Synthesis and Structure of New Polymeric Lithium Pivalates

Article abstract of DOI:10.1134/S1070328420020104

Abstract: Data on the synthesis and study of the crystal structure of [Li₁₀(Piv)₁₀(MeCN)₂]_n (I) and [Li₆(Piv)₆(MeCN)₂]_n (II) are presented. According to X-ray diffract

Full text of DOI:10.1134/S1070328420020104

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2020, Vol. 46, No. 2, pp. 75–80. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Koordinatsionnaya Khimiya, 2020, Vol. 46, No. 2, pp. 67–72.
Synthesis and Structure of New Polymeric Lithium Pivalates
E. N. Zorina-Tikhonovaa, D. S. Yambulatova, M. A. Kiskina, E. S. Bazhinaa, S. A. Nikolaevskiia, *,
N. V. Gogolevaa, I. A. Lutsenkoa, A. A. Sidorova, and I. L. Eremenkoa
aKurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
*e-mail: sanikol@igic.ras.ru
Received September 27, 2019; revised September 29, 2019; accepted September 30, 2019
Abstract—Data on the synthesis and study of the crystal structure of [Li10(Piv)10(MeCN)2]n (I) and
[Li6(Piv)6(MeCN)2]n (II) are presented. According to X-ray diffraction data (CIF files CCDC nos. 1957855
(I); 1955569 (II)), compounds I and II are 1D polymers composed of deca- and hexanuclear fragments,
respectively, in which the lithium atoms are linked to one another by μ3- and μ4-bridging pivalate anions.
Keywords: lithium, trimethylacetate, carboxylate complexes, X-ray diffraction
DOI: 10.1134/S1070328420020104
INTRODUCTION
of publication of these data, the Ar-bian sodium salts
have been widely used as the starting reagents for more
than 13 years. The crystal structure and magnetic
behavior of sodium and potassium semiquinolates and
sodium catecholate, which have a much longer history
of laboratory use, were reported only in 2018 [22].
Inorganic, organometallic, and coordination com-
pounds of lithium occupy an important place in mod-
ern chemistry and materials sciences. They are valu-
able starting compounds for the synthesis of more
complex molecules, key intermediates of various pro-
cesses, and components of functional materials used
in various fields of technology. Lithium carboxylates
are used for the synthesis of heterometallic complexes
in which they are linked to 3d metal atoms and to each
other by bridging carboxylate groups [1–7]. By varia-
tion of additional ligands, it is possible to obtain both
oligo- and polynuclear and polymeric heterometallic
complexes, including metal-organic frameworks, pos-
sessing nontrivial redox [8], magnetic [9, 10], and
sorption properties [11, 12] and functioning as precur-
sors of complex oxides for the manufacture anode
materials [13–15] and high-capacity storage batteries
[16–18]. The formation of intramolecular ionic Li–O
bonds can serve to fabricate heterometallic com-
pounds, which are nonsensitive to excess chelating
ligands, as opposed to accessibility of readily available
starting compounds is a key issue both for fundamen-
tal research aimed at the synthesis of more complex
molecules and for the manufacture of materials pos-
sessing valuable functional properties. It is paradoxical
that the structure and properties of some valuable
chemicals that have been routinely used in synthesis
for several decades do not attract attention of scientific
community and, therefore, remain unknown. As
examples illustrating this statement, consider two
cases belonging to the chemistry of redox active com-
plexes. Data on the structure of crystalline phases of
the sodium salts of bis(N-arylamino)acenaphthene
ligands (Ar-bian) and preparative procedures for their
Here we report the procedure for the synthesis and
data on the structure of lithium pivalate, which is a
valuable initial reagent in the synthesis of heterometal-
lic carboxylate architectures possessing broad struc-
tural diversity and nontrivial physicochemical proper-
ties.
EXPERIMENTAL
All operations on the synthesis of lithium pivalate
were performed in air using commercially available
LiOH · H2O, pivalic acid, hexane, acetonitrile, and
THF.
The ATR IR spectra of the compound were mea-
sured in the 400–4000 cm–1 range on a PerkinElmer
Spectrum 65 spectrophotometer equipped with the
Quest ATR Accessory attachment (Specac). Elemen-
tal analysis was carried out on a EuroEA-3000
C,H,N,S-analyzer (EuroVector).
Synthesis of Li(Piv). A weighed amount of LiOH ·
H2O (5.5 g, 0.13 mol) was dissolved in distilled water
(20 mL) on boiling. An equimolar amount of crystal-
line pivalic acid was added to the obtained solution,
the mixture was stirred and heated at 140°C until water
completely evaporated. The product was cooled down
synthesis were published only in 2003 [21]. By the time to room temperature, washed with hexane, and dried
75

