Synthesis of enantiomerically pure Sb-chirogenic organoantimony compounds and their crystal structures

Article abstract of DOI:10.1016/j.jorganchem.2005.10.042

Sb-chirogenic organoantimony compounds (±)-5a-c bearing heteroatom moieties such as 4,4-dimethyl-2-oxazolinyl, methoxymethyl, and diphenylphosphanyl substituents on the o-position of an aryl group have been prepared by nucleophilic displacement of the ethynyl moiety on (1-naphthyl)(phenylethynyl)(p-tolyl)stibane (3) with aryllithium reagents (2a-c). The optical resolution of the racemic (±)-5a,b was attained via separation of a diastereomeric mixture of their palladium complexes (S)-7 formed from the reactions of (±)-5a,b with di-μ-chlorobis[(S)-dimethyl(1-ethyl-α-naphthyl)aminato-C ²,N]dipalladium(II) (6). The enantiomerically pure Sb-chirogenic stibanes isolated here were optically stable, and no racemization on the chiral antimony center was observed even when they were allowed to stand at room temperature for over 72 h in chloroform. The structure of 5a,b including the absolute configuration was determined by single crystal X-ray analyses of (+)-5aB and antimony-palladium complex (7bB), respectively. The analyses also revealed the presence of intramolecular interaction between the antimony and sp²-nitrogen atoms in the molecule Sb(S)-(+)-5aB.

Full text of DOI:10.1016/j.jorganchem.2005.10.042

Journal of Organometallic Chemistry 691 (2006) 2213–2220
www.elsevier.com/locate/jorganchem
Synthesis of enantiomerically pure Sb-chirogenic
organoantimony compounds and their crystal structures
a
a
Shuji Yasuike a,b, Yoshihito Kishi , Shin-ichiro Kawara ,
c
a,
*
Kentaro Yamaguchi , Jyoji Kurita
a
Faculty of Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi, Ho-3, Kanazawa 920-1181, Japan
Organization for Frontier Research in Preventive Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi, Kanazawa 920-1181, Japan
b
c
Faculty of Pharmaceutical Sciences at Kagawa Campus, Tokushima Bunri University, Shido, Sanuki 769-2193, Japan
Received 17 October 2005; accepted 24 October 2005
Available online 19 December 2005
Abstract
Sb-chirogenic organoantimony compounds ( )-5a–c bearing heteroatom moieties such as 4,4-dimethyl-2-oxazolinyl, methoxymethyl,
and diphenylphosphanyl substituents on the o-position of an aryl group have been prepared by nucleophilic displacement of the ethynyl
moiety on (1-naphthyl)(phenylethynyl)(p-tolyl)stibane (3) with aryllithium reagents (2a–c). The optical resolution of the racemic ( )-5a,b
was attained via separation of a diastereomeric mixture of their palladium complexes (S)-7 formed from the reactions of ( )-5a,b with
di-l-chlorobis[(S)-dimethyl(1-ethyl-a-naphthyl)aminato-C2,N]dipalladium(II) (6). The enantiomerically pure Sb-chirogenic stibanes
isolated here were optically stable, and no racemization on the chiral antimony center was observed even when they were allowed to
stand at room temperature for over 72 h in chloroform. The structure of 5a,b including the absolute configuration was determined
by single crystal X-ray analyses of (+)-5aB and antimony–palladium complex (7bB), respectively. The analyses also revealed the presence
of intramolecular interaction between the antimony and sp2-nitrogen atoms in the molecule Sb(S)-(+)-5aB.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Antimony; Nucleophilic substitution; Sb-chirogenic; Palladium complex; Optical resolution; X-ray analysis; Hypervalent coordination
1. Introduction
amine group by complexation with resolving agents having
these functional groups. However, this research field has
not been investigated over a period of 50 years, because
these compounds were reported to be not so stable and
led to gradual racemization on the antimony center in solu-
tion. In view of this background, we are interested in the
synthesis of Sb-chirogenic organoantimony compounds
and their stereo-chemical properties. We have recently
reported a versatile route for the synthesis of Sb-chirogenic
organoantimony compounds through stepwise nucleophilic
displacement of the ethynyl groups on diethynylstibanes
with Grignard and/or organolithium reagents [6a], as well
as their resolution into optically pure form via separation
of a diastereomeric mixture of the palladium complex
formed from the reaction of the Sb-chiral compounds
and ortho-palladated benzylamine derivatives [6b,7]. As a
further extension of this work, we report here the synthesis
Optically active compounds bearing chirality on group
15 elements are currently a project of great interest in main
group chemistry [1]. Among these, the most popular and
actively investigated examples are P-chirogenic phosphine
compounds which are important synthetic tools for ligand
chemistry in asymmetric synthesis [2]. However, studies on
Sb-chirogenic organoantimony(III) compounds (stibanes)
have been very limited up to now. Synthesis of this kind
of compounds was first demonstrated earlier by Campbell
[3], who resolved optically active phenoxastibanes, stibaflu-
orenes [4] and triarylstibanes [5] having a carboxyl or an
*
Corresponding author. Tel.: +81 76 229 1165/6210; fax: +81 76 229
2781.
