Amidoximes provide facile platinum(II)-mediated oxime-nitrile coupling

Article abstract of DOI:10.1021/ic3006019

The nucleophilic addition of amidoximes R′C(NH₂)=NOH [R′ = Me (2.Me), Ph (2.Ph)] to coordinated nitriles in the platinum(II) complexes trans-[PtCl₂(RCN)₂] [R = Et (1t.Et), Ph (1t.Ph), NMe₂ (1t.NMe₂)] and cis-[PtCl₂(RCN) ₂] [R = Et (1c.Et), Ph (1c.Ph), NMe₂ (1c.NMe₂)] proceeds in a 1:1 molar ratio and leads to the monoaddition products trans-[PtCl(RCN){HN=C(R)ONC(R′)NH₂}]Cl [R = NMe₂; R′ = Me ([3a]Cl), Ph ([3b]Cl)], cis-[PtCl₂{HN=C(R)ONC(R′) NH₂}] [R = NMe₂; R′ = Me (4a), Ph (4b)], and trans/cis-[PtCl₂(RCN){HN=C(R)ONC(R′)NH₂}] [R = Et; R′ = Me (5a, 6a), Ph (5b, 6b); R = Ph; R′ = Me (5c, 6c), Ph (5d, 6d), correspondingly]. If the nucleophilic addition proceeds in a 2:1 molar ratio, the reaction gives the bisaddition species trans/cis-[Pt{HN=C(R) ONC(R′)NH₂}₂]Cl₂ [R = NMe₂; R′ = Me ([7a]Cl₂, [8a]Cl₂), Ph ([7b]Cl₂, [8b]Cl₂)] and trans/cis-[PtCl₂{HN=C(R)ONC(R′)NH ₂}₂] [R = Et; R′ = Me (10a), Ph (9b, 10b); R = Ph; R′ = Me (9c, 10c), Ph (9d, 10d), respectively]. The reaction of 1 equiv of the corresponding amidoxime and each of [3a]Cl, [3b]Cl, 5b-5d, and 6a-6d leads to [7a]Cl₂, [7b]Cl₂, 9b-9d, and 10a-10d. Open-chain bisaddition species 9b-9d and 10a-10d were transformed to corresponding chelated bisaddition complexes [7d]²⁺-[7f]²⁺ and [8c] ²⁺-[8f]²⁺ by the addition of 2 equiv AgNO₃. All of the complexes synthesized bear nitrogen-bound O-iminoacylated amidoxime groups. The obtained complexes were characterized by elemental analyses, high-resolution ESI-MS, IR, and ¹H NMR techniques, while 4a, 4b, 5b, 6d, [7b](Cl)₂, [7d](SO₃CF₃)₂, [8b](Cl)₂, [8f](NO₃)₂, 9b, and 10b were also characterized by single-crystal X-ray diffraction.

Full text of DOI:10.1021/ic3006019

Article
pubs.acs.org/IC
Amidoximes Provide Facile Platinum(II)-Mediated Oxime−Nitrile
Coupling
Dmitrii S. Bolotin,† Nadezhda A. Bokach,*,† Matti Haukka,‡ and Vadim Yu. Kukushkin*,†,§
†Department of Chemistry, St. Petersburg State University, Universitetsky Pr. 26, 198504 Stary Petergof, Russian Federation
‡Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
§Institute of Macromolecular Compounds of Russian Academy of Sciences, V.O. Bolshoii Pr. 31, 199004 St. Petersburg, Russian
Federation
S
* Supporting Information
ABSTRACT: The nucleophilic addition of amidoximes R′C(NH2)NOH
[R′ = Me (2.Me), Ph (2.Ph)] to coordinated nitriles in the platinum(II) com-
plexes trans-[PtCl2(RCN)2] [R = Et (1t.Et), Ph (1t.Ph), NMe2 (1t.NMe2)] and
cis-[PtCl2(RCN)2] [R = Et (1c.Et), Ph (1c.Ph), NMe2 (1c.NMe2)] proceeds in
a 1:1 molar ratio and leads to the monoaddition products trans-[PtCl(RCN)-
{HNC(R)ONC(R′)NH2}]Cl [R = NMe2; R′ = Me ([3a]Cl), Ph ([3b]Cl)],
cis-[PtCl2{HNC(R)ONC(R′)NH2}] [R = NMe2; R′ = Me (4a), Ph (4b)],
and trans/cis-[PtCl2(RCN){HNC(R)ONC(R′)NH2}] [R = Et; R′ = Me (5a,
6a), Ph (5b, 6b); R = Ph; R′ = Me (5c, 6c), Ph (5d, 6d), correspondingly]. If the
nucleophilic addition proceeds in a 2:1 molar ratio, the reaction gives the
bisaddition species trans/cis-[Pt{HNC(R)ONC(R′)NH2}2]Cl2 [R = NMe2;
R′ = Me ([7a]Cl2, [8a]Cl2), Ph ([7b]Cl2, [8b]Cl2)] and trans/cis-[PtCl2{HN
C(R)ONC(R′)NH2}2] [R = Et; R′ = Me (10a), Ph (9b, 10b); R = Ph; R′ = Me
(9c, 10c), Ph (9d, 10d), respectively]. The reaction of 1 equiv of the corresponding amidoxime and each of [3a]Cl, [3b]Cl, 5b−
5d, and 6a−6d leads to [7a]Cl2, [7b]Cl2, 9b−9d, and 10a−10d. Open-chain bisaddition species 9b−9d and 10a−10d were
transformed to corresponding chelated bisaddition complexes [7d]2+−[7f]2+ and [8c]2+−[8f]2+ by the addition of 2 equiv
AgNO3. All of the complexes synthesized bear nitrogen-bound O-iminoacylated amidoxime groups. The obtained complexes
were characterized by elemental analyses, high-resolution ESI-MS, IR, and 1H NMR techniques, while 4a, 4b, 5b, 6d, [7b](Cl)2,
[7d](SO3CF3)2, [8b](Cl)2, [8f](NO3)2, 9b, and 10b were also characterized by single-crystal X-ray diffraction.
1,3,5-triazapentadienes,32−36,38,39 carboxamides37,40−44 and re-
INTRODUCTION
Nucleophilic addition to nitriles, RCN, represents an attrac-
■
lated species,45,46 and phthalocyanines.21,47 The latter findings
made a strong impact on the further exploration of the nitrile
tive route to new organic and coordination compounds with a
reactions with HON-type nucleophiles.
variety of laboratory and industrial applications. The reactivity
The results of the synthetic studies (see above) and also the
of nitriles has already been summarized in some comprehensive
performed theoretical considerations22,48,49 on the addition of
HON nucleophiles to ligated nitriles allowed verification of the
major driving forces of the reaction (Scheme 1). Thus, this
transformation could be enhanced by affecting the nitrile from
its different sides, viz., the C and/or N atoms. This group of
methods includes the application of high oxidation metal
centers (e.g., PtIV,11,12,24,28 ReIV,50 and RhIII16,17) and/or the
involvement of electron-deficient RCN (e.g., R = CO2Et,
CH2Cl) ligands.13,14
reviews,1−10 giving an idea that these compounds, in particular
unreactive RCN species bearing donor R groups, should be
subjected to additional electrophilic activation in order to
perform the nucleophilic addition. One of the most effective
routes to reach this activation is coordination to a metal center.
Although nucleophilic addition to metal-activated nitriles has
been studied for almost a century, only in the past decade were
these reactions extended to HON nucleophiles.9 In particular,
reactions between ligated nitriles at kinetically inert metal
centers (e.g., platinum11−15 or rhodium16,17) and HON species
such as “simple” oximes,13−22 vic-dioximes,23 and functionalized
oximes11,24−29 lead to the formation of the C−O{N} bond
upon addition of the OH group at the CN moiety.
Moreover, when these reactions were performed at kinetically
labile metal centers (e.g., CoII,30 NiII,20,21,31−36 and ZnII37), they
acquired an applied significance insofar as they opened some
efficient routes to syntheses of important classes of nitrile-
derived organic compounds such as amidines,30 acylamides,34
In principle, yet another route to promote the reaction is an
increase of the nucleophilicity of oxime species (Scheme 1).
However, conventional ketoximes and aldoximes usually
exhibit rather similar nucleophilic properties, displaying a
leveling effect in the addition. Thus, the latter approach for
the enhancementbased on the application of oximes of a
Received: March 22, 2012
Published: May 8, 2012
© 2012 American Chemical Society
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the differences in the reactivity of the nitrile complexes in
different cis/trans configurations.
Scheme 1. Enhancement of Nucleophilic Additions of
Oximes to Nitriles
RESULTS
■
As starting materials, we addressed, on the one hand, the nitrile
platinum(II) complexes trans-[PtCl2(RCN)2] [R = Et
(1t.Et),51 Ph (1t.Ph),52 NMe2 (1t.NMe2)53] and cis-
[PtCl2(RCN)2] [R = Et (1c.Et),51 Ph (1c.Ph),52 NMe2
(1c.NMe2)53] and, on the other hand, the amidoximes
R′C(NH2)NOH [R′ = Me (2.Me), Ph (2.Ph)54]. The
reaction of 1t.Et−1t.NMe2 and 1c.Et−1c.NMe2 with 2.Me or
2.Ph (in all possible combinations) proceeds at room
temperature (RT) at both 1:1 and 1:2 molar ratios of the
reactants (except 1t.Et, where the reaction stops after the addi-
tion of 1 equiv of amidoximes; see later) and affords complexes
bearing iminoacylated oxime species (Schemes 2 and 3 and
Table 1). Synthetic experiments are described in sections that
follow.
Reaction between the (Nitrile)platinum(II) Complexes
with 1 equiv of Amidoximes. The direction of the reaction
between platinum(II) nitrile complexes 1t and 1c and
amidoximes 2.Me or 2.Ph depends on the cis/trans con-
figuration of the starting metal complex and the nature of the
R group of the coordinated nitrile. Compounds 1t.Et, 1t.Ph,
1c.Et, and 1c.Ph, featuring coordinated alkyl- or arylcyanides,
react with 1 equiv of 2.Me or 2.Ph (in all possible
combinations) to form open-chain monoaddition species 5a−
5d (Scheme 2, b2) and 6a−6d (Scheme 3, b3), which were
isolated in 55−92% yield. In contrast to these alkyl- or
arylcyanide complexes, dimethylcyanamide-based compounds
1t.NMe2 and 1c.NMe2 react with 1 equiv of 2.Me or 2.Ph (in
all possible combinations) to form cationic [3a](Cl) and
[3b](Cl) (Scheme 2, a2) and neutral chelates 4a and 4b
(Scheme 3, a3).
higher nucleophilicitywas never synthetically explored in the
past.
