Metal effects on the asymmetric synthesis of a new heterobidentate As/P=S ligand

Article abstract of DOI:10.1002/ejic.200901203

The cycloaddition reaction between. 3,4-dimethyl-l-phen-ylarsole and diphenylvinylphosphane sulfide was promoted by chiral palladium and platinum complexes containing oriho-metalated (S)-[l-(dimethylamino)ethyl]naphthalene. They exhibited similar stereose

Full text of DOI:10.1002/ejic.200901203

FULL PAPER
DOI: 10.1002/ejic.200901203
Metal Effects on the Asymmetric Synthesis of a New Heterobidentate As/P=S
Ligand
Mengtao Ma,[a] Sumod A. Pullarkat,[a] Yongxin Li,[a] and Pak-Hing Leung*[a]
Keywords: As ligands / P ligands / S ligands / Palladium / Platinum / Asymmetric synthesis / Cycloaddition
The cycloaddition reaction between 3,4-dimethyl-1-phen-
ylarsole and diphenylvinylphosphane sulfide was promoted
by chiral palladium and platinum complexes containing
ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene.
They exhibited similar stereoselectivity; the palladium cy-
cloadducts could not be separated via column chromatog-
raphy and fractional crystallization, however, the corre-
sponding platinum complexes could be successfully con-
verted into their enantiomerically pure counterpart. A formal
arsanylidene elimination reaction was observed on the liber-
ated free As/P=S bidentate ligand.
of such chiral systems incorporating As and P moieties with
a view to understanding the subtle but significant variations
in the chemistry of arsenic (vs. phosphorus) exhibited in
such reaction scenarios.[13–18]
Introduction
Heterobidentate ligands have very important applica-
tions in transition metal-catalyzed asymmetric reactions
due to the fact that they contain both substitutionally labile
and substitutionally inert groups in the same molecule.[1–5]
These heterobidentate ligands containing one soft and one
hard donor atom often offer some unique advantages over
traditional symmetrical bidentate ligands in potential appli-
cations such as catalysis using transition metals. In such
scenarios their hemilabile nature readily vacates a coordina-
tion position thus allowing the incoming reactant to bind
on the metal and thus be activated during the catalytic cy-
cle. Amongst such ligands, phosphorus–sulfur-based li-
gands make up a popular class of heterobidentate ligands
and have been successfully applied in many asymmetric re-
actions.[6–8] For example recently Faller et al. reported the
enantioselective allylic alkylation and amination of acyclic
carbonates catalyzed by the axially chiral (S)-BINAP(S) li-
gand with up to 97% ee and 99% conversion.[9–12]
However, compared to the relatively extensive applica-
tion of phosphorus–sulfur-based heterobidentate ligands in
many fields, reports on such ligands incorporating inert ar-
senic and labile sulfur centers, especially those that are op-
tically pure, are very rare. Herein we report the successful
resolution of a new chiral As/P=S heterobidentate ligand
via the asymmetric cycloaddition reaction between 3,4-di-
methyl-1-phenylarsole (DMPA) and diphenylvinylphos-
phane sulfide promoted by a chiral platinum complex. This
work is part of our ongoing exploration into the chemistry
Results and Discussion
Asymmetric Diels–Alder Reaction between DMPA and
Diphenylvinylphosphane Sulfide Promoted by a Chiral
Palladium Complex
Our group has successfully employed a series of cyclo-
metallated complexes, mainly based on benzyl and naph-
thylamine systems, as efficient promoters and chiral auxilia-
ries for a wide variety of asymmetric synthetic protocols.[19]
In the present study a palladium complex containing an
ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene
auxiliary was allowed to coordinate to DMPA thus yielding
the complex (+)-1. Subsequently the complex (+)-1 was
treated with aqueous silver perchlorate in dichloromethane,
the resulting perchlorate complex could be used directly for
subsequent reaction with diphenylvinylphosphane sulfide
without isolation. The reaction was monitored by 31P{1H}
NMR spectroscopy. When the reaction mixture was stirred
for 13 d at 40 °C, the 31P{1H} NMR spectrum of the crude
reaction mixture in CDCl3 exhibited two singlets at δ 50.2
and 51.5 ppm in the ratio of 1:2 (Scheme 1). Attempts to
isolate the two diastereomers (Sc,SAs)- and (Sc,RAs)-2 via
column chromatography or fractional crystallization, how-
ever, were not successful.
