Synthesis of [2,6-Bis(2-oxazolinyl)phenyl]palladium complexes via the ligand introduction route

Article abstract of DOI:10.1021/om800666x

A series of [2,6-bis(2-oxazolinyl)phenyl]palladium (Phebox-Pd) complexes were synthesized via the ligand introduction route. trans-Bromo(2,6- dicarboxyphenyl)bis(triphenylphosphine)palladium was prepared by the reaction of 2-bromoisophthalic acid with Pd(PPh₃)₄ in 93% yield, and the carboxy groups of the palladium complex were convened into oxazolinyl groups to give the Phebox-Pd complexes in 44-57% yield.

Full text of DOI:10.1021/om800666x

Organometallics 2008, 27, 5159–5162
5159
Notes
Synthesis of [2,6-Bis(2-oxazolinyl)phenyl]palladium Complexes via
the Ligand Introduction Route
Tsutomu Kimura and Yasuhiro Uozumi*
Institute for Molecular Science (IMS) and CREST, Higashiyama 5-1, Myodaiji, Okazaki 444-8787, Japan
ReceiVed July 14, 2008
Scheme 1. Synthesis of Phebox-Pd Complexes via Metal
Introduction Routes
Summary: A series of [2,6-bis(2-oxazolinyl)phenyl]palladium
(Phebox-Pd) complexes were synthesized Via the ligand intro-
duction route. trans-Bromo(2,6-dicarboxyphenyl)bis(triphe-
nylphosphine)palladium was prepared by the reaction of
2-bromoisophthalic acid with Pd(PPh3)4 in 93% yield, and the
carboxy groups of the palladium complex were conVerted into
oxazolinyl groups to giVe the Phebox-Pd complexes in 44-57%
yield.
Organometallic complexes containing monoanionic terdentate
ligands, so-called pincer complexes, have received much
attention not only as catalysts in synthetic organic chemistry
but also as organometallic materials in the field of materials
science.1 In particular, the pincer palladium complexes having
2,6-bis(2-oxazolinyl)phenyl (abbreviated as Phebox) groups have
been recognized as a useful class of catalysts for asymmetric
transformations,2,3 and considerable effort has been devoted
toward their synthesis. In 1997, three independent groups
reported the syntheses of the Phebox-Pd complexes 2 (Scheme
1). Denmark et al. described the synthesis of the Phebox-Pd
complexes via the oxidative addition of 2-halo-1,3-bis(2-
oxazolinyl)benzenes to Pd2(dba)3 · 2H2O.4 Nishiyama et al.
showed that the transmetalation of i-Pr-Phebox-SnMe3 with
PdCl2(PhCN)2 gave the i-Pr-Phebox-Pd complex.5 Also, Rich-
ards et al. reported that the lithiation of 1,3-bis(2-oxazolinyl)-
benzenes with LDA/TMEDA followed by transmetalation with
PdBr2(1,5-COD) gave the Phebox-Pd complexes.6 Another
method for the synthesis of Phebox-Pd complexes is the C-H
bond activation of 1,3-bis(2-oxazolinyl)benzenes.7
All of these methods use the metal introduction route, in
which the palladium is introduced to the 1,3-bis(2-oxazolinyl)-
arenes 1 in the final step. However, these methods suffer from
several drawbacks: (1) diverse oxazolinyl groups are constructed
at an early stage, (2) an extra metalation step is necessary for
the synthesis via transmetalation,5,6,8 (3) low regioselectivity
of the direct cyclopalladation results in the formation of the
undesirable 4-palladated complex 2′,3e and (4) reactive oxazo-
lines are troublesome in the metalation step.3b,e,9
Recently, we developed a new synthetic strategy, the ligand
introduction route, in which the metal is introduced to the
aromatic ring prior to the construction of the ligand units.10 This
strategy enabled us to prepare a novel class of pincer palladium
complexes having sterically demanding and/or chemically
unstable functional groups. If the ligand introduction route can
be successfully applied to the synthesis of the Phebox-Pd
complexes, the aforementioned inherent problems would be
solved. We report here the synthesis of the Phebox-Pd com-
plexes via the ligand introduction route and X-ray molecular
structure analysis of the Phebox-Pd complexes.
* To whom correspondence should be addressed. Tel: +81-564-59-5571.
