Synthesis, structure, properties and immobilization on a gold surface of the monoribbed-functionalized tris-dioximate cobalt(ii) clathrochelates and an electrocatalytic hydrogen production from H+ ions

Article abstract of DOI:10.1039/c2dt12513g

The cycloaddition of the mono- and dichloroglyoximes to the cobalt(ii) bis-α-benzyldioximate afforded the cobalt(ii) mono- and dichloroclathrochelates in moderate yields (40-60%). These complexes undergo nucleophilic substitution of their reactive chlorine atoms with aliphatic amines, alcohols and thiolate anions. In the case of ethylenediamine and 1,2-ethanedithiol, only the macrobicyclic products with α,α′- N₂- and α,α′-S₂-alicyclic six-numbered ribbed fragments were obtained. The cobalt(ii) cage complexes with terminal mercapto groups were synthesized using aliphatic dithiols. The crystal and molecular structures of the six cobalt(ii) clathrochelates were obtained by X-ray diffraction. Their CoN₆-coordination polyhedra possess a geometry intermediate between a trigonal prism and a trigonal antiprism, and the encapsulated cobalt(ii) ions are shifted from their centres due to the structural Jahn-Teller effect with the Co-N distances varying significantly (by 0.10-0.26 A). The electrochemistry of the complexes obtained was studied by cyclic voltammetry (CV). The anodic waves correspond to the quasi-reversible Co^2+/3+ oxidations, whereas the cathodic ranges contain the quasi-reversibile waves assigned to the Co^2+/+ reductions; all the cobalt(i)-containing clathrochelate anions formed are stable in the CV time scale. The electrocatalytic properties of the cobalt complexes obtained were studied in the production of hydrogen from H⁺ ions: the addition of HClO₄ resulted in the formation of the same catalytic cathodic reduction Co^2+/+ waves. The controlled-potential electrolysis with gas chromatography analysis confirmed the production of H₂ in high Faraday yields. The efficiency of this electrocatalytic process was enhanced by an immobilization of the complexes with terminal mercapto groups on a surface of the working gold electrode.

Full text of DOI:10.1039/c2dt12513g

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Dalton
Transactions
An international journal of inorganic chemistry
www.rsc.org/dalton
Volume 41 | Number 20 | 28 May 2012 | Pages 6005–6320
ISSN 1477-9226
COVER ARTICLE
Voloshin et al.
Synthesis, structure, properties and immobilization on a gold surface of the
monoribbed-functionalized tris-dioximate cobalt(II) clathrochelates and an
electrocatalytic hydrogen production from H+ ions

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PAPER
Synthesis, structure, properties and immobilization on a gold surface of the
monoribbed-functionalized tris-dioximate cobalt(II) clathrochelates and an
electrocatalytic hydrogen production from H+ ions†
Y. Z. Voloshin,*a A. S. Belov,a A. V. Vologzhanina,a G. G. Aleksandrov,b A. V. Dolganov,a V. V. N o v i k o v, a
O. A. Varzatskiic and Y. N. Bubnova
Received 30th December 2011, Accepted 9th March 2012
DOI: 10.1039/c2dt12513g
The cycloaddition of the mono- and dichloroglyoximes to the cobalt(II) bis-α-benzyldioximate afforded
the cobalt(II) mono- and dichloroclathrochelates in moderate yields (40–60%). These complexes undergo
nucleophilic substitution of their reactive chlorine atoms with aliphatic amines, alcohols and thiolate
anions. In the case of ethylenediamine and 1,2-ethanedithiol, only the macrobicyclic products with
α,α′-N2- and α,α′-S2-alicyclic six-numbered ribbed fragments were obtained. The cobalt(II) cage
complexes with terminal mercapto groups were synthesized using aliphatic dithiols. The crystal and
molecular structures of the six cobalt(II) clathrochelates were obtained by X-ray diffraction. Their
CoN6-coordination polyhedra possess a geometry intermediate between a trigonal prism and a trigonal
antiprism, and the encapsulated cobalt(II) ions are shifted from their centres due to the structural
Jahn–Teller effect with the Co–N distances varying significantly (by 0.10–0.26 Å). The electrochemistry
of the complexes obtained was studied by cyclic voltammetry (CV). The anodic waves correspond to the
quasi-reversible Co2+/3+ oxidations, whereas the cathodic ranges contain the quasi-reversibile waves
assigned to the Co2+/+ reductions; all the cobalt(I)-containing clathrochelate anions formed are stable in
the CV time scale. The electrocatalytic properties of the cobalt complexes obtained were studied in the
production of hydrogen from H+ ions: the addition of HClO4 resulted in the formation of the same
catalytic cathodic reduction Co2+/+ waves. The controlled-potential electrolysis with gas chromatography
analysis confirmed the production of H2 in high Faraday yields. The efficiency of this electrocatalytic
process was enhanced by an immobilization of the complexes with terminal mercapto groups on a surface
of the working gold electrode.
