Complexes of palladium(II) chloride with 3-(pyrazol-1-yl)propanamide (PPA) and related ligands

Article abstract of DOI:10.1016/j.poly.2019.07.043

Four new derivatives of the versatile polyfunctional ligands 3-(pyrazol-1-yl)propanamide (1, = PPA) and 3-(3,5-dimethylpyrazol-1-yl)-propanamide (2, = Me₂PPA) have been prepared, in which one of the amide hydrogens on 1 and 2 is formally replaced by alkyl residues. X-Ray diffraction studies revealed that, in contrast to 1 and 2, the N-isopropyl substituted derivatives 3 and 4 form supramolecular hydrogen-bonded chains rather than two-dimensional arrays, and the N-(2-methyl-4-oxypentan-2-yl) (=MOP) substituted compounds 5 and 6 exist as cyclic dimers in the solid state. Reactions of PdCl₂(COD) (COD = 1,5-cyclooctadiene) with 2 equiv. of the corresponding ligands 1–6 in all cases afforded trans-PdCl₂(L)₂ complexes (7–12). X-ray crystal structure determinations of 8, and 10–12 revealed κN-monodentate coordination of the PPA-type ligands.

Full text of DOI:10.1016/j.poly.2019.07.043

Polyhedron 171 (2019) 493–501
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Complexes of palladium(II) chloride with 3-(pyrazol-1-yl)propanamide
(
PPA) and related ligands
a
b
a
a
a
Tyler M. Palombo , Phil Liebing , Sara J. Hildebrand , Quentin R. Patrikus , Anders P. Assarsson ,
b
a,
⇑
b
b,
⇑
a,
⇑
Ling Wang , Donna S. Amenta , Felix Engelhardt , Frank T. Edelmann , John W. Gilje
a
Department of Chemistry and Biochemistry, James Madison University, MSC 4501, Harrisonburg, VA 22807, United States
Chemisches Institut der Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Four new derivatives of the versatile polyfunctional ligands 3-(pyrazol-1-yl)propanamide (1, = PPA) and
-(3,5-dimethylpyrazol-1-yl)-propanamide (2, = Me PPA) have been prepared, in which one of the amide
hydrogens on 1 and 2 is formally replaced by alkyl residues. X-Ray diffraction studies revealed that, in
contrast to 1 and 2, the N-isopropyl substituted derivatives 3 and 4 form supramolecular hydrogen-
bonded chains rather than two-dimensional arrays, and the N-(2-methyl-4-oxypentan-2-yl) (=MOP)
Received 26 June 2019
Accepted 30 July 2019
Available online 8 August 2019
3
2
Keywords:
Pyrazolylpropanamide
Palladium
Crystal structure
Hydrogen bonding
Coordination Modes
substituted compounds 5 and 6 exist as cyclic dimers in the solid state. Reactions of PdCl
COD = 1,5-cyclooctadiene) with 2 equiv. of the corresponding ligands 1–6 in all cases afforded
trans-PdCl (L) complexes (7–12). X-ray crystal structure determinations of 8, and 10–12 revealed
N-monodentate coordination of the PPA-type ligands.
2
(COD)
(
2
2
j
Ó 2019 Elsevier Ltd. All rights reserved.
1
. Introduction
There is a considerable interest in the use of multifunctional
of PPA-type ligands to display different coordination modes [15].
The most characteristic ligand coordination is seven membered
ring chelation involving the pyrazolyl nitrogen and the amide oxy-
ligands containing substituted pyrazole groups because of their
potential applications in catalysis [1–7] and their ability to form
complexes that mimic structural and catalytic functions in metal-
loproteins [8–10]. For several years, we have been interested in
gen donors (
j
N,
j
O-chelating, Scheme 1, a) [11–15]. However,
jN:
jO-bridging and
jN-monodentate modes (Scheme 1, b and c) [15],
as well as more complex coordination patterns [11,14] have been
observed in a number of compounds. Due to the presence of amide
NAH as a potent hydrogen-donating group, the free ligands and
complexes participate in highly diverse hydrogen-bonded
supramolecular structures in the solid state [11–18]. The chemistry
with second and third transition series metals is much less widely
3
-(pyrazol-1-yl)propanamide (1, = PPA), and related ligands (cf.
Scheme 1, [11–13]). The coordination chemistry of 1 with first
transition series metals is diverse. The complexes CuCl (PPA)
and Co Cl (PPA) form in reactions with copper(II) and cobalt(II)
chloride, respectively [11]. The reaction of CuBr with 1 produced
CuBr(PPA) ]Br [12], and the perchlorates of iron(II) and cobalt(II)
afforded the complexes [M(PPA) (EtOH) ](ClO (M = Fe, Co),
whereas with nickel(II) chloride, light green NiCl (PPA) and the
dark green cationic nickel(II) complex [Ni(PPA) (H O) ]Cl were
2
2
3
6
4
2
investigated. The reaction of RuCl (PPh
2
3 3 2
) with 1 forms RuCl (PPA)
[
2
(PPh , which also contains a jN,jO-chelating ligand. The crystal
3
)
2
2
2
4
)
2
structure shows the existence of supramolecular dimers formed
by NAHꢀ ꢀ ꢀCl bonds, but not an extensive hydrogen-bonded
network [19]. In contrast, silver(I) forms the dicoordinate complex
2
2
2
2
4
2
2 3 2
[Ag(PPA) H O, in which the PPA ligand is jN-monodentate,
]NO.
isolated [13]. While complexes of manganese(II) salts with 1 have
not been reported, derivatives of 1, 2-methyl-3-(pyrazol-1-yl)-
propanamide and 3-(3,5-dimethylpyrazol-1-yl)-propanamide (2,
and participates in a complex hydrogen-bonded framework [13].
The present study concentrates on the synthesis and structural
=
Me
study, we reported a series of crystalline MnCl
ZnCl complexes with ligand 2, which demonstrated the ability
2
PPA), form complexes with this metal ion [14,15]. In a recent
2
characterization of PdCl complexes with PPA-derived ligands. In
this contribution, we focused on ligands with substituents at dif-
fering positions of the molecule. In addition to the frequently used
2
, CoCl , CuCl , and
2
2
2
2
unsubstituted PPA (1) and Me PPA (2), we decided to investigate a
series of N-substituted derivatives in order to study the influence
of the number of hydrogen-bond donors on the resulting molecular
and supramolecular structures (Scheme 2). Therefore, we have
⇑
Corresponding authors.
