Cobalt(II) complexes with bis-2,4-[N-(S)-phenylalanyl]-6-chlorotriazine: Synthesis, structure, and application for separation of enantiomers of butan-2-ol

Article abstract of DOI:10.1007/s11172-015-0910-x

The chiral coordination compounds [Co(L)(H₂O)₂(MeOH)] _n (1) and Co₂(L)₂(H₂O)(MeOH)₄ (2) were synthesized by the reaction of bis-2,4-[N-(S)-phenylalanyl]6-chlorotriazine (LH₂) with cobalt(II) pivalate or acetate. In molecules 2, the CoII ions are linked by a bridging water molecule and two carboxy groups of the L^2- anion. By passing the racemate of butan-2-ol through a chromatographic column containing complex 1 as the stationary phase, a mixture enriched with the (S)-isomer of this alcohol can be obtained.

Full text of DOI:10.1007/s11172-015-0910-x

Russian Chemical Bulletin, International Edition, Vol. 64, No. 3, pp. 630—635, March, 2015
630
Cobalt(II) complexes with bisꢀ2,4ꢀ[Nꢀ(S)ꢀphenylalanyl]ꢀ6ꢀchlorotriazine:
synthesis, structure, and application for separation
of enantiomers of butanꢀ2ꢀol*
Yu. A. Satskaya,a N. P. Komarova,b K. S. Gavrilenko,b,c O. V. Manoylenko,b,c M. A. Kiskin,d
S. V. Kolotilov,a I. L. Eremenko,d and V. M. Novotortsevd
aL. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine,
31 prosp. Nauki, 03028 Kiev, Ukraine.
Eꢀmail: svk001@mail.ru
bEnamine Ltd.,
61 Chervonotkaska ul., 03022 Kiev, Ukraine.
Eꢀmail: kgavrio@mail.ru
cChembioCenter, Taras Shevchenko National University of Kyiv,
61 Chervonotkackaya ul., 03022 Kiev, Ukraine.
dN. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
31 Leninsky prosp., 119991 Moscow, Russian Federation.
Eꢀmail: mkiskin@igic.ras.ru
The
chiral
coordination
compounds
[Co(L)(H2O)2(MeOH)]n
(1)
and
Co2(L)2(H2O)(MeOH)4 (2) were synthesized by the reaction of bisꢀ2,4ꢀ[Nꢀ(S)ꢀphenylalanyl]ꢀ
6ꢀchlorotriazine (LH2) with cobalt(II) pivalate or acetate. In molecules 2, the CoII ions are
linked by a bridging water molecule and two carboxy groups of the L2– anion. By passing the
racemate of butanꢀ2ꢀol through a chromatographic column containing complex 1 as the
stationary phase, a mixture enriched with the (S)ꢀisomer of this alcohol can be obtained.
Key words: chiral metal complexes, cobalt, phenylalanine, separation of enantiomers,
butanꢀ2ꢀol, chromatography.
Chiral coordination compounds, including coordinaꢀ
The optical activity of coordination compounds may
arise from the presence of fragments of chiral molecules in
these compounds15—27 or result from the formation of
chiral crystal lattices from achiral molecules and ions.28—30
Metal complexes based on synthetic optically active comꢀ
pounds, the application of which enables the achievement
of almost complete separation of enantiomers, were docuꢀ
mented.26,27 However, rather large amounts of an adsorꢀ
bent are required for the preparative separation of enantiꢀ
omers by sorption or chromatographic methods. Thereꢀ
fore, the development of methods for the preparation of
chiral coordination compounds based on available natural
optically active compounds, such as oxy acids,19—21 amino
acids,22,23,31 campharates,15—18 or cyclodextrins,24,25 as
well as investigation of the properties of these systems are
important problems. These compounds hold promise due
to the simplicity of introducing chiral functional groups
into coordination compounds.
tion polymers, have been attracted attention because such
systems hold promise for the enantioselective catalysis1—4
and the analytical or preparative separation of enantiꢀ
omers5—9 and have unusual properties, such as the ability
to change the angle of rotation of polarized light induced by
changes in the magnetic characteristics of these compounds
(complexes with paramagnetic ions),10,11 as well as nonꢀ
linearꢀoptical properties.12,13 It is well known that organic
optically active compounds can be used for the sorption or
chromatographic separation of enantiomers.14 Meanwhile,
the scope of application of complex (metalꢀcontaining) chiral
compounds is much wider due to the presence of metal
ions, which can provide light absorption (this is important
for magnetoꢀoptics) and catalytic activity and are responꢀ
sible for characteristics of the porous structure of coordiꢀ
nation polymers. Therefore, the development of new methꢀ
ods for the synthesis of chiral metal complexes is an imꢀ
portant problem of modern coordination chemistry.