these frameworks, the ribbed substituents significantly affect
Introduction
both the geometry and the electronic structure of the cage com-
plexes.4 This type of functionalization (in particular, by six
The possibility to encapsulate a cobalt ion in three oxidation
states (from +11 and +21,2 to +31c,2a,b,e,3) using the macrobicyc-
strong electron-withdrawing halogen substituents in three
lic tris-dioximate ligands is mainly governed by the variation of
the functionalizing substituents with different electromeric
characteristics (i.e., the electron-donating or the electron-with-
drawing ones) in the ribbed chelate fragments of their rigid
highly π-conjugated polyene frameworks.1a,c,2e In contrast to the
apical substituents in the capping (cross-linking) fragments of
α-dioximate fragments) allowed obtainment of efficient electro-
catalysts for the production of molecular hydrogen from H+ ions
without overpotential. This was done by fine tuning the potential
of the encapsulated redox couple Co2+/+ to that of the cathodic
2H+/H2 process with HClO4 as a source of these ions.5 At the
same time, the use of monoribbed-functionalized clathrochelates,
with the functionalizing substituent(s) in one of the three chelate
moieties of the macrobicyclic ligand, seems to be a promising
tool for an efficient hydrogen production in other electrocatalytic
systems, as well as for the immobilization of the clathrochelate
electrocatalysts on a surface of the working electrode. For
example, in the case of the iron(II) clathrochelates, the immobi-
lized complexes of this type have been used as mediators of the
electron transfer for amperometric determination of hydrogen
peroxide,6 whereas their mixed self-assembled monolayers with
1-dodecanethiol have been studied as potent molecular
switches.7 Moreover, the monoribbed-functionalized cobalt(II)
aA. N. Nesmeyanov Institute of Organoelement Compounds of the
Russian Academy of Sciences, 119991 Moscow, Russia.
E-mail: voloshin@ineos.ac.ru; Fax: +7-499-135-50-85
bN. S. Kurnakov Institute of General and Inorganic Chemistry of the
Russian Academy of Sciences, 119991 Moscow, Russia
cV. I. Vernadskii Institute of General and Inorganic Chemistry of the
National Academy of Sciences of Ukraine, 03680 Kiev, Ukraine
†Electronic supplementary information (ESI) available: The UV-vis
spectral data, the CVs figures and the examples of the EPR spectra for
the compounds studied. CCDC 860524–860529. For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/
c2dt12513g
6078 | Dalton Trans., 2012, 41, 6078–6093
This journal is © The Royal Society of Chemistry 2012

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Scheme 1 The possible pathways to the monoribbed-functionalized tris-dioximate cobalt(II) clathrochelates.
clathrochelates are prospective paramagnetic tags for studying
the structure of various biological systems. Here, we report the
synthetic pathways to the monoribbed-functionalized cobalt(II)
clathrochelates as well as the preparation of their mono- and
dichloroclathrochelate precursors and the nucleophilic substi-
tutions leading to the target cage compounds (including those
with the terminal reactive groups). Their X-ray structures, spec-
tral, magnetochemical, electrochemical and electrocatalytical
properties (including those for the gold-immobilized cobalt(II)
complexes) are also reported.
