Pivalates with the MII 4O4 cubane core (M = Co, Ni): Synthesis, structure, magnetic properties, and solid-state thermolysis

Article abstract of DOI:10.1007/s11172-009-0002-x

Methods were developed for the controlled thermal synthesis of high-spin cubane-like pivalates {M^II ₄(μ₃-OR) ₄} (M = Co or Ni; R = H or Me) starting from mono-and polynuclear complexes. The solid-state thermal d

Full text of DOI:10.1007/s11172-009-0002-x

Russian Chemical Bulletin, International Edition, Vol. 58, No. 1, pp. 11—20, January, 2009
11
Pivalates with the {MII O4} cubane core (M = Co, Ni):
4
synthesis, structure, magnetic properties, and solidꢀstate thermolysis*
I. G. Fomina,a Zh. V. Dobrokhotova,a G. G. Aleksandrov,a O. Yu. Proshenkina,a
M. L. Kovba,b A. S. Bogomyakov,c V. N. Ikorskii,c† V. M. Novotortsev,a and I. L. Eremenkoa
aN. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
31 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax +7 (495) 954 1279. Eꢀmail: fomina@igic.ras.ru
bDepartment of Chemistry, M. V. Lomonosov Moscow State University,
1 Leninskie Gory, 119992 Moscow, Russian Federation.
Eꢀmail: mich@td.chem.msu.ru
cInternational Tomography Center, Siberian Branch of the Russian Academy of Sciences,
3a ul. Institutskaya, 630090 Novosibirsk, Russian Federation.
Fax: +7 (383 2) 33 1399. Eꢀmail: bus@tomo.nsc.ru
Methods were developed for the controlled thermal synthesis of highꢀspin cubaneꢀlike
pivalates {MII (µ ꢀOR)4} (M = Co or Ni; R = H or Me) starting from monoꢀ and polynuclear
3
4
complexes. The solidꢀstate thermal decomposition of the known pivalate clusters [MI4I(µ ꢀOMe)4ꢀ
3
2
1
(µ ꢀOOCBut)2(η ꢀOOCBut)2(MeOH)4] and the new clusters [MI4I(µ ꢀOH)4(η ꢀOOCBut)3ꢀ
(µꢀ(NH2)2C6H2Me2)3(η ꢀ(NH2)2C6H2Me2)3]+(OOCBut)– (M = Co 3or Ni) was studied by
2
1
differential scanning calorimetry and thermogravimetry. The thermolysis of cubaneꢀlike CoII
and NiII pivalates is a destructive process. The phase composition of the decomposition products
is determined by the nature of coordinated ligands and the structural features of the metal core.
Key words: cobalt, nickel, cubaneꢀlike cobalt and nickel pivalate complexes, 4,5ꢀdimethylꢀ
1,2ꢀphenylenediamine, solidꢀstate thermolysis, Xꢀray diffraction study, magnetic properties.
Among polynuclear transitionꢀmetal carboxylates,
compounds containing 3d metals, including highꢀspin
cobalt(II) and nickel(II) derivatives, are well known to
have cubaneꢀlike structures with the {M4O4} core.1—14,**
The magnetic behavior of symmetrical cubaneꢀlike CoIIꢀ
and NiIIꢀcontaining pivalates is very unusual and depends
on the electronic state of the metal center or the characꢀ
teristic features of the bridging ligands that partially
replace carboxylate groups.5,11,12 It would be expected that
the use of these two factors will facilitate the assembly of
new types of magnetoactive cubanes, the results of these
chemical transformations of the metal core or the ligand
periphery being difficult to predict. These investigations
are, apparently, helpful for the development of techniques
for the molecular assembly of new molecular magnets as
potential components of molecular electronics devices,
because certain cubanes containing CoII or NiII atoms
were found to exhibit ferromagnetic properties.15—19 It
should be noted that, in this case, the chemical assembly
of the target systems having particular magnetic characꢀ
teristics is a key step in the design of such molecular
magnetic materials. The control over the composition
and fragments of the molecular structures of complexes is
an important tool for the directed chemical influence on
the magnetic behavior of compounds.
In the present study, we examined the possibility of
synthesizing new unsymmetrical cubaneꢀlike CoII and NiII
pivalate complexes and investigated their magnetic propꢀ
erties. In addition, we considered ''mild thermolysis'' of
known and the newly synthesized cubaneꢀlike molecules,
which can be used as molecular precursors for the preparaꢀ
tion of oxide materials with different compositions.8,20—24
Results and Discussion
* Dedicated to Academician A. I. Konovalov on his 75th birthꢀ
day.
† Deceased.
** F. H. Allen, Acta Crystallogr., Sect. B, 2002, 58, 308, HAJCAX,
HAJCIF, HAJFAA, RAPXIQ.
The use of alkanecarboxylate anions holds promise for
the chemical assembly of various polynuclear structures
containing transitionꢀmetal atoms. On the one hand, this
is associated with high solubility of new compounds in
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 11—20, January, 2009.
1066ꢀ5285/09/5801ꢀ0011 © 2009 Springer Science+Business Media, Inc.

12
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Fomina et al.
Scheme 1
M = Co, n = ∞ (1); M = Ni, n = 6 (2); M = Co (3), Ni (4)
organic solvents, which allows the preparation of comꢀ
pounds as crystals suitable for different physicochemical
studies, including Xꢀray diffraction. On the other hand,
this is important for the solution of particular technologiꢀ
cal problems in manufacturing processes, for example, to
prevent uncontrolled hydrolysis. We used pivalate anions,
which generally form polynuclear complexes readily
soluble even in hydrocarbons due to the presence of the
bulky tertꢀbutyl group in the carboxylate anion. In addiꢀ
tion, tertꢀbutyl groups serve the shielding function in crysꢀ
tals, thus preventing the formation of 3D polymers, and
substantially reduce the contributions of intermolecular
spinꢀspin interactions between the magnetic centers in
the molecules.
Synthesis of cobalt(II) and nickel(II) pivalates with the
{M4O4} cubaneꢀlike core. Earlier,5,11,12 the isostructural
dinuclear complexes M2(µꢀH2O)(µꢀOOCBut)2(OOCBut)2ꢀ
(HOOCBut)4 (M = Co or Ni) have been used as the
starting reagents for the synthesis of symmetrical cubaneꢀ
like CoII and NiII pivalates. We found that the polynuclear
pivalates [M(OOCBut)2]n (M = Co (1) and Ni (2)) can
also be used for this purpose. The synthesis of the latter
compounds presents no serious problems.25 In spite of the
different structures of the starting reagents 1 and 2 (1 is a
1D polymer, whereas 2 has the sixꢀmembered cyclic strucꢀ
ture Ni6(µ2ꢀOOCBut)6(µ3ꢀOOCBut)6),25 their reactions
with 4,5ꢀdimethylꢀ1,2ꢀphenylenediamine (L) in the ratio
Mat : L = 1 : 2 in deaerated ethanol (the water content is
lower than 5%) at 60 °C under argon afford the isostrucꢀ
tural ionic complexes [M4(µ3ꢀOH)4(η1ꢀOOCBut)3ꢀ
(µꢀ(NH2)2C6H2Me2)3(η1ꢀ(NH2)2C6H2Me2)3]+(OOCBut)–
(M = CoII (3) and NiII (4)), which crystallize as solvꢀ
ates with ethanol and water (3•4EtOH•1.5H2O and
4•4EtOH•1.5H2O, respectively) (Scheme 1).
According to Xꢀray diffraction data, the complex catꢀ
ion in cluster 3 has the {CoII O4} cubaneꢀlike core formed
4
by four cobalt atoms and four oxygen atoms of the tridenꢀ
tate bridging hydroxo groups (Co—O, 2.058(3)—2.110(3)
Å; the O—Co—O angle, 80.66(13)—83.02(13)°) (Fig. 1).
