Amidrazone complexes from a cascade platinum(II)-mediated reaction between amidoximes and dialkylcyanamides

Article abstract of DOI:10.1021/ic4000878

The aryl amidoximes R′C₆H₄C(NH₂)=NOH (R′ = Me, 2a; H, 2b; CN, 2c; NO₂, 2d) react with the dialkylcyanamide platinum(II) complexes trans-[PtCl₂(NCNAlk ₂)₂] (Alk₂ = Me₂, 1a; C ₅H₁₀, 1b) in a 1:1 molar ratio in CHCl₃ to form chelated mono-addition products [3a-h]Cl, viz. [PtCl(NCNAlk₂){NH= C(NR₂)ON=C(C₆H₄R′)NH₂}]Cl (Alk₂ = Me₂; R′ = Me, a; H, b; CN, c; NO ₂, d; Alk₂ = C₅H₁₀; R′ = Me, e; H, f; CN, g; NO₂, h). In the solution, these species spontaneously transform to the amidrazone complexes [PtCl₂{NH=C(NR ₂)NC(C₆H₄R′)NNH₂}] (7a-h; 36-47%); this conversion proceeds more selectively (49-60% after column chromatography) in the presence of the base (PhCH₂)₃N. The observed reactivity pattern is specific for NCNAlk₂ ligands, and it is not realized for conventional alkyl-and arylnitrile ligands. The mechanism of the cascade reaction was studied by trapping the isocyanate intermediates [PtCl(NCO){NH=C(NR₂)NC(C₆H₄R′)NNH ₂}] (5a-h) and also by ESI-MS identification of the ammonia complexes [PtCl(NH₃){NH=C(NR₂)NC(C₆H₄R′ )NNH₂}]⁺ ([6a-h]⁺) in solution. The complexes [3a]Cl, [3c-h]Cl, 5a-h and 7a-h were characterized by elemental analyses, high resolution ESI-MS, IR, and ¹H NMR techniques, while 5b, 5d, 5g, 7b, and 7e were also studied using single-crystal X-ray diffraction.

Full text of DOI:10.1021/ic4000878

Article
pubs.acs.org/IC
Amidrazone Complexes from a Cascade Platinum(II)-Mediated
Reaction between Amidoximes and Dialkylcyanamides
Dmitrii S. Bolotin,† Nadezhda A. Bokach,*,† Andreii S. Kritchenkov,† Matti Haukka,‡
and Vadim Yu. Kukushkin*,†,§
†Department of Chemistry, Saint Petersburg State University, Universitetsky Pr. 26, 198504 Stary Petergof, Russian Federation
‡Department of Chemistry, University of Jyvaskyla, Finland, P.O. Box 35, FI-40014 University of Jyvaskyla, Finland
̈
̈
̈
̈
§Institute of Macromolecular Compounds of Russian Academy of Sciences, V.O. Bolshoii Pr. 31, 199004 Saint Petersburg,
Russian Federation
S
* Supporting Information
ABSTRACT: The aryl amidoximes R′C6H4C(NH2)NOH
(R′ = Me, 2a; H, 2b; CN, 2c; NO2, 2d) react with the di-
alkylcyanamide platinum(II) complexes trans-[PtCl2(NCNAlk2)2]
(Alk2 = Me2, 1a; C5H10, 1b) in a 1:1 molar ratio in CHCl3 to
form chelated mono-addition products [3a−h]Cl, viz. [PtCl-
(NCNAlk2){NHC(NR2)ONC(C6H4R′)NH2}]Cl (Alk2 =
Me2; R′ = Me, a; H, b; CN, c; NO2, d; Alk2 = C5H10; R′ = Me, e;
H, f; CN, g; NO2, h). In the solution, these species spontaneously
transform to the amidrazone complexes [PtCl2{NHC(NR2)-
NC(C6H4R′)NNH2}] (7a−h; 36−47%); this conversion pro-
ceeds more selectively (49−60% after column chromatography) in
the presence of the base (PhCH2)3N. The observed reactivity
pattern is specific for NCNAlk2 ligands, and it is not realized for conventional alkyl- and arylnitrile ligands. The mechanism of the cascade
reaction was studied by trapping the isocyanate intermediates [PtCl(NCO){NHC(NR2)NC(C6H4R′)NNH2}] (5a−h) and also by
ESI-MS identification of the ammonia complexes [PtCl(NH3){NHC(NR2)NC(C6H4R′)NNH2}]+ ([6a−h]+) in solution. The
1
complexes [3a]Cl, [3c−h]Cl, 5a−h and 7a−h were characterized by elemental analyses, high resolution ESI-MS, IR, and H NMR
techniques, while 5b, 5d, 5g, 7b, and 7e were also studied using single-crystal X-ray diffraction.
formed,4 and it means that these variances were recognized not
INTRODUCTION
■
only at the quantitative9 but also at the qualitative level when
In view of the general interest in ligand reactivity and organic
dialkylcyanamide and conventional nitrile ligands react with
transformations involving metal complexes,1 we have focused
the same reagent in absolutely different ways giving and,
our attention on reactions of metal-activated nitriles. This
fascinating area of research has been repeatedly reviewed along
consequently, different products.10
the years by some of us2 and other researchers.3 In particular,
Thus, we recently studied the platinum(IV)-mediated addi-
tion of PhC(NH2)NOH to dimethylcyanamide ligands in
we have observed additions of various ketoximes, aldoximes,
complex A1 (Scheme 1), and observed an unusual conversion
vic-dioximes, and functionalized oximes to nitriles at PtII, PtIV,
of the iminoacylated amidoxime in B1 givingafter the
intermolecular coupling with the nitrile groupchelate C1
featuring the new tridentate ligand.4a As an amplification of that
project, we attempted to carry out a similar transformation at
a platinum(II) center and, to our surprise, found that the
iminoacylated oximes easily convert to metal-bound function-
alized amidrazones (IUPAC name:11 carbamimidoylhydrazon-
amides; see Scheme 2 later) providing simple synthesis of these
species. Insofar as such conversions are not known and,
moreover, amidrazones12 were never obtained by this or any
other method that utilizes dialkylcyanamides and amidoximes,
we conducted a systematic study uncovering this chemistry, and
PdII, NiII, RhIII, and ReIV centers (see refs 2b and 4 and
references therein). It is worthwhile mentioning that although
the addition of oximes to (nitrile)[M] species in the beginning
of the project had purely basic interest, later it provided a
strong background for practical implications such as facile
syntheses of phthalocyanines,5 efficient ZnII-catalyzed hydration
of NCR species,6 generation of various 1,3,5-triazapentadiene
systems,7 and synthesis of amidines under neutral CoII-mediated
conditions.8
Despite the wealth of chemistry associated with the
nucleophilic addition of the oxime functionality HONC to
the so-called conventional NCR ligands (R = alkyl, aryl), only a
few works4 explored metal-bound dialkylcyanamides, NCNAlk2,
as substrates for the addition. These reports indicate substantial
distinctions in the reaction rates and the nature of products
Received: January 16, 2013
© XXXX American Chemical Society
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Scheme 1. Transformations of the mono-Addition Products of Benzamidoxime−Dimethylcyanamide Coupling
Scheme 2. Nucleophilic Addition of Amidoximes to Nitrile Platinum Complexes and Further Transformations of [3a−h]Cl to
Amidrazone Complexes 5a−h and 7a−h
our results are reported in this work. The scenario of our experi-
ments was the following. We, first, extended the PtII-mediated
formation of amidrazone ligands to a different combination of
dialkylcyanamides and amidoximes; second, we investigated the
reaction pathway by trapping intermediates and proposed the
mechanism of the reaction. The description follows these lines.
complexes 1a,b (in all possible combinations) in a 1:1 molar
ratio for 5 min at RT to form chelated mono-addition products
[3a−h]Cl (Scheme 2, a2). The reaction proceeds similarly
to that described in our previous work,4b and [3a]Cl·2H2O and
[3c−h]Cl·2H2O were isolated and characterized by CHN
1
analyses, high-resolution ESI+-MS, IR, and H NMR. Complex
[3b]Cl·2H2O was characterized previously.4b
RESULTS AND DISCUSSION
The reaction of complexes 1a,b with p-Me2NC6H4C(NH2)
NOH proceeds differently. Thus, the interplay between these
reactants for 10 min at either RT or even at 0 °C leads to a
broad spectrum of yet unidentified products. This observation
can be explained in terms of the strong M+ effect of the
dimethylamino group in p-Me2NC6H4C(NH2)NOH, which
increases the nucleophilicity of the amidoxime moiety and
makes reaction a2 (Scheme 2) less selective.
We found that [3a−h]Cl in the solution spontaneously
transform to furnish amidrazone complexes 7a−h (Table 1).