In order to confirm the identities of the two dia-
stereomers, the chiral naphthylamine auxiliary in the dia-
stereomeric mixture was removed chemoselectively from
(Sc,SAs)- and (Sc,RAs)-2 by stirring a dichloromethane solu-
tion of the complexes with concentrated hydrochloric acid
[a] Division of Chemistry and Biological Chemistry, School of
Physical and Mathematical Sciences, Nanyang Technological
University,
Singapore 637371, Singapore
Fax: +65-63166984
E-mail: pakhing@ntu.edu.sg
Eur. J. Inorg. Chem. 2010, 1865–1871
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1865

M. Ma, S. A. Pullarkat, Y. Li, P.-H. Leung
FULL PAPER
Scheme 1.
for 10 min at room temperature. The 31P{1H} NMR spec- cloadduct had formed exclusively via the exo-cycloaddition
trum of the crude neutral dichloro complex 3 in CDCl3 reaction pathway. The geometry at the palladium is dis-
showed only one singlet at δ 50.7 ppm. Brown-yellow crys- torted square planar with angles at palladium in the range
tals suitable for single-crystal X-ray diffraction analysis of 83.7(1)–95.9(1) and 172.6(1)–179.4(1)°. The bond angle
were obtained from acetonitrile in 70% yield. However, the at the bridgehead arsenic (C12–As1–C7) is 77.1(3)°, which
X-ray structural analysis of dichloro complex 3 revealed the is indicative of higher strain usually seen in such norborn-
presence of both enantiomers in the unit cell. The molecu- ene chelates.
lar structure of complex 3 is shown in Figure 1 and is taken
as the representative molecule in order to study the coordi-
Arsinidene–Elimination Reaction
nation aspects for the cycloadducts which were formed as a
racemic mixture. Selected bond lengths and angles are listed
in the caption of Figure 1. The cycloadduct coordinated to
the palladium center as a bidentate ligand via arsenic and
sulfur donor atoms. It also confirmed that the desired cy-
In order to better understand the influence of the trans
ligand in determining the stability of the As bridgehead as
seen from our previous studies, the dichloro complex 3 was
treated with potassium bromide for 10 min at room tem-
perature and the dibromo complex 4 was obtained as a yel-
low solid in 96% yield (Scheme 2). The 31P{1H} NMR
spectrum exhibited only one singlet at δ 51.4 ppm indicating
the absence of any side reaction. Complex 4 was sub-
sequently recrystallized with dichloromethane/acetonitrile
to give the product as orange yellow crystals (Figure 2). The
structural analysis of dibromo complex 4 reveals the pres-
ence of both enantiomers in the unit cell which is similar to
the analogous dichloro complex 3.
Scheme 2.
The dichloro complex 3 is stable in the solid state, but it
decomposes completely after 3 weeks in CD2Cl2 at room
temperature. However, contrastingly the dibromo complex
4 is stable both in the solid state and in solution. This could
be proven by its 31P{1H} NMR spectrum in CD2Cl2 where
the chemical shift remained unchanged even after the sam-
ple was kept in solution for more than two months. But
when complex 4 was treated with potassium cyanide for
Figure 1. Molecular structure of dichloro complex 3. Selected bond
lengths [Å] and angles [°]: Pd1–S1 2.301(2), Pd1–As1 2.305(1),
Pd1–Cl1 2.323(2), Pd1–Cl2 2.389(2), As1–C7 1.976(7), As1–C12
1.961(8), S1–Pd1–As1 89.0(1), S1–Pd1–Cl1 172.6(1), As1–Pd1–Cl1
83.7(1), S1–Pd1–Cl2 91.4(1), As1–Pd1–Cl2 179.4(1), Cl1–Pd1–Cl2
95.9(1), C12–As1–C7 77.1(3).
1866
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 1865–1871

Asymmetric Synthesis of a New Bidentate As/P=S Ligand
produce the yellow crystals of the optically pure (–)-8 in
83% yield, [α]D = –57.7 (c = 0.3, CH2Cl2). The unreacted
(Sc,RAs)-7 was then readily isolated from the mother liquid
by column chromatography. Because of the fact that the
dichloro complex (–)-8 crystallized very slowly (several
weeks), for separation purposes it was more efficient to
treat the resultant mixture at the onset with NaI for 10 min
at room temperature. The resulting diiodo complex (–)-9
and (Sc,RAs)-10 were separated more easily and faster via
column chromatography (a few hours).
