfonic acid (H₃TPPS, 11) was used to protonate chiral amines to yield chiral ammonium phosphines 14-16. Thallium-tris-triphenylphosphinosulfonate (Tl₃TPPS, 12) underwent metathesis with a chiral quartenary ammonium iodide to yield the proton free chiral ammonium phosphine 13. Phosphines 15 and 16 reacted with [Rh(NBD)₂]BF₄ to afford the highly charged chiral zwitterionic complexes [Rh(NBD) (TPPS)₂][(R)-N, N-dimethyl-1-(naphtyl)ethylammonium] ₅ (17) and [Rh(NBD)(TPPS)₂][BF₄] [(R)-N, N-dimethyl-phenethylammonium]₆ (18), respectively. Complexes 5, 6, and 18 were tested as precatalysts for the hydrogenation of de-hydro-N-acetylphenylalanine (19) and methyl-(Z)-(α) -acetoamidocinnamate (MAC, 20) under homogeneous and heterogeneous (silica-supported and self-supported) conditions. None of the reactions was enantioselective.

Full text of DOI:10.1016/j.jorganchem.2003.12.012

Journal of Organometallic Chemistry 689 (2004) 751–758
www.elsevier.com/locate/jorganchem
Rhodium complexes with chiral counterions: achiral catalysts
in chiral matrices
a,
Romano Dorta , Linda Shimon , David Milstein
b
a,
*
*
a
Department of Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
b
Department of Chemical Services, The Weizmann Institute of Science, 76100 Rehovot, Israel
Received 21 September 2003; accepted 1 December 2003
Abstract
The neutral complexes [Rh(I)(NBD)((1S)-10-camphorsulfonate)] (2) and [Rh(I)((R)-N-acetylphenylalanate)] (4) reacted with bis-
diphenylphosphino)ethane (dppe) to form the cationic Rh(I)(NBD)(dppe) complexes, 5 and 6, respectively, accompanied by their
(
0
corresponding chiral counteranions. Analogously, 4 reacted with 4,4 -dimethylbipyridine to yield complex 7. Complexes 5 and 6
disproportionated in aprotic solvents to form the corresponding bis-diphosphine complexes 8 and 9, respectively. 8 was charac-
terized by an X-ray crystal structure analysis. In order to form achiral Rh(I) complexes bearing chiral countercations new sulfonated
monophosphines 13–16 with chiral ammonium cations were synthesized. Tris-triphenylphosphinosulfonic acid (H3TPPS, 11) was
used to protonate chiral amines to yield chiral ammonium phosphines 14–16. Thallium-tris-triphenylphosphinosulfonate (Tl3TPPS,
1
2) underwent metathesis with a chiral quartenary ammonium iodide to yield the proton free chiral ammonium phosphine 13.
Phosphines 15 and 16 reacted with [Rh(NBD)2]BF4 to afford the highly charged chiral zwitterionic complexes
Rh(NBD)(TPPS)2][(R)-N,N-dimethyl-1-(naphtyl)ethylammonium]5 (17) and [Rh(NBD)(TPPS)2][BF4][(R)-N,N-dimethyl-phene-
[
thylammonium]6 (18), respectively. Complexes 5, 6, and 18 were tested as precatalysts for the hydrogenation of de-hydro-N-acet-
ylphenylalanine (19) and methyl-(Z)-(a)-acetoamidocinnamate (MAC, 20) under homogeneous and heterogeneous (silica-supported
and self-supported) conditions. None of the reactions was enantioselective.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Rhodium; Chiral counterions; Catalysis; Hydrogenation
1
. Introduction
combination with steroid derived surfactants gave up to
.5% ee in the hydrogenation of de-hydro-aminoacids [5]
8
In the 1980s chiral ammonium salts were shown to
while aziridinations and cyclopropanations catalyzed by
achiral Cu complexes associated with chiral binaphtol
based counteranions gave up to 28% ee [6]. In view of
our interest in ordered catalytic systems [7] we set out
to achieve crystalline precatalysts chirally modified by
counterions. We disclose here the synthesis and char-
acterization of new chiral ammonium salts of sulfonated
monophosphines and rhodium complexes thereof. The
resulting cationic and anionic rhodium complexes are
associated, respectively, with chiral counteranions and
chiral countercations forming the chiral matrix. The
potential of such highly charged rhodium salts as
Ômolecular solid state organometallic catalystsÕ [8] is
explored, since their extremely low solubility in the re-
action medium fulfills one of the basic prerequisites of
heterogeneous self-supported catalysis. We present the
act as enantioselective phase transfer catalysts in a
number of organic transformations [1,2] and recently
optical yields of up to 99% have been achieved [3].
Moreover, it was demonstrated that chiral spectator
ions also induce chirality in the course of reactions
catalyzed by achiral metal complexes. Achiral Pd com-
plexes in the presence of cinchonidinium alkaloids led to
enantioselectivities of up to 8% ee in allylic alkylation
reactions [4]. The use of achiral rhodium catalysts in
*
Corresponding authors. Present address of RD: Departamento de
Qu ꢀı mica, Universidad Sim oꢀ n Bol ꢀꢁ var, Sartenejas-Baruta, Caracas
080A, Venezuela. Fax: +58-0-212-906-3961.
1
E-mail addresses: rdorta@usb.ve (R. Dorta), david.milstein@
weizman.ac.il (D. Milstein).
0
022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.12.012

752
R. Dorta et al. / Journal of Organometallic Chemistry 689 (2004) 751–758
results of catalytic hydrogenations of prochiral de-hy-
dro-aminoacids that were performed in homogeneous
solution, supported on silica gel, and without support.
