Exploring the coordination chemistry and reactivity of hemilabile N-alkylaminopyrazole ligands towards Pd(II)

Article abstract of DOI:10.1016/j.ica.2006.05.046

Reaction of the N-alkylaminopyrazole (NN′N) ligands bis[(3,5-dimethyl-1-pyrazolyl)methyl]ethylamine (bdmae) and bis[(3,5-dimethyl-1-pyrazolyl)methyl]isopropylamine (bdmai) with [PdCl₂(CH₃CN)₂] in a 1:1 M/L ratio in CH₂Cl₂ produces cis-[PdCl₂(NN′N)] (NN′N = bdmae (1), bdmai (2)). The solid state structure of complex 1 was determined by X-ray diffraction studies. The bdmae ligand is coordinated through the two N_pz atoms to the metal atom, which completes its coordination with two chlorine atoms in a cis disposition. Treatment of the corresponding ligand with [PdCl₂(CH₃CN)₂] in 1:1 M/L ratio in the presence of AgBF₄ and metathesis with NaBPh₄ in CH₂Cl₂/CH₃OH (3:1) gave [PdCl(bdmae)](BPh₄) (3), and in the presence of NaBPh₄ in CH₂Cl₂/CH₃CN (3:1) gave [PdCl(bdmai)](BPh₄) (4). Complexes 1 and 2 were again obtained when complexes 3 and 4 were heated under reflux in a solution of Et₄NCl in acetonitrile. These Pd(II) compounds were characterised by elemental analyses, conductivity measurements, IR, ¹H and ¹³C{¹H} NMR, HMQC and NOESY spectroscopies. The NMR studies of the complexes prove the rigid conformation of the ligands when they are complexed.

Full text of DOI:10.1016/j.ica.2006.05.046

Inorganica Chimica Acta 359 (2006) 4477–4482
www.elsevier.com/locate/ica
Exploring the coordination chemistry and reactivity of hemilabile
N-alkylaminopyrazole ligands towards Pd(II)
a
a,
a
b
*
´
´
Anna Panella , Josefina Pons , Jordi Garcıa-Anton , Xavier Solans ,
˜
b
a,
*
`
Merce Font-Bardia , Josep Ros
a
` `
Departament de Quı´mica, Unitat de Quı´mica Inorganica, Universitat Autonoma de Barcelona, 08193-Bellaterra-Cerdanyola, Barcelona, Spain
b
` `
´
Cristal.lografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Martı i Franques s/n, 08028-Barcelona, Spain
Received 2 May 2006; accepted 23 May 2006
Available online 25 July 2006
Abstract
Reaction of the N-alkylaminopyrazole (NN0N) ligands bis[(3,5-dimethyl-1-pyrazolyl)methyl]ethylamine (bdmae) and bis[(3,5-
dimethyl-1-pyrazolyl)methyl]isopropylamine (bdmai) with [PdCl2(CH3CN)2] in a 1:1 M/L ratio in CH2Cl2 produces cis-[PdCl2(NN0N)]
(NN0N = bdmae (1), bdmai (2)). The solid state structure of complex 1 was determined by X-ray diffraction studies. The bdmae ligand
is coordinated through the two Npz atoms to the metal atom, which completes its coordination with two chlorine atoms in a cis
disposition.
Treatment of the corresponding ligand with [PdCl2(CH3CN)2] in 1:1 M/L ratio in the presence of AgBF4 and metathesis with NaBPh4
in CH2Cl2/CH3OH (3:1) gave [PdCl(bdmae)](BPh4) (3), and in the presence of NaBPh4 in CH2Cl2/CH3CN (3:1) gave
[PdCl(bdmai)](BPh4) (4). Complexes 1 and 2 were again obtained when complexes 3 and 4 were heated under reflux in a solution of
Et4NCl in acetonitrile. These Pd(II) compounds were characterised by elemental analyses, conductivity measurements, IR, 1H and
13C{1H} NMR, HMQC and NOESY spectroscopies. The NMR studies of the complexes prove the rigid conformation of the ligands
when they are complexed.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Palladium(II); N-alkylaminopyrazole ligands; Hemilabile ligands; Pyrazole complexes; Crystal structures
1. Introduction
[M(bdmae)2](ClO4)2 (M = Co(II), Ni(II)) [2], [CuI(bdmae)]
[3], [CuX2(ddae)] (X = Clꢀ, NO ꢀ) [4] (bdmae = bis-
3
The N1-substituted pyrazolic ligands have been exten-
sively investigated in our laboratory in recent years. In par-
ticular, we have reported the synthesis, spectroscopic
studies and structural characterisation of new Rh(I) and
Pd(II) compounds with N-alkylaminopyrazoles.