Figure 2. Molecular structure of dibromo complex 4. Selected bond
lengths [Å] and angles [°]: Pd1–S1 2.312(1), Pd1–As1 2.315(1),
Pd1–Br1 2.441(1), Pd1–Br2 2.510(1), As1–C7 1.986(2), As1–C12
1.969(2), S1–Pd1–As1 89.4(1), S1–Pd1–Br1 172.5(1), As1–Pd1–Br1
83.1(1), S1–Pd1–Br2 92.1(1), As1–Pd1–Br2 178.4(1), Br1–Pd1–Br2
95.4(1), C12–As1–C7 77.3(1).
3 min at room temperature, the solution rapidly changed
from red to colorless. The uncoordinated ligand is very un-
stable and the arsanylidene elimination reaction occurred
instantly to give the new compound 5 and phenylarsonic
acid as seen in our previous studies.[14] The organic com-
pound 5 could be isolated and purified by column
chromatography on a silica column with dichloromethane/
n-hexane. It is also not very stable and changed to numer-
ous unknown compounds after being kept for one week
even in the solid state.
Metal Effects: Asymmetric Diels–Alder Reaction between
DMPA and Diphenylvinylphosphane Sulfide Promoted by
the Analogous Platinum Complex
Similar to the analogous palladium complex, upon re-
moval of the chloro ligand in (+)-6 with AgClO4, the re-
sulting perchlorate complex was treated with diphenylvi-
nylphosphane sulfide for 5 d at room temperature
(Scheme 3). Two diastereomers (Sc,SAs)-7 and (Sc,RAs)-7
were obtained in much shorter reaction time in the ratio of
1:2 (as indicated by two singlets at δ 49.6 and 47.7 ppm,
Scheme 3.
The X-ray analysis of dichloro platinum complex (–)-8
respectively, in the 31P(1H) NMR spectrum). Unfortunately showed that it indeed was chiral [Flack parameter:
these diastereomeric cycloadducts also could not be sepa- –0.001(4)]. Selected bond lengths and angles are listed in
rated by column chromatography or fractional crystalli- the caption of Figure 3. The geometry at the platinum in
zation. However, when they were treated with concentrated (–)-8 is distorted square planar with angles at the platinum
hydrochloric acid for 20 min at room temperature, the in the range of 88.2(1)–92.2(1) and 176.0(1)–176.4(1)°. The
minor isomer (Sc,SAs)-7 was converted into the correspond- cycloadduct coordinated to the platinum center as a biden-
ing neutral dichloro platinum complex (–)-8, while the tate ligand via arsenic and sulfur donor atoms. The As–Pt–
major isomer (Sc,RAs)-7 remained unchanged. The mixture S bond angle [89.4(1)°] in complex (–)-8 is the same as the
was recrystallized with dichloromethane/diethyl ether to As–Pd–S bond angle of complex 4 and a little bigger than
Eur. J. Inorg. Chem. 2010, 1865–1871
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1867

M. Ma, S. A. Pullarkat, Y. Li, P.-H. Leung
FULL PAPER
that of complex 3 [89.0(1)°], however, the Cl1–Pt–Cl2 bond distorted square planar with angles at the platinum in the
angle [92.2(1)°] in complex (–)-8 is smaller than similar range of 80.0(2)–93.8(2) and 172.6(2)–173.4(1)°. The cy-
bond angles in complexes 3 and 4 [95.9(1) and 95.4(1)°, cloadduct coordinated to the platinum center as an As/P=S
respectively]. Complex (Sc,RAs)-10 could be recrystallized bidentate ligand where the sulfur is trans to the carbon and
with dichloromethane/diethyl ether to produce yellow crys- arsenic is trans to the nitrogen.
tals. As expected, the structural analysis of (Sc,RAs)-10 also
The enantiomer of (–)-8, dichloro complex (+)-8, could
revealed that the perchlorate was replaced by an iodide. Se- be obtained by treatment of optically active (Sc,RAs)-7 or
lected bond lengths and angles are listed in the caption of (Sc,RAs)-10 with concentrated hydrochloric acid for 4 h at
Figure 4. The geometry at the platinum in (Sc,RAs)-10 is room temperature (Scheme 4). Further treatment of enan-
tiomerically pure diiodo complex (–)-9 with aqueous potas-
sium cyanide liberated the desired optically pure As/P=S
ligand (+)-11 in quantitative yield, [α]D = +44.3 (c = 0.43,
CH2Cl2). The liberated ligand was unstable and readily pro-
duced the optically active compound (+)-5, [α]D = +60.7 (c
= 0.40, CH2Cl2) (Scheme 5).
