Chiral phosphino(sulfinylmethyl)triarylphosphonium ylide ligands: Rhodium complexes and catalytic properties

Article abstract of DOI:10.1021/om030343g

A novel phosphine-phosphonium ylide ligand bearing a chiral sulfinyl moiety was prepared by reaction of (o-diphenylphosphinophenyl)diphenylphosphonium methylide with (S)-menthyl p-tolylsulfinate. Reaction of this ylide with [Rh(cod)₂][PF₆] gave stable cationic disymmetrically P,C-chelated rhodium complexes with an asymmetric ylidic carbon atom anchored to the metal center. The configuration of this carbon is controlled by the S-configuration of the adjacent sulfinyl group. The stereoselectivity of the complexation is reversed from 9:1 at 20 °C to 1:9 at -45°C. An X-ray diffraction analysis of the thermodynamic complex shows that the stereoselectivity is not directed by chelation of the SO group which lies at a nonbonding distance from the rhodium center. In the presence of triethylamine, epimerization occurs via a putative neutral P,C-chelated complex bearing an yldiide ligand. In the presence of HPF₆ and PPh₃, cleavage of the ylidic carbon-rhodium bond takes place simultaneously with displacement of the phosphino-phosphonium ligand by PPh₃. The phosphine end of the ligand is intended to preserve at least one phosphine-rhodium bond, which is a common feature of all the rhodium catalysts derived from the Wilkinson complex. Indeed, we found that the phosphino-phosphonium ylide complexes are active-though poorly enantioselective-as catalysts for hydrogenation of (Z)-α-acetamidocinnamic acid and hydrosilylation of acetophenone.

Full text of DOI:10.1021/om030343g

4810
Organometallics 2003, 22, 4810-4817
Ch ir a l P h osp h in o(su lfin ylm eth yl)tr ia r ylp h osp h on iu m
Ylid e Liga n d s: Rh od iu m Com p lexes a n d Ca ta lytic
P r op er ties
Remigiusz Zurawinski,† Bruno Donnadieu,‡ Marian Mikolajczyk,*,† and
Remi Chauvin*,‡
Center of Molecular and Macromolecular Studies, Department of Heteroorganic Chemistry,
Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland, and Laboratoire de
Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077 Toulouse Cedex 4, France
Received May 9, 2003
A novel phosphine-phosphonium ylide ligand bearing a chiral sulfinyl moiety was prepared
by reaction of (o-diphenylphosphinophenyl)diphenylphosphonium methylide with (S)-menthyl
p-tolylsulfinate. Reaction of this ylide with [Rh(cod)2][PF6] gave stable cationic disymmetri-
cally P,C-chelated rhodium complexes with an asymmetric ylidic carbon atom anchored to
the metal center. The configuration of this carbon is controlled by the S-configuration of the
adjacent sulfinyl group. The stereoselectivity of the complexation is reversed from 9:1 at 20
°C to 1:9 at -45 °C. An X-ray diffraction analysis of the thermodynamic complex shows
that the stereoselectivity is not directed by chelation of the SO group which lies at a
nonbonding distance from the rhodium center. In the presence of triethylamine, epimerization
occurs via a putative neutral P,C-chelated complex bearing an yldiide ligand. In the presence
of HPF6 and PPh3, cleavage of the ylidic carbon-rhodium bond takes place simultaneously
with displacement of the phosphino-phosphonium ligand by PPh3. The phosphine end of
the ligand is intended to preserve at least one phosphine-rhodium bond, which is a common
feature of all the rhodium catalysts derived from the Wilkinson complex. Indeed, we found
that the phosphino-phosphonium ylide complexes are activesthough poorly enantioselectives
as catalysts for hydrogenation of (Z)-R-acetamidocinnamic acid and hydrosilylation of
acetophenone.
In tr od u ction
using chiral phosphonium ylide ligands in rhodium and
palladium complexes (Scheme 1).7,8 These hybrid P,C
Both the persistency of phosphorus-metal bonds and
the relative weakness of carbon-transition metal bonds
largely contribute to the possibility of catalytic pro-
cesses. Nevertheless catalytic processes with persistent
carbene-metal bonds have recently attracted much
interest,1 including from an enantioselective point of
view.1b,c Along the same line, beyond the imida-
zolylidene ligands, one may envisage other ligands
providing persistent carbon-metal bonds. In particular,
while much efforts have been recently devoted to
catalytic applications of chiral iminophosphorane2a-d
and phosphine oxide ligands,2e-l and whereas the
coordination chemistry of phosphonium ylide C-ligands
is widely documented,3 catalytic applications thereof are
scarce.4 Let us mention Grey’s report on olefin hydro-
genation catalyzed by a phosphonium diylide-rhodium
complex5 and Starzewski’s report on olefin polymeriza-
tion catalyzed by phosphonium ylide-(phosphinoeno-
late)nickel complexes.6 To the best of our knowledge,
there are only a few examples of asymmetric catalysis
(2) (a) Reetz, M. T.; Bohres, E.; Goddard, R. Chem. Commun. 1998,
935. (b) Brunel, J . M.; Legrand, O.; Reymond, S.; Buono, G. J . Am.
Chem. Soc. 1999, 121, 5807. (c) Sauthier, M.; Fornie´s-Camer, J .;
Toupet, L.; Reau, R. Organometallics 2000, 19, 553. (d) Sauthier, M.;
Leca, F.; de Souza, R.; Bernado-Gusmao, K.; Queiroz, L. F. T.; Toupet,
L.; Reau, R. New J . Chem. 2002, 26, 630. (e) Uson, R.; Oro, L. A.;
Ciriano, M. A.; Lahoz, F. J . J . Organomet. Chem. 1982, 240, 429. (f)
Abu-Gnim, C.; Amer, I. J . Organomet. Chem. 1996, 516, 235. (g)
Gladiali, S.; Pulacchini, S.; Fabbri, D.; Manassero, M.; Sansoni, M.
Tetrahedron Asymmetry 1998, 9, 391. (h) Gladiali, S.; Alberico, E.;
Pulacchini, S.; Kollar, L. J . Mol. Catal. A: Chem. 1999, 143, 155. (i)
Maj, A. M.; Pietrusiewicz, K. M.; Suisse, I.; Agbossou, F.; Mortreux,
A. Tetrahedron Asymmetry 1999, 10, 831. (j) Grushin, V. V. J . Am.
Chem. Soc. 1999, 121, 5831. (k) Andrieu, J .; Camus, J .-M.; Poli, R.;
Richard, P. New J . Chem. 2001, 25, 1015. (l) Grushin, V. V. Organo-
metallics 2001, 20, 3950.
(3) (a) Schmidbaur, H. Angew. Chem., Int. Ed. Engl. 1983, 22, 907.
(b) Kaska, W. C. Coord. Chem. Rev. 1983, 48, 1. (c) Belluco, U.;
Michelin, R. A.; Mozzon, M.; Bertani, R.; Facchin, G.; Zanotto, L.;
Pandolfo L. J . Organomet. Chem. 1998, 557, 37. (d) Bricklebank, N.
Organophosphorus Chemistry; The Royal Society of Chemistry: 1999;
Vol. 29, Chapter 6, p 231.
(4) It is well established from Keim’s work that stabilized phospho-
nium ylides are merely precursors of the actual phosphinoenolate
ligands of the catalytically active nickel species for olefin oligomeriza-
tion (SHOP process): Keim, W.; Kowaldt, F. H.; Goddard, R.; Kru¨ger,
C. Angew. Chem., Int. Ed. Engl. 1978, 17, 466.
† Polish Academy of Sciences.
(5) Grey, R. A.; Anderson, L. R. Inorg. Chem. 1977, 16, 3187.
(6) Alexander, K.; Stazewsky, O.; Witte, J . Angew. Chem., Int. Ed.
Engl. 1985, 24, 599.
(7) (a) Ohta, T.; Fujii, T.; Kurahashi, N.; Sasayama, H.; Furukawa,
I. Sci. Eng. Rev. Doshisha Univ. 1998, 39, 133. Chem. Abstr. 130:
139441r. (b) Ohta, T.; Sasayama, H.; Nakajima, O.; Kurahashi, N.;
Fujii, T.; Furukawa, I. Tetrahedron Asymmetry 2003, 14, 537. Zuraw-
inski, R.; Donnadieu, B.; Mikolajczyk, M.; Chauvin, R. J . Organomet.
Chem., accepted for publication.