Earlier,10 we synthesized the aliphatic and aromatic cobalt(II)
clathrochelates with nonequivalent chelate α-dioximate frag-
ments using one-pot condensation of the nonmacrocyclic cobalt
(III) bis-dioximates with the corresponding aliphatic and aromatic
α-dioximes and with BF3·O(C2H5)2 as a Lewis acid (capping
agent), as well as the in situ reduction of the Co3+ ion to the
Co2+ ion with metallic silver or copper(I) salts. Unfortunately, we
have failed to obtain the target clathrochelate cobalt(II)-contain-
ing precursors using the similar synthetic procedures. Therefore,
we obtained the cobalt(II) bis-α-benzyldioximate in an inert
atmosphere; it should be noted that all the nonmacrocyclic and
macrocyclic cobalt(II) bis-dioximates are easy to oxidize. The
cycloaddition of the mono- and dichloroglyoximes to these com-
plexes was performed only in severe conditions with boiling
nitromethane as a solvent, giving the cobalt(II) mono- and
dichloroclathrochelates CoBd2(HGmCl)(BF)2 and CoBd2-
(Cl2Gm)(BF)2 (where Bd2−, HGmCl2− and Cl2Gm2− are α-ben-
zyldioxime, monochloroglyoxime and dichloroglyoxime dia-
nions, respectively) in moderate yields (40–60%, Scheme 2).
As the clathrochelate precursors, these complexes easily
undergo nucleophilic substitution of their reactive chlorine atoms
with N,S-nucleophiles (i.e., the primary aliphatic amines and the
thiolate anions) in the presence of strong organic bases using
dichloromethane as a solvent (Scheme 3). In the case of the sec-
ondary aliphatic amines, only one of the two chlorine atoms of
the dichloroclathrochelate precursor undergoes nucleophilic sub-
stitution. A similar result was described earlier for its iron(II)-
containing analog.8,11 In the case of ethylenediamine and 1,2-
ethanedithiol as the bifunctional nucleophiles with short spacer
fragments, only the macrobicyclic products with α,α′-N2 and
α,α′-S2 alicyclic six-numbered ribbed fragments (Scheme 3)
were obtained: variation in the order of addition of the reaction
components as well as the use of a large excess of these nucleo-
philic agents gave no ribbed-functionalized complexes with
terminal amino or mercapto groups. In contrast, we synthesized
the cobalt(II) clathrochelates with terminal mercapto groups
using the cobalt(II) monochloroclathrochelate as a precursor and
the aliphatic dithiols as the nucleophilic agents (Scheme 3).
Results and discussion
Similar to the analogous iron(II) macrobicycles,8 the mono-
ribbed-functionalized tris-dioximate cobalt(II) clathrochelates
may be obtained through various pathways, as shown in
Scheme 1. However, as described earlier,9 the direct template
condensation of a mixture of the corresponding α-dioximes with
Lewis acids on metal ion matrix (Route I) leads to the formation
of four clathrochelate products, mainly the C3-symmetric macro-
bicyclic complexes with equivalent chelate α-dioximate frag-
ments. The cycloaddition of the preliminarily functionalized
α-dioximes to the macrocyclic bis-dioximate (Route II) is hin-
dered due to both the side reactions of the functionalizing substi-
tuents and their coordination to the central metal ion.8 Moreover,
this pathway is based on the synthesis of the corresponding func-
tionalized α-dioxime for each type of functionalizing group.
Hence, as in the case of the monoribbed-functionalized iron(II)
clathrochelates,8 the most reliable and convenient route to the
analogous cobalt(II) complexes is through the synthesis of the
reactive mono- and dihalogen-containing clathrochelate precur-
sors with an encapsulated cobalt(II) ion (Route III). This first
stage is followed by their functionalization with different nucleo-
philic agents. In contrast to the nonmacrocyclic, macrocyclic and
macrobicyclic iron bis- and tris-dioximates, which are stable
only in the case of the 2+ oxidation state of an encapsulated
metal ion, the analogous cobalt complexes may be preparatively
isolated with a cobalt ion in two (2+ and 3+) oxidation states.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 6078–6093 | 6079

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Scheme 2 Synthesis of the cobalt(II) mono- and dichloroclathrochelate precursors.
Scheme 3 Synthesis of the monoribbed-functionalized cobalt(II) clathrochelates.
