New palladium (II) complexes containing phosphine-nitrogen ligands and their use as catalysts in aminocarbonylation reaction

Article abstract of DOI:10.1002/aoc.4709

Aminocarbonylation of aryl halides, homogeneously catalysed by palladium, is an efficient method that can be employed for obtaining amides for pharmaceutical and synthetic applications. In this work, palladium (II) complexes containing P^N ligands were studied as catalysts in the aminocarbonylation of iodobenzene in the presence of diethylamine. Two types of systems were used: a palladium (II) complex formed in situ; and one prepared prior to the catalytic reaction. In general, the palladium complexes studied achieved high conversions in an average reaction time of less than 2 hr, which is less than that for the standard system (Pd (II)/PPh₃) used. The pre-synthesized complexes were faster than their in situ counterparts, as the latter require an induction time to form the Pd/P^N species. The structure and electronic properties of the ligand P^N can influence both the activity and the selectivity of the reaction, stabilizing the acyl-palladium intermediates formed in a better manner.

Full text of DOI:10.1002/aoc.4709

Received: 23 August 2018
DOI: 10.1002/aoc.4709
Revised: 10 October 2018
Accepted: 25 October 2018
F U L L P A P E R
New palladium (II) complexes containing phosphine‐
nitrogen ligands and their use as catalysts in
aminocarbonylation reaction
Braulio Aranda1,4 | Sergio A. Moya2 | Andres Vega3 | Gonzalo Valdebenito4 |
Sofia Ramirez‐Lopez4 | Pedro Aguirre4
1 Departamento de Ciencias Químicas y
Aminocarbonylation of aryl halides, homogeneously catalysed by palladium, is
an efficient method that can be employed for obtaining amides for pharmaceu-
tical and synthetic applications.
Recursos Naturales, Facultad de
Ingeniería y Ciencias, Universidad de la
Frontera, Temuco, Chile
2 Departamento de Ciencias de los
Materiales, Facultad de Química y
Biología, Universidad de Santiago de
Chile, Santiago, Chile
3 Departamento de Ciencias Químicas,
Facultad de Ciencias exactas, Universidad
Andrés Bello, Santiago, Chile
4 Departamento de Química Inorgánica y
Analítica, Facultad de Ciencias Químicas
y Farmacéuticas, Universidad de Chile,
Santiago, Chile
In this work, palladium (II) complexes containing P^N ligands were studied as
catalysts in the aminocarbonylation of iodobenzene in the presence of
diethylamine. Two types of systems were used: a palladium (II) complex
formed in situ; and one prepared prior to the catalytic reaction. In general,
the palladium complexes studied achieved high conversions in an average
reaction time of less than 2 hr, which is less than that for the standard system
(Pd (II)/PPh3) used. The pre‐synthesized complexes were faster than their in
situ counterparts, as the latter require an induction time to form the Pd/P^N
species. The structure and electronic properties of the ligand P^N can
influence both the activity and the selectivity of the reaction, stabilizing the
acyl‐palladium intermediates formed in a better manner.
Correspondence
Pedro Aguirre, Departamento de Química
Inorgánica y Analítica, Facultad de
Ciencias Químicas y Farmacéuticas,
Universidad de Chile, Santiago, Chile.
Email: paguirre@ciq.uchile.cl
KEYWORDS
amide synthesis, aminocarbonylation, aryl halide, palladium complex, phospho‐nitrogen ligands
Funding information
Fondo Nacional de Desarrollo Científico y
Tecnológico, Grant/Award Number:
1160505; CONICYT‐Chile, Grant/Award
Numbers: 21140223, 21110568 and
1160505
1 | INTRODUCTION
For this reaction, palladium (II) catalysts formed in
situ are currently used by reaction of a palladium (II)
Palladium (II) catalysts have been used in the synthesis
of amides since when Heck reported synthesis from aryl
halides.[1–3] These aromatic amides can be used as
synthesis blocks in the polymerization of products of
pharmacological interest.[4–7] For example, 13α‐steroid
amide products that are pharmacologically significant
have been synthesized using homogeneous palladium
catalysts.[8,9]
precursor and a ligand such as PPh3. Palladium (II) com-
plexes containing bidentate P^P ligands that have been
studied as catalysts in aminocarbonylation show high
activity but in a longer time compared with a standard
catalyst Pd (II)/PPh3, as the ligand stabilizes the Pd (0)/
P^P species too much, hindering the oxidative addition
of the substrate. Other bidentate ligands, such as the
P^N ligands, combine the properties of phosphorus and
Appl Organometal Chem. 2019;e4709.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
1 of 9
https://doi.org/10.1002/aoc.4709

2 of 9
ARANDA ET AL.
nitrogen to give the ligand potential hemilabile
and bifunctional properties. These ligands have been
successfully studied as part of catalytic systems where
the properties of the ligand can influence both the
activity and selectivity of the reaction. In this work,
aminocarbonylation of aryl halides has been reported
using new palladium (II) catalysts containing P^N
ligands. The activity of the complexes used was compared
with a Pd (II)/PPh3 catalyst. All the catalysts that were
studied reached 100% conversion and two major products
were obtained: amide (a) and amide (b) (Scheme 1).
The results obtained show that the favoured product
was amide (b), with the best results being obtained with
the catalyst [Pd(L1)Cl2] (92% conversion with a 95%
selectivity towards amide (b) after 2 hr), and that the
electronic properties of the ligand can also influence both
activity and chemoselectivity.
This is attributed to the pKa of the substrate (pKa 2‐
picolineamine = 8.6),[13] which is lower than the standard
for heterocyclic amines used as precursors (pKa ~ 13).[14]
This double deprotonation led to a modification in the
synthetic route using a stoichiometric amount of Et3N
for the synthesis of L1.
