Polynuclear NiII and CoII hexafluoroacetylacetonates

Article abstract of DOI:10.1007/s11172-018-2202-8

Hydrolysis of [M₄(hfac)₄(MeO)₄(MeOH)₄] (М = Сo, Ni and hfac is hexafluoroacetylaceton ate) is a convenient way of obtaining polynuclear complexes [Ni₇(hfac)₆(OH)₈(H₂O)₆]?2H₂O, [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₈]?2H₂O?2MePh, [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₄(Me₂CO)₄]?3PhMe, and [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₆(Me₂CO)₂]?2H₂O?2Me₂CO, whose structures were confirmed by X-ray analysis.

Full text of DOI:10.1007/s11172-018-2202-8

Russian Chemical Bulletin, International Edition, Vol. 67, No. 7, pp. 1202—1205, July, 2018
1202
Polynuclear NiII and CoII hexafluoroacetylacetonates
O. V. Kuznetsova,a E. Yu. Fursova,a G. A. Letyagin,a,b G. V. Romanenko,a and V. I. Ovcharenkoa
aInternational Tomography Center, Russian Academy of Sciences,
3A ul. Institutskaya, 630090 Novosibirsk, Russian Federation.
E-mail: olya@tomo.nsc.ru
bNovosibirsk State University,
2 ul. Pirogova, 630090 Novosibirsk, Russian Federation
Hydrolysis of [M4(hfac)4(MeO)4(MeOH)4] (М = Сo, Ni and hfac is hexafluoroacetylacet-
onate) is a convenient way of obtaining polynuclear complexes [Ni7(hfac)6(OH)8(H2O)6]•2H2O,
[Co12(hfac)10(OH)14(H2O)8]•2H2O•2MePh, [Co12(hfac)10(OH)14(H2O)4(Me2CO)4]•3PhMe,
and [Co12(hfac)10(OH)14(H2O)6(Me2CO)2]•2H2O•2Me2CO, whose structures were confirmed
by X-ray analysis.
Key words: nickel(II), cobalt(II), polynuclear compounds, hexafluoroacetylacetonate, hydro-
lysis, X-ray analysis.
Mononuclear bis-chelates based on the first-row tran-
synthesis and the structures of the obtained polynuclear
complexes.
sition metal hexafluoroacetylacetonates [M(hfac)2] are
strong acceptors, which can coordinate various ligands.1
Their partial solvolysis, for example, alcoholysis is an ef-
ficient method for transition to polynuclear acceptors,
which can serve as valuable blocks in chemical design of
various functional materials.2,3 However, there is no gen-
eral approach to synthesis of such polynuclear acceptors;
there are only a few described examples of obtaining such
compounds.4,5 The recently reported synthesis yielded
tetranuclear complex [Ni4(hfac)4(MeO)4(MeOH)4] (1),
the treatment of which with Py gave complex
[Ni7(hfac)6(OH)8(Py)6] (2).6 We modified the described
technique for synthesis of 1 and showed that the given
tetranuclear compound can be converted into heptanuclear
complex [Ni7(hfac)6(OH)8(H2O)6]•2H2O (3) via heating
under reflux in toluene. It was also shown that there is
a full structural analog of complex 1, namely tetranuclear
complex [Co4(hfac)4(MeO)4(MeOH)4] (4), which under
the conditions of synthesis of complex 3 is converted into
the complex [Co12(hfac)10(OH)14(H2O)8]•2H2O•2MePh
(5). Since the latter was always isolated with an admixture
of [Co(hfac)2(H2O)2] (6), it was purified by recrystalliza-
tion from mixed solvents. Meanwhile, the individual do-
decanuclear complex was isolated as large crystals, which,
in the presence of impurity products, could be easily isol-
ated by mechanical means. It was noteworthy that the
composition of the coordination sphere and solvent mol-
ecules in [Co12(hfac)10(OH)14(H2O)4(Me2CO)4]•3PhMe (7)