Scheme 4.
Figure 3. Molecular structure of dichloro complex (–)-8. Selected
bond lengths [Å] and angles [°]: Pt1–S1 2.301(1), Pt1–As1 2.312(1),
Pt1–Cl1 2.329(1), Pt1–Cl2 2.355(1), As1–C7 1.967(3), As1–C12
1.968(3), S1–Pt1–Cl1 176.4(1), S1–Pt1–As1 89.4(1), Cl1–Pt1–As1
88.2(1), S1–Pt1–Cl2 90.4(1), Cl1–Pt1–Cl2 92.2(1), As1–Pt1–Cl2
176.0(1), C7–As1–C12 77.8(1).
Scheme 5.
Figure 4. Molecular structure of complex (Sc,RAs)-10. Selected bond lengths [Å] and angles [°]: Pt1–C1 2.024(7), Pt1–N1 2.136(5), Pt1–
As1 2.321(1), Pt1–S1 2.406(2), As1–C29 1.964(6), As1–C34 1.980(6), C1–Pt1–N1 80.0(2), C1–Pt1–As1 93.8(2), N1–Pt1–As1 173.4(1),
C1–Pt1–S1 172.6(2), N1–Pt1–S1 93.7(1), As1–Pt1–S1 92.6(1), C29–As1–C34 77.1(3).
1868
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 1865–1871

Asymmetric Synthesis of a New Bidentate As/P=S Ligand
were removed and the residue was extracted with dichloromethane
and water and the organic layer was dried with MgSO4. Removal
of the solvent gave 4 as a solid, which was then recrystallized from
dichloromethane/acetonitrile to give the product as orange yellow
crystals (0.075 g, 96%); m.p. 131–132 °C. C28H29AsBr2NPPdS
(783.69): calcd. C 42.9, H 3.7, N 1.8, S 4.1; found C 42.7, H 3.4,
N 1.7, S 4.3. 31P{1H} NMR (CD2Cl2): δ = 51.4 ppm. 1H NMR
(CD2Cl2): δ = 1.59 (s, 3 H, =CCH3), 1.67 (s, 3 H, =CCH3), 2.12
Conclusions
The cycloaddition reaction between DMPA and di-
phenylvinylphosphane sulfide was promoted by a chiral
palladium complex, however, both the resulting dia-
stereomers 2 and the corresponding dihalogen complexes 3
and 4 could not be separated into their enantiomeric coun-
terparts via column chromatography or fractional crystalli-
zation. When the chiral metal promoter was changed from
palladium to platinum, the reaction selectivity is similar al-
though the rate improved drastically. However, the major
isomer (Sc,RAs)-7 and the dichloro complex (–)-8 could be
separated via fractional crystallization and column
chromatography. Alternatively they could be converted into
the corresponding iodo complexes (Sc,RAs)-9 and (–)-10.
The two iodo complexes were readily separated by means
of column chromatography. The optically pure As/P=S li-
gand (+)-11 could be liberated by treatment of (–)-9 with
KCN. The arsanylidene elimination reaction was observed
on the racemic or chiral free ligand 9.
3
2
(dd, JHH = 11.0, JPH = 25.8 Hz, 1 H, PCH), 2.85 (m, 1 H,
3
CHCH2), 3.39 (d, JHH = 4.8 Hz, 1 H, AsCH), 3.41 (m, 1 H,
CHCH2), 3.55 (s, 1 H, AsCH), 7.43–8.28 (m, 15 H, arom.) ppm.