Recently, we found that amidoximes are more reactive
nucleophiles than dialkylketoximes toward coupling with RCN
ligands at a PtIV center.11 Furthermore, our preliminary kinetic
data indicate that, in the addition to ligated nitriles, the
amidoxime Ph(NH2)CNOH is approximately an order of
magnitude stronger than Ph(Me)CNOH.50 In the current
work, we decided to amplify the reaction of amidoximes to
rather unreactive (RCN)PtII species, especially those where R is
a donor group. It is worth mentioning that previously only
three works dealt with the PtII-mediated nucleophilic addition
of oximes, and they all include the reaction with reactive nitriles
such as dialkylcyanamides or electron-deficient conventional
nitriles.13,14,18
Our particular interest in studying the addition of
amidoximes to nitrile ligands in platinum(II) complexes was
at least 4-fold. First, we expected to explore a novel approach
to the addition of oximes to metal-bound nitriles based on
the application of highly reactive oximes. Second, we were
interested in the extension of metal-mediated amidoxime−
nitrile coupling, previously reported for PtIV centers,11,12,23 to
PtII species. Third, we anticipated the study of the relative
reactivity of dialkylcyanamides and aryl- and alkylcyanides
bound to PtII centers. Fourth, it was planned to shed light on
Reaction of the (Nitrile)platinum(II) Complexes with 2
equiv of Amidoximes. Complexes [3a](Cl), [3b](Cl), 5c,
5d, and 6a−6d (see later for reactions of 5a and 5b), derived
from monoaddition, were converted to corresponding
bisaddition species [7a](Cl)2, [7b](Cl)2, 9c, and 9d (Scheme 2,
e2 and f 2) and 10a−10d (Scheme 3, e3) by the reaction with
1 equiv more of the corresponding amidoxime. Alternatively,
Scheme 2. Synthetic Transformations of 1t
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Scheme 3. Synthetic Transformations of 1c
Table 1. Compound Numbering and Preparative Yields of the Obtained Species
no.
R
R′
yield
no.
R
R′
yield
no.
R
R′
yield
[3a](Cl)
NMe2
NMe2
NMe2
NMe2
Et
Me
Ph
73
82
62
75
74
92
57
82
71
83
6c
Ph
Me
Ph
55
70
[8d](NO3)2
Et
Ph
Me
Ph
Ph
Me
Ph
Me
Ph
Me
Ph
∼100
∼100
∼100
33
[3b](Cl)
4a
6d
Ph
[8e](NO3)2
Ph
Ph
Et
Me
Ph
[7a](Cl)2
NMe2
NMe2
Et
Me
Ph
73
[8f](NO3)2
4b
[7b](Cl)2
82
9b
5a
Me
Ph
[7d](NO3)2
[7e](NO3)2
[7f](NO3)2
[8a](Cl)2
Ph
∼100
∼100
∼100
62
9c
Ph
Ph
Et
83
5b
Et
Ph
Me
Ph
9d
87
5c
Ph
Me
Ph
Ph
10a
10b
10c
10d
66
5d
Ph
NMe2
NMe2
Et
Me
Ph
Et
69
6a
Et
Me
Ph
[8b](Cl)2
75
Ph
Ph
81
6b
Et
[8c](NO3)2
Me
∼100
87
[7a](Cl)2, [7b](Cl)2, 9c, and 9d (Scheme 2, c2 and d2), and
[8a](Cl)2, [8b](Cl)2, and 10a−10d (Scheme 3, c3 and d3)
were obtained by the reaction of starting nitrile complexes
1.t and 1.c with 2 equiv of 2.Me or 2.Ph (in all possible
combinations) in a MeNO2 solution for 10−100 h at RT
(isolated yields 62−87%). Descriptions of these reactions are
given in the next two sections.
a. Reaction of [PtCl2(RCN)2] (R = Et, Ph) with 2 equiv of
Amidoximes. The direction of the reaction between the
platinum(II) propiononitrile complexes (1t.Et and 1c.Et) and
amidoxime 2.Me or 2.Ph depends on the cis/trans config-
uration of the starting metal species. The reaction of trans-
[PtCl2(EtCN)2] (1t.Et) with 2 equiv of 2.Me or 2.Ph in
nitromethane at RT completes after 2 days and brings about a
broad mixture of unidentified products. However, we were able
to synthesize the bisaddition product 9b via the reaction of
trans-[PtCl2(EtCN){HNC(Et)ONC(NH2)Ph}] (5b)
with 1 equiv of 2.Ph for 2 days in MeOH at RT, which leads
to precipitation of the crystalline trans-[PtCl2{HNC(Et)-
ONC(NH2)Ph}2]·2MeOH (9b) in 33% isolated yield along
with many unidentified products that remain in the solution.
An analogous reaction of 5a with 2.Me under the same reaction
conditions leads to a mixture of platinum-containing species in
solution, and no precipitate was formed.
Benzonitrile species 1t.Ph and 1c.Ph react with 2 equiv of 2.Me
or 2.Ph for 1 day in a nitromethane solution at RT to produce
the bisaddition products [PtCl2{HNC(Ph)ONC(NH2)-
R}2] (9c, 9d, 10c, and 10d).
b. Reaction of [PtCl2(NCNMe2)2] with 2 equiv of
Amidoximes. Compounds 1t.NMe2 and 1c.NMe2 react with
2 equiv of 2.Me or 2.Ph to furnish isomeric bischelates
[7a](Cl)2, [7b](Cl)2, [8a](Cl)2, and [8b](Cl)2 (Schemes 2
and 3), Complex 1t.NMe2 in the reaction forms bisaddition
chelates [7a](Cl)2 and [7b](Cl)2 for 10 h (vs 20 min for the
monoaddition products [3a](Cl) and [3b](Cl)) in nitromethane
at RT in 73% and 82% yields for R′ = Me and Ph, corre-
spondingly, while 1c.NMe2 in the reaction with 2 equiv 2.Me or
2.Ph (10 h, MeNO2, RT) gives a broad mixture of unidentified
species. Bischelates [8a](Cl)2 and [8b](Cl)2 were generated more
selectively and isolated in rather good yields (62% and 75% for
R′ = Me and Ph, respectively) only at −8 °C (100 h, MeNO2).
Chelation Promoted by Chloride Abstraction. We
found that bisaddition species derived from propiononitrile
(10a and 10b; Scheme 3) and benzonitrile complexes (9c and
9d in Scheme 2 and 10c and 10d in Scheme 3) do not convert
to corresponding chelated complexes [7e](Cl)2, [7f](Cl)2, and
[8c](Cl)2−[8f](Cl)2 in a MeNO2 solution at 100 °C or in
the solid phase at temperatures ca. 5 °C lower than the
corresponding decomposition temperatures for these com-
plexes. However, chelates [7e](NO3)2, [7f](NO3)2, and
[8c](NO3)2−[8f](NO3)2 were obtained from 9c and 9d
Complex cis-[PtCl2(EtCN)2] (1c.Et) reacts with 2 equiv of
2.Me or 2.Ph for 2 days in MeNO2 at RT to produce the
bisaddition products cis-[PtCl2{HNC(Et)ONC(NH2)R}2]
in good yields (66% for 10a and 69% for 10b; Scheme 3).
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Figure 1. Molecular structure of [7d](SO3CF3)2 with the atomic numbering scheme. Thermal ellipsoids are given at the 50% probability level.
Selected bond lengths (Å): N1−C1 1.2788(17); N2−C4 1.3132(16); N3−C4 1.3249(17).
(Scheme 2, g2) and 10a−10d (Scheme 3, f 3), respectively, by
abstraction of the chloride ligands with 2 equiv of AgNO3.
Thus, bischelate [7d](NO3)2 was generated by the reaction
of 9b with 2 equiv of AgNO3 for 30 min in MeOH at RT to
give [7d](NO3)2 in almost quantitative yield. The application
of AgSO3CF3 in this reaction could not be recommended as a
synthetic method insofar as all reaction products exhibit similar
solubilities and their separation is a rather difficult task. How-
ever, by conducting this experiment, we succeeded in isolating a
few crystals of [7d](SO3CF3)2 suitable for a single-crystal X-ray
diffraction study (see later), confirming the formulation of the
cation. The reaction of 1t.Et and 2.Me does not give the
corresponding bischelate when it was carried out in diverse
solvents (MeOH, EtOH, and MeNO2), employing different
silver salts (AgNO3 and AgSO3CF3), and at various temper-
atures ranging from −8 to +50 °C.
and/or ions [M + NH4]+, [M + Na]+, and [M + K]+ or frag-
mentation ions, i.e., [M − Cl]+ and [M − 2Cl − H]+; the latter
fragmentations are typical for platinum(II) chloride complexes.
The spectra of ionic species display peaks corresponding to the
cations [M − Cl]+ ([3a]+ and [3b]+), [M − 2Cl]2+ ([7a]2+,
[7b]2+, [8a]2+, and [8b]2+), and [M − 2NO3]2+ ([7d]2+−[7f]2+
and [8c]2+−[8f]2+) or fragmentation ions [M − H − 2Cl]+
([7a]2+, [7b]2+, [8a]2+, and [8b]2+) and [M − H − 2NO3]+
([7d]2+−[7f]2+, and [8c]2+−[8f]2+).
1
In the H NMR spectra of 4a, 4b, [7a](Cl)2, [7b](Cl)2,
[7d](NO3)2−[7f](NO3)2, [8a](Cl)2, [8b](Cl)2, and [8c]-
(NO3)2−[8f](NO3)2, one set of signals was observed, whereas
the spectra of [3a](Cl), [3b](Cl), 5a−5d, and 6a−6d exhibit
two sets of signals in a 1:1 ratio, viz., from the imine and the
1
nitrile. The characteristic feature of the H NMR spectra of
5a−5d, 6a−6d, 9b, 9d, 10b, and 10d is the presence of two
broad signals in a low-field region with an integral intensity 1:2
recognized as the NH and NH2 resonances, while the spectra of
9c, 10a, and 10c exhibit three broad signals in a 1:1:1 ratio with
Analytical and Spectroscopy Data. The complexes give
satisfactory C, H, and N elemental analyses for the proposed
formulas and were also characterized by high-resolution electro-
spray ionization mass spectrometry (ESI-MS), IR, and 1H
NMR spectroscopy. Cationic species [8c](NO3)2 and [8d]-
(NO3)2, as an exception, are not sufficiently stable, and they
start to decompose right after their formation. However, we
succeeded in providing their characterization by IR, high-
1
different chemical shifts of the amide group protons. The H
NMR spectra of chelates [3a](Cl), [3b](Cl), 4a, 4b, [7a](Cl)2,
[7b](Cl)2, [7d](NO3)2−[7f](NO3)2, [8a](Cl)2, [8b](Cl)2,
and [8c](NO3)2−[8f](NO3)2 display three signals of the NH
protons, which are situated in a lower field relative to the open-
chain species 5a−5d, 6a−6d, 9b−9d, and 10a−10d. In
[3b](Cl) and 4b, signals of the dimethylamino group are
shifted to a higher field relative to [3a](Cl) and 4a (ca. 0.3−0.4
ppm), and this effect may be caused by the shielding influence
of the phenyl group. The same influence of the aromatic ring
probably causes a high-field shift of one of the o- and m-H
signals in 6c and 6d relative to the corresponding geometrical
trans isomers 5c and 5d (ca. 0.4 ppm for ortho protons and ca.
