Synthesis and characterization of proximal dinuclear complexes of palladium supported by 2,6-bis(arylimino)phenoxy (aryl = 2,6-diisopropylphenyl and 2,4,6-tri-tert-butylphenyl) and 3,6-bis(imino(2,6-diisopropylphenyl))pyridazine ligands

Article abstract of DOI:10.1021/om900043u

Two kinds of binucleating ligands, 2,6-bis(arylimino)phenoxy (1a: aryl = 2,6-diisopropylphenyl; 1b: aryl = 2,4,6-tri-tert-butylphenyl) and 3,6-bis(imino(2,6-diisopropylphenyl))pyridazine (2), were prepared, and their proximal complexation with two palladi

Full text of DOI:10.1021/om900043u

3256
Organometallics 2009, 28, 3256–3263
Synthesis and Characterization of Proximal Dinuclear Complexes of
Palladium Supported by 2,6-Bis(arylimino)phenoxy (aryl )
2,6-diisopropylphenyl and 2,4,6-tri-tert-butylphenyl) and
3,6-Bis(imino(2,6-diisopropylphenyl))pyridazine Ligands
Kouji Ohno, Kenji Arima, Shinji Tanaka, Tsuneaki Yamagata, Hayato Tsurugi, and
Kazushi Mashima*
Department of Chemistry, Graduate School of Engineering Science, Osaka UniVersity,
Toyonaka, Osaka 560-8531, Japan
ReceiVed January 19, 2009
Two kinds of binucleating ligands, 2,6-bis(arylimino)phenoxy (1a: aryl ) 2,6-diisopropylphenyl; 1b:
aryl ) 2,4,6-tri-tert-butylphenyl) and 3,6-bis(imino(2,6-diisopropylphenyl))pyridazine (2), were prepared,
and their proximal complexation with two palladium atoms was studied. Treatment of the sodium
compounds of 1a,b with 2 equiv of PdCl2(PhCN)2 and PdMeCl(cod) afforded the corresponding
homobimetallic complexes, [2,6-bis(arylimino)phenoxy][RPd(µ-Cl)PdR] (4a: R ) Cl, aryl ) 2,6-
diisopropylphenyl; 4b: R ) Cl, aryl ) 2,4,6-tri-tert-butylphenyl; 7a: R ) Me, aryl ) 2,6-diisopropylphenyl;
7b: R ) Me, aryl ) 2,4,6-tri-tert-butylphenyl), whose structures were characterized spectroscopically
and crystallographically. In the reaction between the sodium compound of 1a with 1 equiv of
PdCl2(PhCN)2, we detected the NaCl adduct of mononuclear palladium species 5a, which, upon release
of NaCl, formed a dimeric complex, ([2,6-bis(2,6-diisopropylphenylimino)phenoxy](PdCl])2 (4a), as
confirmed by X-ray analysis. Complexation of 2 with 2 equiv of PdCl2(PhCN)2 and PdMeCl(cod) in the
presence of 1 equiv of AgBF4 resulted in the formation of the corresponding cationic complexes ([3,6-
bis(imino(2,6-diisopropylphenyl))pyridazine][RPd(µ-Cl)PdR])(BF4) (9a: R ) Cl; 9b: R ) Me), whose
RPd(µ-Cl)PdR skeletons (R ) Cl and Me) were revealed spectroscopically and crystallographically.
positions are anticipated to be one of the most fundamental
entities to exhibit a cooperative effect, accelerating catalytic
activity, improving selectivity, and promoting unexpected
reactivity, and not a simple extension of a single metal complex.
This recent development is due to a rational design of different
types of ligands to fix two metal centers in proximity to
cooperatively catalyze any targeted organic transformation,
through application of the unique bridging ability of hydride
and sulfur atoms for dinuclear ruthenium systems used to
catalyze unique transformations of propargyl substrates9 and
dehydrogenative coupling of substituted pyridines.10 The clear
advantage of dinuclear complexes was demonstrated by Stanley
et al. in the highly regioselective hydroformylation of olefins
catalyzed by a dirhodium complex bridged by a tetraphosphine
ligand.11,12 Another phosphine-based ligand system was reported
by Tsukada and Inoue whose dinuclear palladium catalysts,
supported by a unique N,N′-bis[(2-diphenylphosphino)phenyl]-
formamidate ligand, catalyzed cis-hydroarylation of alkynes with
unactivated arenes in the presence of trialkylborane.13,14 Pyra-
zolate ligands with armed functional groups have been used to
support two metal centers.15,16 Recently Akita et al. developed
a unique 3,5-bis((diphenylphosphino)methyl)pyrazolato) ligand
system for stoichiometrically activating alkyne substrates.17-19
Some binucleating bisphenoxy ligands have been designed to
Introduction
Assembled metal clusters supported by well-designed mul-
tidentate ligands have recently attracted considerable interest
because of their potential catalytic applications to any organic
transformation.1-8 Although many compounds of main group
elements act as ambifunctional cooperative catalysts, dinuclear
complexes bearing two transition metal centers at the proximal
* Corresponding author. E-mail: mashima@chem.es.osaka-u.ac.jp. Fax:
81-6-6850-6245.
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10.1021/om900043u CCC: $40.75
2009 American Chemical Society
Publication on Web 04/24/2009

Proximal Dinuclear Complexes of Palladium
Organometallics, Vol. 28, No. 11, 2009 3257
proximally bind two aluminum atoms.6-8,20 These developments
prompted us to design and prepare new proximal ligand systems
to maintain the two metal centers at one side of the ligand. Our
strategy was based on the use of a standard two-armed phenoxy
moiety5,21-27 and the skeleton of pyridazine modified with two
arms,28-30 and we herein report the synthesis and characteriza-
tion of dinuclear palladium complexes of 2,6-di(aryliminom-
ethyl)-4-methylphenol (aryl ) 2,6-diisoproplyphenyl (1a)31 and
2,4,6-tri-tert-butylphenyl (1b)) and 3,6-bis(imino(2,6-diisopro-
pylphenyl))pyridazine (2).
Figure 1. Structure of complex 4a with the numbering scheme.
Cocrystallized CH2Cl2 molecule and hydrogen atoms are omitted
for clarity. One of the two molecules in the asymmetric unit.
Figure 2. Structure of complex 4b with the numbering scheme.
Hydrogen atoms are omitted for clarity.
Crystals of complexes 4a and 4b suitable for X-ray analysis
were grown from a mixture of dichloromethane and hexane.
Figures 1 and 2 show the molecular structures of complexes
4a and 4b, respectively, and the selected bond lengths and angles
of 4a and 4b are summarized in Table 1. Complexes 4a and 4b
are isomorphic except for the substituents at the aromatic
moieties bound to the nitrogen atoms. The two palladium centers
are doubly bridged by the oxygen atom of the ligand and the
chlorine atom. In complexes 4a and 4b, each geometry around
Results and Discussion
Synthesis of Dinuclear Palladium Complexes of
2,6-Bis(arylimino)phenoxy Ligands. Reaction of 3a, which
was derived from 1a and NaH in THF, with 2 equiv of
PdCl2(PhCN)2 in toluene afforded dinuclear palladium complex
4a as an orange powder (eq 1). In the same procedure, palladium
complex 4b was obtained by the reaction of 3b and 2 equiv of
PdCl2(PhCN)2.