After purification, single monocrystals from the oxide
of L1 ligand were obtained from the washing mixture and
resolved via X‐ray diffraction (Figure 2; Table 1). P^N
ligands are known to be air‐sensitive in solution, which
2 | RESULTS AND DISCUSSION
2.1 | Synthesis
For this study, new P^N ligands were prepared based on
previous experiences (Figure 1).[10–12] In the case of
ligand L1 (Scheme 2), it was found that the usual excess
of Et3N used for its synthesis[10] could deprotonate
the amine group of the precursor entirely, leading to the
formation of a bis‐diphenylphosphine (evidenced by the
31P‐NMR shift in 62.57 ppm).
FIGURE 2 Molecular structure of the oxide of L1 with ellipsoids
drawn at 30% probability level. Hydrogen atoms and solvent
molecules are omitted for clarity
TABLE 1 Selected bond lengths and angles for oxide of L1
Bond
Bond length (Å)
Bond
Bond angle (°)
N2‐P2
1.646(7)
1.429(11)
1.457(7)
1.799(8)
1.806(8)
P2‐N2‐C39
N2‐P1‐C13
N2‐P2‐O1
118.9(6)
103.5(3)
112.7(4)
108.7(4)
N2‐C39
P2‐O1
SCHEME
1
Iodobenzene aminocarbonylation catalysed by
P2‐C13
Pd‐C31
C13‐P2‐C31
palladium (II) complexes, which yield amides a and b as major
products
FIGURE 1 P, N‐donor ligands used for aryl halide aminocarbonylation
SCHEME 2 Synthesis of phosphorus‐
nitrogen ligands

ARANDA ET AL.
3 of 9
TABLE 2 Selected bond lengths and angles for complex [Pd(L7)
Cl2]
leads to oxidation of the phosphine group. The resolved
structure shows that one diphenylphosphine group
linked the amine moiety of the pyridine‐derived substrate
through nucleophilic substitution, which was the main
goal. 31P‐NMR analysis confirmed that L1 ligand has a
non‐oxidized diphenylphosphine group, showing a signal
at 23.9 ppm, which is consistent with other P^N ligands,
unlike its oxide that shows a higher shift at 42.2 ppm.
Regarding ligands L4–L6, Et3N was not used for their
synthesis because it forms a stable product with the
substrate by avoiding nucleophilic substitution. Instead,
a second equivalent of aminoquinoline was used to neu-
tralize the formed HCl.[15] The L7 ligand was prepared
according to literature,[16] yielding a white product
Bond
Bond length (Å) Bond
Bond angle (°)
Pd1‐Cl1
Pd1‐Cl2
Pd1‐P1
Pd1‐N1
Pd1‐O2
2.2827(15)
2.3799(15)
2.1738(14)
2.079(3)
Cl1‐Pd1‐Cl2
89.69(5)
91.61(5)
Cl1‐Pd1‐P1
Cl1‐Pd1‐N1
Cl2‐Pd1‐P1
Cl2‐Pd1‐N1
P1‐Pd1‐N1
P1‐O2‐Cqn
175.35(10)
170.82(5)
92.93(10)
86.40(10)
122.8(3)
1.613(3)
Pd1‐‐‐Cl2 3.9189(18)
between the palladium centre and a chloride ligand from
another complex [Pd1‐Cl21 = 3.9189(18) Å] may suggest
the formation of a coordination dimer or polymer, which
would explain the low solubility of almost all the palla-
dium (II) complexes studied in this work (Figure 3, right).
This interaction might be broken when one of these chlo-
rides are substituted by dimethylformamide (DMF) or
dimethylsulphoxide (DMSO), which can enter the coordi-
nation sphere of the metal when they are used as solvents.
1
confirmed by H‐ and 31P‐NMR.
Palladium (II) complexes containing P^N ligands
were prepared according to the literature[9–12] using
PdCl2 as precursor. Palladium complexes based on Pd
(OAc)2 were also prepared with the aim of studying these
complexes as catalysts, as the use of in situ palladium ace-
tate systems is widely known.[12,17–19] Further, 31P‐NMR
analysis yielded no signals of coordinated phosphine nor
any signal at all, so no Pd(P^N)(OAc)2 complexes were
studied in this work.
All prepared complexes, with the exception of [Pd(L7)
Cl2], are insoluble in most organic solvents; the presence
of an oxygen atom in the structure of ligand L7 is proba-
bly responsible for its better solubility in chloroform and
dichloromethane. This allowed to obtain monocrystals
of [Pd(L7)Cl2] (Figure 3; Table 2).
From the data obtained, it is confirmed that the P^N
ligands coordinate in a bidentate manner with the palla-
dium centre, forming a distorted planar square complex.
The bite angle of the chelating ring formed by ligand L7
is 86°, slightly greater than the bite angle of P^N ligands,
which form a five‐membered ring. The distance found
2.2 | Catalytic studies
Catalytic results are summarized in Table 3. For this
study, a Pd (II)/PPh3 catalyst was used as reference
(Table 3, entry 1), and two synthesis approaches were
followed: forming the Pd (II)/P^N complex in situ (mixing
the reactants in the reaction medium); and using a previ-
ously synthesized palladium (II) complex. Iodobenzene
was used as a substrate as it is commonly used as a refer-
ence for these types of studies. On the other hand, the
catalytic reaction was studied using palladium (II) acetate
as precursor as in situ catalyst, while palladium
FIGURE 3 Molecular structure of complex Pd(L7)Cl2 with ellipsoids drawn at 30% probability level. Hydrogen atoms and solvent
molecules are omitted for clarity

4 of 9
ARANDA ET AL.
TABLE 3 Aryl halide aminocarbonylation with palladium (II)
complexes
formation of the corresponding Pd (0) complex, which is
the active catalytic species for this reaction.
