From mono- and dinuclear to polynuclear cobalt(II) and cobalt(III) coordination compounds based on o-phthalic acid and 2,2′-bipyridine: Synthesis, crystal structures, and properties

Article abstract of DOI:10.1002/ejic.200500008

The reaction of o-phthalic acid (H₂Pht) and 2,2′- bipyridine (bpy) with cobalt(II) carbonate at different temperatures results in the isolation of three types of new cobalt(II) and cobalt(III) compounds. The mononuclear cobalt(III) complex [Co(CO₃)(bpy)₂] ₂(Pht)·16H₂O (1) is obtained when the reaction is run at 60°C. Crystallographic analysis revealed that 1 contains two crystallographically independent [Co(CO₃)-(bpy)₂] ⁺ cations, a Pht^2- anion, and sixteen solvate water molecules. The latter form a wall of channels with the oxygen atoms of the carboxylate groups of the Pht^2- anions, which are occupied by pairs of cations. Increasing the temperature of the reaction to 80°C leads to the formation of the open dinuclear cobalt(II) complex [(bpy)₂Co(Pht) H(Pht)Co(bpy)₂]-(HPht)(H₂Pht)·2H₂O (2), which crystallizes in two polymorphic modifications 2a and 2b. Compound 2a consists of a centrosymmetric dinuclear [(bpy)₂Co(Pht)H(Pht)Co(bpy) ₂]⁺ cation, an HPht^- anion, an H₂Pht molecule, and two solvate H₂O molecules. In 2b, a small alteration in the crystal structure leads to an increase of the unit-cell volume. The asymmetric unit of 2b contains six crystallographically independent Co ^II complexes, which combine into four [(bpy)₂Co(Pht)H(Pht) -Co(bpy)₂]⁺ units. The main structural unit of the cyclic dinuclear complex [Co(Pht)(bpy)(H₂O)]₂·2H ₂O (4) is neutral and cenrosymmetric, with the two Co^II atoms linked by two phthalate ligands to form a 14-membered cycle. A further temperature increase results in the isolation of both the mononuclear complex [Co(Pht)(bpy)(H₂O)₃]·3H₂O (3) and the polynuclear helical coordination polymer [Co(Pht)(bpy)-(H₂O)] _n (5). Extended hydrogen bonding networks as well as aromatic π-π stacking interactions stabilize multidimensional supramolecular architectures in all compounds. Magnetic susceptibility measurements have been performed for complexes 1, 2, 3, and 5. Simulations gave the following parameter sets: for complex 2 |D| = 70 cm^-1, g = 2.55 and J = -0.1 cm ^-1; for complex 3 |D| = 80 cm^-1, g = 2.6 and for complex 5 |D| = 65 cm^-1, g = 2.45. Complex 1 is diamagnetic. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.

Full text of DOI:10.1002/ejic.200500008

FULL PAPER
From Mono- and Dinuclear to Polynuclear Cobalt(II) and Cobalt(III
)
Coordination Compounds Based on o-Phthalic Acid and 2,2Ј-Bipyridine:
Synthesis, Crystal Structures, and Properties
Svetlana G. Baca,*[a] Irina G. Filippova,[b] Christina Ambrus,[c] Maria Gdaniec,[d]
Yurii A. Simonov,[b] Nicolae Gerbeleu,[a] Olesea A. Gherco,[b] and Silvio Decurtins[c]
Keywords: Carboxylate ligands / Cobalt / Magnetic properties / N ligands
The reaction of o-phthalic acid (H2Pht) and 2,2Ј-bipyridine
(bpy) with cobalt(II) carbonate at different temperatures re-
sults in the isolation of three types of new cobalt(II) and co-
balt(III) compounds. The mononuclear cobalt(III) complex
[Co(CO3)(bpy)2]2(Pht)·16H2O (1) is obtained when the reac-
tion is run at 60 °C. Crystallographic analysis revealed that 1
contains two crystallographically independent [Co(CO3)-
(bpy)2]+ cations, a Pht2– anion, and sixteen solvate water
molecules. The latter form a wall of channels with the oxygen
atoms of the carboxylate groups of the Pht2– anions, which
are occupied by pairs of cations. Increasing the temperature
of the reaction to 80 °C leads to the formation of the open
dinuclear cobalt(II) complex [(bpy)2Co(Pht)H(Pht)Co(bpy)2]-
unit of 2b contains six crystallographically independent CoII
complexes, which combine into four [(bpy)2Co(Pht)H(Pht)-
Co(bpy)2]+ units. The main structural unit of the cyclic dinu-
clear complex [Co(Pht)(bpy)(H2O)]2·2H2O (4) is neutral and
cenrosymmetric, with the two CoII atoms linked by two
phthalate ligands to form a 14-membered cycle. A further
temperature increase results in the isolation of both the mo-
nonuclear complex [Co(Pht)(bpy)(H2O)3]·3H2O (3) and the
polynuclear helical coordination polymer [Co(Pht)(bpy)-
(H2O)]n (5). Extended hydrogen bonding networks as well as
aromatic π–π stacking interactions stabilize multidimensional
supramolecular architectures in all compounds. Magnetic
susceptibility measurements have been performed for com-
(HPht)(H2Pht)·2H2O (2), which crystallizes in two polymor- plexes 1, 2, 3, and 5. Simulations gave the following parame-
phic modifications 2a and 2b. Compound 2a consists of a cen- ter sets: for complex 2 |D| = 70 cm–1, g = 2.55 and J =
trosymmetric dinuclear [(bpy)2Co(Pht)H(Pht)Co(bpy)2]+ cat-
ion, an HPht– anion, an H2Pht molecule, and two solvate H2O
molecules. In 2b, a small alteration in the crystal structure
leads to an increase of the unit-cell volume. The asymmetric
–0.1 cm–1; for complex 3 |D| = 80 cm–1, g = 2.6, and for com-
plex 5 |D| = 65 cm–1, g = 2.45. Complex 1 is diamagnetic.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
and synthesis of novel metal carboxylates by employing new
synthetic tools or by varying the nature of the reactants and
synthetic conditions are currently under active investiga-
tion. In this context, o-phthalic acid (H2Pht), which can
exhibit a variety of coordination abilities[3] and has a ten-
dency to form large metal cluster aggregates[4–9] or architec-
tures with multi-dimensional frameworks, has been exten-
sively explored. We have recently reported a series of
nickel(ii), copper(ii), and zinc(ii) phthalate com-
pounds[3,10–16] that show a great structural diversity, rang-
ing from monomeric to polymeric assemblies. Herein we
extend these studies to investigate the interactions of this
universal ligand with cobalt ions in the presence of aro-
matic amines. In this respect, several cobalt phthalate com-
pounds that are already known should be mentioned here.
A very interesting example of a three-dimensional cobalt(ii)
polymer, namely [Co(Pht)2(bipy)]n (bipy = 4,4Ј-bipyridine),
which consists of interlinked Co–Pht–Co and Co–bpy–Co
linear chains, has been reported by Lightfoot et al.[17] Sev-
eral dimers linked by o-phthalate [Co2(Pht)(L)(H2O)]-
(ClO4)2 (L = 2,2Ј-bipyridine, 1,10-phenanthroline, and 5-ni-
Introduction
Carboxylate complexes have received a great deal of at-
tention over the last few years due to their interesting coor-
dination chemistry, unusual structural features, remarkable
physical and chemical properties, and extensive practical
applications as dyes, extractants, drugs, pesticides, magnetic
devices, etc.[1] Metal carboxylates with a high stability are
also efficient catalysts in a vast range of chemical and bio-
chemical processes.[2] Although a great number of metal
carboxylates have been obtained to date, the rational design
[a] Institute of Chemistry, Academy of Sciences of Moldova,
Academiei 3 str., 2028 Chisinau, R. Moldova
Fax: +373-22-739611
E-mail: sbaca_md@yahoo.com
[b] Institute of Applied Physics, Academy of Sciences of Moldova,
Academiei 5 str., 2028 Chisinau, R. Moldova
[c] Department of Chemistry and Biochemistry, University of
Berne,
3012 Berne, Switzerland
[d] Faculty of Chemistry, A. Mickiewicz University,
60-780 Poznan, Poland
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
3118
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DOI: 10.1002/ejic.200500008
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Mono-, Di- and Polynuclear Cobalt(ii) and Cobalt(iii) Coordination Compounds
FULL PAPER
tro-1,10-phenanthroline) have also been isolated.[18] Finally, four new coordination compounds, as shown in Scheme 1.
