Self-assembly of Schiff-base palladacycle-based discrete pseudo-macrocycles: Evidence for hemilability of oxalate ligand

Article abstract of DOI:10.1016/j.jorganchem.2014.02.020

Bis-bidentate tetra-coordinated oxalato bridged binuclear Schiff-base palladacycles [Pd{C,N-κ²-(4-R)C₆H ₃CHNC₆H₃-2,6-i-Pr₂] ₂(μ-η²-η²-C₂O _4<

Full text of DOI:10.1016/j.jorganchem.2014.02.020

Journal of Organometallic Chemistry 759 (2014) 37e45
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Self-assembly of Schiff-base palladacycle-based discrete
pseudo-macrocycles: Evidence for hemilability of oxalate ligand
*
Yuchun Jiang, Benzhi Li, Yu Wang, Daliang Liu, Ximing Song, Xiaohong Chang
Liaoning Provincial Key Laboratory for Green Synthesis and Preparative Chemistry of Advanced Materials, College of Chemistry, Liaoning University,
Shenyang 110036, PR China
a r t i c l e i n f o
a b s t r a c t
Bis-bidentate tetra-coordinated oxalato bridged binuclear Schiff-base palladacycles [Pd{C,N-k
2-(4-R)
Article history:
C6H3CH]NC6H3-2,6-i-Pr2]2(
bridged Schiff-base palladacycles [Pd{C,N-
m
-
h2
-
h
2-C2O4) (R ¼ H; OMe) were synthesized. Reactions of
m-oxalato
Received 16 November 2013
Received in revised form
19 February 2014
k
2-(4-R)C6H3CH]NC6H3-2,6-i-Pr2]2(
m
-
h2
-
h
2-C2O4) (R ¼ H;
OMe) with 1,4-bis(diphenylphosphino)butane (dppb) and 1,4-bis(diphenylphosphino)pentane (dppp)
Accepted 26 February 2014
generated discrete pseudo-macrocycles with 1,10-bicoordinated oxalato bridge. Unexpectedly,
bridged Schiff-base palladacycle [Pd(C,N-
2-C6H4CH]NC6H3-2,6-i-Pr2)]2( h2 2-C2O4) reacted with
PPh3 to form unusual bidentate/monodentate tri-coordinated oxalato bridged binuclear cyclopalladated
m-oxalato
k
m- -h
Keywords:
Palladacycle
Pseudo-macrocycle
Self-assembly
complex
[Pd(C,N-
k
2-C6H4CH]NC6H3-2,6-i-Pr2)(PPh3)](
m
-
h2
-h
1-C2O4)[Pd(C-
k
1-C6H4CH]NC6H3-2,6-i-
Pr2)(PPh3)].
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
hemilabile linkers, it seems feasible for the assembly of metalla-
macrocycles via cleavage of the weaker metal-ligand bonds.
Furthermore, it is well known that coordinated oxalato group
shows various possible coordination modes (Chart 1) [36e42]. The
oxalato group as bis-bidentate bridging ligands (Chart 1, b) are
more frequently exhibited [43e48]. In Pd and Pt systems, bridging
bis-bidentate, terminal bidentate and bridging bis-monodentate
bonding modes have been observed for the oxalato group [49e
58]. To our best knowledge, the Pd or Pt compounds structurally
characterized in which the oxalato group acts as bidentate/mono-
dentate bridging ligand (Chart 1, d) have not been reported. Herein,
we describe the synthesis and structure of bis-bidentate tetra-co-
ordinated oxalato bridged binuclear Schiff-base palladacycles [Pd
The formation of discrete supramolecular structure via
coordination-driven self-assembly has become an active area of
research and an important component of supramolecular chemis-
try and nanoscience [1e6]. As a subset of discrete supramolecular
complexes, the assemblies of organometallic supramolecule have
attracted more and more interest because of their potential appli-
cation as promising molecular materials [7e16]. Most of the
discrete metallosupramolecular ensembles are built from metal
palladium or platinum species with cis-coordinated diamines or
diphosphines as supporting ligands that are linked by classical
Werner-type polydentate ligands, such as pyrazine, 4,40-bipyridine,
or 2,4,6-tris(4-pyridyl)-1,3,5-triazine [17e26]. A few phosphorous
and oxygen donor linkers are preferred in directed self-assembly of
metallamacrocycles [18,27e29]. Cyclometallated Pd(II) or Pt(II)
complexes with C,N-donor ligands as corner species have rarely
been used for the construction of metallosupramolecular assem-
blies [30e33]. Moreover, Mirkin and co-workers reported the
synthesis of 2D and 3D supramolecular assemblies using hemilabile
ligands and transition metals [34,35]. Hence, if cyclometallated
{C,N-k m- -h
2-(4-R)C6H3CH]NC6H3-2,6-i-Pr2]2( h2 2-C2O4) and self-
assembly of discrete pseudo-macrocycles with 1,10-bicoordinated
oxalato bridge based on tetra-coordinated oxalato bridged binu-
clear Schiff-base palladacycles. Also we report an unexpected
binuclear Schiff-base palladacycle containing unusual bidentate/
monodentate tri-coordinated oxalato bridge.