This cascade transformation proceeds for 26 h at 40 °C or for
5 days at RT in a chloroform solution to accomplish 7a−h, and
the latter species were isolated in 36−47% yields (Scheme 2, b2)
by column chromatography on silica gel. The reaction mixture
also contains a broad spectrum of yet unidentified products, and
this explains the rather low yields of 7a−h. The reaction also
■
As the starting materials for studying the platinum(II)-mediated
generation of the amidrazones, we addressed, on one hand,
the dialkylcyanamide platinum(II) complexes trans-[PtCl2-
(NCNAlk2)2] (Alk2 = Me2, 1a; C5H10, 1b) and, on the other
hand, the amidoximes p-R′C6H4C(NH2)NOH (R′ = Me, 2a;
H, 2b; CN, 2c; NO2, 2d). Reaction between complexes 1a,b
and amidoximes 2a−d (in all possible combinations) at 40 °C
in a 1:1 molar ratio in CHCl3 followed by the addition of
1 equiv of the base (PhCH2)3N with the further addition of
1 equiv of an acid (p-MeC6H4SO3H, abbreviated as PTSA)
results in the formation of amidrazone complexes 7a−h that
were isolated in 49−60% yields after column chromatography.
Reaction between the trans-(Dialkylcyanamide)PtII
Complexes and 1 equiv of Aryl Amidoximes. Aryl
amidoximes 2a−d react with dialkylcyanamide platinum(II)
B
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Table 1. Literal Abbreviations for Complexes [3]Cl−7
Scheme 3. Mechanism of the Cyanate to Chloride
Substitution
nos.
Alk2
Ar
[3a]Cl−7a
[3b]Cl−7b
[3c]Cl−7c
[3d]Cl−7d
[3e]Cl−7e
[3f]Cl−7f
[3g]Cl−7g
[3h]Cl−7h
Me2
C6H4Me-p
C6H5
Me2
Me2
C6H4CN-p
C6H4NO2-p
C6H4Me-p
C6H5
Me2
C5H10
C5H10
C5H10
C5H10
C6H4CN-p
C6H4NO2-p
takes place in nitromethane, dichloromethane, and acetone but
gives 7a−h in lower yields than that conducted in chloroform.
As far as the driving forces of the cascade reaction are
concerned, no reaction between any of 2a−d and dimethylcya-
namide in CDCl3 was observed for 7 days at room temperature.
These blank experiments suggest that the nucleophilic addition
of the amidoximes to the NCNAlk2 and further transformations
are PtII-mediated.
Reaction between [3a−h]Cl and 1 equiv of Base. The
addition of 1 equiv of the base (PhCH2)3N to a solution of
any of [3a−h]Cl results in substantial acceleration of the
conversion. On the contrary, the addition of 1 equiv of PTSA
completely inhibits the transformation of [3a−h]Cl. The reac-
tion pathway suggests participation of the deprotonated amide
moiety in the second nucleophilic addition, and therefore,
for this purpose we use base as the promoter. The same reaction
without the addition of a base proceeds much slower and less
selective. Thus, 1 equiv (PhCH2)3N promotes the conversion of
[3a−h]Cl to 5a−h by abstraction of HCl (Scheme 2, c2). The
reaction proceeds for 1 h at 40 °C accomplishing 5a−h that
were isolated in 74−87% yields. When 1,8-diazabicyclo[5.4.0]-
undec-7-ene (DBU) was used as the dehydrochlorinating agent,
yields of 5a−h decrease to ca. 45%, and these species are
generated along with a broad spectrum of unidentified products.
Compounds 5a−h are stable in the presence of (PhCH2)3N but
decompose in the presence of acids, e.g. PTSA or acetic acid.
Although we did not observe the generation of complexes 4 (see
Scheme 5 later), we believe based on our earlier observations,
however, that the reaction proceeds via the formation of the
tridentate ligand (see Scheme 1 and discussion later).
Acid-Catalyzed Hydrolysis of the Coordinated Cyanate
in 5a−h. Reaction between 5a−h and 1 equiv of an Acid.
Upon investigation of reaction b2 (Scheme 2) by ESI-MS, in
the spectra of the reaction mixtures, we observed the signals
of the molecular ions of both cyanate 5a−h and ammonia
[6a−h]+ (Scheme 3) complexes and suggested that these
species are derived from the hydrolysis. Therefore, we decided
to obtain the ammonia complexes selectively, by the addition of
an acid, and to study their further conversions to get more data
supporting the mechanism of the amidrazone generation.
Thus, addition of 1 equiv of PTSA to undried nitromethane−
methanol (1:1, v/v) solution of 5a−h at RT for 10 min leads
to the generation of cationic ammonia complexes [6a−h]-
(p-MeC6H4SO3) formed via the hydrolysis of the coordinated
cyanate (Scheme 3, a3 and b3; see Table 2S in the Supporting
Information for characteristic peaks of [6a−h](p-MeC6H4SO3)).
The reaction also proceeds with AcOH as an acid, but use of the
solid PTSA is more convenient from the synthetic viewpoint.
Compounds [6a−h](p-MeC6H4SO3) are rather unstable, and
they were detected in situ by ESI+-MS. It is worthwhile
mentioning that facile acid-promoted hydrolysis of N-bound
cyanates is well-known, and it was previously explored at
18
ReI,13 RuII,14 RuIII,15 CoIII,16 RhIII,15,17 and PtII metal centers.
It is generally believed that the hydrolysis proceeds via the
protonation of the ligated cyanate followed by the addition
of water to the NCO− ligand,15 and finally, carbon dioxide
eliminates to give the coordinated ammonia (Scheme 3).
Reaction between [6a−h]+ and Chloride. The addition of a
chloroform solution of [Bu4N]Cl (1.1 equiv) to nitromethane−
methanol (1:1, v/v) solution of in situ generated [6a−h]+
followed by keeping the reaction mixture for 90 min at 40 °C
leads to 7a−h (Scheme 3, c3). These compounds were isolated
from the reaction mixture by column chromatography.
It should be noticed that no structural changes were detected
when 5a−h and [Bu4N]Cl (1.1 equiv) were kept at 50 °C for
6 h in a nitromethane−methanol−chloroform solution
(Scheme 3, d4). The latter small experiment points out that
the direct substitution of the cyanate in 5a−h with the chloride
to give 7a−h is not possible under the reaction conditions.
Transformations of Methyl Carbamidoxime Derivatives.
The reaction between dialkylcyanamide complexes 1a,b and
MeC(NH2)NOH proceeds differently than those for the aryl
amidoximes (see above). This interaction leads to the chelated
complexes [PtCl(NCNAlk2){HNC(NR2)ONC(Me)-
NH2}]Cl (Alk2 = Me2 ([8a]Cl), C5H10 ([8b]Cl)), which are
structurally similar to [3a−h]Cl. Compounds [8a,b]Cl are less
reactive than complexes [3a−h]Cl, and no structure trans-
formations were observed for [8a,b]Cl for 24 h at 20−40 °C.
Furthermore, [8a,b]Cl are stable in the presence of 1 equiv of
(PhCH2)3N for 6 h at 40 °C, while in the presence of 1 equiv
of DBU at 40 °C, complexes [8a,b]Cl undergo slow unselective
degradation (Scheme 4).
Compounds [8a,b]Cl transform to the chelated dichloride
complexes [PtCl2{HNC(NR2)ONC(Me)NH2}] (R2 = Me2,
9a; C5H10, 9b) for 3 days at 60 °C (76 and 72% isolated yields,
respectively). We suggest that the Cl− in the reaction mixture
directs the reaction to dichloride monochelate species 9a,b.
We prepared [8a,b](OTf) with the so-called noncoordinated
anion, viz. OTf−, but even in this case we did not observe
the nucleophilic addition to the NCNAlk2 ligand. Complexes
[8a]Cl and 9a were identified in our previous work,4b
while [8b]Cl was characterized by ESI-MS in situ (415.060
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platinum(IV) chemistry and X-ray crystallography data
indicated the anomalously long [1.520(6) Å] oxime N−O
bond.4a Most likely, this step is rate determining in the absence
of base (26 h, 40 °C), but it dramatically accelerates by the
addition of (PhCH2)3N (1 h, 40 °C). It is, on the contrary,
inhibited by PTSA. On the basis of the observation of the effect
of substituents (different for Alk and Ar, see above), the
nucleophilic attack of the deprotonated form of the amide
group to the NCNAlk2 ligand can be suggested. The aromatic
substituent in the amidoxime favors deprotonation due to a
greater electron-withdrawing effect of the Ar substituent
comparing to Alk.
Scheme 4. Transformation of [8a,b]Cl
The heterolytic N−O bond cleavage in B2 gives the zwitter-
ionic intermediate C2, where the anionic and the cationic parts
are stabilized by the electron delocalization (D2). Similar
heterolytic splitting of the oxime N−O bond takes place, as
generally believed, in Beckmann19 and Tiemann20 rearrange-
ments. However, an alternative concerted mechanism of the
transformation cannot be ruled out.
In the intermediate, the rotation around the CN bond
provides suitable arrangement (E2) of the N centers for the
N−N bond formation and generation of the isocyanate
complexes F2; these species were isolated and identified. The
transformation of isocyanates to H2 could not be achieved by
the direct substitution with a chloride but easily occurs via the
acid-promoted hydrolysis and substitution of the metal-bound
ammonia with Cl−; the NH3/Cl− displacements at platinum(II)
centers had some precedents in the past.21
Analytical and Spectroscopy Data. Complexes [3a]-
Cl·2H2O, [3c−h]Cl·2H2O, 5a−h, and 7a−h give satisfactory
C, H, and N elemental analyses for the proposed formulas,
and they were also characterized by IR, high resolution ESI-MS,
1H NMR spectroscopy, and single-crystal X-ray diffraction (for
5b, 5d, 5g, 7b, and 7e).
