Novel chiral ligands, diferrocenyl dichalcogenides and their derivatives, for rhodium- and iridium-catalyzed asymmetric hydrosilylation

Article abstract of DOI:10.1021/om950533u

As chiral ligands for transition metal complex-catalyzed asymmetric reactions, a variety of novel chiral ferrocenyl chalcogen compounds, which possess planar chirality due to the 1,2-unsymmetrically disubstituted ferrocene structure, have been prepared from chiral ferrocenes. There are seven diferrocenyl dichalcogenides (4-10), nine alkyl or aryl ferrocenyl chalcogenides (11-19), two bis(ferrocenylseleno)alkanes (20 and 21), two 1-(phenylchalcogeno)-1-[2-(diphenylphosphino)ferrocenyl]ethanes (22 and 24), and two 1-(phenylchalcogeno)-1-[1′,2-bis(diphenylphosphino)ferrocenyl]ethanes (23 and 25). 2,3-O,O′-Isopropylidene-2,3-dihydroxy-1,4-bis(phenylchalcogeno)butanes (26-28) are also synthesized. The Rh(I) complex-catalyzed hydrosilylation of ketones with diphenylsilane in the presence of these chiral ligands including the reported [R,S;R,S]-bis[2-[1-(dimethylamino)ethyl]ferrocenyl] dichalcogenides (1-3), followed by hydrolysis with dilute HCl, affords the corresponding chiral alcohols (R-configuration) in moderate to quantitative yield with up to 88% enantiomeric excess (ee). Similar treatment of acetophenone in the presence of diferrocenyl dichalcogenides (1, 2, 3, and 10) and a catalytic amount of Ir(I) complex gives chiral 1-phenylethanol of the opposite configuration (S) compared with the Rh case in high yield with up to 23% ee. The new complex prepared from a cationic rhodium compound and the diferrocenyl diselenide (2) shows an activity for asymmetric hydrosilylation of acetophenone to afford 1-phenylethanol in 60% chemical yield with 60% ee. Asymmetric hydrosilylation of imines and asymmetric hydrogenation of an enamide also proceed smoothly using the Rh(I)-diselenide (2) catalytic system to give the corresponding sec-amines and amide with up to 53% and 69% ee, respectively. A catalytic cycle involving the formation of tetracoordinated rhodium(I)-dichalcogenide complex (two Se and two N atoms to one Rh) followed by oxidative addition of the Si-H bond to Rh(I) and carbonyl addition to the produced rhodium(III) hydride complex is proposed for hydrosilylation of ketones.

Full text of DOI:10.1021/om950533u

370
Organometallics 1996, 15, 370-379
Novel Ch ir a l Liga n d s, Difer r ocen yl Dich a lcogen id es a n d
Th eir Der iva tives, for Rh od iu m - a n d Ir id iu m -Ca ta lyzed
Asym m etr ic Hyd r osilyla tion
Yoshiaki Nishibayashi,† Kyohei Segawa,† J ai Deo Singh,† Shin-ichi Fukuzawa,‡
Kouichi Ohe,† and Sakae Uemura*,†
Division of Energy and Hydrocarbon Chemistry, Graduate School of Engineering,
Kyoto University, Sakyo-ku, Kyoto 606-01, J apan, and Faculty of Science and Engineering,
Chuo University, Bunkyo-ku, Tokyo 112, J apan
Received J uly 11, 1995X
As chiral ligands for transition metal complex-catalyzed asymmetric reactions, a variety
of novel chiral ferrocenyl chalcogen compounds, which possess planar chirality due to the
1,2-unsymmetrically disubstituted ferrocene structure, have been prepared from chiral
ferrocenes. There are seven diferrocenyl dichalcogenides (4-10), nine alkyl or aryl ferrocenyl
chalcogenides (11-19), two bis(ferrocenylseleno)alkanes (20 and 21), two 1-(phenylchalco-
geno)-1-[2-(diphenylphosphino)ferrocenyl]ethanes (22 and 24), and two 1-(phenylchalcogeno)-
1-[1′,2-bis(diphenylphosphino)ferrocenyl]ethanes (23 and 25). 2,3-O,O′-Isopropylidene-2,3-
dihydroxy-1,4-bis(phenylchalcogeno)butanes (26-28) are also synthesized. The Rh(I)
complex-catalyzed hydrosilylation of ketones with diphenylsilane in the presence of these
chiral ligands including the reported [R,S;R,S]-bis[2-[1-(dimethylamino)ethyl]ferrocenyl]
dichalcogenides (1-3), followed by hydrolysis with dilute HCl, affords the corresponding
chiral alcohols (R-configuration) in moderate to quantitative yield with up to 88% enantio-
meric excess (ee). Similar treatment of acetophenone in the presence of diferrocenyl
dichalcogenides (1, 2, 3, and 10) and a catalytic amount of Ir(I) complex gives chiral
1-phenylethanol of the opposite configuration (S) compared with the Rh case in high yield
with up to 23% ee. The new complex prepared from a cationic rhodium compound and the
diferrocenyl diselenide (2) shows an activity for asymmetric hydrosilylation of acetophenone
to afford 1-phenylethanol in 60% chemical yield with 60% ee. Asymmetric hydrosilylation
of imines and asymmetric hydrogenation of an enamide also proceed smoothly using the
Rh(I)-diselenide (2) catalytic system to give the corresponding sec-amines and amide with
up to 53% and 69% ee, respectively. A catalytic cycle involving the formation of tetracoor-
dinated rhodium(I)-dichalcogenide complex (two Se and two N atoms to one Rh) followed
by oxidative addition of the Si-H bond to Rh(I) and carbonyl addition to the produced
rhodium(III) hydride complex is proposed for hydrosilylation of ketones.
In tr od u ction
those catalytic reactions,4,5 the phosphines posssessing
a characteristic nature in that structural modification
can be readily made by introduction of a desired
functional group on the ferrocene ring to match a variety
of asymmetric reactions: i.e., rhodium-catalyzed hydro-
genation,6 palladium-catalyzed allylic substitution reac-
tions,7 and gold- or silver-catalyzed aldol-type reactions
of isocyano carboxylates.8
We are currently interested in the preparation of
optically active [R,S;R,S]- and [S,R;S,R]-bis[2-[1-(di-
methylamino)ethyl]ferrocenyl] dichalcogenides [abbrevi-
ated as (R,S)- and (S,R)-(Fc*E)2; E ) S, Se, and Te] and
their stoichiometric use for asymmetric selenoxide
elimination,9ab [2,3]sigmatropic rearrangement,9a,b and
nucleophilic ring-opening of meso-epoxides,9c in which
In transition metal-catalyzed asymmetric reactions,
optically active phosphine compounds have been known
to be effective chiral ligands.1 Thus, Kagan et al. and
Knowles et al. found that 2,3-O,O′-isopropylidene-2,3-
dihydroxy-1,4-bis(diphenylphosphino)butane (DIOP) acted
as an effective ligand for rhodium-catalyzed asymmetric
hydrogenation of enamides,2 while Noyori and Takaya
et al. developed the utility of 2,2′-bis(diphenylphos-
phino)-1,1′-binaphthyl (BINAP) in various types of
asymmetric reactions catalyzed by transition metal
complexes.3 On the other hand, Hayashi et al. intro-
duced the ferrocenylphosphines as chiral ligands for
† Kyoto University.
‡ Chuo University.
X Abstract published in Advance ACS Abstracts, November 15, 1995.
(1) For an example : Brunner, H.; Zettlmeier, W. Handbook of
Enantioselective Catalysis with Transition Metal Compounds; VCH:
Weinheim, Germany, 1993.
(2) (a) Kagan, H. B.; Dang, T. P. J . Am. Chem. Soc. 1972, 94, 6429.
(b) Knowles, W. S.; Sabacky, M. J .; Vineyard, B. D. J . Chem. Soc.,
Chem. Commun. 1972, 10. (c) Vineyard, B. D.; Knowles, W. S.;
Sabacky, M. J .; Backman, G. L.; Weinkauff, D. J . J . Am. Chem. Soc.
1977, 99, 5946.
(4) Hayashi, T.; Mise, T.; Fukushima, M.; Kagotani, M.; Nagashima,
N.; Hamada, Y.; Matsumoto, A.; Kawakami, S.; Konishi, M.; Yama-
moto, K.; Kumada, M. Bull. Chem. Soc. J pn. 1980, 53, 1138.
(5) Sawamura, M.; Ito, Y. Chem. Rev. 1992, 92, 867.
(6) (a) Hayashi, T.; Kawamura, N.; Ito, Y. J . Am. Chem. Soc. 1987,
109, 7876. (b) Hayashi, T.; Kawamura, N.; Ito, Y. Tetrahedron Lett.
1988, 29, 5969.
(7) For an example: Hayashi, T. Catalytic Asymmetric Synthesis;
Ojima, I., Ed.; VCH: New York, 1993; Chapter 7.1.
(8) For an example: Sawamura, M.; Ito, Y. Catalytic Asymmetric
Synthesis; Ojima, I., Ed.; VCH: New York, 1993; Chapter 7.2.
(3) For examples: (a) Noyori, R.; Takaya, H. Acc. Chem. Res. 1990,
23, 345. (b) Takaya, H.; Ohta, T.; Noyori, R. Catalytic Asymmetric
Synthesis; Ojima, I., Ed.; VCH: New York, 1993; Chapter 1.