The synthesis of bidentate-(NN0) and tridentate-(NN0N)
pyrazole ligands was developed by Driessen et al., who
described the synthesis and characterisation of the com-
plexes [MX2(deae)] (M = Co(II), Zn(II); X = Clꢀ, NCSꢀ)
[1], [NiCl2(deae)]2 [1], [CuCl3(deaeH)] [1] (deae = 1-[2-(eth-
ylamino)ethyl]-3,5-dimethylpyrazole), [MX2(bdmae)] (M =
Co(II), Ni(II), Cu(II), Zn(II); X = Clꢀ, Brꢀ, NO3ꢀ) [2],
[(3,5-dimethyl-1-pyrazolyl)methyl]ethylamine), and [Cu-
(NO3)(H2O)(ddae)](NO3)
(ddae = bis[2-(3,5-dimethyl-1-
pyrazolyl)ethyl]ethylamine) [4].
We have previously reported the reactivity of bidentate-
(NN0) ligands deae, 1-[2-(ethylamino)isopropyl]-3,5-dim-
ethylpyrazole (deai), and 1-[2-(ethylamino)tert-butyl]-3,5-
dimethylpyrazole (deat) with Rh(I) and Pd(II), obtaining
complexes with general formula [Rh2Cl2(COD)2(NN0)]
(NN0 = deae, deai) [5], [Rh(COD)(deae)](BF4) [6],
[Rh2(CO)2(deae) [6] [PdCl2(deae)] [7], and [PdCl(deae)]
(BF4) [8].
Moreover, with the tridentate-(NN0N) ligands, bdmae
and bis[(3,5-dimethyl-1-pyrazolyl)methyl]isopropylamine
(bdmai), we have reported the reactivity with Rh(I), obtain-
ing the complexes [Rh2Cl2(COD)2(NN0N)](NN0N = bdmae,
*
Corresponding authors. Fax: +34 93 581 31 01 (J. Pons).
E-mail address: Josefina.Pons@uab.es (J. Pons).
0020-1693/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.05.046

4478
A. Pan˜ella et al. / Inorganica Chimica Acta 359 (2006) 4477–4482
bdmai) [5], [Rh(COD)(bdmae)](BF4) [9], [Rh(CO)2-
(bdmae)](BF4) [9], [Rh(CO)2(bdmae)](BPh4) [9], [Rh(CO)-
(bdmae)](BF4) [9], and [Rh(CO)(bdmae)](BPh4) [9].
In a previous work, we have synthesised the new Pd(II)
complexes [PdCl2(NN0N)], [PdCl(NN0N)]Cl, and [PdCl-
(NN0N)](BF4) [10] (NN0N = ddae, bis[2-(3,5-dimethyl-1-
pyrazolyl)ethyl]isopropylamine (ddai), and bis[2-(3,5-
dimethyl-1-pyrazolyl)ethyl]tert-butylamine (ddat)). These
ligands show bidentate coordination (NN0) and tridentate
coordination (NN0N) depending on the solvent. In these
complexes, the hemilabile centre of the ligands is the nitro-
gen atom of the amine function.
This paper extends this work to the reactivity of a new
family of NN0N ligands with Pd(II). We report the reactiv-
ity of the ligands bdmae, and bdmai with Pd(II). These
ligands contain two pyrazole nitrogens and one amine
nitrogen as potential N-donor atoms.
[PdCl2(CH3CN)2] in 10 ml of dry CH2Cl2. After the mix-
ture had been stirred for 12 h, most of the solvent was
removed under vacuum. Diethyl ether (5 ml) was then
added dropwise to induce precipitation. The yellow orange
solids were filtered off, washed twice with 5 ml of diethyl
ether, and recrystallised in a dichloromethane/diethyl ether
(1:1) mixture.
Compound 1: Yield: 64%. Anal. Calc. for
C14H23Cl2N5Pd (438.3): C, 38.33; H, 5.25; N, 15.97.
Foꢀu1nd: C, 39.06; H, 5.63; N, 15.60%. Conductivity
(X cm2 molꢀ1
,
9.82 · 10ꢀ4 M in CH3CN): 53;
(Xꢀ1 cm2 molꢀ1, 8.92 · 10ꢀ4 M in CH3OH): 10. IR: (KBr,
cmꢀ1) 3131, 3045, m(C–H)ar, 2977, 2937 m(C–H)al, 1554
(m(C@C), m(C@N))ar, 1460, 1419 (d(C@C), d(C@N))ar,
1093 d(C–H)ip, 800 d(C–H)oop; (polyethylene, cmꢀ1) 476,
1
443 m(Pd–N), 338, 322 m(Pd–Cl). H NMR (CD3CN solu-
tion, 250 MHz) d: 6.78 [d, 2H, J = 15.5 Hz, NpzCHHN],
2
5.85 [s, 2H, CH(pz)], 5.32 [d, 2H, 2J = 15.5 Hz,
NpzCHHN], 2.74 [q, 2H, 3J = 7.2 Hz, NCH2CH3], 2.63
[s, 6H, CH3(pz)], 2.24 [s, 6H, CH3(pz)], 0.68 [t, 3H,
3J = 7.2 Hz, NCH2CH3]. 13C NMR (CD3CN solution,
63 MHz) d: 151.0 [CCH3], 144.4 [CCH3], 108.1 [CH(pz)],
68.8 [NpzCH2N], 44.2 [NCH2CH3], 14.9 [NCH2CH3], 12.7
[CCH3], 11.6 [CCH3].
