Synthesis and characterization of platinum(II) complexes with a diazenecarboxamide-appended picolyl-triazole ligand

Article abstract of DOI:10.1002/ejic.201001051

The coordination of the diazenecarboxamides, which were functionalized with the 1-(2-picolyl)-1H-1,2,3-triazole moiety 1, to platinum(II) were studied, where K₂[PtCl₄] and cis-[PtCl₂(DMSO) ₂] were used as the pl

Full text of DOI:10.1002/ejic.201001051

FULL PAPER
DOI: 10.1002/ejic.201001051
Synthesis and Characterization of Platinum(II) Complexes with a
Diazenecarboxamide-Appended Picolyl-Triazole Ligand
[a]
[a]
[a]
ˇ
Damijana Urankar, Andrej Pevec, and Janez Kosmrlj*
Keywords: Platinum / N ligands / Chelates / Click chemistry
The coordination of the diazenecarboxamides, which were
functionalized with the 1-(2-picolyl)-1H-1,2,3-triazole moiety
1, to platinum(II) were studied, where K2[PtCl4] and cis-
[PtCl2(DMSO)2] were used as the platinum sources. The pic-
olyl-triazole (pictri) binding unit enabled chelation to the
metal centre through the 1,2,3-triazole N2 and the pyridyl
nitrogen atoms under mild reaction conditions. When cis-
[PtCl2(DMSO)2] was used, with CH2Cl2 or CH3CN as the re-
action solvents, the pure, stable diamminedichloridoplatin-
um(II) complexes 2 were isolated by filtration in 39 to 83%
yield. The products were structurally characterized in solu-
chemical shifts for 2 appear in the region of –2203 to
–2207 ppm. The structure of complex 2a was confirmed by
single-crystal X-ray crystallography. The formation of the
platinum complexes 2 was monitored using NMR spec-
troscopy. The complexation with cis-[PtCl2(DMSO)2] in
[D7]dmf proceeded through several intermediates, as indi-
cated by the 195Pt NMR spectra with resonances in the range
of –3055 to –2907 ppm. Similarly, the reaction of cis-
[PtCl2(DMSO)2] with diazenecarboxamide, which was func-
tionalized with the nonchelating 1-(2-aminoethyl)-1,2,3-tri-
azole derivative, was examined by NMR spectroscopy.
1
tion by H, 13C and 195Pt NMR spectroscopy. The 195Pt NMR
with cisplatin.[10] Besides their GSH-depleting activity,
some of the diazenes also activated alternative cell-death
pathways.[11] Encouraged by the biological activity of diaz-
enes and inspired by the recent advances in copper-cata-
lyzed azide-alkyne 1,3-dipolar cycloaddition (“click chemis-
try”), we were prompted to design and synthesize a family
of diazenes that were functionalized with the 1-(2-picolyl)-
1H-1,2,3-triazole moiety (Figure 1).[13,14] We anticipated
that this moiety would serve as a novel picolyl-triazole (pic-
tri) ligand to platinum, since it offers a bidentate chelating
system that involves the N2 atom of the 1,2,3-triazole ring
and the pyridine nitrogen atom.
The potential of the triazole-containing ligands prepared
by click chemistry is currently being extensively studied.[15]
Recently, compounds that contain the pictri binding moiety
have been explored as powerful click chelators for transi-
tion-metal ions.[16–18] By using a model compound, we have
experimentally and theoretically explored the chelation of
the pictri unit to CuII, RuII, PdII, AgI and PtII.[17] In all of
the above instances the chelation involved both the triazole
N2 and the picolyl nitrogen atoms and formed a six-mem-
bered metallacycle, which was revealed by X-ray structural
analysis.
Introduction
Cisplatin [cis-diamminedichloridoplatinum(II)] is ap-
proved by the FDA to be used by itself or in combination
with other drugs to treat bladder, ovarian, testicular, cervi-
cal and non-small-cell lung cancers, as well as squamous
cell carcinoma and malignant mesothelioma.[1–3] Despite its
high cure rates, there are several problems associated with
cisplatin, which include the resistance that the tumour cells
acquire after the initial treatment. Drug resistances are
multifunctional processes[4] and it has been suggested that
glutathione (GSH) and glutathione-S-transferase (GST)
constitute the cellular defence.[5,6] To address this issue, cis-
platin analogues that have bioactive carrier ligands that tar-
get GSH or GST have been developed.[7] This emerging ap-
proach is based on a multifunctional strategy, that is, the
design of single chemical entities that are able to simulta-
neously modulate multiple targets.[8]
Our interest in exploring the oxidation of intracellular
thiols has led to diazenecarboxamides, which can be ab-
breviated as diazenes.[9,10] We have shown that diazenes can
decrease the intracellular GSH concentration and inhibit
the growth of different tumour-cell lines.[11,12] These com-
pounds also reduced the survival of cisplatin-resistant sub-
lines and, in a combined treatment, acted synergistically
We decided to explore the coordination properties of the
pictri ligand, which was functionalized with diazenes, as
part of our interest in the synthesis of organic-inorganic
conjugates that have some potential in terms of biological
activity.[19,20] Two different linkers were selected as the con-
nectors between the diazene moiety and the pictri ligand:
those that have an aromatic structure (Figure 1, a) and
[a] Faculty of Chemistry and Chemical Technology, University of
Ljubljana,
Asˇkercˇeva 5, 1000 Ljubljana, Slovenia
E-mail: janez.kosmrlj@fkkt.uni-lj.si
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201001051.
Eur. J. Inorg. Chem. 2011, 1921–1929
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1921

D. Urankar, A. Pevec, J. Kosˇmrlj
FULL PAPER
Scheme 2. The synthesis of 2a–k from 1a–k and cis-[PtCl2-
(DMSO)2] in CH2Cl2 or CH3CN at room temperature. For details
see Table 1.
Table 1. The synthesis of the platinum(II) complexes 2a–k from the
diazene-conjugated pictri ligands (1a–k) and cis-[PtCl2(DMSO)2].
Figure 1. The diazene-appended pictri ligands with (a) an aromatic
structure and (b) an aliphatic structure for the linker.
those that have an aliphatic structure (Figure 1, b). Various
substituted phenyl rings were selected for R since the oxi-
dative properties[9,10] of the diazenes depend on the elec-
tronic nature of the group attached directly to the –N=N–
moiety. Our choice of the pictri ligand was also motivated
by the literature reports on platinum complexes with 1,2,3-
triazole[21] and pyridine,[2] as well as with those with di-2-
pyridylmethane,[22] all of which exhibit cytotoxic properties.
Results and Discussion
[a] Isolated pure product. [b] Measured in [D7]dmf. [c] Not deter-
mined because of insufficient solubility.
Synthesis and Characterization
The diazene-modified pictri ligands selected for this
study were easily prepared from the appropriate propargyl-
appended diazenes and picolylazide by copper-catalyzed
azide-alkyne 1,3-dipolar cycloaddition (click chemistry), as
previously reported (Scheme 1).[13,14]
1
Major changes in the H NMR spectra were observed
for the resonances of the proton ortho to the nitrogen atom
of the pyridine ring, the proton of the triazole unit and the
bridging methylene protons of the picolyl group upon the
coordination of 1a–k to platinum(II) and the formation of
2a–k. All of these signals shifted downfield (vide infra). The
chemical shifts of the protons for group R, the diazene moi-
ety and the linker remained virtually unchanged. For all
of the products 2, the geminal picolyl methylene protons
resonated as a singlet, which suggested dynamic behaviour
for the six-membered metallacycle that makes them equiva-
Scheme 1. The synthesis of ligands 1a–k.