‡ Laboratoire de Chimie de Coordination du CNRS.
(1) See for example: (a) Herrmann, W. A. Angew. Chem., Int. Ed.
2002, 41, 1291, and references therein. (b) Guillen, F.; Winn, C. L.;
Alexakis, A. Tetrahedron Asymmetry 2001, 12, 2083. (c) Pitkowicz, J .;
Roland, S.; Mangeney, P. Tetrahedron Asymmetry 2001, 12, 2087. (d)
Enders, D.; Gielen, H.; Breuer, K. Tetrahedron Asymmetry 1997, 8,
3571. (e) Colleman, A. W.; Hitchcock, P. B.; Lappert, M. F.; Maskell,
R. K.; Mueller, J . H. J . Organomet. Chem. 1983, 250, C9.
10.1021/om030343g CCC: $25.00 © 2003 American Chemical Society
Publication on Web 10/16/2003

Rhodium Complexes with Ylide Ligands
Organometallics, Vol. 22, No. 23, 2003 4811
bridge, encompasses binap,11a X-MOP,11b biphemp,11c
and related ligands.2e,11d The chirality element here
belongs to the metallacycle and is able to directly control
its geometrical features, e.g., the λ/δ configuration in
the case of a C2 symmetric ligand. Reetz’s diiminophos-
phorane (E′ ) ER ) NdPPh3) refers to this pattern.2a
The binapium methylide rhodium complexes shown in
Scheme 1 provide C1-symmetric examples of pattern A
(E′ ) PAr2, ER ) Ph2P+-CHZ). The pattern B, where
the appending chirality element remains outside the
metallacyle, corresponds to Burk’s R-Duphos-type lig-
ands (ER ) E′ ) 2,5-dialkylphospholanyl),12 but was
also exemplified in C1 versions (E′ ) PPh2, ER* ) 4(S)-
i-Pr-1,3-oxazolinyl).13 The pattern C occurs as soon as
the complexing atom is stereogenic and corresponds to
the case of diphosphines with resolved asymmetric
phosphorus atoms. It has been exemplified in both C2
symmetric (e.g., E′ ) E*-R ) P*PhMe)14 and C1
symmetric versions (e.g., E′ ) PPh2, E*-R ) S*(O)-
Ar).15 In the hybrid pattern D, the stereogenic center
E* is created simultaneously with the complexation
process, while its configuration could be controlled by
an appending chiral substituent R(*). The substituent
R(*) then plays a secondary role in assessing the
chirality of the metal environment.
Sch em e 1. Ch ir a l Rh od iu m Ca ta lysts w ith
Bin a p h th iu m Meth ylid e Der iva tives a s Liga n d s
(Ar ) P h , Z ) H; Ar ) p-Tol, Z ) CO2Et, CO2t-Bu ,
CN)
Sch em e 2. P a tter n s for Assessin g Ch ir a lity in
Tr a n sition Meta l Com p lexes fr om Ch ela tin g
Liga n d s w ith a n Ar om a tic Br id ge
The pattern D is here envisionned for E′ ) PPh2 and
E-R* ) Ph2P+-CH-S*(O)Ar. The presence of an
asymmetric ylidic carbon directly bound to the metal
center would bring the chiral information inside the
metallacycle and as close as possible to the metal center.
To the best of our knowledge, enantiomerically pure
chiral complexes containing an asymmetric ylidic car-
bon-transition metal unit have not been reported.
chelating ligands are actually phosphino-phosphonium
ylide ligands with the same binaphthyl bridge as that
of (R)-binap.11a For (2′-di(p-tolyl)phosphinyl-1,1′-binaphth-
2-yl)di(p-tolyl)phosphonium carboxymethylide ligands
(“yliphos”), the stabilized nature of the free ylide favors
decoordination from the catalytic metal centers.7 This
hemilabile character may account for the poor enanti-
oselectivity observed.7a By contrast, the nonstabilized
(R)-binapium methylide ligand was shown to give a
stable chelated rhodium complex.8,9
In the latter complex, however, the atropochirality
results in a poor control (ca. 4 kcal mol-1) of the chiral
configuration of the flexible eight-membered rhoda-
cycle.8,10 We reasoned that a less flexible six-membered
rhodacycle would maintain a more stable chiral confor-
mation. As a shorter aromatic bridge, 1,2-phenylene was
selected to replace the 2,2′-1,1′-binaphthylene bridge
of binap. Contrary to the latter however, the 1,2-
phenylene bridge is intrinsically achiral. The optimal
way to introduce chirality was designed from the
following considerations. Several topological patterns
can be distinguished to assess chirality in the coordina-
tion sphere of the metal (Scheme 2). The pattern A,
where the (atropo)chirality is carried by the ligand
Resu lts a n d Discu ssion
Liga n d Syn th esis. Although a few (sulfinylmethyl)-
phosphoniums had been previously prepared by
Trippett16a and Aitken,16b,c optically active R-sulfi-
nylphosphonium ylides with a stereogenic sulfur center
have been described only recently by Mikolajczyk.17
The preparation of (S)-(p-tolylsulfinyl)methyl)triph-
enylphosphonium ylide 4a was based on the reaction
of (methyl)triphenylphosphonium ylide 1a with menthyl
(S)-p-tolylsulfinate 2 (Scheme 1). The semistabilized
ylide 4a can be used in situ for the preparation of chiral
(E)-alkenyl sulfoxides through classical Wittig reaction
with R,â-unsaturated aldehydes or protonated to the
corresponding ((p-tolylsulfinyl)methyl)triphenylphos-
phonium salt 4a H+.17
The above method was thus envisioned for the prepa-
ration of more functional derivatives such as (2-diphe-
nylphosphinophenyl)((p-tolylsulfinyl)methyl)diphenyl-
(12) (a) Burk, M. J .; Feaster, J . E.; Harlow, R. L. Tetrahedron
Asymmetry 1991, 2, 569. (b) Bayer, A.; Murszat, P.; Thewalt, U.; Rieger,
B. Eur. J . Inorg. Chem. 2002, 2614.
(13) Blacker, A. J .; Clarke, M.; Loft, M. S.; Mahon, M. F.; Williams,
J . M. J . Organometallics 1999, 18, 2867.
(8) About the methylbinapium ligand see: (a) Leglaye, P.;
Donnadieu, B.; Brunet, J .-J .; Chauvin, R. Tetrahedron Lett. 1998, 39,
9179. (b) Soleilhavoup, M.; Viau, L.; Commenges, G.; Lepetit, C.;
Chauvin, R. Eur. J . Inorg. Chem. 2003, 207.
(9) Viau, L.; Lepetit, C.; Commenges, G.; Chauvin, R. Organome-
tallics 2001, 20, 808.
(10) Canal, C.; Lepetit, C.; Soleilhavoup, M.; Chauvin, R. Unpub-
lished results.
(14) Allen, D. G.; Wild, S. B.; Wood, D. L. Organometallics 1986, 5,
1009, and refrences therein.
(15) Hiroi, K.; Suzuki, Y.; Kawagishi, R. Tetrahedron Lett. 1999,
40, 715.
(11) (a) Noyori, R.; Takaya, H. Acc. Chem. Res. 1990, 23, 345, and
references therein. (b) Hayashi, T. Acc. Chem. Res. 2000, 33, 354. (c)
Schmid, R.; Cereghetti, M.; Heiser, B.; Schoenholzer, P.; Hansen, H.
J . Helv. Chim. Acta 1988, 71, 895. (d) Schmid, R.; Broger, E. A.;
Cereghetti, M.; Crameri, Y.; Foricher, J .; Lalonde, M.; Mueller, R. K.;
Scalone, M.; Schoettel, G.; Zutter, U. Pure Appl. Chem. 1996, 68, 131.
(16) (a) Hamid, M.; Trippett, S. J . Chem. Soc. C 1968, 1612. (b)
A¨ıtken, R. A.; Drisdale, M. J .; Ryan, B. M. J . Chem. Soc. 1993, 1699.
(c) A¨ıtken, R. A.; Drisdale, M. J .; Ferguson, G.; Lough, A. J . J . Chem.
Soc., Perkin Trans. 1 1998, 875.
(17) Mikolajczyk, M.; Perlikowska, W.; Omelanczuk, J .; Cristau, H.-
J .; Peyraud-Darcy, A. J . Org. Chem. 1998, 63, 9716.

4812 Organometallics, Vol. 22, No. 23, 2003
Zurawinski et al.