2. Experimental
2.1. General details
Standard Schlenk techniques were employed throughout
the synthesis using a double manifold vacuum line with
high purity dry nitrogen. All reagents were commercial
grade materials and were used without further purification.
All solvents were dried and distilled by standard methods.
The elemental analyses (C, H, N) were carried out by the
staff of the Chemical Analyses Service of the Universitat
Compound 2: Yield: 57%. Anal. Calc. for C15H25Cl2N5Pd
(452.3): C, 39.79; H, 5.53; N, 15.48. Found: C,ꢀ410.33; H,
5.43; N, 15.52%. Conductivity (Xꢀ1 cm2 mol , 8.11 ·
10ꢀ4 M in CH3CN): 36; (Xꢀ1 cm2 molꢀ1, 9.03 · 10ꢀ4 M in
CH3OH): 24. IR: (KBr, cmꢀ1) 3124, 3084, m(C–H)ar, 2971,
2938 m(C-H)al, 1555 (m(C@C), m(C@N))ar, 1462, 1417
(d(C@C), d(C@N))ar, 1083 d(C–H)ip, 807 d(C–H)oop; (poly-
`
Autonoma de Barcelona on a Carlo Erba CHNS EA-
1108 instrument. The conductivity measurements were
performed at room temperature (r.t.) in 10ꢀ3 M in CH3CN
or CH3OH employing a Crison, micro CM 2200 conduc-
timeter. The infrared spectra were run on a Perkin–Elmer
FT spectrophotometer series 2000 cmꢀ1 as KBr pellets or
polyethylene films in the range 4000–100 cmꢀ1 under a
nitrogen atmosphere. The 1H NMR, 13C{1H} NMR,
HMQC and NOESY spectra were run on a NMR-FT
Bruker 250 MHz instrument. 1H NMR and 13C{1H}
NMR chemical shifts (d) were determined relative to inter-
nal TMS and are given in ppm. The electrospray mass
spectra were obtained on an Esquire 3000 ion trap mass
spectrometer from Bruker Daltonics (ESI-IT).
1
ethylene, cmꢀ1) 472 , 448 m(Pd–N), 337, 320 m(Pd–Cl). H
NMR (CD3CN solution, 250 MHz) d: 6.75 [d, 2H,
2J = 15.4 Hz, NpzCHHN], 5.87 [s, 2H, CH(pz)], 5.41 [d,
2
3
2H, J = 15.4 Hz, NpzCHHN], 3.28 [sp, 1H, J = 6.8 Hz,
NCH(CH3)2], 2.65 [s, 6H, CH3(pz)], 2.27 [s, 6H, CH3(pz)],
0.78 [d, 6H, 3J = 6.8 Hz, NCH(CH3)2]. 13C NMR (CD3CN
solution, 63 MHz) d: 151.3 [CCH3], 144.1 [CCH3], 108.4
[CH(pz)], 68.4 [NpzCH2N], 53.2 [NCH(CH3)2], 20.2
[NCH(CH3)2], 15.2 [CCH3], 11.6 [CCH3].
2.2.2. Synthesis of the complexes [PdCl(NN0N)](BPh4)
(NN0N = bdmae (3), bdmai (4))
2.2.2.1. Synthesis of the complex [PdCl(bdmae)](BPh4)
The synthesis of bis[(3,5-dimethyl-1-pyrazolyl)methyl]-
1-methylethylamine (bdmae) and bis[(3,5-dimethyl-1-pyraz-
(3). To
a
solution of 0.27 mmol (0.070 g) of
[PdCl2(CH3CN)2] in 10 ml of dry CH2Cl2, 0.27 mmol
(0.052 g) of AgBF4 in 5 ml of CH3OH and 0.27 mmol
(0.070 g) of the ligand bdmae in 5 ml of dry CH2Cl2 were
added. The mixture was stirred at r.t. and light-protected
for 40 min. The yellow solution was then filtered through
a pad of Celite. The solution was stirred for 6 h and con-
centrated on a vacuum line to one-fifth of the initial vol-
ume. 0.27 mmol (0.092 g) of NaBPh4 was added; then the
solution was cooled down to 0ꢁ and diethyl ether (5 ml)
was then added dropwise to induce precipitation. The yel-
low solid was filtered off, washed twice with 5 ml of diethyl
ether and dried under vacuum.
olyl)methyl]-1-methylisopropylamine
(bdmai),
were
prepared according to the published methods [5,11,12].
