New N-pyrazole, P-phosphine hybrid ligands and their reactivity towards Pd(II): X-ray crystal structures of complexes with [PdCl2(N,P)] core

Article abstract of DOI:10.1016/j.jorganchem.2015.10.007

Two new N-pyrazole, P-phosphine hybrids ligands: 1-[2-(diphenylphosphanyl)methyl]-3,5-dimethylpyrazole (LP1) and 1-[2-(diphenylphosphanyl)propyl]-3,5-dimethylpyrazole (LP3) are presented. The reaction of these two ligands and two other ligands reported in

Full text of DOI:10.1016/j.jorganchem.2015.10.007

Journal of Organometallic Chemistry 799-800 (2015) 257e264
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
New N-pyrazole, P-phosphine hybrid ligands and their reactivity
towards Pd(II): X-ray crystal structures of complexes with [PdCl2(N,P)]
core
a
a
a
b
b, c
~
ꢀ
Miguel Guerrero , Sergio Munoz , Josep Ros , Teresa Calvet , Merce Font-Bardía
,
,
*
Josefina Pons a
a
ꢀ
Departament de Química, Universitat Autonoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
Cristal·lografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Martí i Franques s/n, 08028, Barcelona, Spain
Unitat de Difraccio de Raig-X, Centres Científics i Tecnologics de la Universitat de Barcelona (CCiTUB), Universitat de Barcelona, Sole i Sabarís, 1-3, 08028,
b
c
ꢀ
ꢀ
ꢁ
ꢀ
ꢁ
Barcelona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new N-pyrazole, P-phosphine hybrids ligands: 1-[2-(diphenylphosphanyl)methyl]-3,5-dimethyl
pyrazole (LP1) and 1-[2-(diphenylphosphanyl)propyl]-3,5-dimethylpyrazole (LP3) are presented. The
reaction of these two ligands and two other ligands reported in the literature: 1-[2-(diphenylphos-
phanyl)ethyl]-3,5-dimethylpyrazole (LP2) and 1-[2-(diphenylphosphanyl)ethyl]-3,5-diphenylpyrazole
(LP4) with [PdCl2(CH3CN)2] yield [PdCl2(LP)] (LP ¼ LP1 (1), LP2 (2), LP3 (3) and LP4 (4)) complexes.
All complexes are fully characterised by analytical and spectroscopic methods and the resolution of the
crystal structure of complexes 2 and 3 by single crystal X-ray diffraction is also presented. In these
Received 21 July 2015
Received in revised form
29 September 2015
Accepted 6 October 2015
Available online xxx
Keywords:
N,P-hybrid ligand
Pyrazole
complexes the ligands are coordinated to Pd(II) via k
2(N,P) forming metallocycles of six (2) and seven (3)
members and finish their coordination with two cis-chlorine atoms. Finally, complex 2 is studied in the
palladium-catalysed CeC coupling reaction, being active even for aryl chlorides substrates.
© 2015 Elsevier B.V. All rights reserved.
Phosphine
Palladium (II)
X-ray crystal structures
Catalysis
1. Introduction
relatively underexplored [6].
During the last years, in our group we have studied hybrid li-
Pyrazole ligands are widely used as core motifs for a large
number of compounds of significant relevancy and they have a
variety of applications (i.e. as catalysis, pharmaceuticals, agro-
chemicals, herbicides, fungicides, among others) [1]. The synthesis
of organic ligands containing nitrogen donor atoms and other
heteroatoms as N, O and/or S has focused the interest of many
research laboratories [2]. In particular, the synthesis of nitrogen
ligands containing in addition phosphines (N,P-hybrid ligands) and
their transition metal complexes has become increasingly attrac-
tive in the last years owing to their intrinsic properties, and
considerable structural diversity [3]. These complexes are majority
focused in the cases where the nitrogen atoms are pyridine [4] or
oxazoline groups [5]. Nevertheless, the chemistry of metal com-
plexes with bidentate ligands pyrazole-phosphine has been
gands that combine pyrazole and amino-, alcohol-, ether-, thio-
ether-, phosphinite- or phosphine-groups. These hybrid ligands
have been studied for their potential hemilabile properties, their
applications in catalysis and for the construction of discrete mo-
lecular architectures with diversified topologies [7]. It is well
known that the coordination/chelation properties of these ligands,
and, in consequence, their reactivity and catalytic behaviour, in a
complex depend on both (i) kind of heteroatoms (i.e. S, O, N, etc.)
and (ii) their relative position in the skeleton of the ligands. Thus, in
order to expand the scope of our N-pyrazole, P-phospine system,
we have modulated the length of the link between these
heteroatoms.
Now, we present herein two new phosphine-ligands 1-[2-
(diphenylphosphanyl)methyl]-3,5-dimethylpyrazole (LP1) and 1-
[2-(diphenylphosphanyl)propyl]-3,5-dimethylpyrazole (LP3). With
these ligands and two ligands previously described in the literature
1-[2-(diphenylphosphanyl)ethyl]-3,5-dimethylpyrazole (LP2) [6e]
* Corresponding author.
http://dx.doi.org/10.1016/j.jorganchem.2015.10.007
0022-328X/© 2015 Elsevier B.V. All rights reserved.

258
M. Guerrero et al. / Journal of Organometallic Chemistry 799-800 (2015) 257e264
and 1-[2-(diphenylphosphanyl)ethyl]-3,5-diphenylpyrazole (LP4)
[6f], we have studied their reactivity with [PdCl2(CH3CN)2]. The
synthesis and characterization of these new ligands and their
complexes have been investigated. In particular, NMR experiments
and X-ray crystal studies. Finally, complex 2 has been studied as a
catalyst in the Heck reaction between phenyl halides and tert-butyl
acrylate.
