Synthesis and dehydrative condensation of square-planar mono- and dinuclear hydroxopalladium complexes with the hydrotris(3,5-diisopropylpyrazolyl)borato ligand (Tp(iPr)2), Tp(iPr)2(Py)Pd-OH, and (μ-OH)2{PdTp(iPr)2(H2O)}2

Article abstract of DOI:10.1021/ic991034e

Mono- and dinuclear hydroxopalladium complexes (k₂-Tp(iPr2,X))(py)Pd-OH (1; X= H,Br) and (μ-OH)₂{Pd(κ₂-Tp(iPr2))(H₂O)}₂ (2) are prepared by base hydrolysis of the corresponding chloride complexes (κ₂-Tp(iPr₂,X))(py)Pd-Cl (3) and (μ-Cl)₂{Pd(κ³-Tp(iPr₂))}₂ (4), respectively. Functionalization of the OH part in 1 is effected via dehydrative condensation with protic substrates (H-A) to give a series of substituted products, (κ₂-Tp(iPr))(py)Pd-A (5), and treatment of the dinuclear complex 2 with excess acetic acid affords the mononuclear diacetato complex 6, (κ₂-Tp(iPr2)-H)Pd(OAc)₂(HOAc). Complexes 1-4 and 6 have been characterized crystallographically, and it is revealed that complexes 2 and 6 involve cyclic hydrogen-bonding interaction among the nitrogen atom of the pendent noncoordinated pyrazolyl group, the hydrogen atom in the protic part of the ligand (OH, AcOH), and, in the case of 2, an external water molecule.

Full text of DOI:10.1021/ic991034e

2
096
Inorg. Chem. 2000, 39, 2096-2102
Synthesis and Dehydrative Condensation of Square-Planar Mono- and Dinuclear
Hydroxopalladium Complexes with the Hydrotris(3,5-diisopropylpyrazolyl)borato Ligand
(
TpiPr
2
), TpiPr
2
(Py)Pd-OH, and (µ-OH)2{PdTpiPr
2
(H2O)}2
,
†
†
†
‡
Munetaka Akita,* Taichi Miyaji, Nobuyuki Muroga, Cordula Mock-Knoblauch,
‡
,†
,†
Waldemar Adam, Shiro Hikichi,* and Yoshihiko Moro-oka*
Research Laboratory of Resources Utilization, Tokyo Institute of Technology,
4
259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, and the Institute of Organic Chemistry,
University of W u¨ rzburg, Am Hubland, D-97074 W u¨ rzburg, Germany
ReceiVed August 27, 1999
2
iPr ,X
2
Mono- and dinuclear hydroxopalladium complexes (κ -Tp
2
)(py)Pd-OH (1; X ) H, Br) and (µ-OH)2{Pd(κ -
iPr
2
iPr ,X
2
Tp
2
)(H2O)}2 (2) are prepared by base hydrolysis of the corresponding chloride complexes (κ -Tp
)(py)Pd-
3
iPr
2
Cl (3) and (µ-Cl)2{Pd(κ -Tp
)}2 (4), respectively. Functionalization of the OH part in 1 is effected via dehydrative
condensation with protic substrates (H-A) to give a series of substituted products, (κ -Tp )(py)Pd-A (5), and
treatment of the dinuclear complex 2 with excess acetic acid affords the mononuclear diacetato complex 6,
2
iPr
2
iPr
2
(
κ -Tp
-H)Pd(OAc)2(HOAc). Complexes 1-4 and 6 have been characterized crystallographically, and it is
revealed that complexes 2 and 6 involve cyclic hydrogen-bonding interaction among the nitrogen atom of the
pendent noncoordinated pyrazolyl group, the hydrogen atom in the protic part of the ligand (OH, AcOH), and, in
the case of 2, an external water molecule.
Introduction
Scheme 1
Dehydrative condensation of transition metal hydroxo com-
plexes is a versatile synthetic method, when the conjugated acid
of the incoming ligand (H-A) is a protic substrate (Scheme
Chloride complex 3, a precursor for mononuclear complexes,
1
1
). In our laboratory, a series of transition metal peroxo
was prepared by successive addition of pyridine and the
complexes bearing hydrotris(pyrazolyl)borato ligands (A )
iPr ,X
2
potassium salt of the ligand (KTp
) to a CH2Cl2 solution of
OOR or O2) have been successfully prepared via this synthetic
PdCl2(PhCN)2. Upon addition of pyridine to PdCl2(PhCN)2, the
mixture became cloudy, suggesting formation of PdCl2(py)2,
method.2 Herein we disclose the synthesis of two types of
-5
iPr ,X
square-planar hydroxopalladium complexes, mononuclear [Tp
2
-
-
iPr ,X
2
but subsequent treatment with KTp
resulted in replacement
iPr2
(
L)Pd-OH] (1; X ) H, Br) and dinuclear complexes [Tp
of one of the two pyridine ligands to give the chloride complex
iPr
Pd(H2O)(µ-OH)2(H2O)PdTp
2
] (2), and some dehydrative
3
as a yellow solid. Complex 3a was also obtained by treatment
condensations of them.4
-6
(
4) TpRxM(L)-OH complexes. References 4a and 4b are for V. (a) Kosugi,
M.; Hikichi, S.; Akita, M.; Moro-oka, Y. Inorg. Chem. 1999, 38, 2567.
Results and Discussion
(b) Kosugi, M.; Hikichi, S.; Akita, M.; Moro-oka, Y. J. Chem. Soc.,
Synthesis of Mononuclear Hydroxopalladium Complex
Dalton Trans. 1999, 1369. References 4c-4e are for Mn. (c)
Komatsuzaki, H.; Ichikawa, S.; Hikichi, S.; Akita, M.; Moro-oka, Y.
Inorg. Chem. 1998, 37, 3652. (d) Komatsuzaki, H.; Sakamoto, N.;
Satoh, M.; Hikichi, S.; Akita, M.; Moro-oka, Y. Inorg. Chem. 1998,
iPr ,X
Tp
2
(py)Pd-OH (1). Synthetic procedures for mononuclear
hydroxopalladium complexes are summarized in Scheme 2.
3
7, 6554. (e) Kitajima, N.; Singh, U. P.; Amagai, H.; Osawa, M.;
†
Tokyo Institute of Technology.
University of W u¨ rzburg.