E-mail addresses: amentads@jmu.edu (D.S. Amenta), frank.edelmann@ovgu.de
F.T. Edelmann), giljejw@jmu.edu (J.W. Gilje).
(
https://doi.org/10.1016/j.poly.2019.07.043
277-5387/Ó 2019 Elsevier Ltd. All rights reserved.
0

4
94
T.M. Palombo et al. / Polyhedron 171 (2019) 493–501
a)
b)
2
c)
[
M ]
O
O
[M]
N
N
O
N
NH2
N
NH2
N
NH2
N
1
[M]
[
M ]
Scheme 1. Schematic representation of different coordination modes observed for
-(pyrazol-1-yl)propanamide-derived ligands: a) N, O-chelating, b) N: O-bridg-
ing, and c) N-monodentate.
3
j
j
j j
j
chosen to use the N-isopropyl derivatives of PPA and Me
2
PPA (3,
PPA deriva-
tives having an N-(2-methyl-4-oxypentan-2-yl) residue (5,
iPr
iPr
Scheme 3. Preparation of the ligands 1–6.
=
2 2
PPA , and 4, = ‘‘Me PPA ”), as well as PPA and Me
MOP
=
2
‘‘PPAMOP”, and 6, = ‘‘Me
2
PPA
”, MOP = 2-methyl-4-oxypentan-
PPAiPr
2
) (10),
crystals have not. PdCl
2
(Me
(11), and PdCl
several organic solvents and allowed for obtaining NMR spectra
2
PPA)
2
(8), PdCl
2
(Me
2
-yl). We were interested in determining if the ligands would
MOP
MOP
PdCl
2
(PPA
)
2
2
(Me
2
PPA
2
) (12) are soluble in
chelate as observed with e.g. ruthenium(II) [19] or whether a mon-
odentate mode as seen with silver(I) [13] would occur. In addition,
1
13
and X-ray quality crystals. The H and C NMR spectra resemble
those of the uncoordinated ligands. The most notable differences
involve the chemical shifts of the triplets in the H NMR spectra.
1
and 2 contain two amide hydrogens and are able to form
extended supramolecular structures, which is also to be expected
for their PdCl -complex forms [11–15]. With 3 and 4 there is only
1
2
These can be assigned to the –CH
pyrazolyl ring to the amide functionality. The most downfield tri-
plet, which we assign to the CH group attached to the pyrazolyl
nitrogen, shifts downfield by nearly 0.7 ppm, while the upfield tri-
plet, which we assign to the CH group attached to the amide car-
2 2
CH – groups that connect the
a single NAH hydrogen-bond donor, thus, the ability of these
ligands to form extensive hydrogen bonding networks should be
limited both in their free and complexed states. Finally, 5 and 6
also contain a single amide hydrogen, but have a second carbonyl
functional group that provides an additional potential coordination
site and hydrogen-bond acceptor moiety.
2
2
bon, exhibits a downfield shift of nearly 1 ppm. While the spectra
are consistent with complex formation, they do not provide sub-
stantive information on structural details of the molecules. The
IR spectra of the free ligands and the palladium complexes show
typical bands for the amide functionality. Comparison of the free
ligand 3 and complex 9 revealed a significant increase to higher
2
. Results and discussion
2.1. Preparation and properties
ꢁ1
wavenumbers in the NAH stretching vibrations (3321 cm and
375 cm , respectively). A similar behavior was observed for the
ꢁ
1
3
2
Ligands. Previously, PPA (1) [11–13] and Me PPA (2) [15] have
complexes 10–12. This NAH absorption shift is consistent with
the formation of the NAH hydrogen bridge to the central metal
been reported to form in a straightforward manner by a base-cat-
alyzed Michael addition of acrylamide with pyrazole or 3,5-
dimethylpyrazole, respectively (Scheme 3). Similar reactions using
ꢁ1
ꢁ1
Pd. The IR spectra also show bands at 1638 cm and 1543 cm
ꢁ1
-1
iPr
in 3 and 1635 cm and 1564 cm in 9, which could be assigned
to the C@O stretching vibration (amide I) and the interaction
N-isopropylacrylamide as starting material yielded PPA (3) and
iPr
2
Me PPA
(4), while the diacetone-derived acrylamide
MOP
between mC-N and dCNH (amide II), respectively [20].
H
2
C = CONH-CMe
2
-CH
(6). Compounds 1–6 have been characterized
spectroscopically, by elemental analysis, and X-ray crystallogra-
2
-COMe led to the formation of PPA
(5)
MOP
2
and Me PPA
2.2. Crystal structures
1
13
phy. The H and C NMR and the IR spectra are consistent with
the proposed structures.
2
The crystal structures of PPA (1) [13] and Me PPA (2) [21] have
Complexes of ligands 1–6 with palladium(II) chloride. Reactions of
been published previously, and those of the N-substituted deriva-
tives 3–6 are reported here (Figs. 1–4, see Table 1 for experimental
details). Regarding the orientation of the N-alkyl substituent rela-
tive to the amide oxygen, all four compounds exist as the s-cis rota-
mer in the crystal. While the bond distances and angles are
unremarkable and very similar between the molecules, the hydro-
gen bonding patterns in the crystal structures differ between the
various derivatives. In compounds 1 and 2, the molecules are
linked into two-dimensional supramolecular arrays by NAHꢀ ꢀ ꢀO
PdCl
sponding ligands 1–6 under inert conditions produced yellow
products that analyzed for PdCl (L) (7–12; Scheme 4). In the case
of PdCl (PPA) (7), the complex is insoluble in common solvents,
2
(COD) (COD = 1,5-cyclooctadiene) with 2 equiv. of the corre-
2
2
2
2
except for DMSO which appears to displace the ligand. Conse-
quently, this complex has only been characterized by elemental
iPr
2 2
analysis and IR spectroscopy. PdCl (PPA ) (9) is soluble in several
solvents, so NMR spectra have been obtained, but X-Ray quality
O
O
O
O
N
N
N
iPr
N
NH2
N
N
H
N
N
H
PPAiPr
PPAMOP
PPA 1
3
( )
5
(
)
( )
O
O
O
O
N
N
N
iPr
N
NH2
N
N
N
N
H
H
Me PPA 2
( )
Me PPAiPr
4
Me PPAMOP
6
2
( )
2
2
( )
Scheme 2. Schematic representation of the ligands 1–6 used in this study.

T.M. Palombo et al. / Polyhedron 171 (2019) 493–501
495
Scheme 4. Preparation of the palladium(II) complexes 7–12.