[PdCl(LP)]þ (m/z values, 437 (100%), 451 (100%) and 575 (100%),
respectively. ESI(þ) of
3 shows two peaks attributable to
[PdCl(LP)]þ and [PdCl2(LP) þNa]þ (m/z values, 465 (100%) and 523
(30%), respectively).
Conductivity measurements of 10ꢁ3 M samples in acetonitrile
(between 2 and 8 U
ꢁ1cm2molꢁ1), show the non-ionic behaviour of
complexes 1e4 (compared with tabulated values) [11].
The IR spectra in the range 4000e400 cmꢁ1 of 1e4 compounds
do not show important differences respect free ligands, although
the most characteristic bands are attributable to the pyrazolyl and
2. Results and discussion
pyridyl groups
n
d
(C]C)ar and
n(C]N)ar between 1555 and
2.1. Synthesis of the ligands
1552 cmꢁ1 and
(CeH)oop between 765 and 690 cmꢁ1 [12]. The
n
(CeP) bands between 798 and 793 cmꢁ1 are characteristic in all Pd
Ligand 1-[2-(diphenylphosphanyl)ethyl]-3,5-dimethylpyrazole
(LP2) was previously prepared in our group by reaction of 1-
(chloroethyl)-3,5-dimethylpyrazole with PPh2Li in THF at 25 ꢀC
[6e]. The ligand 1-[2-(diphenylphosphanyl)ethyl]-3,5-diphenylp
yrazole (LP4) was synthesized according to a procedure previ-
ously described by Messerle et al. [6f].
complexes [12]. On IR spectra in the region 600e100 cmꢁ1, the
n
(Pd-N) bands are observed (463e452 cmꢁ1) and the
n(Pd-P) be-
tween (332e309 cmꢁ1). Moreover, the spectra of these complexes
display two bands (360e347 cmꢁ1) and (345e328 cmꢁ1), corre-
sponding to stretching n(Pd-Cl), which are typical of compounds
with a cis disposition of chlorine ligands around the Pd(II) [13].
The 1H, 13C{1H}, 31P{1H}, HMQC, COSY and NOESY NMR spectra
were recorded in CDCl3 for 1 and 3, CD2Cl2 for 2 and CD3CN for 4,
due to its low solubility in other deuterated solvents (see
Supplementary information). The 13C{1H} NMR spectrum of com-
pound 4, could not be recorded for this complex owing to its low
solubility in common solvents. The NMR spectra of 1e4 compounds
do not show important differences between free ligands and the
complexes in the aromatic and in the methyl region. However, NMR
spectra were studied in detail to make the assignment of the N-
(CH2)x-P signals. The 1H, 13C{1H} and 31P{1H} NMR spectra were
consistent with the proposed formulation and showed the coor-
dination of the ligands (LP1, LP2, LP3 and LP4) to the Pd atom. NMR
spectroscopic data are reported in Section 4. The 1H NMR spectra of
complexes 1e4, present one signal between 6.73 and 5.75 ppm,
assigned to the protons of the CH(pz). In the 1H NMR spectrum of 1,
the methylene hydrogens appear as one signal, the two protons of
the CH2 group in Npz-CH2-P chain are equivalent. Thus, the signal
can be assigned as a doublet (4.70 ppm, 2JPH ¼ 8.1 Hz). For 2 and 4,
the four protons of the CH2 groups in Npz-CH2-CH2-P chain, appear
as two multiplets. The multiplets that correspond to Npz-CH2
appear at 4.81 (2) and 5.03 (4) ppm, and multiplets of the protons
CH2-P appear at 2.61 (2) and 2.60 (4) ppm. Finally, for compound 3
the 1H NMR spectrum display four signals as multiplets that cor-
responds to groups of the signals for Npz-CH2(a)-CH2(b)-CH2(c)-P
chain. HMQC spectrum was used to assign the signals of the protons
(a), (b) and (c) of the chain. Two of these multiplets appear at 5.69
The new ligands 1-[2-(diphenylphosphanyl)methyl]-3,5-dimeth
ylpyrazole (LP1) and 1-[2-(diphenylphosphanyl)propyl]-3,5-dimet
hylpyrazole (LP3) were prepared by reaction of 1-(chloromethyl)-
3,5-dimethylpyrazole (LCl1) [8] or 1-(chloropropyl)-3,5-dimeth
ylpyrazole (LCl3) [9], respectively, in presence of PPh2Li, which is
generated in situ by deprotonation of PPh2H by n-butyl lithium (n-
BuLi) in THF as solvent, at 0 ꢀC (Scheme 1a).
These new ligands, isolated in a 99% (LP1) and 95% yields (LP3)
as yellowish oils, were characterised by C, H, and N elemental an-
alyses, IR, 1H, 13C{1H} and 31P{1H} NMR spectroscopy, and by
MS(ESIþ) mass spectrometry. All of them are in agreement with
proposed ligands. In the 31P{1H} NMR spectra, the diphenylphos-
phanyl moiety gives a singlet at
ppm (LP3), indicating the presence of the phosphine group
d
¼ ꢁ18.4 ppm (LP1) and ¼ ꢁ19.1
d
[6e,10,12].