Fax: +81-564-59-5574. E-mail: uo@ims.ac.jp
(1) Reviews: (a) van der Boom, M. E.; Milstein, D. Chem. ReV. 2003,
103, 1759. (b) Singleton, J. T. Tetrahedron 2003, 59, 1837. (c) Bedford,
R. B. Chem. Commun. 2003, 1787. (d) Dupont, J.; Consorti, C. S.; Spencer,
J. Chem. ReV. 2005, 105, 2527. (e) Szabó, K. J. Synlett 2006, 811. (f)
Albrecht, M.; van Koten, G. Angew. Chem., Int. Ed. 2001, 40, 3750.
(2) Nishiyama, H. Chem. Soc. ReV. 2007, 36, 1133.
(3) (a) Bunegar, M. J.; Dyer, U. C.; Evans, G. R.; Hewitt, R. P.; Jones,
S. W.; Henderson, N.; Richards, C. J.; Sivaprasad, S.; Skead, B. M.; Stark,
M. A.; Teale, E. Org. Process Res. DeV. 1999, 3, 442. (b) Stark, M. A.;
Jones, G.; Richards, C. J. Organometallics 2000, 19, 1282. (c) Motoyama,
Y.; Kawakami, H.; Shimozono, K.; Aoki, K.; Nishiyama, H. Organome-
tallics 2002, 21, 3408. (d) Fossey, J. S.; Richards, C. J. Tetrahedron Lett.
2003, 44, 8773. (e) Fossey, J. S.; Richards, C. J. Organometallics 2004,
23, 367. (f) Takemoto, T.; Iwasa, S.; Hamada, H.; Shibatomi, K.;
Kameyama, M.; Motoyama, Y.; Nishiyama, H. Tetrahedron Lett. 2007, 48,
3397.
(4) Denmark, S. E.; Stavenger, R. A.; Faucher, A.-M.; Edwards, J. P.
J. Org. Chem. 1997, 62, 3375.
(5) Motoyama, Y.; Makihara, N.; Mikami, Y.; Aoki, K.; Nishiyama, H.
Chem. Lett. 1997, 951.
(6) Stark, M. A.; Richards, C. J. Tetrahedron Lett. 1997, 38, 5881.
(7) El Hatimi, A.; Go´mez, M.; Jansat, S.; Muller, G.; Font-Bard´ıa, M.;
Solans, X. J. Chem. Soc., Dalton Trans. 1998, 4229.
(8) Stol, M.; Snelders, D. J. M.; Kooijman, H.; Spek, A. L.; van Klink,
G. P. M.; van Koten, G. Dalton Trans. 2007, 2589.
(9) (a) Kazi, A. B.; Jones, G. D.; Vicic, D. A. Organometallics 2005,
24, 6051. (b) Bugarin, A.; Connell, B. T. Organometallics 2008, 27, 4357.
(10) (a) Takenaka, K.; Uozumi, Y. Org. Lett. 2004, 6, 1833. (b)
Takenaka, K.; Uozumi, Y. AdV. Synth. Catal. 2004, 346, 1693. (c) Takenaka,
K.; Minakawa, M.; Uozumi, Y. J. Am. Chem. Soc. 2005, 127, 12273. (d)
Kimura, T.; Uozumi, Y. Organometallics 2006, 25, 4883. (e) Minakawa,
M.; Takenaka, K.; Uozumi, Y Eur. J. Inorg. Chem. 2007, 1629.
10.1021/om800666x CCC: $40.75
2008 American Chemical Society
Publication on Web 09/11/2008

5160 Organometallics, Vol. 27, No. 19, 2008
Notes
Scheme 2. Synthetic Strategy for Phebox-Pd Complexes via
a Ligand Introduction Route
Scheme 4. Synthesis of Phebox-Pd Complexes 2
Scheme 3. Synthesis of Palladium Complex 3
As a key precursor, we designed trans-bromo(2,6-dicarbox-
yphenyl)bis(triphenylphosphine)palladium (3), in which two
carboxy groups were attached to the 2,6-positions of the benzene
ring (Scheme 2). The conversion of the carboxy groups into
the oxazolinyl groups would give the Phebox-Pd complexes 2.
The palladium complex 3 was prepared by the oxidative
addition of 2-bromoisophthalic acid (4) to Pd(PPh3)4 in 93%
yield (Scheme 3).11 The structure of the palladium complex 3
was confirmed by X-ray molecular structure analysis (Figure
1). The square-planar palladium complex 3 bears two triph-
enylphosphines, the 2,6-dicarboxyphenyl group, and the bromide
ligand, with the two triphenylphosphines located trans to each
other. The 2,6-dicarboxyphenyl group is oriented almost per-
pendicular with respect to the square plane.