Results and discussion
Pd(II) fragments with blocked C,N-donor ligands ([Pd{C,N-k
2-(4-R)
C6H3CH]NC6H3-2,6-i-Pr2}]þ) were bridged by appropriate
Synthesis of bis-bidentate tetra-coordinated oxalato bridged Schiff-
base palladacycles
Recently, we investigated the reactivityof
thiocyanato bridged Schiff-base palladacycles with aromatic N-
m-chloro, m-azido and m-
* Corresponding author. Tel.: þ86 24 62207823; fax: þ86 24 62202380.
E-mail addresses: cxh@lnu.edu.cn, c_x_hong@sina.com (X. Chang).
http://dx.doi.org/10.1016/j.jorganchem.2014.02.020
0022-328X/Ó 2014 Elsevier B.V. All rights reserved.

38
Y. Jiang et al. / Journal of Organometallic Chemistry 759 (2014) 37e45
and d 7.61, respectively, which was not shifted in comparison to that
of corresponding cyclopalladated chloro dimmer.
Self-assembly of discrete pseudo-macrocycles with 1,10-
bicoordinated oxalato bridge
Based on the above results, we primarily attempted the re-
actions of
m-oxalato bridged Schiff-base palladacycles with rigid
bipyridyl ligands. Unexpectedly, when complex 1 and 2 was treated
by 4,40-bipyridyl (bpy) or 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt),
respectively, no any novel metallacycles were isolated. This result
reveals that the chelation of oxalato group with Pd is enough strong
not to be cleaved by bipyridyl ligand. Subsequently, we examined
the reactions of complexes 1 and 2 with flexible bis-monodentate
phosphines, such as 1,4-bis(diphenylphosphino)butane (dppb)
and 1,4-bis(diphenylphosphino)pentane (dppp) (Scheme 2),
expecting the formation of novel macrocycles based on cleavage of
Chart 1. Several possible coordination modes of oxalato group.
heterocycles or phosphines. A series of mono-, bi- and tri-nuclear
Schiff-base palladacycles were obtained [59,60]. On the basis of
these results, we considered to synthesize hemilabile chelate ligand
bridged Schiff-base palladacycles. We expected that the formation of
discrete macrocycles by selectively attacking the weaker metal-
ligand bonds of hemilabile chelate ligand bridged Schiff-base palla-
dacycles with molecules that have stronger affinity for metal center.
Since oxalato group with various coordination modesperhaps can act
PdeO in
m-oxalato bridged Schiff-base palladacycles. Recently, we
reported the cleavage reactions of
m
-azido and -thiocyanato
m
bridged Schiff-base palladacycles with tertiary and bis-
monodentate phosphines [60]. In contrast, the cleavage reactions
as hemilabile chelate ligand. We decided to synthesize
bridged Schiff-base palladacycles. Cyclopalladated chloro dimer [Pd
{C,N-
2-(4-R) C6H3CH]NeC6H3-2,6-i-Pr2}(
were treated by AgNO3 in CH3CN, subsequently reacted with an
aqueous solution of K2C2O4 in CH2Cl2 at room temperature to pro-
m-oxalato
of
m-oxalato bridged Schiff-base palladacycles are unknown.
Treatment of complex 1 and 2 with stoichiometric amount of dppb
or dppp in CH2Cl2 at room temperature, respectively, produced
binuclear Schiff-base palladacycles concomitant with bridging bis-
monodentate oxalato ligand and bridging bis-monodentate phos-
phine ligand [Pd{C,N-
C2O4)( -dppb) (R
C6H3CH]NC6H3-2,6-i-Pr2]2(
6). The results indicate that phosphines are a kind of better donors
for soft acceptors Pd(II) due to their softer base compared with
nitrogen and oxygen donors. And thus phosphine ligands have
enough strong affinity for palladium to cleave one of the PdeO
bonds in chelate oxalate group. Complexes 3e6 were characterized
k
m
-Cl)]2 (R ¼ H; OMe)
k
2-(4-R)C6H3CH]NC6H3-2,6-i-Pr2]2(
H, 3; OMe, 4) and [Pd{C,N-
2-(4-MeO)
h1 1-C2O4)(
-dppp) (R ¼ H, 5; OMe,
m- - -
h1 h1
duce pale yellow
m-oxalato bridged Schiff-base palladacycles [Pd
{C,N-
k
2-(4-R) C6H3CH]NeC6H3-2,6-i-Pr2}]2(
m-
h2
-h
2-C2O4) (R ¼ H,1;
m
¼
k
OMe, 2) (Scheme 1). The identities of 1 and 2 were determined by FT-
IR, 1H NMR spectroscopy, elemental analysis and single crystal X-ray
diffraction. The FT-IR spectra of 1 and 2 showed a strong absorption at
approximately 1622 cmꢀ1 and1623 cmꢀ1, respectively, due to the C]
O stretching of bis-bidentate oxalato bridge [56,57]. The 1H NMR
m
-
-
h
m
spectra of 1 and 2 displayed the resonance for CH]N protons at d 7.75
Scheme 1. Synthesis of m-oxalato bridged Schiff-base palladacycles 1 and 2.