2.2. Synthesis and characterization of the complexes
LP1-LP4 ligands (Scheme 1b) react with one equivalent of
[PdCl2(CH3CN)2] in dry CH2Cl2 as solvent, to give the complexes
[PdCl2(LP)] (LP ¼ LP1 (1) (11% yield), LP2 (2) (86% yield), LP3 (3)
(40% yield) and LP4 (4) (56% yield)) (Scheme 1b). The complexes
were analytically and spectroscopically (IR, 1H, 13C{1H}, and 31P{1H}
NMR) characterised.
Elemental analyses of the four complexes are consistent with
their formulation.
MALDI-TOF of 1, 2, and 4 show one peak attributable to
Scheme 1.

M. Guerrero et al. / Journal of Organometallic Chemistry 799-800 (2015) 257e264
259
and 4.25 ppm corresponding to each one of the protons of the
fragment Npz-CH2(a). This behaviour indicates that the two protons
are diastereotopic. The other group of signals at 1.89 and 1.21 ppm,
are attributable to CH2(b) and CH2-P(c), respectively. The presence
of the multiplets for compounds 1e4 is probably due to the dia-
stereotopic properties of CH2 groups. This effect is attributable to
the rigid conformation of the ligands once they are complexed. The
13C{1H} NMR spectra of 1e3 complexes, show one signal between
109.9 and 107.6 ppm, assigned to the CH(pz). The signals in the 31
P
{1H} NMR spectra for all complexes appear at lower fields than for
the free respectively ligands and permit to know that phosphorus
atom is connected to metallic centre. The spectra show a singlet at
(þ35.3 ppm (1), þ23.9 ppm (2), þ11.6 ppm (3), and þ21.0 ppm (4)).
Chemical shifts agree with of values of other complexes of Pd(II), P-
phosphine complexes described in the literature [6g,6h].
2.3. Crystal and molecular structure of complexes 2 and 3
We were able to obtain X-ray single crystals of complexes 2 and
3, and we performed a crystal structure determination for both
complexes.
ORTEP pictures and selected bond distances and angles are
shown in Fig. 1 (2), Fig. 2 (3) and Table 1. The structures of com-
plexes 2 and 3 consists of discrete Pd(II) molecules. The metal is
Fig. 2. ORTEP drawing of [PdCl2(LP3)] (3), showing all non-hydrogen atoms and the
atom numbering scheme; 50% probability amplitude displacement ellipsoids are
shown.
connected to the pyrazole-phosphine ligands via k
2(N,P) building a
metallocycle ring of six (2) and seven (3) members, and finishes its
coordination with two chlorine atoms in a cis-disposition. A slightly
distorted square-planar geometry is observed around Pd(II) atom in
both structures. The distortion of the geometry is observed by the
values of distances between Pd(II) and the main plane N1-P-Cl1-Cl2
[0.005 Å (2), 0.001 Å (3)], the values of the N1-Pd-P bite angles
[82.77(8)º (2), 89.07(6)º (3)]. All of them are in agreement with the
ones found in the literature [14].
The bond distances Pd-N [2.046(3) Å (2), 2.0377(18) Å (3)], Pd-P
[2.2325(11) Å (2), 2.2155(7) Å (3)], Pd-Cl1 [2.3885(12) Å (2),
2.3365(7) Å (3)] and Pd-Cl2 [2.2752(15) Å (2), 2.2747(7) Å (3)], are
in agreement with the values described in the literature: Pd-N
[1.953e2.088 Å], Pd-P [2.201e2.285 Å], Pd-Cl1 [2.282e2.472 Å]
and Pd-Cl2 [2.222e2.294 Å] [14].
Due to the different trans effect of the donor atoms in 2 and 3,
the Pd-Cl1 bonds trans to phosphorus, are longer than the Pd-Cl2
bonds trans to nitrogen [14]. The N1-Pd-P bite angles for 2 and 3
are smaller than 90 ꢀC, but are consistent with the reported angles
for similar complexes [14]. It is worth noting that in both structures
the six (2) and seven-membered rings (3) formed by the bidentate
ligands coordinated to palladium adopt
conformation.
a
twisted boat
To deeply understand the structure for framework we have
Fig. 1. ORTEP drawing of [PdCl2(LP2)] (2), showing all non-hydrogen atoms and the atom numbering scheme; 50% probability amplitude displacement ellipsoids are shown.

260
M. Guerrero et al. / Journal of Organometallic Chemistry 799-800 (2015) 257e264
Table 1
makes it possible to perform the reactions even at temperature
above 140 ꢀC (close to the boiling point of the solvent) under the
reaction conditions. In these reactions were used Et3N as base, DMF
(Dimethylformamide) as solvent and NBu4Br (TBAB) as additive.
The use of complex 2 for the Heck olefination of aryl halides
gives rise exclusively to the formation of trans-acrylic acid esters
(1H NMR). This complex was sensitive to oxygen or moisture:
change in their efficiency was observed if the Heck coupling re-
actions were carried out under aerobic conditions. During these
reactions in the presence of oxygen/moisture a black solid appears
from the reaction mixture. This solid was identified as Pd(0)
through the mercury poisoning test [16].
Selected bond lengths (Å) and angles (º) of 2 and 3.
2
3
PdeN(1)
PdeP
PdeCl(2)
PdeCl(1)
N(1)ePdeP
PePdeCl(2)
N(1)ePdeCl(1)
PePdeCl(1)
Cl(2)ePdeCl(1)
2.046(3)
2.2325(11)
2.2752(15)
2.3885(12)
82.77(8)
91.80(4)
93.27(8)
175.22(4)
92.26(4)
2.0377(18)
2.2155(7)
2.2747(7)
2.3365(7)
89.07(6)
90.43(3)
89.51(6)
178.39(2)
90.99(3)
Catalytic study of complex 2, between phenyl iodide and tert-
butyl acrylate, a yield of 100% (0.1 cat.) and 66% (0.01 cat.) were
obtained, in 0.16 h and 3.6 h, respectively, with a turnover number
(TON) of 987 and 6385, respectively (Table 2: entries 1 and 2).
