Asymmetric and symmetric triazenido cyclopalladated complexes: Synthesis, structural analysis and DFT calculations

Article abstract of DOI:10.1016/j.molstruc.2014.11.069

The reaction of [Pd{dmba}(μ-N₃)]₂ (dmba = N,N-dimethylbenzylamine) with 1-(2-fluorophenyl)-3-(4-nitrophenyl)triazenido (L¹) or 1,3-bis(4-nitrophenyl)triazenido (L²) anions, in methanol, and subsequent treatment with pyridine (py) allows the preparation of the corresponding cyclopalladated compounds [Pd(dmba)(L¹)(py)] (1) and [Pd(dmba)(L²)(py)]·py (2). The acentric mononuclear entities of (1) and (2) are connected by weak intermolecular non-classical CH?C hydrogen bonds, which results in 2-D arrangements by translation, along the [1 0 0] and [0 0 1] crystallographic directions, respectively.

Full text of DOI:10.1016/j.molstruc.2014.11.069

Journal of Molecular Structure 1083 (2015) 311–318
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Asymmetric and symmetric triazenido cyclopalladated complexes:
Synthesis, structural analysis and DFT calculations
Ana Paula Härter Vaniel a, Antonio Eduardo Mauro b, Adelino Vieira de Godoy Netto b,
Eduardo Tonon de Almeida c, Paulo Cesar Piquini d, Priscilla Zambiazi e, Davi Fernando Back e,
,
⇑
Manfredo Hörner e,
⇑
a Universidade de Passo Fundo, Instituto de Ciências Exatas e Geociências, 99001-970 Passo Fundo, RS, Brazil
b Instituto de Química de Araraquara, UNESP – Univ.Estadual Paulista, 14800-900 Araraquara, SP, Brazil
c Universidade Federal de Alfenas – UNIFAL-MG, Instituto de Química – IQ, Alfenas, MG 37130-000, Brazil
d Departamento de Física, Universidade Federal de Santa Maria (UFSM), 97110-970 Santa Maria, RS, Brazil
e Departamento de Química, Universidade Federal de Santa Maria (UFSM), 97110-970 Santa Maria, RS, Brazil
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
Two new cyclopalladated complexes containing triazenido ligands were obtained.
Compounds were characterized by IR techniques and single crystal XRD.
CAHꢁ ꢁ ꢁC interactions are relevant for molecular assembly during the crystallization.
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of [Pd{dmba}(l-N3)]2 (dmba = N,N-dimethylbenzylamine) with 1-(2-fluorophenyl)-3-(4-
nitrophenyl)triazenido (L1) or 1,3-bis(4-nitrophenyl)triazenido (L2) anions, in methanol, and subsequent
treatment with pyridine (py) allows the preparation of the corresponding cyclopalladated compounds
[Pd(dmba)(L1)(py)] (1) and [Pd(dmba)(L2)(py)]ꢁpy (2). The acentric mononuclear entities of (1) and (2)
are connected by weak intermolecular non-classical CAHꢁ ꢁ ꢁC hydrogen bonds, which results in 2-D
arrangements by translation, along the [100] and [001] crystallographic directions, respectively.
Ó 2014 Elsevier B.V. All rights reserved.
Received 19 September 2014
Received in revised form 28 November 2014
Accepted 28 November 2014
Available online 5 December 2014
Keywords:
Triazenido ligand
Supramolecular arrangement
Cyclopalladated complex
Non-classical CHꢁ ꢁ ꢁC hydrogen bond
Introduction
or anionic ligands [1–4]. A phlethora of new ortho palladated
derivatives with distinct structures and physico-chemical proper-
Cyclometallation reaction can be defined as the formation of a
bond between a transition metal and a carbon atom of one of its
ligands, affording a metallocycle [1–4]. Particularly, spectacular
progress has been made in this rich and active area of organome-
tallic chemistry by using palladium as metal center due to the
importance of cyclopalladated compounds in catalysis [5,6],
organic synthesis [7,8], medicinal chemistry [9–12] and nanotech-
nology [13–14].
ties may be obtained from these reactions due to the large and
diverse number of ligands available. For many years, we have been
interested in the reactivity of pseudohalido-bridged cyclopalladat-
ed dimeric complexes [15–21]. Particularly, the cyclometallated
[Pd(dmba)(l-N3)]2 (dmba = N,N-dimethylbenzylamine) is a versa-
tile precursor in azido-bridge splitting reactions and dipolar cyclo-
addition of unsaturated molecules (such as CS2) to a coordinated
azido ligand [22,23]. As an example, we reported the synthesis
One of the most important reactions of cyclometallated
compounds is the cleavage of halide bridged dimers by neutral
and characterization of [Pd(dmba)(l-N,SACN3S2)]2 [22], which
was the first X-ray crystal structure of an ortho metallated complex
bearing the heterocyclic anion [CN3S2]ꢂ. It was a result of the 1,3-
dipolar cycloaddition of carbon disulfide to the azide bridge in
⇑
Corresponding authors. Tel.: +55 55 3220 8650.