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Complexes 4a and 4b were characterized by spectral data
and elemental analysis along with single-crystal X-ray analyses.
In the FAB-MS spectrum of 4a, a parent ion peak was observed.
In the reaction of 3a and PdCl2(PhCN)2, two new resonances
due to CH3 in the isopropyl groups of 4a appeared at δ 1.48
and 1.15. The formation of the dinuclear palladium complex
4a resulted in the differentiation of nonequivalent CH3 in the
isopropyl groups; one was oriented toward the imine moiety
and the other opposite of it. The resonance due to the two imine
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protons overlapped with the aromatic signals. The H NMR
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spectrum of 4b was also consistent with the symmetric pattern
due to the formation of the dinuclear palladium, displaying a
singlet due to the imine proton at δ 7.50 and two singlets due
to two tert-butyl groups at δ 1.69 and 1.23.

3258 Organometallics, Vol. 28, No. 11, 2009
Ohno et al.
Scheme 1. Proposed Reaction Mechanism
Table 1. Selected Bond Distances (Å) and Angles (deg) of 4
4a
4b
Pd1-N1
1.977(6)
2.012(6)
2.063(4)
2.042(5)
2.2650(16)
2.2493(19)
2.3125(18)
2.3219(17)
1.302(7)
93.0(2)
1.997(5)
2.018(4)
2.046(4)
2.065(4)
Pd2-N2
Pd1-O1
Pd2-O1
Pd1-Cl1
2.2677(15)
2.2716(15)
2.3409(15)
2.3300(15)
1.333(7)
93.55(18)
93.96(17)
93.70(14)
93.19(14)
82.67(12)
82.54(11)
90.24(5)
90.40(5)
105.63(18)
89.03(5)
127.1(3)
127.0(3)
Pd2-Cl3
Pd1-Cl2
Pd2-Cl2
C1-O1
N1-Pd1-O1
N2-Pd2-O1
N1-Pd1-Cl1
N2-Pd2-Cl3
O1-Pd1-Cl2
O1-Pd2-Cl2
Cl1-Pd1-Cl2
Cl3-Pd2-Cl2
Pd1-O1-Pd2
Pd1-Cl2-Pd2
C1-O1-Pd1
C1-O1-Pd2
92.9(2)
93.54(16)
93.42(18)
83.57(13)
83.80(13)
89.92(6)
90.07(7)
103.97(19)
88.50(6)
128.3(4)
127.3(4)
between palladium metal and the noninnocent redox-active
ligand 1, may explain the paramagnetic nature of 5a, as we
observed very broad signals due to the presence of paramagnetic
1
species in the H NMR spectrum of in situ generated 5a in
CDCl3.
the two palladium atoms is slightly distorted square planar. In
complex 4a, the geometries around two palladium centers are
essentially the same except for the distance of the Pd-N bond:
the distance of Pd(1)-N(1) [1.977(6) Å] is slightly shorter than
that of Pd(2)-N(2) [2.012(6) Å]. The terminal Pd-Cl distances
of Pd(1)-Cl(1) [2.2677(15) Å] and Pd(2)-Cl(3) [2.2716(15)
Å] are shorter than those of the bridged Pd-Cl distances of
Pd(1)-Cl(2) [2.3409(15) Å] and Pd(2)-Cl(2) [2.3300(15) Å].32
A similar trend was observed in 4b.
To gain insight into the reaction pathways of 3a and 3b with
2 equiv of PdCl2(PhCN)2, a controlled experiment was con-
ducted. As outlined in Scheme 1, complex 3a reacted with 1
equiv of PdCl2(PhCN)2 in toluene at room temperature to give
the mononuclear compound 5a, which further reacted with
another equivalent of PdCl2(PhCN)2 to give the dinuclear
palladium complex 4a in quantitative yield. Because complex
5a was coordinatively unsaturated, we anticipated that the
coordination site was occupied by a salt, NaCl, with a bridged
phenolic oxygen atom. The partial contribution of the radical
character of the ligand, due to the partial electron transfer
To elucidate the structure of 5a, another controlled experiment
was conducted. The sodium compound 3a reacted with 1 equiv
of PdCl2(PhCN)2 in acetonitrile at room temperature gave the
new dimer complex 6a (eq 2) after the release of NaCl. The
isolated complex 6a did not react with another equivalent of
PdCl2(PhCN)2, presumably due to the stability of the dimer
structure, which was in sharp contrast to the observation that
the one-pot reaction of 3a with 2 equiv of PdCl2(PhCN)2 in
acetonitrile gave the dinuclear palladium complex 4a in
1
quantitative yield. Complex 6a was characterized by H and
13C NMR, mass spectroscopies, and a single-crystal X-ray
analysis. Similarly, a palladium enolate complex readily dimer-
ˆ
ized to form a stable dinuclear complex ([N N]PdCH2C(dO)-
ˆ
OCH3)2 (N N ) 1-[1-(5-methylpyrrole-2-yl)ethylidne]amino-
2,6-diisopropylbenzene) bridged by the C,O-enolato groups.33
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In the H NMR spectrum of 6a in CDCl3, four doublets
(δ 1.40, 1.35, 1.08, and 0.97) assigned to protons of CH3 in the
isopropyl group were observed. Resonances due to two non-
equivalent imine protons (Ha or Hb) appeared at δ 10.28 and in
the aryl region, respectively. The IR spectrum showed two sharp
bands at 1635 and 1617 cm-1, due to the CdN stretching
vibration.
Crystals of 6a suitable for an X-ray analysis were grown from
hexane at room temperature. Figure 3 shows the molecular
structure of 6a, and selected bond lengths and angles of 6a are
summarized in Table 2. In the solid state, there are two types
of hydrogen bonds between the hydrogen atom in the ethylene
group and the hydrogen atom in the phenolic oxygen [O(1)-H(7)
) 2.27 Å and O(1*)-H(7) ) 2.09 Å]. The sum of the van der
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1462.

Proximal Dinuclear Complexes of Palladium
Organometallics, Vol. 28, No. 11, 2009 3259
Treatment of 3a with 2 equiv of (cod)PdMeCl in toluene
afforded dinuclear dimethyl palladium complex 7a as a yellow
powder in quantitative yield. Based on 1H and 13C NMR spectral
data, dinuclear palladium complex 7a has two methyl groups
bound to each palladium atom, and the chlorine atom and
oxygen atom of the phenolic spacer act as bridging ligands:
methyl protons and methyl carbons appeared at δH 0.12 and
δC -2.1, respectively, indicating that each methyl group is
bound directly to each palladium atom as a terminal ligand.
Complex 7b was also prepared according to the same procedure
as 7a in quantitative yield. The µ-Cl bridge is quite stable, and
the chloride could not be displaced even upon treatment with
AgBF4.
