Synthesis of symmetrical di(pyrimidin-2-yl)-1,2,4-triazoles and di(pyrimidin-2-yl)-1,2,4,5-tetrazines

Article abstract of DOI:10.1007/s11172-010-0317-7

The reactions of pyrimidine-2-carbonitrile and 4,6-dimethylpyrimidine-2- carbonitrile with hydrazine hydrate were investigated. Intermediates in the route of successive transformations of pyrimidine-2-carbonitrile (pyrimidine-2-carbamidrazone and 1,2-bis[amino(pyrimidin-2-yl)methylidene] hydrazine) into trinuclear heterocyclic compounds, viz., symmetrical di(pyrimidin-2-yl)-1,4-dihydro-1,2,4,5-tetrazines and di(pyrimidin-2-yl)-4H-1,2, 4-triazol-4-amines (potential polydentate ligands), were isolated. The oxidative dehydrogenation of di(pyrimidin-2-yl)-1,4-dihydro-1,2,4,5-tetrazines afforded the corresponding 3,6-di(pyrimidin-2-yl)-1,2,4,5-tetrazines.

Full text of DOI:10.1007/s11172-010-0317-7

Russian Chemical Bulletin, International Edition, Vol. 59, No. 9, pp. 1808—1816, September, 2010
1808
Synthesis of symmetrical di(pyrimidinꢀ2ꢀyl)ꢀ1,2,4ꢀtriazoles
and di(pyrimidinꢀ2ꢀyl)ꢀ1,2,4,5ꢀtetrazines
V. P. Krivopalov,a M. B. Bushuev,b,c Yu. V. Gatilov,a and O. P. Shkurkoa
aN. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences,
9 prosp. Akad. Lavrent´eva, 630090 Novosibirsk, Russian Federation.
Fax: +7 (383) 330 9752. Eꢀmail: oshk@nioch.nsc.ru
bA. V. Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences,
3 prosp. Akad. Lavrentieva, 630090 Novosibirsk, Russian Federation.
cNovosibirsk State University,
2 ul. Pirogova, 630090 Novosibirsk, Russian Federation
The reactions of pyrimidineꢀ2ꢀcarbonitrile and 4,6ꢀdimethylpyrimidineꢀ2ꢀcarbonitrile with
hydrazine hydrate were investigated. Intermediates in the route of successive transformations
of pyrimidineꢀ2ꢀcarbonitrile (pyrimidineꢀ2ꢀcarbamidrazone and 1,2ꢀbis[amino(pyrimidinꢀ2ꢀ
yl)methylidene]hydrazine) into trinuclear heterocyclic compounds, viz., symmetrical
di(pyrimidinꢀ2ꢀyl)ꢀ1,4ꢀdihydroꢀ1,2,4,5ꢀtetrazines and di(pyrimidinꢀ2ꢀyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀ
amines (potential polydentate ligands), were isolated. The oxidative dehydrogenation of
di(pyrimidinꢀ2ꢀyl)ꢀ1,4ꢀdihydroꢀ1,2,4,5ꢀtetrazines afforded the corresponding 3,6ꢀdi(pyrimidinꢀ
2ꢀyl)ꢀ1,2,4,5ꢀtetrazines.
Key words: pyrimidineꢀ2ꢀcarbonitrile, 4,6ꢀdimethylpyrimidineꢀ2ꢀcarbonitrile, pyrimidineꢀ
2ꢀcarbamidrazone, 3,6ꢀdi(pyrimidinꢀ2ꢀyl)ꢀ1,4ꢀdihydroꢀ1,2,4,5ꢀtetrazines, 3,6ꢀdi(pyrimidinꢀ2ꢀ
yl)ꢀ1,2,4,5ꢀtetrazines, 3,5ꢀdi(pyrimidinꢀ2ꢀyl)ꢀ1Hꢀ1,2,4ꢀtriazole, 3,5ꢀdi(pyrimidinꢀ2ꢀyl)ꢀ4Hꢀ
1,2,4ꢀtriazolꢀ4ꢀamines.
Substituted 1Hꢀ and 4Hꢀ1,2,4ꢀtriazoles exhibit propꢀ
erties of metal corrosion inhibitors.1 These compounds
are used also as ligands for the synthesis of transition metal
complexes, being coordinated to metal ions through the
N(1),N(2) or N(2),N(4) atoms of the triazole ring to form
oligoꢀ or polynuclear complexes.2 Transition metal comꢀ
plexes with triazoles can exhibit ferroꢀ or antiferromagꢀ
Triazolꢀ4ꢀamines containing other azinyl groups as
substituents in the triazole ring are of great interest in view
of the extension of the range of structurally related ligands.
However, only the synthesis of 3,5ꢀdi(pyrazinꢀ2ꢀyl)ꢀ1,2,4ꢀ
triazolꢀ4ꢀamine (2) was documented.10 Other ligands of
this type are unknown. We synthesized for the first time
two compounds belonging to this class, viz., 3,5ꢀdi(pyꢀ
rimidinꢀ2ꢀyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀamine (3) and 3,5ꢀbisꢀ
(4,6ꢀdimethylpyrimidinꢀ2ꢀyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀamine
(4), which allowed us to begin studies aimed at synthesizꢀ
ing metal complexes with these ligands. Complexes based
on symmetrical dipyrimidinyltriazoles containing meꢀ
sogenic groups in the pyrimidine rings are of particular
interest in view of the design of new multifunctional spinꢀ
transition materials, which simultaneously exhibit liquidꢀ
crystalline properties.
netic exchange interactions.3,4 For the FeII complexes,
1
5
⇔
the spin transition A1 T2 and the thermochromism can
be observed.5—7 4Hꢀ1,2,4ꢀTriazolꢀ4ꢀamines, unlike parꢀ
ent 1Hꢀ1,2,4ꢀtriazole, are usually coordinated to metal
atoms as bidentateꢀbridging ligands through the N(1) and
N(2) atoms of the triazole ring.2 The introduction of
a heterocyclic substituent containing the pyridineꢀtype
nitrogen atom into the triazole ring (Tri) can lead to
a substantial change in the structure of the resulting comꢀ
plex due to the appearance of additional coordination sites.
In addition, the presence of functional groups in the hetꢀ
erocyclic substituent can impart new properties to the comꢀ
plexes or mutually enhance their properties (synergism).
In the last two decades, researchers focussed on the synꢀ
thesis and investigation of transition metal coordination
compounds containing 3,5ꢀbis(2ꢀpyridyl)ꢀ1,2,4ꢀtriazolꢀ4ꢀ
amine (1) as the ligand.8,9
Known 3,5ꢀdiazinylꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀamines were
synthesized according to a standard procedure involving
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1760—1768, September, 2010.
1066ꢀ5285/10/5909ꢀ1808 © 2010 Springer Science+Business Media, Inc.

Pyrimidinylꢀ1,2,4ꢀtriazoles and ꢀ1,2,4,5ꢀtetrazines
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 9, September, 2010
1809
(2ꢀpyridyl)ꢀ1,4ꢀdihydroꢀ1,2,4,5ꢀtetrazine (8), 3,5ꢀbis(2ꢀ
pyridyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀamine (1), or 3,5ꢀbis(2ꢀpyꢀ
ridyl)ꢀ1Hꢀ1,2,4ꢀtriazole (9) as the final products.