E-mail addresses: daviback@gmail.com (D.F. Back), hoerner.manfredo@gmail.
[Pd(dmba)(
[Pd(dmba)(
l
l
-N3)]2. In addition, another advantage on using
-N3)]2 as precursor is that the formation of the
com (M. Hörner).
http://dx.doi.org/10.1016/j.molstruc.2014.11.069
0022-2860/Ó 2014 Elsevier B.V. All rights reserved.

312
A.P. Härter Vaniel et al. / Journal of Molecular Structure 1083 (2015) 311–318
Table 1
products from is readily confirmed by monitoring the strong
m
as(N3) bandat 2059 cmꢂ1 [24].
Crystal data and structure refinement for 1 and 2.
However, apart from bridge cleavage reactions of azido-bridged
Complex
1
2
dimers with various phosphines and other ligands [15–21], studies
involving such reactions with triazenido have not been carried out
so far. In particular, it seemed interesting to us to investigate the
reactions of cyclopalladated compounds with triazenido ligands
for the reasons that follow. Firstly, due to the ability of these
ligands to coordinate with metal atoms in a variety of modes, as
it is well documented in the literature [25–27], and secondly,
due to their chemotherapeutic properties [28,29] which can be
enhanced by coordination with palladium ions.
Molecular formula
Molecular weight
Radiation, wavelength
Crystal system
Space group
a (Å)
C
26H25FN6O2Pd
C28.50H28N7.50O4Pd
645.98
Mo Ka, 0.71073 Å
578.92
Mo K , 0.71073 Å
a
Orthorhombic
P212121
a = 8.557(5) Å
b = 13.539(5) Å
c = 21.832(5) Å
Triclinic
P(ꢂ1)
a = 11.2962(10) Å
b = 11.9100(10) Å
c = 12.217(10) Å
b (Å)
c (Å)
a
= b =
c
= 90°
a
= 72.529(5)°
b = 76.444(5)°
c
= 66.451(4)°
As part of our ongoing studies of both cyclopalladated and
triazenido ligands [15–24], the reaction of the dimeric compound
Z (mol/unit cell)
V (Å3)
4
2
2529.3(18) Å3
1424.87(17) Å3
Dc (g cmꢂ3
)
1.520 mg/m3
1.506 mg/m3
[Pd(dmba)(l-N3)]2 with the deprotonated 1-(2-fluorophenyl)-3-
(4-nitrophenyl)triazene (L1) or 1,3-bis(4-nitrophenyl)triazene (L2)
has been carried out in the presence of pyridine. The single-crystal
structural analysis of triazenido complexes, including [Pd(II)
(dmba)(Py)] cations bearing a one-dimensional arrangement via
secondary hydrogen bonding, is reported.
Crystal size (mm)
0.243 ꢃ 0.156 ꢃ 0.11 mm 0.25 ꢃ 0.2 ꢃ 0.15 mm
l
(cmꢂ1
)
0.776 mmꢂ1
293
0.699 mmꢂ1
293
659
Temperature (K)
F (000)
h range for data
collection
Index range
1176
2.40–27.66°
2.35–25.09°
ꢂ11 6 h 6 0
ꢂ17 6 k 6 0
ꢂ28 6 l 6 0
3317
ꢂ13 6 h 6 13
ꢂ13 6 k 6 14
0 6 l 6 14
5276
Experimental
Reflections collected
Independent reflections
3317 [R(int) = 0.0208]
5019/
[R(int) = 0.0157]
5019/0/370
X-ray crystallography
Data/restraints/
parameters
3317/0/325
1.045
The Xray data of both compounds were collected at room
temperature on an Enraf-Nonius CAD4 diffractometer, using MoK
Goodness-of-fit on F2
1.031
a
Final R indices [I > 2
r
(I)] R1 = 0.0380
R1 = 0.0272
wR2 = 0.0681
R1 = 0.0390
wR2 = 0.0723
–
radiation (k = 0.70930 Å) and a graphite monochromator. The unit
cell dimensions were obtained from a least-squares fit of the set-
ting angles of 25 reflections. Lorenz and polarization corrections
were also applied [30]. The structures were solved using direct
methods and refined on F2 by full-matrix least-squares methods
with anisotropic displacement factors for all non-hydrogen atoms
[31]. The H atoms of the phenyl groups were geometrically posi-
tioned (CAH = 0.93 Å for Csp2 atoms) and were considered to be
dependent on their respective C atoms, with Uiso(H) values set at
1.2UeqCsp2. Molecular graphs were obtained using the program
DIAMOND 3.1 afor Windows [32]. Details of the structure refine-
ment and the final reliability factors are given in Table 1.