E-mail address: j-kurita@hokuriku-u.ac.jp (J. Kurita).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.10.042

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S. Yasuike et al. / Journal of Organometallic Chemistry 691 (2006) 2213–2220
of enantiomerically pure open-chain Sb-chirogenic organ-
oantimony compounds having a heteroatom moiety at
the ortho-position on an aryl group and the X-ray crystal
structure of these molecules.
ture of the antimony–palladium complex formed from the
reaction of the stibindoles with an optically active ortho-
palladated benzylamine derivative as a preliminary commu-
nication [7]. According to this finding, we performed the
separation of these new open-chain Sb-chirogenic antimony
compounds [( )-5a–c] via antimony–palladium complexes.
Treatment of ( )-5a–c with di-l-dichloro-bis{(S)-2-[(di-
methylamino)methyl]phenyl-C1,N}dipalladium(II) resulted
in coordination of the antimony to the palladium to form
antimony–palladium complexes. However, all attempts to
separate the diastereomeric mixture by fractional recrystal-
lization from a variety of solvents or by column chromatog-
raphy have been unsuccessful. Therefore, we altered the
resolving reagent from the ortho-palladate benzylamine
derivative to di-l-chlorobis[(S)-dimethyl(1-ethyl-a-naph-
thyl)aminato-C2,N]dipalladium(II) (6). The reaction of
( )-5a–c with 6 in dichloromethane at room temperature
resulted in the coordination to give rise to a diastereomeric
mixture of the palladium complexes (7a–c) in almost quan-
titative yields. In the case of 7a, the TLC analysis on silica
gel showed a large difference in Rf values between both dia-
stereomers [Rf = 0.43 for 7aA and 0.21 for 7aB (dichloro-
methane:ether = 20:1)], and the mixture could be easily
separated into diastereomerically pure 7aA (less polar)
and 7aB (polar) by silica gel column chromatography using
the same solvent system for TLC as an eluent. Similar chro-
matographic separation of 5b–palladium complex (7b)
afforded 7bA (less polar) and 7bB (polar) in good yield.
Unfortunately, many attempts to separate the mixture of
5c–palladium complex (7c) having a phosphorous moiety
were unsuccessful so far. The diastereomerically pure palla-
dium complexes 7aA and 7aB bearing an oxazoline ring
were obtained as yellow foams, whereas those of 7bA and
2. Results and discussion
2.1. Preparation of Sb-chirogenic stibanes
The Sb-chirogenic antimony compounds (5a–c) dis-
cussed in this paper were prepared according to the gen-
eral route based on the modified method reported by us
previously [6]. The synthetic route is shown in Scheme
1, and the results including the reaction conditions are
listed in Table 1. Reaction of (1-naphthyl)(phenylethy-
nyl)(p-tolyl)stibane (3) with excess (2–5 equiv.) of arylli-
thium reagents (2a–c) generated from 1a–c and n-BuLi
at low temperature brought about nucleophilic displace-
ment of the phenylacetylene moiety on 3 into aryl groups
to afford ( )-5a–c in good yields. We have recently
reported that a thermodynamically more stable organoli-
thium species is preferentially released in the ligand
exchange reactions involving such intermediate as 4a–c.
In the present reaction, predominant elimination of the
ethnyl group over the other three aryl groups occurred
with the formation of phenylethnyllithium which is more
stable than aryllithium.
2.2. Resolution of Sb-chirogenic stibanes via separation of a
diastereomeric mixture of their palladium complex
We have recently reported a useful route for resolution of
racemic stibindoles via separation of a diastereomeric mix-
Li+
p-Tol
Sb
Ph
R
R
X
1-naphthyl
R
3
Sb 1-naphthyl
p-Tol
Sb p-Tol
1-naphthyl
1a: X = H 1b, c: X = Br
2a-c: X = Li
Li
Ph
Ph
4a-c
( )-5a-c
Me
Me
R = a:
PPh2
OMe
N
b:
c:
O
Scheme 1.
Table 1
Nucleophilic displacement reaction of (1-naphthyl)(phenylethynyl)(p-tolyl)stibane (3) with aryllithium reagents (2)
Aryllithium (equiv.)
Time (h)
Temp. (ꢁC)
Product
Yield (%)
Appearance
2a (5.0)
2b (2.0)
2c (3.0)
4
2
2
0
(
(
(
)-5a
)-5b
)-5c
73
90
88
Mp. 148–150 ꢁC
Mp. 93.5–95 ꢁC
Colorless oil
ꢀ20
ꢀ80 to ꢀ20

S. Yasuike et al. / Journal of Organometallic Chemistry 691 (2006) 2213–2220
2215
7bB having a methoxymethyl group were isolated as yellow
prisms (see Scheme 2).
mined to be R for (ꢀ)-5aA and S for (+)-5aB by the single
crystal X-ray analysis of 5aB, and those of (ꢀ)-5bA and
(+)-5bB were inevitably assigned to be R for (ꢀ)-5bA and
S for (+)-5bB on the basis of the result of the X-ray anal-
ysis of 7bB noted in the following section.
We next performed the decomplexation of the palladium
complexes 7aA, 7aB, 7bA and 7bB to obtain enantiomeri-
cally pure Sb-chirogenic stibanes (+)- and (ꢀ)-(5a,b). Thus,
the oxazoline-substituted palladium complexes 7aA and
7aB, on treatment with 1,2-bis(diphenylphosphino)ethane
in dichloromethane, brought about an easy ligand exchange
reaction to afford enantiomerically pure Sb-chirogenic
2.3. X-ray crystal structures of Sb-chirogenic stibanes
In order to gain deeper insight into the stereochemistry
of the palladium complexes (7) and optically pure stibanes
(5), single crystal X-ray analyses of 7bB and 5aB were
made, and the results are shown in Fig. 1 and Table 2
for 7bB, and Fig. 2 and Table 3 for 5aB.
