Synthesis and characterization of new N-alkylamino-3,5-diphenylpyrazole ligands and reactivity toward PdII and PtII. Study of the cis-trans isomerization

Article abstract of DOI:10.1071/CH09371

In this paper, the synthesis and characterization of two new N-alkylaminopyrazole ligands, 1-[2-(ethylamino)ethyl]-3,5-diphenylpyrazole (dpea) and 1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole (dpoa) are reported. The reaction of these ligands with [MCl

Full text of DOI:10.1071/CH09371

Full Paper
CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2010, 63, 257–269
Synthesis and Characterization of New N-Alkylamino-
3,5-diphenylpyrazole Ligands and Reactivity Toward
PdII and PtII. Study of the cis–trans Isomerization
Gemma Aragay,A Josefina Pons,A,D Vicenç Branchadell,B Jordi García-Antón,A
Xavier Solans,C,‡ Mercé Font-Bardía,C and Josep RosA
ADepartament de Química, Unitat de Química Inorgànica, Universitat Autònoma de Barcelona,
08193-Bellaterra, Barcelona, Spain.
BDepartament de Química, Unitat de Química Física, Universitat Autònoma de Barcelona,
08193-Bellaterra, Barcelona, Spain.
CCristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona,
Martí i Franqués s/n, 08028-Barcelona, Spain.
DCorresponding author. Email: josefina.pons@uab.es
‡Deceased 3 September 2007.
In this paper, the synthesis and characterization of two new N-alkylaminopyrazole ligands, 1-[2-(ethylamino)ethyl]-3,
5-diphenylpyrazole (dpea) and 1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole (dpoa) are reported. The reaction of these
ligandswith[MCl2(CH3CN)2](M = PdII, PtII)affordsthefollowingsquareplanarcomplexes: cis-[MCl2(NNꢀ)](M = PdII:
NNꢀ = dpea, 1; dpoa, 2; M = PtII: NNꢀ = dpea, 3; dpoa, 4). Reaction of [PdCl2(CH3CN)2] and dpea or dpoa in 1:2 M:NNꢀ
molar ratio, in the presence of NaBF4, yields complexes [Pd(NNꢀ)2](BF4)2 (NNꢀ = dpea, [5](BF4)2); dpoa, [6](BF4)2).
The solid-state structures of complexes 1, 3, and [5](BF4)2 have been determined by single-crystal X-ray diffraction
methods. In complexes 1 and 3, the dpea ligand is coordinated through the Npz and Namino atoms to the metallic centre,
which completes its coordination with two chlorine atoms in a cis disposition. For complex [5](BF4)2, the crystal structure
consists of cations involving a [Pd(Npz)2(Namino)2]2+ core with a cis disposition of the two dpea ligands in a square-planar
geometry and BF−4 anions.Theoretical calculations were carried out to optimize the geometries of the cis and trans isomers
of the [Pd(dpea)2]2+ cation and of the [Pd(dpea)2](BF4)2 complex. The results show that the trans isomer is the most
stable for [Pd(dpea)2]2+, in contrast with the cis stereochemistry observed in the crystal structure of [Pd(dpea)2](BF4)2.
The calculations also predict that in acetonitrile solution, the dissociation of this complex into the corresponding ions
is thermodynamically favourable. The cis–trans isomerization process of [Pd(dpea)2]2+ in acetonitrile solution has been
studied by NMR spectroscopy at different temperatures. These experimental results confirm that the trans isomer is the
thermodynamically most stable form of the complexes [5](BF4)2 and [6](BF4)2.
Manuscript received: 1 July 2009.
Manuscript accepted: 4 August 2009.
Introduction
and their coordination with NiII, CuII, and CoII, have
been widely studied by Driessen et al.[6] This information
has been complemented by other compounds presented by
Mukherjee.[7]
The coordination study of amino ligands, and basically of chelat-
ing nitrogen donor atoms, is of great importance owing to the
information that it provides to understand these systems in
nature and to indicate new roles for metal ions in therapeutic
strategies.[1] Moreover, the coordination of these kinds of lig-
ands with some specific metals like palladium, platinum, or zinc
allows the isolation of new compounds with applications in dif-
ferent fields such as catalysis[2] and luminescence,[3] and also
as therapeutic agents.[4]
Itisnecessarytoemphasizetheimportanceoftherelationship
between the structure (cis/trans isomer) and the activity of the
coordination compounds, mostly for medical applications.[5] For
this reason, it is important to continue the characterization and
structural studies of such complexes.
In this context, our group has reported, in recent years, the
synthesis and bonding properties of several new N-alkylamino-
3,5-dimethylpyrazole ligands (NNꢀ: 1-(2-(isopropylamino)
ethyl)-3,5-dimethylpyrazole and 1-(2-(tert-butylamino)ethyl)-
3,5-dimethylpyrazole; NNꢀN: bis((3,5-dimethyl-1-pyrazolyl)
methyl)isopropylamine, bis(2-(3,5-dimethyl-1-pyrazolyl)ethyl)
isopropylamine, and bis(2-(3,5-dimethyl-1-pyrazolyl)ethyl)tert-
butylamine) toward PdII,[8] PtII,[9] RhI,[10] and ZnII.[11]
Moreover, we recently synthesized four N-alkylamino-
pyrazole ligands containing phenyl groups in the 3 and 5
positions of the pyrazole ring (NNꢀ: 1-(2-(diethylamino)ethyl)-3,
5-diphenylpyrazoleand1-(2-(dioctylamino)ethyl)-3,5-diphenyl-
pyrazole; NNꢀN: bis(2-(3,5-diphenyl-1-pyrazolyl)ethyl)amine
Heterocyclic compounds containing nitrogen donor atoms
and alkylamino chains, such as N-alkylaminopyrazole ligands
© CSIRO 2010
10.1071/CH09371
0004-9425/10/020257

258
G. Aragay et al.
N
N
OTs
ϩ
NH2R (R ϭ ethyl, octyl)
2ϩ
NaOH (aq)
N
NHR
Pd
N
[PdCl2(CH3CN)2]
M:L ratio 1:2
N
N
2 NaBF4
N
NHR
RNH
N
R ϭ ethyl (dpea), octyl (dpoa)
R ϭ ethyl [5]2+
R ϭ octyl [6]2+
[MCl2(CH3CN)2]
M ϭ PdII or PtII
Cl
R ϭ ethyl, M ϭ PdII (1)
Cl
R ϭ octyl, M ϭ PdII (2)
M
R ϭ ethyl, M ϭ PtII (3)
R ϭ octyl, M ϭ PtII (4)
N
N
NHR
Scheme 1.
andbis(2-(3,5-diphenyl-1-pyrazolyl)ethyl)ethylamine)andstud-
ied their reactivity toward PdII.[12]
The ligands were characterized by elemental analyses,
mass spectrometry and IR, 1H and 13C{1H} NMR spec-
troscopy. The NMR signals were assigned by reference to the
literature[14] and from Distortionless Enhancement by Polariza-
tion Transfer (DEPT), COrrelation SpectroscopY (COSY), and
Heteronuclear Multiple Quantum Coherence (HMQC) NMR
experiments.
The presence of one alkyl-chain group instead of two at the
amine moiety is expected to affect the ability of the ligand to
coordinate the metal centre. With the aim of extending our last
work, and in order to evaluate this effect on the ligand coor-
dination mode, in the current paper, we present the synthesis
and characterization of two new N-alkylamino-3,5-diphenyl-
pyrazole ligands: 1-(2-(ethylamino)ethyl)-3,5-diphenylpyrazole
(dpea)and1-(2-(octylamino)ethyl)-3,5-diphenylpyrazole(dpoa),
along with the study of their reactivity toward [MCl2(CH3CN)2]
(M = PdII, PtII), obtaining the complexes [MCl2(NNꢀ)]
(M = PdII, PtII; NNꢀ = dpea, dpoa). We also report the prepara-
tionandspectroscopicpropertiesofcomplexes[Pd(NNꢀ)2](BF4)2
(NNꢀ = dpea, dpoa) (Scheme 1). Structural studies of these
complexes are also presented. The cis and trans isomers of
[Pd(dpea)2]2+ and [Pd(dpea)2](BF4)2 have been studied through
theoretical calculations and the results have been used to
rationalize the experimental observations.
Synthesis and Characterization of the Complexes
[MCl2(NNꢀ)] (M = PdII or PtII)
The reaction of [MCl2(CH3CN)2] (M = PdII or PtII) with
the corresponding ligand (NNꢀ), dpea or dpoa, in a 1:1 or
1:2 M:NNꢀ molarratioindichloromethaneforPdII oracetonitrile
for PtII complexes, yields compounds [MCl2(NNꢀ)] (M = PdII:
NNꢀ = dpea, 1; dpoa, 2; M = PtII: NNꢀ = dpea, 3; dpoa, 4). Sto-
ichiometries of these complexes do not depend on the M:NNꢀ
molar ratio.
Several techniques were used for the characterization of the
complexes: elemental analyses, mass spectrometry, conductiv-
ity measurements, IR, 1H, 13C{1H}, 1H{195Pt}, and 195Pt{1H}
NMR spectroscopy and X-ray diffraction methods. The NMR
signals were assigned from DEPT, COSY, HMQC, and nuclear
Overhauser effect correlation spectroscopy (NOESY) NMR
experiments.
Results and Discussion
Synthesis and Characterization of the Ligands
The dpea and dpoa ligands were obtained from the reaction of
1-(2-toluene-p-sulfonyloxyethyl)-3,5-diphenylpyrazole[13] with
the appropriate primary amine (dpea: ethylamine; dpoa: octyl-
amine) in the presence of sodium hydroxide in a tetrahydrofuran
(THF):water solution (dpea, 4:1; dpoa, 7:3). Both products were
obtained as yellow oils. The dpoa ligand was further purified by
chromatography (silica gel 60 Å) with ethyl acetate as eluent.
The elemental analyses for complexes 1–4 are in agreement
with the formula [MCl2(NNꢀ)]. Electrospray ionization mass
spectrometry (MS-ESI+) spectra of compounds 1–4 give peaks
with m/z values of 396 (100%) for 1, 480 (100%) for 2, 484
(76%) for 3, and 568 (100%) for 4, attributable to [MCl2(NNꢀ)–
HCl–Cl]+. Moreover, for compound 3, a peak with m/z value of
580 (100%), attributable to [PtCl2(dpea) + Na]+, is observed.