6080 | Dalton Trans., 2012, 41, 6078–6093 This journal is © The Royal Society of Chemistry 2012

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These complexes undergo side decomposition and oxidation
reactions on silica gel during their chromatographic isolation.
Note that the chlorine-containing cobalt(II) clathrochelates
easily undergo the side reduction reaction with amines and thio-
late anions as the reductants, resulting in the formation of the
corresponding cobalt(I) complexes, which are less thermodyna-
mically stable.1 The partial destruction of their clathrochelate fra-
meworks leads to the formation of the cobalt(II) bis-dioximates
and resulted in a decrease in the yields of the target monoribbed-
functionalized cobalt(II) clathrochelates.
The earlier elaborated12 approach to the functionalization of
the iron(II) macrobicyclic precursors in the case of the low-active
nucleophilic agents involves the use of cadmium(II) amides as
promoters of the nucleophilic substitution. This approach was
also successfully used for the functionalization of the halogen-
containing cobalt(II) clathrochelates: the nucleophilic substitution
of the precursor CoBd2(Cl2Gm)(BF)2 with n-butanol in the pres-
ence of hexamethyldisilazane cadmium(II) amide Cd(HMDSA)2
afforded the monoribbed-functionalized di-n-butoxy-containing
cobalt(II) macrobicycle (Scheme 3).
Fig. 1 General view of the dichloroclathrochelate precursor
CoBd2(Cl2Gm)(BF)2. Hydrogen atoms are omitted for clarity.
As the interpretation of the NMR spectra of the cobalt(II) cla-
throchelates was complicated by the paramagnetic character of
an encapsulated metal ion, the 2D pulse sequences COSY and
1
HMQC were used to assign the signals in their H and 13C{1H}
NMR spectra. The values of the paramagnetic shifts are quite
low, and the interpretation of the results in terms of the spin
density is not straightforward. However, the observed directions
of the paramagnetic shifts and their values are characteristic of
the low-spin cage cobalt(II) compounds.1c Additionally, the low-
spin character of these macrobicycles was confirmed by SQUID
magnetometry data: the values of the magnetic moment, μeff, in
the temperature range studied (5–400 K) were close to the spin-
only value for the low-spin complexes with the electronic
configuration d7 (s = 1/2).
The glassy EPR spectra at 80 K are characteristic of the low-
spin cobalt(II) complexes with a Jahn–Teller distortion.10 Both
g- and hyperfine tensors are rhombic, and the spectra contain
well-resolved splittings in the downfield region caused by the
hyperfine interactions with the 59Co nucleus (ICo = 7/2). Surpris-
ingly, the spectra lineshape strongly depended on the microwave
power used (see ESI, Fig. ESI1†). The tendency to saturation
has not been observed previously for the triribbed-functionalized
cobalt(II) clathrochelates1c and can be attributed to the lower
symmetry of the compounds obtained and the related preference
for one of their three possible Jahn–Teller distortions.
Fig. 2 General view of the monochloroclathrochelate precursor
CoBd2(HGmCl)(BF)2. Hydrogen atoms (except the methine one) are
omitted for clarity.
octahedral one is energetically preferable for the electronic
configurations d6 and d7, whereas the rigidity of the boron-con-
taining capping groups and the sterical hindrances between the
substituents in ribbed chelate fragments of the clathrochelate fra-
meworks cause a trigonal prismatic (TP) distortion of this geo-
metry (the distortion angle ϕ of a MN6-coordination polyhedron
is equal to 0° for a TP and to 60° for a TAP). Indeed, the average
bite angles, α, vary in a very narrow range from 38.5 to 38.9°,
whereas the ϕ angles are from 9.4 to 23.5°, and an increase in
their values is accompanied by a decrease in h from 2.44 to
2.37 Å (Table 1). Thus, the CoN6-coordination polyhedra
possess a geometry that is intermediate between a TP and a TAP.
