The η5-(σ-P,π-arene) chelating H-MOP ligand in an optically and catalytically active rhodium(I) complex

Article abstract of DOI:10.1002/ejic.200390027

(R)-methylbinapium, a Hayashi-type phosphonium-MOP ligand, reacts with [Rh(cod)₂][BF₄] in ethanol to afford the chiral mixed bis(monophosphane)rhodium(I) complex [Rh(η⁵-H-MOP)(MePh₂P)][BF₄]. The constitutional and geometrical features of this complex have been determined by exhaustive ¹H, ¹¹B, ¹³C, ³¹P and ¹⁰³Rh 1-D, 2-D and NOE NMR spectroscopy and optical rotation measurements. The chelating η⁵-(γ-phosphanyldiene) ligand character of H-MOP in this complex is an extension to Rh¹ of similar coordination modes studied by Pregosin in the coordination sphere of Ru^II. The process of its formation relies on an enantiospecific reductive cleavage of a P⁺-C bond, which is also reminiscent of Pregosin's P-C bond cleavages in the ruthenium series. The complex is a catalytic precursor for the hydrogenation of (Z)-αacetamidocinnamic acid. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200390027

SHORT COMMUNICATION
5
The η -(σ-P,π-Arene) Chelating H-MOP Ligand in an Optically and
Catalytically Active Rhodium(
I
) Complex
[a]
[a]
[a]
[a]
Mich e` le Soleilhavoup, Lydie Viau, G e´ rard Commenges, Christine Lepetit, and
Remi Chauvin*[
a]
Keywords: Phosphane ligands / Arene ligands / Atropisomerism / Rhodium / NMR spectroscopy / Asymmetric catalysis
II
(
R)-methylbinapium, a Hayashi-type phosphonium-MOP li-
studied by Pregosin in the coordination sphere of Ru . The
gand, reacts with [Rh(cod) ][BF ] in ethanol to afford the
chiral mixed bis(monophosphane)rhodium(I) complex [Rh(η - cleavage of a P −C bond, which is also reminiscent of Pregos-
2
4
process of its formation relies on an enantiospecific reductive
5
+
H-MOP)(MePh
2
P)][BF
4
]. The constitutional and geometrical
in’s P−C bond cleavages in the ruthenium series. The com-
plex is a catalytic precursor for the hydrogenation of (Z)-α-
acetamidocinnamic acid.
features of this complex have been determined by exhaustive
1
11
13
31
103
H, B, C, P and
scopy and optical rotation measurements. The chelating η -
γ-phosphanyldiene) ligand character of H-MOP in this com-
Rh 1-D, 2-D and NOE NMR spectro-
5
(
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
I
plex is an extension to Rh of similar coordination modes
4
Introduction
few cases, the H-MOP ligand displays an η -coordination
of one naphthyl substituent.
[
7,9]
According to the recent literature, the dogma stating that
only chelating chiral diphosphane ligands can lead to high
ee’s in reductive asymmetric catalysis has exceptions pro-
vided that the alternative monophosphane ligands contain
a resolved atropisomeric biaryl axis.[ Monophosphite,
monophosphonites and phosphoramidites of binaphthol
1]
are thus efficient ligands for the rhodium-catalyzed asym-
metric hydrogenation of acrylic acid derivatives,[
1,2]
while
Hayashi’s X-MOP ligands (Scheme 1) are efficient ligands
[
3]
Scheme 1. X-MOP ligands
for the palladium-catalyzed reduction of allylic alcohols,
[4]
palladium-catalyzed hydrosilylation of olefins, or rhod-
ium-catalyzed arylation of imines.[ The intriguing stereo-
chemical efficiency of the X-MOP ligands is similar to that
5]
[
6]
Our initial goal was to look for chiral phosphoniophos-
of the homoleptic binap ligand 1 (formally PPh -MOP).