Synthesis and Characterization of New N-Alkylamino-3,5-diphenylpyrazole Ligands
259
C(12)
C(13)
C(14)
C(8)
These peaks are observed with the same isotopic distribution as
the theoretical one.
C(9)
C(11)
C(7)
Conductivity values for 10−3 M solutions of 1–4, in aceto-
nitrile, are in agreement with a non-electrolyte nature of the
complexes (1.8–12.7 ꢀ−1 cm2 mol−1).[15]
C(2)
C(10)
C(4)
C(1)
N(1)
C(6)
The IR spectra of complexes 1–4, in the range 4000–
400 cm−1, show signals corresponding to the coordinated lig-
ands. The most characteristic bands are those attributable to the
pyrazolyl group: ν(C=C), ν(C=N), and δ(C–H)oop. Another rel-
evant band is the one attributable to ν(N–H). The IR spectra of
complexes 1–4 in the 600–100 cm−1 region were also recorded.
Complexes 1 and 2 show one band corresponding to ν(Pd–N) at
398 and 405 cm−1, respectively, and two well-defined ν(Pd–Cl)
bands at 335, 326 cm−1 and 330, 318 cm−1, for 1 and 2 respec-
tively, which are typical of compounds with a cis disposition of
the chlorine atoms around PdII. Likewise, complexes 3 and 4
C(15)
C(3)
N(2)
C(5)
Cl(1)
C(16)
Pd
C(17)
N(3)
Cl(2)
C(19)
C(18)
show one band corresponding to ν(Pt–N) at 404 and 407 cm−1
,
respectively, and two ν(Pt–Cl) bands at 337, 328 cm−1, and
336, 329 cm−1, respectively, typical of compounds with a cis
disposition of the chlorine atoms around the PtII.[16]
Fig. 1. ORTEP drawing of [PdCl2(dpea)]·CH2Cl2, showing all non-
hydrogen atoms and the atom numbering scheme; 50% probability amplitude
displacement ellipsoids are shown.
The 1H, 13C{1H}, DEPT, COSY, HMQC, and NOESY NMR
spectra were recorded in CDCl3 for 1 and 2, and in CD3CN
C(2)
C(1)
C(12)
1
for 3 and 4. The H{195Pt} and 195Pt{1H} NMR spectra for 3
C(11)
and 4 were also recorded. NMR spectroscopic data are reported
C(8)
1
C(3)
in the Experimental section. H{195Pt}NMR spectra of com-
C(10)
C(6)
C(7)
C(13)
plexes 3 and 4 show the same signals (chemical shift and
multiplicity) as the 1H NMR spectra, suggesting that no coupling
between the PtII atom and the hydrogens of the ligands takes
place.
C(5)
C(14)
C(9)
C(15)
C(4)
N(1)
N(2)
In the 1H NMR spectra of complexes 1–4, the two pro-
tons of each CH2 group of the Npz–CH2–CH2–Namino chain
are diastereotopic, thus giving rise to four groups of signals,
each one attributable to a single hydrogen atom. This happens
because of the rigid conformation of the ligand once it has been
complexed. These signals appeared as four poorly defined sig-
nals and could not be further studied. HMQC spectra were useful
in order to assign the protons that correspond to the same CH2
group.
Cl(1)
Cl(2)
C(16)
Pt
C(17)
N(3)
C(19)
C(18)
Additional 195Pt{1H} NMR experiments for complexes 3 and
4 at 298 K were also recorded in CD3CN and displayed only one
signalforeachcomplex, at δ = −2008 ppmfor 3and−2106 ppm
for 4. These values appear in the range described in the litera-
ture for complexes with a [PtCl2N2] core (between −2447 and
−1198 ppm).[9,17,18]
Fig. 2. ORTEP drawing of [PtCl2(dpea)]·CH2Cl2, showing all non-
hydrogen atoms and the atom numbering scheme; 50% probability amplitude
displacement ellipsoids are shown.
Table 1. Selected bond lengths [Å] and bond angles [◦] for
[MCl2(dpea)]·CH2Cl2 (M = PdII [1]·CH2Cl2,M = PtII [3]·CH2Cl2)and
for [5](BF4)2
Crystal structures of [1]·CH2Cl2 and [3]·CH2Cl2 consist of
discrete [MCl2(dpea)] (M = PdII, 1; M = PtII, 3) units and sol-
vent molecules (CH2Cl2) linked by van der Waals forces (Figs 1
and 2, respectively).
1
3
The metal atom (PdII or PtII) is surrounded by an identical
core composed of the Npz and an Namino of one dpea ligand
and two chlorine atoms in a slightly distorted square-planar
geometry, with the chlorine atoms in cis disposition. The tetra-
hedral distortion can be observed from the bond angles and
from the largest deviation to the mean plane (0.054(3) Å (1) and
0.050(4) Å (3)) of the atoms coordinated to PdII (1) or PtII (3).
In both complexes, the dpea ligand acts as a bidentate chelate,
forming a six-membered metallacycle ring, with twist-boat con-
formation for M–N(1)–N(2)–C(16)–C(17)–N(3) (M = PdII, 1;
PtII, 3). Selectedbondlengthsandbondanglesforbothstructures
are listed in Table 1.
Pd–N(1)
Pd–N(3)
Pd–Cl(1)
Pd–Cl(2)
2.021(3)
2.062(4)
2.3119(12)
2.2864(12)
Pt–N(1)
Pt–N(3)
Pt–Cl(1)
Pt–Cl(2)
2.014(7)
2.074(8)
2.309(2)
2.299(2)
N(1)–Pd–N(3)
N(1)–Pd–Cl(1)
N(1)–Pd–Cl(2)
N(3)–Pd–Cl(1)
N(3)–Pd–Cl(2)
Cl(1)–Pd–Cl(2)
89.85(14)
90.19(10)
176.88(10)
171.69(10)
88.86(10)
91.50(5)
N(1)–Pt–N(3)
N(1)–Pt–Cl(1)
N(1)–Pt–Cl(2)
N(3)–Pt–Cl(1)
N(3)–Pt–Cl(2)
90.7(3)
90.1(2)
177.8(2)
172.8(2)
88.5(2)
Cl(1)–Pt–Cl(2)
91.04(10)
[5](BF4)2
Pd–N(1)
2.033(2)
Pd–N(3)
2.078(2)
ThePdCl2NpzNamino (terminalchlorine, aliphaticamine)core
is found in the literature as part of five crystal structures.[19]
We recently published three of these structures: [PdCl2(deae)],
N(1)–Pd–N(3)
N(1)#–Pd–N(1)
90.70(11)
89.14(13)
N(1)#–Pd–N(3)
N(3)#–Pd–N(3)
171.36(9)
90.74(14)

260
G. Aragay et al.
[PdCl2(deat)] (deae = 1-(2-(ethylamino)ethyl)-3,5-dimethyl-
The elemental analyses for compounds [5](BF4)2 and
[6](BF4)2 are consistent with the formula [Pd(NNꢀ)2](BF4)2.
MS-ESI+ spectra of compounds [5](BF4)2 and [6](BF4)2
give peaks with m/z values of 344 (100%) and 428 (100%),
respectively, attributable to [Pd(NNꢀ)2]2+. These peaks are
observed with the same isotopic distribution as the theoreti-
cal one.
pyrazole;
deat = 1-(2-(tert-butylamino)ethyl)-3,5-dimethyl-
pyrazole)[8a] and [PdCl2(L1)] (L1 = 1-(2-(diethylamino)ethyl)-
3,5-diphenylpyrazole).[12a] ThePd–Npz (2.021(3) Å), Pd–Namino
(2.062(4) Å), and Pd–Cl (2.3119(12) and 2.2864(12) Å) bond
lengths for complex 1 lie in the interval of distances
found for other structures described in the literature with
the same environment: 1.979–2.141 Å (Pd–Npz),[12a,20] 2.017–
2.280 Å (Pd–Namino),[8a,8d,12a,21] and 2.280–2.341 Å (terminal
Pd–Cl).[8a,8d,12a,21a–j] The Pd–Namino bond length for 1 is clearly
shorter thanthe samedistance for [PdCl2(L1)] (2.114(6) Å).This
could indicate that ligands with only one terminal alkyl chain
form stronger chelated structures than ligands with two terminal
alkyl chains, giving rise to the different behavior of these kind
of ligands when they coordinate PdII.[12a]
Conductivity values for 10−3 M solutions of complexes
[5](BF4)2 and [6](BF4)2 in acetonitrile are in agreement with
1:2 electrolyte compounds (270.4 and 296.3 ꢀ−1 cm2 mol−1
,
respectively).[15]
The IR spectra of complexes [5](BF4)2 and [6](BF4)2, in
the range 4000–400 cm−1, show signals corresponding to the
coordinated ligands. The most characteristic bands are ν(N–H),
ν(C=C), ν(C=N), δ(C–H)oop, and ν(B–F).[16] The IR spectra of
complexes [5](BF4)2 and [6](BF4)2 in the 600–100 cm−1 region
were also recorded. There is only one significant band in this
region corresponding to ν(Pd–N).[16]
The crystal structure of compound [5](BF4)2 consists of
discrete [Pd(dpea)2]2+ cations and BF−4 anions (Fig. 3).
The [Pd(dpea)2]2+ cation presents two dpea ligands in a cis
disposition, bonded to the PdII centre in a bidentate coordination
mode by the Npz and Namino atoms in a square-planar geometry,
forming two six-membered metalocyclic rings with twist-boat
conformation. Selected bond lengths and bond angles for this
structure are listed in Table 1.
The PtCl2NpzNamino (terminal chlorine, aliphatic amine) core
is found in the literature as part of two crystal structures.[19]
Our group has recently published one of these structures:
[PtCl2(deae)].[11]
The Pt–Npz (2.021(3) Å), Pt–Namino (2.062(4) Å), and Pt–
Cl (2.2863(12) and 2.3118(12) Å) bond lengths for complex 3
can be regarded as normal compared with the distances found
in the literature. For Pt–Npz, the literature describes values
between 1.981 and 2.138 Å,[18,20b,22,23] for Pt–Namino between
1.848 and 2.147 Å,[24] and for terminal Pt–Cl between 2.253
and 2.329 Å.[18,20b,22,23] No significant differences are observed
between Pt–Namino bond lengths in structure 3 and [PtCl2(deae)]
(2.073(10), 2.092(11) Å),[11] as happened with PdII complexes.
In this way, the change of methyl groups to phenyl groups in
these positions does not appear to have any remarkable effect on
the coordination features toward PtII.
This coordination mode, which involves a [Pd(Namino 2
)
(Npz)2]2+ core, is found in one single structure in the literature,
[Pd(deat)2](BF4)2.[8c]
Themetal–ligandbonddistancesfor[5](BF4)2 are2.033(2) Å
(Pd–Npz) and 2.078(2) Å (Pd–Namino). These values are con-
The Npz–M–Namino bite angles are 89.85(14)◦ for 1 and
90.7(3)◦ for 3. The bite angles for these complexes can also be
regardedasnormalcomparedwiththosereportedintheliterature
for [PdCl2(deae)] (89.3(2)◦),[8a][PdCl2(deat)] (88.16(18)◦),[8a]
[PtCl2(deae)] (90.3(4)◦),[11] and [PdCl2(L1)] (90.3(2)◦).[12a]
The Namino–H bonds are intermolecularly hydrogen-bridged
to a chlorine atom (Cl(1)). For complex 1, the N(3)–H(3N) bond
length is 0.894(11) Å and the contact parameters between N(3)–
H(3N) and Cl(1) are 2.497(12) Å for H(3N)· · ·Cl(1), 3.339(4) Å
for N(3)· · ·Cl(1), and 157.2(14)◦ for N(3)–H(3N)· · ·Cl(1). For
complex 3, the N(3)–H(3N) bond length has been geometri-
cally fixed in refinement (0.91 Å) and the contact parameters
between N(3)–H(3N) and Cl(1) are 2.52 Å for H(3N)· · ·Cl(1),
3.358(9) Å for N(3)· · ·Cl(1), and 153◦ for N(3)–H(3N)· · ·Cl(1).
The symmetry code for 1 and 3 is −x, 1/2 + y, 1/2 − z.
sistent with those described in the literature: 1.979–2.140 Å
[8a,8d,12a,21]
for Pd–Npz[12a,20] and 2.017–2.280 Å for Pd–Namino
.
The value for the Namino–Pd–Npz bite angle (90.70(11)◦) is
greater than that found for [Pd(deat)2](BF4)2 (87.47(6)◦), which
presents the same core.[8c] The main difference between the
structure of complex [5](BF4)2 and [Pd(deat)2](BF4)2 lies in the
disposition of the two ligands. For [Pd(deat)2](BF4)2,[8c] the lig-
ands are in a trans disposition, while for complex [5](BF4)2, the
dpea ligands are in a cis disposition and the ligands adopt an anti
disposition of the terminal chains to minimize steric hindrance.
The phenyl groups of the dpea ligand are able to arrange
themselves in a way that allows the π–π interaction between
a phenyl ring of one ligand and the pyrazole ring of the other
ligand in the same cation. The centroidpz–centroidph distance is
3.7 Å and the angle between the phenyl plane and the pyrazole
plane is 21.6◦ (Fig. 4). These parameters are in agreement with
those described in the literature for π–π interactions.[25]
Moreover, the Namino–H bonds are intermolecularly
hydrogen-bridged to a fluorine atom (F(1)) of a BF−4 anion. The
N(3)–H(3N) bond length is 0.90(4) Å and the contact parameters
between N(3)–H(3N) and F(1) are 2.22(4) Å for H(3N)· · ·F(1),
2.09 (4) Å for H(3N)· · ·F(1ꢀ), 3.043(17) Å for N(3)· · ·F(1),
2.932(18) Å for N(3)· · ·F(1ꢀ), 153(4)◦ for N(3)–H(3N)· · ·F(1)
and 156(4)◦ for N(3)–H(3N)· · ·F(1ꢀ). The symmetry code is
1 − x, y, −z + 1/2.
Synthesis and Characterization of the Complexes
[Pd(NNꢀ)2](BF4)2
Complexes [Pd(NNꢀ)2](BF4)2 (NNꢀ = dpea, [5](BF4)2; dpoa,
[6](BF4)2) were obtained by treatment of the corresponding
ligand with [PdCl2(CH3CN)2] in a 1:2 M:NNꢀ molar ratio in
acetonitrile and in the presence of NaBF4 in order to pro-
voke the precipitation of the chloride ions. Note that the same
stoichiometric conditions (1:2 M:NNꢀ molar ratio) without the
presence of NaBF4 led to the formation of molecular complexes
[PdCl2(NNꢀ)] (NNꢀ = dpea, 1; dpoa, 2).
NMR spectroscopic data are reported in the Experimental
1
section. H NMR spectra of [5]2+ and [6]2+ at variable tem-
Several techniques were used for the characterization of the
complexes: elemental analyses, mass spectrometry, conductiv-
ity measurements, IR, 1H and 13C{1H} NMR spectroscopy and
X-ray diffraction methods.The NMR signals were assigned from
DEPT, COSY, HMQC, and NOESY NMR experiments.
peratures (338–233 K) in CD3CN did not show any splitting or
broadening of the signals.
For complexes [5](BF4)2 and [6](BF4)2, both ligands in each
one of the complexes are equivalent. 1H NMR spectra were stud-
ied in detail. If we focus our attention on the protons of the