A general and convenient synthetic route to platinum(II) lent on the NMR time scale. The 195Pt NMR chemical
complexes involved cis-[PtCl2(DMSO)2] as the platinum shifts for compounds 2a–i appeared in the region of –2203
source.[23,24] After stirring 1a–k with one equivalent of cis- to –2207 ppm (Table 1). The downfield shift for the above-
[PtCl2(DMSO)2] in CH2Cl2 or CH3CN for 1 to 8 d, the an- mentioned proton resonances and the 195Pt NMR chemical
alytically pure products 2a–k precipitated from the reaction shifts are consistent with the literature reports for the plati-
mixtures and were isolated in 39 to 83% yield (Scheme 2, num(II) coordination of the model pictri ligand.[17,18] NMR
Table 1). In addition to CH2Cl2 and CH3CN, EtOAc and spectra could not be obtained for compounds 2j–k because
acetone were also tested, but the first two solvents afforded of insufficient solubility of the complexes. The complexes
the best results in terms of the chemical yield and the purity were further characterized by electrospray ionization mass
of the products 2a–k.
spectrometry and micro-analysis.
1922
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 1921–1929

Diazenecarboxamide-Platinum(II) Complexes
The ligands (1) are red to yellow in colour because of is found for N2, which is 0.0670(12) Å out of the plane. The
the presence of the diazene moiety. The colour does not bond lengths for the coordination sphere are comparable to
significantly change upon coordination to platinum(II). The those found in other square-planar complexes of plati-
UV/Vis spectra for complexes 2a and 2e, along with those num(II).[26a] The sum of the platinum-containing angles
of ligands 1a and 1e, were recorded in a dmf solution (Fig- equal 360°, with only minor deviations from the ideal 90°
ures S1 and S2 in the Supporting Information). The corre- for the L–Pt–L (L = N, Cl) bond angles.
sponding complexes show strong absorptions at 280 to
The only noteworthy intra- or intermolecular interac-
300 nm in comparison to the absorptions for the ligands. tions in the solid state of 2a·CH3CN that the crystal struc-
Similar behaviour has been documented for 1-(2-picolyl)-4- ture revealed was the presence of the intermolecular C–
phenyl-1H-1,2,3-triazole.[17,18]
H···Pt contacts (Figure 3). In the boat conformation
Unfortunately, complexes 2a–k were insoluble in water adopted by the six-membered chelate, the hydrogen atom
and in most common organic solvents, with the exception (H6A) of the methylene carbon is oriented towards the
of N,N-dimethylformamide (dmf) and dimethyl sulfoxide platinum(II) centre of the contiguous molecule 2ai and has
(dmso). In deuterated N,N-dimethylformamide ([D7]dmf) a Pt···H distance of 2.699 Å and a C–H–Pt angle of 155.2°.
solutions, compounds 2a–k were stable for several weeks. Thus, in the solid state the two molecules are stabilized by a
When 2a was dissolved in deuterated dimethyl sulfoxide pair of intermolecular C–H···Pt contacts that form discrete
([D6]dmso) a rapid (within 24 h) ligand-exchange reaction associations. To the best of our knowledge, only a few sim-
took place with the formation of an uncoordinated pictri ilar examples of the intermolecular C–H···Pt interactions
ligand, which was confirmed by 1H NMR spectroscopy. are found in the literature.[26b]
The propensity of dmso to interact with platinum(II) by
ligand-substitution reactions has been documented.[18,25]
X-ray Crystal Structure
In general, it proved extremely difficult to grow crystals
for the complexes 2a–k that were suitable for crystallo-
graphic studies, and only in one instance – that of 2a –
were we successful. Compound 2a crystallized from boiling
acetonitrile as monosolvate 2a·CH3CN (see Exp. Section).
The result of the single-crystal X-ray analysis confirmed the
structural prediction depicted in Scheme 2.
The molecular structure for 2a with selected bond
lengths and angles is displayed in Figure 2. Ligand 1a
adopted a bidentate coordination mode through the tri-
azole N2 atom and the nitrogen atom of the pyridine and
formed a six-membered chelate ring, which adopted a boat-
like conformation. The coordination at the platinum(II)
centre is essentially square-planar. The largest deviation
from the best plane that contained the coordination sphere tions in 2a·CH3CN [symmetry code: (i) –x + 1, –y, –z + 1].
Figure 3. A diagram showing the intermolecular C–H···Pt interac-
Figure 2. The ORTEP plot of 2a from the X-ray crystal structure with the thermal ellipsoids at a 50% probability for the non-H atoms
and open circles for H-atoms. The hydrogen atoms are not labelled. Selected bond lengths [Å]: Pt1–N2 2.005(3), Pt1–N4 2.040(3), Pt1–
Cl1 2.2838(9), Pt1–Cl2 2.2899(8). Selected bond angles [°]: N2–Pt1–N4 89.30(10), N2–Pt1–Cl1 89.72(8), N2–Pt1–Cl2 175.34(8), N4–Pt1–
Cl1 178.26(8), N4–Pt1–Cl2 90.75(8), Cl1–Pt1–Cl2 90.34(3).
Eur. J. Inorg. Chem. 2011, 1921–1929
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1923

D. Urankar, A. Pevec, J. Kosˇmrlj
FULL PAPER
Monitoring the Coordination by NMR Spectroscopy
of K2[PtCl4] in a similar experiment only half of 1a was
consumed, suggested bidentate platinum coordination for
2a as shown in Scheme 3.
The Reaction of the Pictri Ligand with K2[PtCl4]
Although K2[PtCl4] has been extensively used for the
preparation of different diamminedichloridoplatinum(II)
chelates with bidentate ligands, including those that have a
pictri structural unit,[18] this platinum source was less at-
tractive for the preparation of 2a–k. The desired complex-
ation of 1a to form 2a was accompanied by the formation
of unidentified byproducts as shown by traces b and c in
Figure 4. The isolation of 2a from the above NMR experi-
ment by using solvent evaporation and/or precipitation with
less-polar solvents gave impure material – attempts at puri-
fication of the latter by recrystallization failed and resulted
in an even more complex mixture of products. This behav-
iour could be explained by the reactive nature of the di-
azene being incompatible with the specific reaction condi-
tions used in the above NMR experiment. It is worth noting
that the coordination of the diazene-appended propane-1,3-
diamine ligand to platinum(II) with different platinum pre-
cursors and reaction conditions has also been reported to
result in the decomposition of the ligand.[19]
In our initial experiment directed towards the synthesis
of 2, the chelation of the pictri donor with K2[PtCl4] as a
platinum source was examined in an NMR spectroscopy
experiment. A mixture of the selected ligand 1a and
K2[PtCl4] (1.1 equiv.) was dissolved in a mixture of [D7]dmf
and D2O (7:4, v/v) at 60 °C in the presence of air
(Scheme 3). The progress of the reaction was monitored at
1
60 °C by H NMR and 195Pt NMR spectroscopy. Within
1
3 h the H NMR spectra indicated an over 90% conversion
of 1a into a single product in which the resonances of the
proton ortho to the nitrogen atom of the pyridine ring (H-
6Py), the proton of the triazole ring (H-5triazole) and the
bridging methylene protons (CH2-Py) shifted downfield
from 8.69, 8.54 and 5.94 ppm (in 1a) to 9.31, 9.06 and
6.33 ppm, respectively (Figure 4). One 195Pt resonance was
observed at δ = –2207 ppm, which is consistent with an
N2Cl2 coordination environment.[27,28] These results, along
with the fact that when 1a was exposed to half an equiv.