the monomeric complexes [Co(Pht)(phen)(H2O)3]·H2O and An oxidation of cobalt(ii) ions to cobalt(iii) was observed
[Co(Pht)(dipya)] (phen = 1,10-phenanthroline, dipya = 2,2Ј- when the reaction was carried out at 60 °C in the presence
dipyridylamine) have been synthesized.[19] Recently, we have of the base K2CO3, and the reaction mixture was left in
also described the synthesis and structural characterization contact with air. This resulted in the formation of crystals
of cobalt(ii) phthalate coordination polymers with deriva- of the cobalt(iii) complex [Co(CO3)(bpy)2]2(Pht)·16H2O (1)
tives of imidazole, for example 1-methylimidazole (1- in two weeks. To the best of our knowledge, 1 is the first
MeIm),[3] 2-methylimidazole (2-MeIm),[12] and 4-methyl- example of a trivalent cobalt compound with o-phthalic
imidazole (4-MeIm).[15] In this paper we report on the syn- acid, although in 1 the phthalate dianion is acting only as
thesis, characterization, and crystal structures of three types a counterion. It is interesting to note that similar bis(bipyri-
of new cobalt(ii) and cobalt(iii) compounds with o-phthalic dine)(carbonato)cobalt(iii) nitrate and iodide complexes
acid and 2,2Ј-bipyridine (bpy), namely the mononuclear co- have also been obtained from the initial cobalt(ii) salts but
balt(iii) and cobalt(ii) complexes [Co(CO3)(bpy)2]2- only under O2 or CO2.[20] It seems that the presence of aro-
(Pht)·16H2O (1) and [Co(Pht)(bpy)(H2O)3]·3H2O (3), matic amines such as bpy or phen facilitates the oxidation
respectively, the open dinuclear complex [(bpy)2Co(Pht)- of the initial cobalt(ii) species. Increasing the temperature of
H(Pht)Co(bpy)2](HPht)(H2Pht)·2H2O (2) and the cyclic di- the reaction to 80 °C leads to the formation of the dimeric
nuclear complex [Co(Pht)(bpy)(H2O)]2·2H2O (4), as well as complex
the polynuclear helical coordination
[Co(Pht)(bpy)(H2O)]n (5).
[(bpy)2Co(Pht)H(Pht)Co(bpy)2](HPht)(H2Pht)·
polymer 2H2O (2), the identity of which was confirmed by X-ray
crystallography. The two [Co(bpy)2]2+ units in 2 are con-
nected by a symmetric O···H···O hydrogen bond between
the carboxylate groups of two different coordinated phthal-
ate ligands. A similar Zn compound has recently been re-
ported.[14] Compound 2 crystallizes from hot H2O solution
in two polymorphic modifications (2a and 2b), which con-
Results and Discussion
Synthesis
sist of similar structural units and differ in the crystal struc-
The reaction of o-phthalic acid with cobalt(ii) carbonate
ture organization. Further increasing the reaction tempera-
in the presence of amine at different temperatures affords
Scheme 1.
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S. G. Baca et al.
FULL PAPER
ture resulted in the isolation of two new products, namely (calculated 43.08%). Complex 1 decomposes to the final
the coordination polymer [Co(Pht)(bpy)(H2O)]n (5) and the product Co2O3, with a remaining percentage of 13.22%
mononuclear complex [Co(Pht)(bpy)(H2O)3]·3H2O (3), (calculated 12.61%), when heated from 270 to 360 °C. For
which were obtained in around 20% and 12% yields, dimer 2, the first weight loss is observed from 70 to 150 °C
respectively. One needs to mention here that the cyclic di- and is due to the loss of two water molecules (observed
mer 4 (Scheme 1) was obtained from the reaction of co- 2.51%, calculated 2.50%). In the temperature range of 170–
balt(ii) acetate with H2Pht and bpy in MeOH in a very low 510 °C the decomposition of the organic ligands takes place
yield, therefore the sample was only suitable for X-ray stud- in four unidentified steps with a total weight loss of 85.91%
ies. All attempts to optimize the yield of 4 were unsuccess- to the final product CoO (found 11.39%, calculated
ful.
10.41%). For complex 3, the first weight loss corresponding
to both three uncoordinated and three coordinated water
molecules (found 21.91%, calculated 22.17%) is found in
the temperature range 30–150 °C. The second weight loss is
observed from 150 to 320 °C and corresponds to the disso-
ciation of the bpy ligand (found 30.31%, calculated
32.05%). The third weight loss of 19.58%, from 320 to
450 °C, is due to the loss of phenyl radical.[24,25] A further
weight loss of 11.49%, corresponding to the elimination of
two molecules of CO[26] (calculated 12.15%), occurs be-
tween 450 and 540 °C. The final product is CoO, with a
remaining percentage of 16.70% (calculated 15.37%). In
contrast to 1–3, the coordination polymer 5 is stable up to
approximately 180 °C and then it loses 4.42% of its weight,
which corresponds to the loss of a coordinated water mole-
cule (calculated 4.53%). A further mass decrease is ob-
served between 230 and 320 °C and corresponds to the loss
of the bpy molecule (found 38.05%, calculated 39.32%).
The decomposition of the Pht ligand is observed above
320 °C in two steps, with the weight loss of 18.65 and
14.10% each, by the removal of phenyl radical (calculated
20.28%) and two molecules of CO (calculated 15.93%),
respectively, and is completed below 440 °C to give the ex-
pected oxide (found 20.15%, calculated 18.86%).
Spectroscopic Studies
The most relevant features of the IR spectra of com-
pounds 1–3 and 5 are the absorptions due to the stretching
of the dicarboxylate groups. The positions of these bands
and the separations (Δν) between νasym(CO2) and νsym(CO2)
indicate that the phthalate carboxylate groups function in
different coordination modes. For complex 1, in which the
o-phthalic acid is fully deprotonated but acts only as a
counterion, the characteristic bands of the uncoordinated
carboxylate groups of Pht2– appear at 1678 and 1564 cm–1
for asymmetric stretching, and at 1403 and 1382 cm–1 for
symmetric stretching. In the IR spectrum of complex 2, the
medium-intensity peaks at 1717 and 1366 cm–1 also indicate
the presence of uncoordinated o-phthalic acid [νasym(CO2)
for o-phthalic acid of 1690 and 1678 cm–1].[21] The absorp-
tions at lower frequencies (1579 and 1411 cm–1) can be at-
tributed to deformation vibrations of the chelating carbox-
ylate groups (Δν = 168 cm–1).[22] The IR spectrum of 3
shows a broad νasym(CO2) absorption with a maximum at
1568 cm–1 and a νsym(CO2) absorption at 1404 cm–1, which
can be assigned to the chelating carboxylate group (Δν =
164 cm–1). For polymer 5, the bands of the dicarboxylate
groups appear at 1578 and 1543 cm–1 for the asymmetric
stretching and at 1420 and 1385 cm–1 for the symmetric
stretching. The Δν values are 193 and 123 cm–1 and are at-
tributed to the existence of both monodentate and chelating
modes of the carboxylate groups, respectively. The infrared
spectra of 1–3 and 5 also show broad bands in the 3634–
3230 cm–1 region, which can be assigned to water molecules.