Several complexes provide cocrystallization of solvent
molecules, which are reflected in the results of C, H, and N
elemental analyses, and this cocrystallization is typical for the
triazapentadiene complexes.7a,b,22 Thus, various complexes
bearing the triazapentadiene moiety are well-known as systems
that provide cocrystallization of solvent molecules.7a Moreover,
these species even serve as convenient models for studying
weak molecular interactions involving cocrystallized solvent;7b,22
([M − NCNC5H10 − Cl]+, calcd 415.064), 525.147 ([M − Cl]+,
calcd 525.149)). The characterization of 9a is given in the current
work.
The absence of the nucleophilic addition of the amide group
of MeC(NH2)NOH to a coordinated dialkylcyanamide
indicates that nucleophilicity of the amide moiety significantly
depends on the nature of the substituent in the molecule.
On the basis of observation of the effect of the substituent, the
nucleophilic attack of the deprotonated form of the amide
group to the NCNAlk2 ligand can be postulated. In this case,
the aromatic substituent in the amidoxime favors deprotonation
due to higher electronegativity of the Ar substituent compared
to Alk, which makes the amidoximes bearing the aromatic
group more reactive rather than MeC(NH2)NOH.
Plausible Mechanism for Cascade Generation of the
Amidrazone Complexes. Upon the basis of the experimental
data disclosed above, we suggest a plausible mechanism for
generation of amidrazones 7a−h from dialkylcyanamide
complexes 1a,b and amidoximes 2a−d. The reactions start as
the known4b nucleophilic addition of 1 equiv of an amidoxime
to a platinum-bound dialkylcyanamide (Scheme 2) to furnish
chelates [3a−h]Cl (Scheme 5, A2). The latter species undergo
the intramolecular nucleophilic attack by the NH2 group to the
nitrile C atom to give intermediates B2 that were not detected,
but similar dichelates were previously observed in the
Scheme 5. Plausible Mechanism for a Cascade Generation of the Amidrazone Complexes
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small variation of cocrystallization conditions for the triazapen-
tadiene systems often gives solvates of various composition. All
of these explain why the composition of some complexes for
microanalyses and for X-ray diffraction studies is different.
In the IR spectra of 5a−h and 7a−h, the PtII-bound organic
ligands exhibit a medium-to-strong band at 3448−3192 cm−1,
which can be attributed to the N−H stretches.23 The spectra also
display two CN absorption bands in the range of 1666−1601
cm−1 specific for the metal-bound 1,3,5-triazapentadienes.7a,b,24
The spectra of 5a−h represent a very strong band in the range
of 2270−2217 cm−1 specific for the platinum(II)-bound
cyanate.25 In addition, the spectra of 5c, 5g, 7c, and 7g display
medium to medium-to-strong intensity bands in the range of
2226−2243 cm−1 assignable to the CN stretches from the
p-substituted benzonitrile.23
Figure 1. Molecular structure of 7e with the atomic numbering
scheme. Thermal ellipsoids are given at the 50% probability level.
Positive mode high resolution ESI mass-spectra of nonionic
species 5a−h and 7a−h exhibit peaks corresponding to the
quasi-ion [M + H]+ and/or ions [M + Na]+, [M + K]+, [2 M +
H]+, [2 M + Na]+, and [2 M + K]+ or fragmentation ions,
i.e., [M − Cl]+ (5a−h and 7a−h), [M − NCO]+ (5a−h), and
[M − NCO − Cl − H]+ (5a−h); the latter fragmentations are
typical for platinum(II) chloride complexes.4a,26 Negative mode
high resolution ESI mass-spectra of nonionic species 5a−h and
7a−h display peaks corresponding to the quasi-ion [M − H]−
and/or ions [2 M − H]− (5a−h and 7a−h), [M − NMe2]−,
and [2 M − NMe2]− (7a−d). The spectra of ionic species
[3a−h]Cl and [6a−h](p-MeC6H4SO3) represent peaks from
the cation [M − Cl]+ ([3a−h]+) and [M − p-MeC6H4SO3]+
([6a−h]+) and the fragmentation ions [M − NCNAlk2 − Cl]+
([3a−h]+).
The 1H NMR spectra of 5a−d and 7a−d display two singlets
from the different NMe2 groups, while the spectra of 5e−h and
7e−h show two multiplets, where the lower-field signal is
assignable to the N(CH2)2 moieties and another peak to carbon
Figure 2. Molecular structure of 5d with the atomic numbering
scheme. Thermal ellipsoids are given at the 50% probability level.
1
chains of the NC5H10 groups. The H NMR spectra of 5a−h
and 7a−h exhibit two broad signals from the N−H resonances.
The low-field signal corresponds to the proton of the amidra-
zone amide group, while the high-field signal is from the imino-
proton with observable (in some cases) 2JPtH constant (34 Hz),
which is specific for platinum-bound imines.4a,27 The signals of
the hydrazone NMe2 moiety in 5a−d are shifted to higher-field
relatively to 7a−d at ca. 0.2 ppm, which may be accounted for
by the shielding effect of the cyanate ligand.
N−(CN)imine, N−(CN)hydrazone, and C−NR2 distances are
close to the normal single bonds30 [1.370(8)−1.385(2),
1.363(8)−1.374(6), and 1.340(2)−1.376(8) Å, correspond-
ingly]. In 5g, the C(13)−N(3) distance (1.143(9) Å) is the
normal triple bond.30 In 5b, 5d, and 5g, the C−N and the C−O
distances in the cyanate ligand fall in the intervals 1.070(5)−
1.159(4) Å and 1.196(8)−1.219(4) Å, respectively, which are
characteristic for N-coordinated cyanates.29,31 The N−N
distances [1.426(7)−1.449(2) Å] are specific for the normal
single N(sp2)−N(sp3) bonds.30
In the molecular structures of 5b, 5d, 5g, 7b, and 7e, the
(1,3,5-triazapentadiene)PtII rings have almost planar geometry.
All bond angles in these metallacycles are close to 120°, except
the (NC)imine−N−(CN)hydrazone angles, which range from
127.95(11) to 130.0(5)°, and the N−Pt−N angles, which are
close to 90°. The π-systems of the aromatic rings do not
conjugate with the (1,3,5-triazapentadiene)PtII system that can
be inferred from the inspection of the torsion angles, which are
in the range 70.00−88.84° between the cycles.
Characterizations of [3a]Cl·2H2O and [3c−h]Cl·2H2O are
similar to that described for [3b]Cl·2H2O.4b
X-Ray Structure Determinations. Molecular structures of
5b, 5d, 5g, 7b, and 7e indicate that all coordination polyhedra
exhibit a typical square-planar geometry (Figures 1 and 2).
All bond angles around the PtII centers are close to 90°, except
the N−Pt−Cl angles in dichloride complexes 7b and 7h;
N(4)−Pt(1)−Cl(2) for 7b and N(1)−Pt(1)−Cl(2) for 7h are
97.22(4) and 96.13(16)°, while N(1)−Pt(1)−Cl(1) for 7b and
N(5)−Pt(1)−Cl(1) for 7h are equal to 86.30(5) and
85.31(16)°, correspondingly. The Pt−Cl distances (2.3100(5)−
2.3301(16) Å) are specific for the PtII−Cl bonds.28 The
Pt−Nimine bond lengths (1.955(5)−1.9844(15) Å) exhibit values
characteristic for (imine)PtII species.24 The Pt−Nhydrazone bond
lengths (2.016(2)−2.0271(15) Å) have values characteristic for
PtII−N(sp2) species,28 and the Pt−Ncyanate bond distances
(2.005(2)−2.071(4) Å) are usual for (cyanate)PtII complexes.29
The C−Nimine and C−Nhydrazone bond lengths are the typical
CN double bonds, ranging from 1.294(2) to 1.300(4) Å and
from 1.299(6) to 1.306(3) Å, respectively, while the amide
FINAL REMARKS
■
The results obtained in this work could be considered from at
least three perspectives. First, the accumulated data in the area
of the nitrile chemistry from our4,10,32 and other groups33
demonstrate that the reactivity of dialkylcyanamides, NCNAlk2,
in many instances is different from that observed for the
E
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Figure 3. Our (A3) and known (B3) imidoylamidrazones.
analytical laboratory of the University of Eastern Finland. Electrospray
ionization mass-spectra were obtained on a Bruker micrOTOF
spectrometer equipped with an electrospray ionization (ESI) source.
The instrument was operated both in positive and in negative ion
mode using a m/z range of 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 a Me2SO−
MeOH mixture. In the isotopic pattern, the most intensive peak is
reported. TLC was performed on Silufol UV254 SiO2 plates. Infrared
spectra (4000−400 cm−1) were recorded on a Shimadzu FTIR-8400S
instrument in KBr pellets. 1H NMR spectra were measured on
a Bruker DPX 300 spectrometer in Me2CO-d6 and Me2SO-d6 at
ambient temperature; residual solvent signals were used as the internal
standard.