In the case of the pyridine, pyrazine, and related derivꢀ
atives, the aboveꢀmentioned transformations can be sigꢀ
nificantly influenced by the specific effects of solvation
and complexation with metal ions. Thus, using pyridineꢀ
2ꢀcarbonitrile as an example, it was shown that the reacꢀ
tions with hydrazine afford dihydrotetrazines 8 as the maꢀ
jor products, whereas the alternative pathway giving triazꢀ
ole 9 requires the presence of metal ions M2+ in the reacꢀ
tion mixture.14,15 To explain this fact, the reactivity of
intermediate pyridineꢀ2ꢀcarbamidrazone (5) was investiꢀ
gated, and the conclusion was made about the favorable
formation of the chelate MII complex for tautomer 5A
(compared to tautomer 5B). The complexation leads to an
increase in the electrophilicity of the C=N bond in the
substrate, thus facilitating the attack on the second carbꢀ
amidrazone molecule. The subsequent elimination of the
hydrazine molecule from the adduct affords 1,2ꢀbisꢀ
(aminomethylidene)hydrazine 6. In the absence of M2+
ions in the reaction mixture, tautomer 5B is the major
species in the medium, and, consequently, adduct 7 can
undergo cyclization accompanied by the elimination of
two ammonia molecules and the formation of dihydrotetrꢀ
azine 8.14,15 The subsequent transformations of bisꢀ
(aminomethylidene)hydrazines into triazoles16,17 and of
R = H (3), Me (4)
the reaction of heteroaromatic carbonitriles with hydrꢀ
azine.10—14 Based on investigations of this reaction for
a series of aromatic substrates, suggestions were made
about the structures of certain intermediates in the route
of successive chemical transformations, and the general
hypothetical scheme was proposed based on the observaꢀ
tions on the influence of the components of the reaction
medium and the reaction conditions on the formation of
particular final products (as an example, Scheme 1 repreꢀ
sents the transformations of pyridineꢀ2ꢀcarbonitrile).10—15
The reaction of carbonitrile with hydrazine starts with the
formation of arylcarbamidrazone 5, which, in turn, accuꢀ
mulates in the reaction medium and begins to regioselecꢀ
tively react with different reaction centers of the starting
compounds and products and, depending on the reaction
conditions and the chemical nature of these compounds,
can give bis(carbamidine) 6 and/or adduct 7. These prodꢀ
ucts can undergo further transformations to form 3,6ꢀbisꢀ
Scheme 1

1810
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 9, September, 2010
Krivopalov et al.
dihydrotetrazines into Nꢀaminotriazoles10—12 have been
studied in detail.
We examined several methods for the synthesis of the
target pyrimidinylꢀsubstituted triazolamines with the aim
of choosing the best procedure. One method was based on
the oneꢀstep approach, which has been developed for the
synthesis of pyridyl derivatives of triazolamine and which
involves the reaction of pyridinecarbonitrile with hydrꢀ
azine dihydrochloride in a solution of hydrazine hydrate.10
In another method, the same reaction was carried out in
two steps. Initially, the reaction of carbonitrile 10 with
hydrazine hydrate performed under mild conditions gave
3,6ꢀdisubstituted 1,4ꢀdihydrotetrazine 11, which was reꢀ
arranged into 3,5ꢀdisubstituted triazolamine 4 without the
isolation and purification (Scheme 2). In the third methꢀ
od, the reaction was divided into two steps with the isolaꢀ
tion of individual dihydrotetrazine 11 followed by its transꢀ
formation into triazolamine 4 by analogy with the proceꢀ
dure described previously.11 A comparison of all three
methods for the synthesis of these compounds did not
reveal advantages of a particular method because the yields
of the target product 4 were equal and were at most 25%.
In the aboveꢀdescribed syntheses, we used 98% hydrazine
hydrate.
In these investigations, different approaches were used
for the synthesis of disubstituted triazolamines, including
those containing the pyrazinyl and pyridyl groups, either
by the twoꢀstep procedure with the isolation (or without
the isolation) of the corresponding dihydrotetrazines,
which can be then rearranged into the target compounds
using homogeneous acid catalysis,11—13 or according to
the oneꢀpot procedure in neutral solvents at higher temꢀ
peratures.10,14
The methods developed previously for the synthesis of
pyridine analogs, which prevent the complexation with
metals, seemed to be the most convenient for the synthesis
of pyrimidinyl derivatives of 1,2,4ꢀtriazolꢀ4ꢀamine and
1,2,4,5ꢀtetrazine. Nevertheless, taking into account the
higher electrophilicity of the cyano group at position 2 of
the pyrimidine ring compared to the cyano derivatives of
pyridine and pyrazine, the possible deviations in the aboveꢀ
mentioned transformation, including those associated with
the transformation of the pyrimidine ring (Pym), cannot
be ruled out. Hence, we initially investigated the behavior
of 4,6ꢀdimethylpyrimidineꢀ2ꢀcarbonitrile (10) in the reꢀ
action with hydrazine hydrate under different conditions,
because the presence of two electronꢀreleasing methyl
groups in the even positions of the pyrimidine ring partialꢀ
ly compensates the electronꢀwithdrawing effect of the secꢀ
ond nitrogen atom. Hence, the reactivity of this substrate
should not be substantially different from that of pyridineꢀ
2ꢀcarbonitrile derivatives.
Unsubstituted pyrimidineꢀ2ꢀcarbonitrile (12) exhibitꢀ
ed the most complex behavior in the reaction with hydrꢀ
azine (see Scheme 2). Depending on the temperature conꢀ
ditions, the order of the mixing of the reagents, and their
ratio, the reaction affords different series of products. Our
observations are consistent with the conclusions drawn in
the study,18 where the experimental conditions of the
synthesis of carbamidrazones in a series of substituted
Scheme 2
Pym is pyrimidinꢀ2ꢀyl (3, 12—18), 4,6ꢀdimethylpyrimidinꢀ2ꢀyl (4, 10, 11, 19).

Pyrimidinylꢀ1,2,4ꢀtriazoles and ꢀ1,2,4,5ꢀtetrazines
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 9, September, 2010
1811
pyridines were varied. Thus, we isolated pyrimidineꢀ2ꢀ
carbamidrazone (13) in good yield in the reaction of carꢀ
bonitrile 12 with a large excess of hydrazine hydrate at
room temperature, as opposed to the results of the study,19
where the condensation was performed in 96% ethanol
and gave this compound in a yield of at most 6%. Such
a low yield is apparently attributed to the high affinity of
amidrazone 13 for water as a result of the formation of
intramolecular hydrogen bonds between water molecules
and the endocyclic nitrogen atoms of the pyrimidine ring
and the NH2 groups of the amidrazone moiety. The latter
fact indicates that the extraction of this compound from
aqueous solutions by organic solvents is inefficient and
could lead to a substantial loss of the product in the experꢀ
iment.19 The characteristic structural feature of amidrꢀ
The 13C NMR spectrum also has a double set of signals for
the C(5), C(4), and C(6) atoms, whose chemical shifts are
exactly equal to the shifts observed for individual comꢀ
pounds 14 and 15 (see the Experimental section). Accordꢀ
ing to the spectroscopic data, both compounds were
present in the mixture in comparable amounts, with comꢀ
pound 14 slightly predominating. Compound 14 is the
precursor giving triazole 15. The similar thermal heteroꢀ
cyclization of aryl analogs of compound 14 has been obꢀ
served previously.17
A sample of individual di(pyrimidinꢀ2ꢀyl)triazole 15
was synthesized by the diazotization of triazolamine 3 in
the presence of oxalic acid. This compound is characterꢀ
ized by a very broad NH signal shifted to 14—15 ppm in
1
the H NMR spectrum (in DMSOꢀd6), which is consisꢀ
1
azone 13 is that its H NMR spectrum shows two closely
spaced broad signals of NH2 groups at δ 5.5—5.6.20
tent with the data for 1,2,4ꢀtriazole24 and its 3,5ꢀdiphenyl
derivative.25 It should be noted that the NH signal of
di(pyrimidinꢀ2ꢀyl)triazole 15, which is present in a mixꢀ
ture with bis(aminomethylidene)hydrazine 14, is substanꢀ
tially broadened (up to 11—14 ppm) and is not observed at
all in the case of the deuterium exchange in the presence
of CD3OD. The substantial broadening of the NH signal
of compound 15 is apparently attributed to the fact that it
exists mainly as the 1H tautomer (this fact was proved for
the majority of 1,2,4ꢀtriazoles in the studies24,26,27) and to
the intramolecular migration of the proton between the
adjacent nitrogen atoms of the strongly solvated triazole
and pyrimidine rings in degenerate structures 15 and 15´
(Scheme 3).