F igu r e 1. Preparation of ((S)-sulfinylmethyl)triphenylphosphonium derivatives.
Ta ble 1. Com p a r a tive 31P NMR Da ta for
Meth yltr ia r ylp h osp h on iu m Sa lts, Ylid es, a n d Ylid e
Com p lexes
phosphonium ylides (ligand pattern D, Scheme 1). The
starting (2-diphenylphosphinophenyl)diphenylphos-
phonium methylide 1b was prepared by deprotonation
of the corresponding phosphino-phosphonium 1bH+,
itself selectively prepared from methyl iodide and 1,2-
diphenylphosphinobenzene.9,18 The phosphino-phos-
phonium iodide [1bH][I] was first converted to the
hexafluorophosphate [1bH][P F6]. Deprotonation of 1bH+
and subsequent addition of optically pure menthyl (S)-
p-tolylsulfinate 2 lead to the semistabilized (2-diphenyl-
phosphinophenyl)(sulfinylmethyl)diphenylphospho-
nium ylide 4b (Figure 1).
1
2
-a
+
+
Ph2P
J RhP Ph2P+ J PP
J RhP
PF6
[4a H][I]
19.80
[4bH][P F 6]
[4cH][P F 6]
[1b]b
-7.69
35.34
-11.40
23.30 23.5
28.51 6.5
27.30 29.9
23.30
-141.60
-141.45
[4a ]c
[4b]c
-10.60
27.90 21.6
[(binapCH2)-
Rh(cod)][BF4]d
[5a ][P F 6]
[5b][P F 6]
25.65 155.0 34.18
5.3
5.2
28.51 154.8 26.41 24.1
6.9 -141.70
-141.68
22.75 151.5 20.41 43.5 ≈0
As in the case of 4a H+,17 the initial (sulfinylmethyl)-
phosphonium 4bH+ is in situ deprotonated to the semi-
stabilized ylide 4b by the yet unreacted unstabilized
ylide 1b. After removal of [1bH][P F 6] by filtration, pro-
tonation of 4b with [NH4][PF6] led to (sulfinylmethyl)-
(2-(diphenylphosphinophenyl)diphenylphosphonium-
hexafluorophosphate [4bH][P F 6] in 50% yield. No oxy-
gen transfer from the sulfur atom to the phosphorus
atom was observed,19 but incidental oxidation of 4bH+
allowed for the isolation of the corresponding phosphine
oxide 4cH (Figure 1).
Septet, J PF ≈ 713 Hz. In Et2O at 81 MHz. c In THF at 81
a
1
b
d
MHz. Refs 9 and 10.
hydrogenation or hydrosilylation (see below) are rhod-
ium(I) complexes, the rhodium(I) complexes of 4b were
targeted.7,9,10,24 The chiral phosphoniophosphine 4bH+
was thus deprotonated back to the ylide 4b with n-BuLi
and in situ reacted with [Rh(cod)2][PF6] at room tem-
perature. The 31P NMR specrum of the crude material
exhibits two sets of three signals corresponding to a 9:1
mixture of epimeric complexes [5a ][P F 6] and [5b][P F 6],
which could be separated by chromatography over silica
The 31P NMR characteristics of the phosphinyl- and
phosphinoyl-phosphoniums 4bH+ and 4cH+ are con-
sistent with reported data on the unfunctional phos-
phonium 4a H+ (Table 1) and with further data on
o-Ph2P-C6H4-(Ph)2P ) X phosphazenes (X ) NH,
NSiMe3, NBn, NP(O)(OPh)2)20 and phosphine oxides
(X ) O).21
Rh od iu m Com p lexes. Until recently, most of rhod-
ium complexes with either independent phosphine and
phosphonium ylide ligands22 or chelating phosphino-
phosphonium ylide ligands23 were rhodium(III) com-
plexes. Since most common catalyst precursors for
1
gel (Figure 2). 1D and 2D H, 31P, 13C, and 103Rh NMR
data (see Experimental Section) are consistent with a
P,C chelating behavior of the ligand. While stabilized
phosphonium ylides R3PdCH-CO2R′ were reported to
react with [PdCl2(cod)] and [PtCl2(cod)] at an sp2 carbon
atom of the cyclooctadiene ligand,25 the cyclooctadiene
ligand remains intact in complexes 5+. When the
complexation reaction of the ylide is carried out at low
temperature (-45 °C), the phosphino-phosphonium
ylide complex 5+ is formed in 85% yield but with a
reversed diastereoselectivity: 5a +:5b+ ) 1:9 (Figure 2).
This suggests that 5a + is the thermodynamic epimer,
while 5b+ is the kinetic one (see below).
(18) Bowmaker, G. A.; Herr, R.; Schmidbaur, H. Chem. Ber. 1983,
116, 3576.
(19) Russel, G. A.; Becker, H.-D. J . Am. Chem. Soc. 1963, 85, 3406.
(20) Reed, R. W.; Santarsiero, B.; Cavell, R. G. Inorg. Chem. 1996,
35, 4292-4300.
3
+
(21) The reduced J PP coupling constant in the phosphonium-
phosphine oxide 4cH+ (ca. 7 Hz) is consistent with data reported for
the related derivatives o-OdPPh(R)-C6H4-(Ph)(R)P+-Me (R ) Me:
(23) (a) Werner, H.; Hofmann, L.; Paul, W. J . Organomet. Chem.
1982, 236, C65. (b) Werner, H.; Hofman, L.; Paul, W.; Schubert, U.
Organometallics 1988, 7, 1106.
(24) For an early example of a phosphine-phosphonium diylide
rhodium(I) complex related to Grey’s catalyst,5 see: Costa, T.; Schmid-
baur, H. Chem. Ber. 1982, 115, 1367.
3
3J PP ) 9 Hz; R ) Ph: J PP < 3 Hz).18
+
+
(22) (a) Paul, W.; Werner, H. Chem. Ber. 1985, 118, 3032. (b)
Werner, H.; Feser, R.; Paul, W.; Hofmann, L. J . Organomet. Chem.
1981, 219, C29. (c) Marder, T. B.; Fultz, W. C.; Calabrese, J . C.; Harlow,
R. L.; Milstein, D. J . Chem. Soc., Chem. Commun. 1987, 1543.
(25) Vicente, J .; Chicote, M.-T.; MacBeath, C.; Fernandez-Baeza, J .;
Bautista, D. Organometallics 1999, 18, 2677.

Rhodium Complexes with Ylide Ligands
Organometallics, Vol. 22, No. 23, 2003 4813
F igu r e 2. Diastereoselective preparation of both epimers of complex 5+.
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for Com p lex [5b][P F 6]
empirical formula
fw
C46H44F6OP3SRh
954.69
temperature
wavelength (Mo, KR)
cryst syst
180(2) K
0.71073 Å
orthorhombic
P212121
space group
unit cell dimens
a ) 14.561(5) Å
b ) 14.596(5) Å
8421(4) Å3
V
Z, calcd density
absorp coeff
F(000)
8, 1.506 mg‚m-3
0.632 mm-1
3904
cryst size
cryst form
cryst color
(0.42 × 0.35 × 0.14) mm
parallelepiped
orange
2θ range
3.3-52.1°
d(hkl) range
range for data collection
index ranges
12.453-0.809 Å
3.47-28.28°
F igu r e 3. ORTEP view of the X-ray crystal structure of
the complex [5a ][P F 6], with 50% probability displacement
ellipsoids for non-hydrogen atoms. Selected bond lengths
(Å): Rh-C(1) ) 2.152(3); S(1)-O(1) ) 1.495(3); P(2)-C(1)
) 1.764(4); P(2)-C(9) ) 1.808(4); C(1)-H(1) ) 0.85(4);
S(1)-C(1) ) 1.806(4); C(9)-C(14) ) 1.414(5); Rh-P(1) )
2.2730(10); P(1)-C(14) ) 1.835(3). Selected bond angles
(deg): C(1)-Rh-P(1))92.26(10);S(1)-C(1)-Rh )111.41(16);
P(2)-C(1)-Rh ) 100.76(16); C(14)-P(1)-Rh ) 116.70(12);
C(1)-P(2)-C(9) ) 109.91(17); C(9)-C(14)-P(1) ) 122.9(3);
C(14)-C(9)-P(2) ) 123.8(3); O(1)-S(1)-C(1) ) 111.07(17).