The cobalt atoms are at a nonbonding distance (Co...Co,
3.166(1)—3.170(1) Å). An important difference of 3 from
most of known carboxylate cubanes1,2,4,6,10—14,* is that
the cation in compound 3 is unsymmetrical. The ligand
environment of the three cobalt atoms (Co(1), Co(2),
and Co(3)) is equivalent and, in addition to bonds
with the µ3ꢀOꢀbridging atom, includes the monodentate
pivalate anion (Co—O, 2.066(3)—2.114(3) Å) and two
nitrogen atoms (Co—N, 2.185(4)—2.242(4) Å) of two
bridging diamine ligands, through which the cobalt atoms
are linked in pairs (Co(1) and Co(2), Co(2) and Co(3),
Co(1) and Co(3)). The ligand environment of the Co(4)
atom is sharply different and consists of three µ3ꢀO atoms
and three N atoms (Co—N, 2.174(4)—2.187(4) Å) of the
* F. H. Allen, Acta Crystallogr., Sect. B, 2002, 58, 308, HAJFAA,
RAPXIQ.

{MI4IO4} (M = Co, Ni) pivalates with cubane core
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
13
nuclear complex Co(η2ꢀ(NH2)2C6H2Me2)(η1ꢀ(NH2)2ꢀ
C6H2Me2)2(OOCBut)2 (5)26 or the newly synthesized
complex Ni(η2ꢀ(NH2)2C6H2Me2)(η1ꢀ(NH2)2C6H2Me2)2ꢀ
(OOCBut)2 (6), which is the crystallographically isostrucꢀ
tural analog of the other known compound Fe(η2ꢀ(NH2)2ꢀ
C6H2Me2)(η1ꢀ(NH2)2C6H2Me2)2(OOCBut)2.27 The storage
of dilute ethanolic solutions of complexes 5 and 6 results
in crystallization of compounds 3 and 4, respectively.
Undoubtedly, water that is present in ethanol (used as
the solvent) plays a great role in the formation of the
{M4(µ3ꢀOH)4} cubaneꢀlike core; however, the influence
of hydrocarbon substituents in ROH, apparently, cannot
be excluded as well.
The study of the reaction of compound 2 with 4,5ꢀdiꢀ
methylꢀ1,2ꢀphenylenediamine (L) in methanol (the
water content is lower than 3%) instead of ethanol showed
that, in concentrated solutions, the first step also affords
mononuclear complex 6, whose recrystallization from a
dilute methanolic solution gives rise to the neutral cubane
N(6)
N(5)
N(1)
Co(4)
N(3)
N(4)
N(2)
O(4M)
O(2M
)
O(3M)
O(4)
Co(1)
Co(3)
N(9)
O(3)
Co(2)
O(1M)
N(10)
N(10)
N(11
)
Fig. 1. Structure of the cluster cation [Co4(µ ꢀOH)4(η ꢀOOCBut)3ꢀ
1
3
(µꢀ(NH2)2C6H2Me2)3(η ꢀ(NH2)2C6H2Me2)3]+ (3).
1
cluster
NiII (µ3ꢀOMe)4(η1ꢀOOCBut)(η2ꢀOOCBut)ꢀ
4
(µ2ꢀOOCBut)2(η2ꢀ(NH2)2C6H2Me2)2(MeOH) (7) as a solꢀ
vate with pivalic acid and methanol (7•HOOCBut•MeOH)
(Scheme 2).
three monodentate diamine ligands. As a result, the
cation contains three octahedral CoN2O4 fragments and
one CoN3O3 fragment. The Xꢀray diffraction study (see
the Experimental section) showed that the analogous
nickel complex 4•4EtOH•1.5H2O is isostructural with
the cobalt compound 3•4EtOH•1.5H2O.
The cations [M4(µ3ꢀOH)4(η1ꢀOOCBut)3(µꢀ(NH2)2ꢀ
C6H2Me2)3(η1ꢀ(NH2)2C6H2Me2)3]+ can formally be conꢀ
sidered as the interaction products of the mononuclear
fragment L3M (M = Co or Ni; L = 1,2ꢀ(NH2)2C6H2Me2)
with the M3(µ3ꢀOH)(µ2ꢀOH)3 triangles. Actually, comꢀ
pounds with the composition ML3(OOCBut)2 were obtained
as the major products, when the reaction products were
rapidly isolated from concentrated ethanolic solutions.
These structurally similar products are the known monoꢀ
Complex 7 contains the {Ni4(µ3ꢀOMe)4} fragment as
opposed to {Ni4(µ3ꢀOH)4} found in cation 4, which is
formed in EtOH. Apparently, this fact is attributed to
insignificant, at first glance, steric hindrance, which
appears after the replacement of the methyl group by the
ethyl group, although the difference in the tendency of
the bridging methoxy and ethoxy groups to hydrolysis
cannot be ruled out.
According to Xꢀray diffraction data, the geometrical
characteristics of the {NiII O4} metal core (Ni—O, 2.003(3)—
4
2.068(3) Å; the O—Ni—O angle, 79.42(13)—88.77(13)°)
in cluster 7 (Fig. 2) are similar to those found in the
known5 complex Ni4(µ3ꢀOMe)4(µ2ꢀOOCBut)2(η2ꢀOOCBut)2ꢀ
Scheme 2
— η2-OOCBut
M = Ni, n = 6 (2)

14
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Fomina et al.
(MeOH)4, which also contains methoxide bridges. The
metal atoms in cluster 7 are at nonbonding distances. It
should be noted that the distances between the metal
centers coordinated by the bridging pivalate anions in the
dinuclear Ni(1)...Ni(3) and Ni(2)...Ni(4) fragments
(2.8691(11) and 2.9133(11) Å, respectively) are substanꢀ
tially shorter than the other distances (Ni(1)...Ni(2),
3.116(1) Å; Ni(1)...Ni(4), 3.162(1) Å; Ni(2)...Ni(3),
3.114(1) Å; Ni(3)...Ni(4), 3.161(1) Å). The Ni(4) and
Ni(2) atoms belonging to one side of the cubane are
equivalently coordinated by the chelate diamine ligands
(Ni(4)—N, 2.081(4) and 2.102(4) Å; Ni(2)—N, 2.058(4)
and 2.9133(11) Å). The metal chelate fragments are virtuꢀ
ally planar, like those in the cobalt and iron complexes
studied earlier;18,26,27 however, this coordination mode
was not described for compounds containing nickel atoms.
The Ni(1) and Ni(3) atoms belonging to the opposite side
of the cubane are linked by the bridging pivalate anion
(Ni—O, 2.033(4) and 2.020(4) Å) in the dinuclear fragment,
but these nickel are are in a different ligand environment.
The environment of Ni(1) includes two oxygen atoms of
the chelate pivalate anion (Ni—O, 2.094(4)—2.136(4) Å),
whereas the environment of Ni(3) includes the monoꢀ
dentate pivalate anion (Ni—O, 2.050(3) Å) and the methaꢀ
nol molecule (Ni—O, 2.108(4) Å). Therefore, each metal
center in cluster 7 is in an octahedral environment. The
hydrogen atoms of the amino group of the diamine ligand
is linked to the oxygen atom of the pivalate anion, which
is coordinated to Ni(1) in a monodentate fashion, by an
intramolecular hydrogen bond (N(1)—H(1B), 0.92 Å;
H(H1B)—O(4), 2.35 Å; N(1)—H(1B)...O(4), 3.14 Å;
N(1)—H(1B)...O(4), 143.6°). In addition, there are short
hydrogen bonds between the hydrogen atoms of the amino
groups of the coordinated diamine ligands and the oxygen
atoms of the pivalic acid and methanol solvent molecules.
Magnetic properties of new cubanes. The magnetic
studies showed that complexes 3 and 4 containing the
cubaneꢀlike core exhibit unusual magnetic behavior.
According to magnetic measurements, the effective magꢀ
netic moment µeff of cobaltꢀcontaining cluster 3 remains
virtually unchanged in the 300—50 K temperature range
(9.80—9.67 µB), but it sharply increases to 10.20 µB in the
range of 50—8 K. In the 8—2 K temperature range, µeff
substantially decreases to 9.00 µB (Fig. 3, a) due apparꢀ
ently to intermolecular antiferromagnetic exchange
interactions.