Similar palladium complexes synthesised in our group yield similar
catalytic behaviour [7h].
For several years, aryl bromides and iodides were preferably
used as substrates in such reactions, because aryl chlorides are
transformed very sluggishly by standard palladium catalysts, due to
the strength of the CeCl bond. There has been a growing interest in
finding catalytic systems that can successfully catalyse cross-
coupling reactions with aryl chlorides, since they are widely
available, industrially important, and generally less expensive than
their bromide and iodide counterparts. In order to studied the in-
fluence of the phenyl halide in our system, we have also studied the
catalytic reaction with phenyl chloride as a substrate, yielding 29%
(0.1 cat.) and 37% (0.01 cat) in 32 h and 46 h, respectively, with a
values of TON of 307 and 3601, respectively (Table 2: entries 3 and
4).
explored the connection modes of the metal centers and organic
ligands. Thus, we have investigated the self-assembly pattern of
[PdCl2(LP2)] (2) and [PdCl2(LP3)] (3) complexes in the crystal
through intermolecular CeH$$$Cl hydrogen bonding interactions.
In complex 2 (Fig. 3), three of the potentially active H atoms (H13
from phenyl group, H7B and H6A from ethylene chain) are engaged
in hydrogen bonds with Cl atoms, which act as the unique receptor
for all three intermolecular interactions (C6-H6A$$$Cl2: 3.623 Å,
151.39ꢀ; C7-H7B$$$Cl1: 3.790 Å, 146.95ꢀ; C13-H13$$$Cl1: 3.842 Å,
176.58ꢀ). In complex 3 (Fig. 4), each [PdCl2(LP3)] unit is linked to
three neighbouring molecules, via also C-H$$$Cl hydrogen bonding
(C5-H5C$$$Cl1: 3.627 Å, 141.45ꢀ; C6-H6B$$$Cl2: 3.639 Å, 128.01ꢀ;
C8-H8A$$$Cl2: 3.547 Å, 149.18ꢀ). All these C-H$$$Cl intermolecular
contacts can be considered as “weak” on the basis of the contact
distances and angles [15].
2.4. Heck reactions using [PdCl2(LP2)] (2) complex
In all cases studied the M:L ratio was 1:1. Finally, we have
changed this ratio to M:L 1:10. In this case the results were lower,
t ¼ 33 h, % conv. ¼ 2, and TON ¼ 269 (Table 2, entry 5).
The Heck reaction is one of the most widely used palladium
catalysed reactions in organic synthesis. The reaction consists in the
vinylation of aryl halides, and it was first reported by Mizoroki and
Heck in the early 1970s. In the following decades, the chemical
community has searched for active and stable palladium catalysts,
which should be versatile and efficient.
3. Conclusion
We have presented the synthesis and characterisation of two
new ligands (LP1 and LP3), and with these ligands and two other
ligands, previously described in the literature (LP2 and LP4), we
have assayed the reaction with [PdCl2(CH3CN)2], obtaining
[PdCl2(LP)] (LP ¼ LP1 (1), LP2 (2), LP3 (3) and LP4 (4)) compounds.
All these new complexes have been characterised by elemental
analyses, conductivity measurements, infrared and 1H, 13C{1H} and
31P{1H} NMR spectroscopies, and MS-ESI(þ) and MALDI-TOF
spectrometry.
Complex [PdCl2(LP2)] (2) has been used as pre-catalyst in the
Heck reaction between phenyl halides (I, Cl) and tert-butyl acrylate.
The reaction progress was analysed by gaseliquid chromatography
(GLC). The results obtained are summarized in Table 2.
A characteristic of this complex is the thermal stability, which
The crystal structure of complexes [PdCl2(LP)] (LP ¼ LP2 (2) and
LP3 (3)) were determined by X-ray diffraction methods showing a
square planar geometry where the palladium centre is coordinated
to one bidentate LP ligand and two chlorine atoms in a cis
disposition.
Complex 2 represents an active catalyst in the Heck reaction
between phenyl halides and tert-butyl acrylate. The advantages of
this practical and efficient catalyst system include its generality and
high catalytic activity even for some aryl chlorides under mild
conditions.
4. Experimental Section
4.1. General details
Reactions were carried out under a dinitrogen atmosphere using
vacuum line and Schlenk techniques. Solvents were dried and
distilled according to standard procedures and stored under ni-
trogen. All chemicals products were used as received from
Fig. 3. Supramolecular view of two [PdCl2(LP2)] (2) units generated by intermolecular
CeH$$$Cl hydrogen bondings. CeH$$$Cl hydrogen bonding interactions are indicated
with dashed lines.

M. Guerrero et al. / Journal of Organometallic Chemistry 799-800 (2015) 257e264
261
Fig. 4. Supramolecular view of four [PdCl2(LP3)] (3) units generated by intermolecular CeH$$$Cl hydrogen bondings. CeH$$$Cl hydrogen bonding interactions are indicated with
dashed lines.
Table 2
Heck coupling reaction of Aryl Halides using Pre-Catalysts 2.