Synthesis and Characterization of New N-Alkylamino-3,5-diphenylpyrazole Ligands
261
C(4Ј)
C(4)
C(12)
C(5Ј)
C(12Ј)
C(5)
C(11Ј)
C(8Ј)
C(6Ј)
C(7Ј)
C(13Ј)
C(11)
C(13)
C(8)
C(6)
C(3Ј)
C(3)
C(2Ј)
C(14Ј)
C(10Ј)
C(9Ј)
C(7)
C(10)
C(9)
C(15Ј)
C(14)
C(2)
N(2Ј)
C(1Ј)
C(15)
C(1)
N(2)
N(1Ј)
N(1)
C(16Ј)
C(16)
Pd
C(17Ј)
C(17)
N(3Ј)
N(3)
C(18Ј)
C(19Ј)
C(18)
C(19)
Fig. 3. ORTEP drawing of [Pd(dpea)2]2+, showing all non-hydrogen atoms and the atoms numbering scheme; 50% probability
amplitude displacement ellipsoids are shown.
3.675
3.567
Fig. 4. View of the π–π stacking interactions between the pyrazole ring and the phenyl ring in [Pd(dpea)2]2+
.

262
G. Aragay et al.
NH
H16a
H16b
H18 H17a
H18
H17b
2
4
6
8
Hph
Hortho
6.0
5.5
5.0
4.5
4.0
3.5
3.0
F2 [ppm]
Fig. 5. The 250-MHz 2D NOESY spectrum of [Pd(dpea)2]2+ in CD3CN at 298 K.
C(4)
Phenyl A
C(5)
C(19Ј)
C(3)
C(11)
C(12)
C(8)
C(6)
C(7)
C(18Ј)
C(2)
N(3Ј)
C(13)
C(9)
C(10)
C(17Ј)
C(1)
N(2)
N(1)
C(14)
C(15)
C(16Ј)
N(2Ј)
Pd
C(16)
Phenyl BЈ
Phenyl B
C(15Ј)
C(14)
N(3)
N(1Ј)
C(1Ј)
C(2Ј)
C(17)
C(9Ј)
C(7Ј)
C(10Ј)
C(13Ј)
C(18)
C(6Ј)
C(5Ј)
C(8Ј)
C(11Ј)
C(3Ј)
C(12Ј)
C(19)
Phenyl AЈ
C(4Ј)
Fig. 6. Optimized structure of the trans isomer of [Pd(dpea)2]2+. Hydrogen atoms have been omitted
for clarity.
terminal alkyl chains, protons C(18)–H (Fig. 3) appear as two
multiplets at δ = 3.64, 2.99 ([5]2+) and 3.36, 2.60 ppm ([6]2+).
However, protons C(19)–H, corresponding to the methyl group
of the terminal alkyl chain for [5]2+ and the rest of the protons of
the octyl chain for [6]2+ appear as a single signal for each CH2
or CH3 (for the octyl chain, most of them appear to overlap) at
δ = 1.40 ([5]2+) and 1.34, 0.90 ppm ([6]2+).
described (Fig. 3). In fact, in the crystal structure, the short-
est distances between protons of the terminal alkyl chain and
protons of the phenyl groups are between C(18)–H and C1–H
protons (3.643 and 4.055 Å), and between C(19)–H and C1–H
protons (5.917, 5.840, and 6.169 Å).
However, these NOE interactions would be possible if the two
ligands in complexes [5](BF4)2 and [6](BF4)2 are in the trans
disposition. For this reason, we have optimized the geometries of
the cis and trans isomers of [5]2+ and [5](BF4)2. The structure
of the optimized trans isomer of [5]2+ is shown in Fig. 6.
In the trans isomer, the shortest distances between the protons
of the terminal chain and the protons at the phenyl groups are
NOESY spectra of these compounds were also studied
(Fig. 5). Complexes [5](BF4)2 and [6](BF4)2 show NOE inter-
actions between protons C(18)–H/C(19)–H and the protons of
Ph(A) groups. These effects do not seem compatible with the
cis disposition obtained from the X-ray structure previously