Additionally, complex 1 has a strong band at 1638 cm–1 and
a medium band at 1202 cm–1, which are absent in the IR
spectra of other complexes and are indicative of a chelating
carbonate group.[23]
Description of the Crystal Structures
[Co(bpy)2(CO3)]2(Pht)·16H2O (1)
X-ray analysis indicates that the asymmetric unit of 1
contains two crystallographically independent [Co(CO3)-
(bpy)2]+ cations, a Pht2– anion, and sixteen solvate water
molecules (Figure 1). The structure of the cations is similar
to that in the related compounds [Co(CO3)(bpy)2]-
NO3·5H2O[20] and [Co(CO3)(bpy)2]Cl·3H2O.[27] Each CoIII
atom in 1 is coordinated by four nitrogen atoms of two
chelating bpy molecules and two oxygen atoms of the che-
–
lating CO3 group, and thus adopts a distorted octahedral
N4O2 environment. The average Co–N distances are 1.930
for Co(1) and 1.932 Å for Co(2), while the Co(1)–O bonds
Thermogravimetric Studies
Compounds 1–3, and 5 were heated in the temperature are 1.901(2) and 1.893(2) Å, with 1.895(2) and 1.898(2) Å
range 25–600 °C. The TGA data show that the first weight for the Co(2)–O bonds (Table 1). The observed distortion
loss corresponds to the removal of water molecules in all from an octahedral geometry could be caused by the small
compounds. Complex 1 loses eleven water molecules in two bite angle of the chelating carbonate group [the O–Co–O
steps from 30 to 150 °C (the total weight loss is 15.40%, angles are 69.42(8)° and 69.31(8)° for Co(1) and Co(2),
calculated 15.07%). On further heating, 1 loses 43.88% of respectively]. The O–Co–O bite angle of the chelating car-
its weight between 160 and 270 °C, which corresponds to bonate ligand agrees well with other bis(bipyridine)(carbon-
the release of the five remaining water molecules, the unco- ato)cobalt(iii) [69.9(2)°][20] and (carbonato)bis(phenanthro-
ordinated phthalate dianion (Pht2–), and two bpy molecules line)cobalt(iii) complexes [varies from 68.4(5)° to
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Mono-, Di- and Polynuclear Cobalt(ii) and Cobalt(iii) Coordination Compounds
FULL PAPER
69.8(2)°].[20,28] The dihedral angles between the four-mem- (bpy)2]+ cations. The latter are attached to the channels’
bered chelate ring of the carbonate group and two five- walls by hydrogen bonds [O(4w)–H···O(3CD) = 2.800(3),
membered chelate rings of the bpy ligands are 94.6(1)° and O(8w)–H···O(3AB) = 2.814(3), and O(7w)–H···O(1CD) =
87.0(1)° for Co(1), and 87.0(1)° and 96.5(1)° for Co(2).
2.811(3) Å], as well as by π–π interactions between the Pht
ring and the pyridine ring from the Co(1) complex [the
centroid–centroid distance is 3.562(2) Å].
Figure 1. Crystallographically independent structure fragment with
numbering scheme and displacement ellipsoids drawn at the 30%
probability level in compound 1. Two water molecules are disor-
dered over two positions: O(13w) and O(13*), O(14w) and O(14*).
Hydrogen atoms have been omitted for clarity.
Table 1. Selected bond lengths [Å] and angles [°] for compound 1.
Co(1)–O(1AB)
Co(1)–O(2AB)
Co(1)–N(1A)
Co(1)–N(1B)
Co(1)–N(2A)
Co(1)–N(2B)
O(1AB)–Co(1)–O(2AB)
O(1AB)–Co(1)–N(1A)
O(1AB)–Co(1)–N(1B)
O(1AB)–Co(1)–N(2A)
O(1AB)–Co(1)–N(2B)
O(2AB)–Co(1)–N(1A)
O(2AB)–Co(1)–N(1B)
O(2AB)–Co(1)–N(2A)
O(2AB)–Co(1)–N(2B)
N(1A)–Co(1)–N(1B)
N(1A)–Co(1)–N(2B)
N(1A)–Co(1)–N(2A)
N(1B)–Co(1)–N(2A)
N(1B)–Co(1)–N(2B)
N(2A)–Co(1)–N(2B)
1.901(2)
1.893(2)
1.920(2)
1.926(2)
1.927(2)
1.947(2)
69.42(8)
92.76(9)
88.65(9)
Co(2)–O(1CD)
Co(2)–O(2CD)
Co(2)–N(1C)
Co(2)–N(1D)
Co(2)–N(2C)
Co(2)–N(2D)
O(1CD)–Co(2)–O(2CD) 69.31(8)
O(1CD)–Co(2)–N(1C)
O(1CD)–Co(2)–N(1D)
1.895(2)
1.898(2)
1.922(2)
1.934(2)
1.933(2)
1.937(2)
89.20(9)
91.59(9)
97.66(9)
165.43(8)
92.41(9)
87.95(9)
166.34(9)
96.85(9)
179.21(9)
83.04(9)
96.13(9)
96.77(10)
83.13(9)
96.44(9)
Figure 2. (a) Space-filling representation of channels in the struc-
ture of compound 1. Cations [Co(bpy)2(CO3)]+ have been omitted
for clarity. (b) One channel with a pair of columns formed by
[Co(bpy)2(CO3)]+ cations in 1. Hydrogen atoms have been omitted
for clarity and hydrogen bonds are indicated by dotted lines.
165.96(8) O(1CD)–Co(2)–N(2C)
99.21(9)
88.91(8)
92.53(8)
96.95(9)
O(1CD)–Co(2)–N(2D)
O(2CD)–Co(2)–N(1C)
O(2CD)–Co(2)–N(1D)
O(2CD)–Co(2)–N(2C)
167.92(9) O(2CD)–Co(2)–N(2D)
178.26(9) N(1C)–Co(2)–N(1D)
95.92(9)
83.36(10) N(1C)–Co(2)–N(2D)
95.50(10) N(2C)–Co(2)–N(1D)
82.85(9)
94.61(9)
The cations are arranged in pairs of columns due to π–π
stacking interactions between the antiparallel aromatic
rings belonging to two Co(1) complexes and related by a
symmetrical center at the (1/2, 1/2, 0) site (Figure 2b). The
average contact distance of the adjacent aromatic rings is
about 3.52 Å and the centroid–centroid distance is
N(1C)–Co(2)–N(2C)
N(1D)–Co(2)–N(2D)
N(2C)–Co(2)–N(2D)
Pht2– acts as a fully deprotonated counterion. The 3.780(2) Å. The corresponding distances for analogous pyr-
average dihedral angle between the planes of its carboxylate idine rings of two Co(2) complexes are about 3.77 and
groups is 60.6°, and the angles between the planes of the 3.987(1) Å, respectively, and are slightly longer than those
carboxylate groups and the aromatic ring are 48.8° and for typical aromatic-aromatic π–stacking interactions.[29]
52.1°. The sixteen solvent water molecules and the uncoor- Weak C–H···O hydrogen bonds between the CH groups of
dinated oxygen atoms of the carboxylate groups of the the pyridine rings and the uncoordinated oxygen atoms of
Pht2– anion form a system of hydrogen bonds that generate the CO3 ligands join Co(1) and Co(2) complexes within the
a wall of channels. These channels are extended along the column [C(11C)–H···O(3AB) = 3.226 Å, C(11A)–H···O-
b axis (Figure 2) and are occupied by pairs of [Co(CO3)- (3CD) = 3.215 Å].
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[(bpy)2Co(Pht)H(Pht)Co(bpy)2](HPht)(H2Pht)·2H2O
(2a, 2b)
X-ray diffraction analysis revealed that compound 2
crystallizes in two polymorphic forms: 2a and 2b (Table 2).
The unit-cell parameters of 2a and 2b are related as follows:
a2b Ϸ –(a2a + c2a); b2b Ϸ b2a + c2a – a2a; c2b Ϸ 2(a2a + b2a).
The former (2a) is isostructural with the analogous Zn
complex[14] and also consists of a centrosymmetric dinu-
clear [(bpy)2Co(Pht)H(Pht)Co(bpy)2]+ cation, an HPht–
anion, an H2Pht molecule, as well as two solvate H2O mole-
cules (Figure 3). Each Co atom has a distorted octahedral
geometry containing four nitrogen atoms of two bpy li-
gands (the average Co–N bond length is 2.107 Å) and two
oxygen atoms from one chelating carboxylate group of the
Pht ligand [Co–O 2.112(2) and 2.225(2) Å]. The angle of
the chelating carboxylate group O(3)–Co(1)–O(4) is
60.85(6)°. This value is in good agreement with those of
similar 3d-metal complexes with a 1,3-chelating bidentate
function of the Pht ligand.[10–15] It should be noted that the
coordinated carboxylate group of the Pht residue in 2a is
almost coplanar with the aromatic ring − the dihedral angle
between them is 10.2(1)°; for the second carboxyl group this
angle is equal to 74.1(1)°. The two mononuclear structural
units consisting of one metal ion, two bpy molecules, and
one residue of o-phthalic acid are linked by a very short
symmetric O···H···O hydrogen bond of 2.447(3) Å between
the carboxylate oxygen atoms O(1) and O(1A) into a dimer.