0276-7333/96/2315-0370$12.00/0 © 1996 American Chemical Society

Rh- and Ir-Catalyzed Hydrosilylation
Organometallics, Vol. 15, No. 1, 1996 371
Sch em e 1
F igu r e 1. Crystal structure of 8.
derived from the previously reported [R,S;R,S]-bis[2-
[1-(dimethylamino)ethyl]ferrocenyl] diselenide (2) [1 for
(R,S)-(Fc*S)2 and 3 for (R,S)-(Fc*Te)2]9 by several
transformations. Treatment of 2 with methyl iodide
afforded its ammonium salt 4 which was transformed
to compound 5 in 35% overall isolated yield with
complete retention of configuration by the reaction with
pyrrolidine (Scheme 1).4,12 Treatment of 2 with an
excess of acetic anhydride at room temperature afforded
the optically pure acetate 6 of the same configuration4
in 62% isolated yield which was then hydrolyzed to the
alcohol 7 by treatment with silica gel in 60% isolated
yield. Interestingly, a slow recrystallization of 7 from
dichloromethane at room temperature afforded a single
crystal of the diselenide having a nine-membered ring
8 and its structure was fully characterized by X-ray
crystallography (Figure 1).13 Its absolute configuration
was clarified to be R,S where the configuration around
the chiral carbon is R, showing complete retention at
this carbon during the transformation from 2 to 6, 7,
and 8.
Next, we envisaged preparing novel dichalcogenides
having a chiral sulfoxide moiety on the ferrocene ring
which might show activity as chiral ligands different
from 2-8. Treatment of (R)-ferrocenyl p-tolyl sulf-
oxide, which can be prepared easily by the Anderson
method,14 with lithium diisopropylamide (LDA) at -78
°C, followed by addition of elemental sulfur and air
oxidation, afforded an enantiomeric mixture of bis[2-
(p-tolylsulfinyl)ferrocenyl] disulfide which consisted
mainly of the (R,S)-isomer in accordance with the
reported high diastereoselective lithiation (>99% de)14
of the ferrocene (Scheme 2). By purification via column
chromatography on SiO2, pure (R,R)-disulfide 9 was
obtained in 23% isolated yield. The corresponding pure
the planar chirality of ferrocenes played a most impor-
tant role for the stereoselection. As a next step, we
envisaged to use these chiral dichalcogenides as ligands
for catalytic asymmetric reactions. When hydrosilyl-
ation of acetophenone with diphenylsilane followed by
acid hydrolysis was attempted in the presence of a
catalytic amount of [Rh(COD)Cl]2 and (Fc*Se)2 in
benzene at 25 °C, a nearly quantitative yield of 1-phen-
ylethanol with modest enantiomeric excess (ee) was
obtained. The result was somewhat unexpected because
it has been known that many organochalcogen com-
pounds interacted with transition metal salts to afford
stable coordination compounds which might be unsuit-
able for transition metal-catalyzed reactions.10 It
prompted us to examine such asymmetric reactions in
more detail by designing and preparing various types
of chiral diferrocenyl dichalcogenides and chalcogeno-
group containing ferrocenes. We report here the results
of Rh(I)- and Ir(I)-catalyzed asymmetric hydrosilylation
of ketones, imines, and an enamide using (Fc*E)2 and
other related compounds as chiral ligands.11
Resu lts a n d Discu ssion
Syn t h esis of Ch ir a l Difer r ocen yl Dich a lco-
gen id es. A variety of diferrocenyl diselenides could be
(9) (a) Nishibayashi, Y.; Singh, J . D.; Uemura, S.; Fukuzawa, S.
Tetrahedron Lett. 1994, 35, 3115. (b) Nishibayashi, Y.; Singh, J . D.;
Fukuzawa, S.; Uemura, S. J . Org. Chem. 1995, 60, 4114. (c) Nishiba-
yashi, Y.; Singh, J . D.; Fukuzawa, S.; Uemura, S. J . Chem. Soc., Perkin
Trans. 1, in press.
(10) For examples (a) Murray, S. G.; Hartley, F. R. Chem. Rev. 1981,
81, 365. (b) Gysling, H. J . The Chemistry of Organic Selenium and
Tellurium Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: New
York, 1986; Vol. 1, p 679.
(11) Preliminary communication: Nishibayashi, Y.; Singh, J . D.;
Segawa, K.; Fukuzawa, S.; Uemura, S. J . Chem. Soc., Chem. Commun.
1994, 1375.
(12) Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi,
I. J . Am. Chem. Soc. 1970, 92, 5396. Marquarding, D.; Burghard, H.;
Ugi, I.; Urban, R.; Klusacek, H. J . Chem. Res. (S) 1977, 82.
(13) The sulfur analogue of 8 was also formed and similarly fully
characterized.
(14) Rebiere, F.; Riant, O.; Ricard, L.; Kagan, H. B. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 568.

372 Organometallics, Vol. 15, No. 1, 1996
Nishibayashi et al.
Sch em e 2
Sch em e 4
Sch em e 3
Sch em e 5
(R,S)-diselenide 10 was similarly prepared in 20%
isolated yield, while the attempts for preparation and
isolation of the corresponding pure ditelluride were
unsuccessful.
Syn th esis of Ch ir a l Ar yl a n d Alk yl F er r ocen yl
Ch a lcogen id es. Treatment of (R)-[1-(dimethylamino)-
ethyl]ferrocene with sec-butyllithium followed by reac-
tion with diphenyl disulfide afforded an enantiomeric
mixture of [1-(dimethylamino)ethyl]ferrocenyl phenyl
sulfide which consisted mainly of the (R,S)-isomer, and
purification with column chromatography on SiO2 gave
(R,S)-sulfide 11 in pure form in 42% isolated yield
(Scheme 3). Similarly, other chiral aryl ferrocenyl
chalcogenides such as (R,S)-ferrocenyl phenyl selenide
(12) and telluride (13) and (R,S)-ferrocenyl 2,4,6-triiso-
propylphenyl selenide (14) were prepared by reaction
with the corresponding diphenyl dichalcogenides and
2,4,6-triisopropylphenylselenenyl bromide and isolated
in 56%, 51%, and 34% yields, respectively. Attempts
to prepare the (R,S)-ferrocenyl 2,4,6-tri-tert-butylphenyl
selenide were unsuccessful.
On the other hand, novel (R,S)-alkyl ferrocenyl se-
lenides (15-19) were prepared by the reaction of chiral
ferrocenyl selenide anion derived from 2 with the
corresponding alkyl halides in 38-82% isolated yield
(Scheme 4). However, the expected selenides were not
produced in the case of R ) i-Pr and t-Bu. When the
anion derived from 2 was reacted with 1,3-dibromo-
propane (n ) 3) and 1,5-dibromopentane (n ) 5),
[R,S;R,S]-alkanes possessing two ferrocenylselenium
moieties such as 20 and 21 were produced both in 55%
isolated yield (Scheme 4). With 1,4-dibromobutane (n
) 4), however, the corresponding compound was not
produced in accordance with the reported result15 using
phenyl selenide anion (PhSe-) where the internal quat-
ernization is much faster than nucleophilic attack of the
anion upon another bromide.
ferrocene ring16 promoted us to attempt the introduction
of a chalcogeno moiety into the side chain of ferro-
cenylphosphines. As it has been known that the nucleo-
philic substitution of an acetoxy group on chiral 1-[2-
(diphenylphosphino)ferrocenyl]ethyl acetate (PPFOAc)
and 1-[1′,2-bis(diphenylphosphino)ferrocenyl]ethyl ace-
tate (BPPFOAc) occurred easily with retention of con-
figuration,4 these acetates were allowed to react with
benzenethiolate anion and phenyl selenide anion in
refluxing ethanol. As a result, the corresponding (S,R)-
sulfides (22 and 23) and (S,R)-selenides (24 and 25)
were produced in 74-99% yield (Scheme 5), the config-
uration at the secondary carbon being believed to be
that shown in the scheme. Attempts to prepare similar
tellurium compounds were unsuccessful probably be-
cause of the air-instability of products having tellurium
at the benzylic position.17
Syn th esis of Ch ir a l Bis(ch a lcogen id es). DIOP
[2,3-O,O′-isopropylidene-1,4-bis(diphenylphosphino)-2,3-
butanediol], prepared by Kagan et al., was the first
effective ligand for transition metal-catalyzed asym-
metric reactions.2a The C2 symmetrical structure in
DIOP and four phenyl groups on the two phosphines
played an important role in enantioselective reactions.
In connection with this compound, we envisaged to
prepare similar compounds having a phenylchalcogeno
moiety in place of the diphenylphosphino moiety and
Syn th esis of Ch ir a l F er r ocen ylp h osp h in es P os-
sessin g a Ch a lcogen o Moiety on th e Sid e Ch a in
of th e F er r ocen e. Recent reports by Togni et al. for
the preparation of chiral ferrocenylphosphines possess-
ing a different type of phosphine on the side chain of
(16) (a) Togni, A.; Breutel, C.; Schnyder, A.; Spindler, F.; Landert,
H.; Tijani, A. J . Am. Chem. Soc. 1994, 116, 4062. (b) Breutel, C.;
Pregosin, P. S.; Salzmann, R.; Togni, A. J . Am. Chem. Soc. 1994, 116,
4067.
(17) (a) Ferreira, J . T. B.; Oliveira, A. R. M.; Comasseto, J . V.
Tetrahedron Lett. 1992, 33, 915. (b) Nishibayashi, Y.; Chiba, T,; Singh,
J . D.; Uemura S.; Fukuzawa, S. J . Organomet. Chem. 1994, 473, 205.
(15) Singh, A. K.; Srivastava, V. J . Coord. Chem. 1992, 27, 237.