Fig. 1. Molecular structure of PPAiPr (3) in the crystal, showing the atom-numbering
scheme. Displacement ellipsoids with 50% probability. Selected interatomic
distances (pm): C1–O1 123.6(1), C1–N1 133.8(2), N2–N3 135.3(2), N3–C4 133.2(2).
Fig. 4. Molecular structure of Me
2
PPAMOP (5) in the crystal, showing disorder of the
keto group over two orientations together with the atom-numbering scheme.
Displacement ellipsoids with 50% probability. Selected interatomic distances (pm):
0
O1–C8 122.7(2), O2–C13 124.2(5), O2 –C13 121.3(5), N1–N2 136.1(2), N2–C4 135.4
(
2), N3–C8134.2(2).
and NAHꢀ ꢀ ꢀN bonds [13,21]. As anticipated, this is not the case for
–6, since one of the two hydrogen bond donors is formally
3
iPr
replaced by an alkyl group. Therefore, in PPA (3), the molecules
are stacked together to a linear chain by NAHꢀ ꢀ ꢀO bonds between
iPr
2
the amide groups, while the crystal structure of Me PPA (4) dis-
Fig. 2. Molecular structure of Me
numbering scheme. Displacement ellipsoids with 50% probability. Selected inter-
atomic distances (pm): C1–O 122.7(2), C1–N1 132.9(2), N2–N3 136.0(2), N3–C4
2
PPAiPr (4) in the crystal, showing the atom-
plays helical chains formed by NAHꢀ ꢀ ꢀN bonds between amide car-
MOP
bonyl and pyrazolyl moieties (Fig. 5). In contrast, PPA
Me PPA
2
(5) and
MOP
(6) both exist as cyclic supramolecular dimers in the
1
33.4(2).
crystal. These are formed by NAHꢀ ꢀ ꢀN bonds, while the amide
and keto oxygens do not contribute to hydrogen bonding (Fig. 6).
The hydrogen-bonded Nꢀ ꢀ ꢀO distance in 3 is 296.0(1) pm and
therefore comparable with the values observed in 1 (293.4(1)
pm) [13] and 2 (293.6(3) pm) [21]. The Nꢀ ꢀ ꢀN separations in 4–6
are in a narrow range of 297.7(2)–300.3(2) pm and resemble that
observed in 1 (299.3(1) pm) [13], while the value observed in 2
(
308.4(3) pm) is significantly larger [21].
Crystal structure determinations of the palladium(II) complexes
8
and 10–12 revealed that all these compounds exist as
well-defined mononuclear, centrosymmetric complexes of the
composition PdCl (L) (Figs. 7–9, for experimental details see
Table 1). While the crystal quality of PdCl
was not adequate for full structure refinement, the data obtained
2
2
MOP
2
2
(Me PPA
2
) (12)
iPr
MOP
for PdCl
11) allowed for a detailed analysis of the bonding parameters and
hydrogen-bond geometries. In all four complexes, the two PPA-
derived ligands are attached to the palladium center in a N-mon-
odentate mode, which has been previously observed for the copper
II) complex CuCl (Me PPA) O [15]. Just like in the reference
2 2
(Me PPA)
2
(8), PdCl
2
(Me
2
PPA
)
2
2
(10), and PdCl (PPA
)
2
(
j
(
2
2
2
ꢀ2H
2
Fig. 3. Molecular structure of PPAMOP (5) in the crystal, showing two molecules in
compound, a square-planar coordination of the metal center is
completed by two chloro ligands, whereas the two coordinated
pyrazolyl groups are in a trans arrangement (configuration index
SP-4–12). The Pd-N bond lengths in 8, 10, and 11 are virtually
equal at 200.2(2)–200.9(1) pm, thus being not significantly
the asymmetric unit together with the atom-numbering scheme. Displacement
ellipsoids with 50% probability. Selected interatomic distances (pm): Molecule 1:
O1–C2 121.5(2), O2–C7 122.1(2), N1–C7 134.8(2), N2–N3 135.1(2), N3–133.2(2);
Molecule 2: O3–C14 121.5(2), O4–C19 122.0(2), N4–C19 134.6(2), N5–N6 134.7(2),
N5–C24 133.8(2).

4
96
T.M. Palombo et al. / Polyhedron 171 (2019) 493–501
Table 1
Crystallographic details for the compounds reported in this work.
Compound
3
4
5
6
8
10
11
CCDC deposition number 1,912,534
1,912,535
1,912,536
1,912,537
1,912,538
1,912,539
1,912,540
Molecular formula sum
Formula weight/g mol
Crystal system
Space group
C
9
H
15
N
3
O
C
11
H
19
N
3
O
C
12
H
19
N
3
O
2
C
14
H
23
N
3
O
2
C
16
H
26Cl
511.73
monoclinic
P2 /c
2
6
N O
2
Pd
C
22
H
38Cl
2
6
N O
2
Pd
24 2 6 4
C H38Cl N O Pd
651.90
triclinic
ꢁ
1
181.24
monoclinic
P2 /c
209.29
monoclinic
P2 /n
237.30
triclinic
265.35
monoclinic
P2 /n
595.88
triclinic
1
1
P1
1
1
P1
P1
Cell parameters a/Å
b/Å
c/Å
4.9352(2)
17.338(1)
11.4111(5)
90
99.505(3)
90
963.02(8)
4
392
10.062(2)
11.339(2)
11.308(2)
90
113.00(3)
90
1187.6(5)
4
456
8.718(4)
8.230(3)
17.882(4)
10.503(3)
90
109.29(3)
90
1459.0(8)
4
576
11.2723(5)
6.5591(2)
14.5479(7)
90
100.723(4)
90
1056.83(8)
2
520
7.2409(4)
8.4791(4)
11.5221(6)
93.677(4)
94.373(4)
107.371(4)
670.37(6)
1
8.168(4)
8.969(4)
10.409(6)
14.203(7)
83.79(5)
84.29(4)
77.21(4)
1246(1)
4
512
1.265
0.088
10.382(5)
76.22(4)
83.26(4)
81.16(3)
727.3(6)
1
336
1.488
0.861
a
/deg.
b/deg.
/deg.