or [Co12(hfac)10(OH)14(H2O)6(Me2CO)2]•2H2O•
•2Me2CO (8) depended on the composition of the mother
liquor used for recrystallization of the dodecanuclear
complex. In this report, we describe the conditions of
Experimental
Synthesis of hexakis(1,1,1,5,5,5-hexafluoro-2,4-pentanedi-
onate-O,O´)octa(μ3-hydroxo)hexaaquaheptanickel(II) dihydrate,
[Ni7(hfac)6(OH)8(H2O)6]•2H2O (3). Complex 1 (0.1 g,
0.076 mmol) was dissolved in toluene (6 mL) and the obtained
solution was refluxed for 1 h. Then it was cooled to room tem-
perature and filtered. The mother liquor was allowed to stand at
room temperature in an open flask. In 5—7 days, green pris-
matic crystals of complex 3 were filtered off, washed with toluene,
and dried with air flow. Yield 0.032 g (45%). The elemental
analysis data corresponded to loss of four water molecules. Found (%):
C, 19.8; H, 1.6; F, 36.7. C30H22F36Ni7O24. Calculated (%):
C, 19.4; H, 1.2; F, 36.7. In some experiments, as an admixture
to the major product, thin needle-like green crystals of
[Ni(hfac)2(H2O)2] were formed in the solid phase. The latter
were mechanically separated. If complex 1 was allowed to stand
in a vacuum chamber for 24 h at room temperature prior to reflux,
complex 3 was found to crystallize from toluene solution in a yield
of ~40% free of [Ni(hfac)2(H2O)2] impurity.
Synthesis of tetrakis(1,1,1,5,5,5-hexafluoro-2,4-pentane-
dionate-O,O´)tetra(3-methoxy)tetramethanoltetracobalt(II),
[Co4(hfac)4(MeO)4(MeOH)4] (4). To a solution of complex 6
(0.5 g, 0.98 mmol) in MeOH (5 mL), a solution of KOH (0.038 g,
0.69 mmol) in MeOH (10 mL) was added dropwise under vigor-
ous stirring. The obtained solution was filtered and allowed to
stand in an open flask for several days, and then red prismatic
crystals of complex 4 were filtered off. The highest yield (60%)
of the product was achieved at the Co(hfac)2(H2O)2 : KOH
molar ratio of 1 : 0.7. The elemental analysis data reproducibly
corresponded to loss of one MeOH molecule. Found (%): C, 25.7;
H, 1.9; F, 35.8. C27H28F24Co4O15. Calculated (%): C, 25.3;
H, 2.2; F, 35.5. Upon further storage, the complex [KCo(hfac)3]
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1202—1205, July, 2018.
1066-5285/18/6707-1202 © 2018 Springer Science+Business Media, Inc.

Polynuclear NiII and CoII hexafluoroacetylacetonates Russ. Chem. Bull., Int. Ed., Vol. 67, No. 7, July, 2018
1203
crystallized from the mother liquor as orange elongated plates
in a yield of ~40%. Found (%): C, 25.5; H, 0.8; F, 47.5.
C15H3F18CoKO6. Calculated (%): C, 25.0; H, 0.4; F, 47.5.
Synthesis of decakis(1,1,1,5,5,5-hexafluoro-2,4-pentanedi-
onate-O,O´)tetradeca(3-hydroxy)tetraaquatetrakis(propan-2-
(Rint = 0.0861), 2913 reflections with I > 2(I), 371 refined pa-
rameters, GOOF = 0.950, R1 = 0.0536, wR2 = 0.1326 (I > 2(I)).
Complex [Co12(hfac)10(OH)14(H2O)8]•2H2O•2MePh (5).
C64H58Co12F60O44, FW = 3378.26, T = 295 K, P21/n, a =
= 14.7615(10), b = 23.1418(16), c = 17.9980(12) Å,  = 98.061(5),
V = 6087.5(7) Å3, Z = 2, dcalc = 1.843 g cm–3, 55031 measured
reflections (max = 28.369), including 15080 unique reflections
(Rint = 0.0733), 5698 reflections with I > 2(I), 871 refined pa-
rameters, GOOF = 1.017, R1 = 0.0635, wR2 = 0.1301 (I > 2(I)).