Figure 3. Structure of complex 6a with the numbering scheme.
Hydrogen atoms are omitted for clarity. One of the two moleclues
in the asymmetric unit. Symmetry transformations used to generate
equiv atoms (atom name *): -x, -y, -z.
Figure 4. Structure of complex 7a with the numbering scheme.
Cocrystallized hexane molecule and hydrogen atoms are omitted
for clarity.
Table 2. Selected Bond Distances (Å) and Angles (deg) of 6a
Figure 4 shows the molecular structure of dinuclear methyl
palladium complex 7a, and selected bond lengths and angles
are summarized in Table 3. The terminal Pd-C distance of
Pd(1)-C(34) [2.006(2) Å] is shorter than that of Pd(2)-C(35)
[2.0220(19) Å]. Other bond distances around Pd(1) [2.0217(16),
2.1243(13), and 2.3453(5) Å] for Pd(1)-N(1), Pd(1)-O(1), and
Pd(1)-Cl(1), respectively, are almost the same as the bond
distances around Pd(2). Although the Pd(1)-Cl(1) distance of
7a [2.3453(5) Å] is longer than that of 4a [2.3125 (18) Å], the
C(1)-O(1) distance of 7a [1.300(2) Å] is the same as that of
4a [1.302(7) Å]. These features are likely due to the increased
electron density at each palladium atom with a methyl group
in complex 7a.
Reactions of 3a with platinum compounds PtCl2(PhCN)2 and
PtCl2(MeCN)2 and a nickel compound, NiCl2(PPh3)2, did not
give the desired dinuclear products under the same reaction
conditions as palladium; however, in the case of NiClPh(PPh3)2,
the reaction with 3a gave complex 8 as a green powder (eq 4).
Bis-chelated nickel complexes with this type of O,N-ligand,
similar to complex 8, are thermodynamically favored, and their
formation has been discussed in relation to ethylene polymer-
ization catalysts.35-37
Pd1-N1*
Pd1-O1
2.088(4)
2.019(4)
1.304(6)
Pd1-N2
Pd1-Cl1
2.023(4)
2.2850(14)
C1-O1
N1*-Pd1-O1
88.33(16) N2-Pd1-O1
90.71(16)
N1*-Pd1-Cl1 90.18(12) N2-Pd1-Cl1 90.81(13)
C1-O1-Pd1
128.7(3)
Hydrogen Bonding Geometry (Å and deg)
D-H---A
C7-H7---O1
C7-H7---O1*
D-H
0.95(2)
0.95(2)
H---A
2.27(2)
2.09(2)
D---A
2.708(6)
2.795(6)
D-H---A
107.2
129.6
Table 3. Selected Bond Distances (Å) and Angles (deg) of 7a
Pd1-N1
2.0217(16)
2.1243(13)
2.3453(5)
2.006(2)
1.300(2)
91.16(6)
84.43(4)
91.03(6)
93.45(8)
101.34(5)
127.35(12)
Pd2-N2
Pd2-O1
Pd2-Cl1
Pd2-C35
2.0189(16)
2.1294(13)
2.3398(5)
2.0220(19)
Pd1-O1
Pd1-Cl1
Pd1-C34
C1-O1
N1-Pd1-O1
O1-Pd1-Cl1
Cl1-Pd1-C34
C34-Pd1-N1
Pd1-O1-Pd2
C1-O1-Pd1
N2-Pd2-O1
O1-Pd2-Cl1
Cl1-Pd2-C35
C35-Pd2-N2
Pd1-Cl1-Pd2
C1-O1-Pd2
90.62(6)
84.45(4)
90.35(6)
94.58(8)
89.219(17)
127.19(12)
Waals radii of the O and H atoms (2.72 Å)34 is significantly
longer than the observed O-H distances, indicating that Ha
() H7) bridges two oxygen atoms through two hydrogen bonds,
which stabilizes the dimer structure of 6a. The C(1)dC(2)-
C(7)dN(1) sequence adopted an s-transconformation, whereas
that of C(1)dC(6)-C(21)dN(2) was s-cis, despite the fact
that each CdN double bond has an E configuration. The
geometry around the palladium atom is a slightly distorted
square planar.
Complex 8 was crystallized from toluene, and its structure
was measured by X-ray single-crystal structure determination.
1
The H NMR spectrum of 8 in CDCl3 is consistent with this
structure in the solid state. The four diastereotopic protons in
methyl groups are observed at δ 1.43, 1.32, 1.19, and 1.00, and
(35) Connor, E. F.; Younkin, T. R.; Henderson, J. I.; Waltman, A. W.;
Grubbs, R. H. Chem. Commun. 2003, 2272.
(36) Foley, S. R.; Stockland, R. A., Jr.; Shen, H.; Jordan, R. F. J. Am.
Chem. Soc. 2003, 125, 4350.
(37) Waltman, A. W.; Younkin, T. R.; Grubbs, R. H. Organometallics
2004, 23, 5121.
(34) Bondi, A. J. Phys. Chem. 1964, 68, 441.

3260 Organometallics, Vol. 28, No. 11, 2009
Ohno et al.
not coordinate due to steric congestion between the two chlorine
atoms in the possible complex 11. Thus, it is likely that the
abstraction of one chlorine atom from complex 10 by AgBF4
opened a coordination site and then the second PdCl2 moiety
occupied the proximal position to form the chlorine-bridged
dinuclear skeleton. Similarly, proximal dinuclear complexation
with different kinds of supporting ligands is hampered by an
intramolecular contact between the halides bound to the metal
and the second halo metal unit.23-25,27,38
Figure 5. Structure of complex 8 with the numbering scheme.
Hydrogen atoms are omitted for clarity. Symmetry transformations
used to generate equivalent atoms (atom name *): -x, -y, -z.
Table 4. Selected Bond Distances (Å) and Angles (deg) of 8
Ni1-N1
1.896(2)
1.309(3)
93.13(9)
Ni1-O1
1.8588(18)
C1-O1
N1-Ni1-O1
Ni1-O1-C1
N1-Ni1-O1*
86.87(9)
130.15(18)
two imine protons are also observed at δ 7.96 and the aromatic
region, respectively.
Similar treatment of 2 with 1 equiv of PdClMe(cod) at room
temperature produced a mixture of two complexes, 12a and 12b
(major/minor ) 5:2). Treatment of 12a and 12b with 1 equiv
of PdClMe(cod) in the presence of 1 equiv of AgBF4 in
dichloromethane at -78 °C resulted in the quantitative formation
of complex 9b. When this reaction was conducted at room
temperature, we obtained a complicated mixture containing a
black precipitate. The intermediate cationic species derived from
12a and 12b were thermally unstable at room temperature.
Figure 5 shows the molecular structure of complex 8, and its
selected bond lengths and angles are summarized in Table 4.