24
stibanes (ꢀ)-5aA {m.p. 139–142 ꢁC, ½aꢁD ¼ ꢀ14:8ꢂ} and
24
(+)-5aB {m.p. 139–141 ꢁC, ½aꢁD ¼ þ14:3ꢂ}, respectively, in
excellent yields. The decomplexation of methoxymethyl
group-substituted stibanes 7bA and 7bB was also achieved
by their reaction with triphenylphosphine giving rise to the
corresponding palladium-free (ꢀ)-5bA {Colorless oil,
In the molecular structure of 7bB, only the antimony
atom coordinates to the palladium on the ortho-palladated
naphthylethylamine derivative with the bond length of
24
24
½aꢁD ¼ ꢀ9:0ꢂ} and 5bB {Colorless oil, ½aꢁD ¼ þ8:7ꢂ},
˚
respectively.
Pd–Sb to be 2.5221(6) A. Also apparent is that the anti-
The absolute configurations on the antimony center of
these optically pure Sb-chirogenic stibanes could be deter-
mony and the nitrogen on the palladacycle develop a trans
relationship with the bond angles of N–Pd–Sb to be
178.54(12)ꢁ, and the palladium of 7bB adopts square-planar
geometry. Similar relationship was observed in the crystal
structure of the palladium complex of 1-phenylstibindole
[7]. It also appeared that the antimony atom in 7bB has
R-configuration. It is noteworthy that an intramolecular
coordination between the antimony and oxygen atoms
R
*
Sb
1-naphthyl
˚
(Sbꢃ ꢃ ꢃO: 3.00 A) is observed in the crystal structure of
p-Tol
( )-5a, b
7bB, and the central antimony is in the quasi-tetrahedral
(TH) geometry.
Single crystal X-ray analysis of 5aB revealed its S-
configuration at the Sb-chiral center and the presence of
S
NMe
*
2
Pd
Cl
6
2
S
*
S
*
1-naphthyl
1-naphthyl
R
S
*
*
p-Tol
R
Pd NMe2
Sb
p-Tol
R
Pd NMe2
Sb
Cl
Cl
[Sb(S)-C(S)] -7aB
[Sb(S)-C(S)] -7bB
(more polar)
[Sb(S)-C(S)] -7aA
[Sb(S)-C(S)] -7bA
(less polar)
DPPE
or PPh3
DPPE
or PPh3
R
R
S
*
R
*
Sb
1-naphthyl
Sb 1-naphthyl
p-Tol
p-Tol
Sb(S)-(+)-5aB
Sb(S)-(+)-5bB
Sb(R)-(-)-5aA
Sb(R)-(-)-5bA
Fig. 1. Molecular structure of Sb(S),C(S)-7bB. All hydrogen atoms and
Scheme 2.
benzene molecule in the crystal were omitted for clarity.

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S. Yasuike et al. / Journal of Organometallic Chemistry 691 (2006) 2213–2220
Table 2
Table 3
˚
˚
Selected bond lengths (A) and bond angles (ꢁ) for 7bB
Selected bond lengths (A) and bond angles (ꢁ) for 5aB
Bond lengths
N–Pd
Pd–C(1)
Pd–Cl
Bond lengths
Sb–C(1)
Sb–C(10)
Sb–C(100)
Sb–N
2.126(4)
2.006(5)
2.3956 (11)
2.5221(6)
2.133(5)
2.132(5)
2.137(5)
3.001(4)
2.177(5)
2.170(5)
2.183(5)
2.813(4)
Pd–Sb
Sb–C(2)
Sb–C(3)
Sb–C(4)
Sb–O
Bond angles
C(1)–Sb–C(10)
C(1)–Sb–C(100)
C(10)–Sb–C(100)
C(1)–Sb–N
100.3(2)
94.5(2)
93.8(2)
70.3(2)
76.9(2)
160.0(2)
Bond angles
N–Pd–Cl
N–Pd–C(1)
Sb–Pd–Cl
Sb–Pd–C(1)
N–Pd–Sb
C(1)–Pd–Cl
Pd–Sb–C(2)
Pd–Sb–C(3)
Pd–Sb–C(4)
C(2)–Sb–C(3)
C(2)–Sb–C(4)
C(3)–Sb–C(4)
94.75(11)
81.04(17)
84.21(3)
C(10)–Sb–N
C(100)–Sb–N
Dihedral angles
99.94(13)
178.54(12)
174.57(12)
115.09(14)
127.82(12)
112.60(12)
100.99(18)
96.98(17)
98.08(17)
Sb–C(1)–C(2)–C(ox)
C(1)–C(2)–C(ox)–N
C(3)–C(2)–C(ox)–O
12.7(6)
7.7(8)
8.3(7)
pseudo-trigonal bipyramid (TBP) structure, and C(100) on
the tolyl group and the nitrogen on the oxazoline ring lie
approximately trans to each other with the bond angle of
N–Sb–C(100) to be 160.0(2)ꢁ. These results showed that, in
the structure of 5aB, the 1-naphthyl and oxazoline-substi-
tuted aryl groups occupy an equatorial position with a pair
of electrons on antimony, and the nitrogen on the oxazo-
line ring and the p-tolyl group adopt apical position. The
bond distance between the antimony and C(100)
˚
[2.183(5) A] which hold apical positions is slightly longer
than those of Sb–C(1) [2.177(5) A] and Sb–C(10)
˚
˚
[2.170(5) A]. These results are consistent with our previous
reports for the TBP structure in organoantimony com-
pounds having intramolecular interaction [9]. It is well
known that a more electronegative substituent tends to pre-
fer an apical position and the apical bond is longer than
that of the equatorial bond in the TBP structure [10]. Tak-
ing these facts and our above finding into account, the p-
tolyl group is considered to be more electronegative than
the 1-naphthyl group, although their steric factor could
not be accounted for. To the best of our knowledge, this
is the first example for disclosing the existence of an intra-
molecular interaction between antimony and sp2-nitrogen
atoms, although trivalent organoantimony compounds
bearing an aryl group with NMe2 or CH2NMe2 substituent
in the ortho-position have been widely reported to have the
interaction between the antimony and sp3-nitrogen atoms
[9,11]. The small torsional angles of C(1)–C(2)–C(ox)–N
[7.7(8)ꢁ] and C(3)–C(2)–C(ox)–O [8.3(7)ꢁ] indicate that
the planes of the dimethyl-2-phenyl-2-oxazoline and its
phenyl rings lie in nearly horizontal geometry.