We found that carbamidrazone 13 is the key comꢀ
pound in the chain of further chemical transformations.
The amidrazone molecules have the amphiphilic reactiviꢀ
ty and can either react with the starting carbonitrile to give
1,2ꢀbis(aminomethylidene)hydrazines or undergo dimerꢀ
ization accompanied by the elimination of two ammonia
molecules and the formation of disubstituted dihydrotetrꢀ
azines.10,14—16 Among the known bis(aminomethylidene)ꢀ
hydrazines, the derivative containing the 2ꢀpyridyl group21,22
is most closely related to the compounds under study.
Other heterocyclic derivatives remained unknown until
recent years, and only in the recent past the Xꢀray diffracꢀ
tion data for pyrimidinyl analog 14 prepared as dihydrate
have been published;23 however, details of the synthesis
and complete characteristics of this compound were not
published. We succeeded in isolating compound 14 in 35%
yield. Compound 14 was characterized analytically and
spectroscopically and was studied by powder Xꢀray difꢀ
fraction. The results of the powder Xꢀray diffraction study
are in complete agreement with the singleꢀcrystal Xꢀray
diffraction data.23 In addition, we transformed compound
13 into triazole derivative 15 and dihydrotetrazine derivaꢀ
tive 16 by the thermolysis of a dry sample and using hoꢀ
mogeneous acid catalysis (see Scheme 2).
The transformations of dihydrotetrazines into 4ꢀaminoꢀ
triazoles are generally carried out by refluxing solutions of
dihydrotetrazines in dilute mineral acids. We found that in
the case of the dimethylpyrimidyl derivative of dihydrotetrꢀ
azine 11, triazolamine 4 that is formed under these condiꢀ
tions can be isolated in the rather pure form in moderate
yield. Under these conditions, the corresponding derivaꢀ
tive of dihydrotetrazine 16, which does not contain methꢀ
yl groups, gives di(pyrimidinꢀ2ꢀyl)triazolamine 3 along
with 1,2ꢀdi(pyrimidinꢀ2ꢀyl)hydrazine (17) as the minor
product in 14% yield. Apparently, the formation of the
latter product occurs in the step of the opening of the
protonated dihydrotetrazine ring (Tetr) in accordance with
the proposed mechanism of recyclization.10,11 The repeatꢀ
ed cyclization leading to the formation of a new C—N
bond in the triazole molecule is accompanied by the side
reaction resulting in the addition of water molecules at
two Cꢀelectrophilic centers of the substrate and the elimiꢀ
nation of the hydrazine molecule (see Scheme 2).
We found that the heating of pyrimidinecarbamidraꢀ
zone 13 at temperatures above the melting point leads to
the elimination of ammonia and affords 1,2ꢀdi[aminoꢀ
(pyrimidinꢀ2ꢀyl)methylidene]hydrazine, C10H10N8 (14),
containing an impurity (TLC data and 1H and 13C NMR
spectra). The latter gives a peak at m/z 225 in the mass
spectrum corresponding to the molecular formula
C
10H7N7 for 3,5ꢀdi(pyrimidinꢀ2ꢀyl)ꢀ1Hꢀ1,2,4ꢀtriazole
1,2ꢀDi(pyrimidinꢀ2ꢀyl)hydrazine (17) was identified
in the mixture after chromatography and recrystallization
of the product, which allowed us to increase the percentꢀ
age of this component in the mixture to ~30%. Further
attempts to purify and isolate this compound in the pure
form failed. The structure of this compound was assigned
based on the comparison of the IR, NMR, and mass specꢀ
(15). In addition, the mass spectrum of the mixture has
the most intense peak at m/z 197, relatively intense peaks
at m/z 198 and 171, and a peak at m/z 144 characteristic of
compound 15. The 1H NMR spectrum of the mixture
shows a double set of triplets for the H(5) atom and douꢀ
blets for the H(4) and H(6) atoms of the pyrimidine rings.

1812
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 9, September, 2010
Krivopalov et al.
Scheme 3
tra of the mixture with the spectra of individual diꢀ
(pyrimidinꢀ2ꢀyl)triazolamine 3. The IR spectrum of
the mixture shows two characteristic C=O stretching
bands of the —NH(C=O)—NH(C=O)— moiety at
1678—1710 cm–1. In the 1H NMR spectrum, this moiety
is manifested as a twoꢀproton signal shifted downfield
compared to the NH2 signal of triazolamine 3 (cf. the
published data28,29 for symmetrical dipyridylhydrazines).
The molecular formula C10H8N6O2 determined from the
highꢀresolution mass spectrum is also consistent with the
proposed structure of the byꢀproduct.
1.30 The nonplanar amino groups are linked to the nitroꢀ
gen atoms of the pyrimidine rings by intramolecular
N—H...N hydrogen bonds (H...N, 2.11(2)—2.28(2) Å;
N—H...N, 122(2)—129(1)°). In the crystals, the moleꢀ
cules are linked by C—H...N hydrogen bonds (H...N,
2.40(2)—2.54(2) Å; C—H...N, 165(1)—176(1)°) into
planar layers parallel to the (a—c,b) plane. Among inꢀ
terlayer interactions, let us mention N—H...N hydrogen
bonds (2.55(2) Å, 137°) and πꢀstacking interactions of
the molecules with the centroid—centroid distances of
3.5780(9)—3.9330(9) Å.
The purification of triazolamine 3 from the impurity of
dipyrimidinylhydrazine 17 that is difficult to separate is
a serious problem. Hence, the latter procedure is worse
than the previous method. The best result was obtained
when the recyclization of dihydrotetrazine 16 to triazolꢀ
amine 3 was carried out by heating in THF in the presence
of catalytic amounts of hydrazine dihydrochloride.
The structures of triazolamines 3 and 4 and of dihydroꢀ
tetrazines 11 and 16 were determined based on the NMR
spectroscopic and mass spectrometric data with the use
of the known generalizations for structurally related
compounds.10,12 The singleꢀcrystal Xꢀray diffraction
study of triazolamine 3 (Fig. 1) showed that two crysꢀ
tallographically independent molecules have the same
planar geometry (the rms deviations of the atoms are 0.104
and 0.074 Å), which is similar to that of pyridyl analog
Investigations of the characteristic features of the comꢀ
plexation of the ligands, which we have synthesized, with
transition metal salts are currently underway. In the present
study, we synthesized the first of these compounds, viz.,
the FeII complex with bis(dimethylpyrimidinyl)triazolꢀ
amine 3.