Complex [Co12(hfac)10(OH)14(H2O)4(Me2CO)4]•3MePh
(7). C83H80Co12F60O42, FW = 3596.63, T = 240 K, P21/с,
a = 16.6465(8), b = 23.3770(11), c = 18.1141(9) Å,  = 108.413(3),
V = 6688.1(6) Å3, Z = 2, dcalc = 1.786 g cm–3, 78139 measured
reflections (max = 67.703), including 12003 unique reflections
(Rint = 0.0909), 7845 reflections with I > 2(I), 1034 refined
parameters, GOOF = 1.019, R1 = 0.0521, wR2 = 0.1164 (I > 2(I)).
Complex [Co12(hfac)10(OH)14(H2O)6(Me2CO)2]•2H2O•
•2Me2CO (8). C62H64Co12F60O46, FW = 3392.29, T = 240 K,
P21/с, a = 17.2810(7), b = 23.0619(9), c = 16.9170(7) Å,
one)dodecacobalt(II) tris(toluene) solvate, [Co12(hfac)10(OH)14
-
(H2O)4(Me2CO)4]•3MePh (7), and decakis(1,1,1,5,5,5-hexa-
fluoro-2,4-pentanedionate-O,O´)tetradeca(3-hydroxy)hexaaqua-
bis(propan-2-one)dodecacobalt(II) dihydrate bis(acetone) solvate,
[Co12(hfac)10(OH)14(H2O)6(Me2CO)2]•2H2O•2Me2CO (8).
Complex 4 (0.07 g, 0.053 mmol) was refluxed in toluene (7 mL)
for 1 h. Then the solution was cooled to room temperature, fil-
tered, and allowed to stand in an open flask for 2—3 days result-
ing in the formation of a difficult-to-separate mixture of red
prismatic crystals of complex 5 and crystals of complex 6. The
crystals of complex 5 for X-ray analysis were mechanically se-
lected. Upon recrystallization of the reaction products from
a toluene—acetone—CH2Cl2 mixture, complex 7 was isolated as
red prismatic crystals. Yield 0.016 g (25%). The elemental analy-
sis data corresponded to loss of three toluene molecules and four
acetone molecules. Found (%): C, 19.4; H, 1.04; F, 34.8.
C50H32F60Co12O38. Calculated (%): C, 19.4; H, 1.0; F, 36.9.
Upon recrystallization of the reaction products from a toluene—
acetone mixture, rather large crystals of complex 8 were iso-
lated. The elemental analysis data corresponded to loss of
two acetone molecules. Found (%): C, 20.6; H, 1.7; F, 33.7.
C56H52F60Co12O44. Calculated (%): C, 20.5; H, 1.6; F, 34.8.
X-ray analysis. The X-ray diffraction experiments were carried
out using the automated diffractometers: SMART APEX II
equipped with a Helix low-temperature unit (Oxford Cryosystem)
and Apex Duo equipped with a Cobra low-temperature unit. The
structures were solved by direct methods and refined with full-
matrix least squares in anisotropic approximation for all non-
hydrogen atoms. The positions of Н atoms were calculated
geometrically and refined using a riding model. All the calcula-
tions for the structure solution and refinement were carried out
using Bruker Shelxtl Version 6.14 and SHELXL7 complex soft-
ware. The crystallographic characteristics of compounds and
experimental details are given in Tables 1 and 2. The CIF files
containing the full information for the studied structures were
deposited with the Cambridge Crystallographic Database Centre
(CCDC 1835807-1835812) in website www.ccdc.cam.ac.uk/
data_reguest/cif.
 = 116.8876(18), V = 6013.1(4) Å3, Z = 2, dcalc = 1.874 g cm–3
,
56932 measured reflections (max = 67.753), including 10828
unique reflections (Rint = 0.0585), 8131 reflections with I > 2(I),
1116 refined parameters, GOOF = 1.004, R1 = 0.0377, wR2
= 0.0891 (I > 2(I)).