The aim of the present work is to synthesize new chiral
complexes based on the natural amino acid (S)ꢀphenylꢀ
alanine, determine the structures of the resulting coordiꢀ
nation compounds, and examine the possibility of their
* Dedicated to Academician of the Russian Academy of Sciences
V. I. Minkin on the occasion of his 80th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 0630—0635, March, 2015.
1066ꢀ5285/15/6403ꢀ0630 © 2015 Springer Science+Business Media, Inc.

Cobalt(II) complexes with chlorotriazine
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 3, March, 2015
631
application for the chromatographic separation of the raceꢀ
mate of butanꢀ2ꢀol.
the reaction mixture contains Co2+ and L2– ions in an
amount sufficient for the formation of a precipitate in
accordance with the solubility product. However, if it
would be the only criterion, the evaporation of the mother
liquor will afford the same coordination polymer 1. It
seems that the change in the acidity of the reaction mediꢀ
um in the course of the reaction plays an important role.
The accumulation of pivalic acid due to the deprotonation
of LH2 by pivalate ions probably interferes with the forꢀ
mation of the insoluble coordination polymer. This is
presumably analogous to the effect of insignificant changꢀ
es in the acidity on the composition of polynuclear comꢀ
plexes and coordination polymers with amino acids deꢀ
scribed earlier.34
In this work, we synthesized the chiral cobalt coordiꢀ
nation polymer [Co(L)(H2O)2(MeOH)]n (1) and the
chiral binuclear complex Co2(L)2(H2O)(MeOH)4 (2).
where LH2 is bisꢀ2,4ꢀ[Nꢀ(S)ꢀphenylalanyl]ꢀ6ꢀchlorotriꢀ
azine. The structure of compound 2 was determined by
Xꢀray diffraction. The efficiency of the separation of enanꢀ
tiomers of butanꢀ2ꢀol by liquid chromatography using
complex 1 as the stationary phase was evaluated.
The composition of complex 1 was determined by eleꢀ
mental analysis, but we failed to obtain crystals of these
compound suitable for Xꢀray diffraction. Based on the
elemental analysis, compound 1 contains cobalt(II) and
L2+ in a ratio of 1 : 1. Taking into account that complex 1
is insoluble in most of solvents, this compound is probably
a coordination polymer similar to 3d metal complexes
with other carboxylates containing the triazine ring.35,36
Molecular structure of 2. The Xꢀray diffraction study
showed that compound 2 is a binuclear complex, which
crystallizes as a solvate in the space group P21. In the unit
cell, there are eight uncoordinated water molecules per
two crystallographically nonequivalent molecules 2 (2А
and 2B). The structures of these molecules differ only in
some bond lengths and bond angles (Table 1; the angles
for one of the Co2+ ions are given in the table to illustrate
the distortions of the coordination polyhedra). Since molꢀ
ecules 2А and 2B are structurally similar, the structure
only of binuclear molecule 2А containing the Co(1) and
Co(2) atoms will be described in detail hereinafter. Moleꢀ
cule 2 does not have symmetry elements. Both Co2+ ions
are in an O6 octahedral coordination formed by donor
O atoms with insignificant axial distortions along
the O(1)—Co(1)—O(6) and O(1)—Co(2)—O(12) lines
Results and Discussion
Synthesis of the ligand and complexes. Dicarboxylic
acid LH2 was synthesized by the replacement of two
chlorine atoms in cyanuric chloride by (S)ꢀphenylalanine
moieties in an alkaline medium at 70 C. Under these
conditions, two of the three chlorine atoms of cyanuric
chloride are involved in the reaction, which is in agreeꢀ
ment with the known empirical rule:32,33 in the reaction of
cyanuric chloride with amines, the first chlorine atom of
cyanuric chloride is replaced at 0 C; the second, at
30—50 C; the third, at 90—100 C. In this case, the temꢀ
perature of the reaction mixture plays, apparently, a more
important role than the reagent ratio.