-19 e h e 19, -19 e k e 16,
-52 e l e 52
no. of reflns collected/unique
completeness to 2θ ) 56.56°
refinement method
68 906/10 449 [R(int) ) 0.0693]
99.5%
full-matrix least-squares on F2
no. of data/restraints/params 0449/0/528
goodness-of-fit on F2
final R indices [I > 2(I)]
R indices (all data)
1.091
R1 ) 0.0451, wR2 ) 0.0877
R1 ) 0.0486, wR2 ) 0.0897
0.01(3)
absolute struct param
largest diff peak and hole
0.715 and -0.495 e‚Å-3
IR data suggest that the sulfinyl group is not, or at
least not strongly, bonded to the rhodium atom. Indeed,
the stretching SdO vibration occurs at roughly the same
frequency in complexes 5a + (νS-O ) 1034 cm-1) and 5b+
(νS-O ) 1040 cm-1) as in the free (sulfinylmethyl)-
phosphonium 4H+ (νS-O ) 1052 cm-1). The most strik-
ing variation in the IR spectra concerns the C-P+
The structure and purity level of both complexes (to
be tested in catalytic experiments: see below) were
established by accurate HRMS, sharp melting points,
and NMR spectra (see Experimental Section and Sup-
porting Information). Furthermore, crystals of the 5a +
epimer deposited from a dichloromethane-diethyl ether
solution and allowed for an X-ray diffraction analysis
(Table 2, Figure 3). The ylidic carbon of 5a + has the
R-configuration. The six-membered metallacycle adopts
an envelop conformation where the rhodium atom lies
in the plane defined by both the phosphorus atoms and
the phenylene carbon atoms (Rh-(P1,C14,C9,P2) )
0.043 Å). The ylidic carbon (C1) is tilted out by the
dihedral angle (C1, P2, Rh, P1) ) 69.51°, namely, 1.122
Å above the plane (P1,C14,C9,P2). A similar tilting of
the methylide unit from the RhP2 plane was calculated
in a DFT model of the related rhodium complex [((R)-
binapCH2)Rh(cod)] (Scheme 1).9 Despite the long known
coordinating ability of the sulfinyl group toward rhod-
ium(I) centers, and especially when chelating,27 both the
sulfur and oxygen atoms occur at nonbonding distances
vibration: with respect to the free ligand 4bH+ (νP
+-C
) 1111 cm-1), it takes place at lower frequency in 5b+
(νP -C ) 1096 cm-1) and at higher frequency in 5a (νP
+
+-C
) 1118 cm-1). The NMR characteristics of both the
epimeric complexes are listed in Table 1. They compare
well with those of the [((R)-binapCH2)Rh(cod)]+ complex.
2
In particular, the J RhP coupling constant reaches ca. 5
Hz is both 5a + and [((R)-binapCH2)Rh(cod)]+ and van-
ishes for 5b+. The ylidic CH unit occurs at shielded H
1
and 13C chemical shifts. The deshielding of the proton
corresponds to a shielding of the carbon in 5a + (δ H
)
1
4.2 ppm, δ ) 38.4 ppm) by comparison with 5b+ (δ H
13
1
C
) 3.5 ppm, δ ) 45.4 ppm). The 103Rh chemical shifts
13
C
of 5b+ (+261.3 ppm) and 5a + (+170.0 ppm) fall in the
classical range for Rh(olefin)(P)(X) complexes. For com-
parison, the related orthometalated P,C complex (o-R2-
(26) (a) Mann, B. E. In Transition Metal Nuclear Magnetic Reso-
nance; Pregosin, P. S., Ed.; Studies in Inorganic Chemistry; Elsevier:
Amsterdam, 1991; Vol. 13, p 177. (b) Benn, R.; Rufinsla, Angew. Chem.,
Int. Ed. Engl. 1986, 25, 861.
(27) See for example: Alcock, N. W.; Brown, J . M.; Evans, P. L. J .
Organomet. Chem. 1988, 356, 233.
) +22 ppm.26 However,
103Rh
PC6H4)Rh(cod) occurs at δ
the rhodium atom is slightly more deshielded in 5b+
than in 5a +, and this might result in different catalytic
behaviors.

4814 Organometallics, Vol. 22, No. 23, 2003
Zurawinski et al.
namic diastereoisomeric ratio. In terms of free enthalpy
at 25-50 °C, the SS,RC isomer 5a + is therefore more
stable than the SS,SC isomer 5b+ by ca. 1.4 kcal‚mol-1
.
In acidic medium, the ylidic carbon-rhodium bond
is cleaved. No clean product could be identified from the
reaction of [5b][P F 6] with aqueous HCl in chloroform
at either 25 or -55 °C. In the presence of triphenylphos-
phine however, the noncoordinating anion of hexafluo-
rophosphoric acid (1 equiv of HPF6) allowed for the
formation of the free protonated ligand [4bH][P F 6]
along with the known complex [8][P F 6] (Figure 5).31 The
likely intermediate 72+ was not detected: the electro-
static repulsion of the cationic charges must indeed
favor the displacement of the phosphoniophosphine
ligand by a second neutral triphenylphosphine ligand
(Figure 5).
Ca ta lytic P r op er ties. As emphasized in the Intro-
duction, few catalytic studies of phosphonium ylide
transition metal complexes are available.5-7,9,10 The
challenge of the discovery of catalytic reactions cata-
lyzed by complexes bearing such persistent carbon
ligands is here tackled with complexes 5a + and 5b+.
Since diaminocarbenes behave as efficient persistent
carbon ligands in rhodium-catalyzed hydrosilylation of
ketones,1b,c hydrosilylation was first selected as a trial
reducing process. From a conceptual standpoint, beyond
the effect of the persistent Rh-C bond, the course of
the catalysis should be influenced by the (chiral) elec-
trostatic field generated by the phosphonium center and
embedding the rhodium center.32 Within a more general
prospect, it is worth noting that rhodium(I) complexes
of nondeprotonated phosphino-phosphonium ligands
were shown to be active in olefin hydrogenation in
biphasic media,33 and more recently in homogeneous
hydroformylation of 1-hexene34 and asymmetric hydro-
gen transfer to (Z)-R-acetamidocinnamic acid.35
Ca ta lytic Hyd r osilyla tion . Both epimers of the
complex 5+ in 1% catalytic ratio were found to sepa-
retely catalyze hydrosilylation of acetophenone 9 by Ph2-
SiH2 over a 20-40 h period at room temperature (Figure
6). As shown in Table 3, complex 5a + is definitely much
more selective than complex 5b+. Various solvents were
used, and the catalytic efficiency increases in the order
CH2Cl2 < no < THF. No “CCl4 effect” was observed.36
Regarding the enantioselectivity, complex 5b+ is
slightly more enantioselective than complex 5a +. In
THF, while 5b+ produces a 8% excess of (S)-(-)-
phenylethanol 12, 5a + produces a 5% excess of the
opposite enantiomer. Although not high in absolute
value, this reversal of enantioselectivity suggests that
F igu r e 4. Reversible deprotonation of epimeric complexes
5a + and 5b+, through the putative intermediate 6.
F igu r e 5. Acidic cleavage of the ylidic carbon-rhodium
bond by HPF6 in the presence of triphenylphosphine.
from the rhodium center (Rh‚‚‚O ) 4.6041(30) Å,
Rh‚‚‚S ) 3.2761(13) Å). This is in accordance with
the IR data discussed above.