Scheme 2. Synthesis of macrocycles 3e6.

Y. Jiang et al. / Journal of Organometallic Chemistry 759 (2014) 37e45
39
Scheme 3. Synthesis of bidentate/monodentate oxalato bridged binuclear cyclopalladated complex 7.
by spectroscopic and elemental analysis. Molecular structure of 3, 5
and 6 was determined by X-ray diffraction, respectively. The FT-IR
spectra of 3e6 showed characteristic strong bands of the oxalato
3, 5 and 6 unambiguously confirmed the formation of binuclear Pd
pseudo-macrocycles.
ligand at 1612 cmꢀ1
and 1269 cmꢀ1
nasCOO) and 1265 cmꢀ1
(
nasCOO) and 1263 cmꢀ1
(
nsCOO),1608 (nasCOO)
nsCOO), 1613 (nasCOO) and 1260 cmꢀ1
nsCOO),1607
nsCOO), respectively. The large difference
Synthesis of bidentate/monodentate tri-coordinated oxalato bridged
Schiff-base palladacycle
(
(
(
(
of 349 cmꢀ1, 339 cmꢀ1, 353 cmꢀ1 and 342 cmꢀ1 between the two
bands indicates that the carboxylate group of oxalato ligand is co-
ordinated to the metal in monodentate fashion [58,62,63]. The 1H
NMR spectra of 3e6 displayed the resonance for CH]N protons at
For the sake of further confirming the hemilability of bis-
bidentate bridging oxalate ligand, we examined the reaction of m-
oxalato bridged Schiff-base palladacycle 1 with PPh3, expecting the
formation of bis-monodentate oxalato bridged binuclear cyclo-
metallated Pd complex. Unexpectedly, one PdeO bond and one Pde
N bond was cleaved respectively to give unusual bidentate/mono-
dentate tri-coordinated oxalato bridged Schiff-base palladacycle
d
7.94,
d
7.80e7.86,
d
8.00 and
d
7.88, respectively, which was shifted
7.75 and 7.61) of corresponding
to downfield compared to that (
d
d
bis-bidentate oxalato-bridged cyclopalladated complexes 1 and 2.
Other protons of complexes 3e6 have been identified by the
chemical shift in the rest of their spectrum. Molecular structure of
[Pd(C,N-
k
k m- -h
2-C6H4CH]NC6H3-2,6-i-Pr2)(PPh3)]( h2 1-C2O4)[Pd(C-
1-C6H4CH]NC6H3-2,6-i-Pr2)(PPh3)] (7) (Scheme 3). Complex 7
Table 1
X-ray data collection and structure refinement for 1, 2, 3, 5, 6, 7.
1
2$0.5Et2O
3$CH2Cl2
5
6$CH2Cl2$H2O
7$2CH2Cl2$0.5H2O
Formula
C40H44N2O4Pd2
829.57
296(2)
0.30 ꢁ 0.27 ꢁ 0.22
Hexagonal
R-3
28.8606(14)
28.8606(14)
12.5204(12)
90.00
C44H53N2O6.50Pd2
926.68
296(2)
0.33 ꢁ 0.27 ꢁ 0.21
Monoclinic
P21/n
15.5551(18)
11.8754(14)
26.403(3)
90
101.860(2)
90
4773.2(10)
4
1.290
0.797
C69H74Cl2N2O4P2Pd2
1340.94
113(2)
0.24 ꢁ 0.18 ꢁ 0.10
Monoclinic
P21/c
14.380(2)
23.024(4)
20.817(3)
90
105.036(2)
90
C69H74N2O4P2Pd2
1270.04
296(2)
0.20 ꢁ 0.18 ꢁ 0.12
Triclinic
P1
14.2167(5)
22.9641(7)
21.6201(8)
90
103.391(2)
90
C72H80Cl2N2O7P2Pd2
1431.02
296(2)
0.20 ꢁ 0.20 ꢁ 0.20
Monoclinic
P21/n
13.7661(19)
13.1768(18)
42.330(6)
90
101.205(8)
90
C156H156Cl8N4O9P4 Pd4
3063.93
296(2)
0.20 ꢁ 0.20 ꢁ 0.16
Monoclinic
P21/n
14.704(4)
21.254(6)
25.118(8)
90
105.432(7)
90
Formula weight
Temperature (k)
Crystal size
Crystal system
Space group
ꢀ
a, A
ꢀ
b,A
ꢀ
c,A
a
, deg
, deg
b
90.00
g
, deg
120.00
9031.5(11)
9
1.373
0.934
3
ꢀ
V, A
6655.9(19)
4
1.338
6866.5(4)
4
1.229
7532.0(18)
4
1.262
7567(4)
2
1.345
Z
dcal, g cmꢀ3
m
, mmꢀ1
0.715
0.615
0.639
0.707
F(000)
3798
1900
2760
2624
2952
3144
Tmin
Tmax
0.775
0.827
10,708
3591
221
0.783
0.858
30,095
10,827
569
0.531
0.8470
0.9319
85,104
15,842
798
1.413
0.8870
0.9299
44,578
12,049
720
0.8828
0.8828
46,193
13,071
795
1.328
0.8714
0.8952
56,587
13,321
856
1.298
No. of reflns measured
No. of reflns unique
No. of params refined
ꢀꢀ3
Max., in Dr (e A
)
1.254
1.827
ꢀꢀ3
Min., in Dr (e A
)
ꢀ0.480
ꢀ0.344
ꢀ2.142
ꢀ2.017
ꢀ2.116
ꢀ1.009
GOF on F2
1.149
1.036
1.063
1.051
1.138
1.105
R (I > 2
wR2 (I > 2
s
(I))
s
0.0401
0.1344
0.0564
0.1664
0.0460
0.0951
0.0977
0.1132
0.0453
0.1212
0.0494
0.1243
0.1292
0.3097
0.1929
0.3430
0.1213
0.2850
0.1351
0.2915
0.0607
0.1389
0.0806
0.1534
a
(I))
R (all data)
a
wR2 (all data)
a
wR2 ¼ S[w(F2o ꢀ F2c)2]/S[w(F2o)2]1/2
.