2
phane ligands capable of providing hybrid chelation by
This is assumed to mainly result from steric/electronic ef-
fects, but it might also be enhanced by the transient coor-
dination of one or more CϭC bonds of the naphthyl
groups. Indeed, Pregosin’s work definitely shows that binap
and biphep can act as two-, four-, six-, or eight-electron
δϪ
primary PǞ[Rh]
dative and secondary electrostatic
P ···[Rh] interactions.[11] The results with ‘‘methyldi-
opium’’ as a ligand prototype suggested that the electro-
static interaction might be too loose due to the flexibility
ϩ
δϪ
[
12]
donors in ruthenium() complexes.[
7,8]
of the diopium skeleton.
The 1,1-binaphthyl core of 2,
On the other hand,
ϩ
a P -MOP ligand previously termed as ‘‘methylbinapium’’
binap- and MeO-biphep-ruthenium complexes have been
reported to undergo selective hydrolytic PϪC bond cleavage
leading to complexes containing both a monophosphane H-
[
13]
(Scheme 1),
was therefore devised as a more rigid skel-
eton. The coordination chemistry of binapium 2 is, how-
[
12,13]
MOP ligand and a diphenylphosphinoyl ligand.[
9,10]
ever, quite versatile.
While the methylbinapium skel-
In a
eton is known to enter the coordination sphere of rhodi-
um() as its ylide form (Scheme 1, X ϭ PPh ϭCH ), the
[14]
2
2
[
a]
Laboratoire de Chimie de Coordination du CNRS, UPR 8241,
outcome of our attempts to introduce methylbinapium 2
2
05 Route de Narbonne, 31077 Toulouse cedex 4, France
ϩ
(
X ϭ PPh CH ) directly into the coordination sphere of
Fax: (internat.) ϩ33-5/6155-3003
E-mail: chauvin@lcc-toulouse.fr
2 3
rhodium() is here disclosed.
Eur. J. Inorg. Chem. 2003, 207Ϫ212  2003 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 1434Ϫ1948/03/0102Ϫ0207 $ 20.00ϩ.50/0
207

M. Soleilhavoup, L. Viau, G. Commenges, C. Lepetit, R. Chauvin
SHORT COMMUNICATION
Results and Discussion
lent aromatic protons, and three equivalent shielded pro-
2
tons of a methylphosphane unit at δ ϭ 1.50 ppm (d, J
9 Hz). This observation supports a [Rh(PAr
complexation pattern.
ϭ
ϩ
PH
Reactivity of Methylbinapium 2 with [Rh(cod) ][BF ]
)(PAr Me)]
3 2
2
4
‘‘(R)-methylbinapium’’ 2 was prepared by a one-step
A weaker coupling of the 31P nuclei also occurs with an
intriguing H nucleus at δ ϭ 5.44 ppm. According to the
H- H COSY spectrum, this proton shows a JH,H coupling
of 6.2 Hz with a proton whose signal appears at δ ϭ
.57 ppm, itself similarly coupled with a third proton (δ ϭ
symmetry breaking of the parent C -symmetric diphos-
2
1
[
13]
phane 1 with MeI.
The steric hindrance exerted by the
1
1
3
III
phosphonium terminus towards the P terminus was illus-
trated by both the X-ray-crystal structure of binapium iod-
ide 2·I, and by its lack of reactivity toward electrophiles
7
[13]
7.07 ppm). These latter three protons, referred to as H4,
H3, and H2 (see Scheme 3), are also weakly coupled with
[
e.g. MeI or Fe(CO) (NMe )]. It is therefore not surpris-
4 3
ing that 2·I did not react with either [RhCl(cod)]2 or
Rh(cod) ][BF ] under conventional conditions. Under
3
1
P nuclei (J Յ 1 Hz). They were assigned to the protons
[
PH
2
4
4
of the η -diene-Rh moiety of a chelating H-MOP ligand.