wR2 = 0.0748
R1 = 0.0964
wR2 = 0.0883
ꢂ0.02(5)
R indices (all data)
Absolute structure
parameter
Largest diff. peak and
hole
0.539 and ꢂ0.646 eÅꢂ3
0.381 and
ꢂ0.402 eÅꢂ3
dried in vacuum. Yield: 53%. Melting point: 182 °C. Anal. Calc. for
C12H9NO2F (218): C, 66.05; H, 4.12; N, 6.42. Found: C, 66.12; H,
4.09; N, 6.77. IR (KBr/cmꢂ1): 3200–3100 [s,
m
(NAH)]; 1498[
mas(-
NO2)]; 1397[m(N@N)]; 1319 [vs,
m
s(NO2)]; 1184 [vs, s(NAN)];
m
1256 [( (FACar)].
m
Instruments
Synthesis of [Pd(dmba)(L1)(py)] (1)
The cyclopalladated complex 1 was obtained from a solution
(0.210 g, 0.348 mmol) of [Pd(dmba)( -N3)]2 in 10 mL of methanol,
KBr pellets of the free ligands and complexes were prepared in
order to acquire the IR spectra using a Bruker TENSOR27 FTIR-
Spectrometer in the 4000–400 cmꢂ1 spectral range. For determina-
tion of the melting points, single crystals of complexes 1 and 2
inserted into a glass capillary, were adapted on a MEL-TEMP II
instrument.
l
which was slowly added to a mixture of 1-(2-fluorophenyl)-3-(4-
nitrophenyl)triazene (0.200 g, 0.768 mmol) in 10 mL of methanol/
KOH. After 1 h of continuous stirring at room temperature, 1 mL
of pyridine was added to the deep red reaction mixture which
was then stirred for a further 24 h. Red-prism-shaped crystals suit-
able for X-ray analysis were obtained by slow evaporation of the
solvent mixture at room temperature. Yield of the crystallized
complex: 47%, based on FC6H4NNN(H)C6H4NO2. Anal. Calc. for C26-
H25FN6O2Pd (578.92 g/mol): C, 53.89; H, 4.31; N, 14.50%. Found: C,
52.51; H, 4.03; N, 14.51%. Melting point: 185 °C (decomposition).
Synthesis
The ligand 1,3-bis(4-nitrophenyl)triazene (L2) and the precursor
complex [Pd(dmba)(l-N3)]2 were prepared as reported in the
literature [24,33].
See Scheme 1. IR (KBr/cmꢂ1): the
[s, as(NO2)], 1317 [s, m
s(NO2)], and1292 cmꢂ1 [vs,
m
NAH band is absent. 1503
Synthesis of 1-(2-fluorophenyl)-3-(4-nitrophenyl)triazene (L1)
m
m
as(NNN)].
2-Fluoroaniline (0.303 g, 2.76 mmol) was dissolved in a mixture
of 15 mL of CH3COOH and 5 mL of distilled water and the system
was cooled to 0 °C. Under constant stirring, sodium nitrite
(0.190 g, 2.76 mmol) was also added. After 30 min of stirring
slowly added 4-nitroaniline (0.380 g, 2.76 mmol) previously
dissolved in 20 ml of glacial acetic acid, 20 min after the addition
of the amine the solution was neutralized to pH 6.0 with sodium
acetate. The yellow precipitate obtained was filtered under vac-
uum and washed several times with cold water. The product was
Synthesis of [Pd(dmba)(L2)(py)]ꢁpy (2)
In the same way, the cyclopalladated complex (2) was obtained
from a solution (0.187 g, 0.349 mmol) of [Pd(dmba)(l-N3)]2 in
10 mL of methanol, which was slowly added to a solution of 1,3-
bis(4-nitrophenyl)triazene (0.200 g, 0.697 mmol) in 20 mL of
methanol/KOH. After 1 h of continuous stirring at room tempera-
ture, 1 mL of pyridine was added to the deep red reaction mixture,

A.P. Härter Vaniel et al. / Journal of Molecular Structure 1083 (2015) 311–318
313
Table 2
which was then stirred for a further 24 h. After slow evaporation of
the solvents, red prism-shaped crystals suitable for X-ray analysis
were obtained. Yield of the crystallized complex: 50%, based on
free ligand. Anal. Calc. for C28H27N8O4Pd (645.98 g/mol): C,53.01;
H,4.17; N,17.33%. Found: C,52.8; H,4.11; N, 17.1%. Melting point:
208–212 °C (decomposition). IR (KBr/cmꢂ1) of the free ligand O2-
Selected bond lengths (Å) and angles (°) for [Pd(dmba)(L1)(py)] (1) and [Pd(dmba)(L2)
(py)]ꢁpy (2).