Coordination polymer 1 is produced as an amorphous
pink precipitate by the reaction of solutions of [Co(Piv)2]n
and LH2 in methanol at room temperature, whereas binuꢀ
clear complex 2 is formed as crystals after evaporation of
methanol from the filtrate. Both these compounds are
chiral because they contain residues of the natural amino
acid (S)ꢀphenylalanine. The L2– ligand is coordinated to
the Co2+ ion as the dianion, since LH2 is deprotonated as
a result of the reaction of this compound with the pivalate
anion. Complexes 1 and 2 are electrically neutral. The
charges of the L2– anions are compensated by the charges
of the Co2+ cations. It should be noted that the reaction
with cobalt(II) acetate instead of pivalate produces the
same results, but, according to the elemental analysis, the
reaction products contain impurities.
Table 1. Selected bond lengths (d) in structure 2
Bond
d/Å
Bond
d/Å
Co(1)—O(1)
Co(1)—O(2)
Co(1)—O(3)
Co(1)—O(4)
Co(1)—O(5)
Co(1)—O(6)
Co(2)—O(1)
Co(2)—O(8)
Co(2)—O(9)
Co(2)—O(10)
Co(2)—O(11)
Co(2)—O(12)
2.125(7)
2.038(7)
2.083(7)
2.110(7)
2.039(7)
2.137(8)
2.123(6)
2.064(7)
2.126(7)
2.023(7)
2.052(7)
2.142(8)
Co(3)—O(14)
Co(3)—O(15)
Co(3)—O(16)
Co(3)—O(17)
Co(3)—O(18)
Co(3)—O(19)
Co(4)—O(21)
Co(4)—O(22)
Co(4)—O(23)
Co(4)—O(24)
Co(4)—O(25)
Co(4)—O(14)
2.128(6)
2.072(7)
2.076(7)
2.030(8)
2.148(7)
2.105(8)
2.069(8)
2.020(7)
2.142(7)
2.053(8)
2.136(8)
2.151(7)
The formation of different complexes, 1 and 2, from
the same reaction mixture can be explained as follows.
The formation of insoluble compound 1 occurs until

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Kiskin et al.
Table 2. Selected bond angles () in structure 2
Angle /deg Angle
O(6)
*
Cl(1)
O(4)
O(3)
N(6)
/deg
N(4)
Co(1)
O(7)
N(7)
O(2)
N(1)
*
O(1)—Co(1)—O(2) 90.8(3)
O(1)—Co(1)—O(3) 93.5(3)
O(1)—Co(1)—O(4) 90.3(3)
O(1)—Co(1)—O(5) 94.4(3)
O(1)—Co(1)—O(6) 173.2(4)
O(2)—Co(1)—O(3) 91.6(3)
O(2)—Co(1)—O(4) 175.7(3)
O(2)—Co(1)—O(5) 97.8(3)
O(2)—Co(1)—O(6) 83.4(4)
O(3)—Co(1)—O(4) 84.2(3)
O(3)—Co(1)—O(5) 167.6(3)
O(3)—Co(1)—O(6) 90.3(4)
O(4)—Co(1)—O(5) 86.2(3)
O(4)—Co(1)—O(6) 95.8(3)
O(5)—Co(1)—O(6) 82.9(4)
O(13)
N(3)
N(9)
O(1)
O(5)
O(11)
N(2)
N(5)
N(10)
*
N(8)
O(8)
O(9)
O(10)
Cl(2)
O(12)
Fig. 1. Molecular structure of 2A. The phenyl groups and all
hydrogen atoms are omitted. The carbon atoms to which the
phenyl groups are attached are marked with an asterisk.
* The angles for the coordination environment of the Co(1) atom
are given; the corresponding angles for the Co(2), Co(3), and
Co(4) atoms have similar values.
(the corresponding O—Co—O angles are 173.2(4) and
174.8(3), Fig. 1). In molecule 2А, the Co—O bond lengths
involving oxygen atoms in the equatorial plane are, on the
average, 2.07 Å (the exact bond lengths are given in Table 1),
which is somewhat smaller than the Co—O bond lengths
involving oxygen atoms lying on the tetragonal axis of the
octahedron (aver., 2.13 Å). The coordination polyhedra of
the Co(1) and Co(2) ions in molecule 2А are structurally
similar. The equatorial plane of the chromophore conꢀ
taining the Co(1) atom is formed by two oxygen atoms of
deprotonated carboxy groups of one L2– ligand, O(4) and
O(5), one oxygen atom of the carboxy groups of another
L2– ligand, O(2), and the oxygen atom of methanol, O(3).