X-Ray Structure Determinations. The crystals of complexes 5b,
5d, 5g, 7b, and 7e were immersed in cryo-oil, mounted in a Nylon
loop, and measured at a temperature of 100 or 120 K. The X-ray
diffraction data were collected on a Bruker Kappa Apex II Duo, Bruker
Kappa Apex II, or Bruker Smart Apex II diffractometer using Mo Kα
radiation (λ = 0.710 73 Å). The APEX240 software packages were used
for cell refinements and data reductions. The structures were solved by
direct methods using the SHELXS-9741 program with the WinGX42
graphical user interface. A numerical absorption correction based on
crystal faces (SADABS)43 was applied to all data. Structural refine-
ments were carried out using SHELXL-97.41 In 5g, nitromethane of
crystallization was disordered and omitted from the final refinement.
The contribution of the disordered solvent to the calculated structure
factors was taken into account by using a SQUEEZE routine of
PLATON.44 The total residual electron count was found to be 66, and
it was equated with two nitromethane molecules. In all structures
(except 5g), the NH, NH2, and H2O hydrogen atoms were located
from the difference Fourier map but constrained to ride on their parent
nitrogen atom with Uiso = 1.5Ueq (parent atom). Other hydrogens were
positioned geometrically and constrained to ride on their parent atoms,
with C−H = 0.95−0.99 Å, N−H = 0.88 Å, and Uiso = 1.2−1.5Ueq
(parent atom). The crystallographic details are summarized in Table S2
(Supporting Information).
conventional nitrile substrates NCR (R = Alk, Ar). Thus, in this
work, we found a novel platinum(II)-mediated cascade reaction
between amidoximes and dialkylcyanamides furnishing coordi-
nated amidrazones. This reactivity pattern of dialkylcyanamides
NCNAlk2 is not realized for NCR, and the platinum(II)-
mediated generation of amidrazones is specific for NCNAlk2
ligands.
Second, we found a novel method for the synthesis of func-
tionalized amidrazones. The most developed methods leading
to these species include the reaction of hydrazines with nitriles,
iminoesters, imidoylhalides, amides, thioamides, amidines, and
their salts; aminolysis of hydrazonoylhalides; and the reduction
of formazanes and tetrazolium salts.12,34
Third, the acyclic systems with the atom sequence
R1NC(NR2R3)N(R4)C(R5)N−NR6R7 (Figure 3, A3) were
not previously reported. It should be noticed that a relevant
system picked in dashed lines in Figure 3 (B3) was synthesized
via the metal-free reaction of dicyclohexylcarbodiimide and
1,1,4-trisubstituted thiosemicarbazides.35
Furthermore, the obtained ligand system also relates to 1,3,5-
trazapentadiene metallacycles,36 which have been the subject
of significant attention for the past decade due to their
pH-dependent luminescence properties24,36,37 and catalytic activity.36
Additionally, 5a−h and 7a−h represent a new example of
platinum complexes having an amidrazone functionality,
coordinated via the N(sp2) hydrazide atom (Figure 4, A4).
Figure 4. Observed in this work (A4) and known (B4 and C4)
Synthetic Work. I. Nucleophilic Addition of 1 equiv of
p-R′C6H4C(NH2)NOH (R′ = Me, H, CN, NO2) to trans-
[PtCl2(NCNAlk2)2] (Alk2 = Me2, C5H10). A solution of any of the
amidoximes p-R′C6H4C(NH2)NOH (2a−d; 0.10 mmol) in chloro-
form (3 mL) was added dropwise for 20 min to a stirred solution of
trans-[PtCl2(NCNAlk2)2] (1a,b; 0.10 mmol) in chloroform (3 mL).
After 20 min, the solvent was evaporated under a vacuum to form oily
residues. The residues were washed with three 3-mL portions of dry
diethyl ether, crystallized under dry diethyl ether, and dried in the
air at RT.
coordination modes of amidrazones at platinum(II) centers.
The known (amidrazone)PtII species exhibit other coordination
modes (Figure 4, B4 and C4).38 In our case, the stabilization of
the six-membered amidrazone metallacycle is determined by
the existence of the carbamimidoyl fragment (picked in dashed
lines in Figure 4, A4) that provides the chelation.
We are currently attempting the extension of the observed
reaction to other metal centers and also to other push−pull
nitrile systems.
EXPERIMENTAL SECTION
■
Materials and Instrumentation. Solvents were obtained from
commercial sources and used as received. The amidoximes were
synthesized according to the literature methods.39 The complexes
[PtCl2(NCNAlk2)2] (R2 = Me2, C5H10) were synthesized in accord
with the published procedure;32 the cis- and trans-isomers were
separated by column chromatography on SiO2 (Silicagel 60 F254
0.063−0.200 mm, Merck). Microanalyses were carried out in the
,
[3a]Cl·2H2O yield: 89%. Anal. Calcd. for C14H22N6OCl2Pt·2H2O:
C, 28.39; H, 4.42; N, 14.19. Found: C, 28.43; H, 4.48; N, 14.14%.
F
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High resolution ESI+-MS (MeOH, m/z): 451.069 ([M − NCNMe2 −
Cl]+, calcd 451.061), 521.120 ([M − Cl]+, calcd 521.114). IR (KBr,
selected bonds, cm−1): 3419(s), 3363(s) ν(N−H); 3030(vw),
2984(vw), 2952(vw) ν(C−H); 2305 (m) ν(CN); 1660(m-s),
1620(m-s) ν(CN). 1H NMR (DMSO-d6, δ): 8.84 (s, br, 1H, NH2),
8.55 (s, br, 1H, NH2), 7.65 (s, br, 1H, NH), 7.43 (d, 3JHH = 8 Hz, 2H,
[3f]Cl·2H2O yield: 67%. Anal. Calcd for C19H28N6OCl2Pt·2H2O:
C, 34.66; H, 4.90; N, 12.76. Found: C, 34.81; H, 4.81; N, 12.64%.
High resolution ESI+-MS (MeOH, m/z): 479.092 ([M − Cl −
NCNMe2]+, calcd 479.085). IR (KBr, selected bonds, cm−1): 3416(s),
3358(m) ν(N−H); 3045(vw), 2932(w) ν(C−H); 2295(m-s) ν(C
1
N); 1666(s), 1626(vs) 1603(m) ν(CN). H NMR (DMSO-d6, δ):
3
8.86 (s, br, 1H, NH2), 8.54 (s, br, 1H, NH2), 7.75−7.72 (m, 4H, NH +
o-, p-CH), 7.61 (t, 2H, m-CH), 1.60−1.48 (m, 6H, CH2), 1.23−1.03
(m, 6H, CH2).
CH), 7.30 (d, JHH = 8 Hz, 2H, CH), 3.10 (s, 6H, N(CH3)2), 2.71
(s, 6H, N(CH3)2), 2.35 (s, 3H, ArCH3).
[3c]Cl·2H2O yield: 87%. Anal. Calcd. for C13H19N7OCl2Pt·2H2O:
C, 27.87; H, 3.84; N, 16.25. Found: C, 27.91; H, 3.83; N, 16.28%.
High resolution ESI+-MS (MeOH, m/z): 462.044 ([M − NCNMe2 −
Cl]+, calcd 462.040), 532.095 ([M − Cl]+, calcd 532.093). IR (KBr,
selected bonds, cm−1): 3424(s), 3360(s) ν(N−H); 3033(vw),
2988(vw), 2952(vw) ν(C−H); 2305(m) and 2247(s) ν(CN);
1666(m-s), 1624(m-s) ν(CN). 1H NMR (DMSO-d6, δ): 8.88 (s, br,
[3g]Cl·2H2O yield: 80%. Anal. Calcd. for C20H27N7OCl2Pt·2H2O:
C, 35.09; H, 4.71; N, 14.32. Found: C, 35.12; H, 4.59; N, 14.47%.
High resolution ESI+-MS (MeOH, m/z): 502.073 ([M − NCNC5H10
−
Cl]+, calcd 502.072), 612.157 ([M − Cl]+, calcd 612.156). IR (KBr,
selected bonds, cm−1): 3410 (s), 3368 (s) ν(N−H); 3038 (vw), 2992
(vw), 2966 (vw) ν(C−H); 2268(m) and 2228(s) ν(CN); 1666
(m-s), 1623 (m-s) ν(CN). 1H NMR (DMSO-d6, δ): 8.93 (s, br, 1H,
NH2), 8.64 (s, br, 1H, NH2), 7.70 (s, br, 1H, NH), 7.65 (d, 3JHH = 8 Hz,
2H, CH), 7.32 (d, 3JHH = 8 Hz, 2H, CH)), 3.24−2.95 (m, 8H, NCH2),
1.66−1.50 (m, 6H, CH2), 1.30−1.07 (m, 6H, CH2).
1H, NH2), 8.57 (s, br, 1H, NH2), 7.88 (s, br, 1H, NH), 7.82 (d, 3JHH
=
3
8 Hz, 2H, CH), 7.59 (d, JHH = 8 Hz, 2H, CH), 3.15 (s, 6H,
N(CH3)2), 2.76 (s, 6H, N(CH3)2).