Entry Catalyst
Conv. (%) Time (hr) k (hr−1
Pd + PPh3 96
)
a:b
1
4
2
3
3
2
2
3
3
2
4
3
2
3
2
2
0.76
1.15
0.63
1.02
1.63
1.62
0.91
1.08
1.33
0.84
1.52
1.65
1.54
1.32
1.62
29/71
5/95
3 | INFLUENCE OF P^N LIGAND
2
Pd + L1
Pd + L2
Pd + L3
Pd + L4
Pd + L5
Pd + L6
Pd + L7
92
98
96
97
98
93
96
In this work, several P^N ligands share the same general
structure, which makes it interesting to study the electronic
effects caused by the presence of different groups. For
example, L1 lacks the amide group that L2 possesses, and
L3 has a pyrazine heterocycle instead of the pyridine cycle
found in ligands L1 and L2. Pd (II) catalysts containing L1
achieved higher reaction rates than palladium catalysts
containing L2, both in situ and pre‐synthesized, as shown
by the calculated k constant (Table 3, entries 2, 3, 9 and 10).
It seems that the presence of an electron‐withdrawing
group in the structure of the ligand, such as an amide moi-
ety, negatively affects the catalyst activity; in situ palladium
(II) catalysts have a lower k constant compared with even
the reference experiment using Pd/PPh3 catalyst.
3
40/60
39/61
14/86
16/84
14/86
25/75
5/95
4
5
6
7
8
9
[Pd(L1)Cl2] 91
[Pd(L2)Cl2] 97
[Pd(L3)Cl2] 99
[Pd(L4)Cl2] 97
[Pd(L5)Cl2] 99
[Pd(L6)Cl2] 94
[Pd(L7)Cl2] 96
10
11
12
13
14
15
32/68
28/72
34/66
40/60
14/86
34/66
This drawback is overcome by adding a second nitro-
gen atom to the structure of the ligand as observed with
catalysts containing L3, which have similar k constants
to Pd/L1 catalysts (Table 3, entries 4 and 11), indicating
that the pyrimidine group influences the reaction in the
opposite direction of the effect of the amide group.
Ligands P^N can stabilize early reaction states, such as
the formation of the catalytic species of Pd (0), evidenced
by the absence of black palladium (0). The presence of an
additional electron‐donating group improves the stability,
while an electron‐withdrawing group can hinder it.
The same effect can be observed in the
chemoselectivity, where amide (b) constitutes almost
the entire product that is formed when a catalyst contain-
ing L1 is used; instead, using ligands L2 and L3 leads to a
more even selectivity.
According to the mechanism proposed by Csók
et al.[21] (Figure 4), chemoselectivity is defined as when
the acyl palladium intermediary undergoes aminolysis
[to produce amide (a)] or a second molecule of CO is
coordinated, resulting in amide (b) (Figure 4). If the
ligand P^N can better stabilize the intermediate, it will
be more likely to enter a second molecule of CO, whereas
the presence of an electron‐withdrawing group in the
ligand P^N stabilizes in a lesser way, relatively increasing
the production of amide (a).
Pd = Pd (OAc)2 (0.075 mmol), L = 0.075 mmol, palladium catalyst (0.075
mmol), iodobenzene 7.5 mmol, Et2NH 22.5 mmol, Et3N 1.5 mL, DMF 10
mL, CO 30 bar, T 90°C. a = phenyl acetamide; b = oxo‐phenyl acetamide.
complexes were synthesized from palladium (II) chloride.
Nevertheless, when using PdCl2 instead of Pd (OAc)2, it
behaves closely like the palladium acetate system, achiev-
ing 93% conversion after 4 hr of reaction and with a
chemoselectivity towards amide (b) of 96%.
According to these results, all Pd (II) catalysts con-
taining P^N ligands achieved near complete conversion
after 3 hr of reaction on average, while reference Pd
(II)/PPh3 catalyst required 4 hr to achieve the same con-
version (Table 3, entry 1), which is consistent with results
reported in literature.[12,17–19]
In all entries, Pd (II) catalysts remained in homoge-
neous phase in the course of the reaction; it seems that
the P^N ligand forms a stable Pd (0) complex, avoiding
the formation of palladium (0) (black) in the reductive
carbon monoxide atmosphere.[20]
Overall, palladium (II) complexes synthesized prior to
their study are faster catalysts than in situ systems
containing the same P^N ligand, as evidenced by the
calculated pseudo first‐order kinetic rates (k, Table 3); how-
ever, these k rates can be only used as references as they
were calculated only with a few points. These values sug-
gest that in situ catalysts require an induction time in which
the palladium (II)/P^N donor species is formed prior to its
reduction to a palladium (0) complex.[20,21] This induction
time is apparently neglected or eliminated by using the
already formed Pd (II)/P^N species, leading directly to the
Both catalysts prepared in situ and those prepared
prior to their use as catalysts show the same selectivity
when compared with systems using the same ligand. This
may be due to the fact that they form the same interme-
diary, resulting in the same proportion of products.
Palladium catalysts containing ligands L4 and L5
showed the highest conversion rate in this study,

ARANDA ET AL.
5 of 9
FIGURE 4 Mechanism of aminocarbonylation reaction
achieving almost complete conversions after 2 hr of reac-
tion with both in situ and prior‐synthesized methodolo-
gies (Table 3, entries 5, 6, 12 and 13). A more
conjugated ligand could better stabilize the initial states
of the reaction as compared with simpler ligands.
It is worth noting that ligand L4 forms a five‐member
chelating ring with the metallic centre, while L5 forms a
six‐member chelating one, which slightly increases the
bite angle according to what can be observed with
[Pd(L7)Cl2]. However, catalysts containing ligands L4
and L5 achieve the same activity and selectivity, which
implies that the change is less important than the elec-
tronic and steric properties of the ligand. The steric effect
can be observed with the in situ catalyst Pd + L6, which
shows a longer induction time compared with Pd + L4,
whereas the corresponding previously formed complex
does not show greater differences with respect to
[Pd(L4)Cl2], considering that both ligands form the same
coordination ring.
the potential stabilization of the palladium (0) species,
which leads to a longer induction time. In contrast,
[Pd(L7)Cl2] shows no signs of this effect, as both activity
and chemoselectivity are close to palladium complexes,
containing quinoline amine‐derived ligands.