Preparation of Compound 5: Dibromo complex
4 (0.16 g,
0.22 mmol) in dichloromethane (30 mL) was treated with potas-
sium cyanide (0.2 g) in water (30 mL) for 3 min at room tempera-
ture in air. The solution changed from red to colorless. The organic
layer was washed with water (3ϫ30 mL), dried (MgSO4), and the
solvent was removed. The residue was purified by column
chromatography with dichloromethane to give compound 5 as a
white solid (0.06 g, 84%); m.p. 94–95 °C. 31P{1H} NMR (CDCl3):
1
δ = 49.0 ppm. H NMR (CDCl3): δ = 1.54 (s, 3 H, =CCH3), 1.70
3
3
(s, 3 H, =CCH3), 2.15 (m, 1 H, PCH), 2.78 (dd, JHH = 16.2, JPH
3
3
= 32.3 Hz, 1 H, CHCH2), 3.58 (dd, JHH = 10.0, JPH = 15.2 Hz,
1 H, CHCH2), 5.37 (s, 1 H, =CH), 5.39 (s, 1 H, =CH), 7.42–7.95
(m, 10 H, arom.) ppm. 13C NMR (CDCl3): δ = 19.0 (CH3), 19.9
(d, 4JPC = 7.3 Hz, CH3), 22.6 (d, 2JPC = 6.7 Hz, CH2), 37.1 (d, 1JPC
Experimental Section
3
2
= 220.7 Hz, PCH), 116.1 (d, JPC = 20.4 Hz, =CH), 120.6 (d, JPC
= 53.7 Hz, =CH), 128.0, 128.1, 128.4, 128.6, 129.9, 130.9, 131.1,
131.19, 131.2, 131.3, 131.4, 131.9, 132.3, 132.4, 132.9 (arom.), 133.4
General Methods: Reactions involving air-sensitive compounds
were performed under inert argon using standard Schlenk tech-
niques. Solvents were dried and freshly distilled according to stan-
dard procedures and degassed prior to use when necessary. NMR
spectra were recorded at 25 °C on Bruker Avance 300, 400, and 500
spectrometers. Optical rotations were measured on the specified
solution in a 0.1 dm cell at 20 °C with a Perkin–Elmer 341 polari-
meter. Elemental analysis was performed by the Elemental Analysis
Laboratory of the Division of Chemistry and Biological Chemistry
at Nanyang Technological University. Melting points were mea-
sured with a Stanford Research Systems OptiMelt MPA 100 instru-
ment and are uncorrected. Diphenylvinylphosphane sulfide,[20] (+)-
1[15] and (+)-6[16] were prepared following literature procedures.
4
3
(d, JPC
= 14.8 Hz, =CCH3), 137.8 (d, JPC = 47.5 Hz,
=CCH3) ppm. EI-MS: m/z (%)= 325.1 [M]+.
Preparation of Complexes (Sc,RAs)-7, (–)-8, (–)-9, and (Sc,RAs)-10:
solution of (+)-6 (0.26 g, 0.39 mmol) in dichloromethane
A
(30 mL) was stirred for 2 h in the presence of a solution of silver
perchlorate (0.15 g) in water (1 mL). The organic layer, after the
removal of AgCl, was then washed with water (3ϫ30 mL), dried
(MgSO4), and subsequently treated with diphenylvinylphosphane
sulfide (0.10 g, 0.39 mmol) for 5 d at room temperature. The crude
diastereomeric mixture was treated with excess concentrated hydro-
chloric acid (2 mL) for 20 min at room temperature.
Caution! Perchlorate salts of metal complexes are potentially explos-
ive compounds and should be handled with care.
Method A: The mixture was washed with water (3ϫ30 mL), dried
(MgSO4), and subsequently recrystallized from dichloromethane/
diethyl ether to give (–)-8 as pale yellow crystals (0.08 g, 83%).
[α]D = –57.7 (c = 0.3, CH2Cl2); m.p. Ͼ300 °C. C26H26AsCl2PPtS
(742.43): calcd. C 42.1, H 3.5, S 4.3; found C 42.2, H 3.9, S 4.1.
Preparation of Dichloro Complex 3: A solution of (+)-1 (0.47 g,
0.82 mmol) in dichloromethane (50 mL) was stirred for 2 h in the
presence of a solution of silver perchlorate (1.0 g) in water (1 mL).
The organic layer, after the removal of AgCl, was then washed with
water (3ϫ50 mL), dried (MgSO4), and subsequently treated with
diphenylvinylphosphane sulfide (0.20 g, 0.82 mmol) for 13 d at
40 °C. The crude diastereomeric mixture was treated with excess
concentrated hydrochloric acid (2 mL) for 10 min at room tempera-
ture. The mixture was then washed with water (3ϫ50 mL), dried
(MgSO4), and subsequently recrystallized from acetonitrile to give
3 as brown yellow crystals (0.40 g, 70%); m.p. 126–127 °C.