[3d]Cl·2H2O yield: 82%. Anal. Calcd. for C13H19N7O3Cl2Pt·2H2O:
C, 25.01; H, 3.87; N, 15.70. Found: C, 25.00; H, 3.76; N, 15.79%.
High resolution ESI+-MS (MeOH, m/z): 482.037 ([M − NCNMe2 −
Cl]+, calcd 482.030), 552.086 ([M − Cl]+, calcd 552.083). IR (KBr,
selected bonds, cm−1): 3421(s), 3360(s) ν(N−H); 3030(vw),
2986(vw), 2952(vw) ν(C−H); 2305 (m) ν(CN); 1666(m-s),
1622(m-s) ν(CN), 1520(s) ν(NO)as, 1342(s) ν(NO)s. 1H
NMR (DMSO-d6, δ): 8.90 (s, br, 1H, NH2), 8.59 (s, br, 1H, NH2),
7.93 (s, br, 1H, NH), 7.82 (d, 3JHH = 8 Hz, 2H, CH), 7.55 (d, 3JHH = 8
Hz, 2H, CH), 3.15 (s, 6H, N(CH3)2), 2.77 (s, 6H, N(CH3)2).
[3h]Cl·2H2O yield: 84%. Anal. Calcd. for C19H27N7O3Cl2Pt·2H2O:
C, 32.39; H, 4.58; N, 13.92. Found: C, 32.38; H, 4.49; N, 13.93%.
High resolution ESI+-MS (MeOH, m/z): 522.063 ([M − NCNC5H10
−
Cl]+, calcd 522.061), 632.147 ([M − Cl]+, calcd 623.146). IR (KBr,
selected bonds, cm−1): 3415 (s), 3368 (s) ν(N−H); 3038 (vw), 2992
(vw), 2969 (vw) ν(C−H); 2288 (m) ν(CN); 1666 (m-s), 1624
1
(m-s) ν(CN), 1520(s) ν(NO)as, 1342(s) ν(NO)s. H NMR
(DMSO-d6, δ): 8.95 (s, br, 1H, NH2), 8.64 (s, br, 1H, NH2), 7.72 (s, br,
3
3
1H, NH), 7.62 (d, JHH = 8 Hz, 2H, CH), 7.34 (d, JHH = 8 Hz, 2H,
CH), 3.19−2.98 (m, 8H, NCH2), 1.66−1.52 (m, 6H, CH2), 1.31−1.12
(m, 6H, CH2).
ii. Intramolecular Nucleophilic Addition to Cyanamide Ligand
Followed by Rearrangement. A solution of freshly prepared [3]Cl
(see above) in chloroform (2 mL) was kept for 7 min at RT,
whereupon a solution of tribenzylamine (0.10 mmol) in chloroform
(1 mL) was added. The reaction mixture was kept at 40 °C for 1 h,
and then the solution was cooled to RT. A precipitate formed (for
5b−d, 5g, and 5h) was filtered off, washed with two 0.5-mL portions
of chloroform, and dried in the air at RT, while solutions of 5a, 5e, and
5f were transferred to a short (l = 7 cm, d = 0.7 cm) column filled with
silica gel [eluent: chloroform−nitromethane (5:1, v/v, for 5a) or
chloroform (12 mL; for 5e and 5f), whereupon elution was performed
with chloroform−nitromethane (3:2, v/v) mixture until separation of
the first fraction]. The product (5a, 5e, and 5f) was isolated from the
column in the first fraction. The solvent was evaporated in vacuo to
give cyanate complexes 5a, 5e, and 5f that contain a small amount (ca.
5−10% relatively to the isolated yield of 5) of corresponding dichloride
complex 7a, 7e, or 7f.
[3e]Cl·2H2O yield: 84%. Anal. Calcd. for C20H30N6OCl2Pt·2H2O:
C, 35.72; H, 5.10; N, 12.50. Found: C, 35.81; H, 5.12; N, 12.53%.
High resolution ESI+-MS (MeOH, m/z): 491.098 ([M − NCNC5H10
−
Cl]+, calcd 491.092), 601.181 ([M − Cl]+, calcd 601.176). IR (KBr,
selected bonds, cm−1): 3410 (s), 3368 (s) ν(N−H); 3033 (vw), 2992
(vw), 2966 (vw) ν(C−H); 2288 (m) ν(CN); 1666 (m-s), 1623
1
(m-s) ν(CN). H NMR (DMSO-d6, δ): 8.91 (s, br, 1H, NH2), 8.55
(s, br, 1H, NH2), 7.60 (s, br, 1H, NH), 7.42 (d, 3JHH = 8 Hz, 2H, CH),
3
7.20 (d, JHH = 8 Hz, 2H, CH), 3.15−2.98 (m, 8H, NCH2), 2.33
(s, 3H, ArCH3), 1.62−1.48 (m, 6H, CH2), 1.22−1.03 (m, 6H, CH2).
5a yield: 58%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.47. High resolution ESI+-MS (MeOH, m/z): 441.140 ([M − NCO
− Cl − H]+, calcd 441.136), 478.117 ([M − NCO]+, calcd 478.112),
484.147 ([M − Cl]+, calcd 484.142), 521.124 ([M + H]+, calcd
521.118), 543.109 ([M + Na]+, calcd 543.100), 559.079 ([M + K]+,
calcd 559.074), 997.223 ([2 M − NCO]+, calcd 997.225), 1003.260
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472.101), 509.087 ([M − NCO]+, calcd 509.077), 515.100 ([M −
Cl]+, calcd 515.106), 574.070 ([M + Na]+, calcd 574.065), 590.043
([M + K]+, calcd 590.039). High resolution ESI−-MS (MeOH, m/z):
550.078 ([M − H]−, calcd 550.068), 1100.159 ([2 M − H]−, calcd
1100.143). IR (KBr, selected bonds, cm−1): 3430(m-s), 3390(m-s),
3230(w-m) ν(N−H); 2231(vs) ν(OCN); 1666(vs), 1638(m-s)
ν(CN); 1521(m-s) δ(N−H) and ν(NO)as, 1346(s) ν(NO)s.
1H NMR (Me2CO-d6, δ): 9.05 (s, br, 1H, NH), 8.31 (d, 3JHH = 8 Hz,
([2 M − Cl]+, calcd 1003.252), 1062.219 ([2 M + Na]+, calcd
1062.210), 1078.195 ([2 M + K]+, calcd 1078.184). High resolution
ESI−-MS (MeOH, m/z): 519.109 ([M − H]−, calcd 519.102),
1038.225 ([2 M − H]−, calcd 1038.213). IR (KBr, selected bonds,
cm−1): 3448(m), 3379(m-s) ν(N−H); 2217(vs) ν(OCN); 1665(vs),
3
2H, CH), 7.82 (d, JHH = 8 Hz, 2H, CH), 5.98 (s, br, 1H, NH), 3.00
(s, 6H, NMe2), 2.55 (s, 6H, NMe2). Crystals suitable for X-ray study
were obtained by slow evaporation of a nitromethane−methanol
solution in the air at RT.
1
1624(m-s) ν(CN); 1551(s) δ(N−H). H NMR (Me2CO-d6, δ):
3
3
8.84 (s, br, 1H, NH), 7.42 (d, JHH = 8 Hz, 2H, CH), 7.28 (d, JHH
=
2
8 Hz, 2H, CH), 5.98 (s+d, JPtH = 34 Hz, br, 1H, NH), 3.05 (s, 6H,
N(CH3)2), 2.58 (s, 6H, N(CH3)2), 2.39 (s, 3H, ArCH3).
5e yield: 65%. TLC (eluent: chloroform/acetone = 5:1, v/v) Rf =
0.51. High resolution ESI+-MS (MeOH, m/z): 521.200 ([M − NCO −
Cl − H] , calcd 521.199), 558.176 ([M − NCO]+, calcd 558.175),
+
564.203 ([M − Cl]+, calcd 564.205), 601.182 ([M + H]+, calcd
601.181), 623.164 ([M + Na]+, calcd 623.163), 639.138 ([M + K]+,
calcd 639.136), 1157.335 ([2 M − NCO]+, calcd 1157.348), 1163.360
([2 M − Cl]+, calcd 1163.377), 1200.338 ([M + H]+, calcd 1200.354),
1222.319 ([2 M + Na]+, calcd 1222.336), 1239.293 ([2 M + K]+,
calcd 1239.310). High resolution ESI−-MS (MeOH, m/z): 599.173
([M − H]−, calcd 599.165), 1198.342 ([2 M − H]−, calcd 1198.338).