Cell volume/Å
c
3
Molecules per cell z
Electrons per cell F000
308
1.476
0.921
/g cm 3 1.250
)
ꢁ
1.171
0.077
1.208
0.082
1.608
1.154
Calcd. density
m/mm (Mo-K
q
a
ꢁ
1
0.085
Crystal color and shape
Crystal size/mm
Temperature/K
colorless rod
colorless prism
colorless block
colorless block
yellow plate
yellow rod
yellow block
0.37 ꢂ 0.26 ꢂ 0.16 0.54 ꢂ 0.48 ꢂ 0.33 0.19 ꢂ 0.17 ꢂ 0.13 0.20 ꢂ 0.16 ꢂ 0.15 0.39 ꢂ 0.24 ꢂ 0.06 0.20 ꢂ 0.11 ꢂ 0.11 0.21 ꢂ 0.18 ꢂ 0.17
133(2)
173(2)
100(2)
100(2)
133(2)
153(2)
100(2)
h range/deg.
Reflections collected
Reflections unique
3.621 . . . 29.230
6977
2575
2.302 . . . 25.997
5884
2295
2.014 . . . 29.285
10,941
6574
2.278 . . . 29.233
15,321
3916
3.610 . . . 26.998
7870
2297
2.956 . . . 27.999
8066
3244
2.358 . . . 29.148
7565
3790
Reflections with I > 2
r
(I) 2031
1791
5875
3665
2124
3081
3749
Completeness of dataset 99.2%
98.4%
96.6%
98.7%
99.5%
99.8%
96.8%
R
int
0.0364
0.0343
0.0290
0.0471
0.0439
0.0383
0.0337
Parameters; Restraints
(all data, I > 2 (I))
wR (all data, I > 2 (I))
GooF (F )
121; 0
141; 0
314; 444
0.0627; 0.0549
0.1280; 0.1240
1.156
187; 274
0.0669; 0.0621
0.1311; 0.1291
1.258
126; 0
155; 0
172; 232
0.0270; 0.0266
0.0687; 0.0685
1.072
R
1
r
0.0641; 0.0440
0.1030; 0.0932
1.053
0.0597; 0.0426
0.1087; 0.1017
1.039
0.0275; 0.0251
0.0677; 0.0664
1.065
0.0240; 0.0220
0.0581; 0.0575
1.047
2
r
2
Max. residual peaks
Extinction coefficient
–0.195; 0.225
0.023(4)
–0.203; 0.203
0.026(6)
–0.229; 0.323
–
–0.226; 0.293
–
–0.929; 0.610
–
–0.949; 0.546
–
–1.161; 0.494
–
dependent on the substituent pattern of the PPA ligand. The same
is true for the Pd-Cl bonds, which were observed at 229.6(1)–230.1
3. Conclusions
(
1) pm. Consequently, the coordination environment around the Pd
center is similar to that in the related complex trans-PdCl (pyra-
zole) (Pd-Cl 230.79(6) pm, Pd-N 202.8(2) pm) [22]. However,
As a continuation of our studies of the coordination chemistry
of 3-(pyrazol-1-yl)propanamide (PPA) and related compounds,
we have prepared ligands in which one of the amide hydrogens
2
2
the molecular structures of 8, 10, and 11 are supported by
intramolecular NAHꢀ ꢀ ꢀCl bonding. The significance of this sec-
ondary bonding interaction is corroborated by the pyrazole ring
being rotated out of the palladium’s coordination plane by about
on PPA (1) and Me PPA (2) is formally replaced by alkyl residues.
These substitutions drastically reduce the ability of the compounds
2
to form complex extended H-bond networks. Thus, in contrast to 1
and 2, the N-isopropyl substituted derivatives 3 and 4 form
supramolecular hydrogen-bonded chains rather than two-dimen-
sional arrays, and the N-(2-methyl-4-oxypentan-2-yl) (=MOP) sub-
stituted compounds 5 and 6 exist as cyclic dimers in the solid state.
All of the ligands 1–6 form trans-PdCl (L) complexes (7–12). X-ray
7
0°, while the PdCl
trans-PdCl (pyrazole)
intramolecular Nꢀ ꢀ ꢀCl distances are 347.6(2) pm (8), 335.9(2) pm
10), and 339.7(2) pm (11), respectively, and therefore larger than
2
N
2
and C
3 2
N planes are almost coplanar in
2
2
(angle between planes 9.1(1)°) [22]. The
(
2
2
in the related copper(II) complex (Nꢀ ꢀ ꢀCl 331.8(2) pm) [15]. As a
consequence of the ‘‘twisted” arrangement of the pyrazolyl rings,
the palladium center is efficiently shielded by the ethylene back-
bones, and for complexes 8 and 10 additionally by the substituents
in 5-position of the pyrazolyl groups. This effect is potentially
important for reactions in which the fifth and sixth coordination
site at palladium are involved. Accordingly, the crystal structures
of 8, 10, and 11 do not display any secondary Pdꢀ ꢀ ꢀCl, Pdꢀ ꢀ ꢀO, or
Pdꢀ ꢀ ꢀN bonds.
crystal structure determinations of 8, and 10–12 revealed a jN-
monodentate coordination of the PPA-type ligands in each case,
and the same is to be expected for 7 and 9. Consequently, the coor-
dination chemistry of PPA and related ligands with palladium(II) is
less diverse and more predictable than with first-row transition
metals, which allows for controlled and targeted bottom-up con-
struction of supramolecular hydrogen-bonded structures.
While the structures of the N-substituted derivatives 10 and 11
do not allow for further aggregation of the molecules through
hydrogen bonding, the molecules of complex 8 are linked into a
supramolecular layer structure by NAHꢀ ꢀ ꢀO bonds between the
4. Experimental section
4.1. General methods and materials
CONH
2
groups (Fig. 10). The Nꢀ ꢀ ꢀO separations are 287.0(4) pm
4.1.1. Physical methods
and therefore slightly closer than in the free Me
2
PPA ligand
Microanalyses were performed by Galbraith Laboratories, Inc.,
Knoxville, TN, USA. IR spectra were recorded on a Bruker Alpha
(
Nꢀ ꢀ ꢀO 293.6(3) pm) [21]. The bonding interactions between the
ꢁ
1
ꢁ1
layers are rather weak, being limited to unspecific van-der-Waals
interactions with the pyrazolyl-methyl groups facing each other
FT-IR using an ATR accessory between 4000 cm and 400 cm
at 2 cm
ꢁ1
resolution. NMR spectra were recorded on Bruker
(
Fig. 11). It is to be expected that PdCl
2
(PPA)
2
(7) also shows exten-
Advance 300 and 400 NMR spectrometers and analyzed using
SpinWorks 4.0.3.0. Single-crystal X-ray intensity data were col-
lected on a STOE IPDS 2 T diffractometer equipped with a 34 cm
sive aggregation through hydrogen bonding, which is a reasonable
explanation for the low solubility of this complex.