Consequently, the metal-containing backbone can be con-
sidered as a [(bpy)2Co(Pht)H(Pht)Co(bpy)2]+ unit.
Figure 3. Dimeric aggregate in compound 2a. Two configurations
of the uncoordinated molecule of o-phthalic acid with C and D
index are shown. All hydrogen atoms except a symmetric O(1)···
H···O(1A) bond in the dimer have been omitted for clarity.
chains formed by an alternation of neutral H2Pht mole-
The dinuclear aggregate forms a hydrogen-bonded net- cules, water molecules, and monodeprotonated hydrogen
work with water molecules and the uncoordinated molecule phthalate anions (HPht–), as shown in Figure 4. In this
of o-phthalic acid. The position of the hydrogen atoms of case, the inversion centers between two disordered carbox-
the carboxylic groups in the uncoordinated phthalate mole- ylic groups of the neighboring uncoordinated phthalate
cules could not be located because of disorder of oxygen moieties in the chains have a statistical character (Figure 4).
atoms over two orientations with 50% probability. There- Variations of analogous chains have been observed in {[(η6-
fore, we propose a model in which the crystal of 2a contains C6H6)2Cr]+[HPht]–[H2Pht]} as well as in {([(η5-C5H5)2-
Table 2. Selected bond lengths [Å] and angles [°] of the two polymorphic forms of 2 (2a and 2b).
2a
2b
Min value, max value
Average
Co(1)–O(3)
Co(1)–O(4)
Co(1)–N(1A)
Co(1)–N(1B)
Co(1)–N(2A)
Co(1)–N(2B)
O(4)–Co(1)–O(3)
N(1B)–Co(1)–O(4)
N(2B)–Co(1)–O(4)
N(1A)–Co(1)–O(3)
O(4)–Co(1)–N(1A)
N(1B)–Co(1)–N(1A)
N(2B)–Co(1)–N(1A)
N(1B)–Co(1)–O(3)
N(2B)–Co(1)–N(1B)
N(2A)–Co(1)–O(3)
O(4)–Co(1)–N(2A)
N(1A)–Co(1)–N(2A)
N(1B)–Co(1)–N(2A)
N(2B)–Co(1)–N(2A)
N(2B)–Co(1)–O(3)
2.225(2)
2.112(2)
2.119(2)
2.105(1)
2.119(2)
2.086(2)
60.85(6)
96.25(7)
93.64(7)
88.83(7)
92.82(7)
170.88(7)
102.29(8)
94.73(7)
78.14(8)
99.90(7)
159.02(7)
77.61(8)
93.49(8)
106.55(8)
152.91(7)
Co–O(3)
Co–O(4)
Co–N(1A)
Co–N(1B)
Co–N(2A)
Co–N(2B)
O(4)–Co–O(3)
O(4)–Co–N(1B)
N(2B)–Co–O(4)
N(1A)–Co–O(3)
O(4)–Co–N(1A)
N(1B)–Co–N(1A)
N(2B)–Co–N(1A)
N(1B)–Co–O(3)
N(2B)–Co–N(1B)
N(2A)–Co–O(3)
O(4)–Co–N(2A)
N(1A)–Co–N(2A)
N(1B)–Co–N(2A)
N(2B)–Co–N(2A)
N(2B)–Co–O(3)
2.213(2), 2.259(3)
2.099(2), 2.132(2)
2.105(3), 2.142(3)
2.096(3), 2.117(3)
2.108(3), 2.144(3)
2.088(3), 2.103(3)
60.0(1), 60.8(1)
96.4(1), 97.4(1)
93.5(1), 94.3(1)
88.1(1), 90.0(1)
92.4(1), 93.6(1)
170.0(1), 171.0(1)
100.8(1), 102.4(1)
95.0(1), 96.0(1)
77.2(1), 78.3(1)
98.5(1), 101.5(1)
157.2(1), 159.7(1)
76.7(1), 77.6(1)
93.0(1), 94.8(1)
105.2(1), 107.7(1)
152.1(1), 153.6(1)
2.233
2.116
2.121
2.106
2.127
2.095
60.4
96.5
93.9
89.1
93.0
170.5
101.7
95.6
77.7
100.1
158.6
77.1
93.9
106.6
152.8
3122
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Mono-, Di- and Polynuclear Cobalt(ii) and Cobalt(iii) Coordination Compounds
FULL PAPER
Figure 4. One version of a chain in 2a. The molecule of Pht with D index is neutral and another one with C index is monodeprotonated.
Co]+)4([HPht]–)2[Pht]2–}.[30] The neutral molecule of o- carboxylate oxygen atom (3.273 Å) and the oxygen atoms
phthalic acid forms two hydrogen bonds: O(1D)···O(1C) = of the uncoordinated phthalate molecules (3.059 and
2.588(6) Å and O(3D)···O(1w) = 2.582(6) Å. Another con- 3.275 Å for two possible orientations) are also worthy of
former acts as a monoanion with only one short intramo- mention.
lecular hydrogen bond [O(4C)···O(2C) = 2.390(6) Å]. Two
In compound 2b, a small alteration in the crystal struc-
water molecules join pairs of H2Pht–HPht– units into zig- ture increases the unit cell’s volume six times compared with
zag chains through O–H···O hydrogen bonds: O(1w)··· that of 2a. The asymmetric unit of 2b contains six crystallo-
O(1wA) (–x + 1, –y + 2, –z) = 2.690(4) Å, or O(1w)···O(3C) graphically independent CoII complexes, which combine in
= 2.702(6) Å. The dinuclear aggregates are attached on the crystal structure into four [(bpy)2Co(Pht)H(Pht)-
both sides of the chains due to hydrogen bonds [O(1w)– Co(bpy)2]+ units, as shown in Figure 5. Two of them, na-
H···O(2) = 2.795(3) Å].
mely Co(5)–Co(5A) and Co(6)–Co(6A), are centrosymmet-
Other noncovalent forces that contribute significantly to ric, while the others [Co(1)–Co(2) and Co(3)–Co(4)] are
the 3D structural organization of 2a should be mentioned, noncentrosymmetric. A comparison of the main bond
namely aromatic π–π interactions between the uncoordi- lengths and angles in all six Co complexes shows a close
nated phthalate moieties and one of the coordinated bpy similarity between them. The average structural parameters
molecules (with A indexes), with a centroid–centroid dis- of the coordination environment of the Co atoms are listed
tance of 3.754 Å. The angle between the overlapping aro- in Table 2. The maximum dispersion of distances in Co dis-
matic system is 8.3(1)°. There are also π–π stacking interac- torted octahedrons was observed for the Co–O(3) bond
tions between the antiparallel bpy ligands from different lengths, which are in the range 2.259(3)–2.213(2) Å. The
dinuclear aggregates (the dihedral angle between the bpy Co–O(4) bond lengths vary from 2.099(2) to 2.132(3) Å. In
planes being 0°, with a distance between the centroids of the case of Co–N distances, their values are in the range
the bpy rings of 3.748 Å for the A molecules of bpy and 2.088(3)–2.144(3) Å, but the interval of bond lengths for
3.697 Å for B). The uncoordinated phthalate moieties also each bpy molecule is not more than 0.037 Å.
take part in a C–H···π interaction with the B bpy molecule
The crystal structure of 2b is organized in an analogous
[the distance between H(5C) and the centroid of the sur- manner to 2a. Every Co complex has satellite uncoordi-
rounding B ring is 2.646 Å]. Weak C–H···O hydrogen bonds nated phthalate moieties connected to a bpy molecule by a
involving the bpy carbon atoms and both the coordinated πϪπ stacking interaction (the distance between the overlap-
Figure 5. Six crystallographically independent Co complexes, which form four [(bpy)2Co(Pht)H(Pht)Co(bpy)2]+ units in compound 2b.