IR (KBr, selected bonds, cm−1): 3451(m), 3361(m) ν(N−H); 2938(s),
5b yield: 74%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.42. Anal. Calcd for C13H19N6OClPt·1/2H2O: C, 30.33; H, 3.92; N,
16.32. Found: C, 30.64; H, 3.86; N, 16.10%. High resolution ESI+-MS
(MeOH, m/z): 464.093 ([M − NCO]+, calcd 464.092), 470.102
([M − Cl]+, calcd 470.121), 529.081 ([M + Na]+, calcd 529.080),
545.054 ([M + K]+, calcd 545.054), 1034.165 ([2 M + Na]+, calcd
1034.171), 1050.138 ([2 M + K]+, calcd 1050.145). High resolution
ESI−-MS (MeOH, m/z): 505.086 ([M − H]−, calcd 505.082),
1010.197 ([2 M − H]−, calcd 1010.173). IR (KBr, selected bonds,
cm−1): 3382(m), 3245(m), 3221(m) ν(N−H); 2250(vs) ν(OCN);
1666(vs), 1619(m-s) ν(CN); 1515(s) δ(N−H). 1H NMR
(Me2CO-d6, δ): 9.03 (s, br, 1H, NH), 7.55−7.45 (m, 5H, CH), 5.99
2852(m-s) ν(C−H); 2266(vs) ν(OCN); 1659(vs), 1621(s) ν(CN);
1
1528(m) δ(N−H). H NMR (Me2CO-d , δ): 9.28 (s, br, 1H, NH),
6
7.37 (d, 3JHH = 8 Hz, 2H, CH), 7.29 (d, 3JHH = 8 Hz, 2H, CH), 6.41 (s,
br, 1H, NH), 3.40−3.20 (m, 8H, NCH2), 1.65−1.55 (m, 6H, CH2),
1.20−1.10 (m, 6H, CH2).
2
(s+d, JPtH = 34 Hz, br, 1H, NH), 3.04 (s, 6H, NMe2), 2.57 (s, 6H,
NMe2). Crystals suitable for X-ray study were obtained by slow
evaporation of a nitromethane−methanol solution in the air at RT.
5f yield: 52%. TLC (eluent: chloroform/acetone = 5:1, v/v) Rf =
0.53. High resolution ESI+-MS (MeOH, m/z): 507.185 ([M − NCO −
Cl − H] , calcd 507.183), 544.162 ([M − NCO]+, calcd 544.159),
+
5c yield: 85%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.32. Anal. Calcd for C14H18N7OClPt·H2O: C, 30.63; H, 3.67; N,
17.86. Found: C, 30.58; H, 3.74; N, 17.94%. High resolution ESI+-MS
(MeOH, m/z): 489.094 ([M − NCO]+, calcd 489.088), 495.121
([M − Cl]+, calcd 495.117), 554.084 ([M + Na]+, calcd 554.075),
570.060 ([M + K]+, calcd 570.049). High resolution ESI−-MS
(MeOH, m/z): 530.088 ([M − H]−, calcd 530.078), 1060.179
([2 M − H]−, calcd 1060.164). IR (KBr, selected bonds, cm−1):
3432(m), 3403(m), 3345(m), 3278(w-m) ν(N−H); 2245(vs)
ν(OCN); 2232(m-s) ν(CN); 1664(vs), 1648(s) ν(CN);
550.191 ([M − Cl]+, calcd 550.189), 609.151 ([M + Na]+, calcd
609.147), 625.123 ([M + K]+, calcd 625.121), 1129.310 ([2 M −
NCO]+, calcd 1129.317), 1138.336 ([2 M − Cl]+, calcd 1135.346),
1194.294 ([2 M + Na]+, calcd 1194.307), 1210.265 ([2 M + K]+,
calcd 1210.278). High resolution ESI−-MS (MeOH, m/z): 585.160
([M − H]−, calcd 585.149), 1170.321 ([2 M − H]−, calcd 1170.307).
IR (KBr, selected bonds, cm−1): 3448(m), 3375(m) ν(N−H); 2932(s),
2853(m-s) ν(C−H); 2269(vs) ν(OCN); 1659(vs), 1624(s) ν(CN);
1
1521(m) δ(N−H). H NMR (Me2CO-d , δ): 9.37 (s, br, 1H, NH),
6
7.49−7.45 (m, 5H, Ph), 6.44 (s+d, 2JPtH = 34 Hz, br, 1H, NH), 3.40−
3.20 (m, 8H, NCH2), 1.65−1.55 (m, 6H, CH2), 1.20−1.10 (m, 6H, CH2).
1
1539(s) δ(N−H). H NMR (Me2CO-d63, δ): 9.02 (s, br, 1H, NH),
3
7.88 (d, JHH = 8 Hz, 2H, CH), 7.76 (d, JHH = 8 Hz, 2H, CH), 5.96
(s, br, 1H, NH), 3.00 (s, 6H, NMe2), 2.55 (s, 6H, NMe2).
5g yield: 86%. TLC (eluent: chloroform/acetone = 3:1, v/v) Rf =
0.43. Anal. Calcd for C20H26N7OClPt·1/2CHCl3: C, 36.71; H, 3.98;
N, 14.62. Found: C, 36.70; H, 4.05; N, 14.62%. High resolution
5d yield: 87%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.34. Anal. Calcd for C13H18N7O3ClPt·1/2CHCl3: C, 26.56; H, 3.05;
N, 16.06. Found: C, 26.50; H, 3.21; N, 15.93%. High resolution
ESI+-MS (MeOH, m/z): 472.103 ([M − NCO − Cl − H]+, calcd
+
ESI+-MS (MeOH, m/z): 532.179 ([M − NCO − Cl − H] , calcd
532.173), 569.155 ([M − NCO]+, calcd 569.150), 575.181 ([M − Cl]+,
H
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calcd 575.179), 634.142 ([M + Na]+, calcd 634.138), 650.117 ([M +
K]+, calcd 650.112), 1243.280 ([2 M + Na]+, calcd 1244.287), 1261.254
([2 M + K]+, calcd 1261.260). High resolution ESI−-MS (MeOH, m/z):
610.156 ([M − H]−, calcd 610.140), 1220.309 ([2 M − H]−, calcd
1220.289). IR (KBr, selected bonds, cm−1): 3429(m-s), 3367(m) ν(N−
H); 2943(s), 2859(m-s) ν(C−H); 2270(vs) ν(OCN); 2231(m-s)
ν(CN); 1660(vs), 1631(m-s) ν(CN); 1526(m) δ(N−H). 1H
NMR (Me2CO-d6, δ): 9.60 (s, br, 1H, NH), 7.91 (d, 3J HH = 8 Hz, 2H,
CH), 7.77 (d, 3 JHH = 8 Hz, 2H, CH), 6.45 (s+d, 2JPtH = 34 Hz, br, 1H,
NH), 3.40−3.20 (m, 8H, NCH2), 1.70−1.40 (m, 12H, CH2). Crystals
suitable for X-ray study were obtained by slow evaporation of a
nitromethane−methanol solution in the air at RT.
12 mL) mixture, then a chloroform−nitromethane (3:2, v/v) mixture).
The solvent was evaporated in vacuo at RT to give pure amidrazone
complex 7 in ca. 50% yield (based on 5). Below we give the yields of
7a−h for more convenient procedure A, which provides ca. 5% higher
yields.
7a yield: 51%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.49. Anal. Calcd for C13H21N5Cl2Pt·H2O: C, 29.38; H, 4.36; N, 13.18.
Found: C, 29.47; H, 4.18; N, 13.01%. High resolution ESI+-MS
(MeOH, m/z): 478.110 ([M − Cl]+, calcd 478.108), 536.069 ([M +
Na]+, calcd 536.067), 552.042 ([M + K]+, calcd 552.040), 991.182
([2 M − Cl]+, calcd 991.185), 1027.158 ([2 M + H]+, calcd 1027.162),
1049.138 ([2 M + Na]+, calcd 1049.144), 1065.112 ([2 M + K]+, calcd
1065.118). High resolution ESI−-MS (MeOH, m/z): 469.025 ([M −
NMe2]−, calcd 469.027), 512.061 ([M − H]−, calcd 512.069),
1025.137 ([2 M − H]−, calcd 1025.146). IR (KBr, selected bonds,
cm−1): 3300(m), 3246(w-m) ν(N−H); 1659(vs), 1614(m-s) ν(CN);
1506(m-s) δ(N−H). 1H NMR (Me2CO- d6, δ): 8.79 (s, br, 1H, NH),
5h yield: 85%. TLC (eluent: chloroform/acetone = 3:1, v/v) Rf =
0.53. Anal. Calcd for C18H26N6O2Cl2 Pt·1/2CHCl3: C, 30.40; H,
3.42; N, 12.10. Found: C, 30.43; H, 3.45; N, 12.16%. High resolution
+
ESI+-MS (MeOH, m/z): 552.169 ([M − NCO − Cl − H] , calcd
552.163), 589.145 ([M − NCO]+, calcd 589.140), 595.172 ([M −
Cl]+, calcd 595.169), 654.133 ([M + Na]+, calcd 654.128), 670.107
([M + K]+, calcd 670.102), 1284.259 ([2 M + Na]+, calcd 1284.266),
1301.231 ([2 M + K]+, calcd 1301.240). High resolution ESI−-MS
(MeOH, m/z): 630.147 ([M − H]−, calcd 630.130), 1260.280
([2 M − H]−, calcd 1260.269). IR (KBr, selected bonds, cm−1):
3437(m-s), 3390(m-s) ν(N−H); 2941(s), 2855(m-s) ν(C−H);
2270(vs) ν(OCN); 1651(vs), 1633(m-s) ν(CN); 1516(m-s)
δ(N−H) and ν(NO)as, 1345(s) ν(NO)s. 1H NMR (Me2CO- d6, δ):
2
2
7.40 (d, JHH = 8 Hz, 2H, CH), 7.27 (d, JHH = 8 Hz, 2H, CH), 6.06
(s, br, 1H, NH), 3.05 (s, 6H, N(CH3)2), 2.72 (s, 6H, N(CH3)2), 2.38
(s, 3H, ArCH3).