The samples of [PdCl2(CH3CN)2] [13] were prepared as
described in the literature.
2.2. Synthesis of the complexes
2.2.1. Synthesis of the complexes [PdCl2(NN0N)]
(NN0N = bdmae (1), bdmai (2))
A solution of 0.27 mmol of the corresponding ligand
(bdmae: 0.070 g; and bdmai: 0.074 g) in 5 ml of dry CH2Cl2
was added to a solution of 0.27 mmol (0.070 g) of

A. Pan˜ella et al. / Inorganica Chimica Acta 359 (2006) 4477–4482
4479
Compound 3: Yield: 34%. Anal. Calc. for
C38H43BClN5Pd (721.7): C, 63.18; H, 5.96; N, 9.76. Found:
A prismatic crystal was selected and mounted on a
MAR345 diffractometer with a image plate detector.
Unit-cell parameters were determined from 9384 reflec-
tions (3 < h < 31ꢁ) and refined by least-squares method.
Intensities were collected with graphite monochromatized
Mo Ka radiation. 9945 reflections were measured in the
range 2.25 6 h 6 30ꢁ. 5628 of which were non-equivalent
by symmetry (Rint(on I) = 0.023). 5390 reflections were
assumed as observed applying the condition I > 2r(I).
Lorentz-polarization but no absorption corrections were
made.
C, 62.82; H, 5.87; N, 9.96%. Conductivity (Xꢀ1 cm2 molꢀ1
4.16 · 10ꢀ4 M in CH3CN): 146; (Xꢀ1 cm2 molꢀ1
,
,
9.18 · 10ꢀ4 M in CH3OH): 100. IR: (KBr, cmꢀ1) 3054,
3035 m(C–H)ar, 2983 m(C–H)al, 1579, 1555 (m(C@C),
m(C@N))ar, 1467, 1425 (d(C@C), d(C@N))ar, 1067 d(C–
H)ip, 802 d(C–H)oop; 612 (B–C); (polyethylene, cmꢀ1) 480,
411 m(Pd–N), 343 m(Pd–Cl). MS (%) = 403 (100%)
[PdCl(bdmae)]+. 1H NMR (acetone-d6 solution,
250 MHz) d: 6.04 [s, 2H, CH(pz)], 5.50 [d, 2H,
2J = 11.7 Hz, NpzCHHN], 5.03 [d, 2H, 2J = 11.7 Hz,
The structure was solved by Direct methods, using
SHELXS computer program, and refined by full-matrix
least-squares method with SHELX97 computer programs
[14] using 9945 reflections (very negative intensities were
3
NpzCHHN], 2.98 [q, 2H, J = 7.3 Hz, NCH2CH3], 2.32 [s,
3
12H, CH3(pz)], 1.04 [t, 3H, J = 7.3 Hz, NCH2CH3]. 13C
NMR (acetone-d6 solution, 63 MHz) d: 155.6 [CCH3],
144.4 [CCH3], 108.6 [CH(pz)], 70.1 [NpzCH2N], 54.6
[NCH2CH3], 13.2 [NCH2CH3], 11.7 [CCH3], 11.3 [CCH3].
not
assumed).
The
function
minimised
was
P
2
2 2
wiFojj ꢀ jFcj j where x = [r2(I) + (0.0628P)2 + 2.7870
P]ꢀ1, and P = (jFoj + 2jFcj )/3. Twenty-two H atoms were
located from a difference synthesis and refined with overall
isotropic temperature factor and three H atoms were
located from a difference synthesis and refined, using a rid-
ing model, with an isotropic temperature factor equal to
1.2 the equivalent temperature factor of the atom which
are linked. The final R(F) factor and Rw(F2) values as well
as the number of parameters and other details concerning
the refinement of the crystal structure are gathered in
Table 1.
2
2
2.2.2.2. Synthesis of the complex [PdCl(bdmai)](BPh4)
(4). To
a
solution of 0.27 mmol (0.070 g) of
[PdCl2(CH3CN)2] and 0.27 mmol (0.074 g) of the ligand
bdmai in 15 ml of dry CH2Cl2 and with continuous stirring,
0.27 mmol (0.10 g) of NaBPh4 solved in 5 ml of dry
CH3CN were added. After 5 min stirring, the solution
becomes turbid because of the formation of NaCl. The
solution is stirred for 1 h, and then, it is filtered through
a pad of Celite. The resultant yellow solution is concen-
trated under vacuum to 4 ml and cooled down to 0ꢁC.