Synthesis and Characterization of New N-Alkylamino-3,5-diphenylpyrazole Ligands
263
(a)
(b)
Table 2. 1H NMR results: chemical shifts [ppm] and 1H, 1H coupling
constants [Hz] for [5](BF4)2 and [6](BF4)2 in CD3CN
trans
trans
trans
trans
3 h 30 min
28 h
Compound
[5](BF4)2
[6](BF4)2
3 h
cis
cis
14 h
6 h
δ Hamino
δ H (16a)
δ H (16b)
δ H (17a)
5.71
4.93
4.52
3.36
2.61
15.6
13.6
7.5
6.1
2.7
2.2
11.7
2.4
5.55
4.95
4.54
2.97
1.89
15.3
12.0
9.9
5.6
3.3
2.0
11.0
3.2
trans
trans
trans
cis
cis
15 min
cis
cis
δ H (17b)
2J(16a,16b)
2J(17a,17b)
2J(17a, Hamino
2J(17b, Hamino
3J(16a,17a)
3J(16b,17b)
3J(16a,17b)
3J(16b,17a)
6 min
trans
trans
5 h
)
)
cis
4 h
6.2
cis
0 min
6.2
6.4
6.3
[ppm]
6.4
6.3
[ppm]
Fig. 7. Evolution of the pyrazolic protons of the cis and trans isomers of
[Pd(dpea)2]2+ with time at (a) 298 K, (b) and 313 K.
determined at both temperatures, lead to an activation energy of
∼80 kJ mol−1
.
between C(18)–H and C1–H (3.099 and 3.816 Å), and between
C(19)–H and C(5ꢀ)–H (3.083, 4.523, and 4.792 Å). These dis-
tances are consistent with the NOESY data obtained in solution,
so that we may conclude that the complexes observed in aceto-
nitrile solution correspond to the trans isomers of [5]2+ and
[6]2+ cations.
In addition to the detailed study of the terminal chains, the
Npz–CH2–CH2–Namino fragment of compounds [5](BF4)2 and
[6](BF4)2 was also studied. The two protons of each CH2 group
in the Npz–CH2–CH2–Namino chain are diastereotopic, thus giv-
ing rise to four groups of signals, each one attributable to a single
hydrogen atom. Each group of signals can be assigned as two
doublets of doublets of doublets for C(16)–H and two doublets
of doublets of doublets of doublets for C(17)–H owing to the
additional coupling of this proton to Hamino. Treatment of the
Npz–CH2–CH2–Namino fragment as an AAꢀXXꢀ system gave a
set of coupling constants for each compound. These constants
were consistent with the simulated spectra obtained with the aid
of the gNMR program.[26] All the results are reported in Table 2.
Theoretical studies show that for the [5]2+ cation, the trans
isomer is more stable than the cis by 12.5 kJ mol−1 (ꢁG◦ at
298.15 K in acetonitrile). This difference leads to a predicted
trans:cis ratio of 99.4:0.6. However, the relative stabilities are
reversed when the [Pd(dpea)2](BF4)2 complexes are considered
and the cis isomer becomes the most stable by 48.5 kJ mol−1
(ꢁG◦ at 298.15 K in acetonitrile). The dissociation of these
complexes into [Pd(dpea)2]2+ + 2 BF−4 is thermodynamically
favourable in acetonitrile solution. The computed Gibbs reac-
tion energies at 298.15 K are −84.8 and −23.8 kJ mol−1 for the
trans and cis isomers, respectively. As we can observe, there is a
notable difference in the values of the Gibbs dissociation ener-
gies for cis and trans isomers. This difference is directly related
to the charge distribution of the cations. In the cis isomer, the
positive charge is more polarized than in the trans one, so that
the interaction with the BF−4 counteranions becomes favoured.
An additional experiment was performed in order to obtain
informationaboutthepresenceofcisortransisomersinsolution.
The reaction was carried out in an NMR tube in CD3CN at 298 K
(conditions described in Experimental section).The evolution of
the synthesis of complex [5](BF4)2 (up to 28 h) was monitored
by 1H NMR spectroscopy.
Fig. 7a shows the evolution of the pyrazole proton (CHpz) of
the cis and trans isomers of [5]2+ with time at 298 K. Up to 4 h
after the reaction begins, only one peak corresponding to CHpz
at 6.39 ppm is observed.This signal is assigned to the cis isomer.
From that time on, a second peak at 6.32 ppm, corresponding to
the trans isomer, begins to grow. As the time goes by, the peak
corresponding to the cis isomer decreases and finally disappears
28 h after the beginning of the reaction.Therefore, the kinetic cis
isomer is completely transformed into the trans isomer, which
is the thermodynamically most stable one.
1
Fig. 8 shows experimental and simulated H NMR spectra for
complex [5](BF4)2.
In the NOESY spectra of [5]2+ (Fig. 6) and [6]2+ in
CD3CN, one of the ortho hydrogens of the Ph(Aꢀ) groups
(δ = 7.81 ([5]2+) or 7.80 ppm ([6]2+)) shows NOE interaction
with the doublet of doublets of doublets at δ = 4.93 ([5]2+
or 4.95 ppm ([6]2+), but not with the ones at δ = 4.52 ([5]2+
first set of doublet of doublets of doublets at 4.93 ([5]2+
)
)
or 4.54 ppm ([6]2+). This allowed us to assign H–16a to the
)
or 4.95 ppm ([6]2+) (Fig. 8). These assignments were done
thanks to the trans structure obtained by computational stud-
ies, which shows that the shortest distances are between the
Hortho of Ph(Aꢀ) group at δ = 7.81 ppm and the doublet of
doublets of doublets at δ = 4.93 ppm (C(16a)–H· · ·C1ꢀ–H =
3.046 Å, Fig. 6) and between the Hmeta of the Ph(Aꢀ) group
(appearing as a part of the overlapped phenyl signals in the 1H
NMR spectrum of [5]2+) and the same doublet of doublets of
doublets at 4.93 ppm (C(16a)–H· · ·C2ꢀ–H = 3.374 Å, Fig. 6).
Therefore, C(16)–Hb was assigned to the set of doublet of
doublets of doublets at δ = 4.52 ([5]2+) or 4.54 ppm ([6]2+) and
presents NOE interaction with C(15)–H of the Ph(B) (C(16b)–
H· · ·C(15)–H = 2.548 Å).
Coupling constants (obtained from the gNMR-generated[17]
1H NMR simulated spectra, Fig. 8, Table 2) helped us to dif-
ferentiate between C(17)–Ha and C(17)–Hb. These coupling
constants agree with the conformation of the Npz–CH2–CH2–
Namino chains as seen in Fig. 8, which was corroborated by the
computational studies.
The same kind of experiment was also performed at 313 K.
In this case, the presence of the trans isomer is detected from
the beginning of the reaction, and the cis–trans conversion is
completed in 3.5 h (Fig. 7b). The isomerization rate constants,

264
G. Aragay et al.
2ϩ
Hb Ha
In addition to the experimental results, theoretical calcula-
tions have shown that the trans isomer of the [Pd(dpea)2]2+
cation is thermodynamically more stable than the cis one. If
we study [Pd(dpea)2](BF4)2 aggregates, the cis isomer becomes
the most stabilized one. The same calculations show that the
dissociation of [Pd(dpea)2](BF4)2 into [Pd(dpea)2]2+ + 2 BF4−
is predicted to be thermodynamically favourable in acetonitrile
solution.
Ph(BЈ)
Ha
H17a
Hb
N 16
NHEt
Pd
17
H16b
Npz
Ph(A)
N
Ph(AЈ)
H17b
Namino
N
N
H16a
EtNH
Ph(B)
Experimental
H17a
Experimental H17b
H16b
General Details
H16a
All reagents were commercial-grade materials and were used
without further purification. The reactions were carried out
under nitrogen using vacuum-line and Schlenk techniques. Sol-
vents were dried and distilled according to standard procedures
and stored under nitrogen. Elemental analyses (C, H, N) were
carried out by the staff of the Chemical Analyses Service of
Universitat Autònoma de Barcelona on an Euro Vector 3011
instrument. Conductivitymeasurementswereperformedatroom
temperature in 10−3 M acetonitrile solution employing a Cyber
Scan CON 500 (Euthech Instruments) conductimeter. Infrared
spectra were run on a Perkin–Elmer Fourier-transform (FT)
spectrophotometer, series 2000, as NaCl disks, KBr pellets or
polyethylenefilmsintherangeof4000–100 cm−1. 1H, 13C{1H},
COSY, HMQC, and NOESY NMR spectra were recorded with
an NMR-FT Bruker 250 MHz spectrometer in CDCl3 or CD3CN
solutions at room temperature. 195Pt{1H} NMR spectra were
recorded at 298 K and 77.42 MHz on a DPX-360 Bruker spec-
trometer using aqueous solution of [PtCl6]2− (0 ppm) as an
external reference and a 0.01 s delay time. All chemical shift
values (δ) are given in ppm. Mass spectra were obtained with an
Esquire 3000 ion-trap mass spectrometer from Bruker Daltonics.
The complexes [PdCl2(CH3CN)2][27] and [PtCl2(CH3CN)][28]
were synthesized according to published methods. The precur-
sor 1-(2-toluene-p-sulfonyloxyethyl)-3,5-diphenylpyrazole was
prepared as described in the literature.[13]
5.000
4.750
4.500
3.500
3.250
3.000
2.750
2.500
Simulated
Fig. 8. The 250-MHz 1H NMR and the simulated gNMR spectra for
the H-16 and H-17 protons of the Npz–CH2–CH2–Namino fragment of
[Pd(dpea)2]2+ in CD3CN at 298 K.
Geminal J and ∼180◦ 3J coupling constants have signifi-
2
cantly higher values than ∼30◦ and ∼60◦ 3J coupling constants
(Fig. 8, Table 2). Thus, C(17)–Ha should correspond to the dou-
blet of doublets of doublets of doublets at 3.36 ([5]2+) and
2.97 ppm ([6]2+) and C(17)–Hb to the ones at 2.61 ([5]2+) and
1.89 ppm ([6]2+).
Conclusions
Synthesis of the Ligands 1-(2-(Ethylamino)ethyl)-
3,5-diphenylpyrazole (dpea) and
1-(2-(Octylamino)ethyl)-3,5-diphenylpyrazole (dpoa)
The N-alkylamino-3,5-diphenylpyrazole ligands dpea and dpoa
act as bidentate ligands (Npz, Namino) forming chelated com-
pounds with cis-[MCl2(NNꢀ)] (M = PdII (1, 2) and PtII (3, 4))
stoichiometry. Complexes[Pd(NNꢀ)2](BF4)2 ([5–6](BF4)2)have
also been synthesized.
In complexes 1–4, the ligands show the same behaviour as
the complexes with ligands containing methyl moieties in posi-
tions 3 and 5 of the pyrazole ring,[8a,9] chelating the metallic
centre through the Npz and Namino atoms. However, complexes
1–4 do not further react to form zwitterionic or cyclopalla-
dated complexes as happened with the N-dialkylamino-3,5-
diphenylpyrazole ligands.[12a]
For complexes [5–6](BF4)2, we studied the cis–trans isomer-
ization by NMR spectroscopy. The crystal structure of complex
[5](BF4)2 shows that dpea ligands are in a cis disposition
in the solid state. However, 1H NMR experiments show that
the trans isomer is the isomer present in acetonitrile solution.
Furthermore, we have shown by 1H NMR experiments that the
thermodynamically favoured trans isomer of [Pd(dpea)2]2+ is
formed from the kinetic cis isomer in acetonitrile solution (28 h
at 298 K and 3.5 h at 313 K). These experiments served to cal-
culate the activation energy of the process, which was estimated
to be ∼80 kJ mol−1. The NOESY spectra for [5]2+ and [6]2+
were also consistent with the presence of trans species of these
compounds in solution.
The synthesis of the ligands consists of the reaction between
1-(2-toluene-p-sulfonyloxyethyl)-3,5-diphenylpyrazole (1.45 g,
3.47 mmol) and the appropriate primary amine (dpea, 1.47 g
of 70% ethylamine, 22.9 mmol; dpoa, 2.99 g of 99% octyl-
amine, 22.9 mmol) with sodium hydroxide (0.82 g of 98% purity,
20.1 mmol). The reaction was carried out in a solution of
THF:water (dpea, 4:1; dpoa, 7:3) (20 mL) with continuous stir-
ring and under reflux for 48 h. The mixture was cooled down
to room temperature and extracted three times with chloro-
form (3 × 10 mL). The organic phase was collected and dried
overnight with anhydrous Na2SO4. The solution was filtered off
and the solvent was removed under vacuum. Each product was
obtained as pale-yellow oil. In order to purify the ligand dpoa, a
silica-gel column (60 Å) with ethyl acetate as eluent was used.
The fractions containing pure dpoa ligand were gathered and
the solvent was removed under vacuum. After evaporation, a
pale-yellow oil was obtained.
dpea: (0.71 g, 70%) (Found: C 78.45, H 7.44, N 14.71.
C19H21N3 (291.1) requires C 78.32, H 7.26, N 14.41%.)
νmax(NaCl)/cm−1 ν(N–H) 3306, ν(C–H)ar 3060, ν(C–H)al
2963–2870, δ(N–H) 1680, ν(C=C)ph 1605, (ν(C=C)pz,
ν(C=N)pz) 1549, (δ(C=C)ar, δ(C=N)ar) 1461, δ(C–H)oop ph