=
Results and Discussion
As was noted in the introduction, partial solvolysis of
[M(hfac)2] can serve as an efficient method for the syn-
thesis of polynuclear complexes, which , in turn, can serve
as the valuable blocks in chemical design of various func-
tional materials. However, only a few examples of obtain-
ing such compounds have been described so far. Thus,
there was a recent report on the synthesis of tetranuclear
complex 1 with the metal-oxygen cubane-like core
{Ni4O4}, which was formed by refluxing a mixture of
[Ni(hfac)2(H2O)2] with alkali for several hours. Thermal
treatment of the compound in vacuum followed by recrys-
tallization from diethyl ether with addition of Py resulted
in formation of heptanuclear complex 2•Py, the metal
core of which already comprises two vertex-sharing cubane
moieties.6
We found that the synthesis of complex 1 should be
carried out a room temperature, because heating under
reflux activates hydrolysis, resulting in formation of nickel
hydroxide as an impurity. A similar technique was found
to be suitable for the synthesis of complex 4, which is
isostructural with complex 1. However, upon isolation of
complex 4 from the mother liquor, formation of solid phase
begins from [KCo(hfac)3], which is isostructural with
earlier described [KNi(hfac)3].8
Complex [Ni7(hfac)6(OH)8(H2O)6]•2H2O (3). C30H30F36Ni7O28,
FW = 1933.51, T = 295 K, R-3, a = 21.3176(7), b = 21.3176(7),
c = 11.8546(5) Å, V = 4665.5(4) Å3, Z = 3, dcalc = 2.065 g cm–3
,
9763 measured reflections (max = 28.295), including 2577
unique reflections (Rint = 0.0565), 1454 reflections with I > 2(I),
229 refined parameters, GOOF = 0.923, R1 = 0.0368, wR2
= 0.0795 (I > 2(I)).
=
Complex [Co4(hfac)4(MeO)4(MeOH)4] (4). C28H32Co4F24O16
,
FW = 1316.26, T = 240 K, C2/c, a = 35.7506(19), b = 13.0850(7),
c = 24.4252(14) Å,  = 120.576(3), V = 9837.3(9) Å3, Z = 8,
dcalc = 1.777 g cm–3, 78475 measured reflections (max = 28.460),
including 12180 unique reflections (Rint = 0.1044), 4620 reflec-
tions with I > 2(I), 824 refined parameters, GOOF = 0.696,
R1 = 0.0395, wR2 = 0.0840 (I > 2(I)).
Complex [KCo(hfac)3]. C15H3CoF18KO6, FW = 719.20,
T = 295 K, P3c, a = 17.6676(4), b = 17.6676(4), c = 13.9492(7) Å,
V = 3770.8(3) Å3, Z = 6, dcalc = 1.900 g cm–3, 16909 measured
reflections (max = 67.827), including 4414 unique reflections
Heating of the toluene solution of complex 1 under
reflux in contact with air was shown to produce a relatively
high yield of heptanuclear complex 3. Meanwhile, heating
of complex 4 under reflux in toluene yields a difficult-to-
separate mixture of dodecanuclear complex 5 and com-
pound 6. Recrystallization of a mixture of these products

1204 Russ. Chem. Bull., Int. Ed., Vol. 67, No. 7, July, 2018
Kuznetsova et al.
from a toluene solution in the presence of CH2Cl2 and
acetone or from toluene in the presence of acetone
gave relatively large crystals of complexes 7 or 8, res-
pectively. We managed to grow single crystals for all
the synthesized compounds, determine their molecular
and crystal structures, and establish the structure of their
metal cores.
a
In a molecule of complex 4, each metal atom is bonded
to two O atoms of hfac ligands having bidentate chelating
coordination and three O atoms of bridging MeO– anions
linking each metal ion to three other ones in a tetra-
nuclear moiety (Fig. 1, a). The metal environment is
completed to a distorted octahedron by O atoms of MeOH
molecules in monodentate coordination. The Co—O and
Co—Co distances are within the relatively narrow ranges:
2.005(4)—2.129(5) Å and 3.033(1)—3.104(1) Å, respec-
tively (Table 1).