The Shannon radius of the low-spin Co2+ ion is much greater
than that of the low-spin Fe2+ ion, leading to the elongation –
The structures of the clathrochelates CoBd2(Cl2Gm)
(BF)2·C7H16, CoBd2(HGmCl)(BF)2·2CHCl3, CoBd2((n-C4H9-
NH)2Gm)(BF)2·CH2Cl2, CoBd2(((C2H5)2N)GmCl)(BF)2·C6H6,
CoBd2(S2-Nx)(BF)2 and CoBd2((n-C4H9O)2Gm)(BF)2·2C6H6
were studied by X-ray diffraction (Fig. 1–6); their main geo-
metrical parameters are listed in Table 1. Typically, the geometry
of the boron-capped clathrochelate complexes is mainly gov-
erned by the nature of the encapsulated metal ion and that of
their ribbed substituents.13 The rigidity of the chelate NvC–
CvN fragments causes the bite angles, α (half of the chelate N–
M–N angles), to persist, whereas the heights, h, of the MN6-
coordination polyhedra are affected by the distortion of the
macrobicyclic frameworks around their C3-pseudoaxes. The tri-
gonal antiprismatic (TAP) geometry that is close to the
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 6078–6093 | 6081

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Fig. 6 General view of the clathrochelate CoBd2(S2-Nx)(BF)2. Hydro-
gen atoms are omitted for clarity.
Fig. 3 General view of the clathrochelate CoBd2((n-C4H9O)2Gm)
(BF)2. Hydrogen atoms are omitted for clarity.
example, the ϕ and h values for the cobalt(II) clathrochelates
CoBd2(Cl2Gm)(BF)2 (10.6° and 2.44 Å) and CoBd2((n-
C4H9O)2Gm)(BF)2 (14.7° and 2.42 Å) are significantly different
from those for the iron(II) complexes FeBd2(Cl2Gm)(BF)2 (24.9°
and 2.33 Å)8 and FeBd2((n-C4H9O)2Gm)(BF)2 (25.3° and
2.31 Å), respectively.12
At the same time, the amine macrobicycles CoBd2-
(((C2H5)2N)GmCl)(BF)2 and CoBd2((n-C4H9NH)2Gm)(BF)2 are
more TAP-distorted (ϕ = 18.7 and 23.5°) in comparison with
other monoribbed-functionalized cobalt(II) clathrochelates. In the
previously described mono- and diamine monoribbed-functiona-
lized iron(II) complexes FeBd2(((C2H5)2N)GmCl)(BF)2,8
FeBd2((TempoNH)GmCl)(BF)2, FeBd2((TempoNH)2Gm)(BF)2
(where Tempo is 2,2,6,6-tetramethylpyperidinyl-1-oxyl14),
FeBd2(((CH3)2N)Gm(NH2))(BF)2,15
FeBd2((tert-C4H9NH)2Gm)(BF)2
FeBd2(Im2Gm)(BF)2,16
and FeBd2((CH3OOCC6-
Fig. 4 General view of the clathrochelate CoBd2((n-C4H9NH)2Gm)
(BF)2. Hydrogen atoms are omitted for clarity.
17
H4NH)2Gm)(BF)2,12 these values are equal to 26.6, 25.8, 27.5,
26.6, 24.2, 26.9 and 26.1°, respectively. Therefore, the amine
monoribbed-functionalized iron(II) clathrochelates are also more
TAP-distorted than their halogen-containing macrobicyclic pre-
cursors, although the difference in their ϕ values is only ∼2° in
comparison with those for the analogous cobalt(II) clathroche-
lates (7–12°).
An important feature of the low-spin cobalt(II) clathrochelates
is a shift of the encapsulated metal ion from the centre of its N6-
coordination polyhedron, which is caused mainly by the struc-
tural Jahn–Teller effect; this shift is characteristic of the low-spin
electronic configuration d7.1c As it can be seen from Table 1, the
Co–N distances vary significantly (by 0.10–0.26 Å), whereas
those in FeBd2(Cl2Gm)(BF)2, FeBd2(((C2H5)2N)GmCl)(BF)2
and FeBd2((n-C4H9O)2Gm)(BF)2 are rather close (the differences
do not exceed 0.01 Å). The encapsulated cobalt and iron(II) ions
in their monoribbed-functionalized clathrochelates are shifted in
the direction of the α-benzyldioximate chelate fragments. As a
result, the M–N distances for the functionalized chelate frag-
ments are the largest. Thus, the direction of the displacement of
an encapsulated cobalt(II) ion from the center of its coordination
polyhedron seems to be governed mainly by the electronic
effects of the nonequivalent chelate fragments, whereas the
crystal packing effects cause a distortion of the clathrochelates
Fig. 5 General view of the clathrochelate CoBd2(((C2H5)2N)GmCl)
(BF)2. Hydrogen atoms are omitted for clarity.