Ph2
P
+
MeOH
Rh(NBD)
2
+
dppe
P
Ph2
ð3Þ
O
SO3-
5
2
. Results and discussion
Compounds 5 and 6 disproportionated in aprotic
2
.1. Complexes containing chiral anions
solvents such as THF according to Eq. (4) yielding
compounds 8 and 9, along with the phosphine free
neutral complexes 2 and 4, respectively. Complexes 8
and 9 were identified by separate high yield syntheses
in methanol solution from 2 equiv of dppe and 2 or 4,
respectively. It was shown recently that the lipophi-
In a first approach to form chiral rhodium salts the
chloride ligand of the precursor [Rh2Cl2(COE)2]
COE ¼ cyclooctene) was exchanged with the silver salts
(
of camphorsulfonate (1) (Eq. (1)) and (R)-acety-
lphenylalanate (3) (Eq. (2)) in presence of an excess of
norbornadiene (NBD) to afford the neutral (1S)-10-
camphorsulfonato and (R)-N-acetylphenylalanato Rh(I)
complexes 2 and 4, respectively. Both complexes were
soluble in aliphatic and ether solvents. Despite using an
excess of NBD in the syntheses of 2 and 4 only mono
NBD complexes of rhodium formed, probably due to
effective bidentate ligation of the camphorsulfonate and
phenylalanate anions, respectively, to the Rh(I) centers.
þ
ꢀ
ꢀ
licity of [Rh(dppe)2] A salts is controlled by modi-
fications of the anion A [9]. X-ray quality crystals of
8
were grown from a THF solution of 5. Fig. 1 shows
its solid state structure with a selection of bond pa-
rameters. The space group was monoclinic Cc (No.9)
with a unit cell of a ¼ 14:736ð3Þ, b ¼ 23:615ð5Þ,
c ¼ 35:138ð7Þ, b ¼ 97:90ð3Þ° with two molecules per
asymmetric unit.
In view of a possible application as self-supported
organometallic catalysts [8], the solubility of compounds
6–8 was tested and was found to be low only in alkanes
and perfluoroalkanes
THF, NBD
[
RhCl(COE)2]2
+
2
2
-
AgCl
ð1Þ
O
O
-
+
SO3 Ag
SO3Rh(NBD)
aprotic
solvent
Ph2 Ph2
P
P
1
2
Rh
A*
2
5, 6
+
(A*)Rh(NBD)
P
P
Ph2 Ph2
-
+
COO Ag THF, NBD
NHAc
-AgCl
COORh(NBD)
8: A* = (1S)-camphorsulfonate 2: A* = (1S)-camphorsulfonate
[
RhCl(COE)2]2 + 2 Ph
2 Ph
9: A* = (S)-N-phenylalanate 4: A* = (S)-N-phenylalanate
NHAc
3
4
ð4Þ
ð2Þ
1
,2-Bis(diphenylphosphino)ethane (dppe) cleanly re-
acted with compounds 2 and 4 in methanol solution to
afford 5 (Eq. (3)) and 6, respectively. Additionally, 4
0
0
reacted with 4,4 -dimethyl-2,2 -dipyridyl giving complex
(see Scheme 1). The outer-sphere-chiral complexes 5–7
formed in excellent isolated yields.
7
Ph2
P
+
COO-
NHAc
Rh(NBD) Ph
P
dppe
MeOH
Ph2
6
4
benzene
+
3
,5 dimethyl
Fig. 1. Structure of complex 8 in the solid state. Selected bond lengths
( Aꢂ ) and angles (°) are as follows: Rh(1)–P(2) 2.280(7), Rh(1)–P(1)
bipyridine
N
COO-
NHAc
Rh(NBD) Ph
2
.290(7), Rh(1)–P(3) 2.293(8), Rh(1)–P(4) 2.317(8), S(2)–O(7) 1.4239,
N
S(2)–O(5) 1.4339, S(2)–O(6) 1.4896, S(2)–C(301) 1.7865, P(1)–Rh(1)–
P(2) 97.5(2), P(1)–Rh(1)–P(3) 81.9(3), P(2)–Rh(1)–P(4) 83.0(3), P(3)–
Rh(1)–P(4) 100.1(2), O(7)–S(2)–O(5) 117.3, O(7)–S(2)–O(6) 110.6,
O(5)–S(2)–O(6) 111.3, O(7)–S(2)–C(301) 104.7, O(5)–S(2)–C(301)
111.1, O(6)–S(2)–C(301) 100.3.
7
Scheme 1.

R. Dorta et al. / Journal of Organometallic Chemistry 689 (2004) 751–758
753
2.2. Sulfonated phosphine ligands containing chiral ca-
tions
the presence of three conformers, each of them dis-
playing a doublet at a different chemical shift.
Cinchonidine and its derivatives [11,12] and 1-
(naphtyl)ethylamine (NEA) [13,14] were shown to be
powerful chiral modifiers in heterogeneously catalyzed
reactions [15]. Therefore, phosphine 11 was used to di-
rectly protonate chiral amines such as hydroquinidine,
(R)-NEA, and (R)-phenethylamine giving compounds
14–16 (see Scheme 2). These reactions were carried out
on gram scales and in excellent yields. Compounds 10–
16 are water soluble [16].
In order to improve the chiral matrix (i.e. to augment
the number of chiral units per rhodium atom) we decided
to modify the commercially available monophosphine
sodium-tris-triphenylphosphinosulfonate (Na TPPS, 10)
3
by exchanging the sodium ion for chiral ammonium
ions [10]. Direct ion exchange of 10 with (R)-N,N,N-tri-
methyl-1-phenethylammonuim iodide under varying
conditions failed. The exchange via the Ag3TPPS salt
was not possible either since Ag3TPPS was not accessible
from 10 by different exchange methods. However, the
strongly acidic Dowex-50W ion exchange resin allowed
to exchange the sodium cations with protons (Eq. (5)) on
a gram scale in excellent yields. Surprisingly, the NMR
spectrum of 11 in CD3OD did not reveal the presence of
phosphonium species. Reactions of phosphine 11
with Ag2O gave inseparable mixtures, presumably due
to the formation of silver–phosphine complexes. On
the other hand, 11 reacted cleanly with thalliumethoxyde
in ethanol solution to afford thallium-tris-triphenyl-
2.3. Complexes containing chiral cations
With phosphine ligands 13–16 at hands, we undertook
complexation studies in order to synthesize achiral rho-
dium complexes with chiral countercations. Ligands 13
and 16 were reacted with [RhCl(COE) ] in a ratio of 6:1
2
2
to afford mainly the corresponding WilkinsonÕs catalysts
along with dimeric species and unreacted ligand. Un-
fortunately, these mixtures were inseparable. Hydro-
quinidinium phosphine ligand 14 did not react cleanly
neither with [RhCl(COE) ] nor with [Rh(NBD) ]BF in
phosphinosulfonate (Tl TPPS, 12). Reacting 12 with
3
2
2
2
4
N,N,N-trimethyl-1-phenethylammonuim iodide finally
led to the desired ammonium phosphine 13 (Eq. (6))
along with precipitated TlI
varying stoichiometries and solvents. In general, we
found it difficult to separate and purify mixtures of these
highly ionic species. However, ligands 15 and 16 reacted
cleanly with [Rh(NBD) ]BF in methanol solution to
2
SO3Na
SO3H
4
DOWEX-50W
H - form
afford fivefold negatively charged zwitterionic complexes
7 and 18, respectively, in excellent isolated yields (Eq.