Complex 8 adopts a distorted square-planar geometry, as
observed for some related nickel complexes.35,36 The distance
of Ni(1)-O(1) [1.8588(16) Å] is shorter than that of Ni(1)-N(1)
[1.896(2) Å], because nickel has strong oxophilicity. In the solid
state, the C(1)dC(2)-C(7)dN(1) sequence adopts an s-trans
conformation, whereas that of C(1)dC(6)-C(9)dN(2) was
s-cis, although each CdN double bond has an E configuration.
The geometry around the nickel atom is square-planar.
Synthesis of Dinuclear Complexes Supported by
3,6-Bis(imino(2,6-diisopropylphenyl))pyridazine (2). Treat-
ment of 2 with 2 equiv of PdCl2(PhCN)2 in the presence of 1
equiv of AgBF4 in CH3CN afforded cationic dinuclear complex
9a in quantitative yield (eq 5). Similarly, reaction of 2 with 2
equiv of PdClMe(cod) in the presence of 1 equiv of AgBF4 in
dichloromethane at -78 °C also afforded cationic complex 9b
in quantitative yield. Complexes 9a and 9b were characterized
Complex 9b was crystallized from a mixture of dichlo-
romethane and hexane. Figure 6 shows the cationic part of the
dinuclear palladium complex 9b, and selected bond distances
and angles are summarized in Table 5. The two palladium atoms
are confirmed to be in the proximal positions bridged by a
chloride anion; the skeleton of Pd1-Cl1-Pd2 has distances of
2.3723(13) Å for Pd1-Cl1 and 2.3733(12) Å for Pd2-Cl1 and
an angle of 100.46(5)°. The difference in the Pd-CH3 bond
1
by H NMR, 13C(1H) NMR, combustion analysis, and X-ray
analyses. These reactions required 1 equiv of AgBF4; otherwise,
the reaction resulted in a complicated mixture and no products
were obtained.
In the control experiment, we first perfomed the reaction of
2 with 1 equiv of PdCl2(PhCN)2 in the absence of AgBF4 to
give mononuclear complex 10, to which the second PdCl2 did
(38) Tsukada, N.; Sato, T.; Mori, H.; Sugawara, S.; Kabuto, C.; Miyano,
S.; Inoue, Y. J. Organomet. Chem. 2001, 627, 121.

Proximal Dinuclear Complexes of Palladium
Organometallics, Vol. 28, No. 11, 2009 3261
spectra were recorded by the use of the following instruments: IR,
Jasco FT/IR-230 and FT/IR-410; UV/vis spectra, Hewlett Packard
HP 8453. Elemental analyses were performed on a Perkin-Elmer
2400 microanalyzer at the Faculty of Engineering Science, Osaka
University. All melting points were recorded on a Yanaco MP-
52982 and were not corrected.
Preparation of Dinuclear Complex 4a. A solution of 4-methyl-
2,6-di(2,6-diisopropylphenyliminometyl)phenol (1a) (2.01 g, 4.16
mmol) in THF (20 mL) was added into sodium hydride (104 mg,
4.31 mmol; 1 equiv relative to 1a) placed in an 80 mL Schlenk
tube. After the reaction mixture was stirred at room temperature
for 1 h, all volatiles were removed under reduced pressure to give
3a (134 mg, 267 µmol), which was dissolved in toluene (4 mL). A
solution of PdCl2(PhCN)2 (207 mg, 557 µmol, 2 equiv relative to
3a) in toluene (14 mL) was added. The reaction mixture was stirred
at room temperature for 12 h and then was filtered through a pad
of Celite eluted with dichloromethane. The resulting solution was
concentrated under reduced pressure, and the resulting product was
recrystallized from a mixture of dichloromethane and hexane at
room temperature to give orange crystals of 4a (69 mg, 32% yield),
mp 297 °C (dec). 1H NMR (300 MHz, CDCl3, 35 °C): δ 7.50-7.13
Figure 6. Cationic part of complex 9b. All hydrogen atoms, solvent
molecules, and tetrafluoroborate anion are omitted for clarity.
Table 5. Selected Bond Distances (Å) and Angles (deg) of 9b
Pd1-C1
2.058(5)
2.048(5)
2.055(6)
2.049(5)
90.64(18)
96.15(15)
90.52(15)
95.80(13)
100.46(5)
124.4(4)
Pd1-Cl1
2.3723(13)
2.096(5)
2.3733(12)
2.093(5)
95.3(2)
77.8(2)
95.6(2)
78.02(19)
123.2(4)
Pd1-N1
Pd1-N2
Pd2-C2
Pd2-N4
Pd2-Cl1
Pd2-N3
C1-Pd1-N1
N1-Pd1-N2
C2-Pd2-N4
N3-Pd2-N4
Pd1-N2-N3
C1-Pd1-Cl1
Cl1-Pd1-N2
C2-Pd2-Cl1
Cl1-Pd2-N3
Pd1-Cl1-Pd2
Pd2-N3-N2
3
(m, 10H, Ar-H, CHdN), 3.53 (sept, JH-H ) 6.9 Hz, 4H,
distance between 9b and 7a is attributed to the trans influence
of the pyridazine ring and phenoxide ligands.
3
CH(CH3)2), 2.32 (s, 3H, CH3), 1.48 (d, JH-H ) 6.9 Hz, 12H,
3
CH(CH3)2), 1.15 (d, JH-H ) 6.9 Hz, 12H, CH(CH3)2). 13C NMR
1
(75 MHz, CDCl3, 35 °C): δ 163.0 (d, JC-H ) 166 Hz, CdN),
Conclusion
1
146.0 (Ar), 145.6 (Ar), 140.8 (Ar), 129.6 (Ar), 129.0 (d, JC-H
)
)
1
We report the syntheses of dinuclear palladium complexes
supported by bis(iminomethyl)phenolate and 3,6-bis(imino(2,6-
diisopropylphenyl))pyridazine ligands, which were designed to
act as proximal ligands. Two palladium atoms were bridged by
a chlorine atom, forming an R-Pd(µ-Cl)Pd-R skeleton where
R ) Cl and CH3 for both ligand systems. For the phenolate
ligands, the dinuclearization proceeds through the NaCl adduct
5a and removal of the salt led to the formation of dimer
compounds 4a and 4b. In the case of the pyridazine ligand,
two palladium metals successively coordinated to the ligand only
in the presence of AgBF4. Abstraction of the chlorine atom
bound to the palladium was key to generating the vacant site to
allow the second palladium halide moiety approach, resulting
in the chlorine-bridged dinuclear complexes.
161 Hz, Ar), 128.3 (Ar), 123.5 (Ar), 119.3 (Ar), 29.0 (d, JC-H
127 Hz, CH(CH3)2), 24.7 (q, 1JC-H ) 121 Hz, CH(CH3)2), 23.1 (q,
1JC-H ) 121 Hz, CH(CH3)2), 19.6 (Ar-CH3). IR (KBr ν in cm-1):
1623 (CdN). UV/vis [CH2Cl2, λ in nm (ꢀ in cm-1 M-1)]: 412
(4.0 × 103). MS (FAB): m/z 800 (M+). Anal. Calcd for
C33H41Cl3N2OPd2(CH2Cl2)0.5: C, 47.71; H, 5.02; N, 3.32. Found:
C, 47.87; H, 5.09; N, 3.28.