expansion of the encapsulating macrobicyclic ligands, as well as
to the decrease in ϕ and to the increase in h for all the cobalt(II)
complexes compared to their iron(II)-containing analogs. For
6082 | Dalton Trans., 2012, 41, 6078–6093
This journal is © The Royal Society of Chemistry 2012

Table 1 The main geometrical parameters of the monoribbed-functionalized cobalt clathrochelates obtained and their analogs
CoBd2
(Cl2Gm)
(BF)2
CoBd2
(HGmCl)
(BF)2
CoBd2 ((n-
C4H9NH)2Gm)
(BF)2
CoBd2
(((C2H5)2N)
GmCl)(BF)2
CoBd2 ((n-
CoBd2 (S2- C4H9O)2Gm)
FeBd2
FeBd2((n-
FeBd2
(((C2H5)2N)
GmCl) (BF)2
CoBd2 Dm (Cl2Gm)
C4H9O)2Gm)
10
8
12
8
Parameter
Nx) (BF)2
(BF)2
(BF)2
(BF)2
(BF)2
Metal ion
M–N(1)
(Å)
M–N(2)
(Å)
M–N(3)
(Å)
M–N(4)
(Å)
M–N(5)
(Å)
M–N(6)
(Å)
Co2+
Co2+
Co2+
1.950(3)
Co2+
Co2+
1.917(3)
Co2+
Co2+
Fe2+
Fe2+
Fe2+
1.907(3)
2.132(3)a
2.107(6)a
2.117(6)a
2.113(2)a
2.014(9)
2.003(9)
1.918(9)
1.927(9)
1.978(9)a
1.942(9)a
1.912(1)a
1.914(1)a
1.906(1)
1.909(1)
1.909(1)
1.906(1)
1.968(6)a
2.142(3)a
1.904(3)
1.886(3)
1.890(3)
1.900(3)
2.145(6)a
1.920(5)
1.897(5)
1.886(5)
1.903(5)
1.866(3)
2.059(6)a
1.902(5)
1.941(4)
1.926(5)
1.883(4)
1.894(3)
1.931(3)
1.952(4)
2.083(4)a
2.093(3)a
2.114(2)a
1.887(2)
1.910(2)
1.928(2)
1.897(2)
1.908(6)a
1.890(6)
1.897(5)
1.899(6)
1.884(6)
1.912(3)
1.919(4)*
1.912(3)
1.902(4)
1.919(3)*
1.876(3)
1.916(3)
2.061(3)a
2.136(3)a
B–O (Å)
1.471(4)–
1.500(4)
av. 1.486
1.358(4)–
1.374(4)
av. 1.365
1.275(4)–
1.318(4)
av. 1.301
1.481(8)–
1.492(9)
av. 1.485
1.359(6)–
1.370(6)
av. 1.364
1.276(9)–
1.307(7)
av. 1.295
1.448(8)–
1.476(9)
av. 1.459
1.354
1.467(5)–1.498(5)
1.448(12)–1.521
(7)
av. 1.492
1.487(3)–
1.504(7)
av. 1.486
1.467(3)–1.500(3) 1.461(14)– 1.479(2)–
1.464(9)–1.502(9) 1.467(7)–1.493(7)
1.541(15)
av. 1.495
1.493(2)
av. 1.486
av. 1.485
1.361(4)–1.419(4)
av. 1.484
av. 1.477
av. 1.482
N–O (Å)
1.357(6)–1.389(7) 1.354(4) –
1.361(2)–1.389(2) 1.363(10)– 1.362(2)–
1.374(7)–1.409(7) 1.358(5)–1.383(5)
1.371(5)
1.396(10)
av. 1.373
1.375(2)
av. 1.375
av. 1.391
1.291(5)–1.315(4)
av. 1.369
1.266(11)–1.330
(7)
av. 1.308
1.443(8)–1.458
(11)
av. 1.452
1.356
18.7
av. 1.364
1.287(6) –
1.314(5)
av. 1.301
1.445(7) –
1.478(7)
av. 1.462
1.353
av. 1.372
av. 1.388
av. 1.371
CvN (Å)
1.279(3)–1.309(3) 1.266(13)– 1.299(2)–
1.249(8)–1.336(8) 1.299(6)–1.317(6)
1.321(14)
av. 1.297
1.316(2)
av. 1.308
av. 1.302
1.469(5)–1.489(5)
av. 1.298
av. 1.308
av. 1.308
Chelate C– 1.451(4)–
C (Å)
1.452(3)–1.487(3) 1.462(14)– 1.435(2)–
1.455(9)–1.491(9) 1.434(6)–1.458(6)
1.481(4)
av. 1.460
1.473(14)
av. 1.467
1.355
1.460(2)
av. 1.449
1.358
24.9
av. 1.473
1.373
23.5
38.9
2.37
av. 1.468
1.364
14.7
av. 1.468
1.367
25.3
av. 1.445
1.355
25.0
av. B–F (Å) 1.364
ϕ (°)
α (°)
h (Å)
10.6
38.5
2.44
11.7
38.8
2.44
9.4
38.6
2.45
12.3
38.8
2.41
38.5
2.42
38.6
2.42
39.3
2.33
39.1
39.1
2.31
2.32
