ISSN 10703284, Russian Journal of Coordination Chemistry, 2013, Vol. 39, No. 3, pp. 234–238. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © O.V. Kovalchukova, A.I. Stash, Dinh Do Nguyen, S.B. Strashnova, V.K. Bel’skii, 2013, published in Koordinatsionnaya Khimiya, 2013, Vol. 39, No. 3,
pp. 136–140.
234
This work was intended to continue our manyyear
investigations of the structures and complexation
reactions of tetraoxopyridines. For instance, ammo
nium 4nitro2,3,5,6tetraoxopyridinate, (NH
4
)
2
⋅
(C
5
HO
6
N
2
)
2
, is a precursor for the synthesis of coordi
nation compounds containing the tetraoxopyridinate
anion. Earlier, we have studied the structure of (NH
4
)
2
⋅
(C
5
HO
6
N
2
)
2
by Xray diffraction [1], obtained the
complexes М(H
2
O)
6
(C
5
HN
2
O
6
)
2
⋅ 2H
2
O (М = Ni
2+
,
Cu
2+
, Co
2+
, and Zn
2+
) in the crystalline state, and
structurally identified the complex
Ni(H
2
O)
6
(C
5
HN
2
O
6
)
2
⋅ 2H
2
O [2]. Unusual solva
tolytic decomposition of the pyridine ring of (NH
4
)
2
⋅
(C
5
HN
2
O
6
)
2
into 2methyl1,3diazolium hydro
bis(oxamate) has been studied in [3]. The crystal
structures of sodium 4nitro2,3,5,6tetraoxopyridi
nate trihydrate and ammonium sodium bis(4nitro
2,3,5,6tetraoxopyridinate) monohydrate have been
examined in [4].
In the present work, we obtained hexaaquacad
mium(II) and hexaaquacobalt(II) 4nitro2,3,5,6
tetraoxopyridinates, [Cd(H
2
O)
6
](C
5
HN
2
O
6
)
2
⋅ 2H
2
O
(I) and [Co(H
2
O)
6
](C
5
HN
2
O
6
)
2
⋅ 2H
2
O (II), and the
product of their cocrystallization,
[Cd
0.32
Co
0.68
(H
2
O)
6
](C
5
HN
2
O
6
)
2
⋅ 2H
2
O (III). In addi
tion, we determined their crystal and molecular struc
tures and studied their properties.
EXPERIMENTAL
Cobalt(II) and cadmium(II) chloride hydrates
(reagent grade) were used; (NH
4
)
2
⋅ (C
5
HO
6
N
2
)
2
was
prepared as described in [5, 6].
Synthesis of metal complexes. An appropriate
metal chloride (5 mmol) was dissolved in ethanol (10–
20 mL) and the resulting solution was brought to boil
ing. Then a hot solution of (NH
4
)
2
⋅ (C
5
HO
6
N
2
)
2
in
acetonitrile was added dropwise. The reaction mixture
was kept on a water bath for 30 min, cooled, and left
for several days until precipitation occurred. The pre
cipitates were filtered off, washed with ethanol, and
dried to constant weights. The yields of the complexes
were 30–45%. Yellowbrown single crystals suitable
for Xray diffraction were obtained by recrystallization
from ethanol.
The contents of the metals were determined by
spectrophotometry. Chemical analyses for nitrogen
For Cd(H
2
O)
6
(C
5
HO
6
N
2
)
2
⋅ 2H
2
O (I) (М = 662.71)
anal. calcd. (%): С, 18.12; N, 8.45; Н, 3.35; Cd, 16.96.
Found (%): С, 17.88; N, 8.72; Н, 3.17; Cd, 17.30.
For Co(H
2
O)
6
(C
5
HO
6
N
2
)
2
⋅ 2H
2
O (II) (M = 609.23)
anal. calcd. (%): C, 19.72; N, 9.20; H, 3.64; Co, 9.67.
Found (%): C, 20.14; N, 9.24; H, 3.01; Co, 9.37.
Hexaaquacobalt(II) and Hexaaquacadmium(II) 4Nitro2,3,5,6
Tetraoxopyridinates [M(H
2
O)
6
](C
5
HN
2
O
6
)
2
· 2H
2
O
(M = Co and Cd): Synthesis, Structures, and Properties
O. V. Kovalchukova
a,
*, A. I. Stash
b
, Dinh Do Nguyen
a
, S. B. Strashnova
a
, and V. K. Bel’skii
b
a
Peoples Friendship University, ul. MiklukhoMaklaya 6, Moscow, Russia
b
Karpov Research Institute of Physical Chemistry, ul. Vorontsovo pole 10, Moscow, Russia
*email: okovalchukova@mail.ru
Received July 12, 2012
Abstract—The complexes [Cd(H
2
O)
6
](C
5
HN
2
O
6
)
2
⋅ 2H
2
O (I) and [Co(H
2
O)
6
](C
5
HN
2
O
6
)
2
⋅ 2H
2
O (II)
were obtained in the crystalline state by reactions of cobalt chloride and cadmium chloride with ammonium
4nitro2,3,5,6tetraoxopyridinate, (NH
4
)
2
⋅ (C
5
HO
6
N
2
)
2
. Their cocrystallization gave the heterometallic
complex [Cd
0.32
Co
0.68
(H
2
O)
6
](C
5
HN
2
O
6
)
2
⋅ 2H
2
O (III). The crystal and molecular structures of
complexes I–III were determined by Xray diffraction. It was demonstrated that the complexation reactions
occur by replacement of two ammonium cations 4nitro2,3,5,6tetraoxopyridinate by the complex cations
[M(H
2
O)
6
]
2+
. The tetraoxopyridinate anions and the complex cations are hydrogenbonded through the
coordinated and crystallization water molecules as well as through the O atoms of the organic anion. The
thermolysis of complexes I and II was examined by TGA.
DOI: 10.1134/S1070328413030044