Preparation of Dinulcer Complex 4b. To the sodium compound
3b (205 mg, 304 µmol) in toluene (5 mL) was added a solution of
PdCl2(PhCN)2 (247 mg, 643 µmol) in toluene (5 mL) at room
temperature. After the mixture was stirred for 12 h, the reaction
solution was filtered through a Celite pad eluted with dichlo-
romethane. The solvent was concentrated under reduced pressure,
and the resulting product was recrystallized from a mixture of
dichloromethane and hexane at room temperature to give orange
1
crystals of 4b (236 mg, 80% yield), mp 244 °C (dec). H NMR
Experimental Section
(300 MHz, CDCl3, 35 °C): δ 7.60-7.18 (m, 6H, Ar), 7.50 (s, 2H,
CHdN), 2.23 (s, 3H, CH3), 1.69 (s, 36H, C(CH3)3), 1.23 (s, 18H,
General Procedures. All manipulations involving air- and
moisture-sensitive organometallic compounds were carried out by
using the standard Schlenk techniques under an argon atmosphere.
Hexane, THF, toluene, and diethyl ether were dried over sodium
benzophenone ketyl and then distilled prior to use. Ethanol and
methanol were distilled from magnesium alkoxide. Dehydrated
dichloromethane and acetonitrile were purchased from Wako
Chemical and degassed. Palladium and nickel complexes,
PdCl2(PhCN)2,39 PdMeCl(cod),40 and NiClPh(PPh3)2,41 were pre-
pared following the literature procedures. 4-Methyl-2,6-di(2,6-
diisopropylphenyliminomethyl)phenol (1a) was prepared according
to the literature procedure.31 Syntheses of 4-methyl-2,6-di(2,4,6-
tri-tert-butylphenyliminometyl)phenol (1b) and 3,6-bis(imino(2,6-
diisopropylphenyl))pyridazine (2) are given in the Supporting
Information. Other chemicals were purchased and used as received.
Nuclear magnetic resonance [1H (300 MHz), 13C (75 MHz)]
spectra were measured on a Varian Mercury300-C/H. Mass spectra
were measured on a JEOL JMS-700 mass spectrometer. Other
C(CH3)3). 13C NMR (75 MHz, CDCl3, 35 °C): δ 164.1 (d, 1JC-H
)
172 Hz, CdN), 148.6 (Ar), 145.5 (Ar), 140.5 (Ar), 132.6 (Ar),
1
3
132.1 (Ar), 129.0 (dd, JC-H ) 154 Hz, JC-H ) 6 Hz, Ar), 124.4
(d, 3JC-H ) 7 Hz, Ar), 118.9 (d, 3JC-H ) 8 Hz, Ar), 37.8 (C(CH3)3),
35.1 (C(CH3)3), 32.8 (q, 1JC-H ) 126 Hz, C(CH3)3), 31.4 (q, 1JC-H
) 126 Hz, C(CH3)3), 19.6 (q, 1JC-H ) 127 Hz, Ar-CH3). IR (KBr
ν in cm-1): 1620 (CdN). UV/vis [CH2Cl2, λ in nm (ꢀ in cm-1
t
M-1)]: 406 (1.4 × 104). MS (FAB): m/z 897 (M+ - Bu - CH3),
755 (M+ - 3tBu - 3CH3). Anal. Calcd for C45H65Cl3N2OPd2-
(H2O)1.5: C, 54.25; H, 6.88; N, 2.81. Found: C, 54.63; H, 7.20; N,
3.29.
Detection of in Situ Generated 5a. To the sodium compound
3a (31 mg, 62 µmol) in toluene (3 mL) was added a solution of
PdCl2(PhCN)2 (25 mg, 67 µmol) in toluene (3 mL) at room
temperature. After the mixture was stirred for 12 h, toluene was
removed under reduced pressure to give 5a as brown powders,
whose NMR could not be observed.
Preparation of Dimer Complex 6a. To the sodium compound
3a (178 mg, 352 µmol) in acetonitrile (20 mL) was added a solution
of PdCl2(PhCN)2 (135 mg, 351 µmol) in acetonitrile (10 mL) at
room temperature. After the mixture was stirred for 12 h, the
reaction solution was concentrated under reduced pressure. The
residue was washed with hexane to give 6a as orange powders.
(39) Doyle, J. R.; Slade, P. E.; Jonassen, H. B. Inorg. Synth. 1960, 6,
218.
(40) Rulke, R. E.; Ernsting, J. M.; Spek, A. L.; Elsevier, C. J.; van
Leeuwen, P. W. N. M.; Veieze, K. Inorg. Chem. 1993, 32, 5769.
(41) Hidai, M.; Kashiwagi, T.; Ikeuchi, T.; Uchida, Y. J. Organomet.
Chem. 1971, 30, 279.

3262 Organometallics, Vol. 28, No. 11, 2009
Ohno et al.
The resulting product was recrystallized from dichloromethane to
give orange crystals (185 mg, 150 µmol, 43% yield), mp 284 °C.
1H NMR (300 MHz, CDCl3, 35 °C): δ 10.28 (s, 2H, CHdN),
7.43-7.01 (m, 20H, Ar, CHdN), 3.48s3.42 (m, 8H, CH(CH3)2),
1.76 (s, 6H, CH3), 1.40 (d, 3JH-H ) 6.9 Hz, 12H, CH(CH3)2), 1.35
a solution of NiClPh(PPh3)2 (1.34 g, 1.90 mmol) in toluene (15
mL). The reaction mixture was stirred at room temperature for 12 h,
and then toluene was removed under reduced pressure to give green
powders. The resulting product was recrystallized from hexane to
give green crystals (451 mg, 441 µmol, 98% yield), mp 251 °C
(dec). 1H NMR (300 MHz, CDCl3, 35 °C): δ 7.96 (s, 1H, CHdN),
3
3
(d, JH-H ) 6.9 Hz, 12H, CH(CH3)2), 1.08 (d, JH-H ) 6.9 Hz,
3
3
12H, CH(CH3)2), 0.97 (d, JH-H ) 6.9 Hz, 12H, CH(CH3)2). 13C
7.27s7.09 (m, 12H, Ar, CHdN), 6.85 (s, 1H, Ar), 6.62 (d, JH-H
3
NMR (75 MHz, CDCl3, 35 °C): δ 165.0 (d, 1JC-H ) 149 Hz, CdN),
163.9 (d, 1JC-H ) 149 Hz, CdN), 163.1, 149.1, 145.2, 141.5, 140.7,
139.1, 139.0, 128.9, 128.1, 126.8, 125.2, 123.6, 123.3, 122.8, 121.7,
) 7.7 Hz, 2H, Ar), 5.83-5.75 (m, 2H, Ar), 4.31 (sept, JH-H
)
6.6 Hz, 2H, CH(CH3)2), 2.60 (sept, 3JH-H ) 6.9 Hz, 2H, CH(CH3)2),
3
2.18 (s, 3H, CH3), 1.43 (d, JH-H ) 6.9 Hz, 6H, CH(CH3)2), 1.32
(d, 3JH-H ) 6.6 Hz, 6H, CH(CH3)2), 1.19 (d, 3JH-H ) 6.9 Hz, 6H,
1
and 119.0 (Ar), 28.8 (d, JC-H ) 136 Hz, CH(CH3)2), 28.7 (d,
CH(CH3)2), 1.00 (d, JH-H ) 6.6 Hz, 6H, CH(CH3)2). 13C NMR
3
1JC-H ) 136 Hz, CH(CH3)2), 24.6 (CH(CH3)2), 24.5 (CH(CH3)2),
23.7 (CH(CH3)2), 22.9 (CH(CH3)2), 19.8 (CH3). IR (KBr ν in cm-1):
1635 (CdN), 1617 (CdN). UV/vis [CH2Cl2, λ in nm (ꢀ in cm-1
M-1)]: 431 (1.1 × 104). MS (FAB): m/z 1211(M+ - Cl), 1068
(M+ - 3CH(CH3)2 - Me - Cl + 1). Anal. Calcd for C66H82Cl2N4-
O2Pd2(C6H14)1.4: C, 65.33; H, 7.49; N, 4.10. Found: C, 65.82; H,
7.77; N, 4.59.