T.M. Palombo et al. / Polyhedron 171 (2019) 493–501
497
Fig. 7. Molecular structure of PdCl
2
(Me
2
PPA)
2
(8) in the crystal, showing the atom
numbering scheme. Displacement ellipsoids with 50% probability,
H atoms
attached to C atoms omitted for clarity. Symmetry operator: ’2–x, –y, –z. The Pd
atom is located on a crystallographic center of inversion at (0, 0, 0). Selected
interatomic distances (pm) and angles (deg.): Pd–Cl 229.76(4), Pd–N3 200.8(2), Cl–
0
Pd–Cl 180.00, Cl–Pd–N3 90.36(5), Cl–Pd–N’ 89.64(5), N3–Pd–N3 180.00, O–C1
122.8(2), N1–C1 133.2(3), N2–N3 135.6(2), N3–C4 133.1(2), N1ꢀ ꢀ ꢀCl 347.6(2).
iPr
Fig. 5. Representation of the supramolecular chain structures of a) PPA (3) and b)
iPr
2
Me PPA (4) in the crystal (H atoms attached to C atoms omitted for clarity).
a
image plate detector, using graphite-monochromated Mo-K radi-
ation (k = 0.71073 Å). Numerical absorption correction was applied
for the palladium complexes 8, and 10–12 [23]. The structures
were solved with SIR-97 [24] or SHELXT-2018 [25] and refined
by full matrix least-squares methods on F2 using SHELXL-2018
[
26].
2 2 2
Fig. 8. Molecular structure of PdCl (Me ) (10) in the crystal, showing the
PPAiPr
atom numbering scheme. Displacement ellipsoids with 50% probability, H atoms
attached to C atoms omitted for clarity. The Pd atom is located on a crystallographic
center of inversion at (0, 0, 0.5). Symmetry operator: ’ –x, 2–y, 1–z. Selected
interatomic distances (pm) and angles (deg.): Pd–Cl 230.31(4), Pd–N3 200.9(1), Cl–
4
.1.2. Materials
Dichloro(1,5-cyclooctadiene)palladium(II) was used as received
0
0
from Strem Chemicals. Acrylamide, N-isopropylacrylamide, diace-
tone acrylamide, bis(benzonitrile)dichloropalladium(II), and
trimethylbenzylammonium hydroxide (40% in methanol, Triton
B) were used as received from Sigma Aldrich. Chloroform (99.8%)
was used as received from Acros Organics. 3,5-Dimethylpyrazole
Pd–Cl’ 180.00, Cl–Pd–N3 90.43(4), Cl–Pd–N3 89.57(4), N3–Pd–N3 180.00, O–C1
22.7(2), N1–C1 133.7(2), N2–N3 136.1(2), N3–C4 133.3(2), N1ꢀ ꢀ ꢀCl 335.9(2).
1
in methanol, ‘‘Triton B”) were heated to reflux for 3 h. The resulting
yellow oil was dissolved in diethyl ether and cooled to –10 °C until
the product solidified. The crude product was vacuum filtered,
washed with cold diethyl ether, and dried in vacuo (5.05 g, 61%).
Crystals suitable for X-ray diffraction were obtained by recrystal-
was used as received from Fluka Analytical. PPA (1) [10] and Me
PPA (2) [21] were prepared as described in the literature.
2
-
iPr
9 15 3
lization from diethyl ether. Elem. Anal. Calcd. for C H N O
4
.1.3. Synthesis of PPA (3)
ꢁ1
(
M = 181.24 g mol ): C, 59.64; H, 8.34; N, 23.19. Found: C,
Pyrazole (3.10 g, 46 mmol), N-isopropylacrylamide (5.19 g,
6 mmol), and trimethylbenzylammonium hydroxide (1 mL, 40%
ꢁ1
5
9.00; H, 8.38; N, 22.69%. M.p. = 62 °C. IR (cm ): m = 3321 vs
4
Fig. 6. Representation of the supramolecular dimer structures of a) PPAMOP (5) and b) Me PPAMOP (6) in the crystal (H atoms attached to C atoms omitted for clarity).
2

4
98
T.M. Palombo et al. / Polyhedron 171 (2019) 493–501
(mN-H), 3134 w, 3118 w, 3075 w, 2975 vs, 2943 w, 2879 w, 1771 w,
1
1
1
638 vs ( C=O), 1543 vs ( C-N + dCNH), 1510 m. 1474 w, 1451 m,
m
m
425 w, 1401 m, 1386 s, 1366 m, 1339 w, 1282 s, 1237 s, 1215 m,
173 m, 1133 s, 1055 s, 1030 s, 970 m, 945 w, 911 m, 925 w,
11 m, 844 w, 763 vs, 684 s, 656 vs, 611 s, 488 m, 448 m, 414 s.
9
1
H NMR (400 MHz, CDCl
3
): d = 1.09 (6H, d, J = 6.58 Hz, CH(CH
-CH ), 3.99 (1H, m, J = 6.58 Hz, CH(CH
.46 (2H, t, J = 6.3 Hz, b-CH
-CH), 7.43 (1H, dd, J = 2.29 Hz, J = 0.60 Hz, CH), 7.53 (1H, dd,
3
)
2
),
2
4
4
.72 (2H, t, J = 6.3 Hz,
a
2
3
)
2
),
2
), 6.23 (1H, dd, J = 2.29 Hz, J = 1.90 Hz,
1
3
J = 1.90 Hz, J = 0.60 Hz, CH) ppm.
C NMR (100 MHz, CDCl
), 41.4 (s, b-CH ) , 48.2 (s, CH
3 2
) , 105.3 (s, 4-CH), 130.3 (s, CH), 139.7 (s, CH), 169.1 (s,
3
):
d = 22.5 (s, CH(CH
CH
3
)
2
, 37.6 (s,
a-CH
2
2
(
C@O) ppm.