With the key precursor 3 in hand, we examined the synthesis
of the Phebox-Pd complexes 2 (Scheme 4). Initially, the
palladium complex having the 2,6-bis(chlorocarbonyl)phenyl
group 5 was generated in situ from the reaction of the palladium
complex 3 with oxalyl chloride. The palladium complex 5 was
then treated with (S)-2-amino-1-propanol (6a) in the presence
of Et3N to give the (2,6-bis{N-[(S)-2-hydroxy-1-methylethyl]-
carbamoyl}phenyl)palladium complex 7. Finally, cyclization of
the N-[(S)-2-hydroxy-1-methylethyl]carbamoyl groups with me-
syl chloride in the presence of Et3N under an oxygen atmosphere
gave the desired Me-Phebox-Pd complex 2a in 54% yield along
with triphenylphosphine oxide. Similarly, the reaction of the
palladium complex 3 with a variety of ꢀ-amino alcohols 6b-f
gave the Phebox-Pd complexes bearing benzyl (2b), isopropyl
(2c), isobutyl (2d), (S)-sec-butyl (2e), and dimethyl groups (2f)
at the 4-position of the oxazoline rings in 44-57% yield. The
bromide ligand of the palladium complex 3 was replaced by
the chloride ligand during the reaction, as revealed by elemental
analysis and X-ray molecular structure analysis.
The substituents at the 4-position of the oxazoline rings in
the C2-symmetric Phebox ligands play an important role in the
asymmetric induction, and the oxazolines can supply sufficient
substituent diversity by using ꢀ-aminoalcohols. The formation
of the oxazoline rings in the final step is preferred when the
Phebox ligands are screened in the asymmetric reactions.
The structures of the Phebox-Pd complexes 2c,d,f were
determined by X-ray molecular structure analyses (Figure 2,
Table 1).12 The structural features of the Phebox-Pd complexes
2 are similar to those of the Phebox-Ni13 and Phebox-Pt
complexes.3c-e,14 The Phebox-Pd complexes 2c,d,f adopt
distorted-square-planar geometries at the palladium atom with
the two nitrogen atoms of the oxazolinyl groups, the chlorine
atom, and the carbon atom of the benzene ring. Isopropyl and
isobutyl groups attached to the oxazoline rings in the Phebox-
Pd complexes 2c,d provide the stereochemical environment
around the palladium center. The palladium-carbon bond
lengths of the pincer complexes 2 (1.934-1.940 Å) are slightly
shorter than that of the palladium complex 3 (2.026 Å) by
0.086-0.092 Å. The Cl-Pd-C1 angles of the Phebox-Pd
complexes 2 (177.3-179.1°) are almost linear, whereas the
N1-Pd-N2 angles (157.1-158.0°) are bent.
In summary, we have developed a new synthetic route for
the Phebox-Pd complexes. A variety of Phebox-Pd complexes
were successfully synthesized via the ligand introduction route,
in which the palladium-carbon bond was formed prior to the
construction of the oxazoline rings. This synthetic method is
attractive from the standpoint of a diversity-based approach,
and the yields of the complexes15 are comparable to or higher
(11) The oxidative addition of 2-bromobenzoic acid to Pd(PPh3)4 has
been reported; see: Ferna´ndez-Rivas, C.; Ca´rdenas, D. J.; Mart´ın-Matute,
´
B.; Monge, A.; Gutie´rrez-Puebla, E.; Echavarren, A. M. Organometallics
2001, 20, 2998.
(12) X-ray structural analyses of analogous pincer type Phebox-palladium
complexes have been reported.3b,c,4,5
Figure 1. (a) ORTEP drawing of the palladium complex 3 · 2DMSO
with thermal ellipsoids drawn at the 50% probability level. (b)
ORTEP drawing of 3 · 2DMSO along the Br-Pd bond. Hydrogen
atoms and DMSO are omitted for clarity. Selected bond lengths
(Å) and angles (deg): Br-Pd ) 2.5282(4), Pd-P1 ) 2.3040(7),
Pd-P2 ) 2.3507(8), Pd-C1 ) 2.026(3), C7-O1 ) 1.208(4),
C7-O2 ) 1.327(4), C8-O3 ) 1.208(4), C8-O4 ) 1.336(4),
Pd · · · O1 ) 2.953, Pd · · · O2 ) 2.871; P1-Pd-P2 ) 168.80
(3), Br-Pd-C1 ) 172.04(8).