Moro-oka, Y. J. Am. Chem. Soc. 1991, 113, 7757. Reference 4f is for
Fe. (f) Ogihara, T.; Hikichi, S.; Fujisawa, K.; Kitajima, N.; Akita,
M.; Moro-oka, Y. Inorg. Chem. 1997, 36, 4539. References 4g and
4h are for Co, Ni. (g) Hikichi, S.; Yoshizawa, M.; Sasakura, Y.; Akita,
M.; Moro-oka, Y. J. Am. Chem. Soc. 1998, 120, 10567. (h) Kitajima,
N.; Hikichi, S.; Tanaka, M.; Moro-oka, Y. J. Am. Chem. Soc. 1993,
115, 5496. Reference 4i is for Cu. (i) Kitajima, N.; Koda, T.;
Hashimoto, S.; Kitagawa, T.; Moro-oka, Y. J. Am. Chem. Soc. 1991,
113, 5664. Reference 4j is for Ru. (j) Takahashi, Y.; Akita, M.; Hikichi,
S.; Moro-oka, Y. Inorg. Chem. 1998, 37, 3186. For other metal
complexes see ref 4k. (k) Parkin, G. AdV. Inorg. Chem. 1995, 42,
291.
‡
(
1) (a) Bryndza, H. E.; Tam, W. Chem. ReV. 1988, 88, 1163. (b) Gilje, J.
W.; Roesky, H. W. Chem. ReV. 1994, 94, 895.
(
2) (a) Trofimenko, S. Chem. ReV. 1993, 93, 943. (b) Kitajima, N.; Tolman,
W. B. Prog. Inorg. Chem. 1995, 43, 419. (c) Kitajima, N.; Moro-oka,
Y. Chem. ReV. 1994, 94, 737. (d) Trofimenko, S. Scorpionates The
Coordination Chemistry of Polypyrazolylborate Ligands; Imperial
College Press: London, England, 1999.
(
3) Our recent work based on the TpR
x
ligand. (a) Akita, M.; Miyaji, T.;
Hikichi, S.; Moro-oka, Y. J. Chem. Soc., Chem. Commun. 1998, 1005.
b) Akita, M.; Miyaji, T.; Hikichi, S.; Moro-oka, Y. Chem. Lett. 1999,
13. (c) Akita, M.; Ohta, K.; Takahashi, Y.; Hikichi, S.; Moro-oka,
(
8
(5) Abbreviations used in this paper. TpiPr2, hydrotris(3,5-diisopropylpyra-
iPr ,Br
Y. Organometallics 1997, 16, 4121. (d) Ohta, K.; Hashimoto, M.;
Takahashi, Y.; Hikichi, S.; Akita, M.; Moro-oka, Y. Organometallics
zolyl)borate; Tp
borate; Tp
2
, hydrotris(3,5-diisopropyl-4-bromopyrazolyl)-
iPr ,X
iPr2
iPr ,Br
Me
2
2
, Tp and Tp
2
; Tp
, hydrotris(3,5-dimethylpyra-
R
1
999, 18, 3234. (e) Takahashi, Y.; Akita, M.; Hikichi, S.; Moro-oka,
Y. Organometallics 1998, 17, 4884. References 3f-3h are reviews.
f) Akita, M.; Hikichi, S.; Moro-oka, Y. J. Synth. Org. Chem. 1999,
7, 619. (g) Hikichi, S.; Akita M., Moro-oka, Y. Coord. Chem. ReV.,
in press. (h) See also references cited in ref 3d.
zolyl)borate; Tp , a general term for substituted hydrotris(pyrazolyl)-
borate; pz
the 4-position of the pz
x
iPr
R
2
2
, 3,5-diisopropylpyrazolyl; 4-pz -H, hydrogen atom at
R
(
5
2
ring.
(6) A part of the present result was already reported as a communication.
See ref 3a.
1
0.1021/ic991034e CCC: $19.00 © 2000 American Chemical Society
Published on Web 04/22/2000

Hydroxopalladium Complexes
Table 1. Spectroscopic Data for the TpiPr ,X
Inorganic Chemistry, Vol. 39, No. 10, 2000 2097
Pd Complexes 1-6a
1H NMR/δ
2
H
/ppm
4-pziPr
-Hb
CH(CH
)
3 2
c,d
L
X
IR/cm-1
complex (X)
2
8.85 (2H, dt, 5, 2)e
6.67 (1H, tt, 8, 2)
-1.79h
-1.93h
2476, 1607, 1536
i
k
j
j
j
1
a
6.21,
5.95,
4.62, 3.71 (2H),
2.98, 2.93,
2.35
4.63, 3.91,
3.83, 3.21,
f
(H)
g
5.91
6.38 (2H, ddd, 8, 5, 2)
e
i
k
1
b
8.49 (2H, dt, 6. 2)
6.59 (1H, tt, 8, 2)
2506, 1607, 1513
f
(Br)
3.17, 3.09
6.30 (2H, ddd, 8, 6, 2)g
2m
6.46 (2H),
5.73 (4H)
5.96,
4.01 (2H), 3.62 (4H),
3.49 (4H), 2.78 (2H)
3.98, 3.54
3.51, 2.79
2.59, 2.06
4.78, 3.86,
3.77, 3.01
-1.71
(2H)
3556, 2481, 1537
n
i
(H)
l
o
8.75 (2H, dt, 5, 2)e
i
k
j
3
a
2481, 1607, 1535
f
(H)
5.82,
7.68 (1H, tt, 8, 2)
o
g
5.71
7.20 (2H, ddd, 8, 5, 2)
e
i
k
j
3
b
8.52 (2H, m)
6.48 (1H, m)
2512, 1608, 1512
f
(Br)
g
3.28 (2H)
6.18 (2H, m)
4l,p
6.33 (2H),
5.72 (4H)
3.70 (2H),
3.41 (8H),
2480, 1536
i
j
(H)
2
.84 (2H)
9.11 (2H, m)e
3.02
2770, 2485, 1606,
r
i
k
5
a
6.22,
6.01,
4.71, 3.79,
3.65, 3.26,
2.98, 2.26
4.55, 3.77,
3.57, 3.25,
3.08, 2.23
4.24, 3.76,
3.57, 3.15,
2.91, 2.48
3.82 (2H), 3.66,
3.27 (2H), 3.10,
f
(3H, s)q
j
s
(H)
6.72 (1H, m)
1535, 1217
5.91
6.38 (2H, m)g
9.11 (2H, d, 2)
e
7.03 (2H, m)u
t
i
k
V
5
b
6.38,
5.90,
2475, 1609, 1587,
f,t
j
(H)
6.58 (4H, m),
1535
5.89
6.30 (2H, t, 7)g
w
e
i
x
k
5
c
6.33,
5.89,
9.21 (2H, dt, 5, 1)
6.53 (1H, tt, 7, 1)
w
2.04
2478, 1628, 1607,
f
j
x
(H)
1538, 1322
o
5.76
i
x
k
x
6
6.32,
5.82 (2H)
2.03 (6H),
1.79 (3H)y
2552, 1713, 1609,
x
j
(H)
1575, 1541, 1499,
x
x
1
459, 1334
1H NMR spectra were observed in C
D at 400 MHz unless otherwise stated, and multiplicity and coupling constants (in Hz) are shown in
6 6
a
b
parentheses. Signals without indication of multiplicity are singlet signals. IR spectra were recorded as KBr pellets. The 4-pyrazolyl proton signals.
c
g
n
u
d
e
f
Septets with J ≈ 7 Hz or multiplets. Methyl signals appeared as doublets in the range 2-0 ppm. Ortho proton signals. Para proton signals.
h
i
j
k
l
m
Meta proton signals. OH signals. ν(BH). ν(CdC) of pz rings. ν(CdC) of py rings. Observed in CDCl
3
.