µeff/µ
a
B
10.2
10.0
9.8
9.6
9.4
9.2
9.0
0
50
100 150 200
250 300 T/K
µeff/µ
b
B
8.5
8.0
7.5
7.0
6.5
6.0
C(18)
C(17)
0
50
100
150
200
250
300 T/K
C(19)
C(20)
µ
eff/µ
c
B
O(7)
O(9)
C(16)
O(8)
10
9
N(4)
C(30)
C(31)
C(35)
C(36)
Ni(2)
C(32)
N(2)
C(23)
C(22)
C(27)
C(24)
Ni(4)
C(39)
C(29)
8
C(33)
N(3)
C(34)
Ni(1)
C(2)
N(1)
O(11)
O(12)
C(21)
C(25)
C(26)
C(3)
O(1)
C(28)
O(2)
7
C(40)
C(38)
O(10)
O(13)
C(41)
6
C(8)
Ni(3)
O(3)
O(4)
C(6)
C(7)
C(10)
5
O(5)
O(6)
C(9)
C(11)
4
C(14)
C(15)
C(12)
C(13)
50
100 150 200 250 300 T/K
Fig. 2. Structure of complex 7.
Fig. 3. Magnetic properties of complexes 3 (a), 4 (b), and 8 (c).

{MI4IO4} (M = Co, Ni) pivalates with cubane core
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
15
m/mg
This behavior strongly differs from the magnetic propꢀ
erties of the known symmetrical cubane [Co4(µ3ꢀOMe)4ꢀ
(µ2ꢀOOCBut)2(η2ꢀOOCBut)2(MeOH)4]•4MeOH (8),11
which we synthesized according to the new method by
recrystallization of the tetranuclear complex [Co4(µ3ꢀOH)2ꢀ
(µ2ꢀOOCBut)4(η2ꢀOOCBut)2(EtOH)4]•2EtOH with the
planar metal core from methanol.28
a
4
20
15
10
5
3
According to the results of magnetic measurements,
the effective magnetic moment of complex 8 monotoniꢀ
cally decreases throughout the 300—2 K temperature range
from 9.82 to 4.20 µB due to spinꢀorbital and spinꢀspin
antiferromagnetic exchange interactions (Fig. 3, c).
Nickelꢀcontaining cubane 4 exhibits ferromagnetic
properties in the 300—8 K temperature range, where
the effective magnetic moment µeff of 4 monotonically
increases from 6.60 to 8.56 µB. In the 8—2 K temperature
rangef, µeff substantially decreases (to 7.72 µB) due apparꢀ
ently to intermolecular spinꢀspin antiferromagnetic
exchange interactions (Fig. 3, b).
0
100
200
300
400
500 T/°C
Q/mW
b
0
–5
3
4
–10
–15
100
200
300
400
500 T/°C
The magnetic properties of compound 4 substantially
differ from those of the complex Ni4(OOCBut)4(Mq)4
(Mq is the 8ꢀhydroxyquinoline anion), which is characꢀ
terized by the following two types of exchange interacꢀ
tions: ferromagnetic interactions within the Ni2 pairs
linked by the bridging 8ꢀhydroxyquinoline anions and
antiferromagnetic interactions between these pairs. As a
result, the ground state of the system is diamagnetic.12
However, the properties of compound 4 are similar to
those of the known cubane Ni4(µ3ꢀOMe)4(µ2ꢀOOCBut)2ꢀ
(η2ꢀOOCBut)2(MeOH)4 (9)5 characterized by ferromagꢀ
netic splitting for all four metal centers.
Thermolysis of complexes. To study the stability limits
and the possibility of generating oxide materials from the
newly synthesized cubanes, we studied the solidꢀstate therꢀ
molysis of the following pairs of compounds: the ionic
tetranuclear complexes [M4(µ3ꢀOH)4(η1ꢀOOCBut)3ꢀ
(µꢀ(NH2)2C6H2Me2)3(η1ꢀ(NH2)2C6H2Me2)3]+(OOCBut)–
(M = CoII (3) and NiII (4)) containing µ3ꢀhydroxide
bridges and cubanes [M4(µ3ꢀOMe)4(µ2ꢀOOCBut)2ꢀ
(η2ꢀOOCBut)2(MeOH)4]•4MeOH (M = CoII (8) and
NiII (9)) containing µ3ꢀmethoxide bridges.
Fig. 4. Temperature dependences of the weight loss (a) and the
heat flux (b) for compounds 3 and 4.
study, it is impossible to separate the steps of elimination
of the coordinated and bridging diamine ligands based on
the temperature dependence of the weight loss (see Fig. 4, а).
Taking into account the temperature dependence of the
heat flux (see Fig. 4, b), it can be suggested that the
removal of coordinated ligands occurs in the temperature
ranges of 160—210 °C (3) and 180—260 °C (4). The step
of complete destruction of the complexes giving rise to the
structures of the final solid decomposition products proꢀ
ceeds in the temperature range of 320—500 and 430—520 °C
for 3 and 4, respectively. The total weight losses are
80.0 1.5 and 79.8 1.5% for 3 and 4, respectively. Oxides
with the composition MO are the final solid decomposiꢀ
tion products of both complexes (Tables 1 and 2).
Table 1. Xꢀray powder diffraction analysis of the solid decompoꢀ
sition products of cobaltꢀcontaining cubanes 3 and 8
3
8
CoO[43ꢀ1004]* Co3O4[43ꢀ1003]*
The experimental data suggest that the decomposition
of isostructural complexes 3 and 4 proceeds by the same
mechanism (Fig. 4). Endothermic processes without
weight loss are observed in the 48—110 °C temperature
range, which is apparently associated with the cleavage
of intramolecular hydrogen bonds. The decomposition of
complexes 3 and 4 starts at 160 2 °C and 180 2 °C,
respectively. The first decomposition step (160—260 °C
for 3 and 180—330 °C for 4) is endothermic and is
accompanied by the weight loss of 51.7 1.5% (3) and
51.8 1.5% (4). In these temperature ranges, the diamine
ligands are apparently eliminated (the theoretical perꢀ
centage of these ligands in the complexes is 53.54%).
Under the experimental conditions used in the present
d/Å I (%)
d/Å I (%) d/Å I (%)
d/Å
I (%)
—
—
—
—
4.630 10
2.860 20
—
—
2.4595
—
—
—
67
—
4.6670
2.8580
—
2.4374
—
2.0210
1.5558
—
16
33
—
100
—
20
32
—
2.460 50
—
—
2.437 100
2.130 100
—
—
2.1300 100
—
—
—
—
2.020 30
1.560 40
—
—
1.5061
—
—
50
1.500 50
—
—
—
—
1.423 30
—
—
1.4291
38
* Powder Diffraction File, Swarthmore: Joint Committee on
Powder Diffraction Standards, card.

16
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Fomina et al.
Table 2. Xꢀray powder diffraction analysis of the solid decompoꢀ
sition products of nickelꢀcontaining cubanes 4 and 9
m/mg
a
12
10
8
4
9
Ni[04ꢀ0850]*
NiO[44ꢀ1159]*
9
d/Å
2.4210
I (%) d/Å I (%) d/Å I (%)
d/Å I (%)
20 2.4120
50
—
—
—
—
2.4119 60
2.0884 100
8
6
2.0850 100 2.090 100
4
—
—
1.4825
—
—
—
2.0405 100 2.034 100
—
—
—
—
1.7550
40 1.762 42
30
100
200
300
400
T/°C
40 1.4725
1.2200
1.4773 30
—
—
10 1.246 21
—
Q/mW
b
* Powder Diffraction File, Swarthmore: Joint Committee on
Powder Diffraction Standards, card.
15
10
5
For complexes 8 and 9, processes accompanied by the
weight loss and endotherms (Fig. 5) are observed immeꢀ
diately after the temperature started to increase (the beꢀ
ginning at 40 2 °C). In the 40—65 °C temperature range,
the weight loss is 12.5 1.0% (8) and 13.1 1.0% (9). These
processes involve the elimination of methanol solvent
molecules (the theoretical percentage of methanol solꢀ
vent molecules is 12.55%). In the 65—145 and 65—180
°C temperature ranges, the weigh loss is 13.08 1.0 and
12.6 1.0% for compounds 8 and 9, respectively (the proꢀ
cess is endothermic). This process corresponds to the reꢀ
moval of coordinated methanol, whose theoretical conꢀ
tent is 12.55%. When compounds 8 and 9 were further
heated to 185 and 200 °C, respectively, no changes were
detected. At temperatures higher than those mentioned
above, the complexes undergo final destruction accomꢀ
panied by rather complex energy changes. The temperaꢀ
ture, at which complete decomposition and the formation
of the final solid decomposition products of compounds 8
and 9 are observed, is 352 and 375 °C, respectively. The
total weight loss in the temperature range under study is
69.2 1.0% (8) and 73.6 1.0% (9). According to Xꢀray
powder diffraction data, mixedꢀvalence oxide Co3O4 and
a virtually equimolar mixture of Ni and NiO are formed as
the final decomposition products of compounds 8 and 9,
respectively (see Tables 1 and 2).