1
(75 MHz, CDCl3, 35 °C): δ 165.4 (d, JC-H ) 157 Hz, CdN),
1
160.7 (Ar), 156.2 (d, JC-H ) 170 Hz, CdN), 150.3 (Ar), 145.8
(Ar), 140.9 (Ar), 136.4 (Ar), 146.2 (Ar), 134.1 (Ar), 128.9 (Ar),
128.1 (Ar), 126.5 (d, 1JC-H ) 161 Hz, Ar), 126.4 (Ar), 124.1 (Ar),
1
123.5 (Ar), 122.7 (Ar), 121.8 (Ar), 120.8 (Ar), 29.1 (d, JC-H
)
127 Hz, CH(CH3)2), 27.9 (d, 1JC-H ) 127 Hz, CH(CH3)2), 23.9 (q,
1JC-H ) 125 Hz, CH(CH3)2), 23.7 (q, 1JC-H ) 125 Hz, CH(CH3)2),
Preparation of Dimethyl Dinuclear Complex 7a. To a solution
of 3a (134 mg, 267 µmol) in toluene (4 mL) at room temperature
was added a solution of (cod)PdMeCl (207 mg, 557 µmol) in
toluene (14 mL). The reaction mixture was stirred at room
temperature for 12 h, and then toluene was removed under reduced
pressure. The residue was washed with hexane to give 6a as a
1
1
23.5 (q, JC-H ) 125 Hz, CH(CH3)2), 22.4 (q, JC-H ) 125 Hz,
CH(CH3)2), 19.9 (q, JC-H ) 127 Hz, CH3). IR (KBr ν in cm-1):
1
1622 (CdN), 1598 (CdN). UV/vis [CH2Cl2, λ in nm (ꢀ in cm-1
M-1)]: 469 (1.2 × 104), 354 (1.8 × 104). MS (FAB): m/z 1021
(M+ - H), 979 (M+ - H - CH(CH3)2), 834 (M+ - CH3 - 3CH-
(CH3)2). We could not obtain a satisfactory elemental analysis due
to the contamination of triphenylphosphine oxide.
1
yellow powder in quantitative yield, mp 169 °C (dec). H NMR
(300 MHz, C6D6, 35 °C): δ 7.60 (s, 2H, CHdN), 7.20s7.04 (m,
6H, Ar), 6.62 (s, 2H, Ar), 3.60 (qq, 3JH-H ) 6.9 Hz, 4H, CH(CH3)2),
1.83 (s, 3H, CH3), 1.24 (d, 3JH-H ) 6.9 Hz, 12H, CH(CH3)2), 1.00
(d, 3JH-H ) 6.9 Hz, 12H, CH(CH3)2), 0.67 (s, 6H, PdCH3). 1H NMR
(300 MHz, CDCl3, 25 °C): δ 7.86 (s, 2H, CHdN), 7.26-7.17 (m,
Preparation of Dinuclear Complex 9a. A solution of AgBF4
(129.8 mg, 0.67 mmol) and CH3CN (15 mL) was added to a
solution of 2 (300.0 mg, 0.66 mmol) and (PhCN)2PdCl2 (506.2 mg,
1.32 mmol) in CH3CN (15 mL). The reaction mixture was stirred
for 12 h at room temperature. The mixture was extracted with
CH3CN and then filtered to remove AgCl. After evaporation of
the solvent, the orange solid was washed with Et2O. The orange
solid was dried under reduced pressure to give 9a (550.2 mg, 0.64
mmol, 97%), mp 215s219 °C (dec).
3
8H, Ar), 3.60 (qq, JH-H ) 6.9 Hz, 4H, CH(CH3)2), 2.23 (s, 3H,
CH3), 1.33 (d, 3JH-H ) 6.9 Hz, 12H, CH(CH3)2), 1.11 (d, 3JH-H
)
6.9 Hz, 12H, CH(CH3)2), 0.12 (s, 6H, PdCH3). 13C NMR (75 MHz,
C6D6, 35 °C): δ 166.8 (CdN), 148.9 (Ar), 145.2 (Ar), 141.7 (Ar),
128.5 (Ar), 125.7 (Ar), 126.9 (Ar), 124.7 (Ar), 123.3 (Ar), 29.5
(CH(CH3)2), 26.2 (CH(CH3)2), 24.0 (CH(CH3)2), 20.7 (CH3), -0.9
Stepwise synthesis was alternatively conducted. A solution of
AgBF4 (108.1 mg, 0.55 mmol) in CH3CN (5 mL) was added to a
solution of complex 10 (319.0 mg, 0.50 mmol) in CH3CN (10 mL).
The reaction mixture was stirred for 30 min at room temperature.
After a solution of (PhCN)2PdCl2 (193.6 mg, 0.50 mmol) in CH3CN
(10 mL) was added to the resulting red solution, the reaction mixture
was further stirred for 12 h. The filtration was conducted to remove
AgCl. After evaporation of all volatiles, the orange solid was
washed with Et2O and then dried under reduced pressure, yielding
(PdCH3). 13C NMR (75 MHz, CDCl3, 25 °C): δ 165.3 (d, 1JC-H
)
1
164 Hz, CdN), 146.8 (Ar), 144.0 (d, JC-H ) 153 Hz, Ar), 140.0
(Ar), 126.4 (Ar), 124.4 (Ar), 123.7 (Ar), 123.3 (Ar), 121.3 (Ar),
1
1
27.9 (d, JC-H ) 128 Hz, CH(CH3)2), 25.1 (q, JC-H ) 127 Hz,
CH(CH3)2), 22.9 (q, 1JC-H ) 127 Hz, CH(CH3)2), 19.9 (q, 1JC-H
)
1
127 Hz, CH3), -2.1 (q, JC-H ) 127 Hz, PdCH3). IR (KBr ν in
cm-1): 1617 (CdN). UV/vis [CH2Cl2, λ in nm (ꢀ in cm-1 M-1)]:
456 (6.1 × 103). MS (FAB): m/z 729 (M+ - 2CH3), 686 (M+
-
:
1
2CH3 - CH(CH3)2). Anal. Calcd for C35H47ClN2OPd2(C6H14)1.0
9a in 96% yield. H NMR (300 MHz, CD2Cl2, 30 °C): δ 9.30 (s,
C, 47.71; H, 5.02; N, 3.32. Found: C, 47.87; H, 5.09; N, 3.28.