C26H26AsCl2PPdS (653.77): calcd. C 48.4, H 4.2, N 2.0, S 4.6;
found C 48.0, H 3.9, N 1.7, S 4.5. 31P{1H} NMR (CD2Cl2): δ =
1
31P{1H} NMR (CD2Cl2): δ = 43.9 (s, JPtP = 147 Hz, 1 P) ppm. H
NMR (CD2Cl2): δ = 1.46 (s, 3 H, =CCH3), 1.59 (s, 3 H, =CCH3),
3
3
1.92 (dd, JHH = 1.5, JHH = 12.2 Hz, 1 H, CHCH2), 2.94 (m, 1
3
H, PCH), 3.16 (d, JHH = 10.6 Hz, 1 H, CHCH2), 3.38 (s, 1 H,
AsCH), 3.42 (d, JHH = 5.2 Hz, 1 H, AsCH), 7.32–8.18 (m, 15 H,
3
arom.) ppm.
The solvents from the remaining solution were removed and the
residue was isolated by column chromatography with dichloro-
methane/diethyl ether as elute to give (Sc,RAs)-7 as a yellow solid
(0.18 g, 71%). [α]D = +196.4 (c = 0.3, CH2Cl2); m.p. 160–161 °C.
C40H42AsClNO4PPtS (969.26): calcd. C 49.6, H 4.4, N 1.5, S 3.3;
found C 49.4, H 4.6, N 1.4, S 3.4. 31P{1H} NMR (CDCl3): δ =
1
51.3 ppm. H NMR (CD2Cl2): δ = 1.63 (s, 3 H, =CCH3), 1.64 (s,
3
2
3 H, =CCH3), 2.15 (dd, JHH = 10.6, JPH = 25.4 Hz, 1 H, PCH),
2.95 (m, 1 H, CHCH2), 3.40 (d, JHH = 5.0 Hz, 1 H, AsCH), 3.45
(m, 1 H, CHCH2), 3.55 (s, 1 H, AsCH), 7.42–8.29 (m, 15 H,
arom.) ppm.
3
1
47.7 (s, JPtP = 63 Hz, 1 P) ppm. H NMR (CDCl3): δ = 1.61 (s, 3
3
H, =CCH3), 1.86 (d, JHH = 6.2 Hz, 3 H, CHCH3), 2.00 (s, 3 H,
Preparation of Dibromo Complex 4: The solution of 3 (0.07 g,
0.10 mmol) in dichloromethane (50 mL) was treated with excess
=CCH3), 2.63 (m, 1 H, CHCH2), 2.71 (s, 3 H, NCH3), 2.84 (m, 1
H, CHCH2), 3.20 (d, JHH = 6.5 Hz, 1 H, AsCH), 3.37 (s, 3 H,
3
potassium bromide (0.20 g) in acetone (50 mL) and water (10 mL) NCH3), 3.70 (s, 1 H, AsCH), 3.86 (broad s, 1 H, PCH), 4.65 (q,
and stirred vigorously for 10 min at room temperature. The solvents
3JHH = 6.2 Hz, 1 H, CHCH3), 6.61–7.97 (m, 21 H, arom.) ppm.
Eur. J. Inorg. Chem. 2010, 1865–1871
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1869

M. Ma, S. A. Pullarkat, Y. Li, P.-H. Leung
FULL PAPER
Table 1. Crystallographic data for complexes 3, 4, (–)-8, and (Sc,RAs)-10.
3
4
(–)-8
(Sc,RAs)-10
Formula
Fw
Space group
Crystal system
a [Å]
b [Å]
c [Å]
C28H29AsCl2NPPdS
694.77
P21/n
monoclinic
12.5118(9)
18.4493(14)
13.1877(9)
90
C28H29AsBr2NPPdS
783.69
P21/n
monoclinic
12.4925(5)
18.7724(8)
13.3221(6)
90
C26H26AsCl2PPtS
742.41
C40H42AsINPPtS
996.69
P212121
orthorhombic
9.4457(2)
12.4631(3)
21.4517(5)
90
P212121
orthorhombic
13.4708(3)
16.2313(4)
17.7194(4)
90
α [°]
β [°]
110.221(4)
90
2856.5(4)
4
109.532(2)
90
2944.4(2)
4
90
90
90
90
γ [°]
V [Å3]
2525.35(10)
4
3874.32(16)
4
Z
T [K]
173(2)
1.616
0.71073
2.134
1392
0.0619
0.1546
–
173(2)
1.768
0.71073
4.603
1536
0.0238
0.0505
–
173(2)
1.953
0.71073
7.228
1432
0.0232
0.0454
–0.001(4)
173(2)
1.709
0.71073
5.389
1936
0.0305
0.0706
–0.003(6)
Dcalcd. [gcm–3]
λ [Å]
µ [mm]–1
F(000)
R1 [obsd. data][a]
wR2 [obsd. data][b]
Flack parameter
[a] R1 = Σ||Fo| – |Fc||/Σ|Fo|. [b] wR2 = √{Σ[w(Fo – Fc ) ]/Σ[w(Fo2)2]}, w–1 = σ2(Fo)2 + (aP)2 + bP.