76
ZORINA-TIKHONOVA et al.
in air to a constant weight. The yield was 12.4 g (88%
based on LiOH · H2O).
RESULTS AND DISCUSSION
Lithium pivalate is obtained by neutralization reac-
tion between a solution of lithium hydroxide and
trimethylacetic acid. The use of water as a solvent for
LiOH enables uniform heating of the reaction mix-
ture. Maintenance of the temperature at 140°C pre-
vents removal of trimethylacetic acid from the reaction
mixture, but allows efficient removal of surplus water
after completion of the reaction. The single crystals of
[Li10(Piv)10(MeCN)2]n (I) suitable for X-ray diffrac-
tion were grown at room temperature from a THF–
acetonitrile mixture. Crystallization from acetonitrile
under solvothermal conditions in the absence of oxygen
afforded single crystals of [Li6(Piv)6(MeCN)2]n (II).
The infrared spectrum of compound II exhibits
intense characteristic absorption bands in the 1578–
1538 and 1422–1408 cm–1 ranges corresponding to
antisymmetric νas(COO) and symmetric νs(COO)
stretching vibrations of the coordinated carboxyl
groups of the bridging pivalate anions, respectively.
The bending vibrations δ(OCO) occur as two
medium-intensity bands at 805 and 795 cm–1. The
spectrum of compound II also exhibits a group of
bands at 1478, 1360, and 1224 cm–1, corresponding to
δas, δs, and γ modes of the geminal CH3 groups.
For C5H9O2Li
Anal. calcld., %
Found, %
C, 55.57
C, 55.29
H, 8.39
H, 8.44
IR (ATR; ν, cm–1): 2963 m, 2933 w, 2903 w, 2874 w,
1675 m, 1578 s, 1558 vs, 1538 vs, 1477 vs, 1462 m,
1423 vs, 1407 vs, 1377 s, 1359 vs, 1224 s, 1032 vw,
938 vw, 895 m, 806 m, 795 m, 597 s, 547 s, 435 vs,
428 vs, 415 vs.
The single crystals of [Li10(Piv)10(MeCN)2]n (I)
suitable for X-ray diffraction were grown by recrystal-
lization of the product Li(Piv) from a THF–acetoni-
trile mixture at room temperature.
For C54H96N2O20Li10
Anal. calcld., % C, 55.78
Found, % C, 56.10
H, 8.32
H, 8.51
N, 2.41
N, 2.73
The single crystals of [Li6(Piv)6(MeCN)2]n (II)
suitable for X-ray diffraction were grown by recrystal-
lization of the product Li(Piv) from acetonitrile under
solvothermal conditions.
According to X-ray diffraction data, compounds I
and II are 1D coordination polymers formed by inter-
connected deca- and hexanuclear moieties, respec-
tively. Compound I contains 10 non-equivalent lith-
ium atoms (Fig. 1). Six atoms form three trinuclear
moieties of similar structure (Li(1), Li(2), Li(5) and
Li(4), Li(6), Li(10)), which are connected to one
another by four pivalate anions, two of which are coor-
dinated in the μ4-bridging mode, while the other two
For C34H60N2O12Li6
Anal. calcld., % C, 55.90
Found, % C, 56.14
H, 8.28
H, 8.23
N, 3.83
N, 3.87
IR (ATR; ν, cm–1): 2961 w, 2931 vw, 2905 vw, 2872 vw,
1675 w, 1578 m, 1557 s, 1538 s, 1478 s, 1462 w, 1422 m, anions show μ3-bridging coordination. One O atom of
1408 m, 1377 m,1360 s, 1224 m, 1031 vw, 939 vw,
895 w, 805 m, 795 m, 598 m, 550 m, 450 s, 435 s,
419 vs.
each anion is coordinated to one Li atom of the trinu-
clear moiety, whereas the other O atom is coordinated
to all three lithium atoms of the second trinuclear
moiety (in the case of μ4-bridging anions) and to two
metal atoms (in the case of μ3-anions). The Li(3),
Li(7), Li(8), and Li(9) atoms form a tetranuclear frag-
ment. The Li(3) and Li(7) atoms have C.N. 5, whereas
the other metal sites have C.N. 4. In the case of Li(8)
and Li(9) atoms, one coordination site is occupied by
the N atom of N-coordinated acetonitrile molecule.
In the polymeric chain, a pair of trinuclear fragments
alternates with one tetranuclear fragment being bound
to it via three μ4-bridging pivalate anions (Fig. 2). The
key bond lengths are as follows: Li–O, 1.837(7)–
2.080(6) Å (for I) and 1.856(4)–2.064(4) Å (for II);
Li–N, 2.090(7)–2.128(8) Å (for I) and 2.041(4)–
2.057(4) Å (for II), and the Li···Li interatomic dis-
tances are 2.665(9)–2.943(8), 4.748(9)–4.924(9) Å
(for I) and 1.952(4)–2.856(5) Å, 4.498(5) Å (for II).
Single crystal X-ray diffraction study of complexes I
and II was performed on a Bruker SMART Apex II
diffractometer equipped with CCD detector (MoKα,
λ = 0.71073 Å, graphite monochromator) [23].
Semiempirical absorption correction was applied [24].
The structures were solved by direct methods and
refined in the full-matrix anisotropic approximation
for all non-hydrogen atoms. The hydrogen atoms at
the carbon atoms of organic ligands were generated
geometrically and refined using the riding model. The
calculations were carried out by the SHELX-97 soft-
ware package [25].
The crystallographic parameters of complexes I
and II are summarized in Table 1. The full set of X-ray
diffraction data is deposited with the Cambridge Crys-
tallographic Data Centre (CCDC nos. 1957855 (I);
Each hexanuclear fragment of compound II con-
or tains three pairs of crystallographically nonequivalent
lithium atoms (Fig. 3). In each of these fragments,
1955569
(II);
deposit@ccdc.cam.ac.uk
http://www.ccdc.cam.ac.uk/data_request/cif).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY
Vol. 46
No. 2
2020