Hydrogen atoms have been omitted for clarity.
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S. G. Baca et al.
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ping aromatic rings is about 3.76 Å). Six Pht2– anions com- packing in compound 3 are maintained. In all these com-
pensate the charge of the dimeric units and take part in the pounds the coordinated and uncoordinated water molecules
formation of H-bonded chains that are similar to those in form both intramolecular and intermolecular hydrogen
2a (Figure 4). There are four crystallographically indepen- bonds leading to the organization of double-chains.[32] The
dent chains in 2b. The quality and volume of experimental arrangement of these chains mainly depends on the nature
data, as well as the disorder of some carboxylate groups of of the aromatic amine. The presence of supplementary out-
the Pht moieties and water molecules, did not permit the of-sphere water molecules in compound 3 generates a 3D
localization of all the hydrogen atoms in the structure. network held together by O–H···O hydrogen bonds. The
However, the possibility to distinguish both the neutral water molecule O(2w) and the carboxylate oxygen atom
H2Pht and monodeprotonated HPht– anion exists for the O(3) are involved in intramolecular H-bonding [O(2w)–
four molecules. Molecules with indexes 1S and 5S are neu- H···O(3) = 2.831(2) Å] forming a six-membered hydrogen-
tral H2Pht, while 3S and 6S molecules are HPht– anions, bonded Co(1)–O(2w)–H···O(3)–C(22)–O(4)–Co(1) ring
and the chains may be described as –O(1S)–H···O(4w){or (Figure 6). Individual molecules are joined into centrosym-
O(4wЈ)}–H···O(6w){or O(6wЈ)}–H···O(6S)– and –O(5S)– metric dimers by the hydrogen bonds O(2w)–H···O(2)
H···O(2w){or O(2wЈ)}–H···O(1w){or O(1wЈ)}–H···O(3S)–. [2.678(2) Å] and O(3w)–H···O(1) [2.713(2) Å] (symmetry
The distribution of the carboxylic H atom for the two re- code for O(2) and O(3): –x + 1, –y + 1, –z). The Co···Co
maining disordered phthalate moieties (2S and 4S) has sta- distance within the dimer is 7.368(1) Å. These dimeric units
tistical character as in 2a. The dinuclear aggregates are at- are further connected by O(w)–H···O(carb.) and O(w)–
tached on both sides of the chains due to O(w)–H···Ocarb H···O(w) hydrogen bonds into double-chains running along
hydrogen bonds that are in the range 2.79(1)–2.98(1) Å. An the a axis of the unit cell of 3 (Figure 7). The distance be-
additional π–π interaction occurs between the bpy mole- tween the metal centers of the adjacent dimers is
cules of adjacent Co complexes: Co(3) and Co(6), Co(1) 6.698(1) Å. The hydrogen bond O(4w)–H···O(6w) (x, –y +
and Co(5), Co(2) and Co(4).
1/2, z – 1/2) of 2.775(2) Å and possible π–π interactions
An analysis of the charges on the four different supramo- between antiparallel molecules of bpy (the average distances
lecular aggregates consisting of a [(bpy)2Co(Pht)H(Pht)-
Co(bpy)2]+ unit and two satellite uncoordinated phthalate
moieties (monodeprotonated or neutral) shows that the
structure of 2b has four types of supramolecular fragments.
Two of them are formed around the centrosymmetric di-
mers Co(5)–Co(5A) and Co(6)–Co(6A) and have a positive
charge
{(H2Pht)[(bpy)2Co(5)(Pht)H(Pht)Co(5A)(bpy)2]-
(H2Pht)}+ and negative charge {(HPht)[(bpy)2Co(6)(Pht)-
H(Pht)Co(6A)(bpy)2](HPht)}–, respectively. The supramo-
lecular aggregate around Co(1)–Co(2) is statistically neutral
or has charge +1, and the one around Co(3)–Co(4) has a 0
or –1 charge. This effect could explain the increase of the
cell volume in 2b.
[Co(Pht)(bpy)(H2O)3]·3H2O (3)
Compound 3 (Figure 6) may be subsumed to the struc-
tural type [M(Pht)(Amin)(H2O)3]·nH2O [M = Co, Ni; Amin
= one bidentate ligand (bpy, dipya, phen)[19,31] or two
monodentate ligands (Py, β-Pic, 1-MeIm);[32] n = 0, 1, 3].
In all these compounds, the o-phthalic acid residue is fully
deprotonated and acts as a monodentate ligand. The Co
atom in 3 is in a distorted octahedral environment, being
coordinated by two nitrogen atoms from the bpy molecule,
with a Co–N(1) distance of 2.126(1) Å and a Co–N(2) dis-
tance of 2.134(1) Å, the O(4) atom of the monocoordinated
phthalate ligand [2.145(1) Å], and three oxygen atoms of
water molecules [O(1w), O(2w), and O(3w) distances of
2.115(1), 2.112(1), and 2.056(1) Å, respectively] (Table 3).
The water molecules O(1w) and O(2w) are trans to N(1)
and N(2), respectively, whereas O(3w) lies trans to O(4).
Thus, three coordinated water molecules make one edge of
the octahedron, whereas the same coordinated water mole-
Figure 6. Molecular structure of compound 3.
Table 3. Selected bond lengths [Å] and angles [°] for compound 3.
Co(1)–O(4)
Co(1)–N(1)
2.145(1) Co(1)–O(1w)
2.126(1) Co(1)–O(2w)
2.115(1)
2.112(1)
2.056(1)
87.79(5)
97.29(5)
174.13(5)
Co(1)–N(2)
2.134(1) Co(1)–O(3w)
N(1)–Co(1)–O(4)
N(1)–Co(1)–N(2)
N(2)–Co(1)–O(4)
O(3w)–Co(1)–O(4)
O(3w)–Co(1)–N(1)
O(3w)–Co(1)–N(2)
96.46(5) O(2w)–Co(1)–O(4)
77.36(5) O(2w)–Co(1)–N(1)
95.16(5) O(2w)–Co(1)–N(2)
170.06(4) O(2w)–Co(1)–O(3w) 91.17(5)
91.36(5) O(1w)–Co(1)–O(4)
92.53(5) O(1w)–Co(1)–N(1)
81.87(5)
171.32(5)
94.27(5)
O(3w)–Co(1)–O(2w) 85.13(5) O(1w)–Co(1)–N(2)
O(3w)–Co(1)–O(1w) 91.29(5)
cules lie in
a meridian place in the related com-
pounds.[19,30,31] However, the main features of the crystal
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Mono-, Di- and Polynuclear Cobalt(ii) and Cobalt(iii) Coordination Compounds
FULL PAPER
between the overlapping rings are 3.56 and 3.23 Å) link the [O(3)–Co–O(4) = 60.15°; Table 4]. The Co atom is coordi-
double chains into a 3D network (Figure 8).
nated by three oxygen atoms [O(1*), O(3), O(4)] from two
Pht residues [2.141(1), 2.235(2), and 2.076(1) Å], one water
molecule [O(1w) 2.118(1) Å], and two nitrogen atoms [N(1),
N(2)] of a bpy molecule [2.097(1) and 2.127(1) Å]. The
Co···Co distance in this dimer is 5.034(1) Å. Similar dimers
have been described recently in [Zn(Pht)(Im)(H2O)]2,[13] al-
though in this latter complex the Pht ligands exhibit a 1,6-
bridging function and the Zn atoms have a tetrahedral envi-
ronment. A 14-membered cycle is formed in both com-
pounds, but alteration of the structural function of the Pht
residue leads to a shorter transannular distance in 4 [O(4)–
O(4*) = 3.448(2) Å] compared to that in the Zn dimer
[3.964(2) Å].[13]
Figure 7. View of a double-chain in compound 3. Hydrogen atoms
have been omitted for clarity and hydrogen bonds are indicated by
dotted lines.
Figure 9. Discrete dinuclear molecule in compound 4.