The Reaction of the Pictri Ligand with cis-[PtCl2-
(DMSO)2]
In analogy to the above NMR experiment with
K2[PtCl4], a reaction between 1g and cis-[PtCl2(DMSO)2]
(1 equiv.) was conducted in [D7]dmf and monitored over
several days by NMR spectroscopy (Scheme 4). In this case,
1
overcrowded H NMR spectra with unresolved resonances
were seen (data not shown), which indicated a complex
transformation. The complexity of the reaction was illus-
trated by the 195Pt NMR spectroscopy (Figure 5). Within
20 min at 29 °C, compound 1g was almost completely coor-
dinated to the Pt centre, as is evident from the disappear-
Scheme 3. The reaction of 1a with K2[PtCl4] to form 2a, which was
monitored by NMR spectroscopy (Figure 4).
ance of the resonance at
δ = –3466 ppm for cis-
[PtCl2(DMSO)2] and the concomitant appearance of the
resonance at δ = –3050 ppm.
Scheme 4. The reaction of 1g with cis-[PtCl2(DMSO)2] to form 2g,
which was monitored by NMR spectroscopy (Figure 5).
The pictri donor can potentially offer three different ni-
trogen atoms for coordination to the metal, namely, N2 and
N3 of the triazole unit and the pyridine nitrogen atom.
Based on DFT calculations for 1-(2-picolyl)-4-phenyl-1H-
1,2,3-triazole, the natural bonding orbital (NBO) charges
follow the order N2 (–0.07) Ͼ N3 (–0.27) Ͼ pyridine nitro-
1
Figure 4. (a) Selected parts of the H NMR spectra of ligand 1a.
(b and c) The traces correspond to the reaction between 1a
(0.05 mmol) and K2[PtCl4] (1.1 equiv.) in [D7]dmf/D2O (0.7 mL/
0.4 mL) at 60 °C after 1 h and 3 h, respectively. (d) The H NMR
spectrum of an authentic sample of 2a, which was independently
prepared from 1a and cis-[PtCl2(DMSO)2] (see text).
1
1924
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 1921–1929

Diazenecarboxamide-Platinum(II) Complexes
acts with sterically nondemanding heterocyclic nitrogen
bases, L, to form trans-[PtCl2(DMSO)L], which later isom-
erizes very slowly to the cis form.[29] The 195Pt NMR chemi-
cal shift of –3050 ppm (Table 2, Figure 5, a) also supported
the proposed structure of the intermediate A as it is in good
agreement with the chemical shift of –3023 ppm that was
reported for trans-[PtCl2(DMSO)(pyridine)], whereas the
value for the cis- isomer is –2862 ppm (Table 2, Entries 2
and 3, respectively).[30] As evident from Figure 5, intermedi-
ate A quickly reacts to form a complex mixture of other
unidentified intermediates that resonate in the range of
–3055 to –2907 ppm. Over the course of several days the
intensities of these resonances waned, while the peak at
–2203 ppm that belongs to 2g waxed. The isomerization of
trans-[Pt(1g)Cl2(DMSO)] (A) to the cis-isomer is expected
from the reaction pathway, but its resonance in the 195Pt
NMR spectra could not be identified.
Figure 5. The course of the reaction between 1g (0.1 mmol) and
cis-[PtCl2(DMSO)2] (0.1 mmol) in [D7]dmf (0.7 mL) at 29 °C was
monitored by 195Pt NMR spectroscopy (Scheme 4). Only those
parts of the spectra of interest are shown (from –2000 to –2400 ppm
and from –2800 to –3600 ppm) after: (a) 2 min, (b) 20 min, (c)
1.5 d, (d) 4 d and (e) 17 d. The total spectral window measured
spanned from –1800 to –4000 ppm.
A Comparison between the 1-(2-Picolyl)-1,2,3-triazolyl and
1-(2-Aminoethyl)-1,2,3-triazolyl Ligands
The above results clearly demonstrate that 1,2,3-triazole,
which is functionalized at position 1 with an appropriate
pendant group (e.g. picolyl), can form stable chelates of
platinum(II) with the triazole N2 atom being involved in
the coordination. On the other hand, it has been previously
reported that this is not the case for analogous compounds
that have an aminoalkyl pendant group, as exemplified by
1-(2-aminoethyl)-1,2,3-triazole (3) (Figure 6).[21] The differ-
ence in the complexation affinity of the pyridyl versus the
gen atom (–0.48).[17] Thus, considering the fact that the pyr-
idine nitrogen atom is a significantly more electron-rich do-
nor, its participation in the initial monodentate coordina-
tion to form intermediate A, trans-[Pt(1g)Cl2(DMSO)]
(Scheme 4, Table 2, Entry 1), was assumed. This was sup-
ported by the literature reports that cis-[PtCl2(DMSO)2] re-
Table 2. The structures and the 195Pt NMR spectroscopic data for aminoalkyl functionalized triazoles has been recently ad-
some of the platinum(II) complexes.
dressed theoretically and was attributed to the distinct mag-
nitude of the π-back-donation of the metal d electrons to
the anti-bonding orbitals of the ligand.[17] In order to shed
some light experimentally on the coordination of the 1-(2-
aminoethyl)-1,2,3-triazole ligand to platinum(II), we re-
acted 4 (Figure 6), a closely related analogue of 1g, with
cis-[PtCl2(DMSO)2] in [D7]dmf at 29 °C (Scheme 5). The
progress of the reaction was monitored over several days by
195Pt NMR spectroscopy (Figure 7). An instant reaction
was observed with the formation of a single species B reso-
nating at δ = –3129 ppm, which later transformed very
slowly into a new species C that showed a broad singlet at
δ = –3082 ppm. Based on a similar consideration to that
described above for intermediate A,[29] the structures of B
and C were tentatively assigned to trans- and cis-[Pt(4)-
Cl2(DMSO)], respectively. In these complexes compound 4
is monodentately coordinated to platinum(II) through the
aminoalkyl nitrogen atom (Table 2, Entries 4 and 5, respec-
tively). The 195Pt NMR chemical shifts and the line shape
[a] Relative to Na2[PtCl6]. [b] This work (measured in [D7]dmf). [c]
Ref.[30] (measured in [D6]dmso). [d] Ref.[31] (measured in [D6]dmso).
Figure 6. The structures of the 1-(2-aminoethyl)-1,2,3-triazolyl li-
gands 3 and 4.