Earlier,25,29—31 we have shown that the thermal deꢀ
composition of differentꢀnuclearity CoII carboxylate comꢀ
plexes under inert atmosphere in the 190—220 °C temꢀ
perature range is accompanied by aggregation giving rise
to the volatile octanuclear complex Co8(µ4ꢀO)2(µ2ꢀ
OOCBut)6(µ3ꢀOOCBut)6. Another situation was observed
in studies of the thermolysis of cobaltꢀcontaining comꢀ
plexes 3 and 8 (see Tables 1 and 2). The decomposition of
these complexes affords cobalt oxides as the final solid
products. This is apparently attributed, first, to high therꢀ
mal stability of these compounds, second, to the high
boiling point of the Nꢀdonor ligand, and, third, to the
structural features of the metal core. The formation of
Co3O4 by thermolysis of 8 is apparently associated with
the presence of the bridging pivalate groups. In this case,
8
0
–5
9
–10
100
200
300
400
T/°C
Fig. 5. Temperature dependences of the weight loss (a) and the
heat flux (b) for compounds 8 and 9.
the CO2 fragments, which are formed as a result of cleavꢀ
age of pivalate ligands, act as an oxidizing agent. The
thermolysis of nickelꢀcontaining complexes 4 and 9 is
also a destructive process, the phase composition of the
decomposition products being determined by the nature
of coordinated ligands and the structural features of the
metal core, as has been shown earlier for other nickel(II)
pivalate complexes.25,29—31
Experimental
All synthetic operations were carried out under pure argon
with the use of deaerated solvents and the standard Schlenk
technique. The starting polynuclear cobalt and nickel pivalates
were synthesized according to known procedures.25,28,32 The
synthesis of new compounds was carried out with the use of
trimethylacetic acid (Acros Organics) and 4,5ꢀdimethylꢀ1,2ꢀpheꢀ
nylenediamine (Aldrich).
The IR spectra were recorded on a Specord Mꢀ80 spectroꢀ
photometer in KBr pellets. The static magnetic susceptibility
was measured on a SQUID MPMSꢀ5S Quantum Design magꢀ
netometer in the 2—300 K temperature range. The effective magꢀ
netic moments were calculated by the equation µeff = (8χ T)1/2
.
The thermal decomposition of compounds 3, 4, 8, anMd 9 was
studied by differential scanning calorimetry (DSC) and thermoꢀ
gravimetry (TG) on DSCꢀ20 and TGꢀ50 units of a Mettler
TAꢀ3000 thermoanalyzer. For each compound, three DSC
experiments and three TG experiments were performed. The
weight loss upon thermal degradation was determined directly
on the TGꢀ50 unit; the accuracy of weighing was 2•10–3 mg.
The thermal decomposition was studied in steps by differential
scanning calorimetry, which involved the division of the total

{MI4IO4} (M = Co, Ni) pivalates with cubane core
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
17
temperature range into intervals. The size and the number of
these intervals were determined based on the overall patterns of
the weight loss and the energy change upon decomposition. The
accuracy of the determination of anomalous points and thermal
effects in the DSC curves was 1° and 0.5%, respectively.
hexane, and dried under argon. The yield of the compound
4•4EtOH•1.5H2O was 0.388 g (78%). Found (%): C, 52.81;
H, 7.69; N, 9.72. C76H135N12Ni4O17.50. Calculated (%):
C, 52.66; H, 7.80; N, 9.70. IR, ν/cm–1: 3476 m, 3408 m, 3348 s,
3320 v.s, 3280 s, 3236 m, 3148 m, 2952 m, 2928 m, 2864 m,
1628 m, 1592 v.s, 1560 s, 1552 v.s, 1536 v.s, 1516 v.s, 1480 v.s,
1460 s, 1404 s, 1384 m, 1356 s, 1296 m, 1220 m, 1092 m, 1048 s,
1024 s, 996 s, 884 m, 872 m, 824 m, 796 m, 728 m, 700 m,
660 m, 616 m, 600 m, 544 w, 484 w, 472 w, 448 w, 404 w, 384 w,
368 w, 324 w. Crystals suitable for Xꢀray diffraction study were
obtained.
1
Tetra(µ ꢀhydroxo)tris(η ꢀtrimethylacetato)tris(µꢀ4,5ꢀdiꢀ
3
1
methylꢀ1,2ꢀphenylenediamino)tris(η ꢀ4,5ꢀdimethylꢀ1,2ꢀpheꢀ
nylenediamino)tetracobalt(II) trimethylacetate ethanol and water
1
solvate, [Co4(µ ꢀOH)4(η ꢀOOCBut)3(µꢀ(NH2)2C6H2Me2)3ꢀ
3
(η ꢀ(NH2)2C6H2Me2)3]+(OOCBut)–•4EtOH•1.5H2O
1
(3•4EtOH•1.5H2O). A. Ethanol (60 mL) was added to the
complex [Co(OOCBut)2)]n (1) (0.4 g, 1.53 mmol per formula
unit Co(OOCBut)2) and 4,5ꢀdimethylꢀ1,2ꢀphenylenediamine
(0.418 g, 3.07 mmol), and the reaction mixture was heated
under argon at 60 °C until the starting reagents completely disꢀ
solved. The brightꢀpink solution was filtered, concentrated at
0.1 Torr and 20 °C to 40 mL, and kept at 20 °C. Brightꢀpink
crystals that precipitated after 12 h were separated by decantaꢀ
tion, washed with cold ethanol and hexane, and dried under
argon. The yield of the compound 3•4EtOH•1.5H2O was 0.505 g
(76% based on the starting amount of cobalt). Found (%):
C, 52.81; H, 7.58; N, 9.47. C76H135Co4N12O17.50. Calculated (%):
C, 52.63; H, 7.79; N, 9.70. IR, ν/cm–1: 3484 m, 3432 m, 3404 m,
3320 v.s, 3312 v.s, 3264 m, 3156 m, 3052 w, 3020 w, 2972 m,
2952 m, 2932 m, 2900 m, 2868 m, 1632 m, 1592 v.s, 1564 s, 1512 v.s,
1480 v.s, 1456 s, 1404 s, 1356 s, 1296 m, 1260 v.w, 1216 m, 1092 m,
1048 s, 1028 s, 1000 m, 960 m, 952 m, 884 m, 824 m, 796 m, 776 w,
728 m, 696 m, 668 m, 644 m, 616 m, 600 m, 540 w, 480 w, 468 w,
444 w, 424 w, 396 w, 352 w, 324 w. Crystals suitable for Xꢀray
diffraction study were obtained.
B. Ethanol (70 mL) was added to complex 6 (0.3 g,
0.448 mmol), and the mixture was heated under argon at 60 °C
until complete dissolution of 6. The brightꢀblue solution was
filtered, concentrated at 0.1 Torr and 20 °C to 40 mL, and kept
at 20 °C. Brightꢀblue crystals that precipitated after 12 h
were separated by decantation, washed with cold ethanol and
hexane, and dried under argon. The yield of the compound
4•4EtOH•1.5H2O was 0.151 g (78%). Found (%): C, 52.74;
H, 7.66; N, 9.68. C76H135N12Ni4O17.50. Calculated (%):
C, 52.66; H, 7.80; N, 9.70. IR, ν/cm–1: 3476 m, 3408 m, 3348 s,
3320 v.s, 3280 s, 3236 m, 3148 m, 2952 m, 2928 m, 2864 m,
1632 m, 1592 v.s, 1560 s, 1552 v.s, 1536 v.s, 1516 v.s, 1480 v.s,
1456 s, 1400 s, 1384 m, 1356 s, 1296 m, 1216 m, 1100 m, 1048 s,
1028 s, 996 s, 884 m, 870 m, 824 m, 796 m, 728 m, 700 m,
656 m, 604 m, 536 w, 464 w, 472 w, 444 w, 408 w, 384 w, 352 w,
324 w, 312 w. Crystals suitable for Xꢀray diffraction study were
obtained.