8
Observed in tol-d at -45 °C.
o
p
q
r
s
t
ν(OH). Slightly broad signals. Observed at -20 °C. Methyl signals. ν(CH) for the OMe group. ν(C-O). Overlapped with the Ph signals.
Ph signals. V ν(CdC) of the Ph ring. w Overlapped with the 4-pz signal. ν(CdO). y NH and OH proton signals could not be located.
x
Scheme 2
spectra of 1a and 1b contained singlet signals around δH -1.8
assignable to OH, which disappeared upon addition of D2O.
These data were consistent with the formulation of 1 as a square-
2
iPr ,X
2
planar hydroxopalladium complex with a κ -Tp
which was verified by X-ray crystallographic analysis of the
-Br derivative 1b (Figure 1). According to the CSD database,
ligand,
4
complex 1b is a rare example of a structurally characterized
mononuclear palladium complex with a terminal hydroxo ligand,
whereas dinuclear µ-hydroxo complexes such as 2 have many
precedents (see below). In addition, previous examples of
mononuclear hydroxopalladium complexes, [(terpy)Pd-OH]-
7
a
7b
ClO4‚H2O and Tp(1,4-butandiyl)Pd(IV)-OH‚(µ-cresol)2,
contain hydrogen-bonding interactions with Lewis bases such
as oxygen atoms of water and phenol molecules and counter-
anions, but no such interaction is present in 1. Single crystals
of 1b contain a CH2Cl2 solvate, but the separation between the
OH oxygen atom and the chlorine atom in the CH2Cl2 solvate
(3.623(6) Å) exceeds the acceptable range of hydrogen-bonding
interaction. Thus, the structure of the mononuclear complex 1b
reveals that such hydrogen-bonding interactions are not always
of the Cl-bridged dinuclear complex 4 (see below) with pyridine.
1
iPr
2
A H NMR spectrum of Tp
inequivalent 4-pyrazolyl proton signals (4-pz
B-H vibration (IR) was observed in the range for κ -Tp
ligands (<2500 cm ) (Table 1). These data were consistent
with a square-planar geometry, which was confirmed by X-ray
crystallography of 3a. An ORTEP view of 3a is included in
the Supporting Information, and its structural features will be
discussed later together with the hydroxo complex.
(py)Pd-Cl (3a) contained three
iPr
5
2
-H), and the
2
iPr
2
-
1 3c
4
a requisite for hydroxometal complexes.
Structural parameters for 1a and 3b are summarized in Table
2. The square-planar coordination geometry of Pd is revealed
by the following two structural features. (i) The Pd‚‚‚N31
distances of ca. 3.1 Å are much longer than the other Pd-N11
and Pd-N21 distances of ca. 2.0 Å and reveal no bonding
interaction between the Pd center and the free pyrazolyl ring
The hydroxo complex 1 was prepared by treatment of a CH2-
Cl2 solution of the chloride complex 3 with aqueous NaOH
solution. A variety of TpR
M-OH and TpR
(L)M-OH type
x
x
4
compounds were prepared by this method. Spectroscopic
(
7) (a) Castan, P.; Dahan, F.; Wimmer, S.; Wimmer, F. L. J. Chem. Soc.,
Dalton Trans. 1990, 2679. (b) Canty, A. J.; Jin, H.; Skelton, B. W.;
White, A. H. J. Organomet. Chem. 1995, 503, C16.
features of 1 were very similar to those of the precursor 3 (Table
1
1
). Although OH vibration could not be detected by IR, H NMR

2098 Inorganic Chemistry, Vol. 39, No. 10, 2000
Akita et al.
Table 2. Selected Structural Parameters for the Core Parts of the TpiPr ,X
Pd Complexes 1-6a
2
mononuclear complexes
dinuclear complexes
complexes
Pd1-N11
Pd1-N21
Pd1-N31
Pd1-N32
Pd1-X
1b
3ab
6c
2
4
2.016(6)
2.047(5)
3.808(6)
3.181(5)
2.034(7) (N41)
2.011(4) (O1)
2.002(3)
2.015(3)
3.498(4)
3.105(3)
2.032(3) (N41)
2.285(1) (Cl1)
2.007(4)
2.010(3)
3.199(4)
3.299(4)
1.987(6)
2.019(7)
3.524(8)
3.158(8)
1.989(4)
1.981(4)
2.785(4)
3.372(3)
2.335(1) (Cl1)
2.318(1) (Cl1*)
3.4694(6)
2.026(4) (O1)
2.025(3) (O3)
2.643(7) (N31-O2)
2.018(6) (O1)
2.016(5) (O1*)
Pd1-Y
others
2.932(9) (O1-O2)
2
.576(6) (O4-O5)
2.78(1) (N31-O2)
(Pd1-Pd1*)
3
.0514(9) (Pd1-Pd1*)
N11-Pd1-N12
N11-Pd1-X
N11-Pd1-Y
N21-Pd1-X
N21-Pd1-Y
X-Pd1-Y
87.3(2)
86.2(1)
87.6(1)
87.1(3)
86.6(1)
174.9(2) (N41)
93.1(2) (O1)
95.2(2) (N41)
179.5(2) (O1)
84.3(2)
176.7(1) (N41)
92.59(9) (Cl1)
92.1(1) (N41)
177.72(9) (Cl1)
89.01(9)
178.6(1) (O1)
94.2(1) (O3)
93.1(1) (O1)
177.2(2) (O3)
85.1(1)
172.7(2) (O1)
93.1(3) (O1*)
98.0(2) (O1)
178.7(3) (O1*)
81.7(3)
179.0(1) (Cl1)
95.5(1) (Cl1*)
94.3(1) (Cl1)
177.70(8) (Cl1*)
83.5(3)
a
Interatomic distances in Å and bond angles in deg. b The numbering scheme for the core part of 3a is the same as that of 1b except for Cl1
(
O1). c 6: C1-O1, 1.286(6) Å; C1-O2, 1.228(7) Å; C3-O3, 1.278(7) Å; C3-O4, 1.217(8) Å; C5-O5, 1.305(8) Å; C5-O6, 1.182(7) Å.