40
Y. Jiang et al. / Journal of Organometallic Chemistry 759 (2014) 37e45
was characterized by FT-IR, 1H NMR spectroscopy, elemental anal-
ysis and single crystal X-ray diffraction. To our best knowledge,
complex 7 represents the first structurally characterized palladium
complex containing bidentate/monodentate tri-coordinated oxa-
lato bridge. The FT-IR spectra of 7 showed two strong absorptions at
approximately 1649 cmꢀ1 and 1612 cmꢀ1, respectively, due to the
C]O stretching of bidentate/monodentate oxalato bridge. The 1H
NMR spectra of 7 displayed the resonance for CH]N protons at
reveals that the molecular structure of 2 is similar to 1. Depend-
ing on the solvent, molecules of 2 adopt quite different stacking
mode, as represented in Fig. 3.
Complexes 3 (Fig. 4), 5 (Fig. 5) and 6 (Fig. 6) have similar binu-
clear structure. In complex 3, oxalato ligand in bis-monodentate
mode and dppb respectively link two Pd centers to form anoma-
lous 12-membered macrocycle. The distance of Pd1/Pd2
ꢀ
(6.8979(9) A) is longer than that of complex 1 due to the cleavage of
d
8.36, which was distinctly shifted to downfield compared to that (
d
two weaker PdeO bonds in 1. Two five-membered chelate rings
that contain the imine functionality are twisted with a dihedral
angle 84.8ꢂ due to the formation of macrocycle. Likewise, in com-
plexes 5 and 6, oxalato ligand in bis-monodentate mode and dppp
respectively link two Pd centers to form anomalous 13-membered
7.75) of corresponding cyclopalladated complex 1. Molecular
structure of 7 further confirmed the formation of unusual bidentate/
monodentate oxalato bridged binuclear cyclopalladated complex 7.
ꢀ
macrocycle, in which the distance of Pd1/Pd2 is 7.0292(13) A and
Structures of compounds
ꢀ
6.8826(15) A, respectively. Fig. 7 shows clearly the 13-membered
macrocycles of complexes 5 and 6.
The structures of 1e3 and 5e7 were unambiguously determined
by X-ray diffraction. Single crystals of 1e3 and 5e7 suitable for X-
ray diffraction analysis were obtained from a dichloromethane/
hexane solution while single crystals of 2 from a slowly evaporated
ether solution. Details on crystal data, intensity collection, and
refinement details are given in Table 1. In all structures, the coor-
dination of the Pd metal is essentially square-planar.
Fig. 8 reveals that one PPh3 cleaves one PdeO bond and another
PPh3 cleaves one PdeN bond to produce novel binuclear cyclo-
palladated complex 7. Oxalato ligand bridges two palladium metals
through bidentate/monodentate tri-coordinated mode. It indicates
that bis-bidentate bridging oxalato ligand possesses different
hemilability depending on attacking ligands. The distance of
ꢀ
Pd1/Pd2 is 5.826(1) A, which is slightly longer than that of com-
As shown in Fig. 1, the molecular of complex 1 has a dinuclear
structure bridged by oxalato group. Oxalato ligand links two [Pd
plex 1 due to the cleavage of one PdeO bond. The five-membered
chelate ring that contains the imine functionality is not coplanar
with oxalato chelate ring, being twisted to a dihedral angle of 61.2ꢂ
due to the intervention of PPh3.