Table 4. Selected bond lengths [Å] and angles [°] for compounds 4
and 5.[a]
4
5
Co(1)–O(1)1
Co(1)–O(3)
Co(1)–O(4)
Co(1)–N(1)
Co(1)–N(2)
Co(1)–O(1w)
2.076(1) Co(1)–O(1)2
2.235(2) Co(1)–O(3)
2.141(1) Co(1)–O(4)
2.097(1) Co(1)–N(1)
2.127(1) Co(1)–N(2)
2.118(1) Co(1)–O(1w)
2.054(6)
2.196(5)
2.181(5)
2.151(7)
2.108(6)
2.095(5)
154.8(2)
96.9(2)
85.2(2)
117.8(2)
89.3(2)
60.3(2)
102.7(2)
86.7(2)
139.0(2)
87.3(2)
76.0(2)
111.1(2)
89.5(2)
161.9(2)
91.4(2)
Figure 8. Packing diagram of compound 3. Hydrogen atoms have
been omitted for clarity and hydrogen bonds are indicated by dot-
ted lines.
O(1)1–Co(1)–O(3)
O(1)1–Co(1)–O(4)
O(1)1–Co(1)–N(1)
O(1)1–Co(1)–N(2)
O(1)1–Co(1)–O(1w)
O(3)–Co(1)–O(4)
N(1)–Co(1)–O(3)
N(1)–Co(1)–O(4)
N(1)–Co(1)–N(2)
N(1)–Co(1)–O(1w)
N(2)–Co(1)–O(3)
N(2)–Co(1)–O(4)
O(1w)–Co(1)–O(3)
O(1w)–Co(1)–O(4)
O(1w)–Co(1)–N(2)
165.32(5) O(1)2–Co(1)–O(3)
105.44(5) O(1)2–Co(1)–O(4)
102.49(5) O(1)2–Co(1)–N(1)
91.56(5) O(1)2–Co(1)–N(2)
93.04(5) O(1)2–Co(1)–O(1w)
60.15(5) O(3)–Co(1)–O(4)
92.18(5) N(1)–Co(1)–O(3)
150.90(5) N(1)–Co(1)–O(4)
77.37(5) N(2)–Co(1)–O(4)
93.63(6) N(2)–Co(1)–O(3)
92.23(5) N(2)–Co(1)–N(1)
93.76(5) O(1w)–Co(1)–O(4)
85.35(5) O(1w)–Co(1)–O(3)
92.89(5) O(1w)–Co(1)–N(1)
170.61(5) O(1w)–Co(1)–N(2)
[Co(Pht)(bpy)(H2O)]2·2H2O (4)
A
neutral centrosymmetric dinuclear aggregate
[Co(Pht)(bpy)(H2O)]2 is the main structural unit of com-
pound 4, in which two CoII atoms are linked by two phthal-
ate ligands to form a 14-membered cycle (Figure 9). The
coordination modes of the two deprotonated carboxylate
groups in the Pht residue are different. One carboxylate
group is bidentate to a Co atom, while the other one is
monocoordinated to the adjacent Co atom. The Co atoms
are in a distorted octahedral environment. Deformation of
the CoII coordination polyhedron is observed both in bond
[a] Symmetry transformations used to generate equivalent atoms:
lengths [range from 2.076(1) to 2.235(2) Å] and angles 1: –x + 1, –y, –z + 1; : –x + 2, –y + 1, z + 1/2.
2
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S. G. Baca et al.
FULL PAPER
Both the coordinated and solvate water molecules gener- are joined into a helical polymeric chain (Figure 12). It is
ate an extensive hydrogen-bonding network in 4. The coor- necessary to note that is isostructural with
5
dinated water molecule O(1w) is involved in intermolecular [Zn(Pht)(bpy)(H2O)]n.[33] The coordination polyhedron of
H-bonding [O(1w)–H···O(2) (–x + 1, –y, –z + 1) = the Co atom is composed of the same donor atoms as in 4
2.695(2) Å]. A pair of identical H2O molecules [O(2w)], one and is also distorted. The bond lengths range from 2.054(1)
above and the other below the plane of the 14-membered to 2.196(5) Å and the bond angles from 60.3(2)° to
cycle, which additionally constrict the dimer, form hydrogen 117.8(2)° (Table 4). The Co–O(3) and Co–O(4) bond
bonds as donors with the O(1) atoms of the monocoordin- lengths for the bidentate carboxylate group are similar
ated carboxylate groups [O(2w)–H···O(1) = 2.871(2) Å] and [2.196(5) and 2.181(5) Å], and that is a rather surprising
as acceptors with the coordinated water molecules [O(1w)– result in light of the 1,3-chelating function of the Pht li-
H···O(2w) = 2.722(2) Å]. The second donor function of the gand.[11,14,15] There is a principal difference in the dihedral
O(2w) molecule reduces the organization of layers of dimers
(Figure 10) parallel to the (101) plane. These layers are held
together by π–π interactions between antiparallel bpy mole-
cules with an average deviation of the bpy atoms from the
adjacent ring of 3.41(3) Å.
Figure 10. Packing diagram of compound 4. Hydrogen atoms have
Figure 12. View along the c-axis of the single helical chain in com-
been omitted for clarity and hydrogen bonds are indicated by dot-
ted lines.
pound 5 with bpy wings (a) and Pht wings (b).
[Co(Pht)(bpy)(H2O)]n (5)
The
crystal
structure
of
5
consists
of
[Co(Pht)(bpy)(H2O)] entities (Figure 11) as in 4, but they
Figure 11. A fragment of the helical polymeric chain in compound
5 with the numbering scheme.
Figure 13. Crystal packing of the helical chains in compound 5.
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Mono-, Di- and Polynuclear Cobalt(ii) and Cobalt(iii) Coordination Compounds
FULL PAPER
angles between the planes of the coordinated carboxylate
group and the aromatic ring in compounds 5 and 4. In the
former, this angle is equal to 61.5°, whereas in the latter the
coordinated carboxylate group lies almost in the plane of
the aromatic ring (the dihedral angle is 8°). The second car-
boxylate group of the phthalate dianion is monocoordin-
ated to its adjacent Co atom [Co–O(1) = 2.054(6) Å]. The
tridentate chelate-bridging function of the Pht ligand leads
to the organization of the infinitive helical chain along the
c-axis with a pitch of 8.432 Å (Figure 12). The neighboring
Co···Co distance is 5.546(1) Å, slightly shorter than the
Zn···Zn distance in [Zn(Pht)(bpy)(H2O)]n (5.633 Å)[33]
and much shorter than that in the helix of [Co(Pht)-
(4-MeIm)2]n [6.247(1) Å].[15] The adjacent complexes within
Figure 14. The circles correspond to the temperature dependence
χMT for [(bpy)2Co(Pht)H(Pht)Co(bpy)2](HPht)(H2Pht)·2H2O (2).
A simulation from 5 to 300 K with the parameters[34–36] |D| =
70 cm–1, g = 2.55, and J = –0.1 cm–1 is depicted as a line.
the chain are joined additionally through two O–H···O hy-
drogen bonds between the coordinated water molecule and
carboxylate oxygen atoms O(2) and O(4) of 2.570(8) and
2.760(8) Å, respectively. The chains are held together by van
der Waals interactions (Figure 13).
Magnetic Studies
The temperature dependence of the molar magnetic
susceptibility, χM, of complex 1 indicates a diamagnetic be-
havior. This corresponds to low-spin CoIII (S = 0) ions.
The thermal dependence of χMT (χMT being the product
of the molar magnetic susceptibility and the temperature)
and the simulated curve for a powdered sample of the dinu-
clear complex 2 are shown in Figure 14. The room-tempera-
ture χMT value of 6.0 emuKmol–1 agrees well with the cal-
culated value of 6.0 emuKmol–1 for a high-spin CoII com-
pound (S = 3/2) with g = 2.55.[34] The gradual decrease of
χMT upon lowering the temperature is typical for high-spin
CoII. This decrease of χMT is mainly due to zero-field split-
ting. Below 100 K, a possible weak antiferromagnetic inter-
action between neighboring CoII ions provokes a further
decrease of the χMT values. A simulation within the tem-
perature range 5–300 K with a g-value of 2.55, an axial
zero-field splitting parameter[34,35] of |D| = 70 cm–1, and an
exchange parameter, J, of –0.1 cm–1 gives the best agree-
ment with the experimental data.