The η -coordination was confirmed by the high field reson-
harsher conditions, however, namely in boiling ethanol for
two days, [Rh(cod) ][BF ] did react with a single equivalent
4
2
4
ance (δ ϭ 97.3Ϫ105.5 ppm) of the corresponding carbon
of binapium iodide 2·I. The expected product [RhI(cod)-
2)][BF ] was not observed, but column chromatography
1
atoms C2, C3, C4 and C1, as well as by their J
values
(
RhC
4
(c.a. 5 Hz). By contrast, the resonance at lower field of the
allowed the separation of two complexes. An apolar com-
plex was eluted first and assigned to structure 4 on the basis
adjacent C5 and C10 carbons (δ ϭ 119.7 and 122.4 ppm)
103
1
13
31
and the absence of coupling to the Rh nucleus rule out
of its H, C and P NMR spectroscopic data. The major
6
1
31
the possibility of an η -coordination mode previously enco-
polar complex was then eluted. Its H and P NMR spec-
tra indicate the absence of both a cyclooctadiene ligand and
any phosphonium group, and display two coupled non-
equivalent P atoms at a rhodium center. The structure of
this complex was later assigned as the H-MOP complex
[
16]
untered in other cationic phosphane-rhodium complexes.
1
In the ruthenium series, due to the absence of J
in-
RuC
4
formation, it is more difficult to draw the line between η -
and η -coordination. Nevertheless, in the related complex
Ru(η -H-MOP)(PPhEt )(PPh OH)] [OTf]2, which was
assigned an η -diolefin structure, the effect of the proximate
6
5
2ϩ
[
3
·BF (Scheme 2, see below). Surprisingly, in the presence
2 2
4
4
of two equivalents of 2·I, the conversion of [Rh(cod) ][BF ]
2
4
was much slower. This was ascribed to a harmful effect of Ru atom on the uncoordinated C5 and C10 atoms was re-
III
the excess iodide ions competing with the hindered P
ported to result in chemical shifts of δ ϭ 116.2 and
center of 2. Indeed, reaction of [Rh(cod) ][BF ] with the 116.4 ppm, respectively. These are of the same order of
2
4
tetrafluoroborate salt 2·BF proceeded more rapidly and magnitude as those of C5 and C10 in the rhodium complex
4
[
7]
4
more selectively: after refluxing for 20 h in ethanol, complex 3. It is also worth noting that the η -coordination mode
3
1
3
·BF was the sole rhodium complex observed by P NMR in 3 is consistent with a classical 16-electron count in the
4
analysis of the crude material.
coordination sphere of phosphanylrhodium() complexes.
Although we were unable to isolate a crystal suitable for
an X-ray diffraction analysis, the structure of the complex
is probably very static, as indicated by VTP NMR analysis
at 313 and 223 K: apart from a slight broadening, no signi-
Structure Determination of Complex 3.
The major signal in the ES-MS spectrum at m/z ϭ 741.2
is consistent with the parent cationic fragment
1
31
ϩ
ficant shift nor decoalescence of the H and P signals was
[
(MePh P)(H-MOP)Rh] . The complete multinuclear
2
1
1
observed. H- H NOE experiments allowed us to confirm
the above topological assignment and to gain insights into
NMR assignment and the corresponding structure were de-
termined in CDCl solution. The ionic nature of the com-
3
ϩ
Ϫ
plex could be first refined as a [RhPPЈ] [BF ] form from the geometrical relationships between protons (Scheme 3).