Scheme 3
Synthesis of Dinuclear Hydroxopalladium Complex 2.
iPr
Treatment of PdCl2(MeCN)2 with KTp
2
in the absence of
pyridine furnished the chloride-bridged dinuclear complex 4
Scheme 3). It is essential to use the acetonitrile precursor and
(
Figure 1. Molecular structure of 1b drawn at the 30% probability
level.
to carry out the reaction in acetonitrile, otherwise a complex
mixture of products is obtained.
2
ligand). In κ -TpRxM com-
2
1
(
i.e., κ -coordination of the TpR
x
The very broad H NMR spectrum of 4 observed at room
R
plexes, it has been observed that the pendent pz
x
rings are
temperature suggested dynamic behavior, and indeed sharp
projected away from the metal center to minimize steric
signals were obtained by lowering the temperature. At -45 °C,
repulsions among the pzR
substituents and the ligands. The
iPr
2
x
the 4-pz
-H signal separated into two sets of absorptions in
situation can be best described by the M‚‚‚N31 distance being
longer than the M‚‚‚N32 distance (M-N31 > M-N32). (ii)
The interligand angles fall in the range 84-95°, close to a right
a 1:2 ratio, indicating a mirror symmetrical structure that was
confirmed by X-ray crystallography (Figure 2a and Table 2).
The square-planar PdN Cl coordination geometry is similar to
2
2
angle. The Pd-N(pyridine) lengths are essentially the same as
those of the mononuclear complexes discussed above, but a
iPr
iPr
2
the Pd-N(pz
2
) lengths, which are similar to those in the
weak coordination of the third pz
part is evidenced by the
iPr
3a,b
previously reported Tp
2.011(4) Å) is comparable to the reported values of hydroxo-
palladium complexes (1.966(3) Å in [(terpy)Pd-OH]ClO4‚
2
Pd complexes. The Pd-O distance
following observation. As for the Pd-N31,32 distances, the
situation of complex 4 is opposite those of complexes 1b and
3a discussed above. The N31 lone pair electrons are projected
toward the Pd center, and the N31 atom is located closer to the
Pd center than the N32 atom is (Pd-N31 < Pd-N32), although
the Pd-N31 separation (2.785(4) Å) is substantially longer than
(
7a
7b
H2O; 2.011(8) Å in Tp(1,4-butandiyl)Pd(IV)-OH‚(µ-cresol)2)
and Pd-OPh complexes (2.106(3) Å in (Me3P)2(Cl)Pd-OPh;
8a
8b
2
.098(6) Å in cis-(dmpe)(Me)Pd-OPh; 1.996(7), 1.983(6) Å
8c
in (bipy)Pd(OPh)2). The Pd-Cl distance (2.285(1) Å) is similar
the coordinated Pd-N distances (∼1.98 Å). The weak coordina-
iPr
to that in a related compound (2.288(1) Å in [(2,6-bis(2-
tion of the third pz
2
group should be a result of increased
+
9
imidazolin-2-yl)pyridine)Pd-Cl] ).
Lewis acidity of the palladium center coordinated by the more
electronegative Cl atoms. The Pd-Cl lengths are comparable
(
8) (a) Kim, Y.-J.; Osakada, K.; Takenaka, A.; Yamamoto, T. J. Am.
to those in related square-planar dinuclear Cl-bridged (µ-Cl)2-
Chem. Soc. 1990, 112, 1096. (b) Seligson, A. L.; Cowan, R. L.;
Trogler, W. C. Inorg. Chem. 1991, 30, 3371. (c) Kapteijn, G. M.;
Grove, D. M.; Kooijman, H.; Smeets, W. J. J.; Spek, A. L.; van Koten,
G. Inorg.Chem. 1996, 35, 526.
2
{
Pd{κ -L)}2 complexes: 2.408(2) and 2.428(2) Å in (µ-Cl)2-
(9) Baker, A. T.; Craig, D. C.; Singh, P. Aust. J. Chem. 1991, 44, 1659.

Hydroxopalladium Complexes
Inorganic Chemistry, Vol. 39, No. 10, 2000 2099
bonding interactions, and the Pd-O distances (2.018(6) (O1)
and 2.016(5) Å (O1*)) are comparable to those in previously
reported complexes containing a diamond (µ-OH)2Pd2 core
2
- 12a
(
2.068(6) and 2.077(6) Å in [(µ-OH)2{Pd(C6F5)2}2]
;
t
12b
2
2
2
.140(4) and 2.142(5) Å in (µ-OH)(µ-NHBu ){Pd(Ph)(PPh3)}2;
.125(6) Å in (µ-OH){Pd(Ph)(PPh3)}2CrCp(CO)3; 2.052-
.126(10) Å in (µ-OH)2{Pd(Ph)(PPh3)}2; 2.082(4) Å in [(µ-
OH)2{Pd(dppp)}2] ; 2.209(5) and 2.034(5) Å in (µ-OH)(µ-
Br){Pd(C6H4-2-CH2NMe2)}2; 2.093(4) and 2.195(5) Å in (µ-
OH)(µ-NHC6H4-4-OMe){Pd(Ph)(PPh3)}2; 2.075(3) and 2.81(3)
Å in [(µ-OH)2{Pd(PMe3)2}2] ). When the ligand (L1, L2)
1
2c
1
2d
2
+ 12e
12f
12g
2
+ 12h
2
iPr
2
in (κ -Tp
)PdL1L2 possesses a protic hydrogen atom located
at a distance appropriate for hydrogen-bonding with the nitrogen
iPr
atom of the noncoordinated pz
2
ring, formation of a hydrogen
bond leads to a stable chelating structure. Such an interaction
2
has been noted for the hydroperoxopalladium complex (κ -
iPr
3b
Tp
2
)(Ph3P)Pd-OOH and the acetato complex 6 (see below),
where the protic OOH and AcOH hydrogen atoms are hydrogen-
bonded with the pendent pz
iPr
2
nitrogen atoms, respectively. The
situation of 2 is different from these in that the water molecule
intervenes between the two components to form a ternary
hydrogen bond because the OH‚‚‚N31 separation is too long
for formation of a binary hydrogen bond. The mirror sym-
1
metrical H NMR features even at low temperatures (1:2 patterns
iPr
for the 4-pz
2
-H signals) may be a result of dissociation of
the water molecule in solution because the intensity of the singlet
OH signal at δH -1.71 is for two protons (water signal could
1
not be located), and H NMR spectra with mirror-symmetrical
features consistent with the dissociated form similar to 4 were
obtained even at low temperatures. The dynamic behavior of
iPr
the dehydrated form, (µ-OH)2(PdTp
2
)2, can be explained in
1
1
terms of a mechanism as discussed for 4.