Complex (1)
Complex (2)
Bond lengths
PdAC(31)
PdAN(13)
PdAN(6)
PdAN(5)
Bond lengths
PdAC(41)
PdAN(6)
PdAN(7)
PdAN(11)
1.981(6)
2.047(5)
2.094(5)
2.180(6)
1.363(8)
1.334(6)
1.282(6)
1.987(4)
2.036(3)
2.083(3)
2.149(3)
1.313(4)
NC6H4NNN(H)C6H4NO2: 3282 [s,
[m, (N@N)]; 1326 [vs,
s(NO2)]; and 1170 cmꢂ1 [vs,
[Pd(dmba)(L1)(py)] (2): the
NAH band is absent. 1475 [s,
1322 [s, as(NNN)].
s(NO2)], and 1275 cmꢂ1 [vs,
m
(NAH)]; 1518 [vs,
m
as(NO2)];1405
s(NAN)];
as(NO2)],
m
m
m
m
m
FAC(12)
N(11)AN(12)
Bond angles
m
m
N(13)AN(12)
N(11)AN(12)
Bond angles
C(31)APdAN(13)
C(31)APdAN(6)
N(13)APdAN(6)
C(31)APdAN(5)
N(13)APdAN(5)
N(6)APdAN(5)
C(41)APdAN(6)
C(41)APdAN(7)
N(6)APdAN(7)
C(41)APdAN(11)
N(6)APdAN(11)
N(7)APdAN(11)
C(35)AN(6)APd
N(12)AN(11)APd
93.68(14)
82.48(15)
174.98(13)
176.47(15)
88.27(13)
95.73(13)
117.6(3)
Computational details
93.3(2)
82.8(2)
170.62(19)
174.6(2)
86.5(2)
Density functional theory (DFT) calculations have been per-
formed to study the electronic structure and to determine the reac-
tivity indices (Fukui function) using the Gaussian 09 package [34].
The correlation and exchange functional was described by the
hybrid B3LYP functional [35–36]. The molecular orbitals of the H,
C, N, O, and F atoms were represented by the 6-31G basis set aug-
mented by p and d polarization functions. The Pd orbitals were
described by the compact effective potential with split valence
basis set (CEP-31G) [37]. Geometry optimizations were performed
and the obtained geometries were verified to exhibit only real
infrared frequencies. Local softness maps [38] have been obtained
as differences between calculated electronic densities of the rele-
vant charge states of each studied systems. The resulting 3D maps
were generated through the ChemCraft package [39].
98.2(2)
122.9(3)
coordination geometry around the Pd2+ ion is nearly square-planar
(r.m.s. deviation of 0.1237 Å). The metal center is surrounded
by the C and N atoms of the ortho metallated dmba ligand, a
deprotonated 1-(2-fluorophenyl)-3-(4-nitrophenyl)triazenido ion
[FC6H4NNNC6H4NO2]ꢂ acts as
a monodentate (two-electron
donor), and a neutral pyridine molecule is in a trans position to
the carbon atom of the dmba. The elevation of Pd from the plane
formed by the atoms C31, N13, N5, and N6, is 0.026(3) Å.
The structural parameters of the Pd(dmba) fragment are similar
to those found in other complexes containing this ligand. The
PdAC31 bond distance [1.980(6) Å] and the PdAN6 bond distance
[2.093(5) Å] are in good agreement with the distances found in
other palladium-dmba complexes [22,24,40].
Results and discussion
The dimeric precursor [Pd(dmba)(l-N3)]2 readily undergoes
The PdAN5py bond distance [2.181 Å], which is trans to the
r-
bridge cleavage reactions with deprotonated 1-(2-fluorophenyl)-
3-(4-nitrophenyl)triazene or 1,3-bis(4-nitrophenyl)triazene, in the
presence of pyridine, to afford the monomeric, neutral complexes
[Pd(dmba)(L1)(py)] (1) and [Pd(dmba)(L2)(py)]ꢁpy (2), respectively,
as yellow colored solids (Scheme 1).
bonded aryl group, is longer than the sum of the covalent radii
which is 2.08 Å [41]. The pyridine ring (N5AC45) is planar within
experimental accuracy (r.m.s. = 0.0105 Å). The PdAN5 bond dis-
tance of 2.181(6) Å is longer than the sum of the covalent radii,
which totals 2.08 Å [42], and is in good agreement with values
found in the compounds [PdANPy = 2.03 Å] [43] and [Pd(dmba)-
Py(Cl)] [PdANPy = 2.042 Å] [42].
The IR spectra (KBr pellets) of (1) and (2) show the absence of
the absorption assigned to
mas(N3), which is observed as a very
strong band at 2059 cmꢂ1 in the IR spectrum of [Pd(dmba)(
l
-
The PdAN11 bond length of 2.047(5) Å between the metallic
center and the nitrogen atom of the triazenido chain agrees well
with the Pd-N bond length of 2.034(7) Å observed in the palladacy-
cle [Pd(C6H4NHN@C(CH3)C5H4N)(p-tolNNNp-tol)] [44].
If we take into account the triazenido ligand, we can observe
that it shows a strong deviation from planarity, with the largest
interplanar angle of 26.0(6)° occurring between the phenyl ring
of the ortho-fluorophenyl group and the plane defined by the
N3)]2 [24]. The absence of the
mNAH band in the 3100–
3200 cmꢂ1 region demonstrates the coordination of the triazenido
anions originated by deprotonation of the respective free triazenes,
and this is characterized by strong m
asNNN bands at 1292 cmꢂ1 for
(1) and 1275 cmꢂ1 for (2), respectively.