Other structural features of the complex 5a + quali-
tatively compare with those of Cavell’s homologous (but
achiral) phosphino-phosphazene rhodium(I) complex
(P,N-η2-o-Ph2P-C6H4-Ph2P ) NSiMe3)RhCl(CO).20 In
particular, the critical bonds have the same order of
magnitude: Rh-C ) 2.152(3) Å in 5a + versus Rh-N )
2.146(6) Å in Cavell’s complex. The main difference
qualifying the ylidic carbon-nitrogen analogy resides
in a 10° difference between the critical angles: P-C-
Rh ) 100.76(16)° in 5a + versus P-N-Rh ) 109.9(4)°
in Cavell’s complex.20
The ylidic carbon is substituted by an unusual set of
substituents H, P+, S, and Rh. To the best of our
knowledge, this is the first example of a transition metal
ylide complex containing an asymmetric ylidic carbon
of definite absolute configuration. Let us, however,
mention Spannenberg’s doubly zwitterionic palladium-
(II) complex, where the relative configuration of two
ylidic carbons is spontaneously controlled during the
complexation of the achiral stabilized bisphosphonium
diylide ligand PhCO-CHdPPh2-CH2CH2-Ph2PdCH-
COPh at a PdCl2 center: the racemic dl isomer formed
selectively at the expense of the meso isomer.28
The configuration of the ylidic carbon of the pure
20
complexes 5a + ([R]D ) +58.4°) and 5b+ ([R]24
)
D
+106°) is stable. In basic medium, however, epimeriza-
tion of 5b+ to the thermodynamically more stable isomer
5a + takes place. After heating complex [5b][P F 6] in the
presence of triethylamine for 10 h in THF at 50 °C, the
final ratio 5b+:5a + ) 1:9 is identical to the crude
diastereoisomeric ratio obtained when [5][P F 6] is di-
rectly prepared at room temperature. The epimerization
likely proceeds through deprotonation of the secondary
asymmetric ylidic carbon to give a rhodaylide interme-
diate 6 (Figure 4). Similar complexes containing an
yldiide ligand,29 namely, an R3PdC(R′)-[M] unit, are
known.3,30 The adjacent sulfinyl group then controls the
approach of the proton and determines the thermody-
(31) (a)Wertz, U.; Brune, H.-A. J . Organomet. Chem. 1989, 360, 377.
(b) Schrock, R. R.; Osborn, J . A. J . Am. Chem. Soc. 1971, 93, 2397.
(32) (a) Brunet, J .-J .; Chauvin, R.; Commenges, G.;. Donnadieu,
B.; Leglaye, P. Organometallics 1996, 15, 1752. (b) Brunet, J .-J .;
Chauvin, R.; Chiffre, J .; Huguet, S.; Leglaye, P. J . Organomet. Chem.
1998, 566, 117. (c) Brunet, J .-J .; Chauvin, R.; Chiffre, J .; Donnadieu,
B.; Huguet, S.; Leglaye, P.; Mothes, E. Inorg. Chim. Acta 1999, 291,
300. (d) Chauvin, R. Eur. J . Inorg. Chem. 2000, 577.
(33) (a) Quayle, W. H.; Pinnavaia, T. J . Inorg. Chem. 1979, 18, 2840.
(b) Farzaneh, F.; Pinnavaia, T. J . Inorg. Chem. 1983, 22, 2216. (c)
Renaud, E.; Russel, R. B.; Fortier, S.; Brown, S. J .; Baird, M. C. J .
Organomet. Chem. 1991, 419, 403. (d) Renaud, E.; Baird, M. C. J .
Chem. Soc., Dalton Trans. 1992, 2905.
(28) Spannenberg, A.; Baumann, W.; Rosenthal, U. Organometallics
2000, 19, 3991.
(29) Goumri-Magnet, S.; Gronitzka, H.; Baceiredo, A.; Bertrand, G.
Angew. Chem., Int. Ed. 1999, 38, 578.
(30) See for example: Berno, P.; Gambarotta, S.; Kotila, S.; Erker,
G. Chem. Commun. 1996, 779.
(34) Hap, S.; Nieger, M.; Gudat, D.; Betke-Hornfeck, M.; Schramm,
D. Organometallics 2001, 20, 2679.
(35) Viau, L.; Chauvin, R. J . Organomet. Chem. 2002, 654, 180.
(36) (a) Brunner, H.; Obermann, U. Chem. Ber. 1989, 122, 499. (b)
Brunner, H.; Storiko, R. Eur. J . Inorg. Chem. 1998, 783, and references
therein.

Rhodium Complexes with Ylide Ligands
Organometallics, Vol. 22, No. 23, 2003 4815
Ta ble 3. Ca ta lytic Hyd osilyla tion of Acetop h en on e Ca ta lyzed w ith Com p lexes 5a + a n d 5b+
25
catalyst
solvent
time (h)
% conva
% yieldb
% selectivityc
[R]D
% eed
5b+
5b+
5b+
5b+
5a +
5a +
THF
20
40
40
40
40
40
nd
nd (60)
66 (52)
50 (39)
75 (60)
95 (79)
82 (70)
-3.5°
-0.9°
-1.4°
-1.8°
+2.3°
-0.3°
8
2
3
4
5
1
CH2Cl2
CH2Cl2:CCl4, 3:1
no
quant.
95
66
53
76
98
90
99
THF
CH2Cl2
97
91
a
b
% conv ) (10 + 11)/9 × 100. After hydrolysis. Isolated yields of 12 are given in parentheses. c In hydrosilylation product: 11/(9 +
d
20
10 + 11) × 100. Determined from the optical rotation of pure (R)-12: [R]D +45° (c 5, MeOH).
Ta ble 4. Ca ta lytic Hyd r ogen a tion of
(Z)-r-Aceta m id ocin n a m ic Acid 13 w ith Com p lexes
5a + a n d 5b+a
ee (%)b
25
catalyst
time (h) PH2 (bar) conv (%) [R]D
5b+
48
48
72
72
1
15
15
15
0
71
66
5b+
-1.8°
-0.7°
-1.2°
4
1
2
5b+ + PPh3
5a +
100
a
b
See Experimenttal Section. Estimated from the optical rota-
26
tion with respect to the reported value for pure (R)-14: [R]D
F igu r e 6. Hydrosilylation of acetophenone catalyzed by
complexes 5a + and 5b+.
-51.8° (c 1, EtOH).46
complexes, a resolved asymmetric ylidic carbon atom is
bound to the metal center. The reducing catalytic
efficiency of these complexes has been demonstrated and
dramatically fills the paucity of reported examples of
catalytically active phosphonium-ylide transition metal
complexes. The enantioselectivity of these catalytic
processes remains to be improved. The flexibility and/
or the absence of C2 symmetry of the (C,P,Rh,C,P+,C)
six-membered metallacycle might be responsible for the
lack of enantioselectivity. This challenge will be the goal
of future investigations.
F igu r e 7. Hydrogenation of (Z)-R-acetamidocinnamic acid
catalyzed by complexes 5a + and 5b+.
5a + and 5b+ behave as pseudoenantiomeric catalysts.
As anticipated in the Introduction, the sulfinyl chiral
center plays a secondary role in the chirality of the
rhodium coordination sphere.
Exp er im en ta l Section
It is worth noting that the catalytic propensity of
phosphinophosphonium ylide rhodium complexes for
hydrosilylation of acetophenone seems to be quite
general. Such an activity and 10% ee were indeed
provided by the homologous binapium methylide rhod-
ium complex.10
Reactions were carried out under a nitrogen atmosphere
using Schlenk tube and vacuum line techniques. THF and
ether were distilled over Na/benzophenone. Ethanol was
distilled over Drierite. Dichloromethane was distilled over
P2O5. Butyllithium was purchased from Aldrich as a 1.6 M
solution in hexane. 1,2-Diphenylphosphinobenzene and methyl
iodide were purchased from Fluka. Ammonium tetrafluorobo-
rate was purchased from Aldrich. [Rh(cod)2][BF4] was prepared
from [RhCl(cod)]2,38 itself prepared from cyclooctadiene and
RhCl3‚3H2O (J ohnson-Matthey) according to a modified pro-
cedure (no carbonate was added).39 [Rh(cod)2][BF4] was con-
verted to the [Rh(cod)2][PF6] by anion metathesis with 13 equiv
The catalytic properties were then evaluated in
another reducing catalytic process: hydrogenation.
Ca t a lyt ic H yd r ogen a t ion . The ylidic carbon-
rhodium bond of complexes 5a + and 5b+ is stable under
up to 15 bar of hydrogen atmosphere. This rather
surprising observation prompted us to test these com-
plexes for the hydrogenation of (Z)-R-acetamidocinnamic
acid 13, a reference substrate.37 Under 15 bar H2, each
epimer 5a + and 5b+ was found to be catalytically active
in 1% catalytic ratio (Figure 7). The stability of the
complex was confirmed by the absence of metallic
rhodium even after a 72 h, the required reaction time
to reach quantitative conversion. The enantioselectivity
in N-acetyl-(R)-phenylalanine 14 remained low (ca. 2%
with 5a + and 4% with 5b+). The addition of one catalytic
equivalent of triphenylphosphine did not improve the
activity nor the enantioselectivity (Table 4).
of KPF6 in
a CH2Cl2-H2O mixture. NMR spectra were
recorded in CDCl3 solution, on Bruker AC 200 and AMX 400
spectrometers. Positive chemical shifts at low field are ex-
pressed in ppm by internal reference to TMS for 1H and 13C
and by external reference to 85% H3PO4 in D2O for 31P. 103Rh
chemical shifts are given to high frequency of ¥(103Rh) ) 3.16
MHz. Optical rotations were measured in a 1 dm cell with a
Perkin-Elmer 241 photopolarimeter.