7)). Charge-neutral zwitterionic Rh(I) complexes have
P
+
P
1
(
NaO3S
CH3OH
HO3S
SO3Na
SO3H
been shown to catalyze various transformations [17–20].
Complexes 17 and 18 were found to be soluble in protic
solvents including water and to be insoluble in aliphatic,
aromatic, and notably in ether solvents such as THF. We
note that washing complex 17 with THF effectively re-
moved one mole of the [(R)-N,N-dimethyl-1-(1naph-
tyl)ethylammonium]BF4 salt. Surprisingly, this did not
happen with complex 18.
10
11
ð5Þ
N
N
TlO3S
SO3
I
P
Tl(OEt)
11
P
O3S
TlO3S
SO3
SO3
H
N
SO3Tl
N
[
Rh(NBD)2]BF4
+
2 P
N
12
13
R
3
ð6Þ
Phosphines 12 and 13 were prepared in excellent yields
1
1
5 (R = naphtyl)
6 (R = phenyl)
1
and on gram scales. In the H NMR spectrum 13 re-
3
O S
BF4
ð7Þ
H
N
n
vealed an apparent doublet of triplets (dt) at 1.72 ppm
attributed to the methyl group adjacent to the stereo-
genic carbon atom. Concentration effects were excluded.
Irradiating the protons of this methyl group caused the
quartet at 4.69 ppm (H on stereogenic C atom) to dis-
appear, whereas the aromatic region of the ortho-pro-
tons of the N,N,N-trimethyl-1-phenethylammonuim
cation remained unchanged. It is thus concluded that
3
CH3OH
- NBD
R
P
m
Rh
P
SO3
3
1
1
7 (R = naphtyl, m = 5, n = 0)
8 (R = phenyl, m = 6, n = 1)
Complexes 17 and 18 differ in several ways from
Ôfirst generationÕ complexes such as 5–9 containing
chiral counteranions. First, chiral countercations are
5
there is no J coupling between the methyl protons and
the aromatic ortho-protons. The dt may be explained by

754
R. Dorta et al. / Journal of Organometallic Chemistry 689 (2004) 751–758
1
1
HO
N
N
N
N
SO3
SO3
SO3
H
N
H
P
HO
P
P
N
N
H
N
3
3
3
14
15
16
Scheme 2.
non-coordinating, especially considering the cationic
nature of the rhodium centers. Second, complexes 17
and 18 form highly charged species, thus effectively
lowering the solubility in aprotic solvents which is an
important prerequisite when complexes are to be used as
truly heterogeneous, ‘‘self-supported’’ organometallic
species [8]. Finally, the high number of chiral counteri-
ons in 17 and 18 (five and six, respectively) leads to a
denser chiral matrix. Unfortunately, 17 and 18 were
only isolated as amorphous powders.
coordination of the camphorsulfonato and the acety-
ꢀ
lphenylalanato anions, respectively, as compared to BF .
4
Under unsupported heterogeneous conditions in pentane
or perfluorohexane solvents, 5 mol% of 6 and 7 hydro-
genated methyl-(Z)-a-acetoamidocinnamate (MAC, 20)
in 70–80% yield in 24 h without enantioselectivity (0% ee,
determined by chiral HPLC [22]). The mother liquors
were not catalytically active and rhodium concentrations
ꢀ
4
determined by ICP were less than 10 mol%. Neverthe-
less, we believe that the observed catalytic activity is due
to the presence of small amounts of dissolved complex
since the highly ionic and ÔtrulyÕ insoluble catalyst pre-
cursors 17 and 18 showed no activity under similar con-
ditions (vide infra). Complexes 2 and 4 were not stable
under hydrogenation conditions forming metallic rho-
dium precipitate. Complex 18 was tested in different forms
for the hydrogenation of MAC (see Table 1).
Ligand 13 and complex 17 were grafted via H-
Ò
bonding onto Merck 60 silica using BianchiniÕs method
Ò
[
20] in amounts of 0.10 mmol/g (Merck 60 ) and 0.14
Ò
mmol/g (Merck 60 ), respectively. Qualitatively, slight
leaching of 17 was observed in CH2Cl2 and no leaching
was detected in toluene and THF, whereas it strongly
leached in protic solvents.
COOR
H2
*
COOR
Ph
Ph
2
.4. Catalytic hydrogenations
NHAc
NHAc
ð8Þ
1
2
9 (R = H)
0 (R = CH3)
21 (R = H)
22 (R = CH3)
The Ôfirst generationÕ catalysts 5 and 6 were tested in the
hydrogenation of de-hydro-N-acetylphenylalanine (19,
Eq. (8)). In homogeneous phase at 273 K no enantiose-
lection was observed and 5 and 6 were ca. half as active as
the reference system [Rh(dppe)(NBD)]BF4 [21]. The
lower activity of 5 and 6 is probably due to the stronger
The fivefold negatively charged zwitterionic complex 18
was indeed an active hydrogenation catalyst (entry 1).