Crystal data and experimental parameters are given in Table 1.
Selected bond distances and angles of the title complexes are listed
in Table 2. Fig. 1 shows the molecular structure of the entities of
[Pd(dmba)(L1)(py)] (1) in a thermal ellipsoid representation [25–
27].
NNN moiety. Due to the delocalization of the
p electrons over
the nitro group, and the C11AC16 phenyl ring extended over the
N11AN12@N13 chain, in this part of the triazenido ligand the devi-
ation from planarity is less accentuated, with interplanar angles of
The molecular structure of (1) is depicted in Fig. 1. The X-ray
structure analysis shows that, in the monomeric complex, the
R1
H
N
NH2
H2N
Pd
N
N
N
N
N
(i , ii)
(iii)
N
+
N
R2
NO2
R2
R1
NO2
R2
R1
NO2
R1 = F - complex 1
R2 = NO2 - complex 2
(i) NaNO2, HAc, 0-5oC; (ii) H2O, NaCOOCH3; (iii) [Pd(dmba)(N3)]2, KOH, MeOH, pyridine
Scheme 1.

314
A.P. Härter Vaniel et al. / Journal of Molecular Structure 1083 (2015) 311–318
Fig. 1. Displacement ellipsoids are drawn at the 40% probability level.
Table 3
8.7(1)° for O1N4O2/C21AC26 and 16.6(7)° for C21AC26/
N11AN12@N13. The delocalization of the electrons over the
NNN chain and the para-nitrophenyl substituent is also underlined
by the deviation from the normal NAN bond lengths. The
N12AN13 bond length of 1.334(7) Å is longer than the characteris-
Secondary interactions: lengths (Å) and angles (°) for complexes (1) and (2).
p
DAHꢁ ꢁ ꢁAa
Complex (1)
DAH
HꢁꢁꢁA
DꢁꢁꢁA
DAHꢁꢁꢁA
C39#AH39#ꢁ ꢁ ꢁN12
0.960(8)
0.930(7)
0.930(9)
0.930(9)
0.930(9)
2.774(8)
2.661(9)
2.843(7)
2.835(9)
2.865(10)
3.471(11)
3.588(13)
3.753(11)
3.718(13)
3.652(14)
133.01(41)
174.55(43)
166.32(55)
159.11(55)
143.22(54)
C45AH45ꢁ ꢁ ꢁ F
tic value for
a double bond (1.24 Å), whereas N11AN12
C44AH44ꢁ ꢁ ꢁC34#
C44AH44ꢁ ꢁ ꢁC35#
C44AH44ꢁ ꢁ ꢁC36#
[1.282(6) Å] is shorter than the expected value of 1.44 Å for a single
bond, and N13AC21 [1.388(3) Å] is shorter than what is expected
for a CarylAN single bond [40]. Note that the deviation of the pla-
narity of the N11@N12AN13 chain can also be explained by a
hydrogen bond between the atoms N12 and C39#AH39# in a
bonding order of 2.744(8) Å [H39#ꢁ ꢁ ꢁN12]. Symmetry code: (#)
1 ꢂ x, 0.5 + y, 1.5 ꢂ z. Other details can be seen in Table 3. Fig. 2
shows the interactions between the atoms.
Complex (2)
C48#AH48#ꢁꢁꢁO1b
0.861(3)
2.185(1)
2.957(2)
149.15(11)
a
D = donor and A = acceptor. Symmetry operations used to generate equivalent
atoms: (#) 1 ꢂ x, 0.5 + y, 1.5 ꢂ z.
b
Complex 2. Symmetry operations(#) 1 ꢂ x, ꢂy, ꢂz.
On the other hand, the stark deviation from the ortho-fluoro-
phenyl group can be attributed to a weak intramolecular hydrogen
bond between a H atom (see Fig. 2) from the pyridine ligand and
the F atom, C45AH45ꢁ ꢁ ꢁF [H45ꢁ ꢁ ꢁF = 2.661(9) Å]—for more infor-
mation, see Table 3.
Finally, it can be observed in Fig. 2 that there are also weak con-
tacts between adjacent molecules as a result of CAHꢁ ꢁ ꢁCaryl inter-
molecular hydrogen bonding. The related molecules of (2) are
connected by weak C44AH44ꢁ ꢁ ꢁC34#, C35#, and C36# interactions
{2.843(7) Å [H44ꢁ ꢁ ꢁC34#]; 2.835(9) Å [H44AC35#]; 2.865(10) Å
and [H44AC36#] symmetry code: (#) 1 ꢂ x, 0.5 + y, 1.5 ꢂ z}, giving
rise to an extended trifurcated hydrogen bond [45–47] along the
[100] crystallographic direction (Fig. 2).