0.2 ppm for meta protons).
X-ray Determinations. Molecular structures of 4a (Figure 2),
4b (Figure S1 in the Supporting Information), 5b (Figure 5),
6d (Figure 6), [7b](Cl)2 (Figure S2 in the Supporting
Information), [7d](SO3CF3)2 (Figure 1), [8b](Cl)2 (Figures 3
and 4), [8f](NO3)2 (Figure S3 in the Supporting Information),
9b (Figure 7), and 10b (Figure 8) indicate that all coordination
polyhedra exhibit typical square-planar geometry. All bond
1
resolution ESI-MS, and H NMR spectroscopy.
In the IR spectra of the obtained complexes, the PtII-bound
imines exhibit medium-to-strong bands at 3496−3058 cm−1,
which can be attributed to the N−H stretches. The spectra also
display one or two CN absorption bands in the range of
1674−1588 cm−1 specific for the iminoacylated oximes.55 No
bands assignable to CN stretches from the (nitrile)platinum-
(II) species were observed in the spectra of both mono- and
bisaddition species 4a, 4b, 5a−5d, 6a−6d, [7a](Cl)2, [7b]-
(Cl)2, [7d](NO3)2−[7f](NO3)2, [8a](Cl)2, [8b](Cl)2, [8c]-
(NO3)2−[8f](NO3)2, 9b−9d, and 10a−10d, whereas each of
monoaddition complexes [3a](Cl) and [3b](Cl) exhibits
medium-to-strong intensity bands due to ν(CN) at 2312
and 2295 cm−1, respectively.
Positive-mode high-resolution ESI-MS spectra of nonionic
species display peaks corresponding to the quasi-ion [M + H]+
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Supporting Information, respectively), the C−Nimine bond
lengths are typical CN double bonds, ranging from
1.276(3) to 1.2788(17) Å, while in dimethylcyanamide
derivatives 4a, 4b, [7b](Cl)2, and [8b](Cl)2 (Figures 2, S1
and S2 in the Supporting Information, 3, and 4, correspond-
ingly), the (C−N)imine bond lengths [1.298(3)−1.316(10) Å]
and C−NMe2 distances [1.314(11)−1.339(10) Å] have
intermediate order because conjugation between them. Another
conjugation is observed between the C−Noxime and C−NH2
bonds [bond lengths equal to 1.3132(16)−1.330(3) and
1.314(3)−1.333(4) Å, respectively]. The C−O [1.3349(15)−
1.363(10) Å] and O−N [1.4446(14)−1.472(8) Å] bond
lengths are the normal single bonds.57
In [7b](Cl)2, [7d](SO3CF3)2, and [8b](Cl)2 (Figures S2 in
the Supporting Information, 1, 3, and 4, respectively), the
oxime CN bonds in both ligands exhibit the E configuration,
while in 4a and 4b (Figures 2 and S1 in the Supporting
Information), the CN bonds are in the Z form, and
[8f](NO3)2 (Figure S3 in the Supporting Information) features
two ligands in the different E/Z configurations. In the E-
configured ligands, the intramolecular hydrogen bonding is
formed between the NH2 group and the oxime O atom [N···O
2.463−2.583 Å; N−H···O 95.97−105.21°]. In 4a and 4b
(Figures 2 and S1 in the Supporting Information) bearing the
Z-iminoacylated ligands, the hydrogen bond is formed between
the NH2 center and the Cl atom [N···Cl 3.099(4) and 3.092(3) Å;
N−H···Cl 156.8° and 163.1°, respectively]. No intramolecular
hydrogen bond was detected in the Z-configured ligand of
[8f](NO3)2 (Figure S3 in the Supporting Information).
cis-Bischelates [8a](Cl)2, [8b](Cl)2, and [8c](NO3)2−[8f]-
(NO3)2 exhibit a nonplanar arrangement. The twisted structure
provides the existence of the molecules in the isomeric P and M
forms (Figure 4). Two forms for [8a](Cl)2, [8b](Cl)2, and
[8c](NO3)2−[8f](NO3)2 were observed by single-crystal X-ray
diffraction, which was applied to racemic crystals obtained for
[8b](Cl)2 (Figures 3 and 4) and [8f](NO3)2 (Figure S3 in the
Supporting Information); both P and M isomers were observed
in the crystal lattices.
Figure 2. Molecular structure of 4a with the atomic numbering
scheme. Thermal ellipsoids are given at the 50% probability level.
Selected bond lengths (Å): N1−C1 1.314(6); N4−C1 1.331(5); N2−
C4 1.318(5); N3−C4 1.332(5).
Molecular Structures of Open-Chain Species 5b, 6d, 9b,
and 10b (Figures 5−8). All of the C−Nimine and C−Noxime
bond lengths are typical CN double bonds,12,57−59 ranging
from 1.251(3) to 1.289(6) Å and from 1.280(6) to 1.305(3) Å,
respectively, while the values of the C−NH2 [1.330(7)−
1.345(7) Å], C−O [1.342(3)−1.353(6) Å], and O−N
[1.450(2)−1.477(5) Å] bond lengths indicate their single-
bond characters.57 In 5b and 6d (Figures 5 and 6,
correspondingly), the C−Nnitrile bond lengths are typical C
N triple bonds, ranging from 1.135(6) to 1.147(6) Å.52,60
The iminoacylated oxime ligands are in the E form, which is
stabilized via the intramolecular hydrogen bonding between the
imino H atom and the uncomplexed oxime N atom [N···N
2.578(6)−2.623(6) Å; N−H···N 112.56−122.0°]; the same
type of hydrogen bonding was previously observed for other
open-chain N-bound iminoacylated oximes.12,23,28,58,59 Another
intramolecular hydrogen bridge is formed between NH2 and
the oxime O atom [N···O 2.506−2.561 Å; N−H···O 94.07−
104.93°].
Figure 3. Molecular structure of P-[8b](Cl)2 with the atomic
numbering scheme. Cl anions are omitted for clarity. Thermal
ellipsoids are given at the 50% probability level. Selected bond lengths
(Å): N1−C1 1.316(10); N5−C11 1.299(10); N2−C1 1.314(11);
N6−C11 1.339(10); N3−C4 1.320(10); N7−C14 1.316(11); N4−C4
1.321(11); N8−C14 1.308(11).
angles around the PtII centers are close to 90°, except the N−
Pt−N angles in the chelates (see below). The Pt−Cl distances
[2.2862(12)−2.3193(7) Å] are specific for the PtII−Cl bonds,56
the Pt−Nimine bond lengths [1.972(2)−2.033(3) Å] exhibit
values characteristic for (imine)platinum(II) species,57 and the
Pt−Noxime bond lengths [1.9895(18)−2.020(7) Å] have values
characteristic for (oxime)platinum(II) species.18 Bond lengths
and angles of the iminoacylated oxime ligands agree well
with those found for other similar (imine)platinum(II)
complexes.13,14,18
Molecular Structures of Chelates 4a, 4b, [7b](Cl)2,
[7d](SO3CF3)2, [8b](Cl)2, and [8f](NO3)2 (Figures 1−4 and
S1−S3 in the Supporting Information). The N−Pt−N angles
in the compounds range from 77.07(7) to 79.63(9)°. In
[7d](SO3CF3)2 and [8f](NO3)2 (Figures 1 and S3 in the
DISCUSSION
■
a. Differences in the Reactivity between Amidoximes
and Ketoximes. Earlier work18 explicitly shows that the
activation of aryl- and alkylcyanides by platinum(II) is insuffi-
cient for the nucleophilic addition of the ketoximes R′2CNOH
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Figure 4. Isomerism for [8b](Cl)2.
with R = Ph, CH2Cl, and CH2CO2Me. The reaction proceeds
at 40−50 °C and/or under microwave treatment to produce
monodentately coordinated O-imidoyloximes in moderate
yields (Scheme 5).13,14
Herein we demonstrated that the nucleophilic addition of
amidoxime 2.Me or 2.Ph to (RCN)2PtII species 1t and 1c
proceeds at RT and even at −8 °C [for [8a](Cl)2 and
[8b](Cl)2] to accomplish the iminoacylated species in good
yields. These observations supported our experimental
observations11 (see the Introduction section) that amidoximes
are much more reactive nucleophiles than dialkylketoximes
because of the +M effect of the NH2 group.
b. Differences in the Reactivity between Coordinated
Dialkylcyanamide and Aryl- and Alkylcyanides. Dime-
thylcyanamide complexes 1t.NMe2 and 1c.NMe2 react with
amidoximes to produce chelates [3a](Cl), [3b](Cl), 4a, 4b,
[7a](Cl)2, [7b](Cl)2, [8a](Cl)2, and [8b](Cl)2, while alkyl-
and arylcyanide complexes 1t.Et, 1t.Ph, 1c.Et, and 1c.Ph react
with 2.Me and 2.Ph to form open-chain species 5a−5d, 6a−6d,
9b−9d, and 10a−10d. This observation could be accounted for
by the reduced energy barrier of the imine CN bond
isomerization because of conjugation with the NMe2 group. In
our previous work,11 a similar Z configuration was observed for
relevant platinum(IV) complexes despite the open-chain nature
of the coordinated imines.
Figure 5. Molecular structure of 5b with the atomic numbering
scheme. Thermal ellipsoids are given at the 50% probability level.
Selected bond lengths (Å): N1−C1 1.289(6); N2−C11 1.147(6);
N3−C4 1.280(6); N4−C4 1.345(7).
Although the reactions of 1t and 1c with 1 and 2 equiv of
2.Me or 2.Ph proceed at substantially different times (20 min
to 48 h), they give structurally similar products. We observed
that 1t.NMe2 and 1c.NMe2 react with 2.Me or 2.Ph faster than
1t.Ph and 1c.Ph, which, in turn, under similar reaction con-
ditions react faster than 1t.Et and 1c.Et. The obtained data
indicate that the reactivity of platinum(II)-bound nitriles
toward the nucleophilic addition of amidoximes 2.Me and
2.Ph decreases in the following order, viz., dimethylcyanamide >
benzonitrile > propiononitrile ligands. The same reactivity trend
was previously observed by our group, and this phenomenon can
be explained by the crossover in frontier molecular orbitals control
of the nucleophilic addition, specific for dialkylcyanamides.61
c. Differences in the Reactivity between the cis- and
trans-(Nitrile)2platinum(II) Complexes. Most reactive di-
methylcyanamide complexes 1t.NMe2 and 1c.NMe2 react with
1 equiv of 2.Me or 2.Ph, and the reaction proceeds in different
directions. In the case of 1t.NMe2, the reaction occurs as a
nucleophilic addition of amidoxime (2.Me or 2.Ph), followed
Figure 6. Molecular structure of 6d with the atomic numbering
scheme. Thermal ellipsoids are given at the 50% probability level.