In summary, we carried out successive transformaꢀ
tions of pyrimidineꢀ2ꢀcarbonitrile 12 and its 4,6ꢀdimethꢀ
ylꢀsubstituted derivative 10 into pyrimidinylꢀsubstituted
1,4ꢀdihydroꢀ1,2,4,5ꢀtetrazines 16 and 11 and 1,2,4ꢀtriꢀ
azolꢀ4ꢀamines 3 and 4, respectively. Pyrimidineꢀ2ꢀcarbꢀ
amidrazone 13 and the corresponding 1,2ꢀbis(aminoꢀ
methylidene)hydrazines 14, which are the key intermediꢀ
ates in the route to trinuclear polynitrogen heterocyclic
compounds, were isolated and characterized for the first
time. These compounds are potential polydentate ligands.
Tetrazine derivatives 18 and 19 were synthesized by the
oxidative dehydrogenation of di(pyrimidinꢀ2ꢀyl)dihydroꢀ
tetrazines 11 and 16, respectively.
N(3″)
N(3´)
N(6)
N(4)
C(4″)
C(4´)
C(5´)
C(5)
C(3)
C(5″)
C(6″)
Experimental
C(2″)
C(2´)
N(1″)
C(6´)
N(1)
N(2)
N(1´)
The IR spectra were recorded on a Bruker Vector 22 specꢀ
trophotometer in KBr pellets. The IR spectrum of the FeII comꢀ
plex with triazolamine 3 was measured on a BOMEM MBꢀ102
spectrophotometer in the region of 200—400 cm–1. The UVꢀVis
spectra of solutions of tetrazine dyes in CHCl3 were recorded on
Fig. 1. Molecular structure of 3 with nonhydrogen atoms repreꢀ
sented as displacement ellipsoids drawn at the 50% probability
level (only one crystallographically independent molecule
is shown).

Pyrimidinylꢀ1,2,4ꢀtriazoles and ꢀ1,2,4,5ꢀtetrazines
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 9, September, 2010
1813
a Specord Mꢀ40 spectrophotometer. The mass spectra were obꢀ
tained on a DFS instrument (EI, 70 eV, direct inlet). The 1H and
13C NMR spectra were recorded on Bruker AVꢀ300 and Bruker
AVꢀ400 spectrometers with the use of the signals of the solvents
as the internal standards: DMSOꢀd6, (δ 2.50, δ 39.50) for
compounds 3, 4, 11, and 13—17 and CDCl3 (δH 7.24, δC 76.90)
for compounds 18 and 19. The microanalysis was carried out on
a Carlo Erba analyzer. The water content in the FeII complex
with triazolamine 3 was determined gravimetrically based on the
weight loss after storage of the samples in vacuo. The purity of
the compounds was checked by TLC on Silufol UVꢀ254 plates
with the use of an EtOAc—EtOH—concentrated NH4OH mixꢀ
ture (2 : 2 : 1) as the eluent; the spots were visualized under
UV light.
azine dihydrochloride (2.1 g, 20 mmol), and ethylene glycol
(5 mL). The reaction mixture was heated at 100 °C under argon
for 1.5 h. A 2 M HCl solution (5 mL) was added to the volumꢀ
inous darkꢀorange product, and the resulting redꢀbrown solution
was refluxed for 20 min until the solution became colorless. The
paleꢀyellow solution was brought to рH 9 by adding 2 M NH4OH,
concentrated in vacuo to 5 mL, and extracted with CHCl3.
The extract was concentrated, and the residue was recrystallized
from ethanol. The yield of triazolamine 4 was 1.1 g (25%), m.p.
264.5—266 °C.
C. A solution of dihydrotetrazine 11 (0.75 g, 2.5 mmol) in
2 M HCl (7 mL) was heated under slight reflux in an argon
atmosphere for 0.5 h until the solution became colorless. The
paleꢀyellow solution was concentrated in vacuo to 3 mL, ammoꢀ
nia was added to рH 9, and the solution was again concentrated
and extracted with CHCl3. The extract was concentrated, and
the residue was recrystallized from ethanol. The yield of triꢀ
azolamine 4 was 0.42 g (56%), m.p. 262—266 °C.
H
C
Reaction of 4,6ꢀdimethylpyrimidineꢀ2ꢀcarbonitrile
with hydrazine hydrate
3,6ꢀBis(4,6ꢀdimethylpyrimidinꢀ2ꢀyl)ꢀ1,4ꢀdihydroꢀ1,2,4,5ꢀ
tetrazine (11). A mixture of carbonitrile 10 (2.66 g, 20 mmol)
and hydrazine hydrate (2 mL, 2.1 g, 42 mmol) was heated at
90 °C under argon for 3.5 h and then cooled to room temperaꢀ
ture. Ethanol (5 mL) and water (5 mL) were added to the reacꢀ
tion mixture, and the mixture was kept in a refrigerator. The
orange product was filtered off and successively washed with
water, 50% ethanol (2×0.5 mL), and diethyl ether. The product
was crystallized from ethanol and dried in vacuo. The yield was
1.20 g (42%), m.p. 253—255 °C (EtOH), Rf 0.90. Found (%):
C, 56.87; H, 5.74; N, 37.90. C14H16N8. Calculated (%): C, 56.74;
H, 5.44; N, 37.81. MS, m/z (Irel (%)): 296 [M]+ (63), 134
[C7H8N3]+ (100), 108 [C6H8N2]+ (11), 107 [C7H8N3—HCN]+
(15), 67 (21). Highꢀresolution MS, found: m/z 296.1496 [M]+.
C14H16N8. Calculated: M = 296.1498. IR, ν/cm–1: 3366 (NH),
2919, 2850 (Me), 1594, 1540, 1446, 1344 (Pym). 1H NMR, δ:
2.48 (s, 12 H, 4 Me); 7.37 (s, 2 H, H(5) 2 Pym); 8.89 (s, 2 H,
2 NH). 13C NMR, δ: 23.53 (Me); 120.74 (C(5) Pym); 145.19
(C(3), C(5) Tetr); 155.20 (C(2) Pym); 167.04 (C(4), C(6) Pym).
3,5ꢀBis(4,6ꢀdimethylpyrimidinꢀ2ꢀyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀ
amine (4). A. A mixture of pyrimidinecarbonitrile 10 (1.33 g,
10 mmol), hydrazine hydrate (1.5 mL, 1.6 g, 32 mmol), hydrꢀ
azine dihydrochloride (1.05 g, 10 mmol), and ethylene glycol
(5 mL) was heated at 130—140 °C under argon for 3 h until the
elimination of ammonia ceased. Then the reaction mixture was
cooled to room temperature, and water (20 mL) was added.
After storage for many hours in a refrigerator, the almost colorꢀ
less precipitate that formed was filtered off and washed with
water (2×0.5 mL). The product was recrystallized from ethanol
and dried. The yield was 0.38 g (25%), m.p. 266.5—267.5 °C,
Rf 0.80. Found (%): C, 56.74; H, 5.54; N, 37.74. C14H16N8.