[1.987(6) Å] and the PdAN7 bond distance [2.082(6) Å] are very
similar to that found in complex (2) and other related palladium-
dmba complexes [22,24,40].
In the structure of (2), the pyridine ring N6AC35 is cis-oriented
to the C atom of the dmba fragment, and the Pd1AN6 bond length
[2.036(6) Å] is typical for a PdAN(sp2) [41].
The trans position for the r-bonded aryl group in (2) is occupied
by the triazenido ligand. The observed PdAN11 bond length
[2.149(4) Å] is longer than the sum of the covalent radii of Pd
and N [41], which may be a result of the trans influence of the aryl
group on the dmba ligand.
Due to the delocalization of the
p electrons in both nitro groups
and the phenyl rings, which extends over the triazenide chain, the
whole triazenido ligand shows little deviation from planarity. The
two terminal 4-nitrophenyl substituents show interplanar angles
with the NAN@N chain of 15.9(1)° and 5.2(1)°, respectively, which
confirms the small deviation from planarity for the whole
molecule.
The analysis of the secondary crystal structure of (2) also reveals
that the individual molecules are ordered as synthons [45–48] by
C48AH48ꢁ ꢁ ꢁO1# and C48#AH48#ꢁ ꢁ ꢁO1 intermolecular hydrogen
bonding [H48ꢁ ꢁ ꢁO1# = 2.453(9) Å; C48ꢁ ꢁ ꢁO1# = 3.254(12) Å; and
symmetry code (#) 1 ꢂ x, ꢂy, ꢂz] along the [101] crystallographic
direction. The occurrence of this hydrogen bonding can also explain
the small deviation from planarity for the triazenido ligand. The
Structure of [Pd(dmba)(L2)(py)]ꢁpy (2)
An illustration of the structure of complex (2) is shown in Fig. 3.
The X-ray analysis of the monomeric complex shows that the
nearly square planar coordinated Pd2+ ion is surrounded by the C
and N atoms of an ortho–metallated dmba ligand, a monodentate
1,3-bis(4-nitrophenyl)triazenido ion [O2NC6H4N@NANC6H4NO2]ꢂ,
and a pyridine molecule. Differently to complex (1), in the struc-
ture of (2) the trans-position for the carbon atom of dmba is occu-
pied by the N atom from the triazenido anion (Fig. 3).
The structural parameters of the Pd(dmba) fragment are similar
to those found in complex (1). The Pd-C41 bond distance

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315
Fig. 2. The packing in complex 1 shows multiple hydrogen-bonding. Symmetry operations used to generate equivalent atoms: (#) 1 ꢂ x, 0.5 + y, 1.5 ꢂ z.
Fig. 3. Displacement ellipsoids are drawn at the 40% probability level. Disorder pyridine solvate has been omitted for clarity.
hydrogen-bonding scheme can be seen in the extended crystal-
lattice structure (Fig. 4).
As can be seen from this Figure the frontier orbitals from
compounds (1) and (2) reveal a great similarity, with the electronic
distributions forming -like orbitals delocalized along the triazene.
p
A distinctive feature of these orbitals is that in the HOMO there is
an electron concentration on the N11 atoms but not on N12, while
for the LUMO the opposite is observed (see Figs. 1, 3 and 5).
The Fukui functions for nucleophilic, f+(r), and electrophilic,
fꢂ(r), attacks were estimated as the differences between total
electronic densities of appropriate charge states, according to the
following formulas:
fþðrÞ ¼ qNðrÞ ꢂ qNꢂ1ðrÞ;
fꢂðrÞ ¼ qNþ1ðrÞ ꢂ qNðrÞ;
Frontier orbitals and Fukui functions
In order to analyse the influence of different ligands on the
chemical activity of compounds (1) and (2), we have determined
their frontier orbitals (HOMO and LUMO), and their Fukui
functions related to nucleophilic and electrophilic attacks [38].
These quantities give almost the same information, since com-
pounds under electrophilic (nucleophilic) attacks are expected to
lose (gain) charge through their frontier orbitals. Fig. 5 shows the
frontier orbitals for compounds (1) and (2).

316
A.P. Härter Vaniel et al. / Journal of Molecular Structure 1083 (2015) 311–318
Fig. 4. The hydrogen-bonding scheme in the structure of (2). Symmetry transformations to generate equivalent atoms:(#) 1 ꢂ x, ꢂ y, ꢂ z.
where qX(r) represents the total electronic density at position r of a
system with X electrons.
(1) are the N11 and N13 atoms of triazene. No contribution from
the fluorine atom is observed for both cases.
The Fukui functions for compounds (1) and (2) are shown in
Fig. 6. For compound (1), the active sites for nucleophilic attacks
are centered on the nitrogen atoms N12 and N13 of triazene, with
contributions from the nitro group and the pyridine. For electro-
philic attacks, on the other hand, the reactive sites of compound
For compound (2), the reactive sites for electrophilic attacks fol-
low the same pattern as for compound (1). For nucleophilic attacks,
however, some differences can be noted. The N12 and nitro groups
remain as active sites. The presence of a second nitro group and the
absence of the fluorine atom change the reactive sites from the
Fig. 5. Illustrative pictures of the frontier orbitals HOMO and LUMO for compounds (1) and (2).