4 | EFFECT OF THE AUXILIARY
LIGAND AND LOW CO PRESSURE IN
THE AMINOCARBONYLATION
REACTION
Several carbonylation reactions can only be carried out in
the presence of an auxiliary ligand, usually PPh3, even
when working with P^N heterobidentated ligands.[22]
This ligand is oxidized in the formation of the catalytic
palladium (0) species, reducing it, and avoiding the
formation of metallic palladium (0). To establish the
necessity of an auxiliary ligand in this study, three
catalytic systems were selected and an equivalent of
PPh3 (0.075 mmol) was added in situ. Results are resumed
in Table 4.
Meanwhile, the in situ generated catalyst Pd + L7
exhibits similar behaviour for catalysts containing L2 with
a lower k constant. The presence of an electron‐
withdrawing atom in the structure of the ligand lowers

6 of 9
ARANDA ET AL.
TABLE 4 Aminocarbonylation using PPh3 as auxiliary ligand
TABLE 5 Low CO pressure studies with selected in situ Pd/P^N
catalysts
Aux.
ligand (hr)
Time Conv. TOF
Entry Catalyst
(%)
(hr−1
)
a:b
CO pressure
(bar)
Time
(hr)
Conv.
(%)
Entry
Catalyst
a:b
1
2
3
4
5
6
Pd + L3
Pd + L3
Pd + L5
Pd + L5
PPh3
–
3
3
3
2
2
2
90
96
98
98
90
96
30
32
33
49
45
48
29/71
39/61
25/75
16/84
34:66
36:64
1
2
3
4
Pd + L3
Pd + L3
Pd + L4
Pd + L4
5
30
5
3
3
3
2
44
96
60
97
57/43
39/61
72/28
16/84
PPh3
–
30
[Pd(L7)Cl2] PPh3
[Pd(L7)Cl2]
Pd = Pd (OAc)2 (0.075 mmol), L = 0.075 mmol, palladium catalyst (0.075
mmol), iodobenzene 7.5 mmol, Et2NH 22.5 mmol, Et3N 1.5 mL, DMF 10
mL, T 90°C. a = phenyl acetamide; b = oxo‐phenyl acetamide.
–
Pd = Pd (OAc)2 (0.075 mmol), L = 0.075 mmol, palladium catalyst (0.075
mmol), iodobenzene 7.5 mmol, Et2NH 22.5 mmol, Et3N 1.5 mL, DMF 10
mL, CO 30 bar, T 90°C. a = phenyl acetamide; b = oxo‐phenyl acetamide.
palladium (II) species is reduced by the CO atmo-
sphere;[20] a lower CO availability leads to a slower reduc-
tion process. There is a change in the chemoselectivity in
both cases, in which more amide (a) is produced. This is
expected as a high CO pressure would force the insertion
of a second monoxide molecule into the catalytic cycle.
However, this change is notorious in the case of Pd +
L4, yielding amide (a) in a 4:1 ratio. On the other hand,
catalyst containing L3 achieved an a/b ratio more closely
balanced. These results imply that structural differences
in the P^N ligand could affect which pathway will follow
the catalytic cycle. A more conjugated ligand, such as L4,
will stabilize acyl‐palladium intermediates better under
high‐pressure conditions, whereas a P^N ligand with a
minor conjugation will stabilize at lower or higher CO
pressure at the same level.
Aminocarbonylation reactions have been studied by
several authors in order to obtain carboimines,
amidoimidazopyridine and 2‐ynamides.[23–25] The reac-
tion has been catalysed using palladium complexes con-
taining phosphine and diphosphine ligands. The
catalysts studied showed high conversions; however, the
time reaction was in the range of 5–12 hr. The advantage
of palladium complexes containing phosphorus‐nitrogen
ligands reported here is that the catalysts show high
conversions in a short reaction time (1 hr). Palladium
complexes containing P^N heterobidentate ligands show
advantages in aminocarbonylation reactions, where the
ligand (by combining the hard and soft properties of the
nitrogen and phosphorus atoms) favours the coordination
effect on the metal during the catalytic reaction. These
effects could favour the formation of the catalytic inter-
mediate in the aminocarbonylation reaction.
All the studied systems achieved high conversions
after 3 hr of reaction. However, when an additional
equivalent of PPh3 is added to in situ catalysts (Table 4,
entries 1 and 3), there is a slight change in the activity
and chemoselectivity; for example, the catalytic system
containing L5 + PPh3 took longer to achieve the same
conversion compared with the same system without the
auxiliary ligand. In both in situ entries, chemoselectivity
is similar to the observed when a standard Pd/PPh3 cata-
lyst is used. On the other hand, when the same auxiliary
ligand is added to a palladium complex (Table 4, entries 5
and 6), no significant changes are observed.
These results suggest that, for this study, the reduc-
tion step of the catalytic species does not need an auxil-
iary ligand that could act as a reducing agent. Instead,
when PPh3 is added to in situ catalysts, it acts competi-
tively with P^N ligands in the induction step, yielding a
Pd (0)/PPh3 active species. This is verified when a Pd
(II) complex is used as catalyst, as the coordinate species
is already formed; the same ligand competition was
reported in octene hydrosterification carried by palla-
dium (II) catalysts.[23] It also suggests that the reduction
process might be carried out by the highly reductive CO
atmosphere, where the P^N ligand is useful to stabilize
the catalytic intermediate species.[20]
Catalytic experiments resumed in Table 3 were car-
ried out at high CO pressure with the goal to compare
with previously reported works.[7–9,17–20] In all entries,
amide (b) is the favoured product. To establish what the
influence of the CO pressure is in this behaviour, two in
situ systems using ligands L3 and L4 (both with high
activities and chemoselectivities at high CO pressure)
were studied at the minimum pressure allowed by the
reactors (approximately 5 bar). Catalytic results are
resumed in Table 5.
5 | CONCLUSIONS
In both low‐pressure experiments, activities were
lower than their higher‐pressure counterparts. This can
be attributed to a slower reduction step, in which the
The palladium (II)/P^N complexes studied in this work
are active catalysts in the aminocarbonylation of
iodobenzene, and are usually faster than the reference

ARANDA ET AL.