2
2 2
Method B: The mixture was washed with water (3ϫ30 mL), excess free ligand (+)-11 was obtained as an air-sensitive solid in quantita-
sodium iodide (0.2 g) in acetone (20 mL) was added and stirred for
10 min at room temperature. The solvents were removed and the
diiodo complex (–)-9 and (Sc,RAs)-10 were easily isolated by col-
umn chromatography with dichloromethane/diethyl ether as elute.
Complex (–)-9 was recrystallized with dichloromethane/diethyl
ether to produce yellow crystals (0.09 g, 75%). [α]D = –48.8 (c =
0.1, CH2Cl2); m.p. 186–187 °C. C26H26AsI2PPtS (925.33): calcd. C
33.8, H 2.8, S 3.5; found C 34.0, H 2.9, S 3.3. 31P{1H} NMR
(CD2Cl2): δ = 44.4 (s, JPtP = 132 Hz, 1 P) ppm. 1H NMR (CD2Cl2):
tive yield. [α]D = +44.3 (c = 0.43, CH2Cl2). 31P{1H} NMR (CDCl3):
δ = 48.0 ppm.
X-ray Crystal Structure Determination: Crystallographic data for
complexes 3, 4, (–)-8, and (Sc,RAs)-10 are given in Table 1. Diffrac-
tion data were collected with a Bruker X8 CCD diffractometer with
Mo-Kα radiation (graphite monochromator). SADABS absorption
corrections were applied. All non-hydrogen atoms were refined an-
isotropically, while the hydrogen atoms were introduced at calcu-
lated positions and refined riding on their carrier atoms. The abso-
lute configuration of the chiral complex was determined unambigu-
ously by using the Flack parameter.
5
δ = 1.57 (d, JHH = 0.8 Hz, 3 H, =CCH3), 1.75 (s, 3 H, =CCH3),
3
2
1.97 (dt, JHH = 11.9, JPH = 12.1 Hz, 1 H, PCH), 2.83 (m, 1 H,
CHCH2), 3.28 (m, 1 H, CHCH2), 3.46 (s, 1 H, AsCH), 3.47 (d,
3JHH = 5.2 Hz, 1 H, AsCH), 7.42–8.27 (m, 15 H, arom.) ppm.
Complex (Sc,RAs)-10 was recrystallized with dichloromethane/di-
ethyl ether to produce yellow crystals (0.19 g, 73%). [α]D = +171.4
(c = 0.35, CH2Cl2); m.p. 180–181 °C. C40H42AsINPPtS (996.71):
calcd. C 48.2, H 4.3, N 1.4, S 3.2; found C 48.4, H 4.1, N 1.2, S
CCDC-757121 (for 3), -757122 (for 4), -757123 [for (–)-8],
and -757120 [for (Sc,RAs)-10] contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
1
3.4. 31P{1H} NMR (CDCl3): δ = 47.2 ppm. H NMR (CDCl3): δ
3
= 1.65 (s, 3 H, =CCH3), 1.87 (d, JHH = 6.1 Hz, 3 H, CHCH3),
Acknowledgments
2.04 (s, 3 H, =CCH3), 2.73 (s, 3 H, NCH3), 2.78 (m, 1 H, CHCH2),
2.89 (q, 3JHH = 2JPH = 11.5 Hz, 1 H, PCH), 3.19 (d, 3JPH = 6.4 Hz,
1 H, AsCH), 3.39 (s, 3 H, NCH3), 3.70 (s, 1 H, AsCH), 4.60 (broad
We thank Nanyang Technological University for support of this
research and for a scholarship to M. M.