Rh- and Ir-Catalyzed Hydrosilylation
Organometallics, Vol. 15, No. 1, 1996 373
Sch em e 6
reaction was carried out at 25 °C, the product yield was
higher in all solvents, but the ee value was always lower
(runs 6 and 7, runs 8 and 9, runs 12 and 13). Either at
-20 or +40 °C the reaction hardly occurred. As to the
silane, diphenylsilane (85% ee, run 13) and R-naphthyl-
phenylsilane (82% ee, run 17) showed similar activities,
followed by dimethylphenylsilane (73% ee, run 18),
phenylsilane (∼0% ee, run 19), and triphenylsilane (no
reaction, run 20) roughly in accordance with the ten-
dency observed in the case of chiral phosphines,22 while
it has been reported that, in the case of DIOP ligand,
the reaction using R-naphthylphenylsilane afforded a
higher selectivity than diphenylsilane.18,23 As to the
rhodium catalyst, the neutral complex [Rh(COD)Cl]2
was more effective than the cationic complex [Rh(COD)2]-
BF4 (runs 13 and 16). Next, the effectiveness of a
variety of chiral dichalcogenide ligands (1-10) was
examined under the above optimum conditions, and
typical results are also shown in Table 1. Although it
has been known that the presence of an hydroxy group
on a side chain of ferrocenylphosphine compounds has
a remarkable effect upon enantioselective hydrogenation
of ketones,22 ligand 7 (run 25) did not act well in our
case. The ligand possessing a morpholinoethyl moiety
5 (run 23), as well as ligands possessing p-tolylsulfinyl
moieties 9 and 10 (runs 26 and 27), were not effective,
while ligands 1 and 3 showed moderate activity (31-
50% ee, runs 21 and 22). These results show that the
presence of a (dimethylamino)ethyl moiety on the ferro-
cene ring is most important for highly enantioselective
hydrosilylations when diferrocenyl dichalcogenides are
employed as chiral ligands.
Similar hydrosilylation of acetophenone was then
carried out in THF at 0 °C using various newly prepared
chiral alkyl or aryl ferrocenyl chalcogenides and chal-
cogeno-group containing ferrocenes (11-28) in place of
diferrocenyl dichalcogenides. The reaction proceeded
smoothly to give chiral 1-phenylethanol using any
ligands except for 28, but unfortunately the enantio-
selectivity was always modest to low. Typical results
are shown in Table 2. Among the chalcogeno ethers
(11-13), the seleno ether 12 gave the best ee as in the
case of dichalcogenide series, but in the series of seleno
ethers (12 and 14-19), no characteristic tendency for
enantioselectivity was observed. Although we antici-
pated high enantioselectivity of the product from the
reaction using chiral ligands 22-28, the result was
disappointing and, especially in the case of 26-28, the
product was nearly the racemate in sharp contrast to
the previously reported DIOP case.18,23
Sch em e 7
succeeded in the preparation of novel (S,S)-bis(sulfide)
(26), bis(selenide) (27) and bis(telluride) (28) (Scheme
6) in very high yields (72-97%) by treatment of (S,S)-
2,3-O,O′-isopropylidene-1,4-bis(tosyloxy)-2,3-butane-
diol with the corresponding phenyl chalcogenide anions.
Rh od iu m -Ca ta lyzed Asym m etr ic Hyd r osilyla -
tion of Keton es Usin g Va r iou s Ch ir a l Ch a lco-
gen id es a s Liga n d s. Rhodium(I)-catalyzed enantio-
selective asymmetric hydrosilylation of ketones devel-
oped by Kagan et al.,18 Brunner et al.,19 and Nishiyama
et al.20 has been an important asymmetric reaction
because of the utility of optically pure alcohols in organic
synthesis.21 Therefore, in the first place, we chose Rh(I)-
catalyzed asymmetric hydrosilylation in order to exam-
ine the effectiveness of newly prepared chiral chalcogeno
compounds, although the possibility existed that the
reaction would not occur because of the formation of a
too stable complex between Rh(I) complex and the
chalcogeno compounds.10
The reaction was generally carried out as follows.
The catalyst was prepared in situ by stirring the
rhodium complex, [Rh(COD)Cl]2 or [Rh(COD)2]BF4, and
a chiral chalcogeno compound in a suitable solvent at
room temperature for 1 h under N2. Ketone and then
arylsilane were added dropwise at 0 or 25 °C, and the
mixture was stirred for an appropriate time at that
temperature and then quenched with methanol and
dilute HCl to afford the corresponding chiral alcohol
(Scheme 7). Chemical yields were determined by GLC,
while the ee value and the configuration were deter-
mined by HPLC using Daicel Chiralcel OJ , OD, OB, and
OF columns. First, we searched for an optimum condi-
tion for hydrosilylation by using acetophenone as the
substrate and the selenide 2 as the chiral ligand. The
yield of chiral 1-phenylethanol and its ee value obtained
under various conditions are summarized in Table 1.
As a result, the optimum condition was found to be the
use of tetrahydrofuran (THF), [Rh(COD)Cl]2, and diphen-
ylsilane at 0 °C with a rhodium/2 ratio of 1. When the
As the ligand 2 was found to be most effective for
enantioselective hydrosilylation of acetophenone, the
reactions of a variety of alkyl aryl ketones with diphen-
ylsilane were then examined in THF at 0 °C using
[Rh(COD)Cl]2-2 as a catalyst. The product yield or the
reaction rate was much affected by the nature of alkyl
and aryl groups of the ketone (Scheme 7, Table 3). As
expected, this decreased as the bulkiness of the alkyl
group increased: Me (31%) > Et (14%) > t-Bu (5%).
Replacement of methyl by trifluoromethyl stopped the
reaction completely. For aryl groups, the introduction
(18) Dumont, W.; Poulin, J . C.; Dang, T.-P.; Kagan, H. B. J . Am.
Chem. Soc. 1973, 95, 8295.
(19) (a) Brunner, H.; Becker, R.; Riepl, G. Organometallics 1984, 3,
1354. (b) Brunner, H.; Oberman, U. Chem. Ber. 1989, 122, 499. (c)
Brunner, H.; Brandl, P. Tetrahedron Asymmetry 1991, 931.
(20) (a) Nishiyama, H.; Kondo, M.; Nakamura, T.; Itoh, K. Organo-
metallics 1991, 10, 500. (b) Nishiyama, H.; Yamaguchi, S.; Kondo, M.;
Nakamura, T.; Itoh, K. J . Org. Chem. 1992, 57, 4306.
(21) The transition metal-catalyzed asymmetric hydrosilylation of
ketones has been well studied. For an example: Brunner, H.; Nish-
iyama, H.; Itoh, K. Catalytic Asymmetric Synthesis; Ojima, I., Ed.;
VCH: New York, 1993; Chapter 6.
(22) (a) Hayashi, T.; Katsumura, A.; Konishi, M.; Kumada, M.
Tetrahedron Lett. 1979, 425. (b) Hayashi, T.; Mise, T.; Kumada, M.
Tetrahedron Lett. 1976, 4531.
(23) Ojima, I.; Kogure, T.; Kumagai, M. J . Org. Chem. 1977, 42,
1671.

374 Organometallics, Vol. 15, No. 1, 1996
Nishibayashi et al.
Ta ble 1. Asym m etr ic Hyd r osilyla tion of Acetop h en on e Ca ta lyzed by Rh (I)-(2-10)a
1-phenylethanol
temp (°C) time (h) GLC yield (%) ee (%)b configc
ratio of
ligand Rh(I)/ligand
run
solvent
catalysts
silane
Ph2SiH2
1
2
3
4
5
6
7
8
9
d
d
[Rh(COD)Cl]2
[Rh(COD)Cl]2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
3
5
6
7
1
1
1
2
0.2
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
25
0
1
26
12
5
12
2
73
60
100
60
64
71
37
100
31
100
43
70
31
45
62
47
65
48
82
0
12
9
21
15
11
8
47
∼0
27
6
∼0
11
85
25
33
9
R
R
S
R
S
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
R-NapPhSiH2
PhMe2SiH
PhSiH3
benzene [Rh(COD)Cl]2
benzene [Rh(COD)Cl]2
benzene [Rh(COD)Cl]2
25
25
25
25
0
25
0
25
25
25
0
0
25
0
0
0
e
f
Et2O
Et2O
DME
DME
CH2Cl2
CH3CN
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
Et2O
THF
THF
THF
THF
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)2]BF4
[Rh(COD)2]BF4
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)2]BF4
[Rh(COD)Cl]2
[Rh(COD)Cl]2
R
R
24
3
26
12
20
48
48
48
48
48
40
72
36
72
72
72
72
72
20
94
190
290
190
190
190
190
R
S
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
R
R
R
R
R
R
R
e
82
73
∼0
0
0
Ph3SiH
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
Ph2SiH2
R-NapPhSiH2
Ph2SiH2
Ph2SiH2
0
0
0
0
46
67
37
50
90
81
36
52
0
31
50
31
12
5
0
26
11
R
R
R
R
R
0
9
25
25
25
25
25
0
10
10
10
10
10
10
R
R
18
0
84
22
8
R
R
e
[Rh(COD)Cl]2
25
a
All the reactions were carried out by using acetophenone (1.0 mmol) and diphenylsilane (1.5 mmol) in the solvent (4 mL) in the
b
presence of [Rh(COD)Cl]2 (2.5 mol %) or [Rh(COD)2]BF4 (5 mol %) and 2-10 (5 mol %) unless otherwise stated. Determined by HPLC
using a Daicel Chiralcel OB column. c By optical rotation. Without solvent. e [Rh(COD)Cl]2, 5 mol %. f [Rh(COD)Cl]2, 0.5 mol %.