2
1
Mono(η ꢀ4,5ꢀdimethylꢀ1,2ꢀphenylenediamino)bis(η ꢀ4,5ꢀdiꢀ
1
methylꢀ1,2ꢀphenylenediamino)bis(η ꢀpivalato)cobalt(II),
2
1
B. Ethanol (70 mL) was added to complex 5 (0.3 g,
0.448 mmol), and the mixture was heated under argon at 60 °C
until complete dissolution of compound 5. The brightꢀpink
solution was filtered, concentrated at 0.1 Torr and 20 °C to
40 mL, and kept at 20 °C. Brightꢀpink crystals that precipitated
after 12 h were separated by decantation, washed with cold
ethanol and hexane, and dried under argon. The yield of the
compound 3•4EtOH•1.5H2O was 0.151 g (78% based on the
starting amount of cobalt). Found (%): C, 52.84; H, 7.75;
N, 9.74. C76H135Co4N12O17.50. Calculated (%): C, 52.63;
H, 7.79; N, 9.70. IR, ν/cm–1: 3480 m, 3436 m, 3404 m, 3324 v.s,
3312 v.s, 3264 m, 3152 m, 3052 w, 3020 w, 2972 m, 2956 m,
2924 m, 2900 m, 2864 m, 1628 m, 1592 v.s, 1564 s, 1516 v.s,
1480 v.s, 1460 s, 1404 s, 1356 s, 1296 m, 1260 v.w, 1216 m, 1088 m,
1048 s, 1024 s, 996 m, 952 m, 952 m, 880 m, 872 m, 824 m,
796 m, 776 w, 728 m, 696 m, 648 m, 616 m, 600 m, 540 w,
480 w, 468 w, 444 w, 404 w, 356 w, 328 w. Crystals suitable
for Xꢀray diffraction study were obtained.
Co(η ꢀ(NH2)2C6H2Me2)(η ꢀ(NH2)2C6H2Me2)2(OOCBut)2 (5).
A. Ethanol (60 mL) was added to the complex [Co(OOCBut)2)]n
(1) (0.4 g, 1.53 mmol per formula unit Co(OOCBut)2) and
4,5ꢀdimethylꢀ1,2ꢀphenylenediamine (0.418 g, 3.07 mmol),
and the reaction mixture was heated under argon at 60 °C until
the starting reagents completely dissolved. The brightꢀpink soluꢀ
tion was filtered, concentrated at 0.1 Torr and 20 °C to 20 mL,
and kept at 20 °C. Pink crystal that precipitated after 12 h were
separated by decantation, washed with cold ethanol and hexane,
and dried under argon. The yield of compound 5 was 0.739 g
(72%). Found (%): C, 60.52; H, 7.91; N, 12.49. C34H54CoN6O4.
Calculated (%): C, 61.00; H, 8.07; N, 12.51. IR, ν/cm–1
:
3404 s, 3352 m, sh, 2960 s, 2924 m, 2864 w, 1548 s, 1516 s,
1476 s, 1456 s, 1400 s, 1408 m, 1352 m, 1296 m, 1260 w, 1220 m,
1200 m, 1136 w, 1088 w, 992 m, 888 w, 864 w, 828 m, 796 m,
740 m, 720 m, 692 w, 660 w, 624 w, 596 m, 548 m, 464 m, 432 w,
400 w, 364 w, 312 w. The crystals obtained were studied by
Xꢀray diffraction. The crystallographic parameters for comꢀ
pound 5 (space group P1, a = 12.951(4) Å, b = 16.368(5) Å,
c = 19.221(6) Å, α = 77.560(5)°, β = 73.239(6)°, γ = 70.594(9)°,
1
Tetra(µ ꢀhydroxo)tris(η ꢀtrimethylacetato)tris(µꢀ4,5ꢀdiꢀ
3
1
methylꢀ1,2ꢀphenylenediamino)tris(η ꢀ4,5ꢀdimethylꢀ1,2ꢀpheꢀ
3
nylenediamino)tetranickel(II) trimethylacetate ethanol and water
V = 3647(2) Å , Z = 4) correspond to those of the molecular
1
2
1
solvate, [Ni4(µ ꢀOH)4(η ꢀOOCBut)3(µꢀ(NH2)2C6H2Me2)3ꢀ
structure of Co(η ꢀ(NH2)2C6H2Me2)(η ꢀ(NH2)2C6H2Me2)2ꢀ
3
(η ꢀ(NH2)2C6H2Me2)3]+(OOCBut)–•4EtOH•1.5H2O
(OOCBut)2 established earlier by Xꢀray diffraction.26
1
(4•4EtOH•1.5H2O). A. Ethanol (60 mL) was added to the
complex Ni6(µ ꢀOOCBut)6(µ ꢀOOCBut)6 (2) (0.3 g, 0.192 mmol)
and 4,5ꢀdimet2hylꢀ1,2ꢀpheny3lenediamine (0.313 g, 2.3 mmol),
and the reaction mixture was heated under argon at 60 °C until
the starting reagents completely dissolved. The brightꢀblue
solution was filtered and concentrated at 0.1 Torr and 20 °C to
40 mL. Brightꢀblue crystals that precipitated after 12 h
were separated by decantation, washed with cold ethanol and
B. Methanol (60 mL) was added to the complex [Co(OOCBut)2)]n
(1) (0.4 g, 1.53 mmol per formula unit Co(OOCBut)2) and
4,5ꢀdimethylꢀ1,2ꢀphenylenediamine (0.418 g, 3.07 mmol),
and the reaction mixture was heated under argon at 60 °C until
the starting reagents were completely dissolved. The brightꢀpink
solution was filtered, concentrated at 0.1 Torr and 20 °C to
20 mL, and kept at 20 °C. Pink crystal that precipitated after
12 h were separated by decantation, washed with cold methanol

18
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Fomina et al.
and hexane, and dried under argon. The yield of compound 5
was 0.739 g (72%). Found (%): C, 60.73; H, 8.10; N, 12.55.
C34H54CoN6O4. Calculated (%): C, 61.00; H, 8.07; N, 12.51.
IR, ν/cm–1: 3404 s, 3348 m, sh, 3272 m, 2956 s, 2924 m,
2900 m, 2864 w, 1552 s, 1520 s, 1476 s, 1456 s, 1400 s, 1352 m,
1332 w, 1296 m, 1260 w, 1220 m, 1200 m, 1136 w, 1088 w,
992 m, 888 w, 872 m, 864 m, 828 m, 796 m, 740 m, 720 m,
692 w, 660 w, 624 w, 596 m, 548 m, 464 m, 432 w, 400 w, 364 w,
312 w. The crystals obtained were studied by Xꢀray diffraction.
The crystallographic parameters for compound 5 (space group
P1, a = 12.951(4) Å, b = 16.368(5) Å, c = 19.221(6) Å,
V = 3677(3) Å3, Z = 4) correspond to those of the molecular
2
1
structure of Fe(η ꢀ(NH2)2C6H2Me2)(η ꢀ(NH2)2C6H2Me2)2ꢀ
(OOCBut)2 established earlier by Xꢀray diffraction.27
1
Tetra(µ ꢀmethoxo)mono(η ꢀtrimethylacetato)monoꢀ
3
2
(η ꢀO,O´ꢀtrimethylacetato)bis(µ ꢀO,O´ꢀtrimethylacetato)bisꢀ
2
2
1
(η ꢀ4,5ꢀdimethylꢀ1,2ꢀphenylenediamino)mono(η ꢀmethanol)ꢀ
tetranickel pivalic acid and methanol solvate, [Ni4(µ ꢀOMe)4ꢀ
3
1
2
2
(η ꢀOOCBut)(η ꢀOOCBut)(µ ꢀOOCBut)2(η ꢀ(NH2)2C6H2Me2)2ꢀ
(MeOH)]•HOOCBut •M2eOH
(7•HOOCBut•MeOH).