Selected bond lengths (Å): N2−C8 1.277(6); N1−C1 1.136(6); N3−
C15 1.291(6); N4−C15 1.330(7).
(R′2 = Me2; C4H8) to RCN ligands. Only in the case of cis-
[Pt(NCNR2)2(PPh3)2]2+ (R = Me, Et) were the chelated
monoaddition products obtained when Ag+ or Cu2+ was used
as an additional activator, which, as believed, metalates the
NR2 group (Scheme 4).18
Later, the platinum(II)-mediated reaction of oximes with
RCN ligands was extended to electron-deficient nitriles, i.e.,
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Figure 7. Molecular structure of 9b with the atomic numbering scheme. Thermal ellipsoids are given at the 50% probability level. Selected bond
lengths (Å): N1−C1 1.251(3); N2−C4 1.305(3); N3−C4 1.334(3).
Scheme 5. Microwave-Irradiation-Induced Ketoxime−
(Nitrile)platinum(II) Coupling
elimination of neutral dimethylcyanamide from the neutral
complex is more feasible than the elimination of chloride from
the positively charged complex. Compound 1t.NMe2 reacts with
2 equiv of 2.Me or 2.Ph at RT in good yields, while the reaction
of 1c.NMe2 under the same conditions leads to a broad
spectrum of unidentified products.
In summary, the results from this work could be considered
from at least three perspectives. First, we observed that ami-
Figure 8. Molecular structure of 10b with the atomic numbering
scheme. Thermal ellipsoids are given at the 50% probability level.
Selected bond lengths (Å): N1−C1 1.254(5); N4−C11 1.263(4);
N2−C4 1.301(4); N3−C4 1.334(4); N5−C14 1.299(5); N6−C14
1.339(5).
doximes are more reactive than ketoximes and aldoximes, and
this observation is coherent with the general idea that the NH2
moiety increases the nucleophilicity of the oxime group because
of the +M effect. Hence, the amidoxime species could serve as
candidates for the metal-mediated oxime−nitrile coupling when
a metal center does not provide sufficient activation for the
performance of this reaction. Furthermore, other types of func-
tionalized oximes, e.g., alkylhydroximic acids and their thio
analogues and also hydroxyguanidines, should also have an
enhanced nucleophilicity. The coupling of these species with
nitrile ligands is currently under investigation in our group.
Second, the reactivity of platinum(II)-bound RCN species
decreases in the order dimethylcyanamide > benzonitrile >
propiononitrile. Third, the reactivity of cis-(nitrile)2platinum(II)
complexes toward the addition of amidoximes is higher than that
of trans complexes; these trends point out to the more reactive
substrates for the coupling.
Scheme 4. Lewis Acid Catalyzed Ketoxime−
(Nitrile)platinum(II) Coupling
by intramolecular substitution of a chloride ligand, while
1c.NMe2 reacts with 1 equiv of 2.Me and 2.Ph to produce 4a
and 4b derived from the nucleophilic addition, followed by
the substitution of dimethylcyanamide. Apparently, the
EXPERIMENTAL SECTION
Materials and Instrumentation. Solvents were obtained from
commercial sources and used as received. The amidoximes
were synthesized by literature methods.54 Complexes [PtCl2(RCN)2]
■
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(R = Et,52 Ph,51 NMe253) were synthesized in accordance with the
published procedures; the cis and trans isomers were separated by
column chromatography on SiO2 (Silicagel 60 F254, 0.063−0.200 mm,
Merck). C, H, and N elemental analyses were carried out by the
Department of Organic Chemistry of St. Petersburg State University
on a Hewlett-Packard 185B carbon−hydrogen−nitrogen analyzer. ESI-
MS spectra were obtained on a Bruker micrOTOF spectrometer
equipped with an ESI source. The instrument was operated in both
positive- and negative-ion mode using a range of m/z 50−3000. The
capillary voltage of the ion source was set at −4500 V (ESI+-MS) and
the capillary exit at (70−150) V. The nebulizer gas flow was 0.4 bar
and the drying gas flow 4.0 L/min. For ESI, species were dissolved in
MeOH or MeCN. In the isotopic pattern, the most intensive peak is
reported. Thin-layer chromatography (TLC) was performed on Silufol
UV254 SiO2 plates. IR spectra (4000−400 cm−1) were recorded on a
Synthetic Work. Nucleophilic Addition of the Amidoximes to
the (Nitrile)platinum(II) Complexes. i. Nucleophilic Addition of 1
equiv of R′C(NH2)NOH (R′ = Me, Ph) to trans-[PtCl2(NCNMe2)2]. A
solution of the amidoxime R′C(NH2)NOH (R′ = Me, Ph) (0.10 mmol)
in nitromethane (3 mL; R′ = Me) or in chloroform (1 mL; R′ = Ph) was
added dropwise for 5 min to a stirred solution of trans-[PtCl2(NCNMe2)2]
(0.10 mmol) in nitromethane (1 mL; R′ = Me) or in chloroform (1.5 mL;
R′ = Ph). After 20 min, the volume was reduced in vacuo to 0.5 mL, and
the oily precipitate that formed (R′ = Ph) crystallized under ultrasound
treatment. The crystalline precipitates were separated by filtration, washed
by two 1-mL portions of diethyl ether, and dried at RT in air.
1
Shimadzu FTIR-8400S instrument in KBr pellets. H NMR spectra
were measured on a Bruker DPX 300 spectrometer at ambient
temperature in Me2SO-d6 and CDCl3; residual solvent signals were
used as internal standards.
X-ray Structure Determinations. The crystals of all complexes
were immersed in cryo-oil, mounted in a Nylon loop, and measured at
a temperature of 100 K. The X-ray diffraction data were collected on a
Bruker Kappa Apex II, a Bruker Smart Apex II, or a Bruker Kappa
Apex II diffractometer using Mo Kα radiation (λ = 0.71073 Å). The
APEX262 software packages were used for cell refinement and data
reduction. A semiempirical absorption correction based on equivalent
reflections of a numerical absorption correction (SADABS63) was
applied to all data. The structures were solved by direct methods using
the SHELXS-97,64 SIR97,65 or SIR200866 programs with the WinGX67
graphical user interface. Structural refinements were carried out using
SHELXL-97.64 The NH H atoms were either located from the
difference Fourier map and constrained to ride on their parent atom
with Uiso = 1.5Ueq (parent atom) or positioned geometrically with N−
H = 0.88 and Uiso = 1.2Ueq (parent atom). In all structures, the NH2
and OH H atoms were located from the difference Fourier map and
constrained to ride on their parent atom with Uiso = 1.5Ueq (parent
atom). In structure 7b, the H2O H atoms were located from the
difference Fourier map, and in 8b, they were located by using
Nardelli’s HYDROGEN program.68 In both cases, the H atoms were
constrained to ride on their parent atom with Uiso = 1.5Ueq (parent
atom). All other H atoms were positioned geometrically and
constrained to ride on their parent atom with C−H = 0.95−0.99 Å
and Uiso = 1.2 − 1.5Ueq (parent atom).
In 4a, the CH3NO2 solvent molecule was disordered over two sites
with equal occupancies. The N1S−C1S bond was constrained to the
observed value, and all heavy atoms in CH3NO2 were restrained so
that their Uij components approximate to isotropic behavior. In 6d,
one of the phenyl rings (C16B−C21B) was disordered over two sites
with an occupancy ratio of 0.53/0.47. These rings were constrained to
fit in a regular hexagon with C−C = 1.39 Å. Furthermore, the C atoms
were constrained to have similar displacement parameters. Another
phenyl ring (C16−C21) was also slightly disordered, and therefore the
C atoms were restrained so that their Uij components approximate to
isotropic behavior. In 8b, the asymmetric unit contains two platinum
complexes, four Cl− anions, one H2O solvent molecule, and seven
CH3NO2 solvent molecules. Five of the CH3NO2 molecules were
included in the final structure model. A series of geometric and
displacement restraints were applied to these solvent molecules. The
other two CH3NO2 molecules were heavily disordered, and a
satisfactory disorder model was found for them. Their contribution
to the calculated structure factors was taken into account by using the
SQUEEZE routine of PLATON.69 However, the missing CH3NO2
molecules were taken into account in the unit cell content. The crystal
of 9d was diffracting only weakly. Therefore, satisfactory data
completeness could not been obtained. This structure is included
only as Supporting Information. In 9b, the ethyl group (C1−C2) was
disordered over two sites with occupancies of 0.55 and 0.45. The
crystallographic details of all structures except 9d are summarized in
Tables S1 and S2 in the Supporting Information. The crystallographic
parameters of 9d are given in Table S3 in the Supporting Information.
[3a](Cl). Yield: 93%. Mp: 152 °C (dec). Anal. Calcd for
C8H18N6Cl2OPt·H2O: C, 19.28; H, 4.05; N, 16.87. Found: C, 19.39;
H, 4.10; N, 16.73. High-resolution ESI+-MS (MeOH, m/z): 445.095
([M − Cl]+, calcd 445.082). IR (KBr, selected bonds, cm−1): 3339(m-
s), 3204(m), 3159(m-s) [ν(N−H)]; 2312(s) [ν(CN)]; 1674(vs),
1655(s) [ν(CN)]; 1609(m) [δ(N−H) and/or ν(CN)]; 658(w-
1
m) [δ(C−H)]. H NMR (DMSO-d6, δ): 8.64 (s, br, 1H, NH), 7.86
(s, br, 1H, NH2), 7.57 (s, br, 1H, NH2), 3.07 (s, 6H, NMe2), 2.97 (s,
6H, NMe2), 2.12 (s, 3H, CH3).
[3b](Cl). Yield: 67%. Mp: 104 °C (dec). Anal. Calcd for
C13H20N6Cl2OPt·2H2O: C, 27.00; H, 4.18; N, 14.53. Found: C,
26.85; H, 4.21; N, 14.34. High-resolution ESI+-MS (MeOH, m/z):
436.052 ([M − Cl − NCNMe2]+, calcd 436.045), 507.107 ([M −
Cl]+, calcd 507.098), 1012.203 ([2M − H − 2Cl]+, calcd 1012.189).