d
Ta ble 2. Asym m etr ic Hyd r osilyla tion of
Ta ble 3. Asym m etr ic Hyd r osilyla tion of Alk yl Ar yl
Acetop h en on e Ca ta lyzed by Rh (I)-(11-28)a
Keton es Ca ta lyzed by Rh (I)-2a
(R)-1-phenylethanol
ligand Rh(I)/ligand GLC yield (%) ee (%)b
ketone
alcohol (R)
ratio of
ee (%)b
catalyst
Ar
R
time (h)
GLC yield (%)
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)2]BF4
[Rh(COD)2]BF4
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)2]BF4
[Rh(COD)Cl]2
[Rh(COD)2]BF4
[Rh(COD)2]BF4
[Rh(COD)2]BF4
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
[Rh(COD)Cl]2
11
12
12
12
12
13
14
15
16
17
18
19
20
21
22
23
23
24
25
25
26
27
28
0.5
0.5
1
51
26
41
77
62
30
73
81
36
25
51
39
52
44
65
53
73
50
73
53
35
83
0
16
40
11
∼0
18
18
8
16
12
35
∼0
36
33
40
31
13
27
32
24
20
5
Ph
Ph
Ph
Ph
Ph
Me
Et
CH2Cl
CO2Me
t-Bu
24
70
120
25
240
240
72
31
14
85
31
5
85
58
88c
60
1c
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1
85
indanone
5
42
p-NO2C6H4
p-ClC6H4
2-thienyl
Me
Me
Me
45
41
100
76d
74c
78
72
96
a
All the reactions were carried out using alkyl aryl ketones (1.0
mmol) and diphenylsilane (1.5 mmol) in THF (4 mL) at 0 °C in
b
the presence of [Rh(COD)Cl]2 (2.5 mol %) and 2 (5 mol %). See a
footnote of Table 1. c The absolute configuration of the product is
1
d
1c
1
S. The absolute configuration was not determined.
1c
1c
1c
1
as naphthyl inhibited the reaction completely. Reason-
ably high ee values were obtained in many cases, and
the highest ee (88% ee) was obtained from R-chloro-
acetophenone. It is worth noting that the ee value of
the product from the R-keto ester was lower than that
from acetophenone in this case, as it has been reported
that, in similar reactions using chiral phosphine ligands,
the result was completely reversed due to secondary
coordination of the carbonyl oxygen of the ester to
rhodium giving good enantioselective surroundings.
Hydrosilylation using 10 in place of 2 as a ligand was
nearly unsuccessful, and only the R-keto ester afforded
the expected compound in 46% yield (26% ee) by
reaction at 0 °C for 120 h; almost no reaction occurred
1
1
1
∼0
a
All the reactions were carried out by using acetophenone (1.0
mmol) and diphenylsilane (1.5 mmol) in THF (4 mL) at 0 °C for
20 h in the presence of Rh(I) complex (0.5 mol %) and ligand (1.0
b
or 2.0 mol %) unless otherwise stated. See footnote a of Table 1.
c Rh(I) (1.0 mol %) and ligand (1.0 mol %) were used.
of an electron-withdrawing group, such as NO2 and Cl,
or the use of thienyl group increased the product yield,
while the introduction of an electron-releasing group
such as p-Me or p-MeO or the use of a bulky group such

Rh- and Ir-Catalyzed Hydrosilylation
Organometallics, Vol. 15, No. 1, 1996 375
Ta ble 4. Asym m etr ic Hyd r osilyla tion of
Sch em e 8
Acetop h en on e Ca ta lyzed by Ir (I)-(1-3 or 10)a
reacn condition
1-phenylethanol
ligand temp (°C) time (h) GLC yield (%) ee (%)b configb
1
1
2
2
2
2
3
3
10
15
0
40
15
0
-20
15
0
20
144
4
15
24
24
20
144
120
82
43
100
100
55
40
90
81
98
15
13
∼0
23
18
∼0
∼0
22
11
R
R
S
S
R
R
25
Ta ble 5. Asym m etr ic Hyd r osilyla tion of Im in es
Ca ta lyzed by Rh (I)-2a
a
All the reactions were carried out by using acetophenone (1.0
mmol) and diphenylsilane (1.5 mmol) in THF (4 mL) in the
presence of [Ir(COD)Cl]2 (2.5 mol %) and 1-3 or 10 (5 mol %).
amine
b
temp (°C) time (h) yield (%)b ee (%)c
See footnotes of Table 1.
imine R
solvent
Ph
Ph
Ph
Ph
Ph
PhCH2
PhCH2
benzene
Et2O
Et2O
THF
THF
Et2O
THF
25
25
0
25
0
24
24
140
24
140
45
45
54
27
28
28
37
52
47
∼0
∼0
53
0
18
11
7
with methyl 2-thienyl ketone, R-chloroacetophenone,
p-nitroacetophenone, and p-chloroacetophenone.
Ir id iu m -Ca ta lyzed Asym m etr ic Hyd r osilyla tion
of Acetoph en on e Usin g Ch ir al Difer r ocen yl Dich al-
cogen id es a s Liga n d s. Compared to rhodium-cata-
lyzed asymmetric reactions, the study of iridium-
catalyzed ones is still limited, and highly enantioselective
results were obtained in only several cases such as
transfer hydrogenation24 and hydrogenation.25 We ap-
plied the previously described Rh(I)-catalyzed hydro-
silylation system to an iridium(I) complex using aceto-
phenone as a substrate and diferrocenyl dichalcogenides
(1-3 and 10) as chiral ligands. The results are shown
in Table 4. Hydrosilylation proceeded smoothly to give
1-phenylethanol in good yield, but the enantioselectivity
was generally low. It is noteworthy that 1-phenyletha-
nol of the opposite configuration (S) was obtained when
the diselenide 2 was used. Although the formation of
1-phenylethanol of opposite configuration has been
observed between the Rh(I)- and Ir(I)-complex-catalyzed
hydrosilylations of acetophenone using chiral amino-
phosphines as ligands,26 it is difficult to explain in our
system why the configuration of the product using 1 and
3 was different from that using 2 in spite of a very
similar structure of 1-3.
Rh od iu m -Ca ta lyzed Asym m etr ic Hyd r osilyla -
tion of Im in es Usin g 2 a s a Ch ir a l Liga n d . Asym-
metric hydrosilylation of imines affords synthetically
useful chiral sec-amines, but the study on this subject
is still quite limited and the observed enantioselectivity
thus far is low.27 We applied our Rh(I)-2 catalytic
system to two imines in various solvents (Scheme 8,
Table 5). In all cases, the reaction proceeded smoothly
and the conversion of imines to the hydrosilylated
products was almost 100%, but the isolated yield of the
corresponding amines after acid hydrolysis in a pure
form was low because of difficulty in their separation
from 2. A good result was obtained from N-phenyl-1-
0
0
a
All the reactions were carried out using imines (1.0 mmol) and
diphenylsilane (1.5 mmol) in solvent (4 mL) at 0 °C in the presence
b
of [Rh(COD)Cl]2 (2.5 mol %) and 2 (5 mol %). Isolated yield in a
pure form. c The absolute configuration of the product was not
determined.
Sch em e 9
phenylpropanimine (29) (up to 53% ee), but the reaction
with N-benzyl analogue (30) gave low selectivity (up to
11% ee).
Rh od iu m -Ca ta lyzed Asym m etr ic Hyd r ogen a tion
of a n En a m id e Usin g 2 a s a Ch ir a l Liga n d . In order
to find another utility of 2 as a chiral ligand, asymmetric
hydrogenation of an enamide, R-acetamidocinnamic acid
(31), was carried out under 1 atm hydrogen in the
presence of a Rh(I) complex (Scheme 9), as highly
enantioselective hydrogenation of the enamide has been
reported in many cases.3b In the presence of 5 mol %
[Rh(COD)Cl]2-2 complex, 31 was hydrogenated in dry
ethanol at room temperature to give the hydrogenated
product in 49% yield (50 h) and its ee value was 69% as
determined by the optical rotation. The result was not
satisfactory, but it was shown that 2 could also act as a
chiral ligand for asymmetric hydrogenation.
P r ep a r a tion of a Com p lex betw een Ca tion ic
Rh od iu m (I) Com p ou n d a n d 2 a n d a P la u sible
Sch em e for Hyd r osilyla tion . In order to study the
reaction scheme of this catalytic hydrosilylation, we
have tried to confirm the in situ formation of the
complex between [Rh(COD)Cl]2 and 2 or to isolate it, if
possible. However, 1H-NMR determination of the mix-
ture of the two compounds in THF-d8 under argon did
not give any information on complex formation, and
attempts to isolate it after reaction of the two com-
pounds in THF at room temperature for 20 h resulted
in a complete recovery of 2. The latter fact also suggests
that oxidative addition of 2 to Rh(I) does not occur under
our conditions in contrast to the so far known facile
oxidative addition of diphenyl diselenide or diphenyl
disulfide to low-valent Rh compounds.28
(24) (a) Zassinovich, G.; Bettella, R.; Mestroni, G.; Bresciani-Pahor,
N.; Geremia, S.; Randaccio, L. J . Organomet. Chem. 1989, 370, 187.
(b) Mu¨ller, D.; Umbricht, G.; Weber, B.; Pfaltz, A. Helv. Chim. Acta
1991, 74, 232.
(25) Mashima, K.; Akutagawa, T.; Zhang, X.; Takaya, H.; Taketomi,
T.; Kumobayashi, H.; Akutagawa, S. J . Organomet. Chem. 1992, 428,
213.
(26) Kinting, A.; Kreuzfeld, H. J .; Abicht, H. P. J . Organomet. Chem.
1989, 370, 343.
(27) (a) Langlois, N.; Dang, T. P.; Kagan, H. B. Tetrahedron Lett.
1973, 4865. (b) Kagan, H. B.; Langlois, N.; Dang, T. P. J . Organomet.
Chem. 1975, 90, 353. (c) Becker, R.; Brunner, H.; Mahboobi, S.;
Wiegrebe, W. Angew. Chem., Int. Ed. Engl. 1985, 24, 995.

376 Organometallics, Vol. 15, No. 1, 1996
Nishibayashi et al.