Calculated (%): C, 56.74; H, 5.44; N, 37.81. MS, m/z (Irel (%)):
296 [M]+ (100), 201 (4), 134 [C7H8N3]+ (70), 108 [C6H8N2]+
(32), 107 [C7H8N3—HCN]+ (21), 67 (23). IR, ν/cm–1: 3291
(NH2), 2956, 2920 (Me), 1595, 1558, 1536, 1440 (Pym).
1H NMR, δ: 2.55 (s, 12 H, 4 Me); 7.42 (s, 2 H, H(5) 2 Pym);
7.84 (s, 2 H, NH2). 13C NMR, δ: 23.44 (Me); 120.13 (C(5)
Pym); 148.08 (C(3), C(5) Tri); 154.85 (C(2) Pym); 167.13 (C(4),
C(6) Pym).
Reaction of pyrimidineꢀ2ꢀcarbonitrile
with hydrazine hydrate
Pyrimidineꢀ2ꢀcarbamidrazone (13). A solution of pyrimidineꢀ
2ꢀcarbonitrile (12) (0.42 g, 4 mmol) in THF (1.5 mL) was added
dropwise with stirring to hydrazine hydrate (2 mL, 2.1 g,
42 mmol). The reaction mixture was stirred at room temperature
for 4 h and concentrated in vacuo. The oily viscous residue was
dissolved in anhydrous ethanol (5 mL) and again concentrated
in vacuo. This operation was repeated two times. The residue
was triturated with benzene (5 mL), after which the slow crystalꢀ
lization started. After 10 h, the product was pressed on the filter,
washed with benzene and then with hexane, and dried on the
filter. The yield was 0.52 g (90%), m.p. 98—101 °C (in a capilꢀ
lary) (cf. lit. data19: m.p. 109—110 °C), Rf 0.72. MS, m/z
(Irel (%)): 137 [M]+ (100), 109 [M – N2]+ (51), 108 [M – CHNH2]+
(48), 106 (51), 94 (6), 82 (6), 81 (49), 80 [C4H4N2]+ (43),
79 [C4H3N2]+ (52), 78 (12), 58 (7), 55 (7), 54 (26), 53 (24), 52 (20).
Highꢀresolution MS, found: m/z 137.0698 [M]+. C5H7N5. Calꢀ
culated: M = 137.0701. IR, ν/cm–1: 3434, 3327, 3195 (NH2),
1642 (N—NH2, C=N), 1561, 1449, 1377 (Pym). 1H NMR, δ:
5.55 (br.s, 2 H, =NNH2); 5.65 (br.s, 2 H, =CNH2); 7.39 (t, 1 H,
H(5) Pym, 3J = 4.8 Hz); 8.77 (d, 2 H, H(4), H(6) Pym, 3J = 4.8 Hz).
13C NMR, δ: 120.02 (C(5) Pym); 141.65 (N=C—NH2); 156.99
(C(4), C(6) Pym); 159.14 (C(2) Pym).
1,2ꢀBis[amino(pyrimidinꢀ2ꢀyl)methylidene]hydrazine (14).
A. A mixture of pyrimidinecarbamidrazone 13 (85 mg, 0.6 mmol),
ethyl formate (50 mg, 0.7 mmol), and benzene (2.5 mL) was
refluxed for 3 h. Then the reaction mixture was concentrated
in vacuo, ethanol (1 mL) was added, and the reaction mixture
was brought to reflux and kept in a refrigerator. The precipitate
that formed was filtered off, washed with 50% ethanol, and dried
in vacuo. The product, which was obtained in a yield of 70 mg,
was purified by crystallization from boiling ethanol with the gradꢀ
ual addition of benzene until the solution became turbid. After
storage of the solution in a refrigerator, the yellow product that
precipitated was separated, washed with benzene, and dried
in vacuo. The yield was 31 mg (35%), m.p. 200—205 °C (in
a capillary). After cooling, the melt crystallized and again meltꢀ
ed at 303—305 °C, Rf 0.75. Found (%): C, 42.08; H, 4.87;
N, 38.80. C10H10N8•2.5 H2O. Calculated (%): C, 41.81; H, 5.26;
B. A solution of hydrazine hydrate (3.0 mL, 60 mmol) in
ethylene glycol (10 mL) was added dropwise with stirring to
a mixture of pyrimidinecarbonitrile 10 (4.0 g, 30 mmol), hydrꢀ

1814
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 9, September, 2010
Krivopalov et al.
N, 39.01. MS, m/z (Irel (%)): 242 [M]+ (40), 227 (14), 226 (100),
225 (46), 197 (45), 171 (10), 163 (90), 108 (21), 106 (25), 81 (25),
80 [C4H4N2]+ (35), 79 [C4H3N2]+ (33), 53 (18), 52 (10). Highꢀ
resolution MS, found: m/z 242.1026 [M]+. C10H10N8. Calculatꢀ
ed: M = 242.1028. IR, ν/cm–1: 3431, 3357, 3274 (NH2), 1619
was filtered off, washed with methanol, and dried on the filter.
The product was recrystallized from ethanol in the presence of
DMF and dried in vacuo at 100 °C. The yield of 3,5ꢀdi(pyrimidinꢀ
2ꢀyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀamine (3), which is identical with that
described below, was 0.55 g (7%).
1
(C=N), 1560, 1427, 1372 (Pym). H NMR, δ: 6.63 (br.s, 4 H,
3,5ꢀDi(pyrimidinꢀ2ꢀyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀamine (3). A.
Hydrazine hydrate (1.5 g, 30 mmol) was added dropwise with
stirring to a mixture of pyrimidinecarbonitrile 12 (1.05 g,
10 mmol), hydrazine dihydrochloride (1.05 g, 10 mmol), and
methyl cellosolve (5 mL). The reaction mixture slightly warmed
up, the precipitate gradually dissolved, and the color of the soluꢀ
tion became more intense. The temperature was raised until the
elimination of ammonia started. After 0.5 h, the temperature of
the bath was brought to 115 °C, and the reaction mixture was
kept at this temperature for 6 h. After the completion of the
reaction, the mixture was kept in a refrigerator for 16 h. The
precipitate that formed was pressed on the filter, repeatedly
washed with a minimum amount of anhydrous ethanol, treated
with concentrated NH4OH, and concentrated to dryness. Then
the precipitate was refluxed in ethanol (50 mL) in the presence
of activated carbon. The solution was filtered, and the filtrate
was concentrated in vacuo to 15 mL and kept in a refrigerator.
The crystalline precipitate that formed was filtered off, washed
with anhydrous ethanol, and dried in vacuo at 100 °C. The yield
was 0.87 g (72%), m.p. 257—259 °C (in a capillary); Rf 0.55.
Found (%): C, 49.75; H, 3.37; N, 46.59. C10H8N8. Calculatꢀ
ed (%): C, 50.00; H, 3.36; N, 46.64. MS, m/z (Irel (%)): 240
[M]+ (100), 106 (46), 79 (32), 53 (8). Highꢀresolution MS, found:
m/z 240.0863 [M]+. C10H8N8. Calculated: M = 240.0872. IR,
ν/cm–1: 3326 (NH2), 1566, 1452 и 1421 (Pym). 1H NMR, δ:
7.54 (s, 2 H, NH2); 7.69 (t, 2 H, H(5) 2 Pym, 3J = 4.8 Hz); 9.07
3
2 NH2); 7.59 (t, 2 H, H(5) 2 Pym, J = 4.7 Hz); 8.93 (d, 4 H,
H(4), H(6) 2 Pym, 3J = 4.7 Hz). 13C NMR, δ: 121.62 (C(5)
Pym); 152.48 (C(=N)NH2); 157.74 (C(4), C(6) Pym); 158.86
(C(2) Pym).