Fig. 2. Molecular structure of Sb(S)-(+)-5aB. All hydrogen atoms were
omitted for clarity.
Some group 15 and 16 compounds having intramolecu-
lar interactions (hypervalent compounds) underwent intra-
molecular positional isomerization of the substituents on
the heavier atom [11]. However, the enantiomerically pure
Sb-chirogenic stibanes 5aA, 5bA, 5bA, and 5bB isolated
here were stereochemically stable, and no racemization
took place on the chiral antimony centers even when they
an intramolecular coordination between the antimony and
nitrogen atoms; the distance between the antimony and
nitrogen atoms is 2.813(4) A, which corresponds to 75%
˚
of the sum of the van der Waals radii of both elements
and accords with 133% of the covalent bond length
˚
(2.11 A) [8]. The central antimony atom exhibits a

S. Yasuike et al. / Journal of Organometallic Chemistry 691 (2006) 2213–2220
2217
were allowed to stand at room temperature for over 72 h in
chloroform, which could be ascertained by measuring the
change of their optical rotation.
4.2. Nucleophilic displacement of (1-naphthyl)-
(phenylethynyl)(p-tolyl)stibane (3) with aryllithiums
(2a–c)
3. Conclusion
4.2.1. ( )-4,4-Dimethyl-2-{2-[(1-naphthyl)(4-tolyl)-
stibano]phenyl}-1,3-oxazoline (5a)
We have presented here a versatile synthetic route of
enantiomerically pure open-chain Sb-chirogenic organoan-
timony compounds having a heteroatom moiety on an aryl
group. The racemic stibanes synthesized by nucleophilic
displacement of the ethynyl moiety on (a-naphthyl)(phe-
nylethynyl)(p-tolyl)stibane with appropriate aryllithium
reagents could be easily separated via their palladium com-
plexes. The enantiomerically pure Sb-chirogenic stibanes
isolated here were stereochemically stable and no racemiza-
tion took place even if the stibanes bear the fourth ligand
with intramolecular coordination. Along with these find-
ings, the structures of the antimony–palladium complex
of 7bB and Sb-chirogenic stibane Sb(S)-(+)-5aB were made
clear by their single crystal X-ray analyses. These analyses
also revealed the presence of intramolecular coordination
between the antimony and the oxygen in the palladium
complex 7bB, and that of antimonyꢃ ꢃ ꢃsp2-nitrogen coordi-
nation in the palladium-free Sb(S)-(+)-5aB in the crystal
state.
To a stirring solution of aryllithium (2a) [15], generated
from 4,4-dimethyl-2-phenyl-2-oxazoline (1a: 3.50 g,
20 mmol) and n-BuLi (1.57 M solution in hexane,
14 mL, 22 mmol) in anhydrous ether (60 mL), solids of
(1-naphthyl)(phenylethynyl)(p-tolyl)stibane (3: 1.76 g,
4 mmol) was added in small portions over 40 min at
0 ꢁC. After stirring for 6 h at the same temperature, the
reaction mixture was diluted with ether (50 mL) and water
(50 mL). The organic layer was separated and the aqueous
layer was extracted with ether (50 mL). The combined
organic solution was washed with brine, dried over anhy-
drous MgSO4, and concentrated in vacuo. The residue
was subjected to column chromatography on silica gel
with a mixture of hexane–dichloromethane (4:1) to give
( )-5a as colorless prisms (1.50 g, 73%), m.p. 148–150 ꢁC
(from ethanol–dichloromethane). 1H NMR (500 MHz)
dppm: 0.75 (3H, s), 1.07 (3H, s), 2.31 (3H, s), 3.91 (2H,
s), 7.07 (2H, d, J = 8.3 Hz), 7.21–7.46 (9H, m), 7.78
(1H, d, J = 7.8 Hz), 7.83–7.85 (1H, m), 7.92 (1H, d,
J = 7.8 Hz), 8.34–8.37 (1H, m). 13C NMR (125 MHz)
dppm: 21.37 (q), 27.82 (q), 28.16 (q), 79.31 (t), 125.37
(d), 125.65 (d), 126.23 (d), 128.12 (s), 128.20 (d), 138.55
(d), 128.70 (d), 129.34 (d), 129.42 (s), 130.89 (d), 132.52
(s), 133.59 (s), 134.86 (d), 136.54 (d), 137.24 (d), 137.49
(d), 137.97 (d), 139.16 (s), 142.70 (s), 144.01 (s), 162.49
(s). EI-MS (relative intensity) m/z: 513 (M+, 0.6), 422
(85), 386 (100), 349 (42), 314 (52), 247 (13). Anal. Calc.