Diethyl ether (5 ml) is then added dropwise with continu-
ous stirring until a pale yellow precipitate is observed.
Finally, the precipitate is filtered off, washed twice with
4 ml of cool dry diethyl ether and dried under vacuum.
Compound 4: Yield: 61%. Anal. Calc. for
C39H45BClN5Pd (735.7): C, 63.61; H, 6.12; N, 9.51. Found:
Table 1
Crystallographic data for [PdCl2(bdmae)] Æ CH2Cl2 (1)
Formula
M
C15H27Cl4N5Pd
525.60
Temperature (K)
Crystal system
Space group
Unit cell dimensions
293(2)
monoclinic
P21/n
C, 63.43; H, 5.98; N, 9.37 %. Conductivity (Xꢀ1 cm2 molꢀ1
5.20 · 10ꢀ4 M in CH3CN): 131; (Xꢀ1 cm2 molꢀ1
,
,
3.12 · 10ꢀ4 M in CH3OH): 98. IR: (KBr, cmꢀ1) 3054,
3035 m(C–H)ar, 2982 m(C–H)al, 1579, 1557 (m(C@C),
m(C@N))ar, 1466, 1425 (d(C@C), d(C@N))ar, 1065 d(C–
˚
a (A)
8.5350(10)
18.1020(10)
13.4940(10)
90
91.280(10)
90
2084.3(3)
4
1.669
˚
b (A)
˚
c (A)
H)ip, 802 d(C–H)oop, 612 m(B–C); (polyethylene, cmꢀ1
)
a (ꢁ)
b (ꢁ)
c (ꢁ)
468, 419 m(Pd–N), 352 m(Pd–Cl). MS (%) = 417 (100%)
[PdCl(bdmai)]+. 1H NMR (CD3CN solution, 250 MHz)
d: 6.05 [s, 2H, CH(pz)], 5.22 [d, 2H, 2J = 12.5 Hz,
3
˚
U (A )
Z
2
Dcalc (g cmꢀ3
l (mmꢀ1
F(000)
)
NpzCHHN], 4.78 [d, 2H, J = 12.5 Hz, NpzCHHN], 3.42
3
)
1.412
1056
[sp, 1H, J = 7.6 Hz, NCH(CH3)], 2.43 [s, 6H, CH3(pz)],
2.32 [s, 6H, CH3(pz)], 1.15 [d, 6H, 3J = 7.6 Hz,
NCH(CH3)]. 13C NMR (CD3CN solution, 63 MHz) d:
165.1 [CCH3], 144.8 [CCH3], 108.9 [CH(pz)], 68.0
[NpzCH2N], 59.9 [NCH(CH3)2], 19.1 [NCH(CH3)2], 14.0
[CCH3], 12.6 [CCH3].
Crystal size
h Range (ꢁ)
Index range
0.2 · 0.1 · 0.1
2.25–30.00
0 6 h 6 12,
ꢀ25 6 k 6 25,
ꢀ18 6 l 6 18
9945/5628 (0.02381)
92.7%
none
5628/0/242
1.344
Reflections collected/unique (Rint
Completeness to h = 30ꢁ
Absorption correction
Data/restraints/parameters
Goodness-of-fit
)
2.3. X-ray crystal structure for compound
cis-[PdCl2(bdmae)] Æ CH2Cl2 (1)
Final R1, xR2
R1 (all data), xR2
Largest difference in peak and hole (e A
0.0478 and 0.1420
0.0511 and 0.1476
0.977 and ꢀ0.987
Suitable crystals for X-ray diffraction of compound cis-
[PdCl2(bdmae)] Æ CH2Cl2 were obtained through crystalli-
sation from ethanol/dichloromethane (1:1).
ꢀ3
˚
)

4480
A. Pan˜ella et al. / Inorganica Chimica Acta 359 (2006) 4477–4482
3. Results and discussion
of compounds 1 and 2 are consistent with the formula
[PdCl2(NN0N)] and those for compounds 3 and 4 with
[PdCl(NN0N)](BPh4).
3.1. Synthesis and spectroscopic properties
Complexes 3 and 4 decompose when they are left in
solution (for this reason, the obtaining of suitable mono-
crystals for X-ray diffraction was not possible). This kind
of instability had already been observed in a preceding
paper for NSSN ligands 1,6-bis(3,5-dimethyl-1-pyrazolyl)-
2,5-dithiahexane (bddh) and 1,7-bis(3,5-dimethyl-1-pyraz-
olyl)-2,6-dithiaheptane (bddhp), which are not able to tetra-
coordinate Pd(II) centres. In this case, the
tetracoordination of bddh and bddhp ligands would involve
the formation of unstable five-membered PdNNCS rings
similar to the PdNNCN rings obtained for 3 and 4
[15,16] and presented in this paper. To confirm the exis-
tence of 3 and 4 complexes, electrospray mass spectra were
recorded. The positive ionisation spectrum of 3 and 4 when
measured gave peaks with m/z values of 403 and 417,
respectively (molecular peak of the cation).