B. Pyrimidinecarbamidrazone 13 (140 mg, 1 mmol) was heatꢀ
ed to a temperature above 200 °C until the elimination of ammoꢀ
nia started. Then the reaction mixture was heated in vacuo until
the elimination of ammonia ceased. The residue was treated
with boiling ethanol and filtered. The filtrate was concentrated
to 1 mL, and then benzene (3 mL) and hexane (3 mL) were
added. After storage of the reaction mixture in a refrigerator, the
precipitate was filtered off and dissolved under reflux in CHCl3
(30 mL). The solution was passed through a 2 cm layer of Al2O3,
the eluate was concentrated, and the residue was recrystallized
from a THF—ethanol mixture. The product was obtained in
a yield of 43 mg (35%) as a mixture of 1,2ꢀbis[amino(pyrimidinꢀ
2ꢀyl)methylidene]hydrazine (14) and 3,5ꢀdi(pyrimidinꢀ2ꢀyl)ꢀ
1Hꢀ1,2,4ꢀtriazole (15) in a ratio of 1.5 : 1, m.p. ~200 °C. Upon
cooling, the melt crystallized and melted at 301—303 °C; Rf 0.75
(14) and 0.29 (15). MS, m/z (Irel (%)): 242 [M]+ (34) (14), 226
(100), 225 [M]+ (66) (15), 197 (92), 171 (22) (15), 163 (76), 144
(15) (15), 108 (21), 106 (29), 81 (21), 80 [C4H4N2]+ (39), 79
[C4H3N2]+ (34). 1H NMR, δ: 6.68 (br.s, 4 H, 2 NH2 (14)); 7.60
(t, 2 H, H(5) 2 Pym (14), 3J = 4.7 Hz); 7.62 (t, 2 H, H(5) 2 Pym
(15), 3J = 4.8 Hz); 8.94 (d, 4 H, H(4), H(6) 2 Pym (14), 3J = 4.7 Hz);
9.00 (d, 4 H, H(4), H(6) 2 Pym (15), 3J = 4.8 Hz). 13C NMR, δ:
121.66 (C(5) Pym (14 + 15)); 152.50 (C(=N)NH2 (14)); 157.39
(C(4), C(6) Pym (14) + C(3), C(5) Tri (15)); 157.95 (C(4), C(6)
Pym (15)); 158.86 (C(2) Pym (14 + 15)).
3,6ꢀDi(pyrimidinꢀ2ꢀyl)ꢀ1,4ꢀdihydroꢀ1,2,4,5ꢀtetrazine (16).
Hydrazine hydrate (6 mL, 6.12 g, 122 mmol) was added dropꢀ
wise with stirring to a suspension of pyrimidinecarbonitrile 12
(6.3 g, 60 mmol) in THF (3 mL). The reaction mixture was kept
at room temperature for 20 min and then heated at 90—95 °C for
4.5 h, after which the elimination of ammonia ceased, the mixꢀ
ture hardened, and a voluminous orange precipitate formed. Afꢀ
ter cooling of the reaction mixture, the precipitate was pressed
on the filter, washed with 50% methanol (1 mL) and then twice
with methanol (2×0.5 mL), and dried first on the filter and then
at 100 °C in vacuo over P2O5. The yield was 3.95 g (55%), m.p.
215—218 °C (EtOH), Rf 0.68. Found (%): C, 48.82; H, 3.41;
N, 45.41. C10H8N8•0.5 H2O. Calculated (%): C, 48.19; H, 3.64;
N, 44.96. MS, m/z (Irel (%)): 240 [M]+ (98), 106 (100),
80 [C4H4N2]+ (27), 79 [C4H3N2]+ (60), 53 (39), 52 (17). Highꢀ
resolution MS, found: m/z 240.0863 [M]+. C10H8N8. Calculatꢀ
ed: M = 240.0872. IR, ν/cm–1: 3471 and 3326 (NH), 1632
(C=N), 1567, 1452, 1421, 1354 (Pym). 1H NMR, δ: 7.62 (t, 2 H,
H(5) 2 Pym, 3J = 4.8 Hz); 8.93 (d, 4 H, H(4), H(6) 2 Pym,
3J = 4.8 Hz); 9.05 (s, 2 H, 2 NH Tetr). 13C NMR, δ: 122.20
(C(5) Pym); 145.15 (C(3), C(6) Tetr); 155.82 (C(2) Pym); 157.74
(C(4), C(6) Pym).
3
(d, 4 H, H(4), H(6) 2 Pym, J = 4.8 Hz). 13C NMR, δ: 121.72
(C(5) Pym); 149.00 (C(3), C(5) Tri); 155.50 (C(2) Pym); 157.94
(C(4), C(6) Pym).
B. A suspension of 3,6ꢀdi(pyrimidinꢀ2ꢀyl)ꢀ1,4ꢀdihydrotetrꢀ
azine 16 (0.69 g, 2.5 mmol) in 2 M HCl (6 mL) was carefully
heated with stirring and a gradual rise of the temperature. After
the dissolution of the precipitate, the temperature was raised to
reflux. After ~30 min, the reaction solution, whose color changed
from darkꢀred to strawꢀyellow, was concentrated in vacuo, the
residue was treated with concentrated NH4OH, and the mixture
was again concentrated. The product was extracted with boiling
ethanol. The extract was concentrated to 3 mL and kept in
a refrigerator. After the separation of the precipitate, the filtrate
was concentrated to one half of the initial volume, and an addiꢀ
tional amount of the product was obtained. The total yield was
0.43 g (69%), m.p. 235—245 °C. According to the spectroscopic
data, the product consisted of 3,5ꢀdi(pyrimidinꢀ2ꢀyl)ꢀ4Hꢀ1,2,4ꢀ
triazolꢀ4ꢀamine (3) and 1,2ꢀdi(pyrimidinꢀ2ꢀyl)hydrazine (17) in
a ratio of ~4 : 1 and other minor compounds.
To purify the mixture from the minor compounds, 0.30 g of
the mixture was refluxed with ethyl acetate. The resulting soluꢀ
tion was passed through a 3ꢀcm layer of silica gel. After the
column chromatography, the major fraction was gradually conꢀ
centrated until the crystallization started. After the formation of
a precipitate of triazolamine 3 (0.06 g), the mother liquor was
carefully decanted and kept at room temperature and then in
a refrigerator. The white fineꢀcrystalline precipitate that slowly
formed was filtered off, washed with ethyl acetate, and dried
in vacuo. A mixture (0.14 g) of triazolamine 3 and di(pyrimꢀ
idinecarbonyl)hydrazine 17 in the 3/17 ratio of ~2 : 1 was obꢀ
The filtrates were combined, the product was extracted with
CHCl3, the extract was concentrated in vacuo, the residue was
triturated with methanol (2 mL), and the mixture was kept in
a refrigerator overnight. The strawꢀyellow precipitate that formed

Pyrimidinylꢀ1,2,4ꢀtriazoles and ꢀ1,2,4,5ꢀtetrazines
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 9, September, 2010
1815
tained, m.p. 275—278 °C. MS, m/z (Irel (%)): 244 [M]+ (37) (17),
240 [M]+ (78) (3), 165 (10), 109 (15) (17), 107 (33) (17), 106
(34) (3), 81 (31), 80 (52), 79 [C4H3N2]+ (100), 53 (44), 52 (18).