for C28H26NOSb: C, 65.40; H, 5.10; N, 2.72. Found: C,
65.40; H, 5.20; N, 2.72%.
4. Experimental
4.1. General
Reactions requiring anhydrous conditions were per-
formed with the usual precaution for rigorous exclusion
of air and moisture under an argon atmosphere. Ether
was distilled from its LiAlH4 suspension and dried over
sodium wire. Melting points were taken on a Yanagimoto
micro melting point hot-stage apparatus and are not cor-
1
rected. H NMR (TMS: d: 0.00 as an internal standard)
4.2.2. ( )-(2-Methoxymethylphenyl)(1-naphthyl)-
(p-tolyl)stibane (5b)
and 13C NMR (CDCl3: d: 77.00 as an internal standard)
spectra were recorded on JEOL JNM-EX-90 (90 MHz)
and JEOL JNM-ECP500 (500 and 125 MHz) spectrome-
ters in CDCl3 unless otherwise stated. Mass spectra
(MS) and high-resolution mass spectra (HRMS) were
obtained on a JEOL JMP-DX300 instrument (70 eV,
300 lA). Optical rotations were measured on a JUSCO
DIP-370 digital polarimeter. All chromatographic separa-
tions were accomplished with Silica Gel 60 N (Kanto
Chemical Co., Inc.). Thin-layer chromatography (TLC)
was performed with Macherey-Nagel Pre-coated TLC
plates Sil G25 UV254. 1-Bromo-2-methoxymethylbenzene
(1b) [12], (2-bromophenyl)diphenylphosphane (1c) [13],
(phenylethynyl)(1-naphthyl)(p-tolyl)stibane (3) [6b] and
(+)-di-l-chlorobis{(S)-2-[1-(dimethylamino)ethyl]naphthyl-
C2,N}dipalladium(II) (6) [14] were prepared according to
the reported procedures. 4,4-Dimethyl-2-phenyl-2-oxazo-
line (1a) was purchased from the Sigma–Aldrich Japan.
n-Butyl lithium (n-BuLi: 1.51–1.60 M solution in hexane)
was obtained from Kanto Chemical Co., Inc. Japan.
To a stirring solution of aryllithium (2b) [16], generated
from 1-bromo-2-methoxymethylbenzene (1b) (3.02 g,
15 mmol) and n-BuLi (1.57 M solution in hexane,
9.3 mL, 14.6 mmol) in anhydrous ether (40 mL), solids
of 3 (3.31 g, 7.5 mmol) was added in small portions over
50 min at ꢀ20 ꢁC. After stirring for 2 h at the same tem-
perature, the reaction mixture was allowed to stand for
1 h at r.t. The mixture was diluted with ether (150 mL)
and water (100 mL). The resulting organic layer was sep-
arated and the aqueous layer was extracted with ether
(50 mL). The combined organic solution was washed with
brine, dried over anhydrous MgSO4, and evaporated in
vacuo. The residue was subjected to column chromatogra-
phy on silica gel with a mixture of hexane–dichlorometh-
ane (4:1) to give ( )-5b as colorless prisms (3.10 g, 90%),
m.p. 93.5–95 ꢁC (from hexane–benzene). 1H NMR
(500 MHz) dppm: 2.33 (3H, s), 3.11 (3H, s), 4.56 (2H,
s), 7.08–7.12 (6H, m), 7.19 (1H, d, J = 6.4 Hz), 7.24–
7.36 (6H, m), 7.41–7.48 (2H, m), 7.82 (1H, d,

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S. Yasuike et al. / Journal of Organometallic Chemistry 691 (2006) 2213–2220
J = 7.8 Hz), 7.85 (1H, d, J = 7.8 Hz), 8.18 (1H, d,
J = 8.2 Hz). 13C NMR (125 MHz) dppm: 21.39 (q),
57.50 (q), 76.31 (t), 125.66 (d), 126.00 (d), 126.20 (d),
128.25 (d), 128.38 (d), 138.47 (d), 128.79 (d), 128.90 (d),
129.20 (d), 129.64 (d), 133.68 (s), 134.31 (s), 135.50 (d),
136.69 (d), 137.17 (d), 137.85 (s), 138.20 (s), 138.54 (s),
139.47 (s), 143.62 (s). EI-MS (relative intensity) m/z: 460
(M+, 53), 369 (26), 333 (100), 342 (42), 212 (21). Anal.