However, in none of the experiments was any significant
enantioselection observed. In the unsupported solid state
Table 1
Catalytic hydrogenation of 20 (0.05–0.5 M) at RT using 5 mol% of catalyst precursor 18
a
Entry
Form
Solvent
CH Cl
Reaction time
p(H
2
) (bar)
Yield (%)
1
2
3
4
5
6
7
Solution
Powder
2
2
20 min
18 h
3 h
1
6
6
6
6
5
5
72
0
Toluene
Toluene
Powder
Powder
2
Toluene/THF
Toluene/THF
Toluene
18 h
18 h
18 h
18 h
0.2
3.4
Ground powder and ultrasound
Immobilized on Merck-60
Immobilized on Merck-60
b
26
21
b
THF
a
Determined by NMR and HPLC.
Mother liquors were catalytically inactive.
b

R. Dorta et al. / Journal of Organometallic Chemistry 689 (2004) 751–758
755
only very finely ground 18 in combination with ultra
sonication during the reaction exhibited some activity
docinnamic acid (20, Aldrich) was recrystallized from
water, dried in vacuo at 373 K, and kept in the glove
box. MAC (21) was synthesized by reacting a methanol
solution of 20 with a CH2N2 solution in Et2O at 273 K.
[RhCl(COE)2]2, [Rh(NBD)2]BF4, [Ag((1S)-10-cam-
phorsulfonate] (1) [25] were prepared according to
published procedures. All reactions involving Ag com-
pounds were carried out in the dark. The syntheses were
routinely carried out in a glove box. NMR spectra were
recorded on a Bruker DPX-250 spectrometer. Optical
rotations were measured on a AVIV-202 polarimeter.
Elemental analyses were performed at the microanalyt-
ical laboratory of the Hebrew University, Jerusalem.
Caution: The Tl containing compounds described here
are water soluble and highly toxic.
Ò
(
entry5). Complex18dispersedonMerck60 (0.14mmol/
g) (entries 6, 7) turned out to be a relatively active catalyst
system. The apparently higher activity of the unsupported
‘
‘heterogeneous’’ systems 6 and 7 as compared to unsup-
ported 18 may be explained by the significantly higher
solubilities of 6 and 7 in the reaction media and thus by a
homogeneous contribution to the overall reactivity. In
contrast, 18 apparently formed a ÔtrulyÕ heterogeneous
system. It seems therefore that a negative activity test of
the mother liquor of a given heterogeneous catalyst system
is not sufficient a proof for its heterogeneicity.
3
. Conclusions
4.2. [Rh((1S)-10-camphorsulfonate)(NBD)] (2)
New chiral ammonium sulfonato phosphine ligands
3–16 as well as achiral rhodium complexes with chiral
1
NBD (0.25 ml) was added dropwise to a stirred slurry
counteranions (5–7) and countercations (17, 18) were
synthesized and characterized. The cationic complexes 5
and 6, and, notably, the pentaanionic complex 18 effec-
tively hydrogenated prochiral de-hydro-aminoacids un-
der homogeneous and silica-supported conditions.
However, none of the aforementioned complexes induced
chirality. The zwitterionic complexes 17 and 18 showed
extremely low solubilities in aprotic solvents such as THF,
which is a prerequisite for truly heterogeneous self-sup-
ported catalyst systems. Unfortunately, these complexes
did not catalyze the hydrogenation of MAC (20) under
self-supported conditions, although the use of very fine
powders may improve activities (entry 5 of Table 1). The
immobilization of catalyst precursor 18 via H-bonding on
silica gel proved promising from a reactivity and recy-
clability standpoint. Future efforts will be directed at
synthesizing clean complexes of ligand 14 which contains
the most promising chiral modifier. The confinement of
such catalyst precursors within well defined mesoporous
silica may lead to enantioselective systems [23,24] which is
the object of future studies. On the other hand, the use of
microcrystalline material instead of amorphous powders
of [Rh2Cl2(COE)4] (255 mg, 0.355 mmol) in THF (5 ml).
The resulting dark yellow solution was stirred for 20
min. Then [Ag((1S)-10-camphorsulfonate] (1, 253 mg,
0.711 mmol) was added portionwise and the resulting
mixture was stirred for 24 h. The volatiles were removed
in vacuo and the residue was taken up in CH2Cl2 (5 ml).
The mixture was filtered through Celite and the solution
was evaporated to dryness. Washing the solid with cold
Et2O and drying in vacuo afforded a yellow powder
(246 mg, 81%). Elemental analysis (calculated for
C H SO Rh): C, 47.82 (47.89); H, 5.39 (5.44)%.
1
7
23
4
4.3. [Ag((S)-N-acetylphenylalanate)] (3)
A slurry of (S)-N-acetylphenylalanine (2.410 g,
11.630 mmol) in CH3CN (40 ml) was added to solid
Ag2O (1.348 g, 5.815 mmol) and the mixture was stirred
for 24 h. The resulting white precipitate was filtered off,
washed with Et O (2 ꢁ 40 ml), and dried in vacuo af-
2
fording a white powder (3.47 g, 95%). Elemental anal-
ysis (calculated for C H NO Ag): C, 41.80 (42.06); H,
1
1
12
3
1
3.91 (3.85); N, 4.73 (4.46)%. H NMR (CD3OD): d 1.85
(s, 3 H), 2.80–2.95 (m, 1 H), 3.10–3.25 (m, 1 H), 4.45–
4.55 (m, 1 H), 7.05–7.20 (m, 5 H).
(
of, e.g., 17 or 18) is another strategy, since the chiral order
on a crystalline catalyst surface may impart enanti-
oselectivity. Such crystalline self-supported organome-
tallic catalysts must remain stable under the reaction
conditions. For example, microcrystals of compound 8
4.4. [Rh((S)-N-acetylphenylalanate)(NBD)] (4)
collapsed under 1 bar of H thus destroying any order that
2
NBD (0.25 ml) was added dropwise to a stirred slurry
of [Rh Cl (COE) ] (295.1 mg, 0.4115 mmol) in THF (5
may have been present on the crystal surfaces.