Highꢀresolution MS, found: m/z 244.0698 [M]+, C10H8N6O2
and 240.0877 [M]+, C10H8N8. Calculated: M = 244.0708 (17)
and M = 240.0872 (3). IR of the mixture, ν/cm–1: 3405, 3316,
and 3139 (NH, NH2), 1710 and 1678 (C=O), 1565, 1424, and
precipitate was filtered off, washed with ethanol, and dried
in vacuo at 100 °C. The yield was 0.12 g (70% ), m.p. 245—248 °C.
Found (%): C, 57.03; H, 4.92; N, 38.32. C14H14N8. Calculated (%):
C, 57.13; H, 4.79; N, 38.07. MS, m/z (Irel (%)): 294 [M]+ (17),
134 (56), 133 [C7H8N3—H]+ (100), 132 (26), 107 (9), 106
[C7H8N3—HCN]+ (24), 105 (9), 80 (13), 67 (16), 66 (22), 65
(12). UVꢀVis, λmax/nm (logε): 267 (4.32), 535 (2.79). IR, ν/cm–1
:
1
1386 (Pym). H NMR, δ: 7.54 (s, 2 H, NH2, (3)); 7.69 (t, 2 H,
2997, 2925, 1595, 1532, 1431, 1389, 1347. 1H NMR (CDCl3), δ:
2.69 (s, 12 H, 4 Me); 7.28 (s, 2 H, H(5) 2 Pym). 13C NMR, δ:
24.11 (Me); 121.58 (C(5) Pym); 158.91 (C(2) Pym); 163.88
(C(3), C(5) Tetr); 168.35 (C(4), C(6) Pym).
H(5) 2 Pym, 3, 3J = 4.9 Hz); 7.75 (t, 2 H, H(5) 2 Pym, 17,
3J = 4.9 Hz); 9.02 (d, 4 H, H(4), H(6) 2 Pym, 17, 3J = 4.9 Hz);
9.07 (d, 4 H, H(4), H(6) 2 Pym, 3, 3J = 4.9 Hz); 10.87 (br.s, 2 H,
NH—NH, 17). 13C NMR, δ: 121.69 (C(5) Pym, 3); 123.46 (C(5)
Pym, 17; 148.98 (C(3), C(5) Tri, 3); 155.48 (C(2) Pym, (3));
157.37 (C(2) Pym, 17); 157.82 (C(4), C(6) Pym, 17); 157.86
(C(4), C(6) Pym, 3); 161.44 (C=O, 17).
Dithiocyanatobis[3,5ꢀdi(pyrimidinꢀ2ꢀyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀ
amine]iron monohydrate, [FeL2(NCS)2]•H2O. A solution of
KNCS (21 mg, 0.22 mmol) in MeOH (1 mL) was added to
a solution of Fe(ClO4)2•H2O (32 mg, 0.09 mmol) in MeOH
(1 mL) containing an additive of ascorbic acid under argon. The
precipitate that formed was filtered off, and the filtrate was addꢀ
ed to a solution of triazolamine 3 (43 mg, 0.18 mmol) in MeOH
(13 mL). After 15 min, the brightꢀred precipitate that formed
was separated, washed with MeOH, and dried in air. The yield
was 46.2 mg (77%). IR, ν/cm–1: 3600—3400 (OH, NH), 2067
(NCS–), 1580 sh, 1559, 1491 (Pym, Tri), 476 (NCS–), 253
(Fe—N). Found (%): C, 39.51; H, 2.65; N, 36.48; Fe, 8.13;
S, 9.96; H2O, 3.0. C22H16FeN18S2•H2O. Calculated (%):
C, 39.41; H, 2.71; N, 37.60; Fe, 8.33; S, 9.56; H2O, 2.7.
Xꢀray diffraction study of a crystalline sample of 3,5ꢀdiꢀ
(pyrimidinꢀ2ꢀyl)ꢀ4Hꢀ1,2,4ꢀtriazolꢀ4ꢀamine (3). A suspension of
the complex [FeL2(NCS)2]•H2O (0.1 g) in MeCN (3 mL) in the
presence of several drops of DMF was prepared. The slow evapoꢀ
ration of the solvent for two months led to the formation of large
wellꢀfaceted single crystals of ligand 3 over the layer of the fineꢀ
crystalline complex.
3,5ꢀDi(pyrimidinꢀ2ꢀyl)ꢀ1Hꢀ1,2,4ꢀtriazole (15). A solution of
NaNO2 (0.14 g, 2 mmol) in water (0.3 mL) was added dropwise
with stirring to a solution of triazolamine 3 (0.12 g, 0.5 mmol) in
a mixture of oxalic acid (0.27 g, 3 mmol), acetic acid (0.6 mL),
and water (0.6 mL). The reaction mixture was stirred for 0.5 h,
after which the precipitate that formed was filtered off and washed
with water. Then 2 M NH4OH was added to the precipitate, and
the mixture was extracted with chloroform. The extract was conꢀ
centrated, and the residue was crystallized from anhydrous ethaꢀ
nol. After storage in a refrigerator for 3 days, the colorless fineꢀ
crystalline precipitate was filtered off and dried in vacuo at 100 °C.
The yield was 0.04 g (35%), m.p. 299—302 °C; Rf 0.27.
Found (%): C, 52.86; H, 3.22; N, 43.77. C10H7N7. Calculatꢀ
ed (%): C, 53.33; H, 3.13; N, 43.54. MS, m/z (Irel (%)): 225
[M]+ (90), 197 (100), 196 (33), 171 (32), 144 (18), 106 (15), 79
(21), 65 (13). Highꢀresolution MS, found: m/z 225.0760 [M]+.
C10H7N7. Calculated: M = 225.0763. IR, ν/cm–1: 3432 (NH),
1567, 1509, 1451, 1429, 1410, 1391 и 1376 (Pym). 1H NMR, δ:
7.62 (t, 2 H, H(5) 2 Pym, 3J = 4.9 Hz); 9.00 (d, 4 H, H(4), H(6)
2 Pym, 3J = 4.9 Hz); 14.90 (br.s, 1 H, NH). 13C NMR, δ: 121.60
(C(5) Pym); 156.69 (C(3), C(5) Tri); 157.97 (C(4), C(6) Pym);
158.37 (C(2) Pym).
3,6ꢀDi(pyrimidinꢀ2ꢀyl)ꢀ1,2,4,5ꢀtetrazine (18). A solution of
NaNO2 (0.11 g, 1.6 mmol) in water (0.3 mL) was added dropꢀ
wise with stirring to a cold solution of the substrate, which was
prepared by the dissolution of dihydrotetrazine 16 (0.12 g,
0.5 mmol) in acetic acid (2 mL) at 30 °C. The solution immeꢀ
diately turned carmineꢀviolet. After 0.5 h, the precipitate that
formed was filtered off, washed with water and ethanol, and
dried on the filter. The yield of tetrazine 18* was 0.04 g (33%),
m.p. 274—277 °C. MS, m/z (Irel (%)): 238 [M]+ (5), 105 (100),
78 (25), 53 (8), 52 (7). Highꢀresolution MS, found: m/z 238.0714
[M]+. C10H6N8. Calculated: M = 238.0715. UVꢀVis, λmax/nm
(logε): 260 (4.38), 535 (2.80). IR, ν/cm–1: 3075, 2988, 2920,
1568, 1375, 1168. 1H NMR (CDCl3), δ: 7.61 (t, 2 H, H(5) 2 Pym,
3J = 4.8 Hz); 9.16 (d, 4 H, H(4), H(6) 2 Pym, 3J = 4.8 Hz).