Calc. for C25H23OSb: C, 65.11; H, 5.03. Found: C,
65.15; H, 5.14%.
mixture of (+)- and (ꢀ)-5a (160 mg, 16%, colorless oil,
Rf = 0.90), Sb(S),C(S)-7aA (512 mg, 30%), and Sb(S),
C(S)–7aB (836 mg, 49%). The palladium-free (+)- and
24
(ꢀ)-5a {½aꢁD ¼ ꢀ13:1ꢂ (c 1.0, chloroform), 88.5 %ee} were
formed by the decomplexation of 7aA and 7aB during
chromatographic separation, indicating 7aA was more
susceptible to depalladation than 7aB under these separa-
tion conditions. 7aA: yellow oil, Rf = 0.43 (dichlorometh-
24
ane:ether = 20:1), ½aꢁD ¼ þ63:5ꢂ (c 1.0, chloroform). 1H
NMR (90 MHz) d ppm: 1.00 (6H, br-s), 1.99 (3H, d,
J = 5.1 Hz), 2.32 (3H, s), 2.79 (6H, s), 3.91 (2H, s),
4.15–4.40 (1H, m), 6.97–8.80 (21H, m). FAB-MS (relative
intensity) m/z: 855 (M + 1+, 0.9), 819 (9), 422 (35),
386 (96), 295 (12), 198 (100). FAB-HRMS m/z:
855.1141 (Calc. for C42H42ClN2OPdSb: 855.1147). 7aB:
yellow oil, Rf = 0.21 (dichloromethane:ether = 20:1),
4.2.3. ( )-(2-Diphenylphosphinophenyl)(1-naphthyl)-
(p-tolyl)stibane (5c)
To a stirring solution of aryllithium (2c) [13b], gener-
ated from (2-bromophenyl)diphenylphosphane (1c)
(1.02 g, 3 mmol) and t-BuLi (1.41 M solution in hexane,
4.25 mL, 6 mmol) in anhydrous ether (30 mL), solids of
3 (440 mg, 1.0 mmol) was added in small portions over
25 min at ꢀ80 ꢁC. After stirring for an additional
30 min, the reaction mixture was allowed to warm slowly
to ꢀ20 ꢁC. The mixture was diluted with benzene (50 mL)
and water (30 mL). The organic layer was separated and
the aqueous layer was extracted with benzene (30 mL).
The combined organic solution was washed with brine,
dried over anhydrous MgSO4, and evaporated in vacuo.
The residue was subjected to column chromatography
on silica gel with a mixture of hexane–benzene (5:1) to
give ( )-5c as colorless oil (528 mg, 88%). 1H NMR
(500 MHz) dppm: 2.31 (3H, s), 7.08 (2H, d, J = 6.4 Hz),
7.12–7.27 (17H, m), 7.32 (1H, d, J = 6.4 Hz), 7.38 (1H,
t, J = 7.6 Hz), 7.44 (1H, t, J = 7.6 Hz), 7.77 (1H, d,
J = 8.2 Hz), 7.82 (1H, d, J = 8.2 Hz), 8.04 (1H, d,
J = 8.2 Hz). 13C NMR (125 MHz) d ppm: 21.36 (q),
125.07 (d), 125.62 (d), 125.94 (d), 126.13 (d), 128.22 (d,
JC,P), 128.46 (d), 128.71 (d), 128.87 (d), 129.01 (d),
129.64 (d), 129.76 (d), 130.13 (d), 133.51 (d, JC,P),
133.62 (d, JC,P), 134.14 (s), 135.85 (d), 136.52 (s), 136.91
(d), 137.73 (s), 138.14 (s), 141.75 (d). EI-MS (relative
intensity) m/z: 600 (M+, 100), 523 (63), 473 (88), 382
(19), 183 (64). EI-HRMS m/z: 600.0963 (Calc. for
C35H28PSb: 600.0967).
24
1
½aꢁD ¼ þ3:63ꢂ (c 1.0, chloroform). H NMR (90 MHz) d
ppm: 0.98 (6H, br-s), 1.85 (3H, d, J = 5.9 Hz), 2.32 (3H,
s), 2.88 (3H, br-s), 2.89 (3H, br-s), 3.91–4.31 (3H, m),
6.81–8.48 (21H, m). FAB-MS (relative intensity) m/z:
855 (M + 1+, 0.4), 819 (11), 422 (32), 386 (100), 295
(12), 198 (98). FAB-HRMS m/z: 855.1147 (Calc. for
C42H42ClN2OPdSb: 855.1147).
4.3.2. Sb(R)- and Sb(S)-(2-methoxymethylphenyl)-
(1-naphthyl)(p-tolyl)stibane–palladium complexes
(7bA, 7bB)
The palladium complexes 7bA and 7bB were prepared
according to the procedure described above from ( )-5b
(1.84 g, 4.0 mmol) and 6 (1.36 g, 2.0 mmol). The crude
product was separated by column chromatograph on sil-
ica gel using a mixture of dichloromethane–hexane (10:1)
as an eluent to give diastereomerically pure 7bA (1.53 g,
48%) and 7bB (1.44 g, 45%). 7bA: yellow prisms, m.p.
187–190 ꢁC (from benzene–ether), Rf = 0.48 (dichloro-
24
methane:hexane = 10:1), ½aꢁD ¼ þ143:8ꢂ (c 1.0, chloro-
form). 1H NMR (500 MHz) dppm: 1.93–2.01 (3H, m),
2.34 (3H, s), 2.86 (3H, s), 2.96 (3H, s), 3.05 (3H, s),
4.40–4.56 (3H, m), 6.88 (1H, d, J = 8.4 Hz), 7.09–7.92
(19H, m). FAB-MS (relative intensity) m/z: 766
(M ꢀ Cl+, 12), 445 (2), 333 (9), 301 (7), 198 (100).