4
1
1
103
the B and
Ϫ391 ppm (dd, J
Rh NMR signals at δ ϭ Ϫ0.59 ppm and In particular, they show that in the preferred conformation,
1
1
ϭ 199.6, J
ϭ 206.0 Hz), respect- the methyl group is oriented towards the PPh
2
terminus of
ively. The shielded Rh signal is typical for a rhodium() the naphthylphosphane ligand, while both phenyl rings of
PRh
03
PЈRh
1
complex in this environment.[ The HMQC H- P spec- the methyldiphenylphosphane ligand are oriented towards
15]
1
31
3
1
103
trum (Figure 1) displays a strong coupling of the P/ Rh the diene moiety. Although direct information on the con-
4
ABX pattern [δ ϭ 18.31 ppm (dd) and 57.39 ppm (dd), formation of the η -naphthyl group is not available, the ab-
1
1
2
JPRh ϭ 200, J
ϭ 206, J ϭ 39 Hz] with five inequiva- sence of an NOE between the latter phenyl ring protons
PRh
PP
Scheme 2. Reaction of methylbinapium 2 with [Rh(cod)
08
2 4
][BF ]
2
Eur. J. Inorg. Chem. 2003, 207Ϫ212

An Optically and Catalytically Active Rhodium(I) Complex
SHORT COMMUNICATION
1
31
Figure 1. 400Ϫ162 MHz HMQC H- P NMR spectrum of 3·BF
4
in CDCl
3
solution at 298 K; a weaker correlation of H4 with P1 and
P2 is also seen at a lower threshold of the 2D plot (atom numbering in Scheme 3); *: residual acetone peak
2
5
and that of free (S)-H-MOP prepared by Hayashi is [α]
ϭ
D
[
18]
ϩ102 (c ϭ 2.03, CHCl3). The chiral information brought
by the (R)-binapium reactant is therefore qualitatively pre-
served: the complex is enantiospecifically obtained as an
enriched scalemic mixture.
5
In summary, the complex thus contains both an η -(σ-
1
P, π-arene) (S)-H-MOP ligand and an independent η ,σ-P
methyldiphenylphosphane ligand. It provides a generaliza-
tion to rhodium() of similar well-documented com-
[
7Ϫ9]
plexation patterns in ruthenium() complexes.
It is,
however, worth noting that other chelating ω-phosphanylal-
kene ligands associated with an independent monophos-
phorus() ligand at a rhodium() center are known.[
19]
؉
Reaction Mechanism via Reductive P ؊C Bond Cleavage
The formation of complex 3 formally results from a com-
plexation-reduction process. The reducing agent here is the
ethanol solvent, which is also commonly used to convert
1
1
Scheme 3. 3D structural assignment based on H- H NOE experi-
ments
[
24]
rhodium() salts to rhodium() complexes.
mechanism involving elementary processes at Rh and Rh
A plausible
I
III
and the H6ϪH9 protons would be consistent with a folding centers is depicted in Scheme 4. Starting from (R)-binap-
along the C1···C4 axis. Such a folding (ca. 35°) was indeed ium, the final stereoselective reductive elimination would fi-
4
[18]
ϩ
reported to occur in the related complex [(η -naph- nally lead to an (S)-H-MOP ligand.
thalene)RhCp].
The overall P ϪC
Finally, NOE data also support a clas- bond cleavage process is reducing in nature, and is therefore
sical face-to-edge conformation of the phenyl substituents basically complementary to the related ‘‘acid-induced’’ and
[
17]
in both the RhPPh units.
‘‘solvent-induced’’ PϪC bond cleavage processes identified
2
The optical rotation of complex 3·BF is high: [α]2
5
ϭ
D
by Pregosin in the coordination sphere of ruthenium com-
4
[
7]
ϩ175 (c ϭ 0.1, CH Cl ). For comparison, the optical rota- plexes. A related reductive PϪC bond cleavage was also
2
2
tion of the enantiomerically pure complex [{(R)- invoked in the coordination sphere of a rhodium complex
2
0
[6]
binap}(cod)Rh][ClO ] is [α] ϭ ϩ180 (c ϭ 0.05, CH Cl ),
converting PPh to PPh (n-Pr) under hydrogen in the pres-
4
D
2
2
3 2
Eur. J. Inorg. Chem. 2003, 207Ϫ212
209

M. Soleilhavoup, L. Viau, G. Commenges, C. Lepetit, R. Chauvin
SHORT COMMUNICATION
Scheme 4. Plausible mechanism for the formation of complex 3
ence of propylene at 130 °C.[20] It is also worth noting that
V
Hayashi recently reported a selective P ϪC bond cleavage
[21]
by nBuLi in neutral P(O)Ph -MOP derivatives.