2
2
4
ml). The resulting dark yellow solution was stirred for
0 min. Then [Ag((R)-acetylphenylalanate)] (3, 258.8
2
4
. Experimental
mg, 0.8240 mmol) was added portionwise and the re-
sulting mixture was stirred for 24 h. The volatiles were
removed in vacuo and the residue was taken up in
CH Cl (5 ml). The mixture was filtered through Celite
4
.1. General considerations
2
2
(
S)-N-acetylphenylalanine (Aldrich), chiral amines,
and the solution was evaporated to dryness. Washing
the solid with cold Et O and drying in vacuo afforded a
1
0, TlOEt (Strem), were used as received. a-Acetami-
2

756
R. Dorta et al. / Journal of Organometallic Chemistry 689 (2004) 751–758
1
yellow powder (284 mg, 86%). Elemental analysis (cal-
(5.59); N, 7.25 (7.07)%. H NMR (CD3OD): d 1.50 (m, 2
H), 1.84 (s, 3 H), 2.53 (s, 6 H), 2.80–2.95 (m, 1 H), 3.10–
3.25 (m, 1 H), 4.00–4.10 (m, 2 H), 4.40–4.45 (m, 4 H),
4.45–4.55 (m, 1 H), 7.05–7.20 (m, 5 H), 7.40–7.45 (m, 2
H), 7.55–7.60 (m, 2 H), 8.19 (s, 2 H).
culated for C18H20NO3Rh ꢂ 0.5C4H10O): C, 55.14
1
(
(
54.80); H, 5.40 ](5.75); N, 2.80 (3.20)%. H NMR
CD3OD): d 1.29 (s, br, 2 H), 1.81 (s, 3H), 2.55–2.65 (m,
1H), 2.75–2.85 (m, 1H), 4.01 (s, br, 4 H), 4.11 (s, br, 2
H), 4.20–4.30 (m, 1 H), 7.00–7.25 (m, 5 H). The spec-
trum showed the presence of 0.5 equiv of Et O.
2
4
.8. [Rh(dppe) ][(1S)-10-camphorsulfonate)] (8)
2
4
.5. [Rh(dppe)(NBD)][(S)-10-camphorsulfonate] (5)
A solution of dppe (281.9 mg, 0.708 mmol) in
CH3OH (7 ml) was added dropwise to a stirred solution
of [Rh((1S)-10-camphorsulfonate)(NBD)] (2, 150.2 mg,
0.352 mmol) in CH3OH (4 ml). The resulting orange
solution was stirred for 2 h. The volatiles were evapo-
A solution of dppe (138.1 mg, 0.346 mmol) in
CH3OH (4 ml) was added dropwise to a stirred solution
of [Rh((1S)-10-camphorsulfonate)NBD] (148.2 mg,
0.348 mmol) in CH OH (4 ml). The resulting orange
3
solution was stirred for 6 h and then stripped to an
rated and the solid was washed and slurried in Et O (15
2
ml). Drying in vacuo afforded an orange powder (366
31
orange solid. Slurrying and washing with Et O (8 ml)
2
mg, 92%). P NMR (CD OD): d 56.4 (d, J
Hz). H NMR (CD3OD): d 0.82 (s, 3 H), 1.09 (s, 3 H),
¼ 133
3
Rh–P
afforded a yellow powder (274 mg, 96%). Elemental
1
analysis (calculated for C43H47SO4P2Rh ꢂ H2O): C,
1
.30–1.50 (m, 1 H), 1.50–1.60 (m, 1 H), 1.87 (d, J ¼ 18
31
6
5
0.97 (61.28); H, 5.82 (5.86)%. P NMR (CD3OD): d
Hz, 1 H), 1.90–2.10 (m, 2 H), 2.19 (m, 8 H), 2.31 (d of m,
J ¼ 18 Hz, 1 H), 2.50–2.70 (m, 1 H), 2.73 (d, J ¼ 15 Hz, 1
H), 3.28 (d, J ¼ 15 Hz, 1 H), 7.15–7.40 (m, 40 H). X-ray
quality single crystals of 8 were grown from a concen-
trated and filtered THF solution of 5.
1
4.5 (d, JRh–P ¼ 157.0 Hz). H NMR (CD3OD): d 0.82
(
s, 3 H), 1.09 (s, 3 H), 1.30–1.50 (m, 1 H), 1.50–1.60 (m,
1
(
J
H), 1.80 (s, 2 H), 1.86 (d, J ¼ 18 Hz, 1 H), 1.90–2.10
m, 2 H), 2.31 (d of m, J ¼ 18 Hz, 1 H), 2.41 (d,
¼ 28.1 Hz, 4 H), 2.50–2.70 (m, 1 H), 2.73 (d, J ¼ 15
H–P
Hz, 1 H), 3.28 (d, J ¼ 15 Hz, 1 H), 4.14 (m, 2 H), 5.36
m, 4 H), 7.50–7.65 (m, 20 H).
4
.9. [Rh(dppe)
2
][(S)-N-acetylphenylalanate] (9)
(
A solution of dppe (164.4 mg, 0.413 mmol) in
CH3OH (4 ml) was added dropwise to a stirred solution
4
.6. [Rh(dppe)(NBD)][(S)-N-acetylphenylalanate] (6)
of [Rh((S)-N-acetylphenylalanate)(NBD)] (4, 82.5 mg,
0
A solution of dppe (320.2 mg, 0.804 mmol) in
CH OH (8 ml) was added dropwise to a stirred solution
.206 mmol) in CH OH (2 ml). The resulting orange
3
3
solution was stirred for 6 h and then stripped to an
orange solid which was dried in vacuo. Elemental
analysis (calculated for C63H60NO3P4Rh ꢂ 2CH3OH): C,
of [Rh((S)-N-acetylphenylalanate)(NBD)] (323.5 mg,
0
solution was stirred for 6 h and then stripped to an
orange solid. Slurrying and washing with Et2O (16 ml)
afforded a yellow powder (598 mg, 93%). Elemental
analysis (calculated for C44H44NO3P2Rh): C, 67.88
.806 mmol) in CH3OH (8 ml). The resulting orange
3
1
6
6.74 (66.72); H, 5.80 (5.86); N, 0.80 (1.20)%. P NMR
1
(
(
CD3OD): d 56.3 (d, JRh–P ¼ 133 Hz). H NMR
CD3OD): d 1.84 (s, 3 H), 2.19 (m, 8 H), 2.91 (m, 1 H),
66.09); H, 5.46 (5.55); N, 0.82 (1.75)%. 31P NMR
3.19 (m, 1 H), 4.50 (m, 1 H), 7.10–7.45 (m, br, 45 H).