FAB-HRMS m/z: 766.1110 (Calc. for C42H42N2OPdSb:
766.1220). Anal. Calc. for C39H39ClONPdSb: C, 58.45;
H, 4.91; N, 1.75. Found: C, 58.48; H, 5.30; N,
2.24%. 7bB: yellow prisms m.p. 107–110 ꢁC (from ben-
zene–ether), Rf = 0.34 (dichloromethane:hexane = 10:1),
4.3. Preparation and separation of diastereomerically pure
Sb(R)- and Sb(S)-(aryl)(1-naphthyl)(p-tolyl)stibane–
palladium complexes (7)
24
4.3.1. Sb(R)- and Sb(S)-4,4-dimethyl-2-{2-[(1-naphthyl)-
(4-tolyl)stibano]phenyl}-1,3-oxazoline–palladium
complexes (7aA, 7aB)
½aꢁD ¼ þ74:2ꢂ (c 1.0, chloroform). 1H NMR (500 MHz)
d ppm: 1.91–2.03 (3H, m), 2.28 (3H, s), 2.77 (3H, s),
2.99 (3H, s), 3.29 (3H, s), 4.33 (1H, m), 5.02 (2H, br-
s), 6.63 (1H, d, J = 8.7 Hz), 6.92 (1H, d, J = 8.3 Hz),
7.03–7.55 (15H, m), 7.65 (1H, d, J = 8.7 Hz), 7.82 (1H,
d, J = 7.8 Hz). FAB-MS (relative intensity) m/z: 766
(M ꢀ Cl+, 12), 445 (2), 333 (11), 301 (8), 198 (100).
FAB-HRMS m/z: 766.1104 (Calc. for C42H42N2OPdSb:
766.1220). Anal. Calc. for C39H39ClONPdSb+C6H6: C,
61.56; H, 5.17; N, 1.60. Found: C, 61.39; H, 5.15; N,
1.64%.
To a stirring solution of ( )-5a (1.0 g, 2 mmol) in
dichloromethane (5 mL), solids of (+)-di-l-chlorobis{(S)-
2-[1-(dimethylamino)ethyl]naphthyl-C2,N}dipalladium(II)
(6: 677 mg, 1 mmol) was added in small portions at room
temperature and the mixture was stirred for 10 min. The
reaction mixture was concentrated in vacuo, and the
resulting residue was separated by silica gel column chro-
matograph with dichloromethane–ether (20:1) to give a

S. Yasuike et al. / Journal of Organometallic Chemistry 691 (2006) 2213–2220
2219
4.4. Preparation of enantiomerically pure Sb(R)- and
Sb(S)-(aryl) (1-naphthyl)(p-tolyl)stibane (5a,b)
4.5. Crystallography
4.5.1. Crystal date for Sb(S)-(+)-5aB
Crystal dimensions 0.50 · 0.40 · 0.20 mm; C28H26-
NOSb, Mr = 514.27; orthorhombic space group P212121
4.4.1. Sb(R)-(ꢀ)-4,4-dimethyl-2-{2-[(1-naphthyl)-
(4-tolyl)stibano]phenyl}-1,3-oxazoline (5aA)
˚
To a solution of diastereomerically pure palladium
complex 7aA (423 mg, 0.50 mmol) in benzene (10 mL),
solids of 1,2-bis(dimethylphosphino)ethane (100 mg,
0.47 mmol, 0.94 equiv.) was added in small portions at
room temperature and the mixture was stirred for
10 min. The reaction mixture was concentrated in vacuo
and the resulting residue was subjected to column chro-
matograph on silica gel using a mixture of hexane–dichlo-
romethane (10:1) as an eluent to give (ꢀ)-5aA. Colorless
prisms (174 mg, 72%), m.p. 139–142 ꢁC (from ethanol–
(#19), a = 8.1695(17), b = 16.261(4), c = 17.989(4) A, V =
3
2389.8(9) A , Z = 4, Dcalc = 1.429 g cmꢀ3, T = ꢀ100 ꢁC,
˚
14071 reflections measured, refinement based on 2709
reflections, F000 = 1040, goodness-of-fit = 1.120, number
of parameters = 282, R = 0.0210 [I > 2.00r(I), 2h < 56.78],
Rw = 0.0587. Data were collected on a Bruker Smart 1000
CCD diffractometer with graphite monochromated Mo
˚
Ka radiation (k = 0.71069 A). The structure was solved by
direct methods (SIR 97) [17] and expanded using Fourier
techniques (DIRDIF-94) [18]. The structure was refined by
the full-matrix least-squares refinement. The non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were
included but not refined. All calculations were performed
using the TEXSAN crystallographic software package of
Molecular Structure Corporation [19]. Selected bond dis-
tances and angles are given in Table 1.
24
dichloromethane), ½aꢁD ¼ ꢀ14:8ꢂ (c 1.0, chloroform).
1
The H NMR spectrum of (ꢀ)-5aA was superimposable
to that of ( )-5a.