3
A. Methanol (60 mL) was added to the complex Ni6(µ ꢀOOꢀ
2
CBut)6(µ ꢀOOCBut)6 (2) (0.3 g, 0.192 mmol) and 4,5ꢀdimethylꢀ
3
3
α = 77.560(5)°, β = 73.239(6)°, γ = 70.594(9)°, V = 3647(2) Å ,
Z = 4) correspond to those of the molecular structure of
1,2ꢀphenylenediamine (0.313 g, 2.3 mmol), and the reacꢀ
tion mixture was heated under argon at 60 °C until the
starting reagents completely dissolved. The brightꢀblue soluꢀ
tion was filtered and concentrated at 0.1 Torr and 20 °C to
35—40 mL. Brightꢀblue crystals that precipitated after 12 h
were separated by decantation, washed with cold methanol and
hexane, and dried under argon. The yield of the compound
7•HOOCBut•MeOH was 0.262 g (72%). Found (%): C, 46.54;
H, 7.69; N, 4.45. C49H97N4Ni4O18. Calculated (%): C, 46.52;
H, 7.73; N, 4.43. IR, ν/cm: 3392 m, 3340 m, 3250 m, 2960 s,
2924 s, 2816 m, 1692 m, 1664 m, 1568 s, 1536 s, 1508 s, 1480 s,
1456 m, 1432 m, 1412 s, 1360 s, 1296 w, 1280 w, 1224 s, 1184 m,
1048 v.s, 1000 m, 980 m, 936 w, 900 w, 884 m, 876 m, 812 w, 792 m,
608 m, 448 m, 412 m, 320 w. Crystals suitable for Xꢀray diffracꢀ
tion study were obtained.
2
1
Co(η ꢀ(NH2)2C6H2Me2)(η ꢀ(NH2)2C6H2Me2)2(OOCBut)2
determined earlier by Xꢀray diffraction.26
2
1
Mono(η ꢀ4,5ꢀdimethylꢀ1,2ꢀphenylenediamino)bis(η ꢀ4,5ꢀdiꢀ
1
2
methylꢀ1,2ꢀphenylenediamino)bis(η ꢀpivalato)nickel(II), Ni(η ꢀ(NH2)2ꢀ
C6H2Me2)(η ꢀ(NH2)2C6H2Me2)2(OOCBut)2 (6). A. Ethanol
1
(60 mL) was added to the complex Ni6(µ ꢀOOCBut)6(µ ꢀOOCBut)6
(2) (0.3 g, 0.192 mmol) and 4,5ꢀdimeth2ylꢀ1,2ꢀphenyl3enediamine
(0.313 g, 2.3 mmol), and the reaction mixture was heated under
argon at 60 °C until the starting reagents completely dissolved.
The brightꢀblue solution was filtered and concentrated at
0.1 Torr and 20 °C to 20 mL. Blue crystal that precipitated after
12 h were separated by decantation, washed with cold ethanol
and hexane, and dried under argon. The yield of compound 6
was 0.601 g (78%). Found (%): C, 60.58; H, 8.01; N, 12.65.
C34H54N6NiO4. Calculated (%): C, 60.99; H, 8.13; N, 12.55.
IR, ν/cm–1: 3404 m, 3352 m, 3304 m, 3290 m, 3240 m, 3232 m,
3008 w, 2956 m, 2920 m, 2864 m, 1640 w, 1624 m, 1560 s,
1536 v.s, 1516 v.s, 1480 v.s, 1456 s, 1448 s, 1400 m, 1356 s,
1296 m, 1260 m, 1216 m, 1152 m, 1100 w, 1016 s, 996 s, 888 m,
864 m, 832 w, 792 m, 776 m, 740 w, 720 m, 700 m, 656 m,
604 w, 536 w, 464 w, 444 w, 408 w, 384 w, 352 w, 312 w. The
crystals obtained were studied by Xꢀray diffraction. The crysꢀ
tallographic parameters for compound 6 (space group Pꢀ1,
a = 12.932(6) Å, b = 16.430(8) Å, c = 19.325(8) Å,
The magnetic measurements showed that the effective magꢀ
netic moment of cluster 6 monotonically increases as the temꢀ
perature decreases from 300 to 60.08 K (µ = 4.41—4.59 µ )
eff
B
and then sharply increases (from 4.59 to 8.65 µ ) in the
B
60.08—4.50 K temperature range, passing through a maximum.
In the 4.50—2 K temperature range, the magnetic moment
substantially decreases (to 6.64 µ ).
B. Methanol (60 mL) was Badded to complex 6 (0.3 g,
0.448 mmol), and the mixture was heated under argon at 60 °C
until complete dissolution of starting compound 6. The brightꢀ
blue solution was filtered, concentrated at 0.1 Torr and 20 °C to
40 mL, and kept at 20 °C. Brightꢀblue crystals that precipitated
after 12 h were separated by decantation, washed with cold
methanol and hexane, and dried under argon. The yield of the
solvate of compound 7•HOOCBut•MeOH was 0.108 g (76%).
Found (%): C, 46.56; H, 7.67; N, 4.40. C49H97N4Ni4O18. Calꢀ
culated (%): C, 46.52; H, 7.73; N, 4.43. IR, ν/cm–1: 3392 m,
3344 m, 3250 m, 2964 s, 2924 s, 2816 m, 1692 m, 1664 m, 1564 s,
1536 s, 1508 s, 1484 s, 1456 m, 1432 m, 1412 s, 1360 s, 1292 w,
1280 w, 1224 s, 1184 m, 1048 v.s, 1000 m, 980 m, 936 w, 900 w,
884 m, 876 m, 812 w, 792 m, 608 m, 448 m, 412 m. Crystals
suitable for Xꢀray diffraction were obtained.
3
α = 77.479(7)°, β = 73.210(13)°, γ = 70.719(9)°, V = 3677(3) Å ,
Z = 4) correspond to those of the molecular structure of
2
1
Fe(η ꢀ(NH2)2C6H2Me2)(η ꢀ(NH2)2C6H2Me2)2(OOCBut)2
determined earlier by Xꢀray diffraction.27
B. Methanol (60 mL) was added to the complex
Ni6(µ ꢀOOCBut)6(µ ꢀOOCBut)6 (2) (0.3 g, 0.192 mmol) and
4,5ꢀd2imethylꢀ1,2ꢀp3henylenediamine (0.313 g, 2.3 mmol),
and the reaction mixture was heated under argon at 60 °C until
the starting reagents completely dissolved. The brightꢀblue
solution was filtered and concentrated at 0.1 Torr and 20 °C to
20 mL. Blue crystal that precipitated after 12 h were separated
by decantation, washed with cold methanol and hexane, and
dried under argon. The yield of compound 6 was 0.585 g (76%).