{C,N-
k
2-(4-R)C6H3CH]NeC6H3-2,6-i-Pr2}]
moieties
in
bis-
bidentate mode to give a binuclear compound, and the distance
ꢀ
of Pd1/Pd1A is 5.4046(7) A. Two cyclometallated ligands are in a
In summary, bis-bidentate tetra-coordinated oxalato bridged
binuclear Schiff-base palladacycles were synthesized. Discrete
pseudo-macrocycles with 1,10-bicoordinated oxalato bridge were
obtained by self-assembly of tetra-coordinated oxalato bridged
binuclear Schiff-base palladacycles with bis-monodentate phos-
phines. When tetra-coordinated oxalato bridged binuclear Schiff-
base palladacycle reacted with triphenylphosphine, unusual
bidentate/monodentate tri-coordinated oxalato bridged Schiff-
base palladacycle was isolated. All these results offered the evi-
dence for hemilability of oxalato ligand.
trans arrangement with respect to the Pd/Pd axis. Two five-
membered chelate rings that contain the imine functionality are
nearly coplanar with oxalato chelate ring as shown by the
ꢀ
maximum deviation of 0.123 A, to which the diisopropylphenyl ring
is almost perpendicular with a dihedral angle 85.8(1)ꢂ. The Pd1e
ꢀ
ꢀ
C15 bond [1.947(5) A] and Pd1eN1 [2.015(4) A] are marginally
ꢀ
ꢀ
shorter than those ([1.971(4) A] and [2.036(3) A]) of corresponding
cyclopalladated chloro dimmer [57]. Two PdeO bonds are regarded
ꢀ
to be non-equivalent. Pd1eO2A [2.146(4) A] bond located on the
trans-position of Pd1eC15 bond is significantly longer than Pd1e
ꢀ
O1 bond [2.063(3) A] located on the trans-position of Pd1eN1
bond. It can be ascribed to different trans influence of carbon and
nitrogen. The data of these bond lengths indicate that oxalato group
can be used as hemilabile linkers. It is feasible for assembling of
metalla-macrocycles via cleavage of weaker PdeO bonds. Fig. 2
ꢂ
ꢂ
ꢀ
ꢀ
Fig. 1. Molecular structure of 1. Selected bond lengths (A) and angles ( ): Pd1eC15
1.947(5), Pd1eN1 2.015(4), Pd1eO1 2.063(3), Pd1eO2A 2.146(4); C20eO1ePd1
113.2(3) C15ePd1eN1 81.85(19), C15ePd1eO1 94.90(18), N1ePd1eO1176.61(15), N1e
Pd1eO2A 102.60(15).
Fig. 2. Molecular structure of 2. Selected bond lengths (A) and angles ( ): Pd1eC15
1.951(4), Pd1eN1 2.000(3), Pd1eO2 2.146(3), Pd1eO3A 2.049(3); C15ePd1eN1
80.93(15), C15ePd1eO3A 96.70(13), N1ePd1eO3A 176.93(12), N1ePd1eO2
101.74(12).

Y. Jiang et al. / Journal of Organometallic Chemistry 759 (2014) 37e45
41
Fig. 3. The stacking of the molecules in crystals 2 depending on different solvents. (a): CH3CH2OCH2CH3; (b): CH2Cl2.
Experimental
Niclolet AVATAR 330FT-IR spectrometer. Elemental analyses were
performed on a Thermo Flash EA1112 Analyzer.
General, materials and measurements
[Pd{C,N-
k
2-(4-R)C6H3CH]NeC6H3-2,6-i-Pr2}(
m-Cl)]2 (R
¼
H;
OMe) were prepared according literature methods [61].
All manipulations of air-sensitive compounds were performed
under nitrogen by standard Schlenk techniques. All solvents were
purified and degassed by standard procedures. Other regents were
used as supplied. 1H NMR spectra were obtained using a Mercury-
300 spectrophotometer in CDCl3, for all compounds using TMS as
an internal standard. 31P{1H} NMR spectra were obtained using a
Bruker-600 spectrophotometer in CDCl3, for all compounds using
85% H3PO4 as an external standard. IR spectra were recorded on a
Preparations
[Pd(C,N-
To a 20 mL CH3CN solution of complex [Pd(C,N-
NC6H3-2,6-i-Pr2)( -Cl)]2 (0.196 g, 0.241 mmol) was added AgNO3
k
2-C6H4CH]NC6H3-2,6-i-Pr2)]2(
m-
h2
-h
2-C2O4) (1)
2-C6H4CH]
k
m
(0.093 g, 0.548 mmol). After stirring for 15 h in dark at room tem-
perature, insoluble materials were filtered off. The solvent of the
ꢂ
ꢀ
Fig. 4. Molecular structure of 3. Selected bond lengths (A) and angles ( ): Pd1eC1 2.009(3), Pd2eC22 2.006(3), Pd1eN1 2.099(2), Pd2eN2 2.117(2), Pd1eO1 2.0974(19), Pd2eO4
2.108(2), Pd1eP1 2.2459(7), Pd2eP2 2.2618(8); C1ePd1eO1 171.92(9), C1ePd1eN1 81.45(10), O1ePd1eN1 90.58(9), C1ePd1eP1 95.39(8), O1ePd1eP1 92.62(6), N1ePd1eP1
176.28(7), C22ePd2eO4 172.13(10), C22ePd2eN2 81.26(11), O4ePd2eN2 92.08(9), C22ePd2eP2 94.61(9), O4ePd2eP2 92.38(6), N2ePd2eP2 173.63(8).