Eur. J. Inorg. Chem. 2011, 1921–1929
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1925

D. Urankar, A. Pevec, J. Kosˇmrlj
FULL PAPER
of the resonances for the trans- and cis-species, B and C, 1 to platinum(II) was monitored by 1H and 195Pt NMR
are consistent with those reported by Farrell and co- spectroscopy and indicated a complex reaction coordinate
workers, who studied the isomerization of [trans- with the presence of several intermediates. Although some
{PtCl2(DMSO)}2NH2(CH2)4NH2] to the dinuclear cis-de- tentative explanations have been provided for a few of the
rivative (Table 2, Entries 6 and 7).[28,31] Within 17 d no new observations, the in-depth mechanistic study of the platin-
195Pt NMR peak appeared in the spectra, as shown in Fig- um complexation by the pictri unit is beyond the scope of
ure 7. In comparison to the reaction with 1g (vide supra), this work and will be the subject of another paper. The
a remarkably clean reaction took place between cis- diamminedichloridoplatinum(II) structure of 2 was con-
[PtCl2(DMSO)2] and ligand 4, as can be inferred from the firmed by single-crystal X-ray diffraction analysis for 2a.
195Pt NMR spectra.
Discrete associations were found in the solid state of 2a
where a pair of the complexes was stabilized by a pair of
short intermolecular contacts (2.699 Å) between the meth-
ylene protons of the picolyl group and the platinum centre.
The work presented herein could easily be adopted in the
synthesis of other organic-inorganic conjugates of wide-
spread interest owing to the mild and selective chemistry
required for the introduction of the picolyl-triazole binding
unit into the organic compounds and its affinity for several
metal ions.
Scheme 5. The reaction of 4 with cis-[PtCl2(DMSO)2], which was
monitored by NMR spectroscopy (Figure 7). For the complete
structures of B and C see Table 2.
Experimental Section
General: The reagents and solvents were used as purchased from
Fluka, Aldrich or Alfa Aesar. Ligands 1a–d,[13] 1e–k,[14] 1-(2-
aminoethyl)-4-phenyl-1H-1,2,3-triazole (3)[14] and N-{[1-(2-amino-
ethyl)-1H-1,2,3-triazol-4-yl]methyl}-2-(4-chlorophenyl)diazenecarb-
oxamide (4),[14] as well as cis-[PtCl2(DMSO)2],[23] were prepared by
known procedures. The NMR spectra were recorded at 302 K (un-
less otherwise indicated) with a Bruker Avance DPX 300 spectrom-
eter operating at 300 MHz, 282 MHz, 75 MHz and 64 MHz for
Figure 7. The course of the reaction (Scheme 5) between
4
(0.1 mmol) and cis-[PtCl2(DMSO)2] (0.1 mmol) in [D7]dmf
(0.7 mL) at 29 °C was monitored by 195Pt NMR spectroscopy. Only
the parts of the spectra of interest are shown (from –2000 to
–2400 ppm and from –2800 to –3600 ppm) after: (a) 2 min, (b) 1.5 d
and (c) 17 d. The total spectral window measured spanned from
–1800 to –4000 ppm.
1
1H, 19F, 13C and 195Pt, respectively. The H and 13C NMR spectra
were referenced with respect to TMS as the internal standard.
Some of the 13C NMR chemical shifts were determined relative to
the upfield 13C NMR signal of the solvent [D7]dmf at δ = 30.1 ppm.
The 195Pt and 19F NMR spectra were referenced with respect to
Na2[PtCl6] (325 mg/0.65 mL D2O, T = 302 K)[32] and CCl3F as the
external standards, respectively, at δ = 0 ppm. The 195Pt NMR spec-
tra were recorded with a 75 kHz spectral width, 1000–70000
number of scans and a relaxation delay of 0.02 s between the acqui-
sitions. A line broadening of 100 Hz was applied. The chemical
shifts are given on the δ scale (ppm). The coupling constants (J)
are given in Hertz. The multiplicities are indicated as follows: s
(singlet), d (doublet), t (triplet), q (quartet), m (multiplet) and br
(broadened). The high-resolution mass spectra were obtained with
a Q-TOF Premier instrument. The infrared spectra were recorded
with a BIO-RAD Excalibur Series spectrophotometer by using
samples in potassium bromide disks. The far infrared spectra were
recorded with a Perkin–Elmer System 2000 FTIR spectrophotome-
ter by using samples in nujol. The UV/Vis spectra were recorded
with a Varian Cary 50 UV/Vis Spectrophotometer. The elemental
analyses (C, H, N) were performed with a Perkin–Elmer 2400
Series II CHNS/O Analyzer. The melting points were determined
with a Kofler block.
All of the attempts to isolate species B and C failed, as
illustrated by the following experiment: a mixture of 4 and
cis-[PtCl2(DMSO)2] (1 equiv.) was stirred in CH2Cl2 in the
presence of air for 20 min. During this time the reactants
dissolved completely and formed a precipitate. As soon as
the precipitate was collected by filtration it turned into a
gummy, black material, which the 1H NMR spectral analy-
sis indicated was a complex mixture of products. Unfortu-
nately, these could not be identified.
Conclusions
In continuation of our research on platinum(II) coordi-
nation with the model pictri ligand 1-(2-picolyl)-4-phenyl-
1H-1,2,3-triazole,[17] we have applied this chemistry to more
complex analogues, namely, pictri-appended diazenecarb-
oxamides (1). We have demonstrated that the pictri unit in
1 allows bidentate coordination through the 1,2,3-triazole
N2 and the pyridine nitrogen atom under mild reaction
conditions to form stable diamminedichloridoplatinum(II)
chelates (2). This is an important feature for reactive moie-
The NMR Spectroscopy Experiment for the Reaction of 1a with
K2[PtCl4] to form 2a: Compound 1a (24.1 mg, 0.050 mmol) was
dissolved in a mixture of [D7]dmf (0.7 mL) and D2O (0.4 mL) in
an NMR tube and the 1H NMR spectrum was recorded (Figure 4,
a). K2[PtCl4] (22.8 mg, 0.055 mmol) was added and the reaction
was monitored at 60 °C by 1H NMR spectroscopy (Figure 4, b and
ties such as diazenecarboxamides.[10,19] The coordination of c) and by 195Pt NMR spectroscopy.
1926 Eur. J. Inorg. Chem. 2011, 1921–1929
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Diazenecarboxamide-Platinum(II) Complexes
The Synthesis and Characterization of Dichloridoplatinum(II) Com-
plexes 2a–k
160.6 ppm. 195Pt NMR (64 MHz, [D7]dmf): δ = –2206 ppm. IR
(KBr): ν = 3420, 3119, 1727, 1608, 1490, 1189, 1156, 1088, 842,
˜
771 cm–1. HRMS (ESI+) calcd. for C22H1835Cl3N7NaO2194Pt+ ([M
+ Na]+): 734.0112; found 734.0139. C22H18Cl3N7O2Pt (713.86):
calcd. C 37.01, H 2.54, N 13.73; found C 37.24, H 2.17, N 13.34.
General Procedure: Ligand 1 (0.30 mmol) and cis-[PtCl2(DMSO)2]
(126.7 mg, 0.30 mmol) were mixed in dichloromethane (0.5 mL) or
acetonitrile (1.5 mL) as indicated in Table 1. The reactants were
completely dissolved after 1 h of stirring at room temperature. The
reaction was stirred in the dark for the time indicated in Table 1.
The precipitate was filtered off and washed with dichloromethane
(0.5 mL) or acetonitrile (0.5 mL) and dried to give the analytically
(CHN and NMR) pure complex 2. The yields are given in Table 1.
The NMR spectral and analytical data for 2 are listed below.