Fig. 9. Molecular structure of PdCl
numbering scheme. Displacement ellipsoids with 50% probability,
2
(PPAMOP
)
2
(11) in the crystal, showing the atom
atoms
iPr
H
2
4.1.4. Synthesis of Me PPA (4)
attached to C atoms omitted for clarity. The Pd atom is located on a crystallographic
center of inversion at (0.5, 0.5, 0.5). Symmetry operator: ’ 1–x, 1–y, 1–z. Selected
interatomic distances (pm) and angles (deg.): Pd1–Cl1 229.6(1), Pd1–N1 200–2(2),
A mixture of N-isopropylacrylamide (2.86 g, 25 mmol), 3,5-
dimethylpyrazole (2.40 g, 25 mmol), and trimethylbenzylammo-
nium hydroxide (1 mL, 40% in methanol, ‘‘Triton B”) was sub-
merged in a boiling water bath for 5 h. The reaction mixture
solidified on cooling. The residue was washed with diethyl ether,
and dried in vacuo to give 4.41 g (84%) of 4. Recrystallization from
0
0
0
Cl1–Pd1–Cl1 180.00, Cl1–Pd1–N1 90.89(6), Cl1–Pd–N1 89.11(6), N1–Pd1–N1
1
1
80.00, O1–C6 122.9(2), O2–C11 120.9(2), N1–N2 135.1(2), N1–C1 133.1(2), N3–C6
33.8(2), N1ꢀ ꢀ ꢀCl 339.7(2).
2 2 2
Fig. 10. Representation of the intermolecular NAH∙∙∙O hydrogen bonds of PdCl (Me PPA) (8) viewed in a projection on (1 0 –2) (H atoms attached to C atoms omitted for
clarity). The 2D supramolecular structure extends parallel to (1 0 –2).
Fig. 11. Illustration of two proximate layers of 8 shown in Fig. 10, viewed in a projection on (0 1 0), i.e. along the planes (H atoms attached to C atoms omitted for clarity).

T.M. Palombo et al. / Polyhedron 171 (2019) 493–501
499
methylene chloride/diethyl ether (2:1) solution yielded colorless
crystals suitable for X-ray diffraction analysis. Elem. Anal. Calcd.
J = 6.62 Hz, b-CH
CDCl
(s, CH
CH ), 52.1 (s, C(CH
(s, 3-C-CH ), 170.1 (s, C@O), 207.6 (s, C@O (MOP)) ppm.
2
), 5.75 (1H, s, 4-CH) ppm. 13C NMR (100 MHz,
3
): d = 10.9 (s, 5-CH
(MOP)), 37.8 (s,
), 104.8 (s, 4-CH), 139.5 (s, 5-C-CH
3
3
), 13.4 (s, 3-CH
3
), 27.1 (s, C(CH
(MOP)), 44.3 (s, b –
), 147.8
3 2
) ), 31.6
ꢁ1
for C11
19
H N
3
O (M = 209.29 g mol ): C, 63.13; H, 9.15; N, 20.08.
3
a
-CH ), 37.9 (s, CH
2
2
Found: C, 63.18; H, 8.9; N, 20.09%. M.p. 123–125 °C. IR (ATR,
2
3
)
2
ꢁ
1
cm ):
2
1
m
= 3232 m
969 m, 2930 m, 2874 w,
490 w, 1458 s, 1430 m, 1419 m, 1380 vs, 1367 s, 1330 m, 1257
(
m
N-H), 3203 m, 3117 m, 3054 m, 2982 m,
3
m
1658 vs ( C=O), 1549 s (mC-N + dCNH),
m
w, 1340 vs, 1204 vw, 1163 m, 1132 m, 1121 m, 1055 w, 1036 w,
2 2
4.1.7. Synthesis of PdCl (PPA) (7)
1
4
016 s, 989 m, 926 w, 852 w, 818 s, 771 m, 652 s, 608 s, 588 w,
88 w, 474 m, 440 s. 1H NMR (400 MHz, CDCl
): d = 1.05 (6H, d,
), 2.22 (3H, s, 5-CH ), 2.24 (3H, s, 3-CH ),
.69 (2H, t, J = 6.45 Hz, -CH ), 3.93 (1H, sept, J = 6.58 Hz, CH
CH ), 4.23 (2H, t, J = 6.44 Hz, b-CH ), 5.78 (1H, s, 4-CH), 5.82
1H, br, s, NH) ppm. C NMR (100 MHz, CDCl ): d = 10.9 (s, 5-
), 13.4 (s, 3-CH ), 22.5 (s, CH(CH ), 37.4 (s, -CH ), 41.4 (s,
b-CH ), 44.4 (s, CH(CH ), 104.9 (s, 4-CH), 139.8 (s, 5-C-CH ),
PPA (1; 56 mg, 0.40 mmol) and dichloro(1,5-cyclooctadiene)-
palladium(II) (75 mg, 0.26 mmol) were dissolved in 25 mL of chlo-
roform and stirred under nitrogen for 3 d. The solution was
concentrated and a yellow precipitate of 7 formed to yield 71 mg
(78%). This complex is insoluble in common solvents. While it does
dissolve in DMSO, this solvent apparently displaces the ligand and
satisfactory NMR spectra could not be obtained. Elemental Anal.
3
J = 6.58 Hz, CH(CH
2
(
(
CH
3
)
2
3
3
a
2
3
)
2
2
1
3
3
3
3
3
)
2
a
2
ꢁ1
2
3
)
2
3
Calcd for C12
2 6 2
H18Cl N O Pd (M = 455.64 g mol ): C, 31.63; H,
1
47.8 (s, 3-C-CH
3
), 169.5 (s, C@O) ppm.
3.98; N, 18.44. Found: C, 31.64; H, 3.91; N, 17.93%. M.p. 133–
ꢁ1
1
35 °C. IR (ATR, cm ):
m
= 3371 m (
mN-H), 3340 m, 3190 m, 3120
MOP
4.1.5. Synthesis of PPA
(5)
w, 2918 w, 2360 m, 2342 w, 1658 vs (
m
C=O), 1616 m (mC-N + dCNH),
A mixture of pyrazole (1.36 g, 20 mmol), diacetone acrylamide
3.39 g, 20 mmol), and trimethylbenzylammonium hydroxide
1.2 mL, 40% in methanol, ‘‘Triton B”) was heated for 3 h in a water
1520 m, 1430 w, 1415 s, 1372 m, 1302 m, 1270 m, 1217 m, 1191
w, 1173 w, 1116 w, 1088 m, 1041 w, 1013 w, 938 w, 901 w, 864
w, 794 w, 777 w, 760 s, 668 w, 654 w, 604 w, 535 m, 473 m.