3
9.68 (s, br, 1H, NH), 8.35 (d, JHH = 9 Hz, 2H, CH), 7.85 (d,
3J
= 9 Hz, 2H, CH), 6.43 (s, br, 1H, N H), 3.40−3.20 (m, 8H,
HH
NCH2), 1.70−1.40 (m, 12H, CH2).
7b yield: 59%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.38. Anal. Calcd for C12H19N5Cl2Pt: C, 28.87; H, 3.84; N, 14.03.
Found: C, 29.03; H, 3.76; N, 14.17%. High resolution ESI+-MS
(MeOH, m/z): 464.101 ([M − Cl]+, calcd 464.092), 522.060 ([M +
Na]+, calcd 522.051), 538.034 ([M + K]+, calcd 538.025), 963.161
([2 M − Cl]+, calcd 963.154), 1021.119 ([2 M + Na]+, calcd
1021.113), 1037.092 ([2 M + K]+, calcd 1037.087). High resolution
ESI−-MS (MeOH, m/z): 455.004 ([M − NMe2]−, calcd 455.011),
498.046 ([M − H]−, calcd 498.053), 954.063 ([2 M − NMe2]−, calcd
954.073), 997.105 ([2 M − H]−, calcd 997.115). IR (KBr, selected
bonds, cm−1): 3308(m), 3227(m) ν(N−H); 1664(vs), 1616(m-s)
ν(CN); 1516(m-s) δ(N−H). 1H NMR (Me2CO-d 6, δ): 8.90 (s, br,
1H, NH), 7.53−7.45 (m, 5H, Ph), 6.08 (s, br, 1H, NH), 3.04 (s, 6H,
iii. Hydrolysis of the Coordinated Cyanate. A solution of PTSA
(0.10 mmol) in acetone (1 mL) was added to a solution of 5 (0.10 mmol)
in a nitromethane−methanol (1:1, v/v; 2 mL) mixture, and the solution
was kept at RT. After 10 min, a 5-μL aliquot of the homogeneous
solution obtained was diluted with methanol (1 mL), and the products
were identified by ESI-MS+ without liberation from the reaction
mixture. See Table 2S (Supporting Information) for characteristic peaks
of [6a−h](p-MeC6H4SO3).
iv. Preparation of 7a−h. Procedure A. One-Pot Preparation from
Platinum Complexes 1a,b and Amidoximes 2a−d. Powder of
aromatic amidoxime 2 (0.1 mmol) was added to a vigorously stirred
solution of complex 1 (0.1 mmol) in chloroform (2 mL) at RT. After
5 min, a solution of (PhCH2)3N (0.1 mmol) in chloroform (1 mL)
was added to the stirred solution, whereupon the mixture was stirred
at 40 °C. Then, a solution of PTSA (0.1 mmol) in a nitromethane−
methanol (1:1, v/v) mixture (1 mL) was added to the reaction mixture,
and it was kept on stirring at 40 °C for an additional 2 h, whereupon
the solvent was evaporated in vacuo at RT. A residue was completely
dissolved in a chloroform−nitromethane (5:1, v/v) mixture (volume
varies in the range of 2−5 mL depending on particular complexes), and
the solution obtained was transferred to a short (l = 7 cm, d = 0.7 cm)
column and chromatographed on silica gel (eluent: chloroform−
nitromethane (5:1, v/v, 12 mL), and then a chloroform−nitromethane
(3:2, v/v) mixture until eluation of the first fraction). The product
was isolated from the column in the first fraction. The solvent was
evaporated in vacuo at RT to give pure amidrazone complex 7.
Procedure B. Substitution of the Ammonia with the Chloride in
[6]+. A solution of tetrabuthylammonium chloride (0.15 mmol) in
chloroform (0.5 mL) was added to the solution (3 mL) of [6](p-
MeC6H4SO3) right after its preparation, and the reaction mixture was
kept at 40 °C for 2 h, whereupon the solvent was evaporated in vacuo
at RT to dryness. The residue was dissolved in a chloroform−
nitromethane (2:1, v/v; 2 mL) mixture. The resulting solution was
transferred to a short column (l = 7 cm, d = 0,7 cm) and chromato-
graphed on silica gel (eluent: chloroform−nitromethane (5:1, v/v;
N(CH3)2), 2.72 (s, 6H, N(CH )2). Crystals suitable for X-ray study
3
were obtained by slow evaporation of a nitromethane solution in the
air at RT.
7c yield: 60%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.33. Anal. Calcd for C13H18N6Cl2 Pt·1/4H O: C, 29.53; H, 3.53; N,
2
15.89. Found: C, 29.36; H, 3.66; N, 16.05%. High resolution ESI+-MS
(MeOH, m/z): 547.046 ([M + Na]+, calcd 547.046), 563.026 ([M +
K]+, calcd 563.020). High resolution ESI−-MS (MeOH, m/z): 509.034
([M − Me]−, calcd 509.033), 523.050 ([M − H]−, calcd 523.049). IR
(KBr, selected bonds, cm−1): 3371(m), 3217(m) ν(N−H); 2243(m)
ν(CN); 1666(vs), 1624(m-s) ν(CN); 1528(m-s) δ(N−H).
2
1H NMR (Me2CO-d6, δ): 9.13 (s, br, 1H, NH), 7.91 (d, JHH = 9
2
Hz, 2H, CH), 7.79 (d, JHH = 9 Hz, 2H, C H), 6.13 (s, br, 1H, NH),
3.02 (s, 6H, N(CH3)2), 2.70 (s, 6H, N(CH3)2).
I
dx.doi.org/10.1021/ic4000878 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Found: C, 36.47; H, 4.44; N, 13.49%. High resolution ESI+-MS
(MeOH, m/z): 569.154 ([M − Cl]+, calcd 569.150), 627.110 ([M +
Na]+, calcd 627.109). High resolution ESI−-MS (MeOH, m/z):
603.119 ([M − H]−, calcd 603.111), 1207.242 ([2 M − H]−, calcd
1207.231). IR (KBr, selected bonds, cm−1): 3366(m-s) ν(N−H);
2943(s), 2856(m-s) ν(C−H); 2226(m) ν(CN); 1655(vs),
1
1620(m-s) ν(CN); 1524(m) δ(N−H). H NMR (Me2SO-d6, δ):
7d yield: 55%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.37. Anal. Calcd for C12H18N6O2Cl2Pt·H2O: C, 25.63; H, 3.58; N,
14.95. Found: C, 25.51; H, 3.53; N, 14.79%. High resolution ESI+-MS
(MeOH, m/z): 509.079 ([M − Cl]+, calcd 509.077), 567.037 ([M +
Na]+, calcd 567.036), 583.008 ([M + K]+, calcd 583.010), 1111.079
([2 M + Na]+, calcd 1111.083). High resolution ESI−-MS (MeOH,
m/z): 543.031 ([M − H]−, calcd 543.038), 1088.086 ([2 M − H]−,
calcd 1088.093). IR (KBr, selected bonds, cm−1): 3381(m), 3358(m-s)
ν(N−H); 1659(vs), 1637(m-s) ν(CN); 1518(s) ν(NO)as;
10.48 (s, br, 1H, NH), 7.94 (d, 2JHH = 9 Hz, 2H, CH), 7.68 (d, 2JHH
=
9 Hz, 2H, CH), 6.62 (s, br, 1H, NH), 3.35−3.25 (m, 4H, NCH2),
3.17−3.05 (m, 4H, NCH2), 1.60−1.40 (m, 8H, CH2), 1.10−0.95 (m,
4H, CH2).
1
1348(s) ν(NO)s. H NMR (Me2CO-d6, δ): 9.06 (s, br, 1H, NH),
2
2
8.32 (d, JHH = 9 Hz, 2H, CH), 7.84 (d, JHH = 9 Hz, 2H, CH), 6.08
(s, br, 1H, NH), 3.01 (s, 6H, N(CH3)2), 2.70 (s, 6H, N(CH3)2).
7h yield: 52%. TLC (eluent: chloroform/acetone = 2:1, v/v) Rf =
0.67. Anal. Calcd for C18H26N6O2Cl2Pt·11/2H2O: C, 33.19; H, 4.49;
N, 12.90. Found: C, 33.26; H, 4.42; N, 12.79%. High resolution ESI+-
MS (MeOH, m/z): 589.146 ([M − Cl]+, calcd 589.140), 647.106
([M + Na]+, calcd 647.099), 663.076 ([M + K]+, calcd 663.073).