42
Y. Jiang et al. / Journal of Organometallic Chemistry 759 (2014) 37e45
ꢂ
ꢀ
Fig. 5. Molecular structure of 5. Selected bond lengths (A) and angles ( ): Pd1eC68 2.033(12), Pd2eC69 1.989(12), Pd1eN1 2.121(11), Pd2eN4 2.102(9), Pd1eO2 2.118(9), Pd2eO3
2.134(9), Pd1eP1 2.233(3), Pd2eP2 2.249(4); C68ePd1eO2 174.0(4), C68ePd1eN2 81.9(5), O2ePd1eN2 92.1(4), C68ePd1eP1 93.1(3), O2ePd1eP1 92.9(3), N2ePd1eP1 172.8(3),
C69ePd2eO3 171.4(5), C69ePd2eN1 80.3(5), O3ePd2eN1 92.9(4), C69ePd2eP2 95.3(4), O3ePd2eP2 92.1(3), N1ePd2eP2 171.7(3).
filtrate was fully removed by rotatory evaporator. The resulting pale
yellow oil was dissolved in 10 mL CH2Cl2 and filtered to a Schlenk
tube. Then K2C2O4$H2O solution (0.052 g, 0.282 mmol) dissolved in
4 mL H2O was added to the CH2Cl2 solution. After stirring for 16 h at
room temperature, the organic phase was separated and dried over
anhydrous MgSO4, and then the solvent was completely removed
under vacuum to give crude solid. Recrystallization from CH2Cl2/
CH(CH3)2); Anal. Calcd for C40H44N2O4Pd2: C, 57.91; H, 5.37; N, 3.38.
Found: C, 57.82; H, 5.37; N, 3.12.
[Pd{C,N-
84%)
k m- -h
2-(4-MeO)C6H3CH]NC6H3-2,6-i-Pr2}]2( h2 2-C2O4) (2,
Complex 2 was prepared in a similar manner as described for 1.
IR (KBr, cmꢀ1): 1596 (C]N), 1623 (C]O); m.p.: 287e289 ꢂC; dH
(300 MHz; CDCl3; Me4Si): 7.61 (2H, d, J ¼ 5.4 Hz, eCH]N), 7.24e
7.33 (4H, m, Ar), 7.13 (4H, dd, J ¼ 7.5 Hz, Ar), 6.87e6.96 (2H, m, Ar),
6.63e6.71 (2H, m, Ar), 3.90 (6H, d, J ¼ 16.5 Hz, eOCH3), 3.45 (4H,
hepta, eCH(CH3)2), 1.28 (12H, dd, J ¼ 6.6, 6.6 Hz, eCH(CH3)2), 1.15
hexane gave pale yellowcrystals of [Pd(C,N-
k
2-C6H4CH]NC6H3-2,6-
- -h
2-C2O4) (1, 0.160 g, 80%). IR (KBr, cmꢀ1): 1597 (C]N),
i-Pr2)]2(
m
h2
1622 (C]O); m.p.: 275e276 ꢂC; dH (300 MHz; CDCl3; Me4Si): 7.75
(2H, s, eCH]N), 7.27e7.51 (6H, m, Ar), 7.02e7.19 (8H, m, Ar), 3.45
(hepta, 2H, eCH(CH3)2), 1.24 (24H, ddd, J ¼ 6.6, 6.3, 6.3 Hz, e
(12H, d,
J
¼
6.9, 7.2 Hz, eCH(CH3)2); Anal. Calcd for
ꢂ
ꢀ
Fig. 6. Molecular structure of 6. Selected bond lengths (A) and angles ( ): Pd1eC72 1.988(12), Pd2eC73 1.973(11), Pd1eN1 2.114(9), Pd2eN4 2.102(9), Pd1eO1 2.102(7), Pd2eO3
2.083(8), Pd1eP1 2.253(3), Pd2eP2 2.265(3); C72ePd1eO1 171.3(4), C72ePd1eN1 81.2(5), O1ePd1eN1 91.9(4), C72ePd1eP1 97.2(4), O1ePd1eP1 90.3(2), N1ePd1eP1 173.3(3),
C73ePd2eO3 170.2(4), C73ePd2eN4 80.4(5), O3ePd2eN4 89.8(3), C73ePd2eP2 100.2(4), O3ePd2eP2 89.6(2), N4ePd2eP2 176.3(3).