Synthesis and Characterization of New N-Alkylamino-3,5-diphenylpyrazole Ligands
265
761, δ(C–H)oop pz 695. δH (250 MHz, CDCl3, 298 K) 7.85
(d, 2H, 3J 7.0, Hortho-3-ph), 7.41 (m, 8H, Hph), 6.60 (s, 1H,
CHpz), 4.27 (t, 2H,3J 6.1, NpzCH2CH2NH), 3.09 (t, 2H, 3J
1552, (δ(C=C)ar, δ(C=N)ar) 1482, 1466, δ(C–H)ip 1016, δ(C–
H)oop ph 762, δ(C–H)oop pz 695. νmax(polyethylene)/cm−1 ν(Pd–
N) 405, ν(Pd–Cl) 330, 318. δH (250 MHz, CDCl3, 298 K)
8.38 (d, 2H, 3J 7.8, Hortho-3-ph), 7.54 (m, 8H, Hph), 6.63 (s,
1H, CH(pz)), 5.90 (m, 1H, NpzCHHCH2NH), 5.63 (br, 1H,
NHCH2(CH2)6CH3), 4.53 (m, 1H, NpzCHHCH2NH), 3.32 (br,
1H, NpzCH2CHHNH), 3.12 (br, 1H, NHCHH(CH2)6CH3), 2.90
(br, 1H, NHCHH(CH2)6CH3), 2.10 (br, 1H, NpzCH2CHHNH),
1.96 (br, 1H, NHCH2CHH(CH2)5CH3), 1.73 (br, 1H, NHCH2
CHH(CH2)5CH3), 1.28 (br, 10H, NHCH2CH2(CH2)5CH3),
0.89 (t, 3H, 3J 6.9, NH(CH2)7CH3). δC (63 MHz, CDCl3, 298 K)
155.3, 147.9, 131.1, 130.2 (Cpz, Cph), 129.5–125.4 (Cph), 107.2
(CH(pz)), 55.5 (NpzCH2CH2NH), 51.5 (NpzCH2CH2NH), 49.6
(NHCH2(CH2)6CH3), 31.9–22.7 (NHCH2(CH2)6CH3), 14.2
(NHCH2(CH2)6CH3). m/z (ESI+) 480 (100%, [PdCl2(dpoa)–
HCl–Cl]+).
3
6.1, NpzCH2CH2NH), 2.59 (q, 2H, J 7.1, NHCH2CH3), 1.58
3
(br, 1H, NHCH2CH3), 1.09 (t, 3H, J 7.1, NHCH2CH3). δC
(63 MHz, CDCl3, 298 K) 151.2, 145.8, 133.9, 131.1 (Cpz, Cph),
129.5–126.0 (Cph), 103.8 (CH(pz)), 49.8 (NpzCH2CH2NH), 49.4
(NpzCH2CH2NH), 44.1 (NHCH2CH3), 15.7 (NHCH2CH3). m/z
(ESI+) 314 (12%, [M + Na]+), 298 (64%, [M + Li]+), 292
(100%, [M + H]+).
dpoa: (0.77 g, 59%) (Found: C 80.18, H 8.95, N 11.24.
C25H33N3 (375.3) requires C 79.90, H 8.90, N 11.20%.)
νmax(NaCl)/cm−1 ν(N–H) 3310, ν(C–H)ar 3061, ν(C–H)al
2926–2853, δ(N–H) 1679, ν(C=C)ph 1606, [ν(C=C)pz,
ν(C=N)pz] 1549, [δ(C=C)ar, δ(C=N)ar] 1480, 1463, δ(C–
H)oop ph 761, δ(C–H)oop pz 695. δH (250 MHz, CDCl3, 298 K)
7.77 (d, 2H, 3J 7.0, Hortho-3-ph), 7.35 (m, 8H, Hph), 6.52
(s, 1H, CHpz), 4.20 (t, 2H, 3J 6.0, NpzCH2CH2NH),
3.00 (t, 2H, 3J 6.0, NpzCH2CH2NH), 2.46 (t, 2H, 3J
7.0, NHCH2(CH2)6CH3), 1.76 (br, 1H, NHCH2(CH2)6CH3),
1.17 (br, 12H, NHCH2(CH2)6CH3), 0.80 (t, 3H, 3J 6.9,
NHCH2(CH2)6CH3). δC (63 MHz, CDCl3, 298 K) 151.0,
145.6, 134.1, 131.4 (Cpz, Cph), 129.5–126.0 (Cph), 103.7
(CH(pz)), 55.2 (NpzCH2CH2NH), 54.4 (NpzCH2CH2NH), 48.7
(NHCH2(CH2)6CH3), 32.2–23.1 (NHCH2(CH2)6CH3), 14.5
(NHCH2(CH2)6CH3). m/z (ESI+) 398 (6%, [M + Na]+), 376
(100%, [M + H]+).
Synthesis of Complexes [PtCl2(NNꢀ)] (NNꢀ = dpea 3;
dpoa 4)
A solution of the corresponding ligand (0.14 mmol: dpea,
0.041 g; dpoa, 0.053 g) in dry acetonitrile (10 mL) was added to
a solution of [PtCl2(CH3CN)2] (0.050 g, 0.14 mmol) in the same
solvent (10 mL).The mixture was stirred at reflux for 48 h.Then,
all the solvent was removed under vacuum. Dichloromethane
(5 mL)wasaddedtodissolvethesolid, andthencooldiethylether
(5 mL) was added to induce precipitation. The resulting pale-
yellow precipitate was filtered off, washed twice with diethyl
ether (3 mL), and recrystallized from a dichloromethane/diethyl
ether (4:1) mixture.
Synthesis of Complexes [PdCl2(NNꢀ)] (NNꢀ = dpea 1;
dpoa 2)
Compound 3 (0.058 g, 67%) (Found: C 37.61, H 3.85, N
6.33. C19H21Cl2N3Pt·CH2Cl2 (640.0) requires C 37.40, H 3.61,
N 6.54%.) Conductivity (ꢀ−1 cm2 mol−1, 9.0 × 10−4 M in ace-
tonitrile) 10.6. νmax(KBr)/cm−1 ν(N–H) 3129, ν(C–H)ar 2963,
ν(C–H)al 2921–2841, ν(C=C)ph 1595, (ν(C=C)pz, ν(C=N)pz)
1554, (δ(C=C)ar, δ(C=N)ar) 1480, 1466, δ(C–H)ip 1021, δ(C–
H)oop ph 762, δ(C–H)oop pz 696. νmax(polyethylene)/cm−1 ν(Pt–
N) 404, ν(Pt–Cl) 337, 328. δH (250 MHz, CD3CN, 298 K)
8.37 (d, 2H, 3J 6.7, Hortho-3-ph), 7.46 (m, 8H, Hph), 6.61
(s, 1H, CH(pz)), 6.33 (br, 1H, NHCH2CH3), 5.88 (m, 1H,
NpzCHHCH2NH), 4.32 (m, 1H, NpzCHHCH2NH), 3.41 (br,
1H, NpzCH2CHHNH), 3.28 (m, 1H, NHCHHCH3), 3.09 (m,
1H, NHCHHCH3), 2.15 (m, 1H, NpzCH2CHHNH), 1.36 (t,
3H, 3J 7.1, NHCH2CH3). δC (63 MHz, CD3CN, 298 K) 154.4–
130.2 (Cpz, Cph), 129.4–128.0 (Cph), 107.3 (CH(pz)), 51.2,
51.0 (NpzCH2CH2NH, NHCH2CH3), 49.5 (NpzCH2CH2NH),
13.6 (NHCH2CH3). δPt (77.42 MHz, CD3CN, 298 K) −2008.
m/z (ESI+) 580 (100%, [PtCl2(dpea) + Na]+), 484 (76%,
[PtCl2(dpea)–HCl–Cl]+).
Compound 4 (0.014 g, 16%) (Found: C 46.67, H 5.09, N
6.53. C25H33Cl2N3Pt (640.2) requires C 46.80, H 5.18, N
6.55%.) Conductivity (ꢀ−1 cm2 mol−1, 1.0 × 10−3 M in ace-
tonitrile) 7.7. νmax (KBr)/cm−1 ν(N–H) 3163, ν(C–H)ar 3055,
ν(C–H)al 2952–2853, ν(C=C)ph 1591, (ν(C=C)pz, ν(C=N)pz)
1551, (δ(C=C)ar, δ(C=N)ar) 1482, 1463, δ(C–H)ip 1021, δ(C–
H)oop ph 760, δ(C–H)oop pz 695. νmax(polyethylene)/cm−1 ν(Pt–
N) 407, ν(Pt–Cl) 336, 329. δH (250 MHz, CD3CN, 298 K)
8.35 (d, 2H, 3J 6.8, Hortho-3-ph), 7.50 (m, 8H, Hph), 6.61
(s, 1H, CHpz), 5.85 (m, 1H, NpzCHHCH2NH), 5.53 (br, 1H,
NHCH2(CH2)6CH3), 4.50 (m, 1H, NpzCHHCH2NH), 3.29 (br,
1H, NpzCH2CHHNH), 3.08 (m, 1H, NHCHH(CH2)6CH3), 2.87
(m, 1H, NHCHH(CH2)6CH3), 2.09 (m, 1H, NpzCH2CHHNH),
1.94 (br, 1H, NHCH2CHH(CH2)5CH3), 1.72 (br, 1H, NHCH2
A solution of the corresponding ligand (0.27 mmol: dpea,
0.079 g; dpoa, 0.101 g) in dry dichloromethane (10 mL) was
added to a solution of [PdCl2(CH3CN)2] (0.070 g, 0.27 mmol)
in the same solvent (10 mL). The mixture was stirred at room
temperature for 12 h. Then, most of the solvent was removed
under vacuum (5 mL). Cool diethyl ether (5 mL) was added
to induce precipitation. The resulting brown-orange precipitate
was filtered off, washed twice with cool diethyl ether (3 mL),
and recrystallized from a dichloromethane/diethyl ether (4:1)
mixture.
Compound 1 (0.105 g, 71%) (Found: C 43.50, H 4.33, N
7.87. C19H21Cl2N3Pd·CH2Cl2 (551.0) requires C 43.39, H 4.19,
N 7.59%.) Conductivity (ꢀ−1 cm2 mol−1, 1.0 × 10−3 M in ace-
tonitrile) 12.7. νmax(KBr)/cm−1 ν(N–H) 3164, ν(C–H)ar 3056,
ν(C–H)al 2976–2932, ν(C=C)ph 1620, (ν(C=C)pz, ν(C=N)pz)
1551, 1482, (δ(C=C)ar, δ(C=N)ar) 1466, δ(C–H)ip 1015, δ(C–
H)oop ph 762, δ(C–H)oop pz 696. νmax(polyethylene)/cm−1 ν(Pd–
N) 398, ν(Pd–Cl) 335, 326. δH (250 MHz, CDCl3, 298 K) 8.36
(d, 2H, 3J 7.2, Hortho-3-ph), 7.35 (m, 8H, Hph), 6.60 (s, 1H, CHpz),
5.90 (m, 1H, NpzCHHCH2NH), 5.71 (br, 1H, NHCH2CH3),
4.50 (m, 1H, NpzCHHCH2NH), 3.30 (br, 1H, NpzCH2CHHNH),
3.06 (m, 2H, NHCH2CH3), 2.10 (m, 1H, NpzCH2CHHNH),
1.42 (t, 3H, 3J 7.4, NHCH2CH3). δC (63 MHz, CDCl3, 298 K)
157.4–148.3 (Cpz, Cph), 131.3–128.7 (Cph), 107.5 (CH(pz)), 51.6
(NHCH2CH3), 50.0 (NpzCH2CH2NH), 49.2 (NpzCH2CH2NH),
14.4 (NHCH2CH3). m/z (ESI+) 396 (100%, [PdCl2(dpea)–
HCl–Cl]+).
Compound 2 (0.100 g, 67%) (Found: C 54.15, H 6.04,
N 7.90. C25H33Cl2N3Pd (551.1) requires C 54.31, H 6.02,
N 7.60%.) Conductivity (ꢀ−1 cm2 mol−1, 1.1 × 10−3 M in ace-
tonitrile) 1.8. νmax(KBr)/cm−1 ν(N–H) 3162, ν(C–H)ar 3055,
ν(C–H)al 2925–2853, ν(C=C)ph 1609, (ν(C=C)pz, ν(C=N)pz)