Complex 2a: Red solid, m.p. 201–203 °C. 1H NMR (300 MHz,
[D7]dmf): δ = 5.32 (s, 2 H, CH2), 6.31 (s, 2 H, CH2), 6.96 (dd, J =
1.8, 8.0 Hz, 1 H, Ar-H), 7.39 (dd, J = 8.1, 8.1 Hz, 1 H, Ar-H), 7.47
(br. d, J = 8.4 Hz, 1 H, Ar-H), 7.60 (br. s, 1 H, Ar-H), 7.72 (dd, J
= 6.1, 6.1 Hz, 1 H, Ar-H), 7.97 (br. d, J = 7.2 Hz, 1 H, Ar-H), 8.09
(d, J = 8.6 Hz, 2 H, Ar-H), 8.15 (d, J = 8.6 Hz, 2 H, Ar-H), 8.28
(ddd, J = 1.4, 7.7, 7.7 Hz, 1 H, Ar-H), 8.97 (s, 1 H, triazole-H),
9.28 (br. d, J = 4.9 Hz, 1 H, Ar-H), 11.07 (br. s, 1 H, N-H) ppm.
13C NMR (75 MHz, [D7]dmf): δ = 55.5, 61.7, 107.1, 111.0, 113.2,
124.5, 124.7 (q, J = 273.0 Hz), 127.3, 127.4, 127.7 (q, J = 3.8 Hz),
129.4, 130.8, 133.7 (q, J = 23.2 Hz), 140.1, 141.3, 145.8, 151.4,
154.3, 154.4, 159.3, 160.4 ppm. 195Pt NMR (64 MHz, [D7]dmf): δ
1
Complex 2d: Orange solid, m.p. 206–210 °C. H NMR (300 MHz,
[D7]dmf): δ = 5.32 (s, 2 H, CH2), 6.32 (s, 2 H, CH2), 6.97 (br. d, J
= 8.0 Hz, 1 H, Ar-H), 7.39 (dd, J = 8.1, 8.1 Hz, 1 H, Ar-H), 7.48
(br. d, J = 8.2 Hz, 1 H, Ar-H), 7.61 (br. s, 1 H, Ar-H), 7.73 (br.
dd, J = 6.3 Hz, 1 H, Ar-H), 7.98 (d, J = 7.5 Hz, 1 H, Ar-H), 8.18
(d, J = 8.9 Hz, 2 H, Ar-H), 8.29 (br. dd, J = 7.7 Hz, 1 H, Ar-H),
8.57 (d, J = 8.9 Hz, 2 H, Ar-H), 8.97 (br. s, 1 H, triazole-H), 9.28
(br. d, J = 5.3 Hz, 1 H, Ar-H), 11.11 (br. s, 1 H, N-H) ppm. 13C
NMR (75 MHz, [D7]dmf): δ = 55.5, 61.8, 107.1, 111.1, 113.2, 124.8,
125.9, 127.3, 127.4, 129.4, 130.8, 140.1, 141.3, 145.8, 150.9, 151.5,
154.4, 155.3, 159.4, 160.2, 163.1 ppm. 195Pt NMR (64 MHz, [D7]-
dmf): δ = –2207 ppm. IR (KBr): ν = 3449, 1725, 1609, 1525, 1346,
˜
1193, 1159, 864, 767 cm–1. HRMS (ESI–) calcd. for
C22H17N8O435Cl2194Pt– ([M – H]–): 721.0377; found 721.0365.
C22H18Cl2N8O4Pt (724.41): calcd. C 36.48, H 2.50, N 15.47; found
C 36.87, H 2.16, N 15.09.
Complex 2e: Orange solid, m.p. Ͼ300 °C. 1H NMR (300 MHz,
[D7]dmf): δ = 4.73 (d, J = 6.0 Hz, 2 H, CH2), 6.29 (s, 2 H, CH2),
7.72 (dd, J = 6.1 Hz, 1 H, Ar-H), 7.95 (d, J = 7.3 Hz, 1 H, Ar-H),
= –2207 ppm. IR (KBr): ν = 3301, 1724, 1601, 1487, 1420, 1321,
˜
1159, 1123, 1062, 849, 780, 687 cm–1. IR (nujol): ν = 344 (Pt–Cl 8.05 (s, 4 H, Ar-H), 8.28 (ddd, J = 1.2, 7.7, 7.7 Hz, 1 H, Ar-H),
˜
stretching) cm–1. HRMS (ESI) calcd. for C23H1935Cl2F3N7O2194Pt+
([M
H]+): 746.0556; found 746.0589. C23H18Cl2F3N7O2Pt t, J = 5.7 Hz, 1 H, N-H) ppm. 13C NMR (75 MHz, [D7]dmf): δ =
8.81 (s, 1 H, triazole-H), 9.27 (d, J = 5.1 Hz, 1 H, Ar-H), 9.35 (br.
+
(747.41): calcd. C 36.96, H 2.43, N 13.12; found C 36.63, H 2.45,
N 12.84.
36.3, 55.4, 124.3, 124.7 (q, J = 272 Hz), 127.3, 127.6 (q, J = 3.8 Hz),
128.5, 133.6 (q, J = 32.5 Hz), 141.3, 147.0, 151.6, 154.3, 154.4,
163.5, 163.5 ppm. 195Pt NMR (64 MHz, [D7]dmf): δ = –2203 ppm.
Crystallization of 2a (2a·CH3CN): Compound 2a (160.0 mg) was
dissolved in boiling acetonitrile (400 mL). The solution was fil-
tered, cooled to room temperature and the solvent slowly evapo-
rated over several weeks to approximately 100 mL. The yellow-
orange crystals of 2a·CH3CN (106.1 mg, 63% from 2a) were col-
lected by filtration: m.p. Ͼ350 °C. 195Pt NMR (64 MHz, [D7]dmf):
IR (KBr): ν = 3345, 1720, 1324, 1130, 1065 cm–1. HRMS (ESI–)
˜
calcd. for C17H1535Cl2F3N7O194Pt– [M + 2H – H]–: 654.0294; found
654.0325. C17H14Cl2F3N7OPt (655.32): calcd. C 31.16, H 2.15, N
14.96; found C 31.18, H 2.08, N 14.79.
Complex 2f: Yellow solid, m.p. Ͼ300 °C. 1H NMR (300 MHz, [D7]-
δ = –2207 ppm. C23H18Cl2F3N7O2Pt·CH3CN (788.47): calcd. C dmf): δ = 4.71 (d, J = 5.9 Hz, 2 H, CH2), 6.29 (s, 2 H, CH2), 7.42–
38.08, H 2.68, N 14.21; found C 38.32, H 2.90, N 14.34.
7.53 (m, 2 H, Ar-H), 7.70 (ddd, J = 1.3, 7.5, 7.5 Hz, 1 H, Ar-H),
7.88–8.20 (m, 3 H, Ar-H), 8.27 (ddd, J = 1.4, 7.7, 7.7 Hz, 1 H, Ar-
H), 8.80 (s, 1 H, triazole-H), 9.18–9.34 (m, 2 H, Ar-H, N-H) ppm.