Cr ysta llogr a p h ic Stu d ies. Data were collected at low
temperature (T ) 180 K) on a STOE diffractometer using
graphite-monochromated Mo K radiation (λ ) 0.71073 Å) and
equipped with an Oxford Cryosystems cryostream cooler jet
cooler device. The final unit cell parameters were obtained by
means of a least-squares refinement performed on a set of 8000
well-measured reflections. A crystal decay was monitored, and
no significant fluctuations of intensities were observed during
Con clu sion
It has been shown that chiral phosphino(sulfinyl-
methyl)phosphonium ylides constitute a novel class of
hybrid P,C chelating ligands of rhodium(I). In these
(38) Schenck, T. G.; Downes, J . M.; Milne, C. R. C.; Mackenzie, P.
B.; Boucher, H.; Whelan, J .; Bosnisch, B. Inorg. Chem. 1985, 24, 2334.
(39) Giordano, G.; Crabtree, R. H.; Heintz, R. M.; Forster, D.; Morris,
D. E. In Inorganic Synthesis; Wiley: New York, 1991; Vol. 28, p 88.
(37) Kagan, H. B.; Dang, T. P. J . Am. Chem. Soc. 1972, 94, 6429.

4816 Organometallics, Vol. 22, No. 23, 2003
Zurawinski et al.
the data collection. Structure was solved by direct methods
using SIR9240 and refined by means of least-squares proce-
dures on F2 with the aid of the program SHELXL9741 included
in WinGX version 1.63.42 The atomic scattering factors were
taken from International Tables for X-Ray Crystallography.43
Hydrogens atoms were located on difference Fourier maps, but
introduced in the process of the refinement in idealized
positions using a riding model. The C-H distances were fixed
at 0.93 Å for C sp2 atoms and 0.96 Å for C sp3 atoms, with an
isotropic parameter at 20% higher than the the Ueq value of
the C sp2 atom to with they were attached and 50% higher for
the C sp3 atom. Methyl groups were refined by using a rigid
group with the torsion angle refined as a free variable. All non-
hydrogens atoms were anisotropically refined, and in the last
cycles of refinement a weighting scheme was used, where
weights are calculated from the following formula: w )
135.59, 135.42, 135.33, 134.70, 134.14, 133.58, 132.81, 132.05,
131.83, 131.18, 130.90, 30.58, 130.37, 129.61, 129.43, 129.33,
125.14, 124.57, 118.79, 118.11, 54.60 (P+CH2), 22.00 (CH3). 13C-
{1H} NMR (100.6 MHz, CDCl3): δ 143.74, 143.41 (dd, J CP
)
+
+
15.2 Hz, J CP ) 11.8 Hz), 139.35 (d, J CP ) 12.8 Hz), 139.23 (d,
+
+
J CP ) 10.4 Hz), 137.78 (dd, J CP ) 13.5 Hz, J CP )10.5 Hz),
+
+
135.95 (d, J CP ) 2.9 Hz), 135.58 (d, J CP ) 3.0 Hz), 135.42 (d,
+
+
J CP ) 2.3 Hz), 135.33 (d, J CP ) 11.0 Hz), 134.70 (d, J CP
)
+
4.6 Hz), 134.14 (d, J CP ) 20.1 Hz), 133.58 (d, J CP ) 11.1 Hz),
132.81 (d, J CP ) 16.5 Hz), 132.06 (d, J CP ) 3.9 Hz), 131.82 (d,
+
+
J CP ) 13.3 Hz), 131.18, 130.90 (d, J CP ) 13.2 Hz), 130.58 (d,
+
J CP )13.6 Hz), 130.37, 129.61, 129.42 (d, J CP ) 8.3 Hz), 129.33
+
(d, J CP ) 6.5 Hz), 125.15 (dd, J CP ) 88.3 Hz, J CP ) 37.6 Hz),
+
124.57, 118.79 (dd, J CP ) 89.4 Hz, J CP ) 2.7 Hz), 118.11 (d,
+
+
J CP ) 86.9 Hz), 54.61 (dd, J CP ) 50.5 Hz, J CP ) 21.0 Hz,
P+CH2), 22.00 (CH3). IR (KBr): 3052, 2920, 1640, 1483, 1440,
1111, 1052, 840, 741, 557 cm-1. FAB-MS m/z (rel int): 599
(62) ([4bH+]), 460 (15), 459 (44), 383 (100), 154 (24). HRMS
1/[2(Fo2) + (aP)2 + bP] where P ) (Fo + 2Fc2)/3. The absolute
2
configuration was assigned on the basis of the refinement of
+
the Flack’s enantiopole parameter, X, which is the fractional
calcd for C38H33OSP2 599.1727, found 599.1722. The purity
contribution of F(-h) to the observed structure amplitude,44
of the compound was established by its NMR spectra (see
Supporting Information).
as depicted in the following formula: Fo ) (1 - x)F(h)2
+
2
xF(-h)2. This parameter is sensitive to the polarity of the
structure. The Flack’s parameter was found close to 0, which
clearly indicated the good choice of the enantiomer refined.
Least-squares refinements were carried out by minimizing the
function w(Fo - Fc)2,where Fo and Fc are the observed and
calculated structure. The criteria for a satisfactory complete
analysis were the ratios of root-mean-square shift standard
deviation being less than 0.1 and no significant features in
final difference Fourier maps. Drawings of molecules are
performed by using the program ORTEP3 with 50% probability
displacement ellipsoids for non-hydrogen atoms.4546
Sp ectr oscop ic Ch a r a cter istics of [4cH][P F 6]. [4cH]-
[P F 6] was obtained by incidental oxidation upon prolonged
exposure to air during chromatography. 31P{1H} NMR (162
+
+
MHz, CDCl3): δ 35.39 (d, J PP ) 6.5 Hz, P(O)), 28.51 (d, J PP
) 6.5 Hz, P+), -141.42 (septet, J PF ) 712.9 Hz, PF6-). 1H NMR
(400 MHz, CDCl3): δ 7.85-7.15 (m, 28 H), 5.40 (dd, 1 H, 2J HH
2
2
≈ 13.5, J PH ) 15.1 Hz; CHHP+), 4.70 (dd, 1 H, J HH ) 13.5
Hz, J PH ) 4.4 Hz; CHHP+), 2.46 (s, 3 H, CH3). 13C{1H, 31P}
2
NMR (100.6 MHz, CDCl3): δ 143.44, 140.34, 139.86, 137.81,
137.38, 137.27, 135.75, 135.43, 135.32, 134.96, 134.68, 133.91,
133.62, 133.23, 132.48, 131.59, 131.03, 130.97, 130.12, 129.61,
+
(S)-[2-(Dip h en ylp h osp h in o)p h en yl][(p-tolylsu lfin yl)m -
eth yl]diph en ylph osph on iu m Hexaflu or oph osph ate [4bH]-
[P F 6]. To a stirred suspension of [2-(diphenylphosphino)-
phenyl] (methyl)diphenylphosphonium hexafluorophosphate
[1bH][P F 6] (1.0 g, 1.65 mmol) in diethyl ether (70 mL) at -20
°C was added dropwise a solution of n-BuLi (1.1 mL of 1.5 M
solution in hexane, 1.65 mmol). The cooling bath was removed,
and the mixture was allowed to warm to room temperature.
After 30 min the mixture was cooled to -20 °C and (S)-(-)-
menthyl p-toluenesulfinate (0.243 g, 0.83 mmol) was added.
After 10 min stirring at -20 °C and 30 min at room temper-
ature a precipitate of [2-(diphenylphosphino)phenyl]meth-
yldiphenylphosphonium hexafluorophosphate, insoluble in
Et2O, was filtered off, and the mixture was quenched with a
solution of ammonium hexafluorophosphate (0.26 g, 1.65
mmol) in THF (30 mL). Then, the solvents were evaporated,
water (30 mL) was added, and the mixture was extracted with
CH2Cl2 (3 × 30 mL). The organic layer was dried over Na2-
SO4. The solvent was evaporated, and the crude product was
purified by flash column chromatography on silica gel using
dichloromethane-acetone (20:0.5) as the eluent. Yield: 0.31
g (50%). Mp: 119 °C. [R]22D +61.8 (c 2.0, CH2Cl2). 31P{1H} NMR
129.58, 128.76, 128.65, 124.47, 121.38 (J P ) 86.4 Hz, J (O)-
C
PC ) 6.9 Hz), 120.32 (1J P ) 85.2 Hz), 119.33 (1J P ) 94.6
+
+
C
C
Hz), 56.66 (1J P ) 54.4 Hz), 22.00. (+)-ES-MS m/z: 615.2
+
C
([4cH+]). (-)-ES-MS m/z: 144.9 ([P F 6-]). The purity of the
compound was established by its NMR spectra (see Supporting
Information).