266
G. Aragay et al.
CHH(CH2)5CH3), 1.25 (br, 10H, NHCH2CH2(CH2)5CH3),
0.87 (br, 3H, NH(CH2)7CH3). δC (63 MHz, CD3CN, 298 K)
152.3–130.5 (Cpz, Cph), 129.8–128.7 (Cph), 107.5 (CH(pz)),
55.9 (NpzCH2CH2NH), 51.6 (NpzCH2CH2NH), 49.8 (NHCH2
(CH2)6CH3), 32.1–23.0 (NHCH2(CH2)6CH3), 14.5 (NHCH2
(CH2)6CH3). δPt (77.42 MHz, CD3CN, 298 K) −2106. m/z
(ESI+) 568 (100%, [PtCl2(dpoa)–HCl–Cl]+).
0.014 mmol) in the same solvent (0.5 mL). The mixture was
placed in the NMR tube and NaBF4 (0.0030 g, 0.027 mmol) was
added. The reaction was monitored by 1H NMR spectroscopy at
298 K during 28 h, and at 313 K during 3.5 h.
X-ray Crystallographic Study
Suitable crystals for X-ray diffraction experiments of 1, 3,
and [5](BF4)2 were obtained by crystallization from a mixture
of dichloromethane and diethyl ether (4:1). Prismatic crys-
tals were selected and mounted on an MAR345 diffractometer
with an image plate detector. Unit-cell parameters were deter-
mined from 765 (1), 1159 (3), or 697 ([5](BF4)2) reflections
(3 < θ < 31◦) and refined by least-squares method. Intensities
were collected with graphite monochromatized Mo Kα radia-
tion. 15961 (1), 18232 (3) or 17469 ([5](BF4)2) reflections were
measured in the range 2.59 ≤ θ ≤ 32.14 (1); 2.58 ≤ θ ≤ 30.00
(3); or 2.73 ≤ θ ≤ 30.84 ([5](BF4)2). 5422 (1), 5852 (3), or 5274
([5](BF4)2) of these reflections were non-equivalent by sym-
metry (Rint(on I) = 0.048 (1), 0.053 (3), or 0.048 ([5](BF4)2)).
5160 (1), 5374 (3), or 5040 ([5](BF4)2) reflections were
assumed as observed applying the condition I > 2σ(I). Lorentz-
polarization but no absorption corrections were made. The
structures were solved by direct methods, using the SHELXS-97
computer program,[29] and refined by full-matrix least-squares
method with SHELXL-97[30] using 15930 (1), 18232 (3), or
17469 ([5](BF4)2) reflections (very negative intensities were
not assumed). The function minimized was ꢂw||FO|2 − |FC|2|2,
where w = [σ2(I) + (0.0933P)2 + 2.9515P]−1 (1), w = [σ2(I) +
(0.0904P)2 + 21.1342P]−1 (3), or w = [σ2(I) + (0.08504P)2 +
3.2509P]−1 ([5](BF4)2) and P = (|FO|2 + 2|FC|2)/3. Thirteen
H atoms for [5](BF4)2 were located from a difference synthesis
and refined with an overall isotropic temperature factor. All H
atoms of 1 and 3 and seven H atoms of [5](BF4)2 were computed
and refined, using a riding model, with an isotropic tempera-
ture factor equal to 1.2 times the equivalent temperature factor
of the atom that is linked. The final R(F) factor and Rw(F2)
values, as well as the number of parameters and other details con-
cerning the refinement of the crystal structures are gathered in
Table 3.
Synthesis of Complexes [Pd(NNꢀ)2](BF4)2 (NNꢀ = dpea
[5](BF4)2; dpoa [6](BF4)2)
A solution of the corresponding ligand (0.31 mmol: dpea,
0.090 g; dpoa, 0.116 g) in dry dichloromethane (10 mL) was
added to a solution of [PdCl2(CH3CN)2] (0.041 g, 0.16 mmol)
in the same solvent (10 mL). Then, NaBF4 (0.035 g, 0.31 mmol)
was added to the solution. A white precipitate appeared instan-
taneously. The mixture was stirred for 30 min and then the
precipitate was filtered off. The solvent was reduced under
vacuum to 5 mL. Diethyl ether (3 mL) was added to induce pre-
cipitation. The resulting pale-yellow precipitate was filtered off,
washed twice with diethyl ether (5 mL), and recrystallized from
a dichloromethane/diethyl ether (4:1) mixture.
Compound [ 5](BF4)2: (0.084 g, 63%) (Found: C 53.09,
H 4.99, N 9.64. C38H42B2F8N6Pd (862.8) requires C
52.90, H 4.91, N 9.74%.) Conductivity (ꢀ−1 cm2 mol−1
,
1.0 × 10−3 M in acetonitrile) 270.4. νmax(KBr)/cm−1 ν(N–H)
3222, ν(C–H)ar 3129, ν(C–H)al 2975–2848, ν(C=C)ph 1626,
(ν(C=C)pz, ν(C=N)pz) 1552, 1481, (δ(C=C)ar, δ(C=N)ar)
1470, ν(B–F) 1083, δ(C–H)oop ph 764, δ(C–H)oop pz 698.
νmax(polyethylene)/cm−1 ν(Pd–N) 520. δH (250 MHz, CD3CN,
298 K) 7.81 (d, 2H, 3J 7.2, Hortho-3-ph), 7.61 (m, 8H, Hph),
6.32 (s, 1H, CH(pz)), 5.71 (br, 1H, NpzCH2CH2NH), 4.93
(ddd, 1H, NpzCHHCH2NH), 4.52 (ddd, 1H, NpzCHHCH2NH),
3.64 (m, 2H, NHCH2CH3), 3.36 (dddd, 1H, NpzCH2CHHNH),
2.99 (m, 2H, NHCH2CH3), 2.61 (dddd, 1H, NpzCH2CHHNH),
1.40 (t, 3H, 3J 7.2, NHCH2CH3). δC (63 MHz, CD3CN,
298 K) 148.4–127.9 (Cpz, Cph), 107.1 (CH(pz)), 51.9, 50.1
(NpzCH2CH2NH, NHCH2CH3), 48.1 (NpzCH2CH2NH), 13.0
(NHCH2CH3). m/z (ESI+) 344 (100%, [Pd(dpea)2]2+).
Compound [ 6](BF4)2: (0.086 g, 54%) (Found: C 58.02,
H 6.18, N 8.03. C50H66B2F8N6Pd (1030.4) requires C 58.24,
H 6.45, N 8.15%.) Conductivity (ꢀ−1 cm2 mol−1, 1.1 × 10−3 M
in acetonitrile) 296.3. νmax(KBr)/cm−1 ν(N–H) 3223, ν(C–
H)ar 3133–3062, ν(C–H)al 2950–2856, ν(C=C)ph 1629,
(ν(C=C)pz, ν(C=N)pz) 1551, 1483, (δ(C=C)ar, δ(C=N)ar)
1470, ν(B–F) 1083, δ(C–H)oop ph 763, δ(C–H)oop pz 698.
νmax(polyethylene)/cm−1 ν(Pd–N) 520. δH (250 MHz, CD3CN,
298 K) 7.80 (d, 2H, 3J 7.5, Hortho-3-ph), 7.60 (m, 8H, Hph), 6.32
(s, 1H, CH(pz)), 5.55 (br, 1H, NpzCH2CH2NH), 4.95 (ddd, 1H,
NpzCHHCH2NH), 4.54 (ddd, 1H, NpzCHHCH2NH), 3.36 (m,
1H, NHCHH(CH2)6CH3), 2.97 (dddd, 1H, NpzCH2CHHNH),
2.60 (m, 1H, NHCHH(CH2)6CH3), 1.89 (dddd, 1H, NpzCH2
CHHNH), 1.34 (br, 12H, NHCH2(CH2)6CH3), 0.90 (br,
3H, NHCH2CH2(CH2)5CH3). δC (63 MHz, CD3CN, 298 K)
154.1–134.3 (Cpz, Cph), 130.4–127.0 (Cph), 107.2 (CH(pz)),
57.0 (NpzCH2CH2NH), 50.1 (NHCH2(CH2)6CH3), 48.9
(NpzCH2CH2NH), 31.5–22.3 (NHCH2(CH2)6CH3), 13.4
(NHCH2(CH2)6CH3). m/z (ESI+) 428 (100%, [Pd(dpoa)2]2+).
CCDC-731090 (1), 731091 (3) and 731092 ([5](BF4)2) con-
tain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
Computational Details
Calculations were done using the Gaussian-03 program.[31]
Geometries were optimized using the M05[32] density functional
method with a LANL2DZ[33] basis set supplemented with d
polarization functions for B, C, N, O, and F.
Harmonicvibrationalfrequencieshavebeencomputedtover-
ify that the obtained structures are energy minima. Energies in
acetonitrile solution have been computed for geometries opti-
mized in the gas phase using the Conductor-like Polarizable
Continuum Model method.[34] In this case, the basis set has been
supplemented with sp diffuse functions for B, C, N, O, and F.
Kinetic Studies
Additional Experiments for Monitoring [5](BF4)2
Rate constants for the cis–trans isomerization at 298 and 313 K
were obtained from the five-point linear regressions of ln[cis]
versus t. The activation energy was obtained using theArrhenius
equation for both temperatures.
Synthesis by 1H NMR Spectroscopy
A solution of dpea ligand (0.0079 g, 0.027 mmol) in CD3CN
(0.5 mL) wasaddedto a solution of [PdCl2(CH3CN)2] (0.0035 g,