2H, pyridazine), 8.68 (s, 2H, CHdN), 7.22-7.24 (m, 6H, Ar), 3.18
3
3
Preparation of Dimethyl Dinuclear Complex 7b. To a solution
of 3b (134 mg, 267 µmol) in toluene (4 mL) at room temperature
was added a solution of (cod)PdMeCl (207 mg, 557 µmol) in
toluene (14 mL). The reaction mixture was stirred at room
temperature for 12 h, and then toluene was removed under reduced
pressure. The residue was washed with hexane to give 7b as a
(qq, JH-H ) 6.7 Hz, 4H, CH(CH3)2), 1.36 (d, JH-H ) 6.7 Hz,
12H, CH(CH3)2), 1.15 (d, JH-H ) 6.7 Hz, 12H, CH(CH3)2). 13C
3
NMR (75 MHz, CD2Cl2, 30 °C): δ 140.4 (CHdN), 134.9 (NdC-
CH of pyridazine), 132.9 (Ar), 129.1 (Ar), 123.4 (NdC-CH of
pyridazine), 118.3 (Ar), 112.0 (Ar), 29.0 (CH(CH3)2), 23.6
(CH(CH3)2). UV/vis [CH2Cl2, λ in nm (ꢀ in cm-1 M-1)]: 238
(3.6 × 104), 354 nm (1.7 × 104 dm3 mol-1 cm-1). IR (KBr ν in
cm-1): 1083 (B-F), 1652 (CdN). Anal. Calcd for C30H38N4: C,
41.87; H, 4.45; N, 6.51. Found: C, 41.99; H, 4.92; N, 6.50.
Preparation of Mononuclear Complex 10. A solution of
(PhCN)2PdCl2 (337.5 mg, 0.88 mmol) in CH3CN (10 mL) was
added to a solution of 2 (400.0 mg, 0.88 mmol) in CH3CN (15
mL). The reaction mixture was stirred for 12 h at room temperature.
After removal of all volatiles, the resulting orange solid was washed
with Et2O and then dried under reduced pressure to give 10 (467.8
mg, 0.74 mmol, 84%), mp 294s297 °C (dec). 1H NMR (300 MHz,
1
yellow powder in quantitative yield, mp 172 °C (dec). H NMR
(300 MHz, C6D6, 25 °C): δ 7.86 (s, 2H, CHdN), 7.58 (s, 4H, Ar),
6.73 (s, 2H, Ar), 1.86 (s, 3H, CH3), 1.71 (s, 36H, C(CH3)3), 1.31
(s, 18H, C(CH3)3), 0.84 (s, 6H, PdCH3). 13C NMR (75 MHz, C6D6,
1
25 °C): 166.9 (d, JC-H ) 164 Hz, CdN), 159.8, 147.7, 147.1,
1
3
143.8, 139.9, 128.3, 124.1 (dd, JC-H ) 154 Hz, JC-H ) 7 Hz)
1
and 121.0 (Ar), 37.7 (C(CH3)3), 36.0 (C(CH3)3), 31.8 (d, JC-H
)
126 Hz, C(CH3)3), 31.4 (d, 1JC-H ) 126 Hz, C(CH3)3), 19.8 (CH3),
-1.2 (q, JC-H ) 135 Hz, Pd-CH3). IR (KBr ν in cm-1): 1619
1
(CdN). UV/vis [CH2Cl2, λ in nm (ꢀ in cm-1 M-1)]: 452 (1.0 ×
104). MS (EI+): m/z 913 (M+ - CH3), 897 (M+ - 2CH3 - H).
Anal. Calcd for C47H71ClN2OPd2(C6H5CH3)1.8: C, 65.42; H, 7.87;
N, 2.56. Found: C, 65.04; H, 8.37; N, 2.56.
3
CD2Cl2, 30 °C): δ 8.96 (d, JH-H ) 8.5 Hz, 1H, pyridazine), 8.73
3
(s, 1H, CHdN), 8.40 (s, 1H, CHdN), 8.37 (d, JH-H ) 8.5 Hz,
3
1H, pyridazine), 7.22-7.28 (m, 6H, Ar), 3.27 (sep, JH-H ) 6.9
3
Preparation of Nickel Complex 8. To a solution of 3a (453
mg, 902 µmol) in toluene (10 mL) at room temperature was added
Hz, 2H, CH(CH3)2), 2.92 (sept, JH-H ) 6.9 Hz, 2H, CH(CH3)2),
3
1.40 (d, JH-H ) 6.9 Hz, 6H, CH(CH3)2), 1.16-1.20 (m, 18H,

Proximal Dinuclear Complexes of Palladium
Organometallics, Vol. 28, No. 11, 2009 3263
3
CH(CH3)2). 13C NMR (75 MHz, CD2Cl2, 35 °C): δ 166.7, 158.9,
158.8, 158.4, 143.1, 140.8, 137.0, 132.86, 132.85, 129.4, 127.6,
126.0, 123.6, 123.5, 29.1 (CH(CH3)2), 28.3 (CH(CH3)2), 24.3
(CH(CH3)2), 23.2 (CH(CH3)2), 22.9 (CH(CH3)2). Anal. Calcd for
(C30H38N4Cl2Pd2)(H2O): C, 55.43; H, 6.20; N, 8.62. Found: C,
55.82; H, 5.87; N, 8.70. The presence of solvated water molecule
) 6.9 Hz, 12H, CH(CH3)2), 1.11 (d, JH-H ) 6.9 Hz, 6H,
CH(CH3)2), 0.79 (s, 3H, PdMe). Minor isomer: 1H NMR (300 MHz,
3
CDCl3, 25 °C): δ 8.85 (d, JH-H ) 8.5 Hz, 1H, pyridazine), 8.62
3
(s, 1H, CHdN), 8.48 (s, 1H, CH ) N), 8.32 (d, JH-H ) 8.5 Hz,
3
1H, pyridazine), 7.11-7.34 (m, 6H, Ar), 3.18 (sep, JH-H ) 6.9
3
Hz, 2H, CH(CH3)2), 2.88 (sep, JH-H ) 6.9 Hz, 2H, CH(CH3)2),
1
was confirmed by the H NMR.