Entry
Ar-X
Cat.
mol%
M:L
Solvent
T (ºC)
t (h)
0.16
3.6
32
46
33
Yield(%)
TON
TOF(h-1)
1
2
3
4
5
I
I
Cl
Cl
Cl
2
2
2
2
2
0.1
0.01
0.1
0.01
0.1
1:1
1:1
1:1
1:1
1:10
DMF
DMF
DMF
DMF
DMF
140
140
140
140
140
100
66
29
37
26
987
6385
307
3601
269
6288
1789
8
77
8
commercial suppliers, unless otherwise indicated.
Packard HP-5 column (30 m long, 0.32 mm internal diameter and
0.25 mm film thickness). The stationary phase consists of 5%
diphenyl/95% dimethyl polysiloxane. Thermal stability of complex
2 was evaluated with a blank catalytic experiment (without re-
agents) at 140 ꢀC, close to the boiling point of the solvent, under the
reaction conditions. In these reactions were used Et3N as base, DMF
(Dimethylformamide) as solvent and NBu4Br (TBAB) as additive.
The compound [PdCl2(CH3CN)2] was prepared according to
literature methods [17], 1-[2-(diphenylphosphanyl)ethyl]-3,5-
dimethylpyrazole (LP2) [6e] and 1-[2-(diphenylphosphanyl)
ethyl]-3,5-diphenylpyrazole (LP4) [8] ligands were synthesized as
we previously reported.
Elemental Analyses (C, H, N) were performed at Chemical An-
ꢀ
alyses Service of the Universitat Autonoma de Barcelona, using a
Carlo Erba CHNS EA-1108 instrument separated by chromato-
graphic column and thermoconductivity detector. Conductivity
measurements were performed at room temperature in 10ꢁ3
M
acetonitrile solutions employing a CyberScan CON 500 (Eutech
instrument) conductimeter. Infrared spectra were run in a Perkin
Elmer FT-2000 spectrophotometer as KBr pellets or polyethylene
films. The 1H, 13C{1H} and 31P{1H} NMR spectra and bidimensional
NMR spectra were run on a NMR-FT Brucker AC-250 spectrometer.
All NMR experiments were recorded on CDCl3, CD2Cl2 or CD3CN
solvents under nitrogen. 1H and 13C{1H} NMR chemicals shifts (
were determinate relative to internal TMS and are given in ppm. 31
{1H} NMR chemical shifts (
d)
P
4.2. Synthesis of the ligands
d) were determined relative to external
85% H3PO4. Electrospray Mass spectra (ESI þ) were carried out by
4.2.1. Synthesis of 1-[2-(diphenylphosphanyl)methyl]-3,5-
dimethylpyrazole (LP1) and 1-[2-(diphenylphosphanyl)propyl]-3,5-
dimethylpyrazole (LP3)
the staff of the Chemical Analysis Service of the Universitat
ꢀ
Autonoma de Barcelona in an Esquire 3000 ion trap mass spec-
trometer from Bruker Daltonics. Mass experiments were done on
acetonitrile solvent. Matrix assisted laser desorption/ionization
(MALDI) time-of flight (TOF) mass spectrometry were carried out
by the staff of the Institut de Biotecnologia i Medicina of the Uni-
A solution of nBuLi (16 ml, 25.3 mmol, 1.6 M in hexane) was
added dropwise to a stirred solution of PPh2H (1.38 ml, 8.0 mmol)
in dry THF (10 ml) at ꢁ77 ꢀC (acetone/CO2). After 30 min, the so-
lution of PPh2Li was added dropwise to a stirred solution of 1-
(chloromethyl)-3,5-dimethylpyrazole (LCl1$HCl) (1.16 g, 8 mmol)
for LP1 or 1-(chloropropyl)-3,5-dimethylpyrazole (LCl3$HCl)
(1.39 g, 8 mmol) for LP3, in THF (20 ml) at ꢁ77 ꢀC. The mixture was
maintained at ꢁ77 ꢀC for 1 h. The temperature was then raised to
room temperature and after 12 h of stirring the solvent was evap-
orated under vacuum. 40 ml of dichloromethane were added to the
residue and the salts were extracted with 3 ꢂ 10 ml of distilled
water. Evaporation of the solvent from the organic phase gives 1-
[2-(diphenylphosphanyl)methyl]-3,5-dimethylpyrazole (LP1) and
ꢀ
versitat Autonoma de Barcelona on a positive ion mode on a
Bruker-Daltonics Ultroflex time-of-flight instrument. Ion accelera-
tion was set to 25 KV. All mass spectra were externally calibrated
using a standard peptide mixture. The sample was dissolved in
CHCl3 and mixed with 2,5-dihydroxybenzoic acid (DHB) solution
matrix (0.5
ml matrix). The mixed solution was applied on a ground
steel plate (1
ml). The quantification of the catalytic reaction was
carried out using a Hewlett Packard HP5890 gas chromatograph
equipped with a flame ionization detector (FID), and a Hewlett

262
M. Guerrero et al. / Journal of Organometallic Chemistry 799-800 (2015) 257e264
1-[2-(diphenylphosphanyl)propyl]-3,5-dimethylpyrazole (LP3) as a
yellowish oils.