4.4.2. Sb(S)-(+)-4,4-dimethyl-2-{2-[(1-naphthyl)-
(4-tolyl)stibano]phenyl}-1,3-oxazoline (5aB)
Prepared according to the procedure described above
from palladium complex 7aB (713 mg, 0.83 mmol) and
1,2-bis(dimethylphosphino)ethane (283 mg, 0.71 mmol,
0.86 equiv.). The crude product was purified by column
chromatograph on silica gel using a mixture of hexane–
dichloromethane (10:1) as an eluent to give (+)-5aB. Color-
less prisms (327 mg, 90%), m.p. 139–141 ꢁC (from ethanol–
4.5.2. Crystal date for Sb(R),C(S)-7bB
Crystal dimensions 0.38 · 0.12 · 0.10 mm; C39H39ClN-
OPdSb Æ C6H6, Mr = 879.42; orthorhombic space group
˚
P212121, a = 14.080(3), b = 16.036(3), c = 18.171(4) A,
3
V = 4103.0(15) A , Z = 4, Dcalc = 1.424 g cmꢀ3
,
T =
˚
ꢀ173 ꢁC, 29045 reflections measured, refinement based
on 9272 reflections, F000 = 1776, goodness-of-fit = 0.999,
number of parameters = 7659, R = 0.039 [I > 2.00r(I)],
Rw = 0.086. The data were measured using a Bruker Smart
CCD diffractometer, using Mo Ka graphite monochro-
24
dichloromethane), ½aꢁD ¼ þ14:3ꢂ (c 1.0, chloroform). The
1H NMR spectrum of (+)-5aB was superimposable to that
of ( )-5a.
˚
4.4.3. Sb(R)-(ꢀ)-(2-methoxymethylphenyl)(1-naphthyl)-
(p-tolyl)stibane (5bA)
mated radiation (k = 0.71073 A). The structure was solved
by direct methods using the program SHELXS-97 [20]. The
refinement and all further calculations were carried out using
SHELXL-97 [20]. The hydrogen atoms were included in calcu-
lated positions and treated as riding atoms using the SHELXL
default parameters. The non-hydrogen atoms were refined
anisotropically, using weighted full-matrix least-square.
Selected bond distances and angles are given in Table 2.
To a solution of the diastereomerically pure palladium
complex 7bA (799 mg, 1.0 mmol) in dichloromethane
(10 mL), solids of triphenylphosphine (288 mg, 1.1 mmol,
1.1 equiv.) was added in small portions at room temper-
ature and the mixture was stirred for 10 min. The reac-
tion mixture was concentrated in vacuo and the
resulting residue was subjected to column chromatograph
on silica gel using a mixture of hexane–dichloromethane
(4:1) as an eluent to give (ꢀ)-5bA. Colorless oil (427 mg,
5. Supplementary material
24
93%), ½aꢁD ¼ ꢀ9:0ꢂ (c 2.48, chloroform). The 1H NMR
Crystallographic data for the structural analysis of 5aB
and 7bB have been deposited with the Cambridge Crystallo-
graphic Data Center, CCDC No. 291152 for Sb(S)-(+)-5aB
and No. 291153 for Sb(S),C(S)-7bB. Copies of this informa-
tion may be obtained from The Director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK, fax: +44 1233 336 033;
deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk.
spectrum of (ꢀ)-5bA was superimposable to that of
( )-5b.
4.4.4. Sb(S)-(+)-(2-methoxymethylphenyl)-
(1-naphthyl)(p-tolyl)stibane (5bB)
Prepared according to the procedure described above
from palladium complex 7bB (799 mg, 1.0 mmol) and tri-
phenylphosphine (288 mg, 1.1 mmol, 1.1 equiv.). The crude
product was purified by column chromatograph on silica
gel using a mixture of hexane–dichloromethane (4:1) as
an eluent to give (+)-5bB. Colorless oil (437 mg, 95%),
Acknowledgments
Partial financial support for this work was provided by a
Grant-in Aid for Scientific Research (C) (J.K.) and Grant-
in Aid for Encouragement of Young Scientists from the Ja-
pan Society for the Promotion Science (JSPS), and Takeda
24
1
½aꢁD ¼ þ8:7ꢂ (c 2.5, chloroform). The H NMR spectrum
of (+)-5bB was superimposable to that of ( )-5b.

2220
S. Yasuike et al. / Journal of Organometallic Chemistry 691 (2006) 2213–2220
[11] (a) P. Sharma, D. Castillo, N. Rosas, A. Cabrera, E. Gomez, A.
Scientific Foundation (S.Y.). This work supported was also
provided by the ‘‘Academic Frontier’’ Project for Private
Universities from the Ministry of Education, Culture,
Sports, Science and Technology of Japan, 2005–2009
(S.Y.). Financial support was also provided by the Special
Research Fund from Hokuriku University.
´
Toscano, F. Lara, S. Hernandez, G. Espinosa, J. Organomet. Chem.
689 (2004) 2593;
(b) L.M. Opris, A. Silvestru, C. Silvestru, H.J. Breunig, E. Lork,
Dalton Trans. (2003) 4367;
(c) H.J. Breunig, I. Ghesner, M.E. Ghesner, E. Lork, Inorg. Chem.
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(d) C.J. Carmalt, A.H. Cowley, R.D. Culp, R.A. Jones, S. Kamepalli,
N.C. Norman, Inorg. Chem. 36 (1997) 2770;
(e) C.J. Carmalt, D. Waslsh, A.H. Cowley, R.D. Culp, N.C. Norman,
Organometallics 16 (1997) 3597;
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