IR (KBr, selected bonds, cm−1): 3416(s), 3358(s), 3290(m) [ν(N−H)];
3045(vw), 2995(vw), 2932(w) [ν(C−H)]; 2295(m-s) [ν(CN)];
1666(s), 1626(vs) [ν(CN)]; 1603(m), 1576(m) [δ(N−H) and/or
1
ν(CN)]; 781(m), 706(m) [δ(C−H)]. H NMR (DMSO-d6, δ): 8.88
(s, br, 1H, NH2), 8.56 (s, br, 1H, NH2), 7.75−7.70 (m, 4H, NH + o- and
p-CH), 7.61 (t, 2H, m-CH), 3.13 (s, 6H, NMe2), 2.58 (s, 6H, NMe2).
ii. Nucleophilic Addition of 1 equiv of R′C(NH2)NOH (R′ = Me,
Ph) to cis-[PtCl2(NCNMe2)2]. A solution of cis-[PtCl2(NCNMe2)2]
(0.10 mmol) in nitromethane (1 mL) was added to a solution of the
amidoxime R′C(NH2)NOH (0.15 mmol; R′ = Me, Ph) in
nitromethane (10 mL at 60 °C for R′ = Me; 2 mL at RT for R′ =
Ph). The solution was kept for 6 h (R′ = Me) or for 18 h (R′ = Ph) at
the corresponding temperature, whereupon the solvent was evapo-
rated in vacuo at RT. The residue formed was washed with one 1-mL
portion of cold (−5 °C) chloroform and two 1-mL portions of
MeOH:Et2O (50:50, v/v) and dried at RT in air.
4a. Yield: 63%. Mp: 162 °C (dec). Anal. Calcd for C5H12N4Cl2OPt:
C, 14.64; H, 2.95; N, 13.66. Found: C, 14.88; H, 3.17; N, 13.48.
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High-resolution ESI+-MS (MeOH:Me2SO = 10:1, m/z): 432.988
([M + Na]+, calcd 432.988), 453.046 ([M − Cl + Me2SO]+, calcd
453.043), 842.989 ([2M + Na]+, calcd 842.987). IR (KBr, selected
bonds, cm−1): 3373(vs), 3281(m), 3227(m), 3182(m) [ν(N−H)];
2966(w), 2935(w), 2887(vw), 2818(vw) [ν(C−H)]; 1661(vs),
1636(s) [ν(CN)]; 1589(w) [δ(N−H), ν(CN), and/or ν(C
C)]; 571(m), 530(m) [δ(C−H)]. TLC (eluent is chloroform:acetone
= 2:1, v/v): Rf = 0.32. 1H NMR (DMSO-d6, δ): 7.95 (s, br, 1H, NH2),
7.89 (s, br, 1H, NH2), 7.42 (s, br, 1H, NH), 3.00 (s, 6H, NMe2), 2.16
(s, 3H, CH3). Crystals suitable for X-ray study were obtained by the
slow evaporation of a nitromethane solution at RT in air.
5b. Yield: 92%. Mp: 122 °C (dec). Anal. Calcd for
C13H18N4Cl2OPt·H2O: C, 29.44; H, 3.80; N, 10.56. Found: C,
29.58; H, 3.51; N, 10.37. High-resolution ESI+-MS (MeOH, m/z):
477.081 ([M − Cl]+, calcd 477.076), 535.039 ([M + Na]+, calcd
535.035), 551.012 ([M + K]+, calcd 551.009), 989.129 ([2M − Cl]+,
calcd 989.122), 1047.092 ([2M + Na]+, calcd 1047.081), 1063.062
([2M + K], calcd 1063.055). IR (KBr, selected bonds, cm−1):
3427(m), 3321(m), 3246(w), 3212(w) [ν(N−H)]; 2986(w),
2944(w), 2917(w), 2881(w) [ν(C−H)]; 1666(w), 1626(s) [ν(C
N) and/or ν(CCAr)]; 1566(w) ]δ(N−H), ν(CN), and/or ν(C
CAr)]; 780(w), 696(w) [δ(C−H)]. TLC (eluent is chloroform:ace-
1
tone = 10:1, v/v): Rf = 0.55. H NMR (CDCl3, δ): 7.98 (s, br, 1H,
NH), 7.64 (d, 2H, o-CH), 7.55 (t, 1H, p-CH), 7.47 (t, 2H, m-CH, Ph),
5.21 (s, br, 2H, NH2), 3.15 (q, 2H, CH2), 2.80 (q, 2H, CH2),
1.47 (t, 3H, CH3), 1.38 (t, 3H, CH3). Crystals suitable for X-ray study
were obtained by the slow evaporation of an ethanol solution at RT
in air.
4b. Yield: 94%. Mp: 158 °C (dec). Anal. Calcd for
C10H14N4Cl2OPt: C, 25.43; H, 2.99; N, 11.86. Found: C, 25.17; H,
2.82; N, 11.74. High-resolution ESI+-MS (MeOH, m/z): 490.035
([M + NH4]+, calcd 490.048), 494.992 ([M + Na]+, calcd 495.004),
510.963 ([M + K]+, calcd 510.978), 962.030 ([2M + NH4]+, calcd
962.063), 967.026 ([2M + Na]+, calcd 967.018), 982.996 ([2M + K]+,
calcd 982.992), 1439.048 ([3M + Na]+, calcd 1439.032), 1455.011
([3M + K]+, calcd 1455.006), 1911.069 ([4M + Na]+, calcd
1911.047), 1927.036 ([4M + K]+, calcd 1927.021). IR (KBr, selected
bonds, cm−1): 3442(s), 3432(s) [ν(N−H)]; 2961(w), 2923(w),
2853(w) [ν(C−H)]; 1653(m), 1636(m) [ν(CN)]; 1559(w) [δ(N−
H). ν(CN), and/or ν(CC)]; 782(w), 705(w), 668(w) [δ(C−H)].
5c. Yield: 57%. Mp: 136 °C (dec). Anal. Calcd for
C16H16N4Cl2OPt·0.1CHCl3: C, 34.64; H, 2.91; N, 10.04. Found: C,
34.74; H, 2.87; N, 9.90. High-resolution ESI+-MS (MeOH, m/z):
474.092 ([M − 2Cl − H]+, calcd 474.084), 511.068 ([M − Cl]+, calcd
511.061). IR (KBr, selected bonds, cm−1): 3454(s), 3413(s), 3264(m)
[ν(N−H)]; 3072(w), 2926(m), 2851(w) [ν(C−H)]; 1619(s) [ν(C
N) and/or ν(CCAr)]; 1576(m) [δ(N−H), ν(CN), and/or
ν(CCAr)]; 781(w), 758(m), 684(w) [δ(C−H)]. TLC (eluent is
chloroform:acetone = 10:1, v/v): Rf = 0.41. 1H NMR (CDCl3, δ): 8.60
(d, 2H, Ph), 8.32 (s, br, 1H, NH), 7.83−7.50 (m, 8H, Ph), 4.98 (s, br,
2H, NH2), 2.03 (s, 3H, CH3).
1
TLC (eluent is chloroform:acetone = 5:1, v/v): Rf = 0.31. H NMR
(DMSO-d6, δ): 8.36 (s, br, 1H, NH2), 8.30 (s, br, 1H, NH2), 7.62−7.50
(m, 5H, Ph), 7.46 (s, br, 1H, NH), 2.71 (s, 6H, NMe2). Crystals suitable
for X-ray study were obtained from the reaction mixture at RT.
iii. Nucleophilic Addition of 1 equiv of R′C(NH2)NOH (R′ = Me,
Ph) to [PtCl2(RCN)2] (R = Et; Ph). A mixture of the amidoxime
R′C(NH2)NOH (0.1 mmol; R′ = Me, Ph) and cis- or trans-
[PtCl2(RCN)2] (0.1 mmol; R = Et; Ph) was dissolved in nitromethane
(3 mL). The solution was kept for 3 h at RT, whereupon the solvent
was evaporated in vacuo. The residue formed was washed with two
1-mL portions of cold (−5 °C) chloroform and dried at RT in air.
5d. Yield: 82%. Mp: 136 °C (dec). Anal. Calcd for
C21H18N4Cl2OPt·CHCl3: C, 36.31; H, 2.63; N, 7.70. Found: C,
36.25; H, 2.53; N, 7.71. High-resolution ESI+-MS (MeOH, m/z):
607.032 ([M − H]+, calcd 607.037), 1181.105 ([2M − Cl]+, calcd
1181.122), 1215.071 ([2M − H]+, calcd 1215.083), 1239.077 ([2M +
Na]+, calcd 1239.081). IR (KBr, selected bonds, cm−1): 3489(s),
3439(s), 3268(m) [ν(N−H)]; 3068(w), 2924(m), 2853(w) [ν(C−
H)]; 1654(s), 1624(s) [ν(CN) and/or ν(CCAr)]; 1567(m)
[δ(N−H), ν(CN), and/or ν(CCAr)]; 755(w), 696(w), 683(w)
[δ(C−H)]. TLC (eluent is chloroform:acetone = 10:1, v/v): Rf = 0.63.
1H NMR (CDCl3, δ): 8.65 (d, 2H, Ph), 8.45 (s, br, 1H, NH), 7.77−
7.48 (m, 13H, Ph), 5.29 (s, br, 2H, NH2).
5a. Yield: 74%. Mp: 114 °C (dec). Anal. Calcd for
C8H16N4Cl2OPt·1/4CHCl3: C, 20.64; H, 3.41; N, 11.67. Found: C,
20.81; H, 3.58; N, 11.50. High-resolution ESI+-MS (MeOH, m/z):
378.087 ([M − H − 2Cl]+, calcd 378.084), 415.068 ([M − Cl]+, calcd
415.061), 468.069 ([M + NH4]+, calcd 468.064), 865.082 ([2M −
Cl]+, calcd 865.091), 918.093 ([2M + NH4]+, calcd 918.094). IR (KBr,
selected bonds, cm−1): 3414(m), 3350(s), 3323(s), 3228(m),
3188(m) [ν(N−H)]; 2982(w-m), 2948(w-m), 2921(w), 2884(w)
[ν(C−H)]; 1670(m), 1637(vs) [ν(CN)]; 1607(s), 1569(w) [δ(N−
H) and/or ν(CN)]; 588(w), 536(w-m) [δ(C−H)]. TLC (eluent is
chloroform:acetone = 5:1, v/v): Rf = 0.49. 1H NMR (CDCl3, δ): 7.84
(s, br, 1H, NH), 4.86 (s, br, 2H, NH2), 3.07 (q, 2H, CH2), 2.80 (q,
2H, CH2), 1.95 (s, 3H, CH3), 1.40 (t, 3H, CH3), 1.38 (t, 3H, CH3).