Rh od iu m Com p lexes [5][P F 6]. To a stirred solution of
[4bH][P F 6] (100 mg, 0.134 mmol) in THF (8 mL) at -20 °C
was added n-BuLi (84 µL of 1.6 M solution in hexane, 0.134
mmol). The cooling bath was removed, and the mixture was
allowed to warm to room temperature (orange solution). After
15 min bis(1,5-cyclooctadiene)rhodium(I) hexafluorophosphate
(61 mg, 0.132 mmol) was added, and the stirring was continued
for an additional 2 h. The solvent was evaporated, and the
crude mixture of two diastereomeric rhodium complexes (in
the ratio 5a +:5b+ ) 9:1) was purified by flash column chro-
matography (dichloromethane-acetone gradient), giving 104
mg (81%) of [5a ][P F 6] and 9 mg (7%) of [5b][P F 6].
In a similar experiment, addition of equimolar amounts of
bis(1,5-cyclooctadiene)rhodium(I) hexafluorophosphate to ylide
4 at -45 °C led to the mixture of diastereoisomeric rhodium
complexes in the opposite ratio (5a +:5b+ ) 1:9). Purification
of crude products by flash column chromatography gave 9 mg
(7%) of [5a ][P F 6] and 100 mg (78%) of [5b][P F 6] as orange
solids.
(162 MHz, CDCl3): δ 23.30 (d, J PP ) 23.5 Hz, P+), -7.69 (d,
+
J PP ) 23.5 Hz, P), -141.60 (septet, J PF ) 712.7 Hz, PF6-). 1H
+
NMR (400 MHz, CDCl3): δ 7.87-6.84 (m, 28 H), 5.04-4.98
(m, 2 H, CH2), 2.43 (s, 3 H, CH3). 13C{1H, 31P} NMR (100.6
MHz, CDCl3): δ 143.74, 143.41, 139.36, 139.23, 137.79, 135.95,
Com p lex [5b][P F 6] ((S)S(S)C Ep im er ). Mp: 155-156 °C.
[R]20 +63.1 (c 2.0, CH2Cl2). 31P NMR (162 MHz, CDCl3): δ
D
3
22.75 (dd, 1J PRh ) 151.5 Hz, 3J PP ) 43.5 Hz, P), 20.41 (d, J PP
+
+
(40) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J .
Appl. Crystallogr. 1993, 26, 343.
(41) Sheldrick, G. M. SHELX97 [includes SHELXS97, SHELXL97,
CIFTAB]-Programs for Crystal Structure Analysis (Release 97-2);
Institu¨t fu¨r Anorganische Chemie der Universita¨t: Tammanstrasse
4, D-3400 Go¨ttingen, Germany, 1998.
(42) Farrugia, L. J . Appl. Crystallogr. 1999, 32, 837.
(43) International Tables for X-Ray Crystallography; Kynoch
Press: Birmingham, England, 1974; Vol. IV.
(44) (a) Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876. (b)
Bernardinelli, G.; Flack, H. D. Acta Crystallogr. Sect. A 1985, 41, 500.
(45) ORTEP3 for Windows. Farrugia, L. J . J . Appl. Crystallogr.
1997, 30, 565.
) 43.5 Hz, P+), -141.68 (septet, 1J PF ) 713.2 Hz, PF6-). 103Rh
NMR (12.6 MHz, CDCl3): δ 261.29 (d, J PRh ) 152.2 Hz). 1H
NMR (400 MHz, CDCl3, T ) 253 K): δ 7.98-6.86 (m, 28 H),
5.23 (br s, 1 H, cod-CH), 3.53 (br s, 1 H, P+CH), 3.45-3.36 (m,
3 H, cod-CH), 2.51-2.26 (m, 2H, cod-CH2), 2.48 (s, 3 H, CH3),
2.24-2.05 (m, 1H, cod-CH2), 2.02-1.58 (m, 5H, cod-CH2). 13C-
{1H, 31P} NMR (100.6 MHz, CDCl3): δ 143.37, 141.81, 139.81,
139.00, 136.61, 136.06, 135.83, 134.90, 134.84, 133.96, 133.39,
132.41, 131.89, 131.58, 131.16, 131.10, 130.69, 130.59, 130.13,
129.49, 129.29, 128.59, 126.61, 123.89, 123.32, 120.73, 99.60
(d, J CRh ) 10.2 Hz, cod-CH), 94.75 (d, J CRh ) 8.4 Hz, cod-CH),
(46) Knoop, F.; Blanco, J . G. Z. Phys. Chem. 1925, I146, 272.

Rhodium Complexes with Ylide Ligands
Organometallics, Vol. 22, No. 23, 2003 4817
91.52 (d, J CRh ) 6.7 Hz, cod-CH), 83.17 (d, J CRh ) 9.0 Hz, cod-
CH), 45.44 (d, J CRh ) 26.2 Hz, P+CH), 32.52 (cod-CH2), 32.91
(cod-CH2), 28.52 (cod-CH2), 27.86 (cod-CH2), 2.07 (CH3). 13C-
809.1636. The purity of the compound (to be used in catalytic
experiments) was established by its NMR spectra (see Sup-
porting Information).
Single crystals of [5a ][P F 6] suitable for X-ray diffraction
analysis were obtained by crystallization from CH2Cl2-Et2O.
It allowed for the assignment of the (S)s(R)c configuration for
the epimer 5a +. The configuration of the epimer 5b+ is
therefore (S)s(S)c.
{1H} NMR (100.6 MHz, CDCl3): δ 143.37 (d, J CP ) 14.8 Hz),
+
+
141.80, 139.81 (dd, J CP ) 31.0 Hz, J CP ) 7.5 Hz), 139.00 (dd,
+
+
J CP ) 9.3 Hz, J CP ) 9.3 Hz), 136.61 (d, J CP ) 8.6 Hz), 136.05
+
(d, J CP ) 3.6 Hz), 135.84 (d, J CP ) 14.0 Hz), 134.90 (d, J CP
)
+
+
3.0 Hz), 134.85 (d, J CP ) 3.0 Hz), 133.97 (d, J CP ) 8.0 Hz),
+
133.40 (d, J CP ) 10.5 Hz), 132.41 (d, J CP ) 9.8 Hz), 131.88 (d,
Rea ction of [5b][P F 6] w ith HP F 6 a n d P P h 3. F or m a tion
of Com p lex [8][P F 6]. To a stirred solution of rhodium
complex (S)S(S)C isomer, 5b+ (15 mg, 0.016 mmol) and triph-
enylphosphine (4.1 mg, 0.016 mmol) in dichloromethane (1 mL)
at -20 °C was added hexafluorophosphoric acid (2 µL of 65%
HPF6 in water, 0.016 mmol). After 20 min at -20 °C and 30
min at room temperature the solvent was evaporated and the
31P NMR spectrum was recorded. Signals from starting ligand
[4bH][P F 6] and complex [(PPh3)2Rh(cod)][PF6], [8][P F 6], were
observed.26 Crude product [8][P F 6] was purified by column
chromatography. 31P NMR (81 MHz, CDCl3): δ 26.57 (d, 1J RhP
+
+
J CP ) 13.0 Hz), 131.58 (dd, J CP ) 41.3 Hz, J CP ) 9.6 Hz),
+
131.15, 131.09, 130.68 (d, J CP ) 11.8 Hz), 130.59, 130.13 (d,
+
J CP ) 12.7 Hz), 129.49 (d, J CP ) 10.4 Hz), 129.29 (d, J CP
)
+
9.4 Hz), 128.60 (dd, J CP ) 34.2 Hz, J CP ) 19.1 Hz), 126.62
+
+
(dd, J CP ) 61.4 Hz, J CP ) 5.0 Hz), 123.89, 123.33 (dd, J CP
)
+
70.4 Hz, J CP ) 19.1 Hz), 120.74 (dd, J CP ) 79.5 Hz, J CP ) 7.0
Hz), 99.61 (dd, J CRh ) 10.1 Hz, J CP ) 4.0 Hz, cod-CH), 94.74
(d, J CRh ) 9.0 Hz), 91.53 (dd, J CP ) 17.7 Hz, J CRh ) 7.0 Hz,
cod-CH), 83.17 (d, J CRh ) 9.1 Hz, cod-CH), 45.44 (ddd, J CRh
)
26.2 Hz, J CP ) 23.0 Hz, J CP ) 7.0 Hz, P+CH), 35.51 (cod-CH),
32.90 (d, J CP ) 5.0 Hz, cod-CH), 28.52 (cod-CH), 27.87 (cod-
CH2), 22.03 (CH3). IR (KBr): 3054, 2920, 1638, 1481, 1437,
1096, 1040, 837, 742, 693, 557 cm-1. FAB-MS m/z (rel int):
+
1
) 145.3 Hz); -144.04 ppm (sept, J PF ) 712.7 Hz).