The N-alkylaminopyrazole ligands (bis[(3,5-dimethyl-1-
pyrazolyl)methyl]ethylamine (bdmae), and bis[(3,5-
dimethyl-1-pyrazolyl)methyl]isopropylamine
(bdmai))
(Scheme 1) used for the synthesis of the Pd(II) complexes
were prepared according to the literature procedures
[5,11,12].
Complexes [PdCl2(NN0N)] (NN0N = (bdmae) (1), and
(bdmai) (2)) were obtained by treatment of the correspond-
ing ligand with [PdCl2(CH3CN)2] in a 1:1 M/L ratio in
CH2Cl2. Complexes [PdCl(NN0N)](BPh4) (NN0N =
(bdmae) (3), and (bdmai) (4)) were obtained by reaction
of the corresponding ligand with [PdCl2(CH3CN)2] in a
1:1 M/L ratio in the presence of AgBF4 and metathesis
with NaBPh4 in CH2Cl2/CH3OH (3:1) for complex 3,
and in the presence of NaBPh4 in CH2Cl2/CH3CN (3:1)
for complex 4. When complexes 3 and 4 were heated under
reflux in a solution of Et4NCl in CH3CN for 24 h, com-
plexes 1 and 2 were again obtained. The elemental analyses
The conductivity values in CH3CN and CH3OH for
compounds 1 and 2, are in agreement with non-electrolyte
natures. The conductivity values in CH3CN and CH3OH
R = Et (bdmae)
R = iPr (bdmai)
N
N
N
N
N
R
[PdCl2(CH3CN)2]
R
N
H6b
H6b
H6a
H6a
R = Et
1) AgBF4
+
N
2) NaBPh4
N
N
N
N
-
N
N
N
Pd
Cl
N
BPh4
NEt4Cl
Pd
Cl
Cl
[3]BPh4
R = Et [1]
R = iPr [2]
R = iPr
NaBPh4
NEt4Cl
H6b
H6a
+
N
N
N
N
-
BPh4
N
Pd
Cl
[4]BPh4
Scheme 1.

A. Pan˜ella et al. / Inorganica Chimica Acta 359 (2006) 4477–4482
4481
for compounds 3 and 4 are in agreement with 1:1 electro-
lytes. The reported values for 10ꢀ3 M solutions of non-elec-
trolyte complexes are lower than 120 Xꢀ1 cm2 molꢀ1 or
80 Xꢀ1 cm2 molꢀ1 in CH3CN or CH3OH, respectively,
while the range of conductivity values for 10ꢀ3 M solutions
of 1:1 electrolyte compounds in CH3OH is between 80 and
115 Xꢀ1 cm2 molꢀ1 and in CH3CN between 120 and
160 Xꢀ1 cm2 molꢀ1 [17,18].
1H NMR spectra of 1–4 at room temperature, the methy-
lene hydrogens appear as narrow AB spectra. The two pro-
tons of the CH2 group in the Npz-CH2-Namine chain are
diastereotopic thus giving rise to two groups of signals,
each one attributable to a single hydrogen atom. This hap-
pens because of the rigid conformation of the ligand once it
has been complexed. In this way, each group of signals can
be assigned as a doublet for H6 and H7 (Scheme 1).
The IR spectra of complexes 1–4 in the range 4000–
400 cmꢀ1 show that the ligands are coordinated to Pd(II).
The m(C@C), m(C@N) and d(C–H)oop bands of the pyraz-
olic ligands increase its frequency when they are part of
the complexes [5,11,12]. The IR spectra of 3 and 4 present
bands that were assigned to m(B–C) at 612 cmꢀ1 [19].
The IR spectra of complexes 1–4 in the region 600–
100 cmꢀ1 were also studied. The presence of bands between
480 and 411 cmꢀ1 assigned to m(Pd–N) confirms the coordi-
nation of the ligand to the metallic atom. The complexes 1
and 2 display two well-defined m(Pd–Cl) bands at 338,
322 cmꢀ1 (1) and 337, 320 cmꢀ1 (2). These bands clearly
indicate that the chlorine atoms are coordinated to the
Pd(II) in a cis disposition. In compounds 3 and 4 only
one band attributable to m(Pd–Cl) (343 cmꢀ1 (3),
340 cmꢀ1 (4)) was observed [20].