4.10. TPPS-H (11)
(
(
(
CD OD): d 54.9 (d, JRh–P ¼ 157.0 Hz). 1H NMR
3
CD OD): d 1.80 (s, 2 H), 1.84 (s, 3 H), 2.42 (d,
3
3
JH–P ¼ 28.1 Hz, 4 H), 2.89 (m, 1 H), 3.17 (m, 1 H), 4.16
(
m, 2 H), 4.48 (m, 1 H), 5.38 (m, 4 H), 7.10–7.20 (m, 5
H), 7.50–7.65 (m, 20 H).
A solution of TPPS-Na3 (1018 mg, 1.791 mmol) in
CH3OH (5 ml) and water (3 ml) was applied to a con-
ditioned DOWEX-50W acid ion exchange column
(d ¼ 1 cm, l ¼ 10 cm, CH3OH) and eluted with CH3OH
(80 ml). The solution was pumped down to a golden
syrup and dried in vacuo overnight. Slurrying and
washing with Et2O (3 ꢁ 15 ml) and drying in vacuo af-
forded a white fine powder (800 mg, 87%). Elemental
analysis (calculated for C18H15O9PS3): C, 42.85 (43.03);
0
0
4.7. [Rh(4,4 -dimethyl-2,2 -dipyridyl)(NBD)][(R)-acet-
ylphenylalanate] (7)
0
0
A solution of 4,4 -dimethyl-2,2 -dipyridyl (97.0 mg,
.526 mmol) in benzene (4 ml) was added dropwise to a
0
stirred solution of [Rh((S)-N-acetylphenylalanate)
NBD)] (4, 207.0 mg, 0.516 mmol) causing the forma-
1
(
H, 2.94 (3.01)%. H NMR (CD3OD): d 7.30–7.45 (m,
6H), 7.80–7.90 (m, 6H). The acid protons are not ac-
tion of a red oily precipitate. This mixture was stirred
for 6 h, evapaorated to dryness, washed and slurried in
Et O (10 ml), and dried in vacuo to afford a red powder
31
1
counted for due to D–H scrambling.
P{ H}
NMR(CD3OD): d )5.48 (s), an impurity at 29.0 ppm
amounts usually to <5% by integration and is already
present in commercial TPPS-Na3.
2
(
275 mg, 91%). Elemental analysis (calculated for
C H N O Rh ꢂ 0.5H O): C, 60.40 (60.61); H, 5.32
3
0
32
3
3
2

R. Dorta et al. / Journal of Organometallic Chemistry 689 (2004) 751–758
757
4
.11. TPPS-Tl
3
(12)
hydroquinidine (628.2 mg, 1.924 mmol) in CH2Cl2 (10
ml). The resulting colorless solution was stirred over-
night and then evaporated to a glassy solid. Slurrying
and washing in Et2O (10 ml) afforded 860 mg (91%) of a
finely divided white powder. Elemental analysis (calcu-
lated for C H N O PS ): C, 63.15 (63.23); H, 6.41
A solution of TPPS-H3 (351 mg, 0.694 mmol) in
EtOH (8 ml) was added to TlOEt (519 mg, 2.08 mmol)
and EtOH (2 ml) causing immediate precipitation of a
white solid. The mixture was stirred for 48 h. The white
solid was filtered off, washed with EtOH (20 ml), and
dried in vacuo affording a fine white powder (730 mg,
7
8
93
6
15
1
3
(6.33); N, 5.66 (5.67)%. H NMR (CD OD): d 0.85–0.95
3
(m, 9 H), 1.10–1.20 (m, 3H), 1.50–1.60 (m, 6H), 1.70–
1,90 (m, 12H), 2.30–2.40 (m, 3H), 3.05–3.20 (m, 3H),
3.25–3.40 (m, 6H), 3.40–3.60 (m, 3H), 3.80–3.95 (s, br,
12H), 6.03 (s, 3H), 7.30–7.40 (m, 12H), 7.70–7.85 (m,
12H), 7.85–7.95 (m, 3H), 8.65–8.70 (m, 3H). The N–H
and O–H protons are not accounted for due to H–D
9
5%). Elemental analysis (calculated for C18H12O9
1
PS3Tl3): C, 19.66 (19.43); H, 1.13 (1.09)%. H NMR
DMSO-d6): d 7.00–7.15 (m, 3H), 7.30–7.40 (m, 3H),
(
.50–7.65 (m, 6H). 31P{ H} NMR(DMSO- d6): d )6.15
s), an impurity at 24.6 ppm amounts usually to <3% by
integration.
1
7
(
scrambling. 31P{ H} NMR(CD OD): d )5.69 (s), an
1
3
impurity at 28.4 ppm amounts usually to <5% by inte-
2
5
4.12. Modified synthesis of (R)-N,N,N-trimethyl-1-phen-
ethylammonuim iodide
gration. [a] ¼ 19.0 (c ¼ 1.034, C H OH).
D
2
5
4.15. TPPS-tris-(R)-N,N-dimethyl-1-(naphtyl)ethylam-
monium salt (15)
A solution of CH3I (3.35 g, 23.6 mmol) in CHCl3 (10
ml) was added to a stirred solution of (R)-N,N-dimethyl-
1
The resulting solution was stirred for 5 h, pumped down
-phenethylamine (3.16 g, 21.2 mmol) in CHCl3 (20 ml).
A solution of (R)-N,N-dimethyl-1-(naphtyl)ethyl-
amine (496.0 mg, 2.489 mmol) in CH OH (5 ml) was
3
to a colorless foam, washed and slurried in Et O (30 ml),
2
added dropwise to a stirred solution of TPPS-H (410.1
3
and dried in vacuo yielding a white powder (5.89 g,
1
mg, 0.8014 mmol) in CH OH (5 ml). The resulting
3
9
5%). H NMR (CDCl3): d 1.81 (d, 3 H, J ¼ 7 Hz), 3.34
solution was stirred for 4 h. The volatiles were re-
moved in vacuo affording a golden oil. Slurrying and
washing with Et2O (2 ꢁ 10 ml) afforded a white powder
(
s, 9H), 5.37 (q, 1 H, J ¼ 7 Hz), 7.35–7.45 (m, 3 H), 7.55–
7
.65 (m, 2 H).