SYNTHESIS AND STRUCTURE
77
Table 1. Crystallographic data and structure refinement details for I and II
Value
Parameter
I
II
Molecular formula
C54H96N2O20Li10
1162.73
C34H60N2O12Li6
730.48
M
T, K
150
296(2)
System
Space group
a, Å
b, Å
c, Å
Monoclinic
P21/n
Triclinic
P1
11.6781(8)
21.9413(14)
26.8663(2)
90
93.051(1)
90
12.1867(9)
12.2826(9)
16.0698(11)
107.760(2)
90.193(2)
103.271(2)
2222.6(3)
α, deg
β, deg
γ, deg
V, Å3
6874.3(8)
Z
4
2
ρ(calcd.), g/cm3
μ, mm–1
1.123
1.092
0.08
0.078
θ, deg
Tmin/Tmax
2.2–28.3
0.673/0.746
82590
20985
11189
2.26–26.37
0.653/0.746
22818
Number of measured reflections
Number of unique reflections
Number of reflections with I > 2σ(I)
Rint
9044
4458
0.0978
533
1.03
0.068
Number of refined parameters
GOOF
775
1.00
R1 (I > 2σ(I))
0.071
0.089
wR2 (I > 2σ(I))
0.218
0.190
Residual electron density (min/max), e/Å3
–0.76/1.37
–0.204/0.243
four central lithium atoms (Li(1), Li(2) and Li(5), and Li(5)) additionally coordinate one acetonitrile
molecule each.
Li(6)) are linked by six bridging pivalate anions, four
of which demonstrate μ4-bridging coordination (and
bind four metal atoms each) and the other two show
μ3-bridging coordination. Each anion of the first μ4-
bridging anion pair binds three central lithium atoms
only via coordination of one carboxyl O atom, whereas
the second carboxyl O atom links the central atoms to
a peripheral lithium atom (Li(3) or Li(4)) within the
hexanuclear fragment. Each of the two μ3-bridging
pivalate anions binds two central lithium atoms to one
peripheral atom. The second pair of μ4-bridging acid
anions connects two central lithium atoms to two
peripheral metal atoms, one of which belongs to the
neighboring hexanuclear fragment; as a result, single
fragments are connected into a polymeric chain
(Fig. 4). Two of the four central lithium atoms (Li(1)
It worth to note that the structures of both types of
lithium pivalate we found considerably differ from the
previously
characterized
potassium
pivalate
[K(Piv)(HPiv)(MeCN)]n, which contains both piva-
late anions and neutral trimethylacetic acid
molecules [26].
Thus, we developed a reliable preparative proce-
dure suitable for gram-scale synthesis of lithium piva-
late, which is a valuable initial reagent for the prepara-
tion of heterometallic carboxylate complexes and
Metal-Organic Frameworks. Variation of the crystal-
lization conditions of the obtained product allowed us
to isolate and structurally characterize two coordina-
tion
polymers,
[Li10(Piv)10(MeCN)2]n
and
[Li6(Piv)6(MeCN)2]n.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 46 No. 2 2020