Found (%): C, 60.75; H, 8.07; N, 12.48. C34H54N6NiO4. Calꢀ
culated (%): C, 60.99; H, 8.13; N, 12.55. IR, ν/cm–1: 3404 m,
3348 m, 3300 m, 3236 m, 3232 m, 2960 m, 2952 m, 2924 m,
2866 m, 1632 w, 1624 m, 1568 s, 1536 v.s, 1516 v.s, 1476 v.s,
1456 s, 1448 s, 1404 m, 1356 s, 1332 w, 1300 m, 1260 m, 1220 m,
1140 m, 1092 w, 1016 s, 996 s, 888 m, 864 m, 832 w, 792 m, 776 m,
740 w, 720 m, 700 m, 668 w, 628 w, 600 w, 548 w, 468 w, 436 w,
404 w, 368 w, 324 w, 316 w. The crystals obtained were studied
by Xꢀray diffraction. The crystallographic parameters for comꢀ
pound 6 (space group Pꢀ1, a = 12.932(6) Å, b = 16.430(8) Å,
c = 19.325(8) Å, α = 77.479(7)°, β = 73.210(13)°, γ = 70.719(9)°,
Tetra(µ ꢀmethoxo)bis(µ ꢀO,O´ꢀtrimethylacetato)bis(µ ꢀO,O´ꢀ
3
2
trimethylacetato)tetra(η ꢀmethanol)tetracobalt(II) m2ethanol
1
tetrasolvate, [Co4(µ ꢀOMe)4(µ ꢀOOCBut)2(η ꢀOOCBut)2ꢀ
2
(MeOH)4]•4MeOH (8•4MeOH).2Methanol (40 mL) was added
3
to the complex [Co4(µ ꢀOH)2(µ ꢀOOCBut)4(η ꢀOOCBut)2ꢀ
2
3
2
(EtOH)4]•2EtOH (0.3 g, 0.26 mmol), and the mixture was
stirred under argon at 60 °C until complete dissolution of the
starting compound. The crimson solution was filtered and
concentrated at 0.1 Torr and 20 °C to 10 mL. Pink crystals that
precipitated after 8 h were separated by decantation, washed
with cold methanol and hexane, and dried under argon. The
yield of the compound 8•4MeOH was 0.26 g (98%). Found
(%): C, 37.60; H, 7.74, N, 0.00. C32H80Co4O20. Calculated

{MI4IO4} (M = Co, Ni) pivalates with cubane core
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
19
Table 3. Crystallographic parameters for the complexes 3•4EtOH•1.5H2O and 7•HOOCBut•MeOH
Parameter
3•4EtOH•1.5H2O
7•НOOCBut•MeОН
Molecular formula
Molecular weight
Space group
a/Å
b/Å
C76H135Co4N12O17.50
1732.68
P4/n
C49H97N4Ni4O18
1265.15
Pꢀ1
35.763(8)
35.763(8)
14.957(3)
90
90
90
19129(7)
8
1.203
12.145(3)
14.463(4)
18.626(5)
86.09(1)
85.53(1)
70.97(1)
3080.3(14)
2
c/Å
α/deg
β/deg
γ/deg
V//Å3
Z
ρ
calc/g cm–3
1.364
1.270
µ/mm–1
0.745
θ—2θꢀScan range/deg
Number of measured reflections
Number of reflections with I > 2σ(I)
1.61—27.57
102865
18667
1.49—27.48
25754
13574
R1
wR2
0.0711
0.1886
0.0666
0.1728
(%): C, 37.69; H, 7.91; N, 0.00. IR, ν/cm–1: 3384 s, 3268 m,
2960 s, 2928 s, 2912 s, 2872 s, 2836 m, 1684 m, 1668 m, 1584 v.s,
1572 v.s, 1564 s, 1552 s, 1536 s, 1484 s, 1456 m, 1416 s, 1372 m,
1360 s, 1260 w, 1224 s, 1108 w, 1032 m, 936 w, 896 m, 796 s,
616 m, 608 m, 460 w, 416 m, 324 w. The crystals obtained were
studied by Xꢀray diffraction. The crystallographic parameters for
the compound 8•4MeOH (space group Pbca, a = 15.327(11) Å,
b = 41.83(3) Å, c = 15.887(9) Å, α = 90°, β = 90°, γ = 90°,
V = 10186(11) Å3, Z = 8) correspond to those of the moleꢀ
time of 30 s per frame) according to a standard procedure.33
Semiempirical absorption corrections were applied.33 Crystals
of 4•4EtOH•1.5H2O are tetragonal, space group P4/n,
a = 35.621(9) Å, b = 35.621(9) Å, c = 14.932(4) Å, V = 18947(9) Å3.
The crystallographic parameters and the refinement statistics
for the structures of 3 and 7 are given in Table 3. For the
compound 3•4EtOH•1.5H2O, the hydrogen atoms of the
tertꢀbutyl substituents of the pivalate ligands and the aromatic
rings in the coordinated amine molecules were positioned geoꢀ
metrically and refined using a riding model. The hydrogen atꢀ
oms of the hydrate molecules, alcohol solvent molecules, and
pivalate anions (due to disorder, the occupancies of some of
the solvent molecules substantially differ from unity) were not
located (or positioned geometrically). The atoms of the solvent
molecules were refined isotropically. For the structure of
7•HOOCBut•MeOH, the hydrogen atoms of the tertꢀbutyl
substituents of the pivalate ligands and the aromatic rings of the
coordinated amine molecules were positioned geometrically
and refined using a riding model; the protons of the methanol
solvent molecules were not located.
The structures of all complexes were solved by direct methꢀ
ods and refined by the fullꢀmatrix leastꢀsquares method with
anisotropic displacement parameters for all nonhydrogen atꢀ
oms. The hydrogen atoms of the tertꢀbutyl substituents of the
pivalate ligands and the aromatic rings of the coordinated amine
molecules were positioned geometrically and refined using a
riding model. The calculations were carried out with the use of
the SHELX97 program package.34,35
The rather high R factors for both structures are attributed
also to the partial disorder of the pivalate ligands associated with
''rotation'' of the tertꢀbutyl groups about the C—But bonds, as
evidenced by the abnormally high anisotropic temperature facꢀ
tors for the C atoms of the methyl groups.
2
cular structure of [Co4(µ ꢀOMe)4(µ ꢀOOCBut)2(η ꢀOOCBut)2ꢀ
(MeOH)4]•4MeOH det3ermined ea2rlier by Xꢀray diffraction.11
Tetra(µ ꢀmethoxo)bis(µ ꢀO,O´ꢀtrimethylacetato)bisꢀ
3
2
1
(µ ꢀO,O´ꢀtrimethylacetato)tetra(η ꢀmethanol)tetranickel(II)
2
methanol tetrasolvate, [Ni4(µ ꢀOMe)4(µ ꢀOOCBut)2(η ꢀOOꢀ
2
CBut)2(MeOH)4]•4MeOH (9•4MeOH).2 Methanol (40 mL)
3
was added to the complex [Ni4(µ ꢀOH)2(µ ꢀOOCBut)4ꢀ
3
2
2
(η ꢀOOCBut)2(EtOH)4]•2EtOH (0.3 g, 0.26 mmol), and the
mixture was stirred under argon at 60 °C until complete dissoluꢀ
tion of the starting compound. The green solution was filtered
and concentrated at 0.1 Torr and 20 °C to 15—20 mL. Green
crystals that precipitated after 12 h were separated by decantaꢀ
tion, washed with cold methanol and hexane, and dried under
argon. The yield of the compound 9•4MeOH was 0.297 g (76%).
Found (%): C, 37.65; H, 7.85; N, 0.00. C32H80Ni4O20. Calcuꢀ
lated (%): C, 37.69; H, 7.89; N, 0.00. IR, ν/cm–1: 3388 s,
3268 m, 2956 s, 2928 s, 2908 m, 2876 s, 2828 m, 1684 m, 1668 m,
1564 s, 1552 s, 1536 s, 1512 m, 1484 s, 1456 m, 1416 s, 1372 s,
1360 m, 1260 w, 1224 s, 1100 w, 1044 s, 936 w, 880 m, 796 s, 604 m,
556 m, 452 s, 412 m, 324 w. The crystals obtained were studied
by Xꢀray diffraction. The crystallographic parameters for
the compound 9•4MeOH (space group Pbca, a = 15.327(11) Å,
b = 41.83(3) Å, c = 15.887(9) Å, α = 90°, β = 90°, γ = 90°,
V = 10186(11) Å3, Z = 8) correspond to those of the moleꢀ
2
cular structure of [Ni4(µ ꢀOMe)4(µ ꢀOOCBut)2(η ꢀOOCBut)2ꢀ
3
2
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos 07ꢀ03ꢀ00408,
07ꢀ03ꢀ00707, 08ꢀ03ꢀ00365, and 08ꢀ03ꢀ00343), the Diviꢀ
sion of Chemistry and Materials Science of the Russian
Academy of Sciences (Program ''Chemistry and Physical
(MeOH)4]•4MeOH established earlier by Xꢀray diffraction.5
Xꢀray diffraction study. Xꢀray diffraction data for complexes
3, 4, and 6—9 were measured on an automated Bruker AXS
SMART 1000 diffractometer (graphite monochromator, 120(2) K,
ωꢀscanning technique with a step of 0.3° and exposure

20
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Fomina et al.
19. T. B. Mikhailova, I. G. Fomina, A. A. Sidorov, I. F.
Golovaneva, G. G. Aleksandrov, V. N. Ikorskii, V. M.
Novotortsev, I. L. Eremenko, Zh. Neorg. Khim., 2003, 48,
1648 [Russ. J. Inorg. Chem. (Engl. Transl.), 2003, 48, 1505].
20. M. Halcrow, J. S. Sun, J. C. Huffman, G. Christou, Inorg.
Chem., 1995, 34, 4167.
Chemistry of Supramolecular Systems and Atomic Clusꢀ
ters''), the Presidium of the Russian Academy of Sciences
(Programs ''Molecular Design of Magnetoactive Comꢀ
pounds and Materials (Molecular Magnets)'' and ''Polyꢀ
functional Materials for Molecular Electronics''), the
Council on Grants of the President of the Russian Federaꢀ
tion (Program for State Support of Leading Scientific Schools
of the Russian Federation, Grant NShꢀ1518.2008.03),
and the Federal Agency for Science and Innovations of
the Russian Federation
21. V. Tangoulis, C. P. Raptopopoulu, S. Paschalidou, A. E.
Tsohos, Inorg. Chem., 1997, 3, 5270.