(838 mg, 95%). Elemental analysis (calculated for
4.13. TPPS-tris-(R)-(+)-N,N,N-trimethyl-1-phenethyl-
ammonuim salt (13)
C60H66 N3O9PS3): C, 65.05 (65.49); H, 6.03 (6.05); N,
1
3
9
7
7
.89 (3.82)%. H NMR (CD OD): d 1.72 (d, J ¼ 7 Hz,
3
H), 2.70 (s, br, 18 H), 5.25 (q, J ¼ 7 Hz, 3 H), 7.20–
A solution of (R)-(+)-N,N,N-trimethyl-1-phenethyl-
ammonuim iodide (475.6 mg, 1.633 mmol) in CH3OH
.30 (m, 6 H), 7.50–7.65 (m, 9 H), 7.70–7.85 (m, 9 H),
3
1
1
.90–8.00 (m, 6 H), 8.20–8.30 (m, 3 H). P{ H}
(
10 ml) was dropwise added to a stirred white slurry of
NMR(CD3OD): d)5.55 (s), an impurity at 28 ppm
TPPS-Tl salt (627.3 mg, 0.5436 mmol) in CH3OH (10
ml). At equivalence point a floculating orange-yellow
precipitate formed. The mixture was stirred for 6 h in
the dark. The yellow solid was filtered off over celite and
2
5
amounts usually to <5% by integration. [a] ¼ 11.0
D
(
c ¼ 2.011, CH3OH).
extracted with CH OH (2 ꢁ 5 ml). The combined col-
4.16. TPPS-tris-(R)-N,N-dimethyl-1-phenethylammo-
nuim salt (16)
3
orless filtrate was pumped down to an off-white glassy
solid which was washed and slurried in Et2O (2 ꢁ 10 ml)
and then dried in vacuo yielding a white finely divided
powder (520 mg, 96%). Elemental analysis (calculated
A solution of (R)-N,N-dimethylphenethylamine (372
mg, 2.49 mmol) in CH3OH (5 ml) was dropwise ad-
ded to a stirred solution of TPPS-H3 (420.5 mg,
0.8168 mmol) in CH3OH (5 ml). The resulting solu-
tion was stirred for 4 h. The volatiles were removed in
vacuo affording a golden foaming oil. Slurrying and
washing with Et2O (2 ꢁ 10 ml) afforded a white
powder (729 mg, 94%). Elemental analysis (calculated
for C48H60N3 O9PS3): C, 60.74 (60.67); H, 6.40 (6.36);
for C51H66N3O9PS3): C, 61.84 (61.73); H, 6.69 (6.70); N,
1
4
.20 (4.23)%. H NMR (CD3OD): d 1.72 (‘‘dt’’, J1 ¼ 7
Hz, J ¼ 2 Hz, 9 H), 2.96 (s, br, 27 H), 4.69 (q, J ¼ 7 Hz,
2
3 H), 7.25–7.60 (m, 18 H), 7.75–7.90 (m, 9 H), the
spectrum indicates the presence of 2 mol% Et O.
2
3
1
1
P{ H} NMR(CD3OD): d )5.61 (s), an impurity at 28
25
ppm amounts usually to <5% by integration. [a] ¼ 19.0
D
1
(
c ¼ 1.034, C2H5OH).
N, 4.40 (4.42). H NMR (CD3OD): d 1.62 (d, J ¼ 7
Hz, 9 H), 2.66 (s, br, 18 H), 4.38 (q, J ¼ 7 Hz, 3 H),
3
1
1
4
.14. TPPS-tris-hydroquinidinium salt (14)
7.30–7.45 (m, 21 H), 7.80–7.90 (m, 6 H). P{ H}
NMR(CD3OD): d )5.62 (s), an impurity at 28 ppm
2
5
A solution of TPPS-H3 (328.0 mg, 0.6409 mmol) in
CH OH (3 ml) was added dropwise to a solution of
amounts usually to <5% by integration. [a] ¼ 12.7
D
(c ¼ 1.004, CH3OH).
3

758
R. Dorta et al. / Journal of Organometallic Chemistry 689 (2004) 751–758
4
ethylammonium] (17)
.17. [Rh(NBD)TPPS
2
][(R)-N,N-dimethyl-1-(naphtyl)
obtained free of charge via www.ccdc.cam.ac.uk/conts/
5
retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or deposit@ccdc.
cam.uk).
A solution of TPPS-tris-(R)-N,N-dimethyl-1-naph-
tylammonuim salt (15, 408.5 mg, 0.3712 mmol) in
CH OH (4 ml) was added dropwise to solid
3
[
affording an orange solution. Addition of Et O (16 ml)
Rh(NBD) ]BF (69.0 mg, 0.1845 mmol) under stirring
2 4
2
References
caused the precipitation of a red oil. Separation by de-
cantation and drying in vacuo afforded a yellow powder
which was washed with THF (2 ꢁ 16 ml) to remove
[1] R. Noyori, Asymmetric Catalysis in Organic Synthesis, Wiley–
Interscience, New York, 1994.
[
2] D.L. Hughes, D.-H. Dolling, K.M. Ryan, E.F. Schoenewaldt,
E.J.J. Grabowski, J. Org. Chem. 52 (1987) 4745.
3] T. Ooi, M. Kameda, K. Maruoka, J. Am. Chem. Soc. 125 (2003)
5139.
[
TPPS-(naphtylethylammonium-Me2H)3]BF4 and dried
in vacuo. Elemental analysis (calculated for C113H122
N O P RhS ): C, 62.06 (61.82); H, 5.70 (5.60); N, 3.21
[
5
18
2
6
1
(
3.19)%. H NMR (CD OD): d 1.25 (br, 2 H), 1.73 (d,
[4] B.M. Trost, D.L. Van Vranken, C. Bingel, J. Am. Chem. Soc. 114
1992) 9327.