Dehydrative Condensation of Hydroxo Complexes 1a and
2
with Protic Substrates. The obtained mononuclear hydroxo
Figure 2. Molecular structures of 4 (a) and 2 (b) drawn at the 30%
probability level.
complex 1a was subjected to dehydrative condensation with a
couple of protic substrates with varying acidity (eq 1). The acidic
3
10a
{
Pd(η -cycloheptenyl)}2; 2.4630(6) and 2.4719(6) Å in (µ-
3
10a
Cl)2{Pd(η -cyclooctenyl)}2; 2.337(1) Å (trans to N) in (µ-
Cl)2{Pd(CH2CH2CH2NMe2)}2.1 Thus, the coordination geometry
of Pd in 4 is best described as a distorted square pyramid. The
weak coordination causes a shift of the νBH vibration to the
0b
2
iPr
-1 3c
κ -Tp
2
region (<2500 cm ). The dynamic behavior of 4
can be explained in terms of a mechanism involving pseudoro-
tation of the Tp
iPr
2
3
2
ligand associated with the κ -κ hapticity
change, and analogous mechanisms have been well documented
for square-planar (κ2-TpR
)ML2 complexes (M ) Ru, Rh).
11
x
Hydrolysis of the Cl-bridged dimer 4 with aqueous NaOH
solution successfully afforded the µ-hydroxo complex 2 (Scheme
substrates, PhOH and AcOH, readily reacted to give the
corresponding condensates 5b and 5c, respectively. Even less
acidic MeOH was condensed with 1a, and crystallization of 1a
from MeOH gave 5a. In addition, condensation with hydrop-
eroxides (ROOH) successfully afforded a series of peroxo-
palladium complexes as we reported previously in a communi-
3
). The presence of an OH group is revealed by the νOH vibration
-
1
1
at 3556 cm , and the other H NMR and IR features are very
similar to those of the chloride precursor 2. A broad H NMR
1
spectrum sharpened at a low temperature, and a mirror sym-
metrical structure was suggested by the 1:2 pattern of the
iPr
4
-pz
2
-H signals. Although these features are apparently
3
a,b
cation.
iPr
iPr
2
consistent with a structure analogous to 4, Tp Pd(µ-Cl)2PdTp ,
2
X-ray crystallography (Figure 2b) revealed a dinuclear structure
containing a unique ternary hydrogen-bonding interaction among
(
12) (a) Lopez, G.; Ruiz, J.; Garcia, G.; Vicente, C.; Casabo, J.; Molins,
E.; Miravitlles, C. Inorg. Chem. 1991, 30, 2605. (b) Driver, M. S.;
Hartwig, J. F. Organometallics 1997, 16, 5706. (c) Kuznetsov, V. F.;
Bensimon, C.; Facey, G. A.; Grushin, V. V.; Alper, H. Organometallics
a water molecule, the µ-OH oxygen atom, and the noncoordi-
iPr
nated pz
2
nitrogen atom. The O1‚‚‚O2 (2.932(9) Å) and
1
997, 16, 97. (d) Grushin, V. V.; Alper, H. Organometallics 1993,
2, 1890. (e) Pisano, C.; Consiglio, G.; Sironi, A.; Moret, M. J. Chem.
O2‚‚‚N31 distances (2.78(1) Å) are in the range of hydrogen-
1
Soc., Chem. Commun. 1991, 421. (f) Ruiz, J.; Cutillas, N.; Sampedro,
J.; Lopez, G.; Hermoso, J. A.; Martinez-Ripoll, M. J. Organomet.
Chem. 1996, 526, 67. (g) Ruiz, J.; Rodriguez, V.; Lopez, G.; Chaloner,
P. A.; Hitchcock P. B. J. Chem. Soc., Dalton Trans. 1997, 4271. (h)
Pieri, G.; Paasquali, M.; Leoni, P.; Englert, U. J. Organomet. Chem.
1995, 491, 27.
(
10) (a) Rosset, J. M.; Glenn, M. P. Cotton, J. D.; Willis, A. C.; Kennard,
C. H. L.; Byriel, K. A.; Riches, B. H.; Kitching, W. Organometallics
1
1
998, 17, 1968. (b) Suggs, J. W.; Lee K. S. J. Organomet. Chem.
986, 299, 297.
(11) See references cited in refs 3c-3e.

2100 Inorganic Chemistry, Vol. 39, No. 10, 2000
Akita et al.
1
Figure 4. Pyridyl H NMR signals of 7 observed at -40 °C (in CDCl
3
at 400 MHz). Peaks with asterisks are due to impurities.
Scheme 4
Figure 3. Molecular structures of 6 drawn at the 30% probability level.
The square-planar products (κ -TpiPr
2
)(py)Pd-A (5) were
2
readily characterized on the basis of their spectroscopic features
-
1
similar to 3, i.e., (1) νBH vibration below 2500 cm indicating
2
iPr
3c
κ -coordination of the Tp
2
ligand and (2) three inequivalent
complexes can be chiral. (κ -TpiPr2)(L)Pd-X-type complexes
2
iPr
4
-pz
2
-H signals indicating an unsymmetrical structure.
To examine the condensation ability of the dinuclear complex
fall in this category (Scheme 4). If a chiral hydroxo complex
(
X ) OH) is obtained, it is expected to work as a unique chiral
2
, the reaction with acetic acid was examined. Treatment of 2
13
base. Then we attempted diastereoselective synthesis of chiral
complexes using optically active N donors (nicotine and
quinidine) and phosphine (PPh2(neomenthyl)).