(13) (a) Fossey, J. S.; Richards, C. J. J. Organomet. Chem. 2004, 689,
3056. (b) Stol, M.; Snelders, D. J. M.; Godbole, M. D.; Havenith, R. W. A.;
Haddleton, D.; Clarkson, G.; Lutz, M.; Spek, A. L.; van Klink, G. P. M.;
van Koten, G. Organometallics 2007, 26, 3985.
(14) (a) Motoyama, Y.; Mikami, Y.; Kawakami, H.; Aoki, K.; Nish-
iyama, H. Organometallics 1999, 18, 3584. (b) Fossey, J. S.; Jones, G.;
Motevalli, M.; Nguyen, H. V.; Richards, C. J.; Stark, M. A.; Taylor, H. V.
Tetrahedron: Asymmetry 2004, 15, 2067.
(15) Total chemical yields of 2a-f are 41-53% from the dicarboxylic
acid 4.

Notes
Organometallics, Vol. 27, No. 19, 2008 5161
(5.780 g, 5.00 mmol) in AcOEt (100 mL) was added 2-bro-
moisophthalic acid (4; 1.344 g, 5.49 mmol), and the mixture was
stirred under reflux for 24 h. The resulting colorless solid was
collected by filtration and washed with AcOEt (20 mL × 3) to
give
trans-bromo(2,6-dicarboxyphenyl)bis(triphe-
nylphosphine)palladium (3; 4.060 g, 4.635 mmol, 93%) as a
colorless solid. Mp: 213-215 °C dec. MS (ESI): m/z 874 (M+).
1H NMR (DMSO-d6): δ 6.47 (t, J ) 7.3 Hz, 1H, Ar H), 7.10 (d,
J ) 7.3 Hz, 2H, Ar H), 7.20-7.60 (m, 30H, Ar H), 12.21 (s, 2H,
CO2H). 13C NMR (DMSO-d6): δ 122.0 (Ar), 127.4 (Ar), 129.4
(Ar), 131.8 (virtual t, J ) 21.7 Hz, Ar), 133.5 (Ar), 134.5 (Ar),
135.9 (Ar), 169.3 (Ar), 170.9 (CdO). 31P NMR (DMSO-d6): δ
13.6. Anal. Calcd for C44H35BrO4P2Pd (876.02): C, 60.33; H, 4.03.
Found: C, 60.34; H, 4.09. IR (ATR mode): ν 1685 cm-1 (CdO).
Synthesis of {2,6-Bis[(4S)-4-methyl-2-oxazolinyl]phenyl}-
chloropalladium (2a). To a suspension of trans-bromo(2,6-
dicarboxyphenyl)bis(triphenylphosphine)palladium (3; 219.0 mg,
0.25 mmol) in CH2Cl2 (20 mL) was added (COCl)2 (69.7 mg, 0.55
mmol) and DMF (3.8 mg, 0.05 mmol) at 0 °C, and the mixture
was stirred at 25 °C for 6 h. After the solvent was removed, CHCl3
(10 mL) was added to the residue. To the resulting solution was
added Et3N (55.6 mg, 0.55 mmol) and (S)-2-amino-1-propanol (6a;
41.4 mg, 0.55 mmol) at 0 °C, and the mixture was stirred at 25 °C
for 12 h. The reaction mixture was poured into water (10 mL), and
the organic layer was washed with water (10 mL × 2), dried over
Na2SO4, and concentrated in vacuo. The residue was dissolved in
CHCl3 (10 mL), and to the resulting solution was added Et3N (111.2
mg, 1.10 mmol) and MsCl (126.0 mg, 1.10 mmol) at 0 °C. The
mixture was stirred under reflux under an oxygen atmosphere for
12 h. The reaction mixture was poured into water (10 mL), and
the organic layer was washed with water (10 mL × 2), dried over
Na2SO4, and concentrated in vacuo. The residue was purified by
column chromatography on silica gel using CHCl3 as the eluent to
give {2,6-bis[(4S)-4-methyl-2-oxazolinyl]phenyl}chloropalladium
(2a; 51.8 mg, 0.13 mmol, 54%) as a colorless solid. Mp: 185-187
Figure 2. ORTEP drawings of the Phebox-Pd complexes 2c,d,f
drawn with thermal ellipsoids at the 50% probability level: (a) i-Pr-
Phebox-PdCl (2c); (b) i-Bu-Phebox-PdCl (2d); (c) Me2-Phebox-
PdCl (2d); (d-f) side views of 2c,d,f along the Cl-Pd bond.