1.61 (s, 3H, PdMe), 1.31 (d, 3JH-H ) 6.9 Hz, 6H, CH(CH3)2), 1.19
(d, 3JH-H ) 6.9 Hz, 6H, CH(CH3)2), 1.18 (d, 3JH-H ) 6.9 Hz, 12H,
CH(CH3)2). MS (FAB): m/z 609 (M+ - H). Elemental analysis of
the mixture gave a somewhat larger carbon content: Calcd for
C31H41ClN4Pd: C, 60.88; H, 6.78; N, 9.16. Found: C, 61.64; H,
7.79; N, 9.12.
Preparation of Dimethyl Dinucler Complex 9b. A solution of
AgBF4 (272.3 mg, 1.39 mmol, 1.1 equiv) in CH2Cl2 (10 mL) was
added to a solution of 2 (565.6 mg, 1.24 mmol) and PdClMe(cod)
(725.5 mg, 2.73 mmol, 2.2 equiv) in CH2Cl2 (20 mL) at -78 °C.
After the reaction mixture was slowly warmed to room temperature,
it was stirred for 2 h. The reaction mixture was filtered to remove
AgCl. Removal of all volatiles gave an orange solid, which was
washed with hexane and then dried under reduced pressure, yielding
9b (99.2 mg, 1.21 mmol, 98%).
X-ray Crystallographic Analyses. All crystals were handled
similarly. The crystals were mounted on a CryoLoop (Hampton
Research Corp.) with a layer of light mineral oil and placed in a
nitrogen stream at 120(1) K. All measurements were made on a
Rigaku RAXIS RAPID imaging plate area detector with graphite-
monochromated Mo KR (0.71075 Å) radiation. The crystal-to-
detector distance was 127.40 mm. The data were corrected for
Lorentz and polarization effects. Crystal data and structure refine-
ment parameters are summarized in Table S3 (see Supporting
Information). The structure was solved by direct methods (SIR9242
(7a and 8), SIR200243 (4a), SIR200444 (4b and 6a), and SHELXS-
9745 (9b)) and refined on F2 by full-matrix least-squares methods,
using SHELXL-97.45 Non-hydrogen atoms were anisotropically
refined. H-atoms were included in the refinement on calculated
positions riding on their carrier atoms. The function minimized was
Stepwise synthesis was also carried out. A solution of AgBF4
(30.6 mg, 0.16 mmol, 1.2 equiv) in CH2Cl2 (5 mL) was added to
a solution of the mixture of complexes 12a and 12b (76.3 mg, 0.12
mmol) and PdClMe(cod) (33.0 mg, 0.12 mmol) in CH2Cl2 (5 mL)
at -78 °C. The reaction mixture was slowly warmed to room
temperature and then stirred for 2 h. After removal of AgCl by
filtration, the solution was concentrated to leave an orange solid,
which was washed with hexane and then dried under reduced
1
pressure, giving 9b (96.4 mg, 0.12 mmol, 98% yield). H NMR
(300 MHz, CD2Cl2, 25 °C): δ 9.07 (s, 2H, pyridazine), 8.98 (s,
3
2H, CHdN), 7.20s7.40 (m, 6H, Ar), 3.13 (sep, JH-H ) 6.9 Hz,
[∑w(Fo - Fc2)2] (w ) 1/[σ2 (Fo ) + (aP)2 + bP]), where
2
2
4H, CH(CH3)2), 1.31 (d, 3JH-H ) 6.9 Hz, 12H, H CH(CH3)2), 1.18
(d, 3JH-H ) 6.9 Hz, 12H, CH(CH3)2), 0.77 (s, 6H, PdMe). 13C NMR
(75 MHz, CD2Cl2, 25 °C): δ 167.4 (CHdN), 152.8 (NdC-CH of
pyridazine), 142.2 (Ar), 139.0 (Ar), 134.5 (NdC-CH of pyridazine),
128.5 (Ar), 123.4 (Ar), 28.1 (CH(CH3)2), 23.8 (CH(CH3)2), 22.1
(CH(CH3)2), 7.4 (PdMe). UV/vis [CH2Cl2, λ in nm (ꢀ in cm-1
M-1)]: λmax (ꢀ) ) 230 (8.6 × 104), 319 nm (1.7 × 104 dm3 mol-1
cm-1). IR (KBr ν in cm-1): 1059 (B-F), 1634 (CdN). FAB-MS
(m/z): 698 (M+ - ClBF4), 683 (M+ - MeClBF4). Anal. Calcd for
C32H44BClF4N4Pd2: C, 46.88; H, 5.41; N, 6.83. Found: C, 46.94;
H, 5.43; N, 6.59.
P ) (max(Fo2,0) + 2Fc2)/3 with σ2(Fo ) from counting statistics.
2
2
The function R1 and wR2 were (∑||Fo| - |Fc||)/∑|Fo| and [∑w(Fo
- Fc2)2/∑(wFo4)]1/2, respectively. The ORTEP-3 program46 was used
to draw the molecule.
Supporting Information Available: Tabulations of crystal-
lographic data in CIF format for 4a, 4b, 6a, 7a, 8, and 9b; synthesis
and characterization of ligands 1b and 2; tables of crystal data and
refinement parameters for 4a, 4b, 6a, 7a, 8, and 9b. These materials
are available free of charge via the Internet at http://pubs.acs.org.
Preparation of Methyl Mononucler Complexes 12a and
12b. A solution of PdClMe(cod) (105.3 mg, 0.40 mmol) in CH2Cl2
(5 mL) was added to a solution of ligand 2 (180.4 mg, 0.40 mmol)
in CH2Cl2 (5 mL) under argon. The reaction mixture was stirred
for 15 h at room temperature. After evaporation of the solution,
the orange solid was washed with hexane. The orange solid was
dried under reduced pressure, quantitatively giving a mixture of
12a and 12b, mp of the mixture 207-210 °C (dec). Major isomer:
1H NMR(300 MHz, CDCl3, 25 °C): δ 8.79 (s, 1H, CHdN), 8.79
(d, 3JH-H ) 8.5 Hz, 1H, pyridazine), 8.67 (s, 1H, CHdN), 8.32 (d,
3JH-H ) 8.5 Hz, 1H, pyridazine), 7.11-7.34 (m, 6H, Ar), 3.22 (sep,
OM900043U
(42) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Polidori, G. J. Appl. Crystallogr. 1994,
27, 435.
(43) Burla, M. C.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.;
Giacovazzo, C.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 2003, 36,
1103.
(44) Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano,
G. L.; De Caro, L.; Giacovazzo, C.; Polidoria, G.; Spagna, R. J. Appl.
Crystallogr. 2005, 38, 381.
(45) Sheldrick, G. M. SHELXS-97 and SHELXL-97, Programs for
Crystal Structure Analysis (Release 97-2); University of Go¨ttingen: Ger-
many.
3
3JH-H ) 6.9 Hz, 2H, CH(CH3)2), 2.85 (sep, JH-H ) 6.9 Hz, 2H,
CH(CH3)2), 1.27 (d, 3JH-H ) 6.9 Hz, 6H, CH(CH3)2), 1.14 (d, 3JH-H
(46) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.