2
Catalytic Hydrogenation with Complex 3
The chiral structure of complex 3 combines the essential Scheme 5. Catalytic hydrogenation of (Z)-α-acetamidocinnamic
ϩ
acid with complex 3 as precursor
features of classical [P Rh(diene)] catalytic precursors for
2
asymmetric hydrogenation of prochiral acrylic acid derivat-
ives,[
[
22]
albeit in another connectivity pattern,
ϩ
P(Pdiene)Rh] . These features prompted us to test com-
plex 3 in a 1% catalytic ratio for the hydrogenation of (Z)-
α-acetamidocinnamic acid, a reference substrate. Under 1
bar of hydrogen in methanol, the conversion into N-acetyl-
phenylalanine reached only 6% after 40 h. Under 20 bar of
hydrogen, however, the conversion reached 95%, although
no significant enantioselectivity was obtained. According to
the generally accepted mechanism for rhodium-catalyzed
hydrogenation, the η -diene moiety should be hydrogen-
ated in situ to a putative (but likely) tetralinyl-substituted
naphthylphosphane complex 5. In this complex, the (S)
configuration of the chiral carbon center should result from
the initial (S)-configuration of the chirality axis of H-MOP
Conclusion
The novelty of the above results comes from two points:
5
(
i) the η -(σ-P,π-arene) hetero-chelating behaviour of an
atropisomeric biarylphosphane at a rhodium() center; (ii) a
selective reductive P ϪC bond cleavage leading to a mixed
bis(monophosphane)rhodium() complex. This peculiar or-
ganometallic chemistry and the preliminary catalytic results
pave the way to more general studies of this type of com-
plexes in other Rh-catalyzed processes, such as CϪC bond
ϩ
[
22]
4
[3,4,5]
forming reactions.
(Scheme 5). The fate of the 1,1Ј-tetralinylnaphthtylphos-
phane ligand has been investigated by MM2 calculations.
The latter suggest that, in contrast to H-MOP, this ligand
Experimental Section
[23]
no longer contains a frozen atropisomeric axis.
‘
Both Reactions were carried out under a nitrogen atmosphere using
‘atropisomers’’ are essentially isoenergetic,[23b] and the ro- Schlenk tube and vacuum line techniques. Ethanol was distilled
tation barrier could be estimated at approx. 45 over drierite. Dichloromethane was distilled over P
Binap and methyl iodide were purchased from Fluka. Ammonium
tetrafluoroborate was purchased from Aldrich. [Rh(cod) ][BF ] was
prepared from [RhCl(cod)] , itself prepared from cyclooctadiene
and RhCl ·3H O (JohnsonϪMattey) according a modified de-
scribed procedure (no carbonate was added). NMR spectra were
recorded in CDCl solution, on Bruker AC 200 and AMX 400
spectrometers. Positive chemical shifts at low field are expressed in
2 5
O . (Ϫ)-(R)-
Ϫ1 [23c]
kcal·mol
.
In qualitative accordance with the experi-
2
4
mental observations, the same method applied to the parent
2
H-MOP ligand affords a much higher barrier of about 130
Ϫ1 [3,4]
3
2
kcal·mol
.
The 1,1Ј-tetralinylnaphthtylphosphane li-
[
24]
gand can therefore be qualified as ‘‘weakly’’ chiral. The
negligible ee is therefore consistent with all reports on the
3
1
13
enantioselectivity control by monophosphane ligands bear- ppm relative to internal TMS for H and C, and external 85%
ing a remote chiral center on their backbone.[
22]
3 4 2
H PO in D
O for P. 103Rh chemical shifts are given to high fre-
31
210
Eur. J. Inorg. Chem. 2003, 207Ϫ212

An Optically and Catalytically Active Rhodium(I) Complex
quency of Ξ(103Rh) ϭ 3.16 MHz. Optical rotations were measured 4JP1C14 ϭ 2.5 Hz, C14), 130.79 (d, 4JP1C14Ј ϭ 2.5 Hz, C14Ј), 131.11
SHORT COMMUNICATION
4
2
in a 1-dm cell with a PerkinϪElmer 241 polarimeter.