A.P. Härter Vaniel et al. / Journal of Molecular Structure 1083 (2015) 311–318
317
Fig. 6. Illustrative pictures of the Fukui functions for nucleophilic, f+(r), and electrophilic, fꢂ(r), attacks calculated for compounds (1) and (2).
N13 atom and pyridine, in compound (1), to the additional nitro
group of compound (2).
(proc. 483902/2011-0) and Proc. 305254/2009-0. FAPERGS (Fun-
dação de Amparo à Pesquisa do Estado do Rio Grande do Sul) Edital
No. 002/2011-PqG.
The discussed differences between compounds (1) and (2)
against nucleophilic attacks do not prevail, however, over the gen-
eral behavior of the Fukui functions, which show a great similarity
for the two compounds, despite the asymmetry of compound (1)
introduced by the fluorine atom. In this respect, it is interesting
to note the apparent chemical inactivity of the fluorine atom
against nucleophilic and electrophilic attacks.
References
[1] J. Dehand, M. Pfeffer, Coord. Chem. Rev. 18 (1976) 327.
[2] A.D. Ryabov, Chem. Rev. 90 (1990) 403.
[3] I. Omae, Coord. Chem. Rev. 248 (2004) 995.
[4] J. Cámpora, P. Palma, E. Carmona, Coord. Chem. Rev. 193–195 (1999) 207.
[5] R.B. Bedford, C.S.J. Cazin, D. Holder, Coord. Chem. Rev. 248 (2004) 2283.
[6] I.P. Beletskaya, A.V. Cheprakov, J. Organomet. Chem. 689 (2004) 4055.
[7] I.P. Beletskaya, A.V. Cheprakov, Chem. Rev. 100 (2000) 3009.
[8] J. Dupont, C.S. Consorti, J. Spencer, Chem. Rev. 105 (2005) 2527.
[9] N. Cutillas, G.S. Yellol, C. de Haro, C. Vicente, V. Rodríguez, J. Ruiz, Coord. Chem.
Rev. 257 (2013) 2784.
Conclusions
The synthesis of organometallics containing diazoamino frag-
ments proved to be very effective, both in the methodology and
in the yields obtained. The complexes obtained have been charac-
terized by X-ray diffraction, showing a great potential for the for-
mation of non-classical hydrogen interactions. This situation was
crucial in detecting interesting supramolecular trends in crystal
structures of cyclopalladated compounds. Moreover, theoretical
calculations show no significant change when the change in the
position and nature of the substituent. This evidence allows us to
plan carefully new synthesis and choose for symmetrical com-
plexes for use as catalysts.
[10] A.C.F. Caires, Med. Chem. 7 (2007) 484.
[11] J. Spencer, A. Casini, O. Zava, R.P. Rathnam, S.K. Velhanda, M. Pfeffer, S.K.
Callear, M.B. Hursthouse, P.J. Dyson, Dalton Trans. (2009) 10731.
[12] F.A. Serrano, A.L. Matsuo, P.T. Monteforte, A. Bechara, S.S. Smaili, D.P. Santana,
T. Rodrigues, F.V. Pereira, L.S. Silva, J. Machado Jr., E.L. Santos, J.B. Pesquero,
R.M. Martins, L.R. Travassos, A.C.F. Caires, E.G. Rodrigues, BMC Cancer 11
(2011) 296.
[13] D.A. Alonso, C. Nájera, Chem. Soc. Rev. 39 (2010) 2891–2902.
[14] R.F. Carina, A.F. Williams, G. Bernardinelli, Inorg. Chem. 40 (2001) 1826.
[15] V.A. de Lucca Neto, A.E. Mauro, A.C.F. Caires, S.R. Ananias, E.T. De Almeida,
Polyhedron 18 (1999) 413.
[16] A.C.F. Caires, E.T. de Almeida, A.E. Mauro, J.P. Hemerly, S.R. Valentini, Quim.
Nova 22 (1999) 329.
[17] S.R. Ananias, A.E. Mauro, V.A. de Lucca Neto, Trans. Met. Chem. 26 (2001) 570.
[18] E.T. de Almeida, A.M. Santana, A.V.G. Netto, C. Torres, A.E. Mauro, J. Therm.
Anal. Calorim. 82 (2005) 361.
Supplementary data
[19] M.C. da Rocha, A.M. Santana, S.R. Ananias, E.T. de Almeida, A.E. Mauro, M.C.P.
Placeres, I.Z. Carlos, J. Braz. Chem. Soc. 18 (2007) 1473.
Crystallographic data for the structural analyses have been
deposited with the Cambridge Crystallographic Data Centre (CCDC
no. 987440 and 987441). Further details of the crystal struc-
ture investigations are available free of charge via www.ccdc.
cam.ac.uk/conts/retrieving.htmlor from CCDC at 12 Union
Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033; and
e-maildeposit@ccdc.cam.ac.uk.