The chloride complex with nicotine ligand, (κ -TpiPr2)-
(nicotine)Pd-Cl (7), was obtained as a pale-yellow solid by a
procedure similar to the preparation of 3. The spectroscopic
features of 7 (νBH ) 2479 cm ; three 4-pz -H H NMR
signals) were very similar to those of 3, indicating formation
of an analogous square-planar complex. Although a H NMR
spectrum observed at room temperature contained only a single
set of signals suggesting selective formation of one diastereomer,
upon cooling the sample to -40 °C the p-pyridyl signal
separated into two doublets as shown in Figure 4 and diaste-
reoselectivity was estimated to be ca. 15% de. Because it was
difficult to recover 7 from the reaction mixture because of its
with an excess amount of acetic acid followed by crystallization
from pentane afforded a mononuclear diacetate complex hy-
drogen-bonded to another molecule of acetic acid 6 (Scheme
1
2
3
). A H NMR spectrum of 6 contains two sets of acetate-
iPr
methyl and 4-pz
2
-H signals in a 1:2 ratio, and an IR spectrum
containing several νCdO vibrations reveals the presence of
multiple acetate functional groups. Although the 1:2 H NMR
pattern suggests a mirror symmetrical structure, X-ray crystal-
lography reveals an unsymmetrical structure containing three
acetate groups formulated as (κ -Tp
1
-1
iPr2
1
1
2
iPr
2
-H)Pd(OAc)2(HOAc)
(Figure 3). One of the two coordinated acetato ligands is
iPr
hydrogen-bonded to the noncoordinated pz
2
nitrogen atom
(N31‚‚‚O2, 2.643(7) Å) in a manner similar to 2 discussed
above, and the other acetato ligand is hydrogen-bonded to the
third acetic acid molecule (O4‚‚‚O5, 2.576(6) Å). Because of
the hydrogen-bonding interaction, which causes delocalization
of π electrons of the two acetato ligands over the O-C-O
linkage, bond alternation is not clear for the acetato ligands;
i.e., the C-O lengths are in the narrow range (C1-O1,
great solubility in organic solvents, the less soluble dimethyl
derivative (Tp
tivity was found to be worse than 7 (5% de). Base hydrolysis
of the chloride complex 7 afforded a new complex tentatively
assigned as the corresponding hydroxo complex (κ -Tp
Me
2
) 8 was also prepared but the diastereoselec-
2
iPr
2
1
.286(6) Å; C1-O2, 1.228(7) Å; C3-O3, 1.278(7) Å; C3-
)-
O4, 1.217(8) Å), whereas the C-O and CdO bonds in the third
acetate group are in the typical ranges (C5-O5, 1.305(8) Å;
C6-O5 Å, 1.182(7) Å). The Pd coordination geometry is a
typical square-planar one.
(nicotine)Pd-OH. Attempted syntheses of chloride complexes
with quinidine, 2-methyloxazoline, and PPh2(neomenthyl) ligands
resulted in a mixture of products from which no characterizable
compounds could be isolated.
The reaction proceeds in a stepwise manner because dinuclear
Conclusions
intermediates such as the mono-µ-hydroxo-mono-µ-acetato
iPr
complex (µ-OH)(µ-OAc)(PdTp
plex (µ-OAc)2(PdTp
2
)2 and the bis-µ-acetato com-
Mono- (1) and dinuclear hydroxopalladium complexes (2)
are prepared successfully by base hydrolysis of the correspond-
ing chloride precursors 3 and 4, respectively, and fully
characterized by spectroscopic and crystallographic analyses.
The mononuclear complex 1 readily reacts with a series of protic
iPr
2
)2 were adeventitiously obtained from
reactions of 2 with lesser amounts of acetic acid and identified
spectroscopically (see Experimental Section). The symmetrical
H NMR feature of 6 suggests dissociation of the third AcOH
molecule in solution and switching of the N‚‚H‚‚O hydrogen
bond between the two acetato ligands.
Attempted Diastereoselective Synthesis of Chiral Com-
plexes Using Optically Active N Donors. cis-(L′)2Pd(L)-X-
type square-planar complexes have no element of asymmetry.
But when a pendant that leads to differentiation of the two
square-planar faces is attached to the ligand, square-planar
1
2
iPr
2
substrates (H-A) to give condensates (κ -Tp
)(py)Pd-A (5),
and the dinuclear complex 2 is found to be condensed with acetic
acid. In contrast to the static mononuclear complexes 1, 3, 5,
and 6, dinuclear complexes 2 and 4 exhibit dynamic behavior
(
13) Fujii, A.; Hagiwara, E.; Sodeoka, M. J. Am. Chem. Soc. 1999, 121,
5450.

Hydroxopalladium Complexes
Inorganic Chemistry, Vol. 39, No. 10, 2000 2101
iPr ,Br
Scheme 5
pyridine (0.60 mL, 6.2 mmol), and KTp
2
(995 mg, 1.79 mmol),
the 4-Br derivative 3b was obtained as a pale-yellow solid (886 mg,
.959 mmol, 71% yield) after crystallization from CH Cl -hexane.
Anal. Calcd for C32 ClBr Pd: C, 41.63; H, 5.25; N, 10.62; Cl,
.84; Br, 25.96. Found: C, 41.64; H, 5.41; N, 10.81; Cl, 4.03; Br,
5.43.
Preparation of (K -TpiPr2)(py)Pd-OH (1a). (i) Hydrolysis of 3a.
Cl solution (5 mL) of 3a (308 mg, 0.595 mmol) was added
aqueous 2 M NaOH solution (2.0 mL), and the mixture was stirred for
5 h at room temperature. The aqueous layer was removed via a syringe,
and the organic layer was dried over Na SO . Concentration followed
0
2
2
H48BN
7
3
3
2
2
To a CH
2
2
1
2
4
by addition of hexane gave 1a as a pale-yellow solid (201 mg, 0.402
mmol, 68% yield).
(
ii) One-Pot Synthesis from PdCl
2
(PhCN)
2
. Upon addition of
(PhCN) (3.018
pyridine (3 mL) to a CH Cl solution (25 mL) of PdCl
2
2
2
2
g, 7.88 mmol) the solution changed from dark-red to yellow and yellow
precipitates (PdCl (py) ) appeared. Then KTp (3.992 g, 7.91 mmol)
2 2
and the averaging of the pzR
terms of a combination of fast κ -κ interconversion and
pseudorotation of the TpR
ligand.
signals has been interpreted in
x
iPr2
2
3
was added. After the resulting mixture was stirred for 90 min at room
temperature, inorganic salts were removed by filtration through a Celite
pad. To the filtrate was added aqueous 1 M NaOH solution (20 mL),
and the mixture was stirred for 25 h at room temperature. Then the
aqueous layer was removed via a syringe and the organic layer was
dried over Na SO . Filtration through a Celite pad and concentration
2 4
followed by addition of pentane gave 1a (3.848 g, 5.76 mmol, 73%
yield) as a pale-yellow solid, which was collected on a glass frit and
x
In addition to these aspects, a common structural motif
involving hydrogen-bonding interactions has been noted for
2
iPr
2
(
κ -Tp
)(L)Pd-A-type complexes, where A contains a protic
2
iPr
2
hydrogen atom, i.e., 2, 6, and (κ -Tp
)(PPh3)Pd-OOH. The
nitrogen atom is hydrogen-bonded
iPr
pendant, noncoordinated pz
2
to the protic hydrogen atom in A to form a stable chelating
structure. The structural motif suggests a plausible reaction
mechanism of dehydrative condensation of the square-planar
7
dried under reduced pressure. Anal. Calcd for C32H52BN OPd: C, 57.52;
H, 7.80; N, 14.68. Found: C, 57.10; H, 7.76; N, 14.75.