Synthesis and Characterization of New N-Alkylamino-3,5-diphenylpyrazole Ligands
267
Table 3. Crystallographic data for [MCl2(dpea)]·CH2Cl2 (M = PdII [1]·CH2Cl2; M = PtII [3]·CH2Cl2) and [5](BF4)2
1
3
[5](BF4)2
Formula
M
C20H23Cl4N3Pd
553.61
C20H23Cl4N3Pt
642.30
C38H42B2F8N6Pd
862.60
Temperature [K]
Crystal system
Space group
Unit cell dimensions
a [Å]
293(2)
Monoclinic
P21/c
293(2)
Monoclinic
P21/c
293(2)
Monoclinic
C2/c
12.420(5)
12.420(5)
21.938(7)
b [Å]
7.945(2)
7.950(5)
14.936(4)
c [Å]
β [◦]
24.040(8)
99.90(2)
24.067(11)
99.46(3)
15.023(4)
128.23(2)
Z
4
4
4
U [Å3]
2336(2)
1.574
1.262
1112
2344(2)
1.820
6.453
1240
3867(2)
1.482
0.555
1760
Dcalc [g cm−3
µ [mm−1
F(000)
]
]
Crystal size (mm)
θ range [◦]
Index range
0.2 × 0.1 × 0.1
2.59 to 32.14
−18 ≤ h ≤ 16,−11 ≤ k ≤ 9,
−32 ≤ l ≤ 32
15961/5422 [R(int) = 0.0489]
92.6
None
5422/5/259
1.204
0.09 × 0.05 × 0.05
2.58 to 30.00
−16 ≤ h ≤ 15,−10 ≤ k ≤ 10,
−32 ≤ l ≤ 32
18232/5852 [R(int) = 0.0539]
92.2
None
5852/0/254
1.089
0.2 × 0.1 × 0.1
2.73 to 30.84
−31 ≤ h ≤ 31,−20 ≤ k ≤ 20,
−20 ≤ l ≤ 20
17469/5274 [R(int) = 0.0483]
98.6
None
5274/0/342
1.172
Reflections collected/unique
Completeness to θ [%]
Absorption correction
Data/restraints/parameters
Goodness-of-fit
Final R1, wR2
R1 (all data), wR2
Extinction coefficient
Residual electron density [e Å−3
0.0565, 0.1597
0.0621, 0.1700
0.044(2)
1.343 and −1.300
0.0540, 0.1532
0.0625, 0.1761
0.045(5)
0.923 and −0.086
0.0557, 0.1470
0.0591, 0.1545
0.0261(16)
1.264 and −0.622
]
Acknowledgements
[2] (a) V. Farina, Adv. Synth. Catal. 2004, 346, 1553. doi:10.1002/
ADSC.200404178
Support by the Spanish Ministerio de Ciencia e Innovación (projects
CTQ2007–63913/BQU and CTQ2007–61704/BQU) and allowance of com-
puter resources from the Centre de Supercomputació de Catalunya super-
computing centre are gratefully acknowledged.
(b) C. A. Caputo, N. D. Jones, Dalton Trans. 2007, 4627.
doi:10.1039/B709283K
(c) V. Montoya, J. Pons, V. Branchadell, J. García-Antón,
X. Solans, M. Font-Bardia, J. Ros, Organometallics 2008, 27, 1084.
doi:10.1021/OM7009182
[3] (a) C. Che, C. Wan, K. Ho, Z. Zhou, New J. Chem. 2001, 25, 63.
doi:10.1039/B005644H
References
(b) K. M. Wong, V. W. Yam, Coord. Chem. Rev. 2007, 251, 2477.
doi:10.1016/J.CCR.2007.02.003
[4] (a) S. Moradell, J. Lorenzo, A. Rovira, M. S. Robillard, F. X. Avilés,
V. Moreno, R. Llorens, M. A. Martinez, J. Reedijk, A. Llobet,
J. Inorg. Biochem. 2003, 96, 493. doi:10.1016/S0162-0134(03)
00252-6
(b) G. Zhao, H. Lin, Curr. Med. Chem.: Anticancer Agents 2005, 5,
137. doi:10.2174/1568011053174873
[5] K. Lemma, T. Shi, L. I. Elding, Inorg. Chem. 2000, 39, 1728.
doi:10.1021/IC991351L
[1] (a) F. Abraham, M. Lagrenee, S. Sueur, B. Mernari, C. Bremard, J.
Chem. Soc., Dalton Trans. 1991, 1443. doi:10.1039/DT9910001443
(b) S. Kitagawa, M. Munakata, T. Tanimura, Inorg. Chem. 1992, 31,
1714. doi:10.1021/IC00035A036
(c) A. C. van Steenbergen, E. Bouwman, R. A. G. de Graaff,
W. L. Driessen, J. Reedijk, P. Zanello, J. Chem. Soc., Dalton Trans.
1990, 3175. doi:10.1039/DT9900003175
(d) E. S. Raper, W. Clegg, Inorg. Chim. Acta 1991, 180, 239.
doi:10.1016/S0020-1693(00)84938-5
(e) S. M. Wang, P. J. Huang, H. Chang, C. Y. Cheng, S. L. Wang,
N. C. Li, Inorg. Chim. Acta 1991, 182, 109. doi:10.1016/S0020-
1693(00)85194-4
(f) S. Trofimenko, Chem. Rev. 1972, 72, 497. doi:10.1021/
CR60279A003
[6] (a) W. L. Driessen, R. M. de Vos, A. Etz, J. Reedijk, G. C. Verschoor,
Inorg. Chim. Acta 1995, 235, 127. doi:10.1016/0020-1693(95)
90053-9
(b) J. W. F. M. Schoonhoven, W. L. Driessen, J. Reedijk, J. Chem. Soc.,
Dalton Trans. 1984, 1053. doi:10.1039/DT9840001053
(c) Y. C. M. Pennings, W. L. Driessen, J. Reedijk, Acta Crystal-
logr. Sect. C: Cryst. Struct. Commun. 1988, 44, 2095. doi:10.1107/
S0108270188008923
(g) S. Trofimenko, Prog. Inorg. Chem. 1986, 34, 115. doi:10.1002/
9780470166352.CH3
(h) S. Trofimenko, Chem. Rev. 1993, 93, 943. doi:10.1021/
CR00019A006
(d) W. L. Driessen, R. A. G. de Graaf, F. J. Parlevliet, J. Reedijk,
R. M. de Vos, Inorg. Chim. Acta 1994, 216, 43. doi:10.1016/0020-
1693(93)03707-H
(i) G. La Monica, G. A. Ardizzoia, Prog. Inorg. Chem. 1997, 46, 151.
doi:10.1002/9780470166475.CH3
(j) P. Di Bernardo, A. Melchior, R. Portanova, M. Tolazzi,
P. L. Zanonato, Coord. Chem. Rev. 2008, 252, 1270. doi:10.1016/
J.CCR.2007.12.007
[7] R. Mukherjee, Coord. Chem. Rev. 2000, 203, 151. doi:10.1016/S0010-
8545(99)00144-7