[20] A.M. Santana, J.G. Ferreira, A.C. Moro, S.C. Lemos, A.E. Mauro, A.V.G. Netto,
R.C.G. Frem, R.H.A. Santos, Inorg. Chem. Commun. 14 (2011) 83.
[21] J.G. Ferreira, A. Stevanato, A.M. Santana, A.E. Mauro, A.V.G. Netto, R.C.G. Frem,
F.R. Pavan, C.Q.F. Leite, R.H.A. Santos, Inorg. Chem. Commun. 23 (2012) 63.
[22] A.E. Mauro, A.C.F. Caires, R.H.A. Santos, M.T.P. Gambardella, J. Coord. Chem. 48
(1999) 521.
[23] A.M. Santana, A.E. Mauro, E.T. De Almeida, A.V.G. Netto, S.I. Klein, R.H.A.
Santos, J.R. Zóia, J. Coord. Chem. 53 (2001) 163.
[24] E.T. de Almeida, A.E. Mauro, A.M. Santana, S.R. Ananias, A.V.G. Netto, J.G.
Ferreira, R.H.A. Santos, Inorg. Chem. Commun. 10 (2007) 1394.
[25] V.P. Hanot, T.D. Robert, J.J.A. Kolnaar, J.G. Haasnoot, H. Kooijman, A.L. Spek,
Inorg. Chim. Acta 256 (1997) 327.
[26] S. Brase, J. Kobberling, D. Enders, R. Lazny, M. Wang, S. Brandtner, Tetrahedron
Lett. 40 (1999) 2105.
Acknowledgements
The authors wish to acknowledge CNPq, CAPES, FAPERGS, and
FAPESP for financial support. CNPq: Edital Universal No. 14/2011

318
A.P. Härter Vaniel et al. / Journal of Molecular Structure 1083 (2015) 311–318
[27] C. Karvellas, C.I. Willians, M.A. Whitehead, B.J. Jean-Claude, J. Mol. Struct.
(Theochem.) 535 (2001) 199.
J.V. Orti, J. Cioslowski, D.J. Fox, Gaussian 09, Revision C.01, Gaussian, Inc.,
Wallingford CT, 2009.
[28] E. Carvalho, A.P. Francisco, J. Iley, E. Rosa, Bioorg. Med. Chem. 8 (2000) 1719.
[29] A.M. Zheleva, V.G. Gadjeva, Int. J. Pharm. 212 (2001) 257.
[30] Enraf-Nonius, CAD-4.Software,Version 5.0, Delft, The Netherlands, 1989.
[31] G.M. Sheldrick, SHELXS 97 and SHELXL 97, University of Göttingen, Germany,
1997.
[35] A.D. Becke, J. Chem. Phys. 98 (1993) 1372.
[36] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[37] W.J. Stevens, H. Basch, M. Krauss, J. Chem. Phys. 81 (1984) 6026.
[38] A.K. Chandra, M.T. Nguyen, Int. J. Mol. Sci. 3 (2002) 310.
[39] http://www.chemcraftprog.com.
[32] K. Brandenburg, DIAMOND 3.1a.1997–2005, Version 1.1a.Crystal Impact GbR,
Bonn, Germany.
[40] L.R. Falvello, S. Fernández, R. Navarro, E.P. Urriolabeitia, Inorg. Chem. 36 (1997)
1136.
[33] M. Hörner, L. Bresolin, J. Bordinhão, E. Hartmann, J. Strähle, Acta Crystallogr. C
59 (2003) o426.
[41] L. Pauling, The Nature of the Chemical Bond, third ed., Cornell University Press,
New York, 1960.
[34] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato,
X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F. Ogliaro,
M. Beapark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M.
Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakke, C. Adamo, J.
Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth,
P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman,
[42] Z.-L. Lu, A.A. Neverov, R.S. Brown, Org. Biomol. Chem. 3 (2005) 3379.
[43] M. Hörner, L.C. Vicentin, M. Dahmer, J. Bordinhão, Acta Crystallogr. C 58 (2002)
286.
[44] G. Garcya-Herbosa, N.G. Connelly, A. Muñoz, J.V. Cuevas, G. Orpen, S.D.
Politzer, Organometallic 20 (2001) 3223.
[45] M. Hörner, D.F. Back, F. Broch, G. Manzoni de Oliveira, Polyhedron 31 (2012)
558.
[46] D.F. Back, D. Roman, G. Manzoni de Oliveira, P.C. Piquini, R. Kober, M.A. Ballin,
Inorg. Chim. Acta 412 (2014) 6.
[47] D.S. Reddy, D.C. Craig, G.R. Desiraju, J. Am. Chem. Soc. 118 (1996) 4090.
ˇ
´
[48] D. Drahonovsky, J.-M. Lehn, J. Org. Chem. 74 (2009) 8428.