7 of 9
catalyst Pd (II)/PPh3. The performance of the catalysts
can be improved by using a more conjugated P^N ligand
or more electron‐donating fractions. Complexes prepared
prior to their use as catalysts are faster than their in situ
counterparts, as the ligand is already coordinated with
the metal centre, reducing the induction time to form
the palladium (0) species. The main factor of the
chemoselectivity is the CO pressure; however, the ligand
can mildly influence the selectivity by better stabilizing
the intermediate that leads to the formation of amide
(b). The use of ligand P^N also prevents the formation
of black palladium, which is not catalytically active. The
optimal Pd (II) catalyst found in this study is the complex
[Pd(L1)Cl2], which gives a 91% conversion in only 2 hr of
reaction, and a chemoselectivity of 95% for the oxo‐
phenyl acetamide [or amide (b)] product.
(m, 4H, Ph), 7.65 (td, J = 7.7, 1.7 Hz, 1H, Py), 7.57–7.39
(m, 6H, Ph), 7.27 (d, J = 8.1 Hz, 1H, Py), 7.20 (dd,
J = 7.1, 5.2 Hz, 1H, Py), 4.44–4.22 (m, 2H, CH2), 2.06
(s, 1H, NH).31P‐NMR (101 MHz, CDCl3): 23.9 (s, 1P). IR
(KBr, λ cm−1): 3437, 1586 (NH); 3049, 744 (CH); 2915,
1433 (CH2); 1072 (C‐N); 859 (P‐N). Crystallographic data
for C18H17N2OP (M = 38.54 g mol−1): monoclinic, space
group P21/c (no.14), a = 11.304(2) Å, b = 14.843(3) Å,
c = 10.553(2) Å,
β = 116.385(10)°,
V = 1586.3(6) Å3,
Z = 32, T = N/A K, μ (Mo Kα) = 0.176 mm−1, Dcalc
=
1.2909 g cm−3, 16 952 reflections measured (4.02° ≤ 2Θ
52°), 3113 unique (Rint = 0.1333, Rsigma = 0.1161), which
were used in all calculations. The final R1 was 0.1703 [I ≥
2u(I)] and wR2 was 0.4943 (all data). Elemental analysis
for C17H15N2P calcd (found): C: 73.37 (72.99); H: 5.43
(5.44); N: 10.07 (10.52).
6 | EXPERIMENTAL
6.2 | Synthesis of L2 and L3
All synthesis and procedures described in this work were
carried out in an N2 atmosphere using Schlenk tech-
niques. Organic solvents (analysis grade) and substrates
(synthesis grade) were supplied from Merck or Sigma‐
Aldrich, and dried before using if required. The NMR
data were obtained using a Bruker 300 MHz spectrome-
ter, and all measures were carried out at 298 K. Elemental
analysis for the ligands and palladium complexes was
conducted using a Thermo Scientific Flash 2000 Organic
Elemental Analyzer coupled with an Agilent Technolo-
gies 6890 gas chromatograph. The X‐ray diffraction
studies were carried out using a Bruker‐AXS Smart
Apex II area‐detector diffractometer, and the structures
were resolved using direct methods and refined using
the SHELXL software package. The GC analysis was
performed on a Hewlett‐Packard 5890 series II chromato-
graph equipped with a flame ionization detector (FID)
and a Supelco Equity‐1 column.
Ligands L2 and L3 were synthesized by procedures
described in the literature[10–12] using 2‐picolineamide as
the substrate for L2 and pyrazine carboxamide for L3.
L2 (white solid); yield: 47%. 1H‐NMR (300 MHz,
CDCl3): δ 8.66 (d, J = 8.7 Hz, 1H, OH), 8.55 (d, J = 8.5
Hz, 1H, Py), 8.26 (d, J = 8.2 Hz, 1H, Py), 7.89–7.83 (m,
1H, Py), 7.54–7.37 (m, 10H, 2 Ph), 7.11 (s, 1H, NH).
31P‐NMR (101 MHz, CDCl3): δ 23.69 (s, 1P). IR (KBr, λ
cm−1): 3300, 1452 (N‐H); 3059, 698 (C‐H); 1692 (C=O);
1412 (C‐N); 817 (P‐N). Elemental analysis for
C18H15N2OP calcd (found): C: 70.58 (70.80); H: 4.94
(5.13); N: 9.15 (9.18).
L3 (white yellow solid); yield: 62%. 1H‐NMR (300
MHz, CDCl3): δ 9.46 (d, J = 9.5 Hz, 1H, Pyz), 8.78 (d, J
= 8.8 Hz, 1H, Pyz), 8.53 (m, 1H, Pyz), 8.33 (d, J = 8.3
Hz, 1H, OH), 7.53–7.38 (m, 10H, 2 Ph), 5.78 (s, 1H,
NH). 31P‐NMR (101 MHz, CDCl3): δ 22.95 (s, 1P). IR
(KBr, λ cm−1): 3238, 1452 (N‐H); 3054, 698 (C‐H); 1667
(C=O); 1131 (C‐N); 810 (P‐N). Elemental analysis for
C17H14N3OP calcd (found): C: 66.45 (65.71); H: 4.59
(4.44); N: 13.67 (13.62).