Sch em e 10
Sch em e 11
On the other hand, we succeeded in isolation of the
complex between a cationic rhodium compound ([Rh-
(COD)2]BF4) and 2 by mixing them in THF at 25 °C.
The new complex, isolated in 53% yield, was insoluble
in CHCl3 and THF but soluble in acetone. Proton-NMR
analysis in acetone-d6 did not show any peaks due to
COD and showed all downfield shifted protons of the
complex compared with those of 2 itself, which was
especially prominent for the singlet methyl resonance
of the -NMe2 group. Although a single crystal of the
complex was not available for X-ray structural deter-
mination, we presumed it to be a 1:1 complex between
Rh and diselenide where two Se and two N are coordi-
Si-H bond of arylsilane occurs. Subsequent coordina-
tion of a carbonyl group to the rhodium, formation of a
C-Rh bond, and reductive elimination from Rh furnish
the hydrosilylated compound. The key step for stereo-
selection seems to be the coordination of a carbonyl
group to the rhodium of Rh(III)-2 complex B, which
may have a more suitable rigid structure for stereo-
selection than any complexes having other newly pre-
pared dichalcogenides and monochalcogenides as chiral
ligands.
In conclusion, many novel chiral diferrocenyl dichal-
cogenides and chalcogeno-group containing ferrocenes
have been prepared. These compounds acted as chiral
ligands for Rh(I)- and Ir(I)-catalyzed asymmetric hy-
drosilylation of ketones and imines and asymmetric
hydrogenation of an enamide to give the corresponding
products with moderate to good ee, with [R,S;R,S]-bis-
[2-[1-(dimethylamino)ethyl]ferrocenyl] diselenide (2) be-
ing the most effective ligand.
1
nated to Rh from the results of the H-NMR analysis
together with CH analytical data. It may also be
possible that the complex was formed by oxidative
addition of the Se-Se bond to a Rh(I) to afford a Rh(III)
complex such as [(Fc*Se)Rh(SeFc*)]BF4, which would
1
give the same CH analysis and similar H-NMR data.
Therefore, we examined the utility of this new complex
for asymmetric hydrosilylation. If it were a Rh(III)
complex, the possibility for oxidative addition of an
Si-H bond to it should be quite low and no reaction is
expected to occur. Hydrosilylation of acetophenone in
the presence of 1 mol % of this complex under the
previously described conditions, however, proceeded
smoothly to give (R)-1-phenylethanol in 60% isolated
yield with 60% ee (Scheme 10). This fact shows that
the complex may have the structure shown in 32 where
2 coordinates to Rh(I) as a tetradentate ligand.
By considering these results, we propose Scheme 11
as a catalytic cycle for the Rh(I) complex catalyzed
hydrosilylation of ketones using 2 as a chiral ligand.
Under the catalytic conditions, COD of the Rh(I) com-
plex might be hydrosilylated and removed from the
rhodium to generate the catalytically active species (A),
where 2 coordinates to the rhodium giving a tetracoor-
dinated Rh(I) complex, on which oxidative addition of
Exp er im en ta l Section
Gen er a l Meth od s. 1H and 13C NMR spectra were recorded
on a J EOL GSX-270 (270 MHz) spectrometer as solutions in
CDCl3. Chemical shifts are reported in δ units downfield from
the internal reference Me4Si. The coupling constants (J ) are
in hertz (Hz). Melting points were determined on a Yanaco
MP-S3 micro melting point apparatus and uncorrected. Opti-
cal rotations were measured on a J ASCO DIP-360. GLC
analyses were performed on a Hitachi 163 instrument (1 m ×
3 mm stainless steel column packed with 20% EGSS on
Shimalite) and a Shimadzu GC-14A instrument (25 m HiCap-
CBP-10-S25 capillary column) with flame-ionization detectors
and N2 as carrier gas. Column chromatography on Al2O3 was
performed with ICN Alumina N, Akt. I (hexane and hexane/
ethyl acetate as eluents). Column chromatography on SiO2
was performed with Wakogel C-300 (hexane and hexane/ethyl
acetate as eluents). Elemental analyses were performed at
(28) (a) Collman, J . P.; Rothrock, R. K.; Sen, J . P.; Tullius, T. D.;
Hodgson, K. O. Inorg. Chem. 1976, 15, 2947. (b) Collman, J . P.;
Rothrock, R. K.; Stark, R. A. Inorg. Chem. 1977, 16, 437.

Rh- and Ir-Catalyzed Hydrosilylation
Organometallics, Vol. 15, No. 1, 1996 377
Ta ble 6. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 8
the Microanalytical Center of Kyoto University. All solvents
were distilled from CaH2 or LiAlH4 and stored over 4 Å
molecular sieves under nitrogen. (R)-(+)-N,N-Dimethyl-(1-
ferrocenyl)ethylamine and the (S)-(-)-N,N-dimethyl-(1-ferro-
cenylethyl)amine were prepared easily by the reported method
on a large scale.29 (R,S)-Diferrocenyl diselenide (2), (R,S)-
diferrocenyl disulfide (1), and (R,S)-diferrocenyl ditelluride (3)
were prepared by the reported method, respectively.9 (R)-
Ferrocenyl p-tolyl sulfoxide was prepared by the reported
method in a large scale.14 (S,R)-BPPFOAc was a commercial
reagent, while (S,R)-PPFOAc was prepared by the reported
method from (S,R)-N,N-dimethyl-[1-[2-(diphenylphosphino)-
ferrocenyl]ethyl]amine and acetic anhydride.4 (2S,3S)-(-)-1,4-
Di-O-tosyl-2,3-O,O′-isopropylidene-L-threitol (DIOTs) was a
commercial reagent.
P r ep a r a tion of Diselen id e 5 (Sch em e 1). To a solution
of 2 (670 mg, 1.0 mmol) in acetonitrile (6 mL) was added 10
mL of methyl iodide, and the mixture was stirred at room
temperature for 4 h during which time the solution turned
from heterogeneous to homogeneous. The solvent was then
evaporated completely to leave a viscous oil of the ammonium
salt of 4. To this compound, acetonitrile (6 mL) and pyrrolidine
(5.0 g, 70 mmol) were added, and the mixture was stirred at
room temperature for 48 h to give a yellow heterogeneous
mixture. After the solvent was removed under reduced
pressure, the residue was treated with brine (100 mL) and then
extracted with CH2Cl2 (50 mL × 3). The extract was dried
over MgSO4 and evaporated to leave an orange solid of (R,S)-5
which was purified by column chromatography on alumina
with CH2Cl2 as an eluent: yield 260 mg, 0.35 mmol (35% based
on 2); mp 63-65 °C. 1H-NMR δ 4.04-4.45 (6H, m), 4.10 (10H,
s), 3.70 (2H, q, J ) 6.48 Hz), 2.64 (4H, m), 2.50 (4H, m), 1.58-
1.76 (8H, m), 1.53 (6H, d, J ) 6.48 Hz); 13C-NMR δ 75.4 (d),
73.0 (s), 70.0 (s), 69.9 (d), 69.5 (d), 68.3 (d), 55.0 (d), 51.0 (t),
23.3 (t), 20.4 (q). Anal. Calcd for C32H40N2Fe2Se2: C, 53.21;
H, 5.58; N, 3.88. Found: C, 53.29; H, 5.55; N, 3.51.
P r ep a r a tion of Diselen id e 6. Under nitrogen, a mixture
of 2 (677 mg, 1.01 mmol) and acetic anhydride (2.0 mL) was
stirred at room temperature for 10 h. The mixture was treated
with saturated Na2CO3 (100 mL) and then extracted with
CH2Cl2 (50 mL × 3). The extract was dried over MgSO4 and
evaporated to leave a black oil of a mixture of 6 and N,N-
dimethylacetamide. After recrystallization from ethanol, the
(R,S)-diferrocenyl diselenide (6) (mp 155-156 °C) was isolated
as a red solid in 62% yield (440 mg, 0.63 mmol): 1H-NMR δ
6.02 (2H, q, J ) 6.48 Hz), 4.49 (2H, t, J ) 1.89 Hz), 4.37 (4H,
t, J ) 1.89 Hz), 4.09 (10H, s), 2.11 (6H, s), 1.63 (6H, d, J )
6.48 Hz); 13C-NMR δ 170.1 (s), 89.5 (s), 76.8 (d), 74.7 (s), 70.1
(d), 70.0 (d), 68.8 (d), 68.6 (d), 21.7 (q), 18.5 (q). Anal. Calcd
for C28H30O4Fe2Se2: C, 48.03; H, 4.32. Found: C, 48.22; H,
4.28.
P r ep a r a tion of Diselen id e 7. A mixture of 6 (677 mg,
1.01 mmol) and silica gel (1.0 g) in CH2Cl2 (10 mL) was stirred
at room temperature for 10 h. Silica gel was removed by a
short alumina column, and evaporation of solvent from the
eluent afforded an almost pure 7. After recrystallization from
n-hexane and CH2Cl2, the (R,S)-diferrocenyl diselenide (7) (mp
224-225 °C (dec)) was isolated as a yellow solid in 61% yield
(373 mg, 0.61 mmol): 1H-NMR δ 4.46 (4H, m), 4.36 (2H, t, J
) 2.43 Hz), 4.10 (10H, s), 4.10 (2H, q, J ) 6.75 Hz), 1.55 (2H,
br), 1.48 (6H, d, J ) 6.75 Hz); 13C-NMR δ 94.9 (s), 74.4 (s),
74.0 (d), 70.1 (d), 70.0 (d), 68.8 (d), 66.4 (d), 24.0 (q). Anal.
Calcd for C24H26O2Fe2Se2: C, 46.79; H, 4.25. Found: C, 46.80;
H, 3.88.