In the NOESY spectra of the compounds 1 and 2 it can
be seen that the methyl(pyrazole) group at d = 2.63 (1), and
2.65 (2) ppm shows NOE interaction with the doublet at
d = 5.32 (1), and 5.41 (2) ppm but not with the one at
d = 6.78 (1), and 6.75 (2) ppm. This information leads us
to assign H-6a to the doublet at 5.32 (1), and 5.41 (2)
ppm, and H-6b to the one at d = 6.78 (1), and 6.75 (2)
ppm, because according to the X-ray crystal structure of
1, H-6a has the shortest distance to the methyl(pyrazole)
˚
group at 2.63 ppm (2.895 A) (Fig. 1).
3.2. Crystal and molecular structure of complex 1
The crystal structure of complex 1 consists of mono-
meric cis-[PdCl2(bdmae)] molecules and solvent molecules
(CH2Cl2) linked by van der Waals forces (Fig. 1).
1H NMR, 13C{1H} NMR, HMQC, and NOESY NMR
spectra of compounds 1 and 2 were recorded in CD3CN
and for compounds 3 and 4 in acetone-d6 and CD3CN,
respectively, and they show the signals of the ligands
(bdmae, bdmai). The NMR spectroscopic data are reported
in the Section 2.
The palladium centre has a square planar geometry
(with a slight tetrahedral distortion, in which the metallic
atom lies 0.004 A out of the coordination plane).
The environment consists of two chlorine atoms in cis
disposition to the metal and two nitrogen atoms of the pyr-
azolic rings. Bdmae behaves as a bidentate ligand and only
uses two of its three donor nitrogen atoms, forming a
eight-membered metallocycle. The cis-PdCl2(Npz)2 core
˚
No significant differences between 13C{1H} NMR spec-
tra of free and coordinated ligands were observed. In the
Fig. 1. ORTEP drawing of [PdCl2(bdmae)] (1), showing all non-hydrogen atoms and the atom-numbering scheme; 50% probability amplitude displacement
ellipsoids are shown.

4482
A. Pan˜ella et al. / Inorganica Chimica Acta 359 (2006) 4477–4482
Table 2
[2] J.W.F.M. Schoonhoven, W.L. Driessen, J. Reedijk, J. Chem. Soc.,
Dalton Trans. (1984) 1053.
[3] Y.C.M. Pennings, W.L. Driessen, J. Reedijk, Acta Crystallogr. C44
(1988) 2095.
[4] W.L. Driessen, R.A.G. de Graaf, F.J. Parlevliet, J. Reedijk, R.M. de
Vos, Inorg. Chim. Acta 216 (1994) 43.
˚
Selected bond lengths (A) and bond angles (ꢁ) for [PdCl2(bdmae)] Æ CH2Cl2
(1)
Pd–N(1)
Pd–Cl(1)
2.012(3)
2.2876(10)
Pd–N(4)
Pd–Cl(2)
2.012(3)
2.2917(10)
N(1)–Pd–N(4)
N(1)–Pd–Cl(1)
N(1)–Pd–Cl(2)
88.45(13)
89.36(10)
177.35(9)
N(4)–Pd–Cl(1)
N(4)–Pd–Cl(2)
Cl(1)–Pd–Cl(2)
177.62(9)
88.94(10)
93.25(4)
´
[5] G. Esquius, J. Pons, R. Yanez, J. Ros, J. Organomet. Chem. 619
(2001) 14.
´
[6] G. Esquius, J. Pons, R. Yanez, J. Ros, R. Mathieu, B. Donnadieu,
N. Lugan, Eur. J. Inorg. Chem. (2002) 2999.
´
´
´
[7] A. Panella, J. Pons, J. Garcıa-Anton, X. Solans, M. Font-Bardıa, J.
˜
(containing terminal chlorine atoms) is already found in
the literature as a part of nine crystal structures [7,21–
27]. The Pd–Cl (2.2876(10) and 2.2917(10) A) distances in
Ros, Inorg. Chim. Acta. 359 (2006) 2343.
´
´
´
[8] A. Panella, J. Pons, J. Garcıa-Anton, X. Solans, M. Font-Bardıa, J.
˜
˚
Ros, Inorg. Chim. Acta. 359 (2006) 2226.
[9] R. Mathieu, G. Esquius, N. Lugan, J. Pons, J. Ros, Eur. J. Inorg.
Chem. (2001) 2683.
complex 1 are typical of palladium square-planar com-
˚
plexes (Pd–Cl from 2.276 to 2.326 A [7,28–33]). Moreover,
´
´
´
[10] A. Panella, J. Pons, J. Garcıa-Anton, X. Solans, M. Font-Bardıa, J.