6.1 | Synthesis of L1
A mixture of 2‐picolineamine (1.5 g, 14 mmol) and Et3N
(1 eq.) in dry tetrahydrofuran (THF; 10 mL) was cooled
down to 0°C. Then, a solution of PPh2Cl (2.5 mL, 14
mmol) in THF (5 mL) was added drop‐wise, and the
resulting mixture was stirred overnight at room tempera-
ture. The solution was then filtered, and the solvent was
removed under vacuum to yield a yellow oil. The ligand
was precipitated using a CHCl3/hexane mixture, yielding
a white powder. Single crystals from the oxide of L1 were
obtained from the hexane phase, which were resolved
using X‐ray diffraction. Yield: 40% (white solid). 1H‐NMR
(300 MHz, CDCl3): 8.55 (d, J = 4.6 Hz, 1H, Py), 8.02–7.88
6.3 | Synthesis of L4–L6
Quinoline amine precursor (1 g, 7 mmol, L4: quinoline‐2‐
amine; L5: 8‐aminoquinoline; L6: 1‐aminoisoquinoline) in
THF (10 mL) was cooled down to −78°C, and then a solu-
tion of PPh2Cl (3.5 mmol) in THF (5 mL) was added
drop‐wise. The mixture was allowed to warm up to room
temperature and stirred overnight. The solution was then
filtered. The solvent evaporated under vacuum, and the
product was precipitated from a mixture of CH2Cl2/
diethyl ether, yielding a white powder for L4 and L6,

8 of 9
ARANDA ET AL.
and an orange one for L5. Aminoquinoline hydrochloride
was obtained as a byproduct, which can be recovered
using a NaHCO3/H2O solution.
7.04–7.00 (dd, J = 7.0–7.0 Hz, 1H, Py), 6.57 (d, J = 6.6 Hz,
1H, Py), 5.76 (s, 1H, NH), 4.49 (t, JH‐H = 4.5 Hz, 2H,
CH2). 31P‐NMR (101 MHz, DMSO‐d6): δ 31.95 (s, 1P). IR
(KBr, λ cm−1): 3436, 1438 (N‐H); 3078, 692 (C‐H); 965,
730 (P‐N). Elemental analysis for C19H19Cl2N2PPd calcd
(found): C: 46.03 (45.03); H: 3.65 (3.80); N: 5.96 (4.95).
[Pd(L2)Cl2] (yellow green solid); yield: 37%. 1H‐NMR
(300 MHz, DMSO‐d6): δ 8.85 (d, J = 8.8 Hz, 1H, NH), 8.64
(d, J = 8.63 Hz, 1H, Py), 8.14 (s, 1H, Py), 8.00 (s, 1H, Py),
8.04 (dt, J = 8.0–8.0 Hz, 1H, Py), 7.87–7.39 (m, 10H, 2 Ph).
31P‐NMR (101 MHz, DMSO‐d6): δ 78.84 (s, 1P). IR (KBr, λ
cm−1): 3232, 1446 (N‐H); 3056, 746 (C‐H); 1695 (C=O);
1392 (C‐N); 1101 (P‐N). Elemental analysis for
C18H15Cl2N2OPPd calcd (found): C: 44.70 (45.01); H:
3.13 (2.90); N: 5.79 (5.15).
L4 (white solid); yield: 79%. 1H‐NMR (250 MHz,
CDCl3): δ 8.01 (d, J = 9.1 Hz, 1H, Qn), 7.97–7.88 (m,
1H, Qn), 7.83 (d, J = 9.5 Hz, 1H, Qn), 7.79–7.68 (m, 1H,
Qn), 7.70–7.62 (m, 1H, Qn), 7.62 (d, J = 7.2 Hz, 1H,
Qn), 7.45–7.29 (m, 10H, 2 Ph), 6.27 (s, 1H, NH). 31P‐NMR
(101 MHz, CDCl3): δ 23.21 (s). Elemental analysis for
C21H17N2P calcd (found): C: 76.36 (74.93); H: 5.22
(5.20); N: 8.53 (8.45).
L5 (orange solid); yield: 31%. 1H‐NMR (300 MHz,
CDCl3): δ 8.67 (dd, J = 4.2–1.6 Hz, 1H, Qn), 7.97 (dd, J
= 8.3–1.6 Hz, 1H, Qn), 7.60 (m, J = 17.2, 16.0, 10.4, 4.4
Hz, 1H, Qn), 7.48–7.32 (m, 1H, Qn), 7.34–7.13 (m, 10H,
2 Ph), 7.06 (d, J = 8.1 Hz, 1H, Qn), 6.84 (d, J = 8.6 Hz,
1H, Qn), 4.73 (s, 1H, NH). 31P‐NMR (101 MHz, CDCl3):
δ 22.67 (s). IR (KBr, λ cm−1): 3306, 1481 (N‐H); 1123,
721 (P‐N). Elemental analysis for C21H17N2P calcd
(found): C: 76.82 (74.93); H: 5.22 (5.15); N: 8.53 (8.65).
L6 (white yellow solid); yield: 41%. 1H‐NMR (300
MHz, CDCl3): δ 7.87 (dd, J = 15.1–7.1 Hz, 3H, Qn),
7.74–7.55 (m, 10H, 2 Ph), 7.46 (t, J = 7 Hz, 1H, Qn),
7.38 (dd, J = 4.3, 2.3 Hz, 1H, Qn), 7.27 (s, 1H, NH), 7.00
(d). 31P‐NMR (101 MHz, CDCl3): δ 22.88 (s). IR (KBr, λ
cm‐ 1): 3485, 1504 (N‐H); 793, 701 (P‐N). Elemental
analysis for C21H17N2P calcd (found): C: 76.82 (75.93);
H: 5.22 (5.20); N: 8.53 (8.25).
1
[Pd(L3)Cl2] (yellow solid); yield: 81%. H‐NMR (300
MHz, DMSO‐d6): δ 10.55 (s, 1H, OH); 9.19–8.62 (m, 2H,
Pyz); 8.27 (s, 1H, Pyz); 8.05–7.40 (m, 10H, 2 Ph), 6.66 (s,
1H, NH). 31P‐NMR (101 MHz, DMSO‐d6): δ 82.29 (s,
1P). IR (KBr, λ cm−1): 3435, 1436 (N‐H); 3094, 689
(C‐H); 1688 (C=O); 1381 (C‐N); 1107 (P‐N). Elemental
analysis for C17H14Cl2N3OPPd calcd (found): C: 42.13
(41.95); H: 2.91 (2.85); N: 8.67 (9.28).