The sum of the O—Co—O angles in the equatorial plane is
359.8° (Table 2). Hence, it can be concluded that the
Co(1) and O(2)—O(5) atoms lie nearly in one plane. The
axial positions of the chromophore Co(1)O6 are occupied
by the oxygen atom O(1) of the bridging water molecule
and the oxygen atom O(6) of the methanol molecule. The
Co(1) and Co(2) ions are linked via a ꢀbridging water
molecule and two O,O´ꢀbridging carboxy groups (see Fig. 1).
Therefore, a molecule of one independent unit 2А is formed
by the connection of the Co(1) and Co(2) ions by one
water molecule and two anions of the L2– ligand. The
uncoordinated O(7) and O(13) atoms of the carboxylate
anions apparently form a hydrogen bond with the bridging
water molecule (the d(O(1)—O(7)) and d(O(1)—O(13))
distances are 2.558(1) and 2.612(9) Å, respectively).
In the crystal lattice, the planes of the phenyl and
triazine rings of adjacent molecules 2 are nearly parallel to
each other, and the distances between these planes are
shorter than 4 Å (the shortest distances d(N(4)—C(85)) =
= 3.39(4) Å, d(N(18)—C(19)) = 3.42(2) Å, Fig. 2). This
arrangement of aromatic rings is evidence of ꢀstacking
interactions. It should be noted that similar contacts were
found only in pairs of binuclear complexes, whereas the
formation of a polymer chain through such interactions is
not observed in this case.
Separation of enantiomers of butanꢀ2ꢀol. An analysis of
the factors that have an effect on the efficiency of the
separation of enantiomers of butanꢀ2ꢀol by chiral coordiꢀ
nation polymers is a difficult problem because, as follows
from the literature data, in most cases isomers of aliphatic
monohydric alcohols are more difficult to separate7,8,37
than compounds containing two or more groups capable
N(18)
C(19)
N(4)
c
0
C(18)
b
a
Fig. 2. Fragment of the crystal structure of compound 2. The hydrogen atoms and uncoordinated water molecules are omitted. The
lines between the centers of the sixꢀmembered rings indicate possible ꢀstacking interactions.

Cobalt(II) complexes with chlorotriazine
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 3, March, 2015
633
of forming relatively highꢀenergy interactions (diols, pheꢀ
nylethanol and its analogs, etc.).31,37—39 Despite the fact
that the use of some optically active coordination comꢀ
pounds enables the separation of enantiomers of butanꢀ2ꢀ
ol with an efficiency close to 100%,6,27,40 many adsorbꢀ
ents capable of separating isomers of certain chiral organꢀ
ic compounds are inefficient in the separation of isomers
of monohydric alcohols or their derivatives.7,8
The possibility of using insoluble compound 1 as
a carrier for the chromatographic separation of enantioꢀ
mers of butanꢀ2ꢀol was evaluated by liquid column chroꢀ
matography. The racemate of butanꢀ2ꢀol was passed
through a 20ꢀcm column packed with a sample of 1 with
a weight of 0.45 g, which resulted in the enrichment of the
mixture with the (S)ꢀisomer (the (R)ꢀisomer is, correꢀ
spondingly, adsorbed; Fig. 3). The first portion of butanꢀ
2ꢀol eluted from the column (0.09 mL) did not contain,
within experimental error, an excess of one of the isomers
of butanꢀ2ꢀol. The enantiomeric excess (ee = 1.0 0.3 %,
where ee = 100%•|c(R) – c(S)|/(c(R) + c(S), c(R) and
c(S) are the concentrations or weights of (R)ꢀ and (S)ꢀ
isomers, respectively) was observed in the second portion
(once 0.09—0.18 mL of the racemate was passed through
the column, see Fig. 3). The column containing 0.45 g of
the adsorbent gives 0.07 g of a solution containing the
1.0 0.3% enantiomeric excess of (S)ꢀbutanꢀ2ꢀol, or, in
total, 0.3 g of the solution with ee of about 0.7%.