LP1: (Yield: 99%, 2.33 g). Anal. Calc. for C18H19N2P: C, 73.45, H,
6.51; N, 9.52. Found: C, 73.81; H, 6.44; N, 9.39%. MS (ESIþ): m/z (%):
295 (97%) [LP1 þ H]þ, 311 (100%) [LP1(O) þH]þ (LP1(O) ¼ oxidized
(m, 2H, pz-CH2-CH2-P), 2.37 (s, 3H, pz-CH3), 2.19 (s, 3H, pz-CH3)
ppm. 13C{1H} NMR (CD2Cl2 at 298 K, 63 MHz)
d: 152.9, 134.4e127.2
(C6H5), 107.6 (pz-CH), 45.5 (pz-CH2-CH2-P), 27.6 (d, 1JPC ¼ 32.4 Hz,
pz-CH2-CH2-P), 14.7 (pz-CH3), 11.0 (pz-CH3) ppm. 31P{1H} NMR
(CD2Cl2 at 298 K, 81 MHz) d: 23.9 (s, P-C6H5) ppm.
ligand). IR: (NaCl, cmꢁ1): 3051
n
(CeH)ar, 2922
(C]C/C]N)ar, 787 (PeC), 739, 695
NMR (CDCl3 at 298 K, 250 MHz) : 7.47 (m, 10H, C6H5), 5.65 (s, 1H,
n
(CeH)al, 1552
n
(C]
3 (Yield: 40%, 0.054 g). Anal. Calc. for C20H23N2PCl2Pd: C, 47.93;
H, 4.41; N, 5.30. Found: C, 47.72; H, 4.13; N, 5.59%. MS (MALDI-TOF):
m/z (%): 465 (100%) [PdCl(LP3)]þ, 523 (30%) [PdCl(LP3) þ Na]þ.
C/C]N)ar, 1433
d
n
d
(CeH)oop. 1H
d
2
pz-CH), 4.61 (d, 2H, JPH ¼ 4.7 Hz, pz-CH2-P), 2.18 (s, 3H, pz-CH3),
Conductivity (1.05 ꢂ 10ꢁ3 M in acetonitrile): 6
U
ꢁ1cm2molꢁ1. IR:
(C]C/C]N)ar,
(CeH)oop; (poly-
(Pd-Cl), 309
(Pd-P). 1H
d: 7.63 (m, 10H, C6H5), 5.99 (s, 1H,
1.83 (s, 3H, pz-CH3) ppm. 13C{1H} NMR (CDCl3 at 298 K, 63 MHz)
d
:
(KBr, cmꢁ1) 3055
n(CeH)ar, 2959 n(CeH)al, 1554 n
1
148.3, 139.9 (pz-CCH3), 136.9 (d, JPC
¼
14.9 Hz, P-C6H5),
1435
ethylene, cmꢁ1) 457
NMR (CDCl3 at 298 K, 250 MHz)
d(C]C/C]N)ar, 798
n(PeC), 743, 691 d
133.8e128.3 (C6H5), 105.7 (pz-CH), 50.6 (d, 1JPC ¼ 14.6, pz-CH2-P),
n(Pd-N), 355, 337
n
n
4
14.0 (pz-CH3), 11.5 (d, JPC ¼ 3.3 Hz, pz-CH3) ppm. 31P{1H} NMR
(CDCl3 at 298 K, 81 MHz)
d
: ꢁ18.4 (s, P-C6H5) ppm.
pz-CH), 5.69/4.25 (m, 1H/1H, pz-CH2-CH2-CH2-P), 1.89/1.21 (m,2H/
2H, pz-CH2-CH2-CH2-P), 2.44 (s, 3H, pz-CH3), 2.23 (s, 3H, pz-CH3)
LP3: (Yield: 95%, 2.45 g). Anal. Calc. for C20H23N2P: C, 74.51, H,
7.19; N, 8.69. Found: C, 74.95; H, 7.23; N, 8.33%. MS (ESIþ): m/z (%):
323 (46%) [LP3 þ H]þ, 339 (100%) [LP3(O) þH]þ (LP3(O) ¼ oxidized
ppm. 13C{1H} NMR (CDCl3 at 298 K, 63 MHz)
d: 135.3e128.4 (C6H5),
109.9 (pz-CH), 47.6 (pz-CH2-CH2-CH2-P), 24.9, 23.4 (pz-CH2-CH2-
ligand). IR: (NaCl, cmꢁ1): 3047
n
(CeH)ar, 2919
(C]C/C]N)ar, 778 (PeC), 742, 698
NMR (CDCl3 at 298 K, 250 MHz) : 7.45 (m, 10H, C6H5), 5.66 (s, 1H,
n
(CeH)al, 1551
n(C]
CH2-P), CH2-CH2-CH2-P), 15.7 (pz-CH3), 12.0 (pz-CH3) ppm. 31P{1H}
C/C]N)ar, 1433
d
n
d
(CeH)oop. 1H
NMR (CDCl3 at 298 K, 81 MHz) d: 11.6 (s, P-C6H5) ppm.