High resolution ESI−-MS (MeOH, m/z): 623.111 ([M − H]−, calcd
623.101). IR (KBr, selected bonds, cm−1): 3375(m), 3192(m-s) ν(N−H);
2939(s), 2856(m-s) ν(C−H); 1655(vs), 1623(m-s) ν(CN);
7e yield: 54%. TLC (eluent: chloroform/acetone = 5:1, v/v) Rf =
0.53. Anal. Calcd for C19H29N5Cl2Pt·H2O: C, 37.32; H, 5.11; N, 11.45.
Found: C, 37.49; H, 5.20; N, 11.45%. High resolution ESI+-MS
(MeOH, m/z): 558.178 ([M − Cl]+, calcd 558.171), 616.132 ([M +
Na]+, calcd 616.129), 1209.278 ([2 M + Na]+, calcd 1209.269). High
resolution ESI−-MS (MeOH, m/z): 592.134 ([M − H]−, calcd
592.132), 1185.279 ([2 M − H]−, calcd 1185.271). IR (KBr, selected
bonds, cm−1): 3364(m), 3269(w-m) ν(N−H); 2932(s), 2854(m-s)
1
1518(s) ν(NO)as; 1346(s) ν(NO)s. H NMR (Me2CO-d6, δ):
2
2
9.03 (s, br, 1H, NH), 8.46 (d, JHH = 9 Hz, 2H, CH), 8.08 (d, JHH
=
9 Hz, 2H, CH), 6.11 (s, br, 1H, NH), 3.40−3.20 (m, 8H, NCH2),
1.70−1.40 (m, 12H, CH2).
v. Preparation of Complexes 9a,b. A solution of MeC(NH2)
NOH (0.1 mmol) in nitromethane (2 mL) was added dropwise to a
vigorously stirred solution of 1 in nitromethane (2 mL) at RT, and the
reaction mixture was then stirred at 60 °C for 3 days. The solvent was
evaporated in vacuo at RT, and a residue obtained was dissolved in
a chloroform−nitromethane (3:1, v/v) mixture (2 mL). The solution was
transferred to a short (l = 5 cm, d = 0.7 cm) column and chromatographed
on silica gel (eluent: chloroform/nitromethane 2:1, v/v). The first fraction
was collected, whereupon the solvent was evaporated in vacuo to give pure
9a (early characterized,4b yield 76%) and 9b (yield 72%).
1
ν(C−H); 1649(vs), 1616(m-s) ν(CN); 1516(m-s) δ(N−H). H
NMR (Me2CO-d6, δ): 9.21 (s, br, 1H, NH), 7.33 (d, 2JHH = 8 Hz, 2H,
CH), 7.26 (d, 2JHH = 8 Hz, 2H, CH), 6.41 (s, br, 1H, NH), 3.45−3.20
(m, 8H, NCH2), 2.39 (s, 3H, ArCH3), 1.65−1.50 (m, 6H, CH2), 1.20−
1.00 (m, 6H, CH2). Crystals suitable for X-ray study were obtained by
slow evaporation of a nitromethane solution in the air at RT.
7f yield: 49%. TLC (eluent: chloroform/acetone = 5:1, v/v) Rf =
0.46. Anal. Calcd for C18H27N5Cl2Pt·H2O: C, 36.19; H, 4.89; N, 11.72.
Found: C, 36.40; H, 4.99; N, 11.66%. High resolution ESI+-MS
(MeOH, m/z): 544.160 ([M − Cl]+, calcd 544.155), 602.117 ([M +
Na]+, calcd 602.113), 618.092 ([M + K]+, calcd 618.087), 1123.287
([2 M − Cl]+, calcd 1123.279), 1181.250 ([2 M + Na]+, calcd
1181.238), 1197.236 ([2 M + K]+, calcd 1197.212). High resolution
ESI−-MS (MeOH, m/z): 578.107 ([M − H]−, calcd 578.116),
1157.224 ([2 M − H]−, calcd 1157.240). IR (KBr, selected bonds,
cm−1): 3366(m), 3279(m) ν(N−H); 2932(s), 2853(m-s) ν(C−H);
1657(vs), 1618(m-s) ν(CN); 1518(m-s) δ(N−H). 1H NMR
(Me2CO-d6, δ): 9.33 (s, br, 1H, NH), 7.46 (m, 5H, Ph), 6.48 (s, br,
1H, NH), 3.45−3.20 (m, 8H, NCH2), 1.65−1.50 (m, 6H, CH2), 1.20−
1.00 (m, 6H, CH2).
9b yield: 72%. Anal. Calcd for C8H16N4Cl2OPt: C, 21.34; H, 3.58;
N, 12.44. Found: C, 21.25; H, 3.51; N, 12.38%. High resolution ESI−-
MS (MeOH, m/z): 449.029 ([M − H]−, calcd 449.022), 485.006
([M + Cl]−, calcd 484.998), 935.038 ([2 M + Cl]−, calcd 935.028). IR
(KBr, selected bonds, cm−1): 3439(m), 3373(s) ν(N−H); 2928(s),
2858(m) ν(C−H); 1645(vs) ν(CN). TLC (eluent: chloroform/
1
acetone = 2:1, v/v) Rf = 0.57. H NMR (Me2CO- d6, δ): 8.47 (s, br,
1H, NH2), 6.99 (s, br, 1H, NH2), 6.58 (s, br, 1H, NH), 3.64−3.56 (m,
4H, NCH2), 2.28 (s, 3H, CH ), 1.66−1.58 (m, 6H, CH2).
3
ASSOCIATED CONTENT
* Supporting Information
■
S
Characteristic ESI+-MS peaks of [6a−h](p-MeC6H4SO3).
Molecular structure of 7b with the atomic numbering scheme.
Thermal ellipsoids are given at the 50% probability level.
Molecular structure of 5b with the atomic numbering scheme.
Thermal ellipsoids are given at the 50% probability level.
Molecular structure of 5g with the atomic numbering scheme.
Thermal ellipsoids are given at the 50% probability level.
Crystal data. Crystallographic information file. This material is
available free of charge via the Internet at http://pubs.acs.org.
7g yield: 53%. TLC (eluent: chloroform/acetone = 3:1, v/v) Rf =
0.57. Anal. Calcd for C19H26N6Cl2Pt·H2O: C, 36.66; H, 4.53; N, 13.50.
J
dx.doi.org/10.1021/ic4000878 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(5) Kopylovich, M. N.; Kukushkin, V. Y.; Haukka, M.; Luzyanin, K.
AUTHOR INFORMATION
■
V.; Pombeiro, A. J. L. J. Am. Chem. Soc. 2004, 126, 15040−15041.
Corresponding Author
*E-mail: bokach@nb17701.spb.edu (N.A.B.); kukushkin@
vk2100.spb.edu (V.Y.K.).
(6) Kopylovich, M. N.; Kukushkin, V. Y.; Haukka, M.; Frausto da
́
Silva, J. J. R.; Pombeiro, A. J. L. Inorg. Chem. 2002, 41, 4798−4804.
(7) (a) Kopylovich, M. N.; Pombeiro, A. J. L.; Fischer, A.; Kloo, L.;
Kukushkin, V. Y. Inorg. Chem. 2003, 42, 7239−7248. (b) Kopylovich,
M. N.; Haukka, M.; Kirillov, A. M.; Kukushkin, V. Y.; Pombeiro, A. J.
L. Chem.Eur. J. 2007, 13, 786−791. (c) Kopylovich, M. N.; Kirillov,
A. M.; Tronova, E. A.; Haukka, M.; Kukushkin, V. Y.; Pombeiro, A. J.
L. Eur. J. Inorg. Chem. 2010, 2425−2432.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(8) Kopylovich, M. N.; Kukushkin, V. Y.; Guedes da Silva, M. F. C.;
The authors express their gratitude to the Russian Fund of
Basic Research (grants 12-03-00076, 12-03-33071, and 11-03-
00262) and Saint Petersburg State University (research grants
of V.Y.K., 2011−2013, and N.A.B., 2013−2015). D.S.B. is
grateful to the Government of Saint Petersburg and The
Potanin Foundation for the scholarships (2011−2012).
Authors acknowledge the RAS Presidium Subprogram 8P
coordinated by N.T. Kuznetsov. NMR studies were performed
at the Centre for Magnetic Resonance (Saint Petersburg State
University).
Haukka, M.; Frausto da Silva, J. J. R.; Pombeiro, A. J. L. J. Chem. Soc.,
́
Perkin Trans. 2001, 1569−1573.
(9) (a) Kritchenkov, A. S.; Bokach, N. A.; Haukka, M.; Kukushkin, V.
Y. Dalton Trans. 2011, 40, 4175−4182. (b) Kritchenkov, A. S.; Bokach,
N. A.; Kuznetsov, M. L.; Dolgushin, F. M.; Tung, T. Q.; Molchanov, A.
P.; Kukushkin, V. Y. Organometallics 2012, 31, 687−699.
(10) (a) Anisimova, T. B.; Bokach, N. A.; Luzyanin, K. V.; Haukka,
M.; Kukushkin, V. Y. Dalton Trans. 2010, 39, 10790−10798.
(b) Gushchin, P. V.; Kuznetsov, M. L.; Haukka, M.; Wang, M.-J.;
Gribanov, A. V.; Kukushkin, V. Y. Inorg. Chem. 2009, 48, 2583−2592.
(11) Glossary of Class Names of Organic Compounds And Reactive
Intermediates Based on Structure. http://www.chem.qmul.ac.uk/
iupac/class/ (accessed May 2013).
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