Hydrogen atoms have been omitted for clarity. Three and two
independent molecules were present in the asymmetric units of 2d,f,
respectively. One is shown.
20
1
°C. MS (ESI): m/z 384 [M+]. [R]D ) 320° (c 0.1, EtOH). H
NMR (CDCl3): δ 1.55 (d, J ) 6.7 Hz, 6H, CH3), 4.37 (dd, J )
6.7, 8.5 Hz, 2H, OCH2), 4.40-4.47 (m, 2H, NCH), 4.86 (t, J )
8.5 Hz, 2H, OCH2), 7.12 (t, J ) 7.9 Hz, 1H, Ar H), 7.27 (d, J )
7.9 Hz, 2H, Ar H). 13C NMR (CDCl3): δ 21.4 (CH3), 58.3 (NCH),
77.7 (OCH2), 123.9 (Ar), 126.8 (Ar), 129.8 (Ar), 168.0 (Ar), 173.8
(CdN). IR (ATR mode): ν 1615 cm-1 (CdN).
than those employing conventional methods. Further applications
of the ligand introduction route to the synthesis of other types
of pincer complexes are underway and will be reported in due
course.
Experimental Section
General Procedures. All manipulations were performed under
a nitrogen atmosphere. Nitrogen gas was dried by passage through
P2O5. NMR spectra were recorded on a JEOL JNM-AL500
{2,6-Bis[(4S)-4-(phenylmethyl)-2-oxazolinyl]phenyl}chloropalla-
dium (2b). Yield: 44% (59.2 mg, 0.11 mmol), colorless solid. Mp:
278-280 °C dec. MS (ESI): m/z 501 [(M - Cl)+]. [R]D20 ) 604°
1
spectrometer (500 MHz for H, 125 MHz for 13C, 202 MHz for
1
(c 0.1, CHCl3). H NMR (CDCl3): δ 3.08 (dd, J ) 7.3, 13.9 Hz,
1
31P). H, 13C, and 31P NMR spectra were recorded in CDCl3 or
2H, PhCH2), 3.72 (dd, J ) 2.1, 13.9 Hz, 2H, PhCH2), 4.63-4.76
(m, 6H, NCH, OCH2), 7.17 (t, J ) 7.3 Hz, 1H, Ar H), 7.26 (d, J
) 7.3 Hz, 2H, Ar H), 7.29-7.34 (m, 6H, Ar H), 7.41 (d, J ) 7.3
Hz, 4H, Ar H). 13C NMR (CDCl3): δ 40.0 (CH2), 63.3 (NCH),
75.0 (OCH2), 124.0 (Ar), 126.8 (Ar), 127.0 (Ar), 128.6 (Ar), 129.6
(Ar), 129.8 (Ar), 136.4 (Ar), 168.4 (Ar), 174.5 (CdN). Anal. Calcd
for C26H23ClN2O2Pd (537.35): C, 58.11; H, 4.31; N, 5.21. Found:
C, 57.96; H, 4.56; N, 5.11. IR (ATR mode): ν 1611 cm-1 (CdN).
DMSO-d6 at 25 °C. Chemical shifts are reported in δ (ppm)
1
referenced to an internal Me4Si standard for H NMR. Chemical
shifts of 13C NMR are given relative to CDCl3 (δ 77.0) or DMSO-
d6 (δ 39.7) as an internal standard. The 31P NMR data are reported
relative to external 85% H3PO4. ESI mass spectra were recorded
on a JEOL JMS-T100LC spectrometer. Melting points were
determined using a Yanaco MP-J3 micro melting point apparatus
and are uncorrected. The IR spectra were obtained using a JASCO
FT/IR-460plus spectrophotometer in the ATR mode. Optical
rotations were recorded on a JASCO P-1020 polarimeter. Com-
mercially available reagents were used without purification. 2-Bro-
moisophthalic acid (4)16 and Pd(PPh3)417 were prepared according
to the procedures in the literature. The ꢀ-amino alcohols 6 were
prepared by the reduction of the corresponding amino acids with
LiAlH4.