Y. Jiang et al. / Journal of Organometallic Chemistry 759 (2014) 37e45
43
ether to give pale yellow solids. Recrystallization from CH2Cl2/
hexane generated pale yellow crystals of [Pd(C,N-
2-C6H4CH]
NC6H3-2,6-i-Pr2)]2( -dppb) (3, 0.106 g, 75%). IR (KBr,
h1 1-C2O4)(
k
m-
-h
m
cmꢀ1): 1612 (C]N; C]O); m.p.: 228e230 ꢂC; dH (300 MHz; CDCl3;
Me4Si): 7.94 (2H,d, J ¼ 7.2 Hz, eCH]N), 7.78e7.84 (8H, m, ePPh2e),
7.27e7.43 (16H, m, ePPh2e, Ar), 7.15 (4H, d, J ¼ 7.5 Hz, Ar), 6.88e
6.93 (2H, m, Ar), 6.61e6.68 (4H, m, Ar), 3.55 (4H, hepta, e
CH(CH3)2), 2.14 (4H, br, PeCH2eCH2eCH2eCH2eP), 1.31 (12H, d,
J ¼ 6.3 Hz, eCH(CH3)2), 1.12 (12H, d, J ¼ 6.6 Hz, eCH(CH3)2), 1.00
(4H, br, PeCH2eCH2eCH2eCH2eP); dP (CDCl3): 33.4 (s); Anal. Calcd
for C68H72N2O4P2Pd2$0.25CH2Cl2: C, 64.18; H, 5.72; N, 2.19. Found:
C, 64.29; H, 5.82; N, 1.88.
Complexes 4e7 were prepared in a similar manner as complex 3.
[Pd{C,N-
dppb) (4, 43%)
k m- -h m-
2-(4-MeO)C6H3CH]NC6H3-2,6-i-Pr2]2( h1 1-C2O4)(
IR (KBr, cmꢀ1): 1608 (C]N; C]O); m.p.: 203e205 ꢂC; dH
(300 MHz; CDCl3; Me4Si): 7.80e7.86 (10H, m, eCH]N, ePPh2e),
7.27e7.44 (14H, m, ePPh2e, Ar), 7.18 (2H, d, J ¼ 8.4 Hz, Ar), 7.13 (4H, d,
J ¼ 7.5 Hz, Ar), 6.40 (2H, dd, J ¼ 2.4, 2.4 Hz, Ar), 6.13 (2H, dd, J ¼ 2.1,
2.1 Hz, Ar), 3.54 (4H, hepta, eCH(CH3)2), 3.14 (6H, s, eOCH3), 2.14 (4H,
br, PeCH2eCH2eCH2eCH2eP), 1.27 (12H, d, J ¼ 6.9 Hz, eCH(CH3)2),
1.09 (16H, d, J ¼ 6.9 Hz, eCH(CH3)2, PeCH2eCH2eCH2eCH2eP); dP
(CDCl3): 33.3 (s); Anal. Calcd for C70H76N2O6P2Pd2$0.25CH2Cl2: C,
63.09; H, 5.77; N, 2.09. Found: C, 62.89; H, 6.00; N, 2.46.
Fig. 7. Macrocycle views of 5 (a) and 6 (b). 2,6-Diisopropyl phenyl, phenyl of dppb and
dppp, and hydrogen atoms were omitted for clarity. Palladium, nitrogen, oxygen,
phosphorus and carbon are represented by purple, blue, red, orange and black spheres,
respectively. (For interpretation of the references to color in this figure legend, the
reader is referred to the web version of this article.)
[Pd(C,N-
76%)
k m- -h m-dppp) (5,
2-C6H4CH]NC6H3-2,6-i-Pr2)]2( h1 1-C2O4)(
IR (KBr, cmꢀ1): 1613 (C]N; C]O); m.p.: 206e208 ꢂC; dH
(300 MHz; CDCl3; Me4Si): 8.00 (2H, d, J ¼ 7.2 Hz, eCH]N), 7.69e
7.75 (8H, m, ePPh2e), 7.35e7.47 (12H, m, ePPh2e), 7.27e7.32 (4H,
m, Ar), 7.21 (4H, d, J ¼ 7.5 Hz, Ar), 6.91e6.96 (2H, m, Ar), 6.70e6.78
(4H, m, Ar), 3.65 (4H, hepta, eCH(CH3)2), 2.02 (4H, br, PeCH2eCH2e
CH2eCH2eCH2eP), 1.60 (4H, br, PeCH2eCH2eCH2eCH2eCH2eP),
1.32 (12H, d, J ¼ 6.9 Hz, eCH(CH3)2), 1.26 (4H, br, PeCH2eCH2e
CH2eCH2eCH2eP),1.13 (12H, d, J ¼ 6.9 Hz, eCH(CH3)2), 0.98 (4H, br,
C42H48N2O6Pd2$0.25CH2Cl2: C, 55.71; H, 5.37; N, 3.08. Found: C,
55.40; H, 5.35; N, 2.72.
[Pd(C,N-k m- -h m-dppb) (3)
2-C6H4CH]NC6H3-2,6-i-Pr2)]2( h1 1-C2O4)(
To a 6 mL CH2Cl2 solution of complex 1 (0.094 g, 0.113 mmol)
was added 1,4-(diphenylphosphino)butane (0.049 g, 0.115 mmol).