78
ZORINA-TIKHONOVA et al.
N(1)
O(20)
Li(9)
O(13)
O(13)
O(10)
O(17)
O(11)
Li(5)
O(1)
Li(2)
O(16) O(19)
Li(10)
O(15)
O(7)
O(18)
O(10)
Li(6)
O(9)
Li(7)
Li(3)
O(6)
O(12)
O(3)
O(8)
O(3)
Li(8)
O(5)
O(4)
Li(4)
Li(1)
O(8)
O(2)
O(6)
O(9)
O(14)
N(2)
N(1)
Li(9)
O(20)
O(11)
O(13)
Li(5)
O(19)
O(13)
O(17)
O(7)
Li(10)
O(16)
O(1)
O(10)
O(8)
O(18)
Li(7)
O(10)
Li(4)
O(6)
O(9)
O(3)
Li(2)
O(15)
O(3)
O(9)
Li(3)
O(12)
Li(6)
O(4)
O(5)
O(6)
Li(1)
O(14)
Li(8)
O(8)
O(2)
N(2)
Fig. 1. Structure of the decanuclear fragment forming the polymeric chain of compound I. The methyl groups of the pivalate
anions and hydrogen atoms are omitted.
c
b
a
Li(9)
Li(9)
Li(9)
Li(7)
Li(4)
Li(10)
Li(4)
Li(5)
Li(1)
Li(2)
Li(3)
Li(10)
Li(6)
Li(2)
Li(3)
Li(7)
Li(7)
Li(5)
Li(3)
Li(8)
Li(1)
Li(6)
Li(8)
Li(8)
O
N
C
Li
Fig. 2. Fragment of the polymeric chain of compound I. The methyl groups of the pivalate anions and hydrogen atoms are omit-
ted.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY
Vol. 46
No. 2
2020

SYNTHESIS AND STRUCTURE
O(1)
79
Li(1)
N(1)
O(6)
Li(4)
O(2)
O(9)
O(11)
O(5)
Li(3)
Li(4)
O(6)
O(8)
O(7)
O(11)
O(3)
O(3)
Li(2)
O(4)
O(4)
Li(2)
O(5)
Li(3)
O(7)
O(2)
O(8)
O(9)
Li(1) N(1)
O(1)
N(2)
Li(5)
O(12)
O(9)
O(8)
O(4)
O(2)
O(7)
O(5)
Li(3)
O(11)
Li(4)
O(10)
O(6)
Li(6)
Li(4)
Li(6)
O(2)
O(4)
O(6)
O(10)
O(11)
O(9)
O(12)
O(5)
Li(3)
O(7)
O(8)
Li(5)
N(2)
Fig. 3. Structure of the two types of hexanuclear fragments forming the polymeric chain of compound II. The methyl groups of
the pivalate anions and hydrogen atoms are omitted.
b
a
Li(1)
c
Li(5)
Li(6)
Li(4)
Li(1)
Li(2)
Li(4)
Li(4)
Li(3)
Li(2)
Li(6)
Li(2)
Li(3)
Li(6)
Li(5)
Li(3)
Li(5)
Li(1)
Li
N
O
C
Fig. 4. Fragment of the polymeric chain of compound II. The methyl groups of the pivalate anions and hydrogen atoms are omitted.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 46 No. 2 2020