(
(
bath maintained at 44–47 °C. A white solid formed after cooling to
room temperature, which was washed three times with diethyl
ether. After three recrystallizations from diethyl ether/hexanes,
2 2 2
4.1.8. Synthesis of PdCl (Me PPA) (8)
2
.94 g (62%) of 5 was obtained. Single crystals suitable for X-ray
Me PPA (2; 86 mg, 0.50 mmol) and dichloro(1,5-cyclooctadi-
2
diffraction were obtained following these recrystallizations. Elem.
ene)palladium(II) (73 mg, 0.26 mmol) were dissolved in 20 mL of
chloroform and stirred under nitrogen for 3 d. Evaporation of the
solvent yielded 89 mg (75%) of an orange solid. Yellow needle-like
crystals suitable for X-Ray diffraction were obtained from a metha-
ꢁ
1
Anal. Calcd. for C12
H
19
N
3
O
2
(M = 237.30 g mol ): C, 60.74; H,
8
7
3
1
1
1
8
.07; N, 17.71; Found: C, 60.97; H, 8.21; N, 17.72%. M.p. 74–
ꢁ1
6 °C. IR (ATR, cm ):
051 m, 2979 m, 2941 m, 1697 vs (
543 s ( C-N + dCNH), 1515 m, 1467 m, 1439 m 1410 m, 1401 m,
m
= 3256 m
(
m
N-H), 3214 m, 3132 w,
m
C=O, MOT), 1675 vs ( C=O),
m
nol solution by slow evaporation. Elemental Anal. Calcd. for C16-
ꢁ1
m
H26Cl
2
6
N O
2
Pd (M = 511.75 g mol ): C, 37.55; H, 5.12; N, 16.42.
384 m, 1372 m, 1360 m, 1319 m, 1281 m, 1252 m, 1206 m,
183 m, 1153 m, 1130 m, 977 m, 950 m, 935 m, 918 m, 895 m,
Found: C, 37.50; H, 5.21; N, 16.0%. M.p. 261.2–263.5 °C. IR (ATR,
ꢁ
1
cm ):
C=O), 1554 w, 1470 w, 1414 m, 1395 m, 1351 w, 1316 w,
1258 s, 1206 w, 1086 w, 1013 s, 864 w, 792 s, 702 w, 660 w,
m = 3384 m (mN-H), 3166 m, 2962 m, 1704 m, 1687 w
41 m, 772 vs, 753 vs, 670 m, 651 m, 616 m, 563 m, 537 m, 498
(m
1
w, 484 w, 479 w, 476 w, 466 w, 462 w, 456 w. H NMR
1
(
400 MHz, Acetone-d
6
): d = 1.32 (6H, s, C(CH
-CH ), 2.96 (2H, s, CH
), 6.17 (1H, dd, J = 1.8 Hz, J = 2.2 Hz,
-CH), 6.89 (1H, br, s, NH), 7.39 (1H, dd, J = 0.6 Hz, J = 1.8 Hz, 3-
3
)
2
), 2.02 (3H, s, CH
3
602 m, 532 w, 476 m. H NMR (400 MHz, CDCl
5-CH ), 2.83 (3H, s, 3-CH ), 3.79 (2H, t, J = 6.38 Hz,
(2H, t, J = 6.38 Hz, b-CH ), 5.14 (1H, s, br, NH), 5.91 (1H, s, 4-CH),
6.38 (1H, s, br, NH) ppm. C NMR (100 MHz, CDCl
CH ), 15.1 (s, 3-CH ), 36.1 (s, -CH ), 45.3 (s, b-CH
CH), 145.1 (s, 5-C-CH ), 150.4 (s, 3-C-CH ), 172.0(s, C@O) ppm.
3
): d = 2.35 (3H, s,
(
MOP)), 2.65 (2H, t, J = 6.73 Hz,
a
2
2
(MOP)),
3
3
a
-CH ), 4.98
2
4
4
.36 (2H, t, J = 6.73 Hz, b-CH
2
2
1
3
3
): 11.8 (s, 5-
2
), 107.6 (s, 4-
1
3
CH), 7.57 (1H, dd, J = 2.2 Hz, J = 0.6 Hz, 5-CH) ppm. C NMR
100 MHz, Acetone-d ): d = 26.6 (s, C(CH ), 30.7(s, CH (MOP)),
7.0 (s, -CH ), 47.7 (s, b-CH ), 50.4 (s, CH (MOP)), 51.6 (s, C
CH ), 104.5 (s, 4-CH), 129.4 (s, 3-CH), 138.5 (s, 5-CH), 169.3 (s,
3
3
a
2
(
3
(
6
3
)
2
3
3
3
a
2
2
2
3 2
)
iPr
C@O), 206.3 (s, C@O (MOP)) ppm.
2 2
4.1.9. Synthesis of PdCl (PPA ) (9)
iPr
PPA (3; 91 mg, 0.50 mmol) and dichloro(1,5-cyclooctadiene)-
palladium(II) (75 mg, 0.26 mmol) were dissolved in 20 mL of chlo-
roform and stirred under nitrogen for three days. Evaporation of
the solvent yielded 92 mg (68%) of an orange solid that was
washed with diethyl ether and dried in vacuo. Elemental Anal.
MOP
4
.1.6. Synthesis of Me
2
PPA
(6)
A mixture of 3,5-dimethylpyrazole (2.85 g, 33 mmol), diacetone
acrylamide (5.04 g, 33 mmol), and trimethylbenzylammonium
hydroxide (1 mL, 40% in methanol, ‘‘Triton B”) was heated to reflux
for 2.5 h. The reaction mixture was cooled to room temperature
producing a waxy solid. The solid was triturated with two 10 mL
aliquots of diethyl ether yielding 6 as a white solid (4.67 g, 59%).
Single crystals appropriate for X-Ray diffraction were obtained by
recrystallization from diethyl ether. Elem. Anal. Calcd. for
ꢁ1
Calcd for C18
2 6 2
H30Cl N O Pd (M = 539.80 g mol ): C, 40.05; H,
5.60; N, 15.57. Found: C, 40.54; H, 4.81; N, 15.09%. M.p. 193–
ꢁ1
195 °C. IR (ATR, cm ):
m = 3375 s (mN-H), 1665 m, 1635 s (mC=O),
1564 s ( C-N + dCNH), 1519 w, 1464 w, 1439 m, 1414 m, 1386 w,
m
1356 m, 1344 w, 1318 w, 1283 m, 1263 m, 1248 m, 1224 w,
1176 w, 1160 w, 1130 w, 1106 w, 1083 s, 1057 w, 1008 w, 988
ꢁ1
C
14
H
23
N
3
O
2
(M = 265.36 g mol ): C, 63.37; H, 8.74; N, 15.84.