Asym m etr ic Hyd r ogen a tion of (Z)-r-Aceta m id ocin -
n a m ic Acid . To (Z)-R-acetamidocinnamic acid (0.1 g, 0.49
mmol) and the rhodium complex (4.6 mg, 0.005 mmol, 1 mol
%) was added methanol (4 mL), and the mixture was stirred
under reaction conditions specified in Table 2. After the quoted
time, the solution was evaporated to dryness and the conver-
809 (84) [C46H44OSRhP2+], 701 (58), 670 (26), 549 (100), 460
+
(18), 459 (43), 154 (38). HRMS calcd for C46H44OSRhP2
809.1636, found 809.1635.
:
The purity of the compound (to be used in catalysis) was
established by its NMR spectra (see Supporting Information).
Com p lex [5a ][P F 6] ((S)s(R)c Ep im er ). Mp: 149-151 °C.
1
sion was determined by H NMR spectroscopy. Depending on
the conversion, one of the following procedures was used to
remove the catalyst: (A) In the case of 100% conversion the
catalyst was removed by extracting the residue with dichlo-
romethane (3 × 0.5 mL). (B) In the case of partial conversion
the residue was dissolved in 0.5 M NaOH and extracted with
ether (3 × 20 mL). The aqueous phase was acidified with dilute
HCl, extracted with ether (3 × 20 mL), and washed with brine.
The ethereal phase was dried over NaSO4 and evaporated to
dryness.
[R]24 +106.4 (c 1.1, CH2Cl2). 31P NMR (162 MHz, CDCl3): δ
D
+
+
28.51 (dd, J PRh ) 154.8 Hz, J PP ) 24.1 Hz, P), 26.41 (dd, J PP
) 24.1 Hz, J P
) 6.9 Hz, P+), -141.70 (septet, J PF ) 712.7
+
Rh
Hz, PF6-). 103Rh NMR (12.6 MHz, CDCl3): δ 170.02 (d, J PRh
)
153.2 Hz). 1H NMR (400 MHz, CDCl3, T ) 253 K): δ 7.96-
7.10 (m, 28 H), 4.75 (br s, 1 H, cod-CH), 4.18 (q, J ) 2.8 Hz, 1
H, P+CH), 3.65 (br s, 1 H, cod-CH), 3.57 (br s, 1 H, cod-CH),
3.40 (br s, 1 H, cod-CH), 2.40 (s, 3 H, CH3), 2.10-1.46 (m, 7
H, cod-CH2), 1.31-1.17 (m, 1 H, cod-CH2). 13C{1H, 31P} NMR
(100.6 MHz, CDCl3): δ 144.63, 143.26, 138.91, 138.03, 137.10,
136.59, 135.95, 134.57, 134.29, 134.09, 133.39, 133.32, 132.38,
131.84, 131.82, 131.73, 130.65, 130.43, 129.99, 129.91, 129.81,
129.65, 126.16, 125.87, 125.75, 123.47, 103.73 (d, J CRh ) 6.9
Hz, cod-CH), 101.51 (d, J CRh ) 6.8 Hz, cod-CH), 89.24 (d, J CRh
) 8.6 Hz, cod-CH), 88.60 (d, J CRh ) 9.1 Hz, cod-CH), 38.36 (d,
J CRh ) 23.3 Hz, P+CH), 31.40 (cod-CH2), 30.37 (cod-CH2), 30.10
(cod-CH2), 29.35 (cod-CH2), 22.27 (CH3). 13C{1H} NMR (100.6
Asym m etr ic Hyd r osilyla tion of Acetop h en on e. To a
stirred solution of rhodium complex (8 mg, 0.008 mmol, 1 mol
%) and acetophenone (0.1 g 0.83 mmol) in appropriate solvent
(1 mL) (see Table 3) was added diphenylsilane (0.16 g, 0.87
mmol). Stirring was continued for the quoted period. To
determine the chemical and hydrosilylation yield, a sample
1
was taken and a H NMR spectrum was recorded. The reaction
mixture was quenched by addition of methanol (0.5 mL)
containing 1% of p-toluenesulfonic acid. After srirring at room
temperature for 30 min the solvents were evaporated in vacuo,
and the crude product was purified by column chromatography
using diethyl ether-pentane (1:3) as the eluent.
+
MHz, CDCl3): δ 144.63 (d, J CP ) 11.1 Hz), 143.25, 138.89 (d,
+
+
J CP ) 9.3 Hz), 138.02 (dd, J CP ) 12.1 Hz, J CP ) 9.9 Hz),
+
137.10 (br s), 136.59 (dd, J CP ) 35.8 Hz, J CP ) 7.2 Hz), 135.95
(d, J CP ) 3.8 Hz), 134.56, 134.27, 134.09 (d, J CP ) 11.3 Hz),
+
133.39 (d, J CP ) 12.1 Hz), 133.32 (d, J CP ) 10.3 Hz), 132.38
Ack n ow led gm en t. This work was performed with
the support of the Laboratoire Europe´en Associe´ (LEA)
financed by the CNRS (France) and with the support
of the European Commission within the 5th Framework
Programme (Contract ICA-CT-2000-70021-Center of
Ecellence).
+
+
(d, J CP ) 9.6 Hz), 131.84, 131.82, 131.73 (dd, J CP ) 13.1 Hz,
+
J CP ) 38.3 Hz), 130.64, 130.42 (d, J CP ) 12.8 Hz), 129.99 (d,
+
+
J CP ) 9.5 Hz), 129.89 (d, J CP ) 9.7 Hz), 129.81 (dd, J CP
)
12.1 Hz, J CP ) 24 Hz), 129.65 (d, J CP ) 10.0 Hz), 126.17 (d,
+
+
J CP ) 100.0 Hz), 125.87, 125.75 (d, J CP ) 71.9 Hz), 123.48
+
(dd, J CP ) 87.5 Hz, J CP ) 20.1 Hz), 103.71 (ddd, J CRh ) 7.0
+
Hz, J CP ) 9.1 Hz, J CP ) 3.0 Hz, cod-CH), 101.52 (dd, J CP
)
10.1 Hz, J CRh ) 7.0 Hz, cod-CH), 89.23 (d, J CRh ) 9.3 Hz, cod-
CH), 88.63 (d, J CRh ) 8.7 Hz, cod-CH), 38.36 (ddd, J CRh )23.3
Su p p or tin g In for m a tion Ava ila ble: Full listings of
crystallographic data, atomic parameters, atomic coordinates,
Hz, J CP ) 24.8, J CP ) 6.4 Hz, P+CH), 31.37 (cod-CH2), 30.35
+
1
bond distances, and bond angles for [5a ][P F 6] and H, 31P, and
(cod-CH2), 30.10 (cod-CH2), 29.36 (cod-CH2), 22.28 (CH3). IR
13C NMR spectra of compounds [4bH][P F 6], [4cH][P F 6], [5a ]-
[P F 6], and [5b][P F 6]. This material is available free of charge
via the Internet at http://pubs.acs.org.
(KBr): 3060, 2919, 1637, 1482, 1438, 1118, 1034, 837, 742,
715, 693, 558 cm-1. FAB-MS m/z (rel int): 809 (100) [C46H44
-
OSRhP2+], 701 (28), 670 (38), 549 (76), 459 (20), 307 (36), 154
+
(92). HRMS calcd for
C
46H44OSRhP2
:
809.1636, found
OM030343G