(d, JP2C24Ј ϭ 2.0 Hz, C24Ј), 131.20 (d, JP1C12 ϭ 12.0 Hz, C12),
1
J
31.30 (d, 1
J
P2C21Ј ϭ 48 Hz, C21Ј), 131.30 (s, C4Ј), 131.47 (d,
P2C22Ј ϭ 11.5 Hz, C22Ј),
P2C24 ϭ 3 Hz, C22), 132.40 (d, 2JP1C12Ј ϭ 12.0 Hz,;
J
Methylbinapium 2: (R)-Methylbinapium iodide 2·I (m.p. 307Ϫ310
3
2
P2C10Ј ϭ 15 Hz, C10Ј), 132.00 (d,
J
°
C) was prepared in 97% yield from (R)-binap 1 according to de-
32.35 (d, 4
1
[
13,14]
scribed procedures.
tained quantitatively by metathesis of 2·I and [NH
The tetrafluoroborate salt 2·BF
][BF
4
was ob-
1
4
C12Ј), 132.50 (d, JP1C11Ј ϭ 47.5 Hz, C11Ј), 134.44 (d, JP2C5Ј
.0 Hz, C5Ј), 134.72 (d,
P1C11 ϭ 46.2 Hz, C11), 142.27 (d, JP2C1Ј ϭ 21.0 Hz, C1Ј), 146.21
dd, JP2C2Ј ϭ 49.0, JP1C2Ј ϭ 3.0 Hz, C2Ј) ppm.
ϭ
4
4
].
2
2
J
(
JP2C22 ϭ 13.5 Hz, C22), 137.62 (d,
1
2
Complex 3·BF4: (R)-Binapium tetrafluoroborate 2·BF
.16 mmol) and [Rh(cod) ][BF ] (0.065 g, 0.16 mmol) were mixed
4
(0.115 g,
1
2
0
2
4
in ethanol (15 mL). The suspension was heated, and the resulting
deep orange solution was refluxed for 20 h. The solvent was then
Hydrogenation Procedure: Complex 3·BF (0.005 g, 0.006 mmol)
4
and (Z)-α-acetamidocinnamic acid (0.123 g, 0.6 mmol) were placed
in a glass vessel in a steel autoclave under 1 bar of nitrogen atmo-
sphere. Methanol was then syringed in, and the autoclave was pres-
surized to 21 bar with hydrogen gas. After stirring at 25 °C for 40 h,
the autoclave was opened and the solvent evaporated to dryness to
31
evaporated under reduced pressure. P NMR analysis of the crude
material indicated the presence of complex 3·BF along with traces
): δ ϭ 26.52 (s, 1 P,
PϭO)]. Further purification was
achieved by chromatography over silica gel eluting with CH Cl
4
3
1
of binapium oxide [ P NMR (81 MHz, CDCl
3
ϩ
2 2
MePh P ), 31.67 (s, 1 P, Ph
2
2
/
1
give an orange solid. H NMR analysis of the crude material in
acetone mixtures of increasing polarity (from 100:0 to 80:20). The
most colored fractions were collected and the solvents evaporated,
leading to an orange solid (0.060 g, 45%) which was used for full
spectroscopic analysis and optical rotation measurement. TLC
6
[D ]DMSO indicated an exclusive 95% conversion of the staring
material to N-acetylphenylalanine. The catalyst residue was re-
moved by treatment with a 5  aqueous NaOH solution and wash-
ing with Et
extracted with Et
2
O. After acidification with HCl, the aqueous layer was
O. The organic layer was dried over MgSO and
(
SiO
2 2 2 f
, CH Cl /acetone 80:20) R ϭ 0.60. (ϩ)ES-MS: m/z ϭ 741.2
25
25
2
4
with consistent isotopic pattern. [α]
D
ϭ ϩ175, [α]578 ϭ ϩ202.