268
G. Aragay et al.
[8] (a) A. Pañella, J. Pons, J. García-Antón, X. Solans, M. Font-
(c) J. García-Antón, J. Pons, X. Solans, M. Font-Bardía, J. Ros,
Eur. J. Inorg. Chem. 2002, 3319. doi:10.1002/1099-0682(200212)
2002:12<3319::AID-EJIC3319>3.0.CO;2-L
Bardía, J. Ros, Inorg. Chim. Acta 2006, 359, 2343. doi:10.1016/
J.ICA.2005.09.069
(b) A. Pañella, J. Pons, J. García-Antón, X. Solans, M. Font-
Bardía, J. Ros, Eur. J. Inorg. Chem. 2006, 1678. doi:10.1002/EJIC.
200501056
(d) A. Boixassa, J. Pons, A. Virgili, X. Solans, M. Font-Bardía,
J. Ros, Inorg. Chim.Acta 2002, 340, 49. doi:10.1016/S0020-1693(02)
01052-6
(c) A. Pañella, J. Pons, J. García-Antón, X. Solans, M. Font-
Bardía, J. Ros, Inorg. Chim. Acta 2006, 359, 2226. doi:10.1016/
J.ICA.2005.11.046
(d) A. Pañella, J. Pons, J. García-Antón, X. Solans, M. Font-
Bardía, J. Ros, Inorg. Chim. Acta 2006, 359, 4477. doi:10.1016/
J.ICA.2006.05.046
(e) A. Boixassa, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Inorg.
Chim. Acta 2003, 346, 151. doi:10.1016/S0020-1693(02)01384-1
(f) J. García-Antón, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Eur. J.
Inorg. Chem. 2003, 3952. doi:10.1002/EJIC.200300235
(g) J. García-Antón, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Inorg.
Chim. Acta 2003, 355, 87. doi:10.1016/S0020-1693(03)00333-5
(h) A. Boixassa, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Inorg.
Chim. Acta 2004, 357, 733. doi:10.1016/J.ICA.2003.06.015
(i) J.A. Pérez, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Inorg. Chim.
Acta 2005, 358, 617. doi:10.1016/J.ICA.2004.07.064
[9] M. del Carme Castellano, J. Pons, J. García-Antón, X. Solans, M. Font-
Bardía, J. Ros, Inorg. Chim. Acta 2008, 361, 2491. doi:10.1016/
J.ICA.2008.01.016
[10] (a) G. Esquius, J. Pons, R. Yáñez, J. Ros, J. Organomet. Chem. 2001,
619, 14. doi:10.1016/S0022-328X(00)00662-8
(j) J. García-Antón, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Acta
Crystallogr. 2004, E60, m1087. doi:10.1107/S1600536804016022
[21] (a) R. P. Hughes, M. A. Meyer, M. D. Tawa, A. J. Ward, A. Williamson,
A. L. Rheingold, L. N. Zakharov, Inorg. Chem. 2004, 43, 747.
doi:10.1021/IC030251J
(b) R. Mathieu, G. Esquius, N. Lugan, J. Pons, J. Ros, Eur. J.
Inorg. Chem. 2001, 2683. doi:10.1002/1099-0682(200109)2001:10
<2683::AID-EJIC2683>3.0.CO;2-T
(c) G. Esquius, J. Pons, R. Yáñez, J. Ros, R. Mathieu, B. Donnadieu,
N. Lugan, Eur. J. Inorg. Chem. 2002, 2999. doi:10.1002/1099-0682
(200211)2002:11<2999::AID-EJIC2999>3.0.CO;2-A
[11] M. C. Castellano, J. Pons, J. García-Antón, X. Solans, M. Font-
Bardía, J. Ros, Inorg. Chim. Acta 2008, 361, 2923. doi:10.1016/
J.ICA.2008.02.059
(b) S. Dey,V. K. Jain,A. Knoedler, W. Kaim, X-Ray StructureAnalysis
Online 2004, 20, x127. doi:10.2116/ANALSCIX.20.X127
(c) K. I. Gasanov, A. S. Antsyshkina, G. G. Sadikov, N. A. Ivanova,
D. I. Mirzai, I. A. Efimenko, V. S. Sergienko, Crystallogr. Rep. 2002,
47, 603. doi:10.1134/1.1496058
[12] (a) G. Aragay, J. Pons, J. García-Antón, X. Solans, M. Font-
Bardía, J. Ros, J. Organomet. Chem. 2008, 693, 3396. doi:10.1016/
J.JORGANCHEM.2008.07.038
(d) L. Pech, Y. Bankousky, A. Kemme, E. Silina, J. Ashaks, A. Sturis,
Latvijas Kimijas Zurnals 2000, 4, 19.
(e) G. Zhao, H. Lin, P. Yu, H. Sun, S. Zhu, X. Su, Y. Chen,
J. Inorg. Biochem. 1999, 73, 145. doi:10.1016/S0162-0134(99)
00009-4
(f) E. C. Alyea, S. A. Dias, G. Ferguson, A. J. McAlees,
R. McCrindle, P. J. Roberts, J. Am. Chem. Soc. 1977, 99, 4985.
doi:10.1021/JA00457A015
(b) G. Aragay, J. Pons, J. García-Antón, A. Mendoza, G. Mendoza-
Díaz, T. Calvet, M. Font-Bardía, J. Ros, Aust. J. Chem. 2009, 62, 475.
doi:10.1071/CH08521
[13] W. G. Haanstra, W. L. Driessen, R. A. G. de Graff, G. C. Sebregts,
J. Suriano, J. Reedijk, U. Turpeinen, R. Hämäläinen, J. S. Wood,
Inorg. Chim. Acta 1991, 189, 243. doi:10.1016/S0020-1693(00)
80196-6
[14] (a) E. Pretch, T. Clerc, J. Seibl, W. Simon, Tables of Determination of
Organic Compounds. 13C-NMR, 1H-NMR, IR, MS, UV/VIS, Chemical
Laboratory Practice 1989 (Springer: Berlin).
(b) D. H. Williams, I. Fleming, Spectroscopic Methods in Organic
Chemistry 1995 (McGraw-Hill: London).
[15] (a) W. J. Geary, Coord. Chem. Rev. 1971, 7, 81. doi:10.1016/S0010-
8545(00)80009-0
[22] (a) V. Montoya, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Inorg.
Chim. Acta 2006, 359, 25. doi:10.1016/J.ICA.2005.07.047
(b) V. Montoya, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Inorg.
Chim. Acta 2005, 358, 2763. doi:10.1016/J.ICA.2005.01.028
(c) A. Boixassa, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Inorg.
Chim. Acta 2004, 357, 827. doi:10.1016/J.ICA.2003.10.001
(d) R. G. Raptis, J. P. Fackler, Jr, Acta Crystallogr. Sect. C: Cryst.
Struct. Commun. 1991, 47, 1180. doi:10.1107/S0108270190012823
(e) A. V. Khripun, S. I. Selivanov, V.Y. Kukushkin, M. Haukka, Inorg.
Chim. Acta 2006, 359, 320. doi:10.1016/J.ICA.2005.08.017
(f) K. Sakai, Y. Tomita, T. Ue, K. Goshima, M. Ohminato,
T.Tsubomura, K. Matsumoto, K. Ohmura, K. Kawakami, Inorg. Chim.
Acta 2000, 297, 64. doi:10.1016/S0020-1693(99)00287-X
(g) J. A. Broomhead, L. M. Rendina, M. Sterns, Inorg. Chem. 1992,
31, 1880. doi:10.1021/IC00036A030
(b) L. K. Thompson, F. L. Lee, E. J. Gabe, Inorg. Chem. 1988, 27, 39.
doi:10.1021/IC00274A010
[16] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordi-
nation Compounds 1986 (Wiley & Sons: New York, NY).
[17] (a) L. Scuzová, Z. Trávnicek, M. Zatloukal, I. Popa, Bioorg. Med.
Chem. 2006, 14, 479. doi:10.1016/J.BMC.2005.08.033
(b) I. Lakomska, E. Szlyk, J. Sitkowski, L. Kozerski, J. Wietrzyk,
M. Pelczynska, A. Nasulewicz, A. Opolski, J. Inorg. Biochem. 2004,
98, 167. doi:10.1016/J.JINORGBIO.2003.09.001
(h) M. A. Cinellu, S. Stoccoro, G. Minghetti, A. L. Bandina,
G. Banditelli, B. Bovio, J. Organomet. Chem. 1989, 372, 311.
doi:10.1016/0022-328X(89)87104-9
(c) Z. Trávnicˇek, M. Maloñ, M. Zatloukal, K. Dolezal, K. Strnad,
J. Marek, J. Inorg. Biochem. 2003, 94, 307. doi:10.1016/S0162-
0134(03)00051-5
[23] (a) A. de León, J. Pons, J. García-Antón, X. Solans, M. Font-
Bardía, J. Ros, Polyhedron 2007, 26, 2498. doi:10.1016/J.POLY.2006.
12.034
(d) P. Tsiveriotis, N. Hadjiliadis, G. Slavropoulos, Inorg. Chim. Acta
1997, 261, 83. doi:10.1016/S0020-1693(97)05454-6
(e) C. Tessier, F. D. Rochon, Inorg. Chim. Acta 1999, 295, 25.
doi:10.1016/S0020-1693(99)00303-5
(f) P. S. Pregosin, Coord. Chem. Rev. 1982, 44, 247. doi:10.1016/
S0010-8545(00)80523-8
(b) A. de León, J. Pons, J. García-Antón, X. Solans, M. Font-
Bardía, J. Ros, Inorg. Chim. Acta 2007, 360, 2071. doi:10.1016/
J.ICA.2006.10.035
[24] (a) M. Goto, H. Tsutsui, S. Matsuda, Y. Tanaka, N. Tsuruda,
H. Kurosaki, Chem. Pharm. Bull. 2004, 52, 47. doi:10.1248/
CPB.52.47
[18] A. deLeón, J. Pons, J. García-Antón, X. Solans, M. Font-Bardía, J. Ros,
Polyhedron 2007, 26, 2921. doi:10.1016/J.POLY.2007.01.051
[19] F. A. Allen, Acta Crystallogr. 2002, B58, 380. doi:10.1107/
S0108768102003890
[20] (a) V. Montoya, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Inorg.
Chim. Acta 2005, 358, 2312. doi:10.1016/J.ICA.2004.12.060
(b) J. García-Antón, J. Pons, X. Solans, M. Font-Bardía, J. Ros, Eur.
J. Inorg. Chem. 2003, 2992. doi:10.1002/EJIC.200300035
(b) C. J. L. Lock, P. Pilon, Acta Crystallogr. Sect B: Struct. Cryst. and
Cryst. Chem. 1981, 37, 45. doi:10.1107/S0567740881002161
(c) T. Tsubomura, S. Yano, K. Kobayashi, T. Sakurai, S. Yoshikawa, J.
Chem. Soc. Chem. Commun. 1986, 459. doi:10.1039/C39860000459
(d) M. Crespo, M. Font-Bardía, J. Granell, M. Martinez, X. Solans,
Dalton Trans. 2003, 3763. doi:10.1039/B306243K
(e) V. P. Munk, R. R. Fenton, T. W. Hambley, Polyhedron 1999, 18,
1039. doi:10.1016/S0277-5387(98)00390-8

Synthesis and Characterization of New N-Alkylamino-3,5-diphenylpyrazole Ligands
269
[25] (a) C. Janiak, Dalton Trans. 2000, 3885. doi:10.1039/B003010O
(b)S. Muñoz, J. Pons, X. Solans, M. Font-Bardia, J. Ros, J. Organomet.
Chem. 2008, 693, 2132. doi:10.1016/J.JORGANCHEM.2008.03.010
[26] P. H. M. Budzelaar, gNMR – version 4.0. 1997 (IvorySoft, Cherwell
Scientific: Oxford, UK).
[27] S. Komiya, Synthesis of Organometallic Compounds: a Practice
Guide 1997 (John Wiley & Sons: New York, NY).
[28] F. P. Fanizzi, F. P. Intini, L. Maresca, G. Natile, J. Chem. Soc., Dalton
Trans. 1990, 199. doi:10.1039/DT9900000199
K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas,
D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V.
Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D.
J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong,
C. Gonzalez, J. A. Pople, Gaussian 03, Revision E.01 2004 (Gaussian,
Inc.: Wallingford, CT). http://www.gaussian.com.
[29] G. M. Sheldrick, SHELXS-97, Program for Crystal Structure Deter-
mination 1997 (University of Göttingen: Germany).
[32] Y. Zhao, N. E. Schultz, D. G. Truhlar, J. Chem. Phys. 2005, 123,
161103/1.
[30] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure Refine-
ment 1997 (University of Göttingen: Germany).
[33] (a) P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 270.
doi:10.1063/1.448799
[31] M. J. Frisch, G. W.Trucks, H. B. Schlegel, G. E. Scuseria, M.A. Robb,
J. R. Cheeseman, J. J. A. Montgomery, T. Vreven, K. N. Kudin,
J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone,
B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson,
H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene,
X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken,
C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala,
(b) T. H. Dunning, P. J. Hay, Modern Theoretical Chemistry 1977,
Vol. 3 (Plenum Press: New York, NY).
[34] (a) A. Klamt, G. Schüürmann, J. Chem. Soc. Perkin Trans. 2: Phys.
Org. Chem. 1993, 799. doi:10.1039/P29930000799
(b) V. Barone, M. Cossi, J. Phys. Chem. A 1998, 102, 1995.
doi:10.1021/JP9716997
(c) M. Cossi, N. Rega, G. Scalmani, V. Barone, J. Comput. Chem.
2003, 24, 669. doi:10.1002/JCC.10189