22. W. Bidell, V. Shklover, H. Berke, Inorg. Chem., 1992, 31, 5561.
23. M. A. Yampol´skaya, G. S. Matuzenko, N. V. Gerbeleu,
Yu. A. Simonov, A. A. Dvorkin, Zh. Neorg. Khim., 1989, 34,
681 [J. Inorg. Chem. USSR (Engl. Transl.), 1989, 34].
24. T. M. AbdelꢀFattah, G. Davies, B. V. Romanovsky, O. L.
Shakhnovskaya, A. M. Larin, S. A. Jansen, M. J. Palmieri,
Catal. Today, 1996, 89, 670.
References
1. J. A. Bertrand, T. C. Hightower, Inorg. Chem., 1973, 12, 206.
2. W. L. Gladfelter, M. W. Lynch, W. P. Schaefer, D. N.
Hendrickson, H. B. Gray, Inorg. Chem., 1981, 20, 2390.
3. T. O. Denisova, M. A. Golubnichaya, S. E. Nefedov, Izv.
Akad. Nauk, Ser. Khim., 2003, 2612 [Russ. Chem. Bull., Int.
Ed., 2003, 52, 2760].
25. I. G. Fomina, G. G. Aleksandrov, Zh. V. Dobrokhotova,
O. Yu. Proshenkina, M. A. Kiskin, Yu. A. Velikodnyi, V. N.
Ikorskii, V. M. Novotortsev, I. L. Eremenko, Izv. Akad.
Nauk, Ser. Khim., 2006, 1841 [Russ. Chem. Bull., Int. Ed.,
2006, 55, 1909].
26. T. B. Mikhailova, A. E. Malkov, A. A. Sidorov, I. G. Fomina,
G. G. Aleksandrov, I. F. Golovaneva, V. M. Dem´yanovich,
V. M. Novotortsev, V. N. Ikorskii, I. L. Eremenko, Zh.
Neorg. Khim., 2002, 47, 1829 [Russ. J. Inorg. Chem. (Engl.
Transl.), 2002, 47, 1680].
27. M. A. Kiskin, G. G. Aleksandrov, Zh. V. Dobrokhotova,
V. M. Novotortsev, Yu. G. Shvedenkov, I. L. Eremenko,
Izv. Akad. Nauk, Ser. Khim., 2006, 779 [Russ. Chem. Bull.,
Int. Ed., 2006, 55, 806].
28. M. A. Golubnichaya, A. A. Sidorov, I. G. Fomina, M. O.
Ponina, S. M. Deomidov, S. E. Nefedov, I. L. Eremenko,
I. I. Moiseev, Izv. Akad. Nauk, Ser. Khim., 1999, 1773 [Russ.
Chem. Bull. (Engl. Transl.), 1999, 48, 1751].
4. K. Dimitrou, A. D. Brown, K. Folting, G. Christou, Inorg.
Chem., 1999, 38, 1834.
5. G. Chaboussant, R. Basler, H.ꢀU. Gudel, S. T. Ochsenbein,
A. Parkin, S. Parsons, G. Rajaraman, A. Sieber, A. A. Smith,
G. A. Timco, R. E. P. Winpenny, Dalton Trans., 2004, 2758.
6. H. Zhao, J. Bacsa, K. R. Dunbar, Acta Crystallogr., Sect. E:
Struct. Rep. Online, 2004, 60, m637.
7. K. Dimitrou, J.ꢀS. Sun, K. Folting, G. Christou, Inorg.
Chem., 1995, 34, 4160.
8. V. G. Kessler, S. G. Gohil, M. Kritikos, O. N. Korsak, E. E.
Knyazeva, I. F. Moskovskaya, B. V. Romanovsky, Polyhedron,
2001, 20, 915.
9. J. K. Beattie, T. W. Hambley, J. A. Klepetko, A. F. Masters,
P. Turner, Polyhedron, 1997, 16, 2109.
10. K. Dimitrou, A. D. Brown, T. E. Concolino, A. L. Rheingold,
G. Christou, Chem. Commun., 2001, 1284.
11. G. Aromí, A. S. Batsanov, P. Christian, M. Helliwell,
A. Parkin, S. Parsons, A. A. Smith, G. A. Timco, R. E. P.
Winpenny, Chem. Eur. J., 2003, 9, 5142.
12. G. Aromí, A. S. Batsanov, P. Christian, M. Helliwell,
O. Roubeau, G. A. Timco, R. E. P. Winpenny, Dalton Trans.,
2003, 4466.
29. Zh. V. Dobrokhotova, I. G. Fomina, M. A. Kiskin, A. A.
Sidorov, I. L. Eremenko, Izv. Akad. Nauk, Ser. Khim., 2006,
250 [Russ. Chem. Bull., Int. Ed., 2006, 55, 256].
30. I. G. Fomina, Zh. V. Dobrokhotova, M. A. Kiskin, G. G.
Aleksandrov, O. Yu. Proshenkina, A. L. Emelina, V. N.
Ikorskii, V. M. Novotortsev, I. L. Eremenko, Izv. Akad.
Nauk, Ser. Khim., 2007, 1650 [Russ. Chem. Bull., Int. Ed.,
2007, 56, 1712].
31. I. G. Fomina, Zh. V. Dobrokhotova, G. G. Aleksandrov,
M. A. Kiskin, M. A. Bykov, V. N. Ikorskii, V. M. Novotortsev,
I. L. Eremenko, Izv. Akad. Nauk, Ser. Khim., 2007, 1660
[Russ. Chem. Bull., Int. Ed., 2007, 56, 1722].
13. J. K. Beattie, T. W. Hambley, J. A. Klepetko, A. F. Masters,
P. Turner, Polyhedron, 17, 1343.
14. K. Dimitrou, K. Folting, W. E. Streib, G. Christou, J. Am.
Chem. Soc., 1993, 115, 6432.
15. V. A. Ivanov, T. G. Aminov, V. M. Novotortsev, V. T.
Kalinnikov, Izv. Akad. Nauk, Ser. Khim., 2004, 2255 [Russ.
Chem. Bull., Int. Ed., 2004, 53, 2357].
16. I. G. Fomina, A. A. Sidorov, G. G. Aleksandrov, T. B.
Mikhailova, E. V. Pakhmutova, V. N. Ikorskii, V. M.
Novotortsev, I. L. Eremenko, Izv. Akad. Nauk, Ser. Khim.,
2004, 1422 [Russ. Chem. Bull., Int. Ed., 2004, 53, 1477].
17. A. E. Malkov, I. G. Fomina, A. A. Sidorov, G. G. Aleksandrov,
I. M. Egorov, N. I. Latosh, O. N. Chupakhin, G. L. Rusinov,
Yu. V. Rakitin, V. M. Novotortsev, V. N. Ikorskii, I. L.
Eremenko, I. I. Moiseev, J. Mol. Struct., 2003, 1—3, 207.
18. A. E. Malkov, I. G. Fomina, A. A. Sidorov, G. G. Aleksandrov,
V. N. Ikorskii, I. L. Eremenko, V. M. Novotortsev, Izv.
Akad. Nauk, Ser. Khim., 2003, 489 [Russ. Chem. Bull., Int.
Ed., 2003, 52, 513].
32. A. A. Sidorov, I. G. Fomina, S. S. Talismanov, G. G.
Aleksandrov, V. M. Novotortsev, S. E. Nefedov, I. L. Eremenko,
Koord. Khim., 2001, 27, 584 [Russ. J. Coord. Chem. (Engl.
Transl.), 2001, 27].
33. SMART (Control) and SAINT (Integration) Software, Version
5.0, Bruker AXS Inc., Madison, WI, 1997.
34. G. M. Sheldrick, SADABS, Program for Scanning and Correcꢀ
tion of Area Detector Data, Göttingen University, Göttinngen,
Germany, 1997.
35. G.M. Sheldrick, SHELX97, Program for the Solution of Crystal
Structures, Göttingen University, Göttingen, Germany, 1997.
Received May 16, 2008;
in revised form September 24, 2008