3
(
J ¼ 7 Hz, 15 H), 2.75 (s, 30 H), 3.87 (br, 2 H), 4.47 (br, 4
31
1
[5] G. Oehme, in: B. Cornils, W.A. Herrmann (Eds.), Aqueous Phase
Organometallic Catalysis, VCH–Wiley, Weinheim, 1998.
H), 5.38 (q, J ¼ 7 Hz, 5 H), 7.30–8.30 (m, 59 H). P{ H}
NMR(CD3OD): d 29.2 (d, br, J ¼ 150 Hz).
[
[
[
[
6] D.B. Llewellyn, D. Adamson, B.A. Arndtsen, Org. Lett. 2 (2000)
165.
7] K. T o€ llner, R. Popovitz-Biro, M. Lahav, D. Milstein, Science 278
1997) 2100.
4
4.18. [Rh(NBD)TPPS
ethylammonium] (18)
2 4
][BF ][(R)-N,N-dimethyl-phen-
(
6
8] C. Bianchini, E. Farnetti, M. Graziani, J. Kaspar, F. Vizza, J. Am.
Chem. Soc. 115 (1993) 1753.
9] J. van den Broeke, M. Lutz, H. Kooijman, A.L. Spek,
B.-J. Deelman, G. van Koten, Organometallics 20 (2001)
(
RD193) A solution of TPPS-tris-(R)-N,N-dimethyl-
-phenethylammonuim salt (16, 527 mg, 0.555 mmol) in
CH3OH (7 ml) was added dropwise to a solution of
Rh(NBD)2]BF4 (106 mg, 0.284 mmol) in CH3OH (1
1
2
10] E. Monflier, P. Bourdauducq, J.-L. Couturier, J. Kervennal, A.
114.
[
[
Mortreux, J. Mol. Catal. A 97 (1995) 29.
[11] Y. Orito, S. Imai, S. Niwa, J. Chem. Soc. Jpn. (1980) 670.
ml). The reaction mixture was stirred for 2 h and then
evaporated to an orange glassy solid. Slurrying and
washing with THF (3 ꢁ 10 ml), followed by high vac-
uum drying afforded an orange, finely divided solid
[
12] H.-U. Blaser, H.P. Jalett, W. Lottenbach, M. Studer, J. Am.
Chem. Soc. 122 (2000) 12675.
[
13] T. Heinz, G. Wang, A. Pfaltz, A. Minder, M. Sch u€ rch, T.
Mallat, A. Baiker, J. Chem. Soc., Chem. Commun. (1995)
(
C103H128BF N O P RhS ): C, 56.62 (56.69); H, 5.99
550 mg, 91%). Elemental analysis (calculated for
1
421.
[14] J.M. Bonello, F.J. Williams, R.M. Lambert, J. Am. Chem. Soc.
125 (2003) 2723.
4
6
18
2
6
1
(
5.91); N, 3.79 (3.85)%. H NMR (CD3OD): d 1.48 (br,
[
[
15] H.-U. Blaser, Tetrahedron: Asymmetry 2 (1991) 843.
16] Attempts to exchange the sodium ions of the commercially
available tetrasodium salt of the diphosphine ligand 1,2-bis(di-4-
sulfonatophenylphosphino)benzene in similar ways were not
successful.
2
H), 1.65 (d, J ¼ 7 Hz, 18 H), 2.68 (s, 36 H), 4.04 (br, 2
H), 4.39 (q, J ¼ 7 Hz, 6 H), 4.57 (br, 4 H), 7.35–7.50 (m,
1
4
2 H), 7.88 (m, 6 H), 8.08 (br, 6 H). 31P{ H} NMR
(
CD3OD): d 29.2 (d, br, J ¼ 155 Hz).
[
17] M. Stradiotto, J. Cipot, R. McDonald, J. Am. Chem. Soc. 125
(
2003) 5618.
[18] B.G. van der Hoven, H. Alper, J. Am. Chem. Soc. 123 (2001)
0214.
4
.19. Typical catalytic run
1
[19] C. Dai, E.G. Robins, A.J. Scott, W. Clegg, D.S. Yufit, J.A.K.
Howard, T.B. Marder, J. Chem. Soc., Chem. Commun. (1998)
A Fischer–Parr reactor was charged in the glove box
with the catalyst precursor, the substrate, and the solvent.
The reactor was then taken out of the glove box, pres-
surized to 5 or 6 bar and depressurized three times with
hydrogen, and put under 5 or 6 bar of hydrogen pressure.
At the end of the reaction the solid was filtered off and the
filtrate directly used for HPLC determination. NMR
spectra were taken after removing the volatiles.
1
983.
[
20] C. Bianchini, D.G. Burnaby, J. Evans, P. Frediani, A. Meli, W.
Oberhauser, R. Psaro, L. Sordelli, F. Vizza, J. Am. Chem. Soc.
1
21 (1999) 5961.
[
[
[
[
21] Complexes analogous to 6 and 7 bearing the COD ligand instead
of NBD were very sluggish hydrogenation catalysts.
22] M.J. Burk, J.E. Feaster, W.A. Nugent, R.L. Harlow, J. Am.
Chem. Soc. 115 (1993) 10125.
23] A. Joy, S. Uppili, M.R. Netherton, J.R. Scheffer, V. Ramamurthy,
J. Am. Chem. Soc. 122 (2000) 728.
24] B.F.G. Johnson, S.A. Raynor, D.S. Shephard, T. Mashmeyer,
J.M. Thomas, G. Sankar, S. Bromley, R. Oldroyd, L. Gladden,
M.D. Mantle, Chem. Commun. (1999) 1167.
5
. Supplementary Material
CCDC 214524 contains the supplementary crystal-
lographic data for compound 8. These data can be
[25] A. Ohno, A. Tsutsumi, Y. Kawai, N. Yamazaki, Y. Mikata, M.
Okamura, J. Am. Chem. Soc. 116 (1994) 8133.