d
4 (Yield: 56%, 0.092 g). Anal. Calc. for C29H25N2PCl2Pd: C, 57.12;
H, 4.13; N, 4.59. Found: C, 56.95; H, 4.05; N, 4.63%. (MALDI-TOF): m/
z (%): 575 (100%) [PdCl(LP4)]þ. Conductivity (1.08 ꢂ 10ꢁ3 M in
pz-CH), 3.96 (m, 2H, pz-CH2-CH2-CH2-P), 1.87 (m, 2H/2H, pz-CH2-
CH2-CH2-P), 2.12 (s, 3H, pz-CH3), 2.08 (s, 3H, pz-CH3) ppm. 13C{1H}
NMR (CDCl3 at 298 K, 63 MHz)
d
: 147.6, 139.0 (pz-CCH3), 138.7 (d,
acetonitrile): 8
U
n
ꢁ1cm2molꢁ1. IR: (KBr, cmꢁ1) 3056
n
(CeH)ar, 2907
(C]C/C]N)ar, 802 (PeC),
(Pd-N), 360, 345
(Pd-P). 1H NMR (CD3CN at 298 K, 250 MHz)
: 7.71
1JPC ¼ 12.6 Hz, P-C6H5), 134.4 (d, 1JPC ¼ 17.1 Hz, P-C6H5), 133.6e128.5
n
(CeH)al, 1552
(C]C/C]N)ar, 1436
d
n
3
(C6H5), 105.3 (pz-CH), 49.7 (d, JPC ¼ 14.1 Hz, pz-CH2-CH2-CH2-P),
765, 693
d
(CeH)oop; (polyethylene, cmꢁ1) 461
n
27.2 (d, 1JPC ¼ 16.8 Hz, pz-CH2-CH2-CH2-P), 25.2 (d, JPC ¼ 12.0 Hz,
n(Pd-Cl), 332
n
d
2
pz-CH2-CH2-CH2-P), 13.9 (pz-CH3), 7.1 (pz-CH3) ppm. 31P{1H} NMR
(m, 20H, C6H5), 6.73 (s,1H, pz-CH), 5.03 (m, 2H, pz-CH2-CH2-P), 2.60
(m, 2H, pz-CH2-CH2-P), 2.21 (s, 3H, pz-CH3), 1.79 (s, 3H, pz-CH3)
(CDCl3 at 298 K, 81 MHz)
d: ꢁ19.1 (s, P-C6H5) ppm.
ppm. 31P{1H} NMR (CD3CN at 298 K, 81 MHz)
ppm.
d: 21.0 (s, P-C6H5)
4.3. Synthesis of the complexes
4.3.1. Complexes [PdCl2(LP)] (LP ¼ LP1 (1), LP2 (2), LP3 (3) and LP4
(4))
4.4. X-ray crystal structure for complexes 2 and 3
The appropriate ligand (0.270 mmol: LP1, 0.079 g; LP2, 0.083 g;
LP3, 0.087 g; LP4, 0.117 g) dissolved in dry CH2Cl2 (10 ml) was
added to a solution of the palladium complex [PdCl2(CH3CN)2]
(0.270 mmol, 0.070 g) in dry CH2Cl2 (15 ml). The orange solutions
were stirred at room temperature for 12 h. The resulting solutions
were concentrated until 5 ml. For solution that contain the LP2
ligand, a yellow pure solid was obtained by precipitation. Cold dry
diethyl ether (5 ml) was added dropwise to the solution of LP1, LP3
and LP4. After one hour at 4 ꢀC an orange pure solid was obtained
for LP1 and yellow solids were obtained for LP3 and LP4. The solids
were washed with cold dry diethyl ether.
Crystals of complexes 2 and 3 suitable for X-ray diffraction were
obtained through recrystallization from CH2Cl2/diethyl ether mix-
tures. Prismatic crystals were selected and mounted on a MAR 345
diffractometer with an image plate detector. Unit cell parameters
were determined form 47 reflections for 2 and 17380 reflections for
3 (3 <
q
< 31ꢀ) and refined by least-squares method. Intensities
radiation.
ꢃ 30.00 for
were collected with graphite monochromatized Mo K
a
24329 reflections were measured in the range 2.56 ꢃ
q
2, which 5646 were non-equivalent by symmetry (Rint (on
I) ¼ 0.035). 5619 reflections were assumed as observed applying
the condition I > 2
2.63 ꢃ
applying the condition I > 2
s. 5717 reflections were measured in the range
1 (Yield: 11%, 0.014 g). Anal. Calc. for C18H19N2PCl2Pd: C, 45.84;
H, 4.06; N, 5.94. Found: C, 45.60; H, 3.83; N, 6.21%. MS (MALDI-
TOF): m/z (%): 437 (100%) [PdCl(LP1)]þ. Conductivity (1.02 ꢂ 10ꢁ3 M
q
ꢃ 32.88 for 3 which 5330 were assumed as observed
s(I). Three reflections were measured
every two hours as orientation and intensity control, significant
intensity decay was not observed. Lorenz-polarization and ab-
sorption corrections were made.
For 2 and 3, the structure was solved by direct methods, using
SHELS-97 computer program [18] and refined by full matrix least-
squares method with SHELXL-97 computer program [19], using
24329 reflections for 2 and 5717 reflections for 3. The function
in acetonitrile): 2
2958, 2915 (CeH)al,1555
(PeC), 744, 690
(CeH)oop; (polyethylene, cmꢁ1) 463
(Pd-P). 1H NMR (CDCl3 at 298 K, 250 MHz)
U
ꢁ1cm2molꢁ1. IR: (KBr, cmꢁ1) 3053
n
(CeH)ar,
(C]C/C]N)ar, 798
(Pd-N), 358,
n
n(C]C/C]N)ar, 1436 d
n
342
d
n
n
(Pd-Cl), 325
n
d:
2
7.63 (m, 10H, C6H5), 5.86 (s, 1H, pz-CH), 4.70 (d, 2H, JPH ¼ 8.1 Hz,
pz-CH2-P), 2.56 (s, 3H, pz-CH3), 2.28 (s, 3H, pz-CH3) ppm. 13C{1H}
NMR (CDCl3 at 298 K, 63 MHz)
d
: 148.1, 139.9 (pz-CCH3), 136.8 (d,
minimized was SwkFor2 - rFcr2r2, where w ¼ [
s
2(I) þ 4.8616P]ꢁ1
,
þ
1JPC ¼ 14.7 Hz, P-C6H5), 135.2e128.5 (C6H5), 109.5 (pz-CH), 49.2 (d,
and
P
¼
(rFo2r2
þ
2
rFcr2)/3 for 2, and
w
¼
[
s
2(I)
1JPC ¼ 37.4, pz-CH2-P), 15.2 (pz-CH3), 12.4 (d, pz-CH3) ppm. 31P{1H}
(0.0567P)2 þ 0.4027P]ꢁ1 for 3. For 2, all H atoms are computed and
refined, using a riding model, with an isotropic temperature factor
equal to 1.2 times the equivalent temperature factor of the atom
which is linked. For 3, 2H atoms were located from a difference
synthesis and refined with isotropic temperature factor and 21H
atoms were computed and refined, using a riding model, with an
isotropic temperature factor equal to 1.2 times the equivalent
temperature factor of the atom which is linked.