). B (128.4 MHz, CDCl ): δ ϭ
4
). Other NMR assignments were
the solvents evaporated giving a white powder (0.87 g) consisting
25
11
[α]546 ϭ ϩ278 (c ϭ 0.1, CH
2
Cl
2
3
in 95% N-acetylphenylalanine and 5% unchanged olefin according
1
Ϫ0.59 (q,
J
FB ϭ 1.0 Hz, BF
1
25
to H NMR spectroscopy. [α]
D
ϭ ϩ0.007 (c ϭ 1, EtOH).
1
31
31
1
13
1
13
1
achieved with the help of H{ P}, P{ H}, C{ H}, C{ H,
3
1
1
31
1
31 103
1
1
13
31
P}, H- P{ H} HMQC, P- Rh J-HMQC, H- C{ P},
1
1
31
1
1
1
31
H- H{ P} GS-HMQC, H- H GS-COSY45, H{ P} dpfgse
[
[
1]
1
1
31
M. T. Reetz, G. Mehler, Angew. Chem. 2000, 112, 4047Ϫ4049;
M. T. Reetz, G. Mehler, Angew. Chem. Int. Ed. 2000, 39,
3889Ϫ3890.
m
TOCSY, and H- H{ P} dpfgse (t ϭ 600 ms) NOE experiments.
31P NMR (162 MHz, CDCl
): δ ϭ 57.89 (dd, 1JPRh ϭ 206.0, 2JPP
3
ϭ
2] [2a]
P), 19.28 (dd, 1JPRh ϭ 199.6, 2JPP ϭ 38.6 Hz,
C. Claver, E. Fernandez, A. Gillon, K. Heslop, D. J. Hyett,
A. Martorell, A. G. Orpen, P. G. Pringle, Chem. Commun.
3
8.6 Hz, NaphtPh
2
P) ppm. 1 Rh NMR (12.6 MHz, CDCl
03
MePh
2
3
): δ ϭ Ϫ391 (dd,
000, 961Ϫ962. [ M. van den Berg, A. J. Minnaard, E. P.
2b]
2
1
PRh ϭ 206.0, 1JPRh ϭ 199.6 Hz, PPЈRh ) ppm. H NMR
ϩ
1
J
Schudde, J. van Esch, A. H. M. de Vries, J. G. de Vries, B. L.
3
(400 MHz, CDCl
3
): δ ϭ 1.63 (ddd, 2
J
P1H ϭ 9.3 Hz,
J
RhH
ϭ
[2c]
Feringa, J. Am. Chem. Soc. 2000, 122, 11539Ϫ11450.
A.
4
3
1
3
.3 Hz, JP2H ϭ 0.6 Hz, 3 H, P1CH ), 5.44 (dt, JH4H3 ϭ 6.2 Hz,
Bayer, P. Murszat, U. Thewalt, B. Rieger, Eur. J. Inorg. Chem.
3
2JP2H4 ഠ 1 Hz, 1 H, H4), 6.56 (dd, 3
[2d]
J
J
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M. van den Berg, R. M. Haak, A. J.
3
3
P1H12Ј ϭ 11.8 Hz, 2 H, H12Ј), 6.77 (dd,
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3JP2H22Ј ϭ 12.0 Hz, 2 H, H22Ј), 7.00 (dt, JH23ЈH22Ј ഠ JH23ЈH24Ј
3
3
ϭ
ഠ
ϭ
[
[
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3
T. Hayashi, Acc. Chem. Res. 2000, 33, 354Ϫ362.
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J
H13ЈH12Ј
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6
Hayashi, Tetrahedron Lett. 1996, 4169Ϫ4172.
3
3
H9), 7.11 (dm, JP1H12 ϭ 11.8 Hz, 2 H, H12), 7.18 (ttd, JH24ЈH23Ј
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[6]
[7]
T. Hayashi, M. Ishigedani, J. Am. Chem. Soc. 2000, 122,
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.8, 4 H24ЈH22Ј ϭ 1.3, 3
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9
76Ϫ977.