Figure 15.
The
temperature
dependence,
χMT,
for
[Co(Pht)(bpy)(H2O)3]·3H2O (3) is depicted as circles. The line cor-
responds to a simulation from 25 to 300 K with the parameters |D|
= 80 cm–1 and g = 2.6.
The room-temperature χMT value of 3.05 emuKmol–1
for compound 3 (Figure 15) agrees quite well with the cal-
culated value of 3.17 emuKmol–1 for a high-spin CoII com-
pound (S = 3/2) with g = 2.6.[34] The gradual decrease of
χMT upon lowering the temperature is typical for high-spin
CoII. This decrease of χMT is mainly due to zero-field split-
ting. A simulation within the temperature range 25–300 K
with the parameters |D| = 80 cm–1 and g = 2.6 reproduces
the experimental data quite well. At lower temperatures, the
measured susceptibility shows a steeper decrease. This is
probably due to weak antiferromagnetic intermolecular in-
teractions between the CoII complexes.
Figure 16. The temperature dependence, χMT, for the chain com-
plex [Co(Pht)(bpy)(H2O)]n (5) is depicted as circles. A simulation
for a single-ion behavior within the temperature range of 100 K to
300 K by using a typical parameter set of |D| = 65 cm–1 and g =
2.45 is shown as a line.
The thermal dependence of χMT of complex 5 is depicted
in Figure 16. Attempts to obtain a satisfactory simulation temperature range of 100 K to 300 K, with a typical param-
for this linear-chain compound of CoII ions were not suc- eter set of |D| = 65 cm–1 and g = 2.45, is depicted in Fig-
cessful. However, only to give an impression of the devia- ure 16. Obviously, intrachain magnetic-exchange interac-
tion from a single ion behavior, a simulation[36] within the tions have a pronounced effect.
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S. G. Baca et al.
FULL PAPER
dried in air. Yield: 4.52 g (62.87% based on bpy). C72H56Co2N8O18
(1439.1): calcd. C 60.09, H 3.92, N 7.79; found C 59.90, H 3.86, N
Conclusions
The reaction of cobalt(ii) anions with o-phthalic acid and
bidentate bipyridine ligands has produced some intriguing
complexes. Complexes of different nuclearity are obtained
depending on the temperature of the reaction: the mononu-
clear [CoIII(CO3)(bpy)2]2(Pht)·16H2O (1) and [Co(Pht)-
(bpy)(H2O)3]·3H2O (3) complexes, the open [(bpy)2Co(Pht)-
H(Pht)Co(bpy)2](HPht)(H2Pht)·2H2O (2) and cyclic dinu-
clear [Co(Pht)(bpy)(H2O)]2·2H2O (4), and polynuclear
[Co(Pht)(bpy)(H2O)]n (5). Moreover, in complex 1 the oxi-
dation of cobalt(ii) to cobalt(iii) ions has occurred. The
structural trends displayed in 1–5 illustrate the extraordi-
narily rich binding abilities of the carboxylate groups of the
o-phthalate ligand and their ability to form extensive hydro-
gen-bonding interactions and build supramolecular archi-
tectures. The variable-temperature magnetic data indicate a
weak antiferromagnetic interaction between neighboring
CoII centers in both the open dinuclear complex 2 and mo-
nonuclear complex 3, whereas complex 1 is a rare example
containing low-spin CoIII (S = 0) ions.
7.59. IR (KBr): ν = 3428br, 3073m, 3035sh, 1717s, 1600vs,
˜
1579vs, 1564sh, 1538s, 1493sh, 1475vs, 1444vs, 1411vs, 1366s,
1315m, 1293m, 1251m, 1177m, 1159m, 1075m, 1059m, 1022s,
796m, 773vs, 736s, 715m, 683w, 650m, 576m cm–1. Single crystals
suitable for diffraction studies were obtained by recrystallization of
2 from a hot aqueous solution.
Synthesis of [Co(Pht)(bpy)(H2O)3]·3H2O (3) and [Co(Pht)(bpy)
(H2O)]n (5). Method A: Cobalt(ii) carbonate (1.18 g) was added to
a hot solution of H2Pht (1.69 g, 10 mmol) and bpy (1.56 g,
10 mmol) in water (50 mL). The resulting mixture was heated at
reflux for 45 min. The precipitated solid was removed by filtration
from the hot solution, and the filtrate allowed to cool to room
temp. Cherry-colored crystalline 5 and large, rose-colored crystals
of 3 suitable for X-ray investigation were collected by filtration af-
ter a week, washed with water and dried in air. The crystals of 3
and 5 were separated by hand. The yields of compounds 5 and 3
were 0.78 g (19.65%) and 0.3 g (12.1%), respectively. An additional
batch of 3 was obtained by keeping the mother filtrate in air for 2
weeks. 3: C18H24CoN2O10 (487.32): calcd. C 44.36, H 4.96, N 5.75;
found C 44.28, H 4.68, N 5.67. IR (KBr): ν = 3230br, 1652sh,
˜
1602vs, 1568vs, 1484s, 1444vs, 1404vs, 1315m, 1250m, 1172m,
1159m, 1104w, 1087m, 1060m, 1023s, 840s, 820s, 764vs, 736vs,
701s, 652s, 632m cm–1. The identity of 5 was established by com-
parison of IR data with the crystallographically characterized pre-
cipitate from Method B, and by elemental analysis (found for com-
pound 5: C 54.11, H 3.45, N 6.84). Method B: A solution of KHPht
(2.04 g, 10 mmol) in 20 mL of water was added to a hot solution
of Co(O2CMe)2·4H2O (2.49 g, 10 mmol) and bpy (1.56 g, 10 mmol)
in 20 mL of MeOH. The resulting cherry-colored solution was
stirred and heated for 1 h. Crystals of compound 5 suitable for X-
ray diffraction studies crystallized after several days, and they were
then filtered off, washed with MeOH, and dried in air. Yield: 3.00 g
(75.6%). C18H14CoN2O5 (397.24): calcd. C 54.43, H 3.55, N 7.05,
Experimental Section
General: All reagents were purchased from commercial sources and
used as received. IR spectra were recorded with a Perkin–Elmer
Spectrum One spectrometer in the region 4000–400 cm–1 using KBr
pellets. TG analyses were carried out with a Mettler-Toledo TA
50 in dry dinitrogen (60 mLmin–1) at a heating rate of 5 °Cmin–1.
Magnetic susceptibility data of powdered samples were collected
with an MPMS Quantum Design SQUID magnetometer (XL-5) in
the temperature range 300–1.8 K and at a field of 1000 G. The
samples were placed in a Saran foil bag and a straw was used as
the sample holder. The output data were corrected for the experi-
mentally determined diamagnetism of the sample holder and the
diamagnetism of the sample calculated from Pascal’s constants. The
program MAGPACK[36] was used to model the experimental mag-
netic susceptibility data.
Co 14.84; found C 54.43, H 3.61, N 6.99, Co 14.80. IR (KBr): ν =
˜
3274br, 3119m, 3078m, 1610s, 1600s, 1578s, 1542vs, 1492s, 1474s,
1446vs, 1420vs, 1384s, 1314m, 1262w, 1252m, 1175m, 1152m,
1085m, 1057m, 1041w, 973w, 921w, 869m, 824m, 815m, 763vs,
737s, 721m, 692s, 651s, 631m, 576w, 456m cm–1. Method C:
Co(O2CMe)2·4H2O (0.25 g, 1 mmol) in 10 mL of MeOH was
added to a hot solution of H2Pht (0.17 g, 1 mmol) and bpy (0.16 g,
1 mmol) in 15 mL of MeOH. The resulting cherry-colored solution
was heated at reflux for 1 h. Water (1 mL) was then added to the
solution and it was allowed to slowly evaporate at room temp. over
3 weeks to give a crystalline precipitate of 5 and several crystals of
4 suitable for diffraction studies. The yield of 5 was 0.25 g (62.5%).