Bond Distances
Se(1)-Se(2)
Se(1)-C(13)
O(1)-C(11)
2.354(1)
1.904(10)
1.46(1)
Se(2)-C(1)
O(1)-C(23)
1.869(8)
1.44(1)
Bond Angles
Se(1)-Se(2)-C(1)
Se(2)-Se(1)-C(13)
101.2(3) O(1)-C(23)-C(14) 108.0(7)
99.3(3) C(11)-O(1)-C(23) 117.2(7)
Ta ble 7. Atom ic Coor d in a tes for 8
atom
x
y
z
Beq (Å2)
Se(1)
Se(2)
Fe(1)
Fe(2)
O(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
0.7542(1)
0.9900(1)
0.7757(2)
1.1941(2)
1.0674(9)
0.890(1)
0.928(1)
1.026(1)
1.048(1)
0.962(1)
0.662(2)
0.579(2)
0.501(1)
0.533(2)
0.640(2)
0.893(1)
0.807(1)
0.993(1)
1.094(1)
1.077(1)
0.968(1)
0.915(1)
1.335(2)
1.446(1)
1.456(1)
1.358(2)
1.283(1)
1.180(1)
1.368(1)
0.1658
-0.15657(6)
-0.20017(6)
-0.09504(8)
-0.38636(8)
-0.3266(4)
-0.1329(6)
-0.1921(6)
-0.1464(7)
-0.0591(7)
-0.0503(6)
-0.0077(8)
-0.0090(8)
-0.0865(9)
-0.1395(9)
-0.088(1)
3.10(2)
3.35(2)
2.68(3)
2.59(3)
2.9(1)
2.8(2)
2.5(2)
3.4(2)
4.1(2)
3.6(2)
5.3(3)
5.2(3)
4.9(3)
6.3(4)
5.9(4)
2.8(2)
3.5(2)
2.5(2)
2.6(2)
3.0(2)
3.3(2)
2.7(2)
5.2(3)
5.7(4)
6.1(4)
5.4(3)
4.5(3)
2.8(2)
4.3(3)
0.0164(1)
0.5189(2)
-0.0179(2)
0.4330(7)
0.336(1)
0.4450(9)
0.557(1)
0.510(1)
0.374(1)
0.647(2)
0.514(2)
0.488(2)
0.605(2)
0.708(1)
0.439(1)
0.577(1)
0.0613(10)
0.178(1)
0.159(1)
0.029(1)
-0.026(1)
-0.163(2)
-0.042(2)
-0.036(2)
-0.151(2)
-0.228(1)
0.306(1)
0.344(1)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
-0.2883(6)
-0.3243(6)
-0.3152(5)
-0.3530(5)
-0.4440(6)
-0.4608(6)
-0.3827(6)
-0.4543(9)
-0.432(1)
-0.340(1)
-0.3140(9)
-0.3825(9)
-0.3088(6)
-0.3394(8)
(λ ) 0.710 69 Å) and a 12 kW rotating anode generator.
Crystal data for 8 are as follows: monoclinic, space group P21
(No. 4); a ) 7.363(3), b ) 9.326(2), c ) 15.826(2) Å; V )
1085.5(4) Å3; Z ) 2; Dcalcd ) 1.83 g cm-3; µ(Mo KR) ) 47.02
cm-1; total of 3589 reflections within 2θ ) 60.0°. The final R
value was 0.047 (Rw ) 0.055). The structure was solved by
direct methods (SHELXS86). All non-hydrogen atoms were
refined anisotropically. Hydrogen atom positions were geo-
metrically calculated or taken from a difference Fourier map.
Selected bond distances and angles for 8 are shown in Table
6. The final non-H atomic parameters are summarized in
Table 7.
P r ep a r a tion of Diselen id e 10 (Sch em e 2). After lithia-
tion of (R)-ferrocenyl p-tolyl sulfoxide (1.23 g, 3.8 mmol) in
tetrahydrofuran (THF) (40 mL) with lithium diisopropylamide
(4.2 mmol) in dry heptane/THF/ethylbenzene (2.1 mL) at -78
°C under N2, selenium powder (0.34 g, 4.3 mmol) was added
portionwise and the resulting mixture was stirred at -78 °C
for 10 min and then at room temperature for 1 h. The mixture
was poured into water (10 mL), and then air was bubbled
through the solution at room temperature for 9 h. An almost
pure sample of (R,S)-bis[2-(p-tolylsulfinyl)ferrocenyl] diselenide
[(Fs*Se)2] (10) was isolated in 20% yield (0.31 g, 0.39 mmol)
by column chromatography on SiO2 with n-hexane and ethyl
acetate as eluents. Recrystallization from n-hexane and
CH2Cl2 afforded a pure 10 as an orange solid (mp 189-191
°C): 1H-NMR δ 7.80 (4H, d, J ) 7.97 Hz), 7.39 (4H, d, J )
7.97 Hz), 4.51 (2H, m), 4.37 (2H, m), 4.15 (10H, s), 4.06 (2H,
m), 2.47 (6H, s); 13C-NMR δ 141.4 (s), 140.4 (s), 129.5 (d), 125.6
(d), 97.9 (s), 78.6 (d), 75.2 (s), 71.3 (d), 71.0 (d), 70.4 (d), 21.5
(q). Anal. Calcd for C34H30O2Fe2S2Se2: C, 50.77; H, 3.76.
Found: C, 50.44; H, 3.79. [R]25D: +160 (c 0.12, CHCl3).
X-r a y Str u ctu r a l Deter m in a tion of Diselen id e 8 (F ig-
u r e 1). A single crystal of (R,S)-8 was obtained from 7
recrystallized carefully and slowly from CH2Cl2 at room
temperature. Data for 8 (an orange crystal; mp >250 °C) of
formula C24H24OFe2Se2 were collected on a Rigaku AFC7R
diffractometer with graphite-monochromated Mo KR radiation
(29) Gokel, G.; Ugi, I. J . Chem. Educ. 1972, 49, 82.

378 Organometallics, Vol. 15, No. 1, 1996
Nishibayashi et al.
(R,R)-Difer r ocen yl Disu lfid e (9). Similarly, (R,R)-bis[2-
(p-tolylsulfinyl)ferrocenyl] disulfide [(Fs*S)2] (9) (mp >250 °C)
was prepared as a yellow solid in 23% isolated yield from (R)-
ferrocenyl p-tolyl sulfoxide: 1H-NMR δ 7.81 (4H, d, J ) 7.97
Hz), 7.40 (4H, d, J ) 7.97 Hz), 4.46 (2H, m), 4.38 (2H, m),
4.13 (10H, s), 4.10 (2H, m), 2.47 (6H, s); 13C-NMR δ 141.4 (s),
140.4 (s), 129.5 (d), 125.6 (d), 97.4 (s), 84.0 (s), 77.2 (d), 71.2
(d), 70.8 (d), 70.4 (d), 21.5 (q). Anal. Calcd for C34H30O2-
J ) 7.02 Hz), 0.96 (3H, t, J ) 7.29 Hz); 13C-NMR δ 93.6 (s),
74.7 (d), 73.1 (s), 69.9 (d), 67.5 (d), 56.9 (d), 40.3 (q), 31.5 (t),
23.6 (t), 14.6 (q), 12.7 (q). Anal. Calcd for C17H25NFeSe: C,
53.99; H, 6.66; N, 3.70. Found: C, 54.20; H, 6.71; N, 3.62.
Spectroscopic and analytical data and isolated yield of other
selenides (R,S)-16-21 are as follows.
16: an orange oil; 1H-NMR δ 4.32 (1H, t, J ) 2.16 Hz), 4.18
(2H, m), 4.09 (5H, s), 3.92 (1H, q, J ) 7.02 Hz), 2.74-2.83 (1H,
m), 2.54-2.64 (1H, m), 2.11 (6H, s), 1.64 (2H, m), 1.36 (3H, d,
J ) 7.02 Hz), 1.35 (2H, m), 0.88 (3H, t, J ) 7.29 Hz); 13C-
NMR δ 93.7 (s), 74.7 (d), 73.1 (s), 69.9 (d), 67.5 (d), 56.9 (d),
40.3 (q), 32.5 (t), 29.0 (t), 23.0 (t), 13.6 (q), 12.6 (q). Anal. Calcd
for C18H27NFeSe: C, 55.12; H, 6.94; N, 3.06. Found: C, 55.24;
H, 7.13; N, 3.41. Yield: 82%.
Fe2S4: C, 57.47; H, 4.26. Found: C, 57.17; H, 4.41. [R]25
+180 (c 0.12, CHCl3).
:
D
(R,S)-Ferrocenyl phenyl sulfide (11) and (R,S)-ferrocenyl
phenyl selenide (12) are known compounds which were
prepared by the reported method.30
(R,S)-F er r ocen yl P h en yl Tellu r id e (13) (Sch em e 3).
After lithiation of commercial (R)-(+)-N,N-dimethyl-(1-ferro-
cenylethyl)amine (526 mg, 2.05 mmol) with sec-BuLi (cyclo-
hexane solution, 2.24 mmol) in dry diethyl ether (10 mL) at 0
°C under N2, diphenyl ditelluride (836 mg, 2.05 mmol) was
added portionwise and the resulting mixture was stirred at 0
°C for 2 h and then at room temperature for 4 h. The mixture
was treated with saturated Na2CO3 (100 mL) and then
extracted with CH2Cl2 (50 mL × 3). The extract was dried
over MgSO4 and evaporated to leave a black oil of crude (R,S)-
13 which was purified by column chromatography on active
alumina with n-hexane and ethyl acetate as eluents giving a
black oil (483 mg, 1.05 mmol) in 51% yield: 1H-NMR δ 4.25
(1H, m), 4.21 (1H, t, J ) 2.43 Hz), 4.12 (1H, m), 4.01 (5H, s),
3.98 (1H, q, J ) 7.02 Hz), 2.04 (6H, s), 1.29 (3H, d, J ) 7.02
Hz); 13C-NMR δ 138.2 (d), 128.7 (d), 127.3 (d), 117.7 (s), 93.8
(s), 75.0 (s), 70.2 (s), 68.7 (d), 67.6 (d), 59.0 (d), 39.5 (q), 11.0
(q). Anal. Calcd for C20H23NFeTe: C, 52.12; H, 5.03; N, 3.04.