6a. Yield: 71%. Mp: 97 °C (dec). Anal. Calcd for C8H16N4Cl2OPt:
C, 21.34; H, 3.58; N, 12.44. Found: C, 21.47; H, 3.52; N, 12.40. High-
resolution ESI+-MS (MeOH, m/z): 378.089 ([M − H − 2Cl]+, calcd
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378.084), 415.066 ([M − Cl]+, calcd 415.061), 451.043 ([M + H]+,
calcd 451.037), 468.071 ([M + NH4]+, calcd 468.064), 865.090
([2M − Cl]+, calcd 865.091), 918.089 ([2M + NH4]+, calcd 918.094),
939.019 ([2M + K]+, calcd 939.023), 1278.129 ([3M − H − 2Cl]+,
calcd 1278.144), 1351.093 ([3M + H]+, calcd 1351.097). IR (KBr,
selected bonds, cm−1): 3417(m), 3322(s), 3242(m) [ν(N−H)];
2988(w), 2948(w-m), 2921(w-m), 2886(w) [ν(C−H)]; 1672(m),
1631(vs) [ν(CN)]; 1608(s) [δ(N−H) and/or ν(CN)]; 608(w),
523(w) [δ(C−H)]. TLC (eluent is chloroform:acetone = 3:1, v/v):
Rf = 0.43. 1H NMR (CDCl3, δ): 7.74 (s, br, 1H, NH), 5.06 (s, br, 2H,
NH2), 3.07 (q, 2H, CH2), 2.80 (q, 2H, CH2), 2.01 (s, 3H, CH3), 1.43
(t, 3H, CH3), 1.38 (t, 3H, CH3).
6d. Yield: 70%. Mp: 128 °C (dec). Anal. Calcd for
C21H18N4Cl2OPt: C, 41.46; H, 2.98; N, 9.21. Found: C, 41.24; H,
2.92; N, 9.39. High-resolution ESI+-MS (MeOH, m/z): 609.108
([M + H]+, calcd 609.053), 626.136 ([M + NH4]+, calcd 626.080),
631.092 ([M + Na]+, calcd 631.035), 647.066 ([M + K]+, calcd
647.009), 1234.209 ([2M + NH4]+, calcd 1234.125), 1239.174 ([2M +
Na]+, calcd 1239.081), 1255.141 ([2M + K]+, calcd 1255.055). IR
(KBr, selected bonds, cm−1): 3417(s), 3326(m), 3206(m) [ν(N−H)];
3064(w), 2961(m), 2934(w) [ν(C−H)]; 1625(s), 1599(m) [ν(C
N) and/or ν(CCAr)]; 1565(m) [δ(N−H), ν(CN), and/or
ν(CCAr)]; 775(w), 750(w), 691(w) [δ(C−H)]. TLC (eluent is
chloroform:acetone = 10:1, v/v): Rf = 0.37. 1H NMR (CDCl3, δ): 8.70
(d, 2H, o-CH), 8.59 (s, br, 1H, NH), 7.72 (d, 2H, o-CH), 7.66−7.49
(m, 7H, Ph), 7.42 (t, 2H, m-CH), 7.24 (d, 2H, o-CH), 5.33 (s, br, 2H,
NH2). Crystals suitable for X-ray study were obtained by the slow
evaporation of a nitromethane solution at RT in air.
iv. Nucleophilic Addition of 2 equiv of R′C(NH2)NOH (R′ = Me,
Ph) to cis- and trans-[PtCl2(NCNMe2)2]. A solution of R′C(NOH)-
NH2 (0.2 mmol) in nitromethane (1 mL) (or methanol for R′ = Me)
was added to a solution of [PtCl2(NCNMe2)2] (0.1 mmol) in
nitromethane (2 mL). The homogeneous solution was kept for 10 h at
RT (for trans-[PtCl2(NCNMe2)2]) or 100 h at −8 °C (for cis-
[PtCl2(NCNMe2)2]). The precipitate formed was filtered off, washed
with two 2-mL portions of nitromethane, and dried at RT in air.
6b. Yield: 83%. Mp: 110 °C (dec). Anal. Calcd for
C13H18N4Cl2OPt·H2O: C, 29.44; H, 3.80; N, 10.56. Found: C,
29.37; H, 3.62; N, 10.66. High-resolution ESI+-MS (MeOH, m/z):
513.064 ([M + H]+, calcd 513.053), 530.091 ([M + NH4]+, calcd
530.080), 535.047 ([M + Na]+, calcd 535.035), 551.019 ([M + K]+,
calcd 551.009), 1042.133 ([2M + NH4]+, calcd 1042.125), 1047.098
([2M + Na]+, calcd 1047.081), 1063.063 ([2M + K]+, calcd
1063.055). IR (KBr, selected bonds, cm−1): 3424(s), 3332(m),
3241(m) [ν(N−H)]; 3064(w), 2992(w), 2942(w) [ν(C−H)];
1599(m) [ν(CN) and/or ν(CCAr)]; 1560(m) [δ(N−H),
ν(CN), and/or ν(CCAr)]; 776(w), 752(w), 697(w) [δ(C−H)].
1
TLC (eluent is chloroform:acetone = 2:1, v/v): Rf = 0.61. H NMR
(CDCl3, δ): 7.89 (s, br, 1H, NH), 7.68 (d, 2H, o-CH), 7.59 (t, 1H,
p-CH), 7.51 (t, 2H, m-CH, Ph), 5.25 (s, br, 2H, NH2), 3.15 (q, 2H,
CH2), 2.75 (q, 2H, CH2), 1.47 (t, 3H, CH3), 1.38 (t, 3H, CH3).
[7a](Cl)2. Yield: 73%. Mp: 225 °C (dec). Anal. Calcd for
C10H24N8Cl2O2Pt·1/2H2O: C, 21.32; H, 4.47; N, 19.89. Found: C,
21.46; H, 4.55; N, 19.75. High-resolution ESI+-MS (MeOH, m/z):
482.155 ([M − 2Cl − H]+, calcd 482.154). IR (KBr, selected bonds,
cm−1): 3432(m), 3425(m), 3290(m), 3181(m), 3058(m) [ν(N−H)];
2925(w), 2853(w), 2824(w) [ν(C−H)]; 1649(s), 1613(m) [ν(C
1
N)]; 767(w), 724(w), 687(w) [δ(C−H)]. H NMR (DMSO-d6, δ):
8.60 (s, 1H, NH2), 8.00 (s, 1H, NH2), 7.11 (s, br, 1H, NH), 3.09 (s, br,
6H, NMe2), 2.73 (s, 3H, CH3).
6c. Yield: 55%. Mp: 85 °C (dec). Anal. Calcd for C16H16N4Cl2OPt:
C, 35.18; H, 2.95; N, 10.26. Found: C, 35.24; H, 2.92; N, 10.13. High-
resolution ESI+-MS (MeOH, m/z): 546.049 ([M + H]+, calcd
546.043), 563.078 ([M + NH4]+, calcd 563.069). IR (KBr, selected
bonds, cm−1): 3447(s), 3351(s), 3276(m) [ν(N−H)]; 3193(m),
3064(w), 2963(w-m), 2924(w), 2866(w) [ν(C−H)]; 1648(m),
1623(vs) [ν(CN)]; 1599(m-s) [δ(N−H), ν(CN), and/or
ν(CCAr)]; 805(m), 757(m), 697(m), 684(m) [δ(C−H)]. TLC
(eluent is chloroform:acetone = 5:1, v/v): Rf = 0.39. 1H NMR
(CDCl3, δ): 8.63 (d, 2H, o-CH), 8.41 (s, br, 1H, NH), 7.64−7.49 (m,
4H, Ph), 7.42 (t, 2H, m-CH), 7.23 (d, 2H, o-CH), 5.10 (s, br, 2H,
NH2), 2.06 (s, 3H, CH3).
[7b](Cl)2. Yield: 82%. Mp: 168 °C (dec). Anal. Calcd for
C20H28N8Cl2O2Pt·1/2H2O: C, 34.94; H, 4.25; N, 16.30. Found: C,
35.08; H, 4.36; N, 16.26. High-resolution ESI+-MS (MeOH, m/z):
303.593 ([M − 2Cl]2+, calcd 303.596), 606.177 ([M − 2Cl − H]+,
calcd 606.185). IR (KBr, selected bonds, cm−1): 3448(m), 3414(s),
3401(s), 3151(m) [ν(N−H)]; 2990(m), 2959(m), 2926(m) [ν(C−
H)]; 1649(s) [ν(CN)]; 1592(m) [ν(CN) and/or ν(CCAr)];
1570(w) [δ(N−H), ν(CN), and/or ν(CCAr)]; 778(w), 694(w)
1
[δ(C−H)]. H NMR (DMSO-d6, δ): 9.10 (s, 1H, NH2), 8.84 (s, 1H,
NH2), 7.85−7.60 (m, 6H, NH + Ar), 2.73 (s, br, 6H, NMe2). Crystals
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suitable for X-ray study were obtained by the slow evaporation of an
ethanol solution of the complex at RT in air.
ν(CCAr)]; 1576(s) [δ(N−H), ν(CN), and/or ν(CCAr)]; 778(m),
702(w), 690(m) [δ(C−H)]. TLC (eluent is chloroform:acetone =
4:1, v/v): Rf = 0.35. H NMR (DMSO-d6, δ): 8.32 (d, 2H, o-CH),
1
8.18 (s, br, 1H, NH), 7.69 (t, 1H, p-CH), 7.57 (t, 2H, m-CH), 7.10
(s, br, 1H, NH), 6.84 (s, br, 1H, NH), 1.91 (s, 3H, CH3).
[8a](Cl)2. Yield: 62%. Mp: 156 °C (dec). Anal. Calcd for
C10H24N8Cl2O2Pt·2H2O: C, 20.34; H, 4.78; N, 18.98. Found: C,
20.46; H, 4.67; N, 18.87. High-resolution ESI+-MS (MeOH, m/z):
482.149 ([M − 2Cl − H]+, calcd 482.154). IR (KBr, selected bonds,
cm−1): 3406(s), 3246(m), 3150(m) [ν(N−H)]; 2935(w) ν(C−H);
9d. Yield: 87%. Mp: 143 °C (dec). Anal. Calcd for
C28H26N6Cl2O2Pt·H2O: C, 44.10; H, 3.70; N, 11.02. Found: C,
44.08; H, 3.52; N, 11.13. High-resolution ESI+-MS (MeOH:Me2SO =
10:1, m/z): 787.157 ([M − Cl + Me2SO]+, calcd 787.154). IR (KBr,
selected bonds, cm−1): 3491(m-s), 3340(m-s), 3283(m-s), 3258(sh)
[ν(N−H)]; 3173 (w), 3055(w) [ν(C−H)]; 1622(vs) [ν(CN)];
1560(m-s) [δ(N−H), ν(CN), and/or ν(CCAr)]; 777(m-s),
696(s) [δ(C−H)]. TLC (eluent is chloroform:acetone = 10:1, v/v):
1
1643(s) [ν(CN)]; 726(w), 682(w) [δ(C−H)]. H NMR (DMSO-
d6, δ): 8.70 (s, 1H, NH2), 8.55 (s, 1H, NH2), 8.01 (s, br, 1H, NH),
3.11 (s, br, 6H, NMe2), 2.17 (s, 3H, CH3).
1
Rf = 0.66. H NMR (DMSO-d6, δ): 8.90 (d, 2H, o-CH), 8.47 (s, br,
1H, NH), 7.85 (d, 2H, o-CH), 7.72 (t, 1H, p-CH), 7.63−7.50 (m, 5H,
m- and p-CH), 7.39 (s, br, 2H, NH2).