3
s, 1 H, CHCH2), 4.68 (q, JHH = 6.2 Hz, 1 H, CHCH3), 7.10–8.41
(m, 21 H, arom.) ppm.
[1] J. C. Jeffrey, T. B. Rauchfuss, Inorg. Chem. 1979, 18, 2658–
2666.
[2] A. Bader, E. Lindner, Coord. Chem. Rev. 1991, 108, 27–110.
[3] C. S. Slone, D. A. Weinberger, C. A. Mirkin, Prog. Inorg. Chem.
1999, 48, 233–350.
[4] P. Braunstein, F. Naud, Angew. Chem. Int. Ed. 2001, 40, 680–
699.
[5] V. V. Grushin, Chem. Rev. 2004, 104, 1629–1662.
[6] D. A. Evans, K. R. Campos, J. S. Tedrow, F. E. Michael, M. R.
Gagne, J. Am. Chem. Soc. 2000, 122, 7905–7920.
[7] H. Y. Cheung, W. Y. Yu, F. L. Lam, T. T. L. Au-Yeung, Z.
Zhou, T. H. Chan, A. S. C. Chan, Org. Lett. 2007, 9, 4295–
4298.
Removal of Chiral Auxiliary: Synthesis of Dichloro Complex (+)-8:
The optically pure (Sc,RAs)-7 (0.14 g, 0.14 mmol) [or (Sc,RAs)-10]
was dissolved in dichloromethane (30 mL) and treated with excess
concentrated hydrochloric acid (2 mL) for 4 h at room temperature.
The solution was washed with water (3ϫ30 mL) and dried
(MgSO4). The solvent was removed and the residue was sub-
sequently recrystallized from dichloromethane/diethyl ether to give
(+)-8 as yellow crystals (0.09 g, 84%); [α]D = +80.5 (c = 0.2,
CH2Cl2). Other data were the same as complex (–)-8.
Liberation of the As/P=S Ligand (+)-11: A solution of (–)-9 (0.06 g,
0.06 mmol) in dichloromethane (10 mL) was stirred vigorously with
a saturated aqueous solution of potassium cyanide (1.0 g) for
15 min. The organic layer was separated, then washed with water
(3ϫ10 mL), and dried (MgSO4). Upon removal of the solvent, the
[8] M. Mellah, A. Voituriez, E. Schulz, Chem. Rev. 2007, 107,
5133–5209.
[9] J. W. Faller, J. C. Wilt, J. Parr, Org. Lett. 2004, 6, 1301–1304.
1870
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 1865–1871

Asymmetric Synthesis of a New Bidentate As/P=S Ligand
[10]
[11]
[12]
[16] M. Ma, S. A. Pullarkat, M. Yuan, N. Zhang, Y. Li, P. H.
Leung, Organometallics 2009, 28, 4886–4889.
[17] M. Ma, S. A. Pullarkat, K. Chen, Y. Li, P. H. Leung, J. Or-
ganomet. Chem. 2009, 694, 1929–1933.
[18] F. Liu, S. A. Pullarkat, Y. Li, S. Chen, P. H. Leung, Eur. J.
Inorg. Chem. 2009, 27, 4134–4140.
[19] P. H. Leung, Acc. Chem. Res. 2004, 37, 169–177.
[20] R. Rabinowitz, J. Pellon, J. Org. Chem. 1961, 26, 4623–4626.
Received: December 14, 2009
J. W. Faller, J. C. Wilt, Tetrahedron Lett. 2004, 45, 7613–7616.
J. W. Faller, J. C. Wilt, Organometallics 2005, 24, 5076–5083.
J. W. Faller, J. C. Wilt, Org. Lett. 2005, 7, 633–636.
[13] M. L. Bungabong, K. W. Tan, Y. Li, S. V. Selvaratnam, K. G.
Dongol, P. H. Leung, Inorg. Chem. 2007, 46, 4733–4736.
[14] M. Ma, S. A. Pullarkat, Y. Li, P. H. Leung, Inorg. Chem. 2007,
46, 9488–9494.
[15] M. Ma, S. A. Pullarkat, Y. Li, P. H. Leung, J. Organomet.
Chem. 2008, 693, 3289–3294.
Published Online: March 19, 2010
Eur. J. Inorg. Chem. 2010, 1865–1871
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1871