[Pd(L4)Cl2] (white yellow solid); yield: 37%. 1H‐NMR
(300 MHz, DMF‐d7): δ 10.27 (dd, J = 8.5, 4.2 Hz, 1H, Qn),
10.07 (d, J = 8.5 Hz, 1H, Qn), 8.34 (s, 2H, Qn), 8.30 (d, J
= 2.9 Hz, 1H, Qn), 8.27 (s, 1H, NH), 8.23 (d, J = 6.0 Hz,
3H, Ph), 8.18–8.10 (m, 2H, Ph), 8.04 (d, J = 1.4 Hz, 1H,
Ph), 8.03–8.01 (m, 1H, Ph), 7.99 (d, J = 1.5 Hz, 1H, Qn),
7.97 (d, J = 2.8 Hz, 1H, Ph), 7.92 (dd, J = 11.4–4.3 Hz,
2H, Ph), 7.82 (dd, J = 8.0–1.1 Hz, 1H, Ph), 7.60 (dd,
J = 14.9–7.5 Hz, 3H, Ph), 7.51–7.45 (m, 1H, Ph), 7.35 (d,
J = 9.0 Hz, 1H, Qn), 7.28 (d, J = 8.9 Hz, 1H, Ph or Qn),
7.14 (d, J = 8.9 Hz, 1H, Ph or Qn). 31P‐NMR (101 MHz,
CDCl3): δ 78.38 (s). IR (KBr, λ cm−1): 3442, 1510 (N‐H);
834, 773 (P‐N). Elemental analysis for C21H17Cl2N3OPPd
calcd (found): C: 49.88 (48.53); H: 3.39 (3.70); N: 5.54 (6.01).
[Pd(L5)Cl2] (red solid); yield: 40%. 1H‐NMR (300
MHz, DMF‐d7): δ 9.63 (s, 1H, NH), 9.46 (dd, J = 5.2–1.3
Hz, 1H, Qn), 9.03 (dd, J = 8.4–1.3 Hz, 1H, Qn), 8.31 (d,
J = 8.0 Hz, 1H, Qn), 8.21 (s, 3H, Ph), 8.18–8.10 (m, 3H,
Ph), 8.10–7,97 (m, 2H, Ph), 6.01 (s, 1H, Qn). 31P‐NMR
(121 MHz, DMF‐d7): δ 79.64 (s). Elemental analysis for
C21H17Cl2N2PPd calcd (found): C: 49.88 (48.56); H: 3.39
(3.77); N: 5.54 (5.48).
6.4 | Synthesis of L7
Ligand L7 was synthesized by procedures described in the
literature,[16] yielding a white powder. Yield: 47%.
1H‐NMR (300 MHz, CDCl3): δ 8.95–8.90 (m, 1H, Qn),
8.78 (d, J = 4.2 Hz, 1H, QN), 8.17 (d, J = 1.5 Hz, 1H,
Qn), 8.14 (d, J = 1.6 Hz, 1H, Qn), 8.11 (d, J = 1.7 Hz,
1H, Qn), 7.63–7.53 (m, 1H), 7.54–7.31 (m, 10H, Ph).
31P‐NMR (121 MHz, CDCl3): δ 116.89 (s). Elemental
analysis for C21H16NOP calcd (found): C: 76.59 (77.03);
H: 4.90 (4.80); N: 4.25 (4.45).
6.5 | Synthesis of [Pd(L)Cl2] complexes
(L = L1–L7)
1
Pd (II) complexes containing P^N ligands were synthe-
sized by procedures described in the literature,[10–12]
using PdCl2 (500 mg, 2.8 mmol) as the precursor. Single
crystals for X‐ray diffraction studies were obtained from
[Pd(L7)Cl2].
[Pd(L6)Cl2] (yellow solid); yield: 35%. H‐NMR (300
MHz, DMF‐d7): δ 8.9 (s, 1H, NH), 8.69 (d, J = 8.2 Hz,
2H, Qn), 8.61 (t, J = 5.6 Hz, 2H, Qn), 8.53 (s, 2H, Qn),
8.31 (d, J = 6.7 Hz, 1H, Qn), 8.20 (d, J = 10.8 Hz, 3H,
Qn), 8.11–7.86 (m, 4H, Ph), 7.80 (dd, J = 14.1, 7.2 Hz,
2H, Ph), 7.71 (dd, J = 11.7, 4.9 Hz, 1H, Ph), 7.24 (d,
J = 6.8 Hz, 1H, Qn), 7.17 (dd, J = 15.1, 6.9 Hz, 1H, Qn).
31P‐NMR (121 MHz, DMF‐d7): δ 78.92 (s). IR (KBr, λ
1
[Pd(L1)Cl2] (yellow solid); yield: 74%. H‐NMR (300
MHz, DMSO‐d6): δ 7.96 (d, J = 8 Hz, 1H, Py), 7.90–7.59
(m, 10H, 2 Ph), 7.42–7.36 (dt, J = 7,4, 7.4 Hz, 1H, Py),

ARANDA ET AL.
9 of 9
cm−1): 3340, 1440 (N‐H); 952, 747 (P‐N). Elemental anal-
ysis for C21H17Cl2N2PPd calcd (found): C: 49.88 (48.03);
H: 3.39 (3.50); N: 5.54 (5.18).
P. Oxley, S. C. Passey, T. C. Walsgrove, A. S. Wells, Org. Process
Res. Dev. 2003, 7, 663.
[5] I. Ojima, C. Commandeur, W. H. Chiou, Comprehensive Organ-
ometallic Chemistry III, 3rd ed., Elsevier Science, Oxford 2007.
1
[Pd(L7)Cl2] (yellow solid); yield: 55%. H‐NMR (300
[6] M. McGuire, E. Sorenson, D. N. Klein, N. H. Baine, Synth.
Commun. 1998, 28, 1611.