Found: C, 52.49; H, 5.18; N, 2.91.
(R,S)-F er r ocen yl 2,4,6-Tr iisop r op ylp h en yl Selen id e
(14). Similarly, the selenide 14 was prepared from (R)-(+)-
N,N-dimethyl(1-ferrocenylethyl)amine and (2,4,6-triisopropyl-
phenyl)selenenyl bromide as a red oil:31 1H-NMR δ 6.98 (2H,
s), 4.15 (1H, m), 4.10 (5H, s), 4.03-4.08 (2H, m), 3.96 (2H,
quint, J ) 6.75 Hz), 3.64 (1H, q, J ) 6.48 Hz), 2.87 (1H, quint,
J ) 6.75 Hz), 2.02 (6H, s), 1.51 (3H, d, J ) 6.48 Hz), 1.14-
1.25 (18H, m); 13C-NMR δ 152.7 (s), 149.5 (s), 128.5 (s), 121.6
(d), 77.2 (s), 71.8 (d), 70.3 (d), 66.6 (d), 57.4 (d), 41.3 (q), 34.2
(d), 34.0 (d), 24.6 (q), 24.4 (q), 24.0 (q), 16.7 (q). Anal. Calcd
for C29H41NFeSe: C, 64.69; H, 7.68 N, 2.60. Found: C, 64.65;
H, 7.65; N, 2.47. Yield: 34%.
17: a red oil; 1H-NMR δ 5.08-5.98 (1H, m), 4.86-4.90 (2H,
m), 4.32 (1H, t, J ) 2.16 Hz), 4.20 (2H, m), 4.09 (5H, s), 3.96
(1H, q, J ) 7.02 Hz), 3.47-3.52 (1H, m), 3.27-3.29 (1H, m),
2.12 (6H, s), 1.34 (3H, d, J ) 7.02 Hz); 13C-NMR δ 135.6 (d),
115.9 (t), 94.2 (s), 75.4 (d), 72.4 (s), 69.8 (d), 69.6 (d), 67.7 (d),
56.9 (d), 40.1 (q), 31.8 (t), 11.5 (q). Anal. Calcd for C17H23
-
NFeSe: C, 54.28; H, 6.16; N, 3.72. Found: C, 54.58; H, 6.26;
N, 3.37. Yield: 47%.
18: a red oil; 1H-NMR δ 4.32 (1H, t, J ) 2.16 Hz), 4.20 (2H,
m), 4.09 (5H, s), 3.96 (1H, q, J ) 7.02 Hz), 3.15 (1H, m), 2.12
(6H, s), 1.2-2.0 (10H, m), 1.36 (3H, d, J ) 7.02 Hz); 13C-NMR
δ 76.1 (d), 71.8 (s), 70.0 (d), 69.8 (s), 68.0 (d), 67.8 (d), 57.2 (d),
43.6 (d), 40.1 (q), 34.8 (t), 33.7 (t), 25.9 (t), 12.8 (q). Anal. Calcd
for C20H29NFeSe: C, 57.43; H, 6.99; N, 3.35. Found: C, 57.18;
H, 6.64; N, 3.38. Yield: 38%.
19: a red oil; 1H-NMR δ 4.32 (1H, t, J ) 2.16 Hz), 4.20 (2H,
m), 4.09 (5H, s), 3.93 (1H, q, J ) 7.02 Hz), 2.76 (2H, m), 2.12
(6H, s), 1.38 (3H, d, J ) 7.02 Hz), 1.01 (9H, s); 13C-NMR δ
76.5 (s), 74.4 (d), 69.9 (d), 68.2 (s), 67.3 (d), 56.8 (d), 47.5 (s),
46.1 (t), 40.4 (q), 29.6 (q), 12.8 (q). Anal. Calcd for C19H29
-
NFeSe: C, 56.17; H, 7.20; N, 3.45. Found: C, 56.02; H, 7.15;
N, 3.70. Yield: 43%.
20: [R,S;R,S], an orange oil; 1H-NMR δ 4.32 (2H, t, J )
2.16 Hz), 4.18 (4H, m), 4.09 (10H, s), 3.91 (2H, q, J ) 7.02
Hz), 2.82-2.89 (2H, m), 2.57-2.67 (2H, m), 2.10 (12H, s), 1.90
(2H, t, J ) 7.56 Hz), 1.35 (6H, d, J ) 7.02 Hz); 13C-NMR δ
94.2 (s), 77.5 (d), 75.3 (d), 72.9 (s), 70.2 (d), 67.8 (d), 57.2 (d),
40.5 (q), 31.0 (t), 29.2 (t), 12.3 (q). Anal. Calcd for C31H42N2-
Fe2Se2: C, 52.27; H, 5.94; N, 3.93. Found: C, 52.52; H, 6.13;
N, 3.55. Yield: 55%.
P r ep a r a tion of Ch ir a l Alk yl F er r ocen yl Selen id es
(15-21)(Sch em e 4). A typical experimental procedure for the
preparation of these selenides is as follows. In a two-necked
50 mL round bottom flask containing a magnetic stirring bar
were placed (R,S)-(Fc*Se)2 (2) (107 mg, 0.32 mmol) and NaBH4
(25 mg, 0.65 mmol) under nitrogen. Dry ethanol (5 mL) was
added to the flask at 0 °C, and the mixture became homoge-
neous after stirring for 0.5 h at room temperature. An ethanol
(1 mL) solution of n-propyl bromide (60 mg, 0.49 mmol) was
then added to the resulting solution, and the mixture was
stirred at the reflux temperature (bath temperature 100 °C)
for 5 h. The mixture was treated with brine (100 mL) and
then extracted with CH2Cl2 (50 mL × 3). The extract was
dried over MgSO4 and evaporated to leave a yellow solid of
(R,S)-2-[1-(dimethylamino)ethyl]ferrocenyl propyl selenide (15),
which was purified by column chromatography on alumina
with hexane/ethyl acetate (9/1) as an eluent to give pure 15
as an orange oil: 84 mg, 0.22 mmol (69% yield based on 2);
1H-NMR δ 4.32 (1H, t, J ) 2.16 Hz), 4.18 (2H, m), 4.09 (5H,
s), 3.92 (1H, q, J ) 7.02 Hz), 2.74-2.83 (1H, m), 2.54-2.64
(1H, m), 2.11 (6H, s), 1.64 (2H, six, J ) 7.29 Hz), 1.37 (3H, d,
21: [R,S;R,S], an orange oil; 1H-NMR δ 4.32 (2H, t, J )
2.16 Hz), 4.18 (4H, m), 4.08 (10H, s), 3.91 (2H, q, J ) 7.02
Hz), 2.73-2.80 (2H, m), 2.55-2.63 (2H, m), 2.10 (12H, s), 1.63
(2H, m), 1.40 (4H, m), 1.36 (6H, d, J ) 7.02 Hz); 13C-NMR δ
94.0 (s), 77.5 (d), 75.1 (d), 73.1 (s), 70.2 (d), 67.8 (d), 57.2 (d),
40.6 (q), 30.4 (t), 30.2 (t), 29.3 (t), 12.6 (q). Anal. Calcd for
C
33H46N2Fe2Se2: C, 53.54; H, 6.26; N, 3.78. Found: C, 53.15;
H, 6.23; N, 3.44. Yield: 55%.
P r ep a r a tion of Ch ir a l F er r ocen ylp h osp h in es P ossess-
in g a Ch a lcogen o Moiety on th e Sid e Ch a in of F er r ocen e
(22-25) (Sch em e 5). A typical experimental procedure for
the preparation of (S,R)-22 is as follows. In a two-necked 50
mL round bottom flask containing a magnetic stirring bar were
placed diphenyl disulfide (51.2 mg, 0.23 mmol) and NaBH4 (53
mg, 1.40 mmol) under nitrogen. Ethanol (4 mL) was added
to the flask at 0 °C, and the mixture became homogeneous
after stirring for 0.5 h at room temperature. An ethanol (2
mL) solution of (S,R)-PPFOAc (200 mg, 0.45 mmol) was then
added to the resulting solution, and the mixture was stirred
at the reflux temperature (bath temperature 100 °C) for 4 h.
The mixture was treated with brine (100 mL) and then
extracted with CH2Cl2 (50 mL × 3). The extract was dried
over MgSO4 and evaporated to leave a yellow solid of (S,R)-
22, which was recrystallized from EtOH (mp 76-78 °C): 230
mg, 0.45 mmol (100% yield based on PPFOAc); 1H-NMR δ
7.61-7.68 (2H, m), 7.37-7.41 (3H, m), 7.18-7.30 (10H, m),
4.53 (1H, m), 4.36 (2H, m), 4.02 (1H, m), 3.92 (5H, s), 1.69
(30) (a) Honeychuck, R. V.; Okoroafor, M. O.; Shen, L. H.; Brubaker,
C. H., J r. Organometallics 1986, 5, 482. (b) Okoroafor, M. O.; Ward,
D. L.; Brubaker, C. H., J r. Organometallics 1988, 7, 1504.
(31) (2,4,6-Triisopropylphenyl)selenenyl bromide was prepared from
bis(2,4,6-triisopropylphenyl) diselenide and bromine in CCl4: Boch-
mann, M; Webb, K. J .; Hursthouse, M. B.; Mazid, M. J . Chem. Soc.,
Dalton Trans. 1991, 2317.