NMR (CDCl3 at 298 K, 81 MHz) d: 35.3 (s, P-C6H5) ppm.
2 (Yield: 86%, 0.113 g). Anal. Calc. for C19H21N2PCl2Pd: C, 46.74;
H, 4.20; N, 5.66. Found: C, 47.07; H, 4.64; N, 5.61%. (MALDI-TOF): m/
z (%): 451 (100%) [PdCl(LP2)]þ. Conductivity (1.12 ꢂ 10ꢁ3 M in
acetonitrile): 7
U
n
ꢁ1cm2molꢁ1. IR: (KBr, cmꢁ1) 3046
n
(CeH)ar, 2923
(C]C/C]N)ar, 793 (PeC),
(Pd-N), 347, 328
(Pd-P). 1H NMR (CD2Cl2 at 298 K, 250 MHz)
: 7.55
(m, 10H, C6H5), 5.75 (s, 1H, pz-CH), 4.81 (m, 2H, pz-CH2-CH2-P), 2.61
n
(CeH)al, 1552
(C]C/C]N)ar, 1436
d
n
746, 693
d
(CeH)oop; (polyethylene, cmꢁ1) 452
n
n(Pd-Cl), 314
n
d
The parameters refined and other details concerning the
refinement of the crystal structures are gathered in Table 3.

M. Guerrero et al. / Journal of Organometallic Chemistry 799-800 (2015) 257e264
263
Table 3
Crystallographic data for 2 and 3.
2
3
Formula
C19H21Cl2N2PPd
485.65
293(2)
C20H23Cl2N2PPd
499.67
293(2)
Formula weigh
Temperature (K)
Wavelength (Å)
System, space group
a, b, c (Å)
0.71073
0.71073
Monoclinic, P21/n
14.300(7),10.054(5), 15.273(4)
113.94(2)
2006.94(15)/4
1.607/1.275
Monoclinic, P21/n
11.857(4),8.343(3), 21.298(4)
101.22(2)
2066.6(11)/4
1.606/1.241
b
(ꢀ)
U (Å3)/Z
Dcalc (g cmꢁ3)/
F(000)
m )
(mmꢁ1
976
1008
Crystal size (mm3)
hkl ranges
0.2 ꢂ 0.1 ꢂ 0.1
ꢁ19 ꢃ h ꢃ 21, ꢁ14 ꢃ k ꢃ 13,
ꢁ23 ꢃ l ꢃ 23
2.56e30.00
0.2 ꢂ 0.1 ꢂ 0.1
ꢁ15 ꢃ h ꢃ 15, 0 ꢃ k ꢃ 12,
0 ꢃ l ꢃ 30
2
q
Range (ꢀ)
2.63e32.88
Reflections
24329/5646
5717/5717
collected/unique/[Rint
]
[R(int) ¼ 0.0352]
[R(int) ¼ 0.0311]
Completeness to
q (%)
96.4
97.1
Absorption correction
Max. and min. trans.
Empirical
0.880 and 0.858
5646/3/227
Empirical
0.88 and 0.86
5717/0/245
Data/restrains/parameters
Goodness-of-fit on F2
1.324
1.140
Final R indices [I > 2
R indices (all data)
s
(I)]
R1 ¼ 0.0458, wR2 ¼ 0.0839
R1 ¼ 0.0460, wR2 ¼ 0.0840
þ0.672, ꢁ0.453
R1 ¼ 0.0379, wR2 ¼ 0.0920
R1 ¼ 0.0400, wR2 ¼ 0.0936
þ0.747, ꢁ0.686
Largest diff. peak and
hole (e Åꢁ3
)
140e149.
Acknowledgement
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ꢁ
Support by the Spanish Ministerio de Educacion y Cultura 2007-
2011 (projecte CTQ 2007-63913 BQU) is gratefully acknowledged.
Also, The MEC MAT2011-27225 and the 2014SGR260 projects are
acknowledged. Dr. Miguel Guerrero acknowledges the support of
the Secretary for Universities and Research of the Government of
Catalonia and the COFUND Programme of the Marie Curie Actions
of the 7th R&D Framework Programme of the European Union for
the ‘Beatriu de Pinos’ contract (2013 BP-B 00077).
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Crystallographic data for the structural analysis has been
deposited with the Cambridge Crystallographic Data Centre, CCDC
reference number 1411684 for compound 2 and 1411685 for com-
pound 3. Copies of this information may be obtained free of charge
from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK:
fax: þ44 1223336033; e-mail: deposit@ccdc.cam.acuk or www.
htpp://ccdc.cam.ac.uk.
(i) A. Pal, R. Ghosh, N.N. Adarsh, A. Sarkar, Tetrahedron 66 (2010) 5451e5458;
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Supplementary data related to this article can be found at http://
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