[Cu(sala)]n, where H2sala is Nꢀ(2ꢀhydroxybenzyl)ꢀ(S)ꢀ
alanine) cannot be used as carriers in chromatographic
columns to separate isomers of butanꢀ2ꢀol or Oꢀtrifluoroꢀ
acetylꢀ2ꢀmethylbutanꢀ1ꢀol, respectively.8,41 Analogously, the
chiral coordination polymer Zn4O(btb)4/3(L)(DEF)19(H2O)6,
where H3btb is 1,3,5ꢀtris(4ꢀcarboxyphenyl)benzene, H2L
is 2ꢀ(Nꢀ(4S)ꢀbenzylꢀ2ꢀoxooxazolidinꢀ3ꢀyl)ꢀ1,4ꢀbenzeneꢀ
dicarboxylic acid, also proved to be inefficient in the
chromatographic separation of enantiomers of butanꢀ2ꢀ
ol.7 Therefore, compound 1 is less efficient in the chromaꢀ
torgraphic separation of enantiomers of butanꢀ2ꢀol comꢀ
pared with the coordination polymer based on lactate, but
it is more efficient than some chiral coordination polyꢀ
mers containing a nitrogen atom in the vicinity of an asymꢀ
metric center.
It should be noted that in the case of sorption of pure
enantiomers of butanꢀ2ꢀol from the gas phase, the comꢀ
pound [Ni2(asp)2(4,4´ꢀbpy)]n better absorbs (R)ꢀbutanꢀ
2ꢀol.41 The chirality of this coordination polymer is due to
the presence of an ꢀaminocarboxylate moiety containing
the asymmetric center in the (R)ꢀconfiguration.5 Comꢀ
pound 1 also better retains (R)ꢀbutanꢀ2ꢀol, but it contains
ꢀaminocarboxylate moieties in the (S)ꢀconfiguration.
A comparison of these data suggests that the configuration
of a certain asymmetric center is not a key factor responꢀ
sible for the preferable adsorption of enantiomers of this
substrate. This is in good agreement with the results of the
simulation of guest—host interactions in chiral coordinaꢀ
tion compounds, which demonstrate that multicenter inꢀ
teractions play an important role in the recognition of
enantiomers.37
The efficiency of compound 1 in the chromatographic
separation of enantiomers of butanꢀ2ꢀol is lower than that
of the porous coordination polymer [Zn((S)ꢀLact)(bdc)]n
(Lact2– is (S)ꢀlactate, bdc2– is 1,4ꢀbenzenedicarboxylate).
The application of the latter under exactly the same conꢀ
ditions provides the 4.4 1.5% enantiomeric excess of (S)ꢀ
butanꢀ2ꢀol.41 Meanwhile, chiral porous coordination polyꢀ
mers containing ꢀamino acid moieties ([Ni2(asp)2(4,4´ꢀ
bpy)]n, where Asp2– is the (R)ꢀaspartic acid dianion, and
Therefore, we showed that the reaction of bisꢀ2,4ꢀ[Nꢀ
(S)ꢀphenylalanyl]ꢀ6ꢀchlorotriazine with cobalt(II) carbꢀ
oxylates affords chiral coordination polymer 1. The forꢀ
mation of compound 1 ceased with an increase in the
amount of carboxylic acid in the reaction mixture (due to
the deprotonation of LH2 by carboxylate ions involved in
the starting cobalt salt), and binuclear complex 2 began to
form. The structure of the latter was confirmed by Xꢀray
diffraction. It was found that compound 1 can be used as
a stationary phase in chromatographic columns to sepaꢀ
rate enantiomers of butanꢀ2ꢀol and can be applied to preꢀ
pare a mixture enriched with (S)ꢀbutanꢀ2ꢀol.
ee (%)
1.0
0.5
0
Experimental
All experimental operations employed in the synthesis of
new complexes were performed in air using commercial solvents
and reagents of reagent grade without additional purification.
The polymer [Co(piv)2]n was synthesized by a procedure deꢀ
scribed earlier.42 Enantiomers of butanꢀ2ꢀol (Acros Organics)
contained 99% of the pure isomer. The composition of the samꢀ
ples was confirmed by elemental analysis on a Carlo Erba 1106
analyzer.
–0.5
0.10 0.15
0.20
0.25 0.30 0.35 V/mL
Fig. 3. Enantiomeric excess of (S)ꢀbutanꢀ2ꢀol in the portions
eluted from a column packed with compound 1 versus the volꢀ
ume of the passed racemate of butanꢀ2ꢀol (analysis of sequential
0.09ꢀmL portions ).