It was further identified by comparison of its IR spectrum with the
crystallographically characterized precipitate from Method B, and
by elemental analysis; found for the title compound 5: C 54.30, H
3.48, Co 14.90, N 7.01.
Synthesis of [Co(CO3)(bpy)2]2(Pht)·16H2O (1): A warm solution of
H2Pht (1.66 g, 10 mmol) and bpy (1.56 g, 10 mmol) in water
(20 mL) was added to a suspension of CoCO3·Co(OH)2·nH2O
(1.18 g) and K2CO3 (1.38 g, 10 mmol) in water (30 mL). The re-
sulting mixture was stirred at 60 °C for 30 min. The precipitated
solid was removed immediately and the filtrate allowed to cool to
room temp. Dark-red crystals of 1 suitable for X-ray diffraction
studies were filtered off after two weeks, and washed with water,
EtOH, and dried in air. Yield: 1.00 g (30.4% based on bpy).
C50H68Co2N8O26 (1315.0): calcd. C 45.67, H 5.21, N 8.52; found
C 45.71, H 5.15, N 8.48. IR (KBr): ν = 3384br, 3116m, 3086m,
˜
X-ray Crystallographic Study: Experimental data for 2a were col-
lected with an Enraf–Nonius CAD4 single-crystal diffractometer
with Cu-Kα radiation at 140 K and were processed using a locally
written program.[37] Experimental data for all other crystals were
obtained with a KUMA KM4CCD-κ-axis diffractometer with
graphite-monochromated Mo-Kα radiation at 130 K for 1, 293 K
3061m, 3032m, 1678vs, 1639s, 1606s, 1563s, 1501m, 1472s, 1449s,
1403s, 1382s, 1318m, 1282w, 1247m, 1202s, 1157m, 1123w,
1109w, 1075w, 1037w, 1025w, 1004w, 822m, 773vs, 751sh, 729s,
692w, 676w, 652m, 509m, 484w cm–1.
Synthesis of [(bpy)2Co(Pht)H(Pht)Co(bpy)2](HPht)(H2Pht)·2H2O
(2): H2Pht (3.32 g, 20 mmol) and bpy (3.12 g, 20 mmol) were added for 2b and 4, 130 K for 3, and at 170 K for 5. The data were pro-
to a suspension of CoCO3·Co(OH)2·nH2O (2.3 g) in water (50 mL).
The resulting mixture was stirred at 80 °C for 10 min. The precipi-
tated solid containing unreacted cobalt(ii) carbonate was removed
immediately and the filtrate allowed to cool to room temp. Large
red crystals were filtered off after a week, washed with water, and
cessed using the KUMA diffraction (Wroclaw, Poland) program.
Crystal data and details of data collection and refinement for 1–5
are given in Table 5. The structures were solved by direct methods
(SHELXS-97)[38] and refined by the full-matrix least-squares
method on F2 (SHELXL-97)[39] with an anisotropic approach for
3128
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 3118–3130

Mono-, Di- and Polynuclear Cobalt(ii) and Cobalt(iii) Coordination Compounds
Table 5. Crystal data and structure refinements of compounds 1–5.
FULL PAPER
1
2a
2b
3
4
5
Empirical formula
Formula mass
Temperature [K]
Wavelength [Å]
Crystal size [mm]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C50H68Co2N8O26 C72H56Co2N8O18 C72H56Co2N8O18 C18H24CoN2O10 C18H16CoN2O6
C18H14CoN2O5
397.24
170(2)
1314.98
1439.10
1439.11
487.32
415.26
130(2)
140(2)
293(2)
130(2)
293(2)
0.71073
1.54178
0.71073
0.71073
0.71073
0.71073
0.7×0.7×0.3
monoclinic
P21/c
0.3×0.4×0.3
triclinic
P1
0.6×0.6×0.3
triclinic
P1
0.8×0.4×0.4
monoclinic
P21/c
0.5×0.5×0.3
monoclinic
P21/n
0.25×0.1×0.05
orthorhombic
Pna21
10.077(2)
19.098(4)
8.432(2)
90
90
90
4, 1.626
1.091
812
¯
¯
14.046(3)
14.693(3)
28.904(6)
90.
91.94(3)
90
10.901(2)
11.690(2)
14.022(3)
111.16(3)
105.79(3).
91.40(3)
15.324(3)
20.702(4)
31.835(6)
104.79(3)
93.45(3)
8.959(2)
18.711(4)
12.757(3)
90
102.57(3)
90.
11.520(2)
13.072(3)
11.957(2)
90
107.25(3)
90
γ [°]
92.95(3)
Z, Dc [gcm–3
]
4, 1.465
0.647
1, 1.504
4.795
6, 1.475
0.594
4, 1.551
0.881
4, 1.604
1.038
μ [mm–1
F(000)
]
2744
742
4452
1012
852
θ range for data coll. [°]
Limiting indices
3.41–25.03
–16 Յ h Յ 16
–17 Յ k Յ 13
–34 Յ l Յ 34
3.54–69.98
0 Յ h Յ 13
–14 Յ k Յ 14
–17 Յ l Յ 16
5951/5951
3.40–25.03
–9 Յ h Յ 18
–24 Յ k Յ 24
–37 Յ l Յ 37
83789/33922
3.45–29.82
–12 Յ h Յ 12
–16 Յ k Յ 25
–17 Յ l Յ 16
23547/5496
3.57–26.37
–11 Յ h Յ 1 4
–16 Յ k Յ 16
–14 Յ l Յ 14
9325/3507
3.79–25.02
–11 Յ h Յ 5
–20 Յ k Յ 22
–10 Յ l Յ 6
4658/2064
Reflections collected/unique 61380/10503
Completeness to θmax
[R(int) = 0.0552] [R(int) = 0]
[R(int) = 0.0389] [R(int) = 0.0395] [R(int) = 0.0189] [R(int) = 0.0704]
99.6%
99.0%
98.7%
91.8%
99.6%
98.8%
Data/restraints/parameters
Goodness-of-fit on F2
10503/52/903
1.021
5951/6/481
1.023
33922/8/2771
1.116
5496/0/376
1.079
3507/0/309
1.058
2064/1/236
1.033
Final R indices [I Ͼ 2σ(I)]
R1 = 0.0491,
wR2 = 0.1389
R1 = 0.0599,
wR2 = 0.1488
0.821/–0.667
R1 = 0.0401,
wR2 = 0.1058
R1 = 0.0489,
wR2 = 0.1102
0.349/–0.661
R1 = 0.0644,
wR2 = 0.1956
R1 = 0.1250,
wR2 = 0.2312
0.465/–0.836
R1 = 0.0346,
wR2 = 0.0831
R1 = 0.0384,
wR2 = 0.0858
0.558/–0.695
R1 = 0.0271,
wR2 = 0.0690
R1 = 0.0301,
wR2 = 0.0714
0.276/–0.270
R1 = 0.0568,
wR2 = 0.1089
R1 = 0.0770,
wR2 = 0.1183
0.459/–0.473
R indices (all data)
Largest diff. peak/hole
[eÅ–3
]
the non-hydrogen atoms for 1, 2a, 3, 4, and 5. The crystals of 2b
have a substructure: Iexp. for hkl reflections with l = 2n ϾϾ Iexp for
hkl with l = 2n + 1. The structure of 2b was refined by using the
Konnert–Hendrickson conjugate-gradient algorithm (CGLS) at the
early stages, and then the blocked full-matrix refinement was per-
formed. Hydrogen atoms were located from the difference synthe-
ses of electronic density, except for H of disordered phthalate moie-
ties and water molecules. Localized hydrogen atoms were included
in the subsequent refinement in the riding-model approximation for
1, 2a, 2b, and 5. For 3 and 4, H-atoms were refined in an isotropic
approximation. CCDC-258617 (1), -258618 (2a), -258619 (2b),
-258939 (3), -258620 (4), and -258621 (5) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Center via www.ccdc.cam.ac.uk/data_request/cif.
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1
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collection of crystallographic data sets for compound 2b.
Eur. J. Inorg. Chem. 2005, 3118–3130
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3129

S. G. Baca et al.
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Received: January 5, 2005
Published Online: June 22, 2005
3130
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 3118–3130