The structure of [KCo(hfac)3] is formed by polymeric
chains (Fig. 1, b), where all Ohfac atoms are bridging. The
K—O distances are 2.77(2)—2.80(1) Å; Co—O, 2.035(10)—
2.070(10) Å.
b
K(1)
Co(1)
In complex 3 (Fig. 2), all Ni atoms are bridged by OH
groups to form the metal-oxygen core {Ni7O8} as two
vertex-sharing cubane moieties. The environment of the
central Ni atom comprises only O atoms of hydroxyl
groups; other Ni atoms are surrounded by Ohfac atoms,
Fig. 1. Structure of molecular [Co4(hfac)4(MeO)4(MeOH)4] (4)
(a) and a chain fragment in [KCo(hfac)3] (b). Hereinafter,
H atoms and CF3 groups are omitted in the figures.
Fig. 2. Structure of complex [Ni7(hfac)6(OH)8(H2O)6]•2H2O (3). Dashed lines indicate H-bonds.
Table 1. M—O and M…M distances in the studied compounds
Formula
d/Å
M—O
M…M
[Ni7(hfac)6(OH)8(H2O)6]•2H2O (3)
[Co4(hfac)4(MeO)4(MeOH)4] (4)
[KCo(hfac)3]
2.020(3)—2.095(4)
2.005(4)—2.129(5)
2.77(2)—2.80(1)
(K—O)
3.0243(6)—3.0929(8)
3.086(1)—3.104(1)
3.472(6)—3.503(7)
(K—Co)
2.035(10)—2.070(10)
(Co—O)
2.024(3)—2.221(4),
2.297(3)
2.008(3)—2.189(3),
2.316(3)
2.021(2)—2.213(2),
2.266(2)
[Co12(hfac)10(OH)14(H2O)8)]•2H2O•2MePh (5)
[Co12(hfac)10(OH)14(H2O)4(Me2CO)4]•3PhMe(7)
[Co12(hfac)10(OH)14(H2O)6(Me2CO)2]•2H2O•2Me2CO (8)
3.002(1)—3.067(1)
3.0348(9)—3.0878(8)
3.0141(7)—3.1054(7)

Polynuclear NiII and CoII hexafluoroacetylacetonates Russ. Chem. Bull., Int. Ed., Vol. 67, No. 7, July, 2018
1205
OH, and H2O. The outer-sphere H2O molecules form
numerous H-bonds with coordinated H2O molecules and
Ohfac atoms giving rise to columns running along [001]
direction in the structure of complex 3 (Fig. 2).
a
Co(2)
Co(3)
Co(6)
In dodecanuclear CoII complexes (Fig. 3), the central
part of the metal core {Co12O16} comprises two face-
sharing cubes, to which two cubane moieties are attached.
The environment of all Co atoms is a slightly distorted
octahedron, except for Co atoms arranged on the shared
face. The octahedron of these atoms is noticeably distorted:
one Co—O distance (2.266(2), 2.297(3), and 2.316(3) Å)
is longer than others (2.021(2)—2.213(2), 2.024(3)—
2.221(4), and 2.008(3)—2.189(3) Å, respectively). The
major structural difference between these complexes is the
ratio of H2O to acetone molecules.
Co(1)
Co(5)
Co(4)
Therefore, we managed to synthesize new polynuclear
NiII and СoII hydroxohexafluoroacetylacetonates and to
demonstrate by X-ray analysis that the major structure-
forming unit of these compounds is the metal-oxygen
cubane-like core {M4O4}.
This study was financially supported by the Russian
Science Foundation (Project No. 17-13-01022), the Coun-
cil on Grants at the President of the Russian Federation
(Program for State Support of Young Scientists, Project
МК-5027.2018.3), and the Federal Agency for Scientific
Organizations.
b
Co(6)
Co(2)
Co(3)
Co(4)
Co(1)
Co(5)
References
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Co(1)
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Co(6)
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Co(2)
Co(5)
Fig. 3.Molecular structures of [Co12(hfac)10(OH)14(H2O)8] (a),
[Co12(hfac)10(OH)14(H2O)4(Me2CO)4] (b), and [Co12(hfac)10
(OH)14(H2O)6(Me2CO)2] (c).
-
Received April 13, 2018;
accepted April 25, 2018