Bisꢀ2,4ꢀ[Nꢀ(S)ꢀphenylalanyl]ꢀ6ꢀchlorotriazine (LH2). A mixꢀ
ture of (S)ꢀphenylalanine (1.8 g, 15 mmol), cyanuric chloride

634
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Kiskin et al.
(0.96 g, 5 mmol), and NaHCO3 (0.92 g, 10 mmol) in water
(40 mL) was stirred at 70 C for 24 h. Then a 2 M NaOH solution
(3 mL) was added, and the resulting mixture was acidified with
3 M HCl to pH 1—2. The cooling of the mixture to 0—5 C
afforded a white precipitate, which was filtered on a glass filter,
washed with water (100 mL), and dried at 50 C. The yield was
65%. Found (%): C, 56.4; H, 4.23; N, 15.0. C21H21N5O4.5Cl
(LH2·0.5H2O). Calculated (%): C, 55.9; H, 4.69; N, 15.5.
{Bisꢀ2,4ꢀ[Nꢀ(S)ꢀphenylalanyl]ꢀ6ꢀchlorotriazino}di(aqua)ꢀ
(90 : 10, v/v)). The absolute configuration of the isomer of buꢀ
tanꢀ2ꢀol was determined by comparing its chromatogram with
the chromatogram of the pure isomer. Before the analysis, each
portion of the alcohol obtained after passing through the column
was modified by the treatment with phenyl isocyanate in benzꢀ
ene (7 mL) with continuous stirring at 70 C for 24 h (this treatꢀ
ment gives Oꢀ(2ꢀbutyl)ꢀNꢀphenylcarbamate). The reference
samples were prepared by the same procedure starting from the
pure Rꢀ or Sꢀisomer of the alcohol (0.2 mL) and phenyl isocyanꢀ
ate (0.6 mL); the racemization was not observed.
1
methanolcobalt(II), [Co(L)(H2O)2(MeOH)] (1) and di(, ꢀbisꢀ
2,4ꢀ(Nꢀ(S)ꢀphenylalanyl)ꢀ6ꢀchlorotriazinoꢀO,O´,O´´´)(ꢀ
1
aqua)tetra( ꢀmethanol)dicobalt(II), Co2(L)2(H2O)(MeOH)4 (2).
This study was financially supported by the National
Academy of Sciences of Ukraine and the Russian Founꢀ
dation for Basic Research (Joint Grant 03ꢀ03ꢀ14, RFBS
Project No. 14ꢀ03ꢀ90423) and the Council on Grants at
the President of the Russian Federation (Program for State
Support of Leading Scientific Schools of the Russian Fedꢀ
eration, Grant NShꢀ4773.2014.3).
Coordination polymer 1 was synthesized as follows. A solution
of [Co(piv)2]n (261 mg, 1 mmol) in MeOH (10 mL) was added to
a solution of LH2 (442 mg, 1 mmol) in MeOH (10 mL). The
reaction mixture was stirred for 10 min, during which an amorꢀ
phous precipitate of complex 1 formed. The precipitate was sepꢀ
arated by the filtration on a glass filter and washed with methaꢀ
nol (50 mL). The yield was 55%. Found (%): C, 46.3; H, 4.18;
N, 11.9. C22H26N5O11ClCo ([Co(L)(H2O)2(MeOH)]n). Calcuꢀ
late (%) C, 46.6; H, 4.62; N, 12.4.
The filtrate obtained after the separation of 1 was allowed to
be concentrated at room temperature. After 3—4 days, large
pink prismatic crystals of compound 2 formed. The crystals were
filtered off on a paper filter and washed with methanol (20 mL).
The yield was 30% (based on the starting compound [Co(piv)2]n).
Found (%): C, 45.3; H, 5.21; N, 10.3. C46H62N10O17Cl2Co2
(Co2(L)2(H2O)(MeOH)4•4H2O). Calculated (%): C, 45.4;
H, 5.14; N, 11.5.
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T = 120(2) K, monoclinic system, space group P21, a = 17.618(3) Å,
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–1
= 6030.7(16) Å3, Z = 2, dcalc = 1.339 g cm–3,  = 0.709 mm
,

= 27.51, 59765 measured reflections, 27525 unique reflecꢀ
max
tions, Rint = 0.0757, GOOF = 1.063, R1 (I > 2I)) = 0.1088, wR2
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Received January 26, 2015;
in revised form February 6, 2015