13C NMR (75 MHz, [D7]dmf): δ = 36.3, 55.4, 117.2, 117.5, 126.3,
126.4, 127.3, 128.5, 141.3, 147.2, 148.9, 149.0, 151.6, 154.5, 163.6,
164.4, 167.8 ppm. 19F NMR (282 MHz, [D7]dmf): δ = –107.9 (m)
1
Complex 2b: Orange solid, m.p. 240–243 °C. H NMR (300 MHz,
[D7]dmf): δ = 5.32 (s, 2 H, CH2), 6.31 (s, 2 H, CH2), 6.98 (dd, J =
1.8, 8.0 Hz, 1 H, Ar-H), 7.39 (dd, J = 8.1, 8.1 Hz, 1 H, Ar-H), 7.49
(br. d, J = 8.0 Hz, 1 H, Ar-H), 7.60 (br. s, 1 H, Ar-H), 7.71 (dd, J
= 6.6, 6.6 Hz, 1 H, Ar-H), 7.96 (br. d, J = 7.6 Hz, 1 H, Ar-H), 8.28
(ddd, J = 1.4, 7.7, 7.7 Hz, 1 H, Ar-H), 8.96 (s, 1 H, triazole-H),
9.28 (br. d, J = 5.7 Hz, 1 H, Ar-H), 11.37 (br. s, 1 H, N-H) ppm.
13C NMR (75 MHz, [D7]dmf): δ = 55.5, 61.8, 107.3, 111.4, 113.4,
127.3, 127.4, 127.5 (br), 129.4, 130.8, 137.3 (br), 140.0, 140.8 (br),
141.3, 144.3 (br), 145.8, 151.5, 154.4, 159.1, 159.4 ppm. 195Pt NMR
ppm. 195Pt NMR (64 MHz, [D ]dmf): δ = –2203 ppm. IR (KBr): ν
˜
7
= 3358, 3119, 1717, 1501, 1227, 1140, 851, 772 cm–1. HRMS (ESI–)
calcd. for C16H1535Cl2FN7O194Pt– [M + 2H – H]–: 604.0326; found
604.0338. C16H14Cl2FN7OPt (605.31): calcd. C 31.75, H 2.33, N
16.20; found C 31.37, H 2.43, N 15.83.
(64 MHz, [D ]dmf): δ = –2206 ppm. IR (KBr): ν = 3515, 3414, Complex 2g: Ochre solid, m.p. Ͼ300 °C. 1H NMR (300 MHz, [D7]-
˜
7
3151, 1730, 1607, 1519, 1490, 1400, 1223, 1159, 1136, 1028, 974,
dmf): δ = 4.70 (d, J = 5.9 Hz, 2 H, CH2), 6.30 (s, 2 H, CH2), 7.70
(d, J = 8.7 Hz, 2 H, Ar-H), 7.85 (d, J = 8.7 Hz, 2 H, Ar-H), 7.95
771 cm–1. HRMS (ESI+) calcd. for C22H1435Cl2F5N7NaO2194Pt+
([M + Na]+): 790.0031; found 790.0034. C22H14Cl2F5N7O2Pt (d, J = 7.3 Hz, 1 H, Ar-H), 8.30 (dd, J = 7.7, 7.7 Hz, 1 H, Ar-H),
(769.37): calcd. C 34.34, H 1.83, N 12.74; found C 34.04, H 2.06,
N 12.36.
8.80 (s, 1 H, triazole-H), 9.22–9.34 (m, 2 H, Ar-H, N-H) ppm. 13C
NMR (75 MHz, [D7]dmf): δ = 36.3, 55.4, 125.4, 127.3, 128.4, 130.5,
139.1, 141.3, 147.1, 150.7, 151.5, 154.4, 163.5 ppm. 195Pt NMR
1
Complex 2c: Orange solid, m.p. 229–232 °C. H NMR (300 MHz,
(64 MHz, [D ]dmf): δ = –2203 ppm. IR (KBr): ν = 3360, 1721,
˜
7
[D7]dmf): δ = 5.31 (s, 2 H, CH2), 6.32 (s, 2 H, CH2), 6.94 (br. d, J
= 6.5 Hz, 1 H, Ar-H), 7.37 (dd, J = 8.1, 8.1 Hz, 1 H, Ar-H), 7.48
(br. d, J = 8.4 Hz, 1 H, Ar-H), 7.61 (br. s, 1 H, Ar-H), 7.67–7.81
(m, 3 H, Ar-H), 7.93–8.05 (m, 3 H, Ar-H), 8.28 (dd, J = 7.2, 7.2 Hz,
1 H, Ar-H), 8.98 (s, 1 H, triazole-H), 9.27 (br. d, J = 5.4 Hz, 1 H,
1489,
1152,
843
cm–1.
HRMS
(ESI–)
calcd.
for
C16H1535Cl3N7O194Pt– [M + 2H – H]–: 620.0030; found 620.0050.
C16H14Cl3N7OPt (621.77): calcd. C 30.91, H 2.27, N 15.77; found
C 30.53, H 2.42, N 15.39.
Ar-H), 10.98 (br. s, 1 H, N-H) ppm. 13C NMR (75 MHz, [D7]dmf): Complex 2h: Ochre solid, m.p. Ͼ300 °C. 1H NMR (300 MHz, [D7]-
δ = 55.5, 61.8, 107.1, 110.9, 113.2, 125.6, 127.3, 127.4, 129.4, 130.6, dmf): δ = 4.75 (d, J = 6.0 Hz, 2 H, CH2), 6.42 (s, 2 H, CH2), 7.72
130.7, 139.4, 140.4, 141.3, 145.8, 150.8, 151.5, 154.4, 159.3, (dd, J = 6.4 Hz, 1 H, Ar-H), 7.95 (d, J = 7.3 Hz, 1 H, Ar-H), 8.08
Eur. J. Inorg. Chem. 2011, 1921–1929
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1927

D. Urankar, A. Pevec, J. Kosˇmrlj
FULL PAPER
(d, J = 8.9 Hz, 2 H, Ar-H), 8.31 (dd, J = 7.6, 7.6 Hz, 1 H, Ar-H),
8.52 (d, J = 8.9 Hz, 2 H, Ar-H), 8.90 (s, 1 H, triazole-H), 9.30 (d,
J = 5.5 Hz, 1 H, Ar-H), 9.44 (br. t, J = 4.9 Hz, 1 H, N-H) ppm.
13C NMR (75 MHz, [D7]dmf): δ = 36.4, 55.4, 124.6, 125.9, 127.4,
128.5, 141.4, 147.0, 150.7, 151.6, 154.5, 155.3, 163.3 ppm. 195Pt
Supporting Information (see footnote on the first page of this arti-
cle): The UV/Vis spectra for compounds 1a, 1e, 2a and 2e.
Acknowledgments
NMR (64 MHz, [D ]dmf): δ = –2204 ppm. IR (KBr): ν = 3314,
˜
7
3268, 3128, 1724, 1525, 1347, 866, 768 cm–1. HRMS (ESI–) calcd.
for C16H1435Cl2N8O3194Pt– [M + 2H – H]–: 631.0271; found
631.0290. C16H14Cl2N8O3Pt (632.32): calcd. C 30.39, H 2.23, N
17.72; found C 30.19, H 2.32, N 17.42.
This study was supported by the Ministry of Higher Education,
Science and Technology of the Republic of Slovenia and the Slov-
enian Research Agency (P1-0230–0103). The authors thank Dr.
ˇ
Bogdan Kralj and Dr. Dusan Zigon (Mass Spectrometry Center,
ˇ
Jozef Stefan Institute, Ljubljana, Slovenia) for the mass spectra
ˇ
measurements. This work was also partially supported through the
infrastructure of the EN-FIST Centre of Excellence, Ljubljana.