80
ZORINA-TIKHONOVA et al.
ACKNOWLEDGMENTS
11. Sapianik, A.A., Zorina-Tikhonova, E.N., Kis-
kin, M.A., et al., Inorg. Chem., 2017, vol. 56, p. 1599.
X-ray diffraction, IR spectroscopy, and elemental anal-
ysis were performed using Shared Experimental Facilities
supported by IGIC RAS State Assignment.
12. Sapianik, A.A., Kiskin, M.A., Kovalenko, K.A., et al.,
Dalton Trans., 2019, vol. 48, p. 3676.
13. Dobrokhotova, Zh., Emelina, A., Sidorov, A., et al.,
Polyhedron, 2011, vol. 30, p. 132.
FUNDING
14. Burkhardt, S.E., Bois, J., Tarascon, J.-M., et al., Chem.
Mater., 2013, vol. 25, p. 132.
This work was supported by the Russian Foundation for
Basic Research (project no. 18-29-04043).
15. Lutsenko, I.A., Kiskin, M.A., Aleksandrov, G.G.,
et al., Russ. Chem. Bull., Int. Ed. 2018, vol. 67, no. 3,
p. 449.
CONFLICT OF INTEREST
16. Bykov, M., Emelina, A., Kiskin, M., et al., Polyhedron,
2009, vol. 28, no. 16, p. 3628.
The authors declare that they have no conflicts of
interest.
17. Dobrohotova, Zh.V., Sidorov, A.A., Kiskin, M.A.,
et al., J. Solid State Chem., 2010, vol. 183, no. 10,
p. 2475.
REFERENCES
18. Hong, M., Choi, H.C., and Byon, H.R., Chem. Mater.,
1. Sidorov, A.A., Kiskin, M.A., Aleksandrov, G.G., et al.,
2015, vol. 27, p. 2234.
Russ. J. Coord. Chem., 2016, vol. 42, p. 621.
19. Cheprakova, E.M., Verbitskiy, E.V., Kiskin, M.A.,
https://doi.org/10.1134/S1070328416100031
et al., Polyhedron, 2015, vol. 100, p. 89.
2. Bazhina, E.S., Aleksandrov, G.G., Efimov, N.N.,
et al., Russ. Chem. Bull., Int. Ed., 2013, vol. 62, no. 4,
p. 962.
20. Sidorov, A.A., Kiskin, M.A., Aleksandrov, G.G., and
Eremenko, I.L., Russ. Chem. Bull., Int. Ed., 2016,
vol. 65, no. 11, p. 2754.
21. Fedushkin, I.L., Skatova, A.A., Chudakova, V.A., and
Fukin, G.K., Angew. Chem., Int. Ed., 2003, vol. 42,
p. 3294.
3. Bazhina, E.S., Aleksandrov, G.G., Kiskin, M.A., et al.,
Russ. Chem. Bull., Int. Ed., 2016, vol. 65, no. 1, p. 249.
4. Zorina-Tikhonova, E., Gogoleva, N., Sidorov, A.,
et al., Eur. J. Inorg. Chem., 2017, p. 1396.
22. Fokin, S.V., Letyagin, G.A., Romanenko, G.V., et al.,
5. Gogoleva, N.V., Zorina-Tikhonova, E.N., Bogomya-
Russ. Chem. Bull., Int. Ed., 2018, vol. 67, no. 1, p. 61.
kov, A.S., et al., Eur. J. Inorg. Chem., 2017, p. 547.
23. SMART (сontrol) and SAINT (integration) Software.
Version 5.0. Madison (WI, USA): Bruker AXS, Inc., 1,
p. 997.
24. Sheldrick, G.M., SADABS. Program for Scanning and
Correction of Area Detector Data, Göttinngen (Germa-
ny): Univ. of Göttingen, 2004.
6. Zauzolkova, N.V., Nikiforova, M.E., Kiskin, M.A.,
et al., Russ. Chem. Bull. Int. Ed., 2011, vol. 60, no. 2,
p. 273.
7. Gogoleva, N.V., Zorina-Tikhonova, E.N., Kiskin, M.A.,
et al., Russ. Chem. Bull. Int. Ed., 2014, vol. 63, no. 12,
p. 2741.
25. Sheldrick, G.M., Acta Crystallogr., Sect. A: Found.
8. Ferey, G., Millange, F., Morcrette, M., et al., Angew.
Crystallogr., 2008, vol. 64, no. 1, p. 112.
Chem., Int. Ed., 2007, vol. 46, p. 3259.
26. Kiskin, M.A., Fomina, I.G., Aleksandrov, G.G., et al.,
9. Aromi, G., Bell, A.R., Helliwell, M., et al., Chem.-Eur.
J., 2003, vol. 9, p. 3024.
Inorg. Chem. Commun., 2004, vol. 7, p. 734.
10. Bazhina, E.S., Aleksandrov, G.G., Kiskin, M.A., et al.,
Translated by Z. Svitanko
Polyhedron, 2017, vol. 137, p. 246.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY
Vol. 46
No. 2
2020