[8b](Cl)2. Yield: 75%. Mp: 142 °C (dec). Anal. Calcd for
C20H28N8Cl2O2Pt·2H2O: C, 33.62; H, 4.51; N, 15.68. Found: C,
33.43; H, 4.67; N, 15.68. High-resolution ESI+-MS (MeOH, m/z):
303.597 ([M − 2Cl]2+, calcd 303.596). IR (KBr, selected bonds,
cm−1): 3448(s) [ν(N−H)]; 2961(w), 2932(w), 2875(w) [ν(C−H)];
1636(s) [ν(CN) and/or ν(CCAr)]; 776(w), 690(w) [δ(C−H)].
1H NMR (DMSO-d6, δ): 8.87 (s, br, 1H, NH), 8.25 (s, br, 1H, NH2),
7.94 (s, br, 1H, NH2), 7.67−7.60 (m, 3H, o- and p-CH), 7.49 (t, 2H,
m-CH), 3.15 (s, 6H, NMe2). Crystals suitable for X-ray study were
obtained by the slow evaporation of a nitromethane solution of the
complex at RT in air.
v. Nucleophilic Addition of 2 equiv of R′C(NH2)NOH (R′ = Me,
Ph) to [PtCl2(RCN)2] (R = Et; Ph). A mixture of the amidoxime
R′C(NH2)NOH (R′ = Me, Ph) (0.22 mmol) and cis- or trans-
[PtCl2(RCN)2] (0.10 mmol; R = Et; Ph) was dissolved (9d and 10b)
or suspended (9c, 10a, 10c, and 10d) in nitromethane (3 mL). The
vigorously stirred suspension (or homogeneous solution without
stirring for 9d and 10b) was kept for 24 h (R = Ph) or 48 h (for R =
Et) at RT, whereupon the resulting suspension was cooled to 4 °C.
The precipitate formed was filtered off, washed with two 1-mL
portions of chloroform, and dried at RT in air.
10a. Yield: 66%. Mp: 154 °C (dec). Anal. Calcd for
C10H22N6Cl2O2Pt: C, 22.91; H, 4.23; N, 16.03. Found: C, 22.78; H,
4.19; N, 16.14. High-resolution ESI+-MS (MeOH, m/z): 452.133 ([M −
2Cl − H]+, calcd 452.132), 489.111 ([M − Cl]+, calcd 489.109),
525.093 ([M + H]+, calcd 525.085), 542.147 ([M + NH4]+, calcd
542.112). IR (KBr, selected bonds, cm−1): 3496(m), 3344(s),
3201(m) [ν(N−H)]; 3083(m), 2941(w-m), 2881(w) [ν(C−H)];
1664(m-s), 1626(vs) [ν(CN)]; 794(w), 700(w-m) [δ(C−H)].
1
TLC (eluent is chloroform:acetone = 1:1, v/v): Rf = 0.62. H NMR
(DMSO-d6, δ): 7.92 (s, br, 1H, NH), 6.90 (s, br, 1H, NH), 6.62 (s, br,
1H, NH), 2.89 (q, 2H, CH2), 1.81 (s, 3H, CH3), 1.25 (t, 3H, CH3).
10b. Yield: 69%. Mp: 149 °C (dec). Anal. Calcd for
C20H26N6Cl2O2Pt·3/4H2O: C, 36.29; H, 4.19; N, 12.70. Found: C,
36.28; H, 4.17; N, 12.65. High-resolution ESI+-MS (MeOH, m/z):
576.167 ([M − 2Cl − H]+, calcd 576.163), 613.143 ([M − Cl]+, calcd
613.140), 649.120 ([M + H]+, calcd 649.117), 666.149 ([M + NH4]+,
calcd 666.143), 687.077 ([M + K]+, calcd 687.073), 1261.260 ([2M −
Cl]+, calcd 1261.249), 1314.263 ([2M + NH4]+, calcd 1314.253),
1335.203 ([2M + K]+, calcd 1335.182). IR (KBr, selected bonds,
cm−1): 3496(m), 3373(m), 3299(s), 3227(m-s), 3185(m) [ν(N−H)];
3059(w-m), 2988(w-m), 2941(w-m), 2918(w), 2888(w), 2849(w)
[ν(C−H)]; 1671(s), 1629(vs) [ν(CN)]; 1598(m) [ν(CN) and/
or ν(CCAr)]; 1567(s) [δ(N−H), ν(CN), and/or ν(CCAr)];
777(w), 695(w) [δ(C−H)]. TLC (eluent is chloroform:acetone = 4:1,
9c. Yield: 83%. Mp: 156 °C (dec). Anal. Calcd for C18H22N6Cl2-
O2Pt·1/2H2O: C, 34.35; H, 3.68; N, 13.35. Found: C, 34.36; H, 3.66; N,
13.19. High-resolution ESI+-MS (MeOH, m/z): 548.125 ([M − 2Cl − H]+,
calcd 548.132), 585.100 ([M − Cl]+, calcd 585.109), 621.073 ([M + H]+,
calcd 621.085), 643.056 ([M + Na]+, calcd 643.067), 1168.198 ([2M −
2Cl − H]+, calcd 1168.210), 1205.173 ([2M − Cl]+, calcd 1205.187),
1258.179 ([2M + NH4]+, calcd 1258.190), 1789.230 ([3M − 2Cl − H]+,
calcd 1789.288), 1861.219 ([3M + H]+, calcd 1861.241), 1883.195
([3M + Na]+, calcd 1883.223). IR (KBr, selected bonds, cm−1): 3494(m),
3354(m-s), 3188(m-s) [ν(N−H)]; 3056(w), 3003(w), 2968(w), 2925(w)
[ν(C−H)]; 1669(m-s), 1623(vs) [ν(CN)]; 1600(s) [ν(CN) and/or
1
v/v): Rf = 0.57. H NMR (DMSO-d6, δ): 8.38 (s, br, 1H, NH), 7.85
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(d, 2H, o-CH), 7.55−7.40 (m, 3H, m- and p-CH), 7.16 (s, br, 2H,
NH2), 3.00 (q, 2H, CH2), 1.35 (t, 3H, CH3). Crystals suitable for
X-ray study were obtained from the reaction mixture at RT in air.
10:1, v/v, m/z): 671.111 ([M + Na]+, calcd 671.098), 691.166 ([M −
Cl + Me2SO]+, calcd 691.154), 1261.254 ([2M − Cl]+, calcd
1261.249), 1319.213 ([2M + Na]+, calcd 1319.208), 1339.267 ([2M −
Cl + Me2SO]+, calcd 1339.263). IR (KBr, selected bonds, cm−1):
3470(m), 3418(m), 3340(s), 3286(m-s) [ν(N−H)]; 3059(w-m),
2978(w-m), 2939(w-m), 2880(w), 2831(w) [ν(C−H)]; 1660(sh),
1626(vs) [ν(CN)]; 1564(s) [δ(N−H), ν(CN), and/or ν(C
CAr)]; 781(m), 694(m) [δ(C−H)]. TLC (eluent is chloroform:
1
acetone = 6:1, v/v): Rf = 0.57. H NMR (DMSO-d6, δ): 7.92 (s, br,
1H, NH), 7.81 (d, 2H, o-CH), 7.57−7.45 (m, 3H, m- and p-CH),
7.25 (s, br, 2H, NH2), 3.02 (q, 2H, CH2), 1.42 (t, 3H, CH3).
Crystals suitable for X-ray study were obtained from the reaction
mixture at RT in air.
vii. Preparation of [Pt(HNC(R)ONC(R′)NH2)2](NO3)2 (R = Et,
Ph; R′ = Me, Ph). A mixture of [PtCl2(HNC(R)ONC(R′)NH2)2]
(9b−9d and 10a−10d; 0.05 mmol) and AgNO3 (17 mg, 0.1 mmol)
was suspended in MeOH (2 mL). The suspension was kept in the dark
for 30 min under vigorous stirring, whereupon warm MeOH (10 mL,
55 °C) was added to the suspension to dissolve precipitated 7e and
then AgCl was filtered off. The filtrate was evaporated in vacuo, and
the residue was washed with CH2Cl2 (1 mL) and Et2O (1 mL).
10c. Yield: 81%. Mp: 152 °C (dec). Anal. Calcd for
C18H22N6Cl2O2Pt: C, 34.85; H, 3.57; N, 13.55. Found: C, 34.91; H,
3.49; N, 13.47. High-resolution ESI+-MS (MeOH, m/z): 621.090
([M + H]+, calcd 621.085), 643.073 ([M + Na]+, calcd 643.067), 659.046
([M + K]+, calcd 659.041), 1241.175 ([2M + H]+, calcd 1241.163),
1263.160 ([2M + Na]+, calcd 1263.145), 1279.135 ([2M + K]+, calcd
1279.119). IR (KBr, selected bonds, cm−1): 3495(m-s), 3448(m),
3376(m-s), 3321(s), 3219(m-s), 3187(m-s) [ν(N−H)]; 3062(w),
2980(w), 2932(w) [ν(C−H)]; 1658(s), 1622(vs) [ν(CN)];
1598(m), [ν(CN) and/or ν(CCAr)]; 1577(s) [δ(N−H), ν(C
N), and/or ν(CCAr)]; 785(m), 699(w) [δ(C−H)]. TLC (eluent is
1
chloroform:acetone = 2:1, v/v): Rf = 0.44. H NMR (DMSO-d6, δ):
8.61 (d, 2H, o-CH), 7.79 (s, br, 1H, NH), 7.70−7.50 (m, 3H, m- and
p-CH), 6.96 (s, br, 1H, NH), 6.64 (s, br, 1H, NH), 1.75 (s, 3H, CH3).
[7d](NO3)2. Yield: ca. 100%. Mp: 175 °C (dec). Anal. Calcd for
C20H26N8O8Pt·1/2H2O: C, 33.81; H, 3.83; N, 15.77. Found: C, 33.70;
H, 3.44; N, 15.63. High-resolution ESI+-MS (MeOH, m/z): 288.578
([M − 2NO3]2+, calcd 288.585), 304.591 [M− 2NO3 − H +
MeOH]2+, calcd 304.598), 576.152 ([M − 2NO3 − H]+, calcd
576.163), 608.178 ([M− 2NO3 − H + MeOH]+, 608.189). IR (KBr,
selected bonds, cm−1): 3432(s), 3427(s), 3367(s) [ν(N−H)];
3055(m), 2927(w), 2853(w) [ν(C−H)]; 1669(m) [ν(CN)];
1636(s), 1588(s) [ν(CN) and/or ν(CCAr)]; 1570(m) [δ(N−
H), ν(CN), and/or ν(CCAr)]; 1384(s) [ν(N−O)]; 780(w),
728(w), 706(w) [δ(C−H)]. 1H NMR (DMSO-d6, δ): 9.23 (s, br, 1H,
NH2), 9.21 (s, br, 1H, NH2), 7.84 (d, 2H, o-CH), 7.78 (t, 1H, p-CH),
7.68 (t, 2H, m-CH), 6.51 (s, br, 1H, NH), 2.46 (q, 2H, CH2), 0.84
(t, 3H, CH3). Crystals suitable for X-ray study were obtained by the
slow evaporation of an ethanol−nitromethane (1:1, v/v) solution at
RT in air.