3
H14ЈH13Ј ϭ 7.5, 4JH14ЈH12Ј ϭ 1.3, 5JP1H14Ј ϭ 1.8 Hz, 1 H, H14Ј),
.25 (dm, 5JP2H24 ϭ 2.0 Hz, 1 H, H24), 7.27 (dm, JP2H23 ϭ 2.0 Hz,
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4
7
2
3
3
H, H23), 7.27 (dd, JH3ЈH4Ј ϭ 8.4, JP2H3Ј ϭ 8.5 Hz, 1 H, H3Ј),
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3
7
.33 (d, JH6H7 ϭ 7.2 Hz, 1 H, H6), 7.33 (m, 1 H, H14), 7.35 (dm,
[
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4
3
3
N. Feiken, P. S. Pregosin, G. Trabesinger, Organometallics
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P1H13 ϭ 2.0 Hz, 2 H, H13), 7.51 (t, JH8H7 ϭ JH8H9 ϭ 7.2 Hz, 1
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3
3
H, H8), 7.55 (m, 1 H, H8Ј), 7.57 (t, JH3H2 ഠ JH3H4 ϭ 6.2 Hz, 1
8c]
H, H3), 7.57 (m, 1 H, H7), 7.66 (dt, 3JH7ЈH6Ј ഠ 3
JH7ЈH8Ј ϭ 8.3,
4
H7ЈH9Ј ϭ 1.2 Hz, 1 H, H7Ј), 7.82 (dm, 3JP2H22 ϭ 7.8 Hz, 2 H,
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3
3
H22), 7.82 (d, JH9ЈH8Ј ϭ 8.6 Hz, 1 H, H9Ј), 7.91 (dd, JH4ЈH3Ј
8
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3
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13
1
3
H6Ј) ppm. C{ H} NMR (100 MHz, CDCl ): δ ϭ 17.29 (ddd,
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1
2
3
1
[9]
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PC ϭ 32, JRhC ϭ 2, JP2C ϭ 2 Hz, P1CH
3
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ϭ
1
5
, 3 P1C4 ϭ 4.8, 3
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JP2C4 ϭ 8.0 Hz, C4), 97.56 (ddd, JRhC2 ϭ 5,
[
10]
2
P1C2 ϭ 4.0, JP2C2 Ͻ 1 Hz, C2), 101.74 (ddd, JRhC3 ϭ 4, 2JP1C3
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1
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2
1
[
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J. J. Brunet, R. Chauvin, G. Commenges, B. Donnadieu,
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125.46 (s, C6), 126.44 (s, C9Ј), 127.71 (s, C3Ј), 128.78 (d, JP1C13Ј
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3
10.5 Hz, C13Ј), 128.78 (s, C6Ј), 128.97 (d,
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[12]
[13]
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3
C23Ј), 128.94 (s, C8Ј),129.19 (d, JP1C13 ϭ 10.5 Hz, C13), 129.43
1
3
(
(
s, C7Ј), 129.66 (s, C7), 129.69 (d, JP2C23 ϭ 11.5 Hz, C23), 129.84
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2
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211

M. Soleilhavoup, L. Viau, G. Commenges, C. Lepetit, R. Chauvin
SHORT COMMUNICATION
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merely 0.7 kcal·mol
C
lower than the steric energy of the
The whole steric energy hypersurface
(S
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23c]
[
15]
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increments) afforded maximum energy structures in the range
Ϫ1
organic Chemistry vol. 13, p. 177.
10Ϫ20 kcal·mol .
[
[
[
[
[
[
[
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E. T. Singewald, X. Shi, C. A. Mirkin, S. J. Schofer, C. L. Stern,
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[24]
Addition of carbonate is not necessary and affords impure
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[
23] [23a]
MM calculations were carried out using the MM2 force
field implemented in the software, CAChe Scientific, release
3
.8, Oxford Molecular, 1995. [
23b]
The absolute minimum steric
Received September 19, 2002
Ϫ1
energy of the (S
C
,RArϪCH) rotamer is Ϫ32.8 kcal·mol . It lies
[I02534]
212
Eur. J. Inorg. Chem. 2003, 207Ϫ212