2
iPr ,Br
2
Preparation of (K -Tp
obtained from PdCl (PhCN)
4.95 mmol), and NaTp
described for complex 1a. Anal. Calcd for C32
O): C, 41.65; H, 5.58; N, 10.63. Found: C, 41.25; H, 5.26; N, 10.30.
)(py)Pd-OH (1b). Complex 1b was
(380 mg, 0.99 mol), pyridine (0.4 mL,
(720 mg, 0.99 mol) following method ii
Br Pd (1b‚
hydroxopalladium complexes 1 and 2. The pendent pzR
group
x
2
2
iPr ,Br
2
may assist incorporation of a nucleophile via formation of
hydrogen-bonding interaction (A) as shown in Scheme 5 because
H51BN
O
7 2
3
the pzR
H
2
x
nitrogen atom is the most basic site in the molecule.
iPr
Preparation of (Tp
2
2
Pd) (µ-Cl)
2
(4). A mixture of PdCl
(883 mg, 1.76 mmol) dissolved in
2 2
(MeCN)
Subsequent nucleophilic attack of the lone pair electrons of A
at the Pd center to give a trigonal-bipyramidal intermediate (B)
followed by proton migration (C) and water elimination would
furnish the condensate (D).
iPr
(
456 mg, 1.76 mmol) and KTp
2
MeCN (30 mL) was stirred for 40 min at ambient temperature. After
filtration through a Celite pad, the volatiles were removed under reduced
pressure. Extraction of the residue with CH
lization from CH Cl -hexane gave 4 as dark-red crystals (524 mg,
.423 mmol, 48% yield). Anal. Calcd for C54 Pd : C, 53.38;
H, 7.65; N, 13.84. Found: C, 52.90; H, 7.57; N, 13.75.
2 2
Cl followed by crystal-
2
2
Experimental Section
0
H
92
B
2
N
12Cl
2
2
General Methods. All manipulations were carried out under an inert
atmosphere by using standard Schlenk techniques. THF, pentane,
hexane (Na-K alloy), MeOH (Mg(OMe)
were treated with appropriate drying agents, distilled, and stored under
argon. H and C NMR spectra were recorded on JEOL EX400 ( H,
00 MHz; C, 100 MHz) and Bruker AC200 spectrometers ( H: 200
iPr
Preparation of (Tp
2
Pd‚OH
2
)
2
(µ-OH)
2
(2). To a THF solution
(
12 mL) of 4 (238 mg, 0.196 mmol) was added aqueous 1 M NaOH
2 2 2 2
), CH Cl , and MeCN (CaH )
solution (2 mL), and the mixture was stirred for 1 h at room temperature.
The aqueous layer was removed via a syringe, and the organic layer
1
13
1
1
3
1
was dried over Na
crystallization from THF gave 2 as yellow crystals (93 mg, 0.076 mmol,
9% yield). Anal. Calcd for C54 Pd (4‚(H O) ): C, 53.41;
H, 8.15; N, 13.85. Found: C, 53.57; H, 7.97; N, 13.99.
2 4
SO . Filtration through a Celite pad followed by
4
MHz). Solvents for NMR measurements containing 0.5% TMS were
dried over molecular sieves, degassed, distilled under reduced pressure,
and stored under Ar. IR spectra were obtained on a JASCO FT/IR 5300
3
H
98
B
N
2 12
O
4
2
2
2
2
iPr
2
iPr 14
iPr ,Br 3e
15
Preparation of (K -Tp
)(py)Pd-OMe (5a). Recrystallization of
1a from MeOH gave 5a as a pale-yellow solid. Anal. Calcd for C33.5
BN
spectrometer. KTp
2
,
NaTp
2
,
PdCl
2
(PhCN)
2
,
2
and PdCl -
1
6
56
H -
(MeCN)
2
were prepared according to the reported methods. Other
chemicals were purchased and used without further purification. Details
of X-ray crystallography are included in Supporting Information.
7
O1.5Pd (5a‚(MeOH)0.5): C, 57.63; H, 8.10; N, 14.05. Found: C,
5
7.42; H, 7.86; N, 14.35.
2
iPr2)(py)Pd-OPh (5b): Reaction of 1a with
2
iPr
Preparation of (K -Tp
Preparation of (K -Tp
0.80 mL, 9.9 mmol) to a CH
804 mg, 2.10 mmol) caused an immediate color change from red-
(py) ) appeared.
(1.07 g, 2.12 mmol) was added to the mixture, and the
2
)(py)Pd-Cl (3a). Addition of pyridine
PhOH. A mixture of 1a (114 mg, 0.171 mmol) and PhOH (20 mg,
(
(
2
Cl solution (25 mL) of PdCl (PhCN)
2
2
2
0
2 2
.21 mmol) dissolved in CH Cl (2 mL) was stirred for 35 min at
ambient temperature. Removal of the volatiles under reduced pressure
and washing the residue with hexane gave 5b (73 mg, 0.098 mmol,
brown to pale-yellow, and a yellow precipitate (PdCl
2
2
iPr
Then KTp
2
7
57% yield) as yellow solids. Anal. Calcd for C38H56BN OPd: C, 61.32;
resultant mixture was stirred for 1 h at room temperature. After removal
of insoluble materials by filtration through a Celite plug, the volatiles
of the filtrate were removed under reduced pressure. The residue was
washed with hexane and crystallized from CH
crystals (722 mg, 1.05 mmol, 50% yield). Anal. Calcd for C32
ClPd: C, 55.98; H, 7.50; N, 14.28. Found: C, 56.49; H, 7.61; N, 14.35.
H, 7.60; N, 13.18. Found: C, 60.77; H, 7.53; N, 13.16.
2
iPr
2
Preparation of (K -Tp
AcOH. A mixture of 1a (70 mg, 0.105 mmol) and AcOH (7 mL, 0.12
mmol) dissolved in CH Cl (2 mL) was stirred for 2 h at ambient
temperature. Removal of the volatiles under reduced pressure, extraction
with CH Cl -hexane, filtration through a Celite pad, and crystallization
gave 5c (34 mg, 0.0477 mmol, 46% yield) as a pale-yellow solid. Anal.
Calcd for C34 Pd: C, 57.50; H, 7.68; N, 13.81. Found: C,
8.58; H, 7.83; N, 13.49.