13C NMR, δ: 122.61 (C(5) Pym); 158.42 (C(4), C(6) Pym);
159.21 (C(2) Pym); 163.58 (C(3), C(5) Tetr).
The Xꢀray diffraction data were collected on a Bruker APEX
II CCD diffractometer (graphite monochromator, λ(MoꢀKα) =
= 0.71073 Å, 296 K, φ,ωꢀscanning technique). Colorless crystals
belong to the monoclinic system, C10H8N8, M = 240.24, space
group P21/c, a = 7.8317(4) Å, b = 18.4894(8) Å, c = 14.5157(7) Å,
β = 94.936(2)°, V = 2094.13(17) Å3, Z = 8, dcalc =1.524 g cm–3
,
μ = 0.106 mm–1. The intensities of 30083 reflections were meaꢀ
sured (2θ < 54°) from a crystal with dimensions 0.25×0.28×0.30 mm,
of which 4543 reflections were independent (Rint = 0.0459);
3569 reflections with I ≥ 2σ(I) were obtained, 389 parameters
were refined, R1 = 0.0411 (based on reflections with I ≥ 2σ(I)),
wR2 = 0.1267, and GOOF = 1.029 (based on all reflections).
The absorption correction was applied with the use of the
SADABS program32 (Tmin/Tmax = 0.89/0.96). The structure was
solved by direct methods. The positions and thermal parameters
of nonhydrogen atoms were refined first isotropically and then
anisotropically by the fullꢀmatrix leastꢀsquares method. The
hydrogen atoms were refined isotropically. All calculations were
performed with the use of the SHELXTL program package.33
The atomic coordinates and the thermal parameters were deꢀ
posited with the Cambridge Crystallographic Data Centre
(CCDC 754771).
3,6ꢀBis(4,6ꢀdimethylpyrimidinꢀ2ꢀyl)ꢀ1,2,4,5ꢀtetrazine (19).
A solution of NaNO2 (0.60 g, 10 mmol) in water (2 mL) was
added dropwise with stirring to a cold solution of dihydrotetrꢀ
azine 11 (0.60 g, 2 mmol) in acetic acid (6 mL). The reaction
solution immediately turned violet, and the darkꢀviolet fineꢀ
crystalline precipitate formed soon afterwards. After 0.5 h, the
References
1. B. Mernari, H. El Attari, M. Traisnel, F. Bentiss, M. Lagꢀ
renee, Corrosion Sci., 1998, 40, 391.
2. J. G. Haasnoot, Coord. Chem. Rev., 2000, 200—202, 131.
* In the study,31 the m.p. for compound 18 was not reported.

1816
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 9, September, 2010
Krivopalov et al.
3. M. Inoue, M. Kubo, Coord. Chem. Rev., 1976, 21, 1.
4. U. Beckmann, S. Brooker, Coord. Chem. Rev., 2003, 245, 17.
5. L. G. Lavrenova, S. V. Larionov, Koord. Khim., 1998, 24,
403 [Russ. J. Coord. Chem. (Engl. Transl.), 1998, 24, 379].
6. P. J. van Koningsbruggen, in Spin Crossover in Transition
Metal Compounds, Topics in Curr. Chem., 233, Eds P. Gutꢀ
lich, H. A. Goodwin, SpringerꢀVerlag, Berlin, 2004, p. 123.
7. S. V. Larionov, Koord. Khim., 2008, 34, 243 [Russ. J. Coord.
Chem. (Engl. Transl.), 2008, 34, 237].
20. US Pat. 0075375 (2005); http://v3.espacenet.com.
21. F. H. Case, J. Heterocycl. Chem., 1970, 7, 1001.
22. Z. Xu, L. K. Thompson, D. O. Miller, Inorg. Chem., 1997,
36, 3985.
23. S. Shi, T.ꢀM. Yao, X.ꢀT. Geng, L. Chen, L.ꢀN. Ji, Acta
Crystallogr., Sect. E, 2008, 64, o272.
24. L. T. Creagh, P. Truitt, J. Org. Chem., 1968, 33, 2956.
25. J. C. Lewis, J. Y. Wu, R. G. Bergman, J. A. Ellman, Angew.
Chem., Int. Ed., 2006, 45, 1589.
8. M. H. Klingele, S. Brooker, Coord. Chem. Rev., 2003,
241, 119.
26. R. M. Claramunt, D. Sanz, C. Lopez, J. A. Jimenez, Magn.
Reson. Chem., 1997, 35, 35.
9. J. A. Kitchen, S. Brooker, Coord. Chem. Rev., 2008,
252, 2072.
10. F. Bentiss, M. Lagrenee, M. Traisnel, B. Mernari, H. Elatꢀ
tari, J. Heterocycl. Chem., 1999, 36, 149.
11. J. F. Geldard, F. Lions, J. Org. Chem., 1965, 30, 318.
12. R. A. Bowie, M. D. Gardner, D. G. Neilson, K. M. Watson,
S. Mahmood, V. Ridd, J. Chem. Soc., Perkin Trans. 1,
1972, 2395.
13. M. H. Klingele, P. D. W. Boyd, B. Moubaraki, K. S. Murꢀ
ray, S. Brooker, Eur. J. Inorg. Chem., 2006, 573.
14. L. Cheng, W.ꢀX. Zhang, B.ꢀH. Ye, J.ꢀB. Lin, X.ꢀM. Chen,
Inorg. Chem., 2007, 46, 1135.
15. X.ꢀM. Chen, M.ꢀL. Tong, Acc. Chem. Res., 2007, 40, 162.
16. D. D. Libman, R. Slack, J. Chem. Soc., 1956, 2253.
17. I. Ya. Postovskii, N. N. Vereshchagina, Zh. Obshch. Khim.,
1959, 29, 2139 [J. Gen. Chem. USSR (Engl. Transl.), 1959, 29].
18. US Pat. 6504032 (2003); http://v3.espacenet.com.
19. F. H. Case, J. Org. Chem., 1965, 30, 931.
27. B. I. Buzykin, E. V. Mironova, V. N. Nabiullin, A. T. Gubaidꢀ
ullin, I. A. Litvinov, Zh. Obshch. Khim., 2006, 76, 1534 [Russ.
J. Gen. Chem. (Engl. Transl.), 2006, 76, 1471].
28. E. Dyer, T. J. Nycz, M. B. Long, J. Heterocycl. Chem., 1972,
9, 1267.
29. P. V. Bernhardt, P. Chin, D. R. Richardson, J. Biol. Inorg.
Chem., 2001, 6, 801.
30. M. R. Silva, J. A. Silva, N. D. Martins, A. M. Beja, A. J. F.
N. Sobral, Acta Crystallogr., Sect. E, 2008, 64, o1762.
31. W. Kaim, J. Fees, Z. Naturforsch., 1995, 50b, 123.
32. G. M. Sheldrick, SADABS, Program for Empirical Xꢀray
Absorption Correlation, Bruker—Nonius, 1990—2004.
33. G. M. Sheldrick, SHELXTL v.6.12, Structure Determination
Software Suite, Bruker AXL, Madison (USA), 2000.
Received December 3, 2009;
in revised form July 16, 2010