{2,6-Bis[(4S)-4-(1-methylethyl)-2-oxazolinyl]phenyl}chloropalla-
dium (2c). Yield: 57% (62.9 mg, 0.14 mmol), colorless solid. Mp:
261-263 °C dec. MS (ESI): m/z 405 [(M - Cl)+]. [R]D20 ) 493°
(c 0.1, EtOH). 1H NMR (CDCl3): δ 0.80 (d, J ) 6.7 Hz, 6H, CH3),
0.91 (d, J ) 6.7 Hz, 6H, CH3), 2.80 (dh, J ) 3.4, 6.7 Hz, 2H,
CHCH3), 4.33 (ddd, J ) 3.4, 6.7, 9.5 Hz, 2H, NCH), 4.612 (d, J
) 6.7 Hz, 2H, OCH2), 4.615 (d, J ) 9.5 Hz, 2H, OCH2), 7.13 (t,
J ) 7.9 Hz, 1H, Ar H), 7.27 (d, J ) 7.9 Hz, 2H, Ar H). 13C NMR
(CDCl3): δ 14.2 (CH3), 18.9 (CH3), 28.9 (CH), 66.9 (NCH), 71.1
(OCH2), 123.9 (Ar), 126.9 (Ar), 129.5 (Ar), 167.9 (Ar), 173.8
(CdN). Anal. Calcd for C18H23ClN2O2Pd (441.26): C, 48.99; H,
5.25; N, 6.35. Found: C, 48.72; H, 5.17; N, 6.38. IR (ATR mode):
ν 1612 cm-1 (CdN).
Synthesis of trans-Bromo(2,6-dicarboxyphenyl)bis(triphe-
nylphosphine)palladium (3). To a suspension of Pd(PPh3)4
(16) Courchay, F. C.; Sworen, J. C.; Ghiviriga, I.; Abboud, K. A.;
Wagener, K. B. Organometallics 2006, 25, 6074.
(17) Coulson, D. R. Inorg. Synth. 1972, 13, 121.

5162 Organometallics, Vol. 27, No. 19, 2008
Notes
Table 1. Selected Bond Lengths (Å) and Angles (deg) for Palladium Complexes 2c,d,f and 3
bond lengths bond angles
Pd-L1a X-Pd-C1a
compd
Pd-Xa
Pd-L2a
Pd-C1
L1-Pd-L2a
3
2.5282(4)
2.385(1)
2.410(1)
2.4109(9)
2.3040(7)
2.070(3)
2.060(6)
2.059(3)
2.3507(8)
2.040(3)
2.076(6)
2.076(3)
2.026(3)
1.934(3)
1.940(5)
1.936(3)
168.80(3)
158.0(1)
157.1(2)
157.7(1)
172.04(8)
179.1(2)
177.4(2)
177.3(1)
2c
2d
2f
a Legend: for 3, X ) Br, L1 ) L2 ) P; for 2c,d,f, X ) Cl, L1 ) L2 ) N.
{2,6-Bis[(4S)-4-(2-methylpropyl)-2-oxazolinyl]phenyl}chloropalla-
dium (2d). Yield: 50% (58.8 mg, 0.13 mmol), colorless solid. Mp:
262-264 °C dec. MS (ESI): m/z 433 [(M - Cl)+]. [R]D20 ) 484°
(c 0.1, EtOH). 1H NMR (CDCl3): δ 0.95 (d, J ) 6.7 Hz, 6H, CH3),
0.97 (d, J ) 6.1 Hz, 6H, CH3), 1.38 (ddd, J ) 4.9, 10.4, 13.1 Hz,
2H, CH2), 1.61-1.68 (m, 2H, CH), 2.42-2.47 (ddd, J ) 2.4, 9.2,
13.1 Hz, 2H, CH2), 4.30-4.35 (m, 2H, NCH), 4.47 (t, J ) 8.1 Hz,
2H, OCH2), 4.82 (t, J ) 8.1 Hz, 2H, OCH2), 7.10 (t, J ) 7.3 Hz,
1H, Ar H), 7.24 (d, J ) 7.3 Hz, 2H, Ar H). 13C NMR (CDCl3): δ
21.6 (CH3), 23.7 (CH3), 25.5 (CH), 43.8 (CH2), 61.3 (NCH), 76.5
(OCH2), 123.8 (Ar), 126.6 (Ar), 129.8 (Ar), 168.2 (Ar), 173.6
(CdN). Anal. Calcd for C20H27ClN2O2Pd (469.31): C, 51.18; H,
5.80; N, 5.97. Found: C, 50.93; H, 5.72; N, 5.99. IR (ATR mode):
ν 1616 cm-1 (CdN).