After stirring for 14 h at room temperature, the solvent was
completely evaporated and the resulting residue was isolated by
ꢂ
ꢀ
Fig. 8. . Molecular structure of 7. Selected bond lengths (A) and angles ( ): Pd1eC8 1.995(6), Pd1eN2, 2.098(4), Pd1eO4, 2.135(4), Pd1eP1 2.2569(15), Pd2eC3 1.986(5), Pd2eO1
2.128(4), Pd2eO2 2.075(4), Pd2eP2 2.2244(17), C8ePd1eN2 81.4(2), C8ePd1eO4 168.73(19), C8ePd1eP1 95.18(16), N2ePd1eO4 87.63(16), C4eO4ePd1 127.3(4), C3ePd2eO2
91.15(19), C3ePd2eO1 169.32(19), O1ePd2eO2 79.49(15), O1ePd2eP2 99.38(11), C4eO1ePd2 111.9(3).

44
Y. Jiang et al. / Journal of Organometallic Chemistry 759 (2014) 37e45
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PeCH2eCH2eCH2eCH2eCH2eP); dP (CDCl3): 33.0 (s); Anal. Calcd
for C69H74N2O4P2Pd2$0.25CH2Cl2: C, 64.41; H, 5.81; N, 2.17. Found:
C, 64.61; H, 6.18; N, 2.47.
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378.
[Pd{C,N-
dppp) (6, 45%)
k m- -h m-
2-(4-MeO)C6H3CH]NC6H3-2,6-i-Pr2}]2( h1 1-C2O4)(
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379.
IR (KBr, cmꢀ1): 1607 (C]N; C]O); m.p.: 229e230 ꢂC; dH
(300 MHz; CDCl3; Me4Si): 7.88 (2H, d, J ¼ 7.2 Hz, eCH]N), 7.69-7.75
(8H, m, ePPh2e), 7.37e7.48 (12H, m, ePPh2e), 7.29 (2H, d,
J ¼ 8.1 Hz, Ar), 7.21 (2H, d, J ¼ 8.4 Hz, Ar), 7.18 (4H, d, J ¼ 7.2 Hz,
Ar),6.43 (2H, dd, J ¼ 2.4, 2.4 Hz, Ar), 6.26 (2H, dd, J ¼ 2.4, 2.4 Hz, Ar),
3.64 (4H, hepta, eCH(CH3)2), 3.27 (6H, s, eOCH3), 2.03 (4H, br, Pe
CH2eCH2eCH2eCH2eCH2eP), 1.31 (12H, d, J ¼ 6.6 Hz, eCH(CH3)2),
1.27 (4H, br, PeCH2eCH2eCH2eCH2eCH2eP), 1.13 (12H, d,
J ¼ 6.9 Hz, eCH(CH3)2), 1.02 (2H, br, PeCH2eCH2eCH2eCH2eCH2e
P); dP (CDCl3): 32.9 (s); Anal. Calcd for C71H78N2O6P2Pd2$2CH2Cl2: C,
58.45; H, 5.51; N, 1.87. Found: C, 58.63; H, 5.64; N, 2.20.
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13950e13951.
[Pd(C,N-
1-C6H4CH]NeC6H3-2,6-i-Pr2)(PPh3)] (7, 78%)
k m- -h
2-C6H4CH]NC6H3-2,6-i-Pr2)(PPh3)]( h2 1-C2O4)[Pd(C-
k
IR (KBr, cmꢀ1): 1591 (C]N), 1612 (C]N; C]O), 1649 (C]O);
m.p.: 157e159 ꢂC; dH (300 MHz; CDCl3; Me4Si): 8.36 (2H, br, eCH]
N), 7.26e7.72 (32H, m, PPh3, Ar), 6.91e7.03 (8H, m, Ar), 6.61e6.69
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(CDCl3):
76H74N2O4P2Pd2$2CH2Cl2: C, 61.47; H, 5.16; N, 1.84. Found: C,
61.35; H, 5.18; N, 2.28.
39.8
(s),
40.3
(s);
Anal.
Calcd
for
C
X-ray structure determination
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Suitable crystals for X-ray analysis of 1e3 and 5e7 were ob-
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slowly evaporating ether solution of 2. X-ray data of complexes 1e3
and 5e7 were collected on Bruker APEX-II area-detector diffrac-
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cell and intensity data were performed with graphite-
ꢀ
monochromated Mo K
collected at room temperature using the
a
radiation (
l
¼ 0.71073 A). All data were
u
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at ꢀ160 ꢂC. Details of the data collection and refinement are
summarized in Table 1. All calculations were carried out with the
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Acknowledgment
This work was supported by the Project Sponsored by the Sci-
entific Research Foundation for the Returned Overseas Chinese
Scholars of State Education Ministry (2008), the Scientific Research
Foundation funded by Liaoning Provincial Education Department of
China [No. LT2011001], the Natural Science Foundation of Liaoning
Province [No. 201102085] and Foundation of 211 Project for Inno-
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Appendix A. Supplementary material
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CCDC 957807e957812 contain the supplementary crystallo-
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