10d. Yield: 87%. Mp: 153 °C (dec). Anal. Calcd for
C28H26N6Cl2O2Pt: C, 45.17; H, 3.52; N, 11.29. Found: C, 45.01; H,
3.49; N, 11.42. High-resolution ESI+-MS (MeOH, m/z): 709.147
([M − Cl]+, calcd 709.140), 745.123 ([M + H]+, calcd 745.117), 767.107
([M + Na]+, calcd 767.096), 783.080 ([M + K]+, calcd 783.073),
1453.262 ([2M − Cl]+, calcd 1453.249), 1489.234 ([2M + H]+, calcd
1489.226), 1511.221 ([2M + Na]+, calcd 1511.208), 1527.197 ([2M +
K]+, calcd 1527.182). IR (KBr, selected bonds, cm−1): 3482(m),
3363(m-s), 3288(m-s) [ν(N−H)]; 3059(w), 2922(w), 2859(w)
[ν(C−H)]; 1636(s), 1612(vs) [ν(CN)]; 1600(s) [ν(CN) and/
or ν(CCAr)]; 1578(s), 1570(s) [δ(N−H), ν(CN), and/or ν(C
CAr)]; 776(m), 694(m) [δ(C−H)]. TLC (eluent is chloroform:ace-
1
tone = 8:1, v/v): Rf = 0.46. H NMR (DMSO-d6, δ): 8.72 (d, 2H,
o-CH), 8.28 (s, br, 1H, NH), 7.73 (d, 2H, o-CH), 7.60−7.47 (m, 6H,
m- and p-CH), 7.26 (s, br, 2H, NH2).
vi. Preparation of [PtCl2(HNC(Et)ONC(Ph)NH2)2]. A solution
of the benzamidoxime PhC(NH2)NOH (0.2 mmol) in methanol
(0.5 mL) was added to a solution of 5b (0.10 mmol) in methanol
(2 mL). The mixture was left to stand at RT. After 48 h, crystals formed
were filtered off, washed with methanol (0.5 mL) and diethyl ether
(1 mL), and dried at RT in air.
[7e](NO3)2. Yield: ca. 100%. Mp: 173 °C (dec). Anal. Calcd for
C18H22N8O8Pt: C, 32.10; H, 3.29; N, 16.64. Found: C, 32.23;
H, 3.39; N, 16.52. High-resolution ESI+-MS (MeOH, m/z): 274.574
([M − 2NO3]2+, calcd 274.570), 548.134 ([M − 2NO3 − H]+, calcd
548.132). IR (KBr, selected bonds, cm−1): 3385(m), 3342(m),
3313(m), 3171(m-s) [ν(N−H)]; 2947(w) [ν(C−H)]; 1668(m),
1632(s) [ν(CN)]; 1601(s) [ν(CN) and/or ν(CC)]; 1580(m-s)
[δ(N−H), ν(CN), and/or ν(CCAr)]; 1384(vs) [ν(N−O)];
9b. Yield: 33%. Mp: 144 °C (dec). Anal. Calcd for
C20H26N6Cl2O2Pt·H2O: C, 36.04; H, 4.23; N, 12.61. Found: C,
35.88; H, 4.18; N, 12.57. High-resolution ESI+-MS (MeOH:Me2SO =
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777(w-m), 689(m) [δ(C−H)]. 1H NMR (DMSO-d6, δ): 10.73 (s, br,
1H, NH), 8.95 (s, br, 1H, NH2), 8.71 (s, br, 1H, NH2), 8.20 (d, 2H,
o-CH), 7.83 (m, 1H, p-CH), 7.66 (t, 2H, m-CH), 1.24 (s, 3H, CH3).
[8e](NO3)2. Yield: ca. 100%. Mp: 139 °C (dec). Anal. Calcd for
C18H22N8O8Pt·2H2O: C, 34.38; H, 4.85; N, 14.58. Found: C, 34.37; H,
4.95; N, 14.50. High-resolution ESI+-MS (MeOH, m/z): 274.569 ([M −
2NO3]2+, calcd 274.570), 548.142 ([M − 2NO3 − H]+, calcd 548.132).
IR (KBr, selected bonds, cm−1): 3443(m-s), 3328(m-s), 3149(m) [ν(N−
H)]; 2922(w), 2849(w) [ν(C−H)]; 1654(m), 1623(s) [ν(CN)];
1576(m-s) [δ(N−H), ν(CN), and/or ν(CCAr)]; 1384(vs) [ν(N−
O)]; 780(w-m), 687(m) [δ(C−H)]. 1H NMR (DMSO-d6, δ): 11.05 (s,
br, 1H, NH), 9.04 (s, br, 1H, NH2), 8.72 (s, br, 1H, NH2), 8.22 (d, 2H,
o-CH), 7.86 (t, 1H, p-CH), 7.70 (t, 2H, m-CH), 2.37 (s, 3H, CH3).
[7f](NO3)2. Yield: ca. 100%. Mp: 177 °C (dec). Anal. Calcd for
C28H26N8O8Pt·1/2H2O: C, 41.69; H, 3.37; N, 13.89. Found: C, 41.51;
H, 3.41; N, 13.82. High-resolution ESI+-MS (MeOH, m/z): 336.587
([M − 2NO3]2+, calcd 336.585), 672.167 ([M − 2NO3 − H]+, calcd
672.163). IR (KBr, selected bonds, cm−1): 3421(m-s), 3366(s),
3186(m-s) [ν(N−H)]; 3053(w), 2960(w), 2925(w), 2854(w) [ν(C−
H)]; 1622(vs) [ν(CN)]; 1601(vs) [ν(CN) and/or ν(CCAr)];
1560(m) [δ(N−H), ν(CN), and/or ν(CCAr)]; 1384(s) [ν(N−
1
O)]; 787(m), 692(m) [δ(C−H)]. H NMR (DMSO-d6, δ): 9.37 (s,
br, 1H, NH2), 9.35 (s, br, 1H, NH2), 7.99−7.97 (d + s, br, 3H, o-CH +
NH), 7.86−7.77 (m, 2H, 2p-CH), 7.72 (t, 2H, m-CH), 7.63−7.58
(m, 4H, o- and m-CH).
[8f](NO3)2. Yield: ca. 100%. Mp: 156 °C (dec). Anal. Calcd for
C28H26N8O8Pt·31/4H2O: C, 39.28; H, 3.83; N, 13.09. Found: C,
39.10; H, 3.54; N, 13.22. High-resolution ESI+-MS (MeOH, m/z):
336.578 ([M − 2NO3]2+, calcd 336.585), 672.158 ([M − 2NO3 −
H]+, calcd 672.163). IR (KBr, selected bonds, cm−1): 3429(m-s),
3316(m-s), 3134(m) [ν(N−H)]; 2935(w), 2854(w) [ν(C−H)];
1654(m), 1626(s) [ν(CN)]; 1596(s) [ν(CN) and/or ν(CCAr)];
1558(s) [δ(N−H), ν(CN), and/or ν(CC)]; 1384(vs) [ν(N−O)];
1
774(w-m), 693(m) [δ(C−H)]. H NMR (DMSO-d6, δ): 11.23 (s, br,
1H, NH), 8.64 (s, br, 1H, NH2), 8.62 (s, br, 1H, NH2), 8.26 (d, 2H,
o-CH), 7.87 (t, 1H, p-CH), 7.78−7.68 (m, 5H, CH), 7.57 (t, 2H, m-CH).
Crystals suitable for X-ray study were obtained by the slow evaporation of
an ethanol−nitromethane (1:1, v/v) solution at RT in air.
[8c](NO3)2. Yield: ca. 100%. Melting point and microanalytical
data were not obtained because of the relatively fast decomposition
of 35 right after the preparation. High-resolution ESI+-MS (MeOH,
m/z): 226.567 ([M − 2NO3]2+, calcd 226.572), 452.129 ([M − 2NO3 −
H]+, calcd 452.137). IR (KBr, selected bonds, cm−1): 3434(m-s),
3337(m), 3170(m) [ν(N−H)]; 2985(w), 2920(w), 2853(w) [ν(C−
H)]; 1638(vs), 1592(m) [ν(CN)]; 1565(m-s) [δ(N−H) and/or
ν(CN)]; 1384(vs) [ν(N−O)]; 793(w), 666(w) [δ(C−H)]. 1H
NMR (DMSO-d6, δ): 10.48 (s, br, 1H, NH), 8.88 (s, br, 1H, NH2),
8.65 (s, br, 1H, NH2), 2.81 (q, 2H, CH2), 2.24 (s, 3H, CH3), 1.23
(t, 3H, CH3).
ASSOCIATED CONTENT
* Supporting Information
■
S
X-ray crystallographic data in CIF format, molecular structures,
and tables of crystal data. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: bokach@nb17701.spb.edu (N.A.B.), kukushkin@
vk2100.spb.edu (V.Y.K.).
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
[8d](NO3)2. Yield: ca. 100%. Melting point and microanalytical
data were not obtained because of the relatively fast decomposition
of 35 right after the preparation. High-resolution ESI+-MS (MeOH,
m/z): 288.578 ([M − 2NO3]2+, calcd 288.585), 576.151 ([M − 2NO3 −
H]+, calcd 576.163). IR (KBr, selected bonds, cm−1): 3433(m-s),
3329(m), 3159(m) [ν(N−H)]; 3059(w-m), 2990(w), 2946(w)
[ν(C−H)]; 1653(s), 1630(vs) [ν(CN)]; 1596(s) [ν(CN) and/
or ν(CCAr)]; 1565(m-s) [δ(N−H), ν(CN), and/or ν(CC)];
1384(vs) [ν(N−O)]; 774(m), 698 (m) [δ(C−H)]. 1H NMR
(DMSO-d6, δ): 10.50 (s, br, 1H, NH), 8.45 (s, br, 1H, NH2), 8.43
(s, br, 1H, NH2), 7.67 (d, 2H, o-CH), 7.58−7.47 (m, 3H, m- and
p-CH), 2.84 (q, 2H, CH2), 1.29 (t, 3H, CH3).
The authors express their gratitude to the Russian Fund of Basic
Research (grants 12-03-00076 and 11-03-90417), Saint-Petersburg
State University (research grant 2011−2013). D.S.B. is grateful to
the Government of Saint-Petersburg and the Potanin fund for a
scholarships (2011).
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NOTE ADDED AFTER ASAP PUBLICATION
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Due to a production error, this paper was published on the
Web on May 8, 2012, with minor text errors. The corrected
version was reposted on May 10, 2012.
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