(CH3), 65.8 (CCH3), 82.9 (OCH2), 123.8 (Ar), 126.7 (Ar), 130.1
(Ar), 167.2 (Ar), 172.4 (CdN). Anal. Calcd for C16H19ClN2O2Pd
(413.21): C, 46.51; H, 4.63; N, 6.78. Found: C, 46.43; H, 4.57; N,
6.80. IR (ATR mode): ν 1617 cm-1 (CdN).
X-ray Structure Determination. Single crystals of 3 suitable
for an X-ray diffraction study were grown by slow diffusion of
Et2O into the DMSO solution. Single crystals of 2c,d,f were
obtained by their crystallization from hot AcOEt. X-ray data for
single crystals were collected on a Rigaku Saturn CCD area detector
at -100 °C using graphite-monochromated Mo KR radiation (λ )
0.710 73 Å). The structures were solved by direct methods (SIR
92) and expanded using Fourier techniques (DIRDIF99). All non-
hydrogen atoms except for C30, C31, and C32 in 2d and C29 in
2f were refined anisotropically, and the hydrogen atoms were refined
using the riding model. All calculations were performed using the
CrystalStructure crystallographic software package. Crystallographic
data and details of structure refinement are summarized in Table
S1 (see the Supporting Information).
(2,6-Bis{(4S)-4-[(1S)-1-methylpropyl]-2-oxazolinyl}phenyl)-
chloropalladium (2e). Yield: 47% (52.4 mg, 0.12 mmol), colorless
20
solid. Mp: 283-285 °C dec. MS (ESI): m/z 433 [(M - Cl)+]. [R]D
1
) 478° (c 0.1, EtOH). H NMR (CDCl3): δ 0.78 (d, J ) 6.7 Hz,
6H, CH3), 0.96 (t, J ) 7.3 Hz, 6H, CH3), 1.14-1.23 (m, 2H, CH2),
1.25-1.33 (m, 2H, CH2), 2.64 (d of sextets, J ) 3.2, 6.7 Hz, 2H,
CH), 4.43 (ddd, J ) 3.2, 6.4, 9.8 Hz, 2H, NCH), 4.57-4.64 (m,
4H, OCH2), 7.13 (t, J ) 7.3 Hz, 1H, Ar H), 7.27 (d, J ) 7.3 Hz,
2H, Ar H). 13C NMR (CDCl3): δ 11.77 (CH3), 11.83 (CH3), 26.4
(CH2), 35.6 (CH), 65.6 (NCH), 71.2 (OCH2), 123.9 (Ar), 126.8
(Ar), 129.6 (Ar), 168.1 (Ar), 173.8 (CdN). Anal. Calcd for
C20H27ClN2O2Pd (469.31): C, 51.18; H, 5.80; N, 5.97. Found: C,
50.97; H, 5.92; N, 5.73. IR (ATR mode): ν 1613 cm-1 (CdN).
[2,6-Bis(4,4-dimethyl-2-oxazolinyl)phenyl]chloropalladium (2f).
Yield: 48% (49.2 mg, 0.12 mmol), pale yellow solid. Mp: 261-263
°C dec. MS (ESI): m/z 377 [(M - Cl)+]. 1H NMR (CDCl3): δ
1.63 (s, 12H, CH3), 4.44 (s, 4H, CH2), 7.13 (t, J ) 7.9 Hz, 1H, Ar
H), 7.26 (d, J ) 7.9 Hz, 2H, Ar H). 13C NMR (CDCl3): δ 27.9
Acknowledgment. This work was supported by the
CREST program, sponsored by the JST. We also thank the
JSPS (GRANT-in-AID for Scientific Research, No. 15205015)
and the MEXT (Scientific Research on Priority Areas, No.
420) for partial financial support of this work.
Supporting Information Available: Selected crystallographic
data (Table S1) and CIF files giving crystallographic data for 2c,d,f
and 3. This material is available free of charge via the Internet at
http://pubs.acs.org.
OM800666X