˜
˚
the Pd–Npz (2.012(3) A) bond lengths are of the same order
Ros, Eur. J. Inorg. Chem. (2006) 1678.
as those reported in the literature (Pd–Npz from 1.971 to
2.141 A [7,8,10,28,31,34,35]). All the complexes described
[11] W.L. Driessen, Recl. Trav. Pais-Bas 101 (1982) 441.
[12] W.G. Haanstra, W.L. Driessen, R.A.G. de Graaff, G.C. Sebregts, J.
Suriano, J. Reedijk, U. Turpeinen, R. Hamalainen, J.S. Wood,
Inorg. Chim. Acta 189 (1991) 243.
[13] S. Komiya, Synthesis of Organometallic Compounds: A Practice
Guide, Ed. Board, New York, USA, 1997.
[14] G.M. Sheldrick, SHELXS-97, Program for Crystal Structure Determi-
nation and SHELXL-97, Program for Crystal Structure Refinement,
University of Go¨ttingen, Germany, 1997.
˚
above have a cis disposition of the pyrazolic ligands there-
fore; the angles N–Pd–N and Cl–Pd–Cl are also likely to be
compared. In most of the cases, the Cl–Pd–Cl angle
appears to be wider than the N–Pd–N angle, often by more
than 2ꢁ. In structure 1, cis N–Pd–N angles deviate 1.55ꢁ
(88.45(13)ꢁ). Other bond lengths and angle data of interest
are gathered in Table 2.
´
´
[15] J. Garcıa-Anton, J. Pons, X. Solans, M. Font-Bardia, J. Ros, Eur. J.
Inorg. Chem. (2002) 3319.
[16] A. Rimola, M. Sodupe, J. Ros, J. Pons, Eur. J. Inorg. Chem. (2006) 447.
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[19] D.H. Williams, I. Fleming, Spectroscopic Methods in Organic
Chemistry, McGraw-Hill, London, UK, 1995.
[20] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 4th ed., Wiley, New York, USA, 1986.
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Ivanov, Koord. Kim (Russ.) 5 (1979) 1406.
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4758.
4. Conclusion
The N-alkylaminopyrazole ligands (bdmae, and bdmai)
can coordinate Pd(II) centres in different ways. In com-
plexes 1 and 2 these ligands show bidentate coordination
(Npz, Npz) and in complexes 3 and 4 shows tridentate coor-
dination (Npz, Namino, Npz). Furthermore, we have demon-
strated the hemilabile properties of these ligands when
coordinated to Pd(II). When complexes 3 and 4 are heated
under reflux in solution of Et4NCl in CH3CN, 1 and 2 are
obtained once again. This could be considered as type III
hemilability [36].
[26] Yu Ni, Shu-wei Li, Kai-bei Yu, Wei-zhong Zheng, Liang-fu Zhang,
Sicuani Dx. Xuebau, Zir. Kex. (Chin.) 22 (1999) 707.
[27] A. Jouaiti, M.W. Hosseini, N. Kyritsakas, Eur. J. Inorg. Chem.
(2003) 57.
5. Supplementary material
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic Data
Centre, CCDC reference number 604072 for compound
[1] Æ CH2Cl2. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ. UK; fax: +44 1223336033; e-mail:
deposit@ccdc.cam.acuk or www.htpp://ccdc.cam.ac.uk.
´
´
[28] J.A. Perez, J. Pons, X. Solans, M. Font-Bardıa, J. Ros, Inorg. Chim.
Acta 358 (2005) 617.
´
[29] V. Montoya, J. Pons, X. Solans, M. Font-Bardıa, J. Ros, Inorg.
Chim. Acta 358 (2005) 2312.
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[30] V. Montoya, J. Pons, X. Solans, M. Font-Bardıa, J. Ros, Inorg.
Chim. Acta 359 (2006) 25.
[31] M.D. Ward, J.S. Fleming, E. Psillakis, J.C. Jeffery, J.A. McCleverty,
Acta Crystallogr. C54 (1998) 609.
[32] D.B. Grotjahn, D. Combs, S. Van, G. Aguirre, F. Ortega, Inorg.
Chem. 39 (2000) 2080.
Acknowledgement
[33] D.B. Grotjahn, S. Van, D. Combs, A.A. Lev, C. Scheneider,
C.D. Incarvito, K. Lam, G. Rossi, A.L. Rheinghold, M.
Rideout, C. Meyer, G. Hernandez, L. Mejorado, Inorg. Chem.
42 (2003) 3347.
´
Support by the Spanish Ministerio de Educacion y Cul-
tura (Project BQU2003-03582) is gratefully acknowledged.
[34] Chin-Wing Chan, D.M.P. Mingos, A.A.J.P. White, D.J. Williams, J.
Chem. Soc., Dalton Trans. (1995) 2469.
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