Found: C, 63.08, H, 8.57, N, 15.43%. M.p. 99–100 °C. IR (ATR,
w, 961 w, 939 w, 896 w, 840 w, 783 w, 768 vs, 714 w, 677 w,
ꢁ1
1
cm ):
m
m
= 3246 w (
m
N-H), 3048 w, 2999 w, 2966 w, 2935 w,
C=O), 1552 vs (
621 m, 575 m, 518 w, 455 w, 417 m. H NMR (400 MHz, CDCl
3
):
1
1
1
702 s (
C=O
,
MOP) , 1672 vs (
m
m
C-N + dCNH),
d = 0.92 (6H, d, J = 6.58 Hz, CH(CH
CH ), 3.84 (1H, sept, J = 6.58 Hz, CH(CH
J = 6.23 Hz, b-CH ), 6.19 (2H, s, br, NH), 6.35 (1H, t, J = 2.58 Hz, 4-
CH), 7.55 (1H, dd, J = 2.58 Hz, J = 0.89 Hz, 3-CH), 7.80 (1H, dd,
3
2
) ), 3.63 (2H, t, J = 6.23 Hz,
a-
468 m, 1440 m, 1429 m, 1412 m, 1380 s, 1361 s, 1354 s, 1299 m,
251 s, 1207 m, 1175 w, 1150 w, 1129 w, 1054 w, 1032 w, 992
2
3 2
) ), 5.06 (2H, t,
2
w, 944 w, 893 w, 839 w, 791 s, 732 w, 706 w, 673 w, 653 w, 630
1
13
w, 613 w, 600 w, 569 m, 538 m, 529 w, 510 w, 504 w. H NMR
J = 2.58 Hz, J = 0.89 Hz, 5-CH) ppm. C NMR (100 MHz, CDCl
d = 22.3 (s, CH(CH ), 37.3 (s, -CH ), 41.3 (s, b-CH ), 49.9 (s, CH
(CH , 107.4 (s, 4-CH), 135.7 (s, 3-CH), 143.3 (s, 5-CH), 168.0 (s,
C@O) ppm.
3
):
(
(
400 MHz, CDCl
MOP)); 2.20 (3H, s, 5-CH
-CH ), 2.89 (2H, s, CH
2
3
): d = 1.30 (6H, s, C(CH
), 2.23 (3H, s, 3-CH
(MOP)), 4.19 (2H, t,
3
)
2
), 2.05 (3H, s, CH
3
3
)
2
a
2
2
3
3
), 2.66 (2H, t,
3 2
)
J = 6.62 Hz,
a
2

5
00
T.M. Palombo et al. / Polyhedron 171 (2019) 493–501
iPr
), 5.90 (1H, s, 4-CH), 6.52 (2H, s, br, NH) ppm. 13
): d = 11.8 (s, 5-CH ), 15.1 (s, 3-CH ), 26.5
(MOP)), 37.7 (s, -CH ), 45.4 (s, b-CH ),
), 107.3 (s, 4-CH), 145,1 (s, 5-
4
.1.10. Synthesis of PdCl
2
(Me
2
PPA
)
2
(10)
J = 6.2 Hz, b-CH
NMR (100 MHz, CDCl
(s, C(CH ), 31.5 (s, CH
51.0 (s, CH (MOP)), 52.1 (s, C(CH
C-CH ), 150.3 (s, 3-C-CH ), 169.1 (s, C@O), 206.9 (s, C@O (MOP))
ppm.
2
C
iPr
Me
2
PPA (4(79 mg, 0.38 mmol) and dichloro(1,5-cyclooctadi-
3
3
3
ene)palladium(II) (73 mg, 0.25 mmol) were dissolved in 20 mL of
chloroform and stirred under nitrogen for three days. Evaporation
of the solvent yielded 141 mg (94%) of orange crystals suitable for
X-ray diffraction analysis. Elemental Anal. Calcd. for C22H38Cl N -
2 6
2
O Pd (M = 595.91 g mol ): C, 44.34; H, 6.43; N, 14.10%. Found:
C, 44.09; H, 6.22; N, 13.66. M.p. 226 °C. IR (ATR, cm ):
vs, 3143 w, 3064 w ( N-H); 2972 s, 2931 w ( C-H), 1668 vs (
C-N + dCNH), 1459 s, 1436 w, 1411 s, 1387 m, 1367 m,
334 w, 1297 m, 1262 s, 1234 m, 1182 s, 1164 s, 1138 w, 1129 w,
096b, 1070 w, 1044 w, 1018 w, 960 w, 920 w, 890 w, 866 w,
3
)
2
3
a
2
2
2
3 2
)
3
3
ꢁ1
ꢁ
1
m = 3294
Acknowledgments
m
m
mC=O),
1
1
1
7
4
543 s (m
The material is based on work supported by the National
Science Foundation – United States under CHE-1062629 and
1
461175. General financial support of this work by the Otto-von-
98 vs, 741 m, 674 s, 659 s, 639 m, 630 m, 596 m, 585 m, 573,
Guericke-Universität Magdeburg is also gratefully acknowledged.
1
52 m, 434 m.
H
NMR (400 MHz, CDCl
), 2.33 (3H, s, 5-CH ), 2.83 (3H, s, 3-CH
.72 (2H, t, J = 6.32 Hz, -CH ), 3.81 (1H sept, J = 6.57 Hz, CH
CH ), 4.92 (2H, t, J = 6.32 Hz, b-CH ), 5.89 (1H, s, 4-CH), 6.49
2H, s, br, NH) ppm. C NMR (100 MHz, CDCl ): d = 12.0 (s, 5-
-CH ), 41.5 (s, b-
), 107.5 (s, 4-CH), 145.3 (s, 5-C-CH ), 150.1
3
): d = 0.90 (6H, d,
J = 6.57 Hz, CH(CH
3
(
(
CH
CH
3
)
2
3
3
),
a
2
Appendix A
3
)
2
2
1
3
3
CCDC 1912534–1912540 (cf. Table 1) contains the supplemen-
tary crystallographic data for the compounds reported in this
paper. These data can be obtained free of charge via http://www.
ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crys-
tallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
3
), 15.2 (s, 3-CH
3
), 22.2 (s, CH(CH
3
)
2
), 37.3(s,
a
2
2
), 45.6 (s, CH(CH
3
)
2
3
(
s, 3-C-CH
3
) , 168.3 (s, C@O) ppm.
MOP
4.1.11. Synthesis of PdCl
2
(PPA
2
) (11)
MOP
A solution of PPA
(5; (172 mg, 0.72 mmol) and dichloro(1,5-
cyclooctadiene)palladium(II) (104 mg, 0.36 mmol) in 40 mL of ace-
tone was refluxed for 1 h under a nitrogen atmosphere. Volatile
components were removed in vacuum and the remaining solid
was recrystallized from methylene chloride/hexanes to yield
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