)(py)Pd-OAc (5c): Reaction of 1a with
3
CN to give 3a as yellow
2
2
H51BN -
7
2
iPr ,Br
2
2
2
Preparation of (K -Tp
)(py)Pd-Cl (3b). Following the pro-
(PhCN) (523 mg, 1.36 mmol),
cedure described for 3a using PdCl
2
2
H
7 2
54BN O
5
(
14) Kitajima, N.; Fujisawa, K.; Fujimoto, C.; Moro-oka, Y.; Hashimoto,
iPr ,Br
2
Preparation of (Tp
2
)PdOAc(AcOH) (6): Reaction of 4 with
S.; Kitagawa, T.; Toriumi, K.; Tatsumi, K.; Nakamura, A. J. Am.
Chem. Soc. 1992, 114, 1277.
15) Anderson, G. K.; Lin, M. Inorg. Synth. 1990, 28, 61.
16) Doyle, J. R.; Slade, P. E.; Jonassen, H. B. Inorg. Synth. 1960, 6, 218.
AcOH. A toluene solution (2 mL) of 2 (93 mg, 0.076 mmol) and AcOH
(18 mL, 0.31 mmol) was stirred for 20 min at room temperature. After
removal of the volatiles under reduced pressure the residue was
(
(

2102 Inorganic Chemistry, Vol. 39, No. 10, 2000
Akita et al.
crystallized from pentane to give 6 as pale-yellow crystals (52 mg,
Preparation of (TpMe2)(nicotine)Pd-Cl (8). Nicotine (235 mL, 1.46
0
.70 mmol, 45% yield). Anal. Calcd for C33 Pd: C, 52.76;
H
57BN
6
O
6
mmol) was added to a CH
mg, 1.46 mmol). After the solution was stirred for 5 min, TlTp
2
Cl
2
solution (15 mL) of PdCl
2
(MeCN)
2
(379
(500
Me
H, 7.66; N, 11.19. Found: C, 52.38; H, 7.76; N, 11.10.
2
iPr
Dinuclear intermediates (µ-OH)(µ-OAc)(PdTp
2
)
2
and (µ-OAc)
were adventitiously obtained from reaction of 2 with 1-2
equiv of acetic acid and characterized spectroscopically. Analytically
2
-
mg, 1.46 mmol) was added and the resulting mixture was stirred for 3
h at room temperature. The resultant TlCl was removed by filtration
through a Celite pad. Concentration to ca. 2 mL followed by addition
of hexane gave pale-yellow precipitates. The supernatant solution was
removed via a syringe, and the residue was washed with hexane twice.
iPr
(
PdTp
2
)
2
iPr
pure samples could not be obtained. For (µ-OH)(µ-OAc)(PdTp
2
) ,
2
1
H NMR (in CDCl
-pz
3
at -20 °C): δ
-H), 3.75, 3.37, 3.20, 3.14 (2H × 4, sept, J ) 7 Hz, CHMe
.44 (4H, sept, J ) 7 Hz, CHMe ), 1.85 (3H, s, CH
H
6.00, 5.72, 5.61 (s × 3, 2H × 3,
iPr
4
2
2
),
Crystallization from MeCN gave 8 as pale-yellow solids (593 mg, 68%
3
(
2
3
COO), -2.56
1
yield). H NMR (CDCl
3
H
at room temperature): δ 5.93, 5.84, 5.75
-
1
1H, s, OH). IR: 2489 (νBH), 1537 (νpz), 1566, 1418 cm (νCdO). For
Me
Me
2
(
8
7
1H × 3, br s × 3, 4-pz
2
-H), 1.5-2.6 (3H × 6, d, Me) (Tp
),
iPr
1
(
µ-OAc)
2
(PdTp
2
)
2
, H NMR (in CDCl
3
at -20 °C): δ
H
6.34 (s, 2H,
.70 (1H, s, o′-py), 8.61 (1H, d, J ) 4.9 Hz, o-py), 7.81 (1H, d, J )
iPr
iPr
4
1
-pz
393 cm (νCdO).
Preparation of (TpiPr2)(nicotine)Pd-Cl (7). Nicotine (91 mL, 0.566
Cl solution (10 mL) of PdCl (MeCN) (147
mg, 0.566 mmol). After the solution was stirred for 5 min, KTp
285 mg, 0.566 mmol) was added and the resulting mixture was stirred
2
-H), 5.82 (s, 4H, 4-pz
2
), 1.84 (6H, s, CH
3
COO × 2). IR: 1564,
.3 Hz, p-py), 2.60 (3H, s, NMe) (nicotine). Other signals overlapped
-
1
-1
with each other and could not be analyzed. IR (KBr): 2460 cm (νBH).
Anal. Calcd for C22 ClPd: C, 49.93; H, 6.03; N, 18.64. Found:
H36BN
8
mmol) was added to a CH
2
2
2
2
iPr
C, 49.60; H, 6.15; N, 18.60.
2
(
Acknowledgment. We are grateful to the Ministry of
Education, Science, Sports, and Culture of the Japanese Govern-
ment for financial support of this research (Grants-in-Aid for
Scientific Research, Nos. 08102006 and 11228201). C.M.-K.
thanks the DAAD (German Academic Exchange Service) for a
scholarship.
for 1 h at room temperature. Resultant TlCl was removed by filtration
through a Celite pad. After filtration through a Celite pad, the volatiles
under reduced pressure and the yellow oily residue were dissolved in
iPr
hexane. Stirring the mixture for 1 h caused precipitation of Tp
2
Pd-
iPr
(
°
pz
C for 3 weeks gave 7 as a trace amount of yellow crystals. H NMR
CDCl at room temperature): δ
2
-H)Cl. Filtration, concentration to ca. 2 mL and cooling at -70
1
(
4
7
3
H
5.97, 5.82, 5.68 (1H × 3, s × 3,
), 8.66 (1H, s, o′-py), 8.57 (1H, d, J ) 5.7 Hz, o-py),
.75 (1H, d, J ) 6.3 Hz, p-py), 7.13 (1H, t, J ) 6.6 Hz, µ-py) (nicotine).
iPr
iPr
2
-pz
2
-H) (Tp
Supporting Information Available: Experimental details of X-ray
crystallography. This material is available free of charge via the Internet
at http://pubs.acs.org.
Other signals overlapped with each other and could not be analyzed.
-
1
(
With CDCl
Anal. Calcd for C37
C, 57.62; H, 7.98; N, 14.14.
3
at -40 °C, see Figure 4.) IR (KBr): 2479 cm (νBH).
H
60BN
8
ClPd: C, 57.74; H, 7.86; N, 14.56. Found:
IC991034E