Complex 2i: Ochre solid, m.p. Ͼ300 °C. 1H NMR (300 MHz,
[D7]dmf): δ = 2.43 (s, 3 H, CH3), 4.70 (d, J = 5.9 Hz, 2 H, CH2),
6.29 (s, 2 H, CH2), 7.45 (d, J = 8.1 Hz, 2 H, Ar-H), 7.65–7.74 (m,
3 H, Ar-H), 7.95 (d, J = 6.9 Hz, 1 H, Ar-H), 8.27 (ddd, J = 1.4,
7.7, 7.7 Hz, 1 H, Ar-H), 8.79 (s, 1 H, triazole-H), 9.15 (br. t, J =
5.4 Hz, 1 H, N-H), 9.18 (d, J = 4.8 Hz, 1 H, Ar-H) ppm. 13C NMR
(75 MHz, [D7]dmf): δ = 21.4, 36.3, 55.4, 123.8, 127.3, 128.41,
128.42, 130.8, 141.3, 145.1, 147.3, 150.3, 151.6, 154.4, 163.8 ppm.
[1] http://www.cancer.gov/.
[2] L. Kelland, Nat. Rev. Cancer 2007, 7, 573–584.
[3] a) B. Lippert (Ed.), Cisplatin: Chemistry and Biochemistry of a
Leading Anticancer Drug, Wiley-VCH, Zürich, 1999; b) Y.
Jung, S. Lippard, Chem. Rev. 2007, 107, 1387–1407; c) A. V.
Klein, T. W. Hambley, Chem. Rev. 2009, 109, 4911–4920; d) J.
Reedijk, Eur. J. Inorg. Chem. 2009, 1303–1312; e) B. W. Harper,
A. M. Krause-Heuer, M. P. Grant, M. Manohar, K. B. Garbut-
cheon-Singh, J. R. Aldrich-Wright, Chem. Eur. J. 2010, 16,
7064–7077.
195Pt NMR (64 MHz, [D ]dmf): δ = –2204 ppm. IR (KBr): ν =
˜
7
3360, 3336, 3127, 1717, 1505, 1153, 831, 766 cm–1. HRMS (ESI–)
calcd. for C17H1835Cl2N7O194Pt– [M + 2H – H]–: 600.0577; found
600.0600. C17H17Cl2N7OPt (601.35): calcd. C 33.95, H 2.85, N
16.30; found C 33.57, H 2.93, N 15.98.
[4] a) L. R. Kelland, Drugs 2000, 1–8; b) M. A. Fuertes, C.
Alonso, J. M. Pérez, Chem. Rev. 2003, 103, 645–662.
[5] a) P. Mistry, L. R. Kelland, G. Abel, S. Sidhar, K. R. Harrap,
Br. J. Cancer 1991, 64, 215–220; b) A. Casini, A. Scozzafava,
C. T. Supuran, Environ. Health Perspect. 2002, 110, 801–806;
c) G. K. Balendiran, R. Dabur, D. Fraser, Cell Biochem. Funct.
2004, 22, 343–352.
Complex 2j: Ochre solid, m.p. Ͼ300 °C. IR (KBr): ν = 3350, 3117,
˜
1708, 1503, 1143, 1022, 841, 770 cm–1. The NMR spectra could not
be obtained because the complex was insufficiently soluble. HRMS
(ESI–) calcd. for C17H1835Cl2N7O2194Pt– [M + 2H – H]–: 616.0526;
found 616.0498. C17H17Cl2N7O2Pt (617.35): calcd. C 33.07, H 2.78,
N 15.88; found C 32.75, H 2.93, N 15.56.
[6] D. Gibson, Dalton Trans. 2009, 10681–10689.
Complex 2k: Yellow solid, m.p. Ͼ300 °C. IR (KBr): ν = 3354, 3118,
˜
[7] a) R. Millet, S. Urig, J. Jacob, E. Amtmann, J.-P. Moulinoux,
S. Gromer, K. Becker, E. Davioud-Charvet, J. Med. Chem.
2005, 48, 7024–7039; b) W. H. Ang, I. Khalaila, C. S. Allar-
dyce, L. Juillerat-Jeanneret, P. J. Dyson, J. Am. Chem. Soc.
2005, 127, 1382–1383.
[8] a) R. Morphy, Z. Rankovic, J. Med. Chem. 2005, 48, 6523–
6543; b) A. Cavalli, M. L. Bolognesi, J. Med. Chem. 2009, 52,
7339–7359; c) B. Meunier, Acc. Chem. Res. 2008, 41, 69–77.
[9] J. Kosˇmrlj, M. Kocˇevar, S. Polanc, J. Chem. Soc. Perkin Trans.
1 1998, 3917–3919.
1717, 1493, 768 cm–1. The NMR spectra could not be obtained
because the complex was insufficiently soluble. HRMS (ESI–)
calcd. for C16H1635Cl2N7O194Pt– [M + 2H – H]–:586.0420; found
586.0439. C16H15Cl2N7OPt (587.32): calcd. C 32.72, H 2.57, N
16.69; found C 32.35, H 2.63, N 16.44.
X-ray Structure Determination of 2a·CH3CN: Crystal data:
C23H18Cl2F3N7O2Pt·CH3CN, M = 788.49, triclinic, space group
¯
P1, a = 8.33230(10) Å, b = 10.0246(2) Å, c = 18.7318(4) Å, α =
95.3617(11)°, 90.1259(12)°, 113.7736(11)°, V =
[10] J. Kosˇmrlj, M. Kocˇevar, S. Polanc, Synlett 2009, 2217–2235.
[11] S. Jakopec, K. Dubravcˇic´, S. Polanc, J. Kosˇmrlj, M. Osmak,
Toxicol. vitro 2006, 20, 217–226.
β
=
γ
=
1424.23(5) Å3, Z = 2, Dc = 1.839 gcm–3, μ = 5.172 mm–1. A yellow
block of compound 2a·CH3CN with dimensions of
0.10ϫ0.05ϫ0.05 mm3 was glued to a glass thread. The diffraction
data were collected with a Nonius Kappa CCD diffractometer with
an area detector at room temperature. A graphite monochromated
Mo-Kα radiation source (λ = 0.71072 Å) was employed. A total of
10993 reflections were measured, 6408 were independent and 5749
[IϾ2σ(I)] were considered observed. The structure was solved by
direct methods using SIR-92[33] and refined with a full-matrix least-
squares procedure based on F2 using SHELXL-97.[34] All of the
non-hydrogen atoms were refined anisotropically. All of the C–H
hydrogen atoms were included in the model at geometrically calcu-
lated positions and refined using a riding model. The hydrogen
atom bonded to nitrogen N5 was visible in the last stages of the
refinement and was refined with the constrained N–H bond length
(0.86 Å) and isotropic thermal parameters (1.2 times the thermal
parameter of the attached nitrogen atom). The final R indices
[IϾ2σ(I)] R1 = 0.0249, wR2 = 0.0561, and (all data) R1 = 0.0313,
wR2 = 0.0561 were found.