Rh- and Ir-Catalyzed Hydrosilylation
Organometallics, Vol. 15, No. 1, 1996 379
(3H, d, J ) 6.48 Hz). Anal. Calcd for C30H27FePS: C, 71.15;
H, 5.37. Found: C, 71.18; H, 5.31.
values of the alcohols were determined by HPLC using Daicel
Chiralcel OJ , OD, OB, and OF columns. The configuration of
the alcohols was determined by the reported optical rotation.32
Gen er a l P r oced u r e for Rh od iu m -Ca ta lyzed Asym -
m et r ic Hyd r osilyla t ion of Im in es Usin g 2 a s a Ch ir a l
Liga n d . The reaction was carried out by a method similar to
that described in the previous section. In this case only the
purification method of the product was different. Purification
was carried out by TLC because at high temperature (distil-
lation) the product decomposed in many cases. The ee value
of the product was determined by HPLC using Daicel Chiralcel
OJ , OD, OB, and OF columns.
Gen er a l P r oced u r e for Rh od iu m -Ca ta lyzed Asym -
m etr ic Hyd r ogen a tion of r-Aceta m id ocin n a m ic Acid
Usin g 2 a s a Ch ir a l Liga n d . In a 20-mL flask were placed
a metal complex and a chiral ligand under argon. Anhydrous
EtOH (3.0 mL) was added, and then the mixture was magneti-
cally stirred at room temperature for 1 h. This solution was
added by a syringe to another flask containing R-acetamido-
cinnamic acid (1.0 mmol) under 1 atm of hydrogen pressure.
After being stirred for a suitable time, the reaction mixture
was slowly added to 0.5 N NaOH(aq) (30 mL) and extracted
with diethyl ether (50 mL × 3). To the water layer, 1 N
HCl(aq) was added until the solution became acidic, and then
it was extracted with diethyl ether (50 mL × 3) and dried over
anhydrous MgSO4. The extract was concentrated under
reduced pressure by an aspirator to leave an almost pure
hydrogenated product (49% yield). The ee value and the
configuration were determined by optical rotation in metha-
nol.33
P r ep a r a tion of 32. In a 20-mL flask was placed the
cationic rhodium compound ([Rh(COD)2]BF4) (21 mg, 0.052
mmol) and (R,S)-(Fc*Se)2 (2) (35 mg, 0.051 mmol) under argon.
Anhydrous THF (2.0 mL) was added, and then the resulting
solution was magnetically stirred at room temperature for 20
h during which time the color of the solution turned from pale
orange to red. When diethyl ether (5 mL) was added to the
solution, 32 was precipitated as a brown solid, which was
collected by filtration and dried under atmospheric pressure:
24 mg, 53% isolated yield based on 2, mp 185-187 °C (dec);
1H-NMR (acetone-d6) δ 4.92 (2H, m), 4.84 (2H, q, J ) 7.02 Hz),
4.79 (2H, m), 4.64 (2H, m), 4.30 (10H, s), 3.00 (12H, s, -NMe2),
1.99 (6H, d, J ) 7.02 Hz). Anal. Calcd for C28H36BF4Fe2-
N2RhSe2: C, 39.11; H, 4.22; N, 3.26. Found: C, 38.98; H, 4.60;
N, 2.73. [For comparison, 2: 1H-NMR (acetone-d6) δ 4.47 (2H,
m), 4.30 (4H, m), 4.08 (10H, s), 3.93 (2H, q, J ) 7.02 Hz), 2.14
(12H, s, -NMe2), 1.35 (6H, d, J ) 7.02 Hz).]
Similarly, other (S,R)-ferrocenylphosphines (23-25) were
prepared from (S,R)-PPFOAc or (S,R)-BPPFOAc and the
corresponding diphenyl dichalcogenide, respectively.
1
23: a yellow solid; mp 119-121 °C; H-NMR δ 7.53-7.59
(2H, m), 7.16-7.42 (23H, m), 4.46 (1H, m), 3.45-4.38 (7H, m),
1.55 (3H, d, J ) 6.48 Hz). Anal. Calcd for C42H37FeP2S: C,
72.94; H, 5.39. Found: C, 72.77; H, 5.07. Yield: 81%.
24: An orange oil; 1H-NMR δ 7.61-7.68 (2H, m), 7.28-7.41
(3H, m), 7.16-7.29 (10H, m), 4.65 (1H, m), 4.35 (2H, m), 4.05
(1H, m), 3.90 (5H, s), 1.81 (3H, d, J ) 6.48 Hz). Anal. Calcd
for C30H27FePSe: C, 65.12; H, 4.92. Found: C, 65.34; H, 5.01.
Yield: 100%.
25: a yellow solid; mp 73-75 °C; 1H-NMR δ 7.52-7.59 (2H,
m), 7.17-7.38 (23H, m), 4.56 (1H, m), 3.42-4.38 (7H, m), 1.67
(3H, d, J ) 6.48 Hz). Anal. Calcd for C42H37FeP2Se: C, 68.31;
H, 5.05. Found: C, 67.97; H, 5.06. Yield: 74%.
P r ep a r a tion of Bis(ch a lcogen id es) (26-28) (Sch em e 6).
A typical experimental procedure for the preparation of (S,S)-
26 is as follows. In a two-necked 50 mL round bottom flask
containing a magnetic stirring bar were placed diphenyl
disulfide (144 mg, 0.66 mmol) and NaBH4 (84 mg, 2.22 mmol)
under nitrogen. Ethanol (15 mL) was added to the flask at 0
°C, and the mixture became homogeneous after stirring for
0.5 h at room temperature. An ethanol (5 mL) solution of (S,S)-
DIOTs (300 mg, 0.64 mmol) was then added to the resulting
solution, and the mixture was stirred at the reflux temperature
(bath temperature 100 °C) for 5 h. The mixture was treated
with brine (100 mL) and then extracted with CH2Cl2 (50 mL
× 3). The extract was dried over MgSO4 and evaporated to
leave a colorless oil of 26, which was purified by column
chromatography on silica gel with hexane/ethyl acetate (9/1)
as an eluent: 216 mg, 0.62 mmol (97% yield based on DIOTs);
1H-NMR δ 7.17-7.39 (10H, m), 4.07 (2H, m), 3.21 (4H, m),
1.41 (6H, s); 13C-NMR δ 135.5 (s), 129.4 (d), 129.0 (d), 126.3
(d), 110.0 (s), 79.0 (d), 37.0 (t), 27.3 (q). Anal. Calcd for
C
19H22O2S2: C, 65.86; H, 6.40. Found: C, 65.90; H, 6.37.
27: (S,S), a colorless oil; 1H-NMR δ 7.47-7.52 (4H, m),
7.22-7.27 (6H, m), 4.08 (2H, m), 3.17 (4H, m), 1.40 (6H, s);
13C-NMR δ 132.7 (d), 129.9 (s), 129.2 (d), 127.1 (d), 109.5 (s),
80.1 (d), 30.5 (t), 27.4 (q). Anal. Calcd for C19H22O2Se2: C,
51.83; H, 5.04. Found: C, 52.10; H, 5.25. Yield: 91%.
28: (S,S), a yellow oil; 1H-NMR δ 7.69-7.73 (4H, m), 7.15-
7.30 (6H, m), 4.03 (2H, m), 3.15 (4H, m), 1.34 (6H, s); 13C-
NMR δ 138.4 (d), 129.2 (d), 127.7 (d), 111.8 (s), 108.9 (s), 81.6
(d), 27.5 (q), 11.6 (t). Anal. Calcd for C19H22O2Te2: C, 42.45;
H, 4.13. Found: C, 42.72; H, 4.11. Yield: 72%.
Gen er a l P r oced u r e for Rh od iu m - or Ir id iu m -Ca ta -
lyzed Asym m etr ic Hyd r osilyla tion of Keton es Usin g
Va r iou s Ch ir a l Ch a lcogen id es a s Liga n d s. In a 20-mL
flask were placed a metal complex and a chiral ligand under
argon. Anhydrous THF (3.0 mL) was added by a syringe
through a septum, and then the mixture was magnetically
stirred at room temperature for 1 h. After addition of ketone
(1.0 mmol) in anhydrous THF (1.0 mL) by a syringe, the
reaction flask was dipped in a thermoregulated bath at 0 °C.
Silane (1.5 mmol) was then added slowly by a syringe. For
the workup, methanol (1 mL) was added slowly to the reaction
mixture at 0 °C. After gas evolution ceased, 1 N HCl(aq) (5
mL) was added to the reaction mixture, which was stirred for
1 h at room temperature. The mixture was extracted with
brine (50 mL) and diethyl ether (50 mL × 3) and dried over
anhydrous MgSO4. The extract was concentrated under
reduced pressure by an aspirator. After the residue was
distilled under reduced pressure by use of a Kugelrohr, the
corresponding alcohol was obtained in a pure form. The ee
Ack n ow led gm en t. We thank Dr. Teruyuki Kondo
of this Division for assistance with the X-ray analysis.
The present work was supported in part by a Grant-
in-Aid for Scientific Research from the Ministry of
Education, Science, and Culture of J apan and by a
Fellowship (to Y.N.) of the J apan Society for the
Promotion of Science for J apanese J unior Scientists.
Su p p or tin g In for m a tion Ava ila ble: Text describing
X-ray procedures and tables of crystal structure data, hydrogen
positional and B parameters, anisotropic thermal parameters,
and complete bond distances and angles for 8 (26 pages).
Ordering information is given on any current masthead page.
OM950533U
(32) Kasai, M.; Froussios, C.; Ziffer, H. J . Org. Chem. 1983, 48, 459.
(33) Fryzuk, M. D.; Bosnich, B. J . Am. Chem. Soc. 1977, 99, 6262.