MHz, CDCl3): δ 10.56 (dd, J = 5.4–1.4 Hz, 1H, Qn), 8.43
(dd, J = 8.2–1.4 Hz, 1H, Qn), 8.01–7.89 (m, 4H, Qn),
7.64–7.38 (m, 10H, 2 Ph). 31P‐NMR (101 MHz, CDCl3): δ
114.5 (s). Crystallographic data for C21H16NOPPdCl2
(M = 506.66 g mol−1): monoclinic, space group P21/n
(no. 14), a = 10.565(5) Å, b = 11.311(5) Å, c = 17.038(7) Å,
β = 99.28(2)°, V = 2009.2(16) Å3, Z = 4, T = 296.15 K, μ
[7] E. Takács, C. Csilla‐Varga, R. Skoda‐Földes, L. Kollár,
Tetrahedron Lett. 2007, 48, 2453.
[8] E. Szánti‐Pintér, Z. Csók, Z. Berente, L. Kollár, R. Skoda‐Földes,
Steroids 2013, 78, 1177.
[9] E. Szánti‐Pintér, Z. Csók, L. Kollár, K. Vékey, R. Skoda‐Földes,
J. Organomet. Chem. 2012, 718, 105.
,
(Mo Kα) = 1.280 mm−1 Dcalc = 1.6748 g cm−3, 21 645
[10] P. Aguirre, C. Lagos, S. A. Moya, C. Zuniga, C. Vera‐Oyarce, E.
Sola, G. Peris, J. C. Bayón, Dalton Trans. 2007, 46, 5419.
reflections measured (4.34° ≤ 2Θ ≤ 51.98°), 3913 unique
(Rint = 0.1343, Rsigma = 0.1086), which were used in all
calculations. The final R1 was 0.0453 [I ≥ 2u(I)], and wR2
was 0.0940 (all data).
[11] G. Abarca, K. Brown, S. A. Moya, J. C. Bayón, P. Aguirre, Catal.
Lett. 2005, 145, 1396.
[12] B. Aranda, S. Zolezzi, G. Valdebenito, J. Cáceres‐Vásquez, S. A.
Moya, P. Aguirre, J. Chil. Chem. Soc. 2013, 58, 2136.
6.6 | Catalytic essays
[13] D. Larsen, M. Pittelko, S. Karmakar, E. T. Kool, Org. Lett. 2005,
17, 274.
A mixture of catalyst (0.075 mmol), iodobenzene (7.5
mmol), diethylamine (2.4 mL) and Et3N (1.5 mL) dis-
solved in DMF (10 mL) was introduced in a previously
purged, glass‐lined stainless‐steel, high‐pressure capable
autoclave fitted with temperature and pressure control.
The autoclave was then charged with CO (30 bar), and
the temperature set up to 90°C (t = 0). Samples were
collected every hour and analysed by gas chromatography
(GC). The products obtained in the catalytic reaction
were determined by GC–mass spectrometry (MS) in
University of Chile's CEPEDEQ (Centro de Estudios para
el Desarrollo de la Quimica). Pseudo first‐order kinetic
rate k for every entry was determined by the logarithmic
plot of the initial rate vs. substrate concentration.
[14] M. Doležal, J. Zitko, J. Jampílek, Understanding Tuberculosis –
New Approaches to Fighting Against Drug Resistance, InTech
Rijeka, Croatia 2012.
[15] R. Pattacini, C. Giansante, P. Ceroni, M. Maestri, P. Braunstein,
Chem. Eur. J. 2007, 13, 10 117.
[16] D. Benito‐Garagorri, W. Lackner‐Warton, C. M. Standfest‐
Hauser, K. Mereiter, K. Kirchner, Inorg. Chim. Acta 2012,
363, 3674.
[17] T. Shibata, K. Takagi, J. Am. Chem. Soc. 2000, 122, 9852.
[18] F. C. Rix, M. Brookhart, P. S. White, J. Am. Chem. Soc. 1996,
118, 2436.
[19] M. Papp, R. Skoda‐Földes, J. Mol. Catal. A: Chem. 2013, 378, 193.
[20] X. Wu, H. Neumann, M. Beller, Chem. Asian J. 2010, 5, 2168.
[21] Z. Csók, A. Takátsy, L. Kollár, Tetrahedron 2012, 68, 2657.
[22] G. Cavinato, L. Toniolo, J. Mol. Catal. A: Chem. 1996, 104(3), 221.
ACKNOWLEDGEMENTS
[23] a) I. J. B. Lin, J. C. Liao, C. C. J. Chuang, J. Chin. Chem. Soc.
1991, 38(28), 483. b) P. R. Nitha, M. M. Joseph, G. Gopalan,
K. K. Maiti, K. V. Radhakrishnan, P. Das, Org. Biomol. Chem.
2018, 16, 6430.
The authors of this work thank CONICYT‐Chile for
financial support (FONDECYT projects 1160505, doctoral
grants 21110568 and 21140223). S.A.M. thanks Dicyt
(021642MD) of the Universidad de Santiago de Chile.
[24] J. Zhang, Y. Ma, M. Yangmin, Eur. J. Org. Chem. 2018, 1720.
[25] N. L. Hughes, C. L. Brown, A. A. Irwin, Q. Cao, M. J. Muldoon,
ChemSusChem 2017, 10, 675.
ORCID
Pedro Aguirre https://orcid.org/0000-0001-6169-3793
How to cite this article: Aranda B, Moya SA,
Vega A, Valdebenito G, Ramirez‐Lopez S, Aguirre
P. New palladium (II) complexes containing
phosphine‐nitrogen ligands and their use as
catalysts in aminocarbonylation reaction. Appl
Organometal Chem. 2019;e4709. https://doi.org/
10.1002/aoc.4709
REFERENCES
[1] A. Schoenberg, R. F. Heck, J. Org. Chem. 1974, 39, 3327.
[2] R. F. Heck, J. P. Nolley, J. Org. Chem. 1972, 37, 2320.
[3] R. F. Heck, Org. React. 1982, 27, 345.
[4] R. J. Atkins, A. Banks, R. K. Bellingham, G. F. Breen, J. S.
Carey, S. K. Etridge, J. F. Hayes, N. Hussain, D. O. Morgan,