[12] a) M. Osmak, T. Bordukalo, J. Kosˇmrlj, M. Kvajo, Z. Mari-
janovic´, D. Eljuga, S. Polanc, Neoplasma 1999, 46, 201–206; b)
M. Osmak, T. Bordukalo, B. Jernej, J. Kosˇmrlj, S. Polanc, Anti-
Cancer Drugs 1999, 10, 853–859; c) M. Osmak, T. Bordukalo,
A. Ambriovic´ Ristov, B. Jernej, J. Kosˇmrlj, S. Polanc, Neo-
plasma 2000, 47, 390–395; d) L. Pieters, J. Kosˇmrlj, R. Len-
arsˇicˇ, M. Kocˇevar, S. Polanc, Arkivoc 2001, 5, 42–50; e) D. Mo-
skatelo, A. Benjak, V. Laketa, S. Polanc, J. Kosˇmrlj, M. Osmak,
Chemotherapy 2002, 48, 36–41; f) D. Moskatelo, S. Polanc, J.
Kosˇmrlj, L. Vukovic´, M. Osmak, Pharmacol. Toxicol. 2002, 91,
ˇ
258–263; g) T. Cimbora-Zovko, S. Bombek, J. Kosˇmrlj, L. Kov-
acˇicˇ, S. Polanc, A. Katalinic´, M. Osmak, Drug Dev. Res. 2004,
61, 95–100; h) S. Jakopec, K. Dubravcˇic´, A. Brozovic´, S. Pol-
anc, M. Osmak, Cell Biol. Toxicol. 2006, 22, 61–71; i) I. Mar-
ˇ
ˇ
tin-Kleiner, S. Bombek, J. Kosˇmrlj, B. Cupic´, T. Cimbora-
Zovko, S. Jakopec, S. Polanc, M. Osmak, J. Gabrilovac, Tox-
icol. vitro 2007, 21, 1453–1459.
[13] D. Urankar, J. Kosˇmrlj, J. Comb. Chem. 2008, 10, 981–985.
[14] D. Urankar, M. Steinbücher, J. Kosjek, J. Kosˇmrlj, Tetrahedron
2010, 66, 2602–2613.
[15] a) T. L. Mindt, H. Struthers, L. Brans, T. Anguelov, C.
Schweinsberg, V. Maes, D. Tourwé, R. Schibli, J. Am. Chem.
Soc. 2006, 128, 15096–15097; b) H. Struthers, T. L. Mindt, R.
Schibli, Dalton Trans. 2010, 39, 675–696.
CCDC-692994 contains the supplementary crystallographic data
for 2a·CH3CN. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
1928
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 1921–1929

Diazenecarboxamide-Platinum(II) Complexes
[16] a) W. S. Brotherton, H. A. Michaels, J. T. Simmons, R. J. Clark,
N. S. Dalal, L. Zhu, Org. Lett. 2009, 11, 4954–4957; b) J. D.
Crowley, P. H. Bandeen, L. R. Hanton, Polyhedron 2010, 29,
70–83; c) Y. Fu, Y. Liu, C. Zhong, H. Li, X. G. Chen, J. G.
Qin, Chin. J. Inorg. Chem. 2010, 26, 1133–1140; d) G.-C. Ku-
ang, H. A. Michaels, J. T. Simmons, R. J. Clark, L. Zhu, J. Org.
Chem. 2010, 75, 6540–6548; e) S.-Q. Bai, S. Leelasubcharoen,
X. Chen, L. L. Koh, J.-L. Zuo, T. S. A. Hor, Cryst. Growth Des.
2010, 10, 1715–1720; f) J. D. Crowley, P. H. Bandeen, Dalton
Trans. 2010, 39, 612–623; g) S.-Q. Bai, J. Y. Kwang, L. L. Koh,
D. J. Young, T. S. A. Hor, Dalton Trans. 2010, 39, 2631–2636;
h) D. Urankar, A. Pevec, I. Turel, J. Kosˇmrlj, Cryst. Growth
Des. 2010, 10, 4920–4927.
[24] I. Eryazici, C. N. Moorefield, G. R. Newkome, Chem. Rev.
2008, 108, 1834–1895.
[25] a) S. J. S. Kerrison, P. J. Sadler, J. Chem. Soc., Chem. Commun.
1977, 861–863; b) W. I. Sundquist, K. J. Ahmed, L. S. Hollis,
S. J. Lippard, Inorg. Chem. 1987, 26, 1524–1528; c) J. Yoo, J.-
H. Kim, Y. S. Sohn, Y. Do, Inorg. Chim. Acta 1997, 263, 53–
60.
[26] a) Cambridge Structural Database (version 5.31.1, update May
2010); b) Search for platinum(II) complexes that have a square
planar environment with C–H···Pt separations in the range of
2.0 to 2.8 Å.
[27] a) C. Tessier, F. D. Rochon, Inorg. Chim. Acta 1999, 295, 25–
38; b) E. Monti, M. Gariboldi, A. Maiocchi, E. Marengo, C.
Cassino, E. Gabano, D. Osella, J. Med. Chem. 2005, 48, 857–
866.
[17] D. Urankar, B. Pinter, A. Pevec, F. De Proft, I. Turel, J.
Kosˇmrlj, Inorg. Chem. 2010, 49, 4820–4829.
[18] K. J. Kilpin, J. D. Crowley, Polyhedron 2010, 29, 3111–3117.
[19] D. Urankar, J. Kosˇmrlj, Inorg. Chim. Acta 2010, 363, 3817–
3822.
[28] B. M. Still, P. G. A. Kumar, J. R. Aldrich-Wright, W. S. Price,
Chem. Soc. Rev. 2007, 36, 665–686.
[29] G. Annibale, M. Bonivento, L. Cattalini, M. L. Tobe, J. Chem.
Soc., Dalton Trans. 1992, 3433–3438.
ˇ
[20] S. Grabner, J. Kosˇmrlj, N. Bukovec, M. Cemazar, J. Inorg. Bio-
ˇ
chem. 2003, 95, 105–112.
[30] A. P. S. Fontes, A. Oskarsson, K. Lövqvist, N. Farrell, Inorg.
Chem. 2001, 40, 1745–1750.
[21] a) A. Maisonial, P. Serafin, M. Traïkia, E. Debiton, V. Théry,
D. J. Aitken, P. Lemoine, B. Viossat, A. Gautier, Eur. J. Inorg.
Chem. 2008, 298–305; b) A. Chevry, M.-L. Teyssot, A. Maison-
ial, P. Lemoine, B. Viossat, M. Traïkia, D. J. Aitken, G. Alves,
L. Morel, L. Nauton, A. Gautier, Eur. J. Inorg. Chem. 2010,
3513–3519.
[22] a) A. Canty, E. A. Stevens, Inorg. Chim. Acta 1981, 55, L57–
L59; b) N. Moeller, B. S. Kangarloo, I. Puscasu, C. Mock, B.
Krebs, J. E. A. Wolff, Anticancer Res. 2000, 20, 4435–4440.
[23] R. Romeo, L. M. Scolaro, Inorg. Synth. 1998, 32, 153–158.
[31] Y. Qu, S. G. de Almeida, N. Farrell, Inorg. Chim. Acta 1992,
201, 123–129.
[32] T. G. Appleton, F. B. Ross, Inorg. Chim. Acta 1996, 252, 79–
89.
[33] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, J.
Appl. Crystallogr. 1994, 27, 435–435.
[34] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
Received: October 2, 2010
Published Online: March 4, 2011
Eur. J. Inorg. Chem. 2011, 1921–1929
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1929