a The distances for the functionalized ribbed fragments.

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with equivalent α-dioximate moieties as well as of the com-
plexes with similar ribbed substituents.
four coordination bonds between an encapsulated cobalt(II) ion
and the α-benzyldioximate fragments.
Another feature of the monoribbed-functionalized cobalt(II)
clathrochelates is a tendency of the dihedral C–CvN angles in
their chlorine- and oxygen-containing chelate fragments to have
larger values (approximately 114°) compared to those in the
phenyl- and amine-containing ribbed moieties (approximately
111°). The average tilt angles of the phenyl substituents to each
other for the same chelate fragment are approximately 59
and 53° in the monoribbed-functionalized cobalt(II) clathroche-
lates and their chlorine-containing macrobicyclic precursors,
respectively.
The solution spectra of the monoribbed-functionalized
cobalt(II) clathrochelates are substantially different from those
for the corresponding pseudo-C3-symmetric boron-capped cobalt
(II) tris-α-benzyldioximates and triribbed-functionalized α-dioxi-
mates, as well as from those for their iron(II)-containing analogs.
A number of bands in the visible region of these spectra (two or
three) assigned to the charge transfer bands (CTBs) Co d → L
π* persist, whereas the directions of their shifts resulted from
functionalization (a nucleophilic substitution) are opposite. In
contrast, functionalization of the iron(II) di- and hexachlorocla-
throchelates and the hexachlorine-containing cobalt(II) macrobi-
cyclic precursors with N,S-nucleophiles led to the substantial
longwave shifts of their CTBs and, in several cases, caused new
bands to appear.1c,4,8
The spectra of these complexes in the UV region contain
highly intense bands assigned to the intraligand π–π* transitions
in the α-dioximate chelate fragments. It should be noted that the
total number of bands for the monoribbed-functionalized cobalt
(II) clathrochelates is higher than that for their triribbed-functio-
nalized analogs (see ESI, Table ESI1†). This fact may be
explained by a decrease in the symmetry of the cage molecules
due to a nonequivalence of their ribbed chelate fragments.
The electrochemical characteristics of the acetonitrile solutions
of the cobalt(II) clathrochelates with nonequivalent α-dioximate
chelate fragments were studied by cyclic voltammetry (CV)
using a glassy carbon (GC) working electrode. As it follows
from the linear plot Ip versus v1/2 (where v is scan rate), all
waves in their CVs are characteristic of the current diffusion-con-
trolled processes in steady-state conditions; the oxidation and
reduction potentials are listed in Table 2.
Despite the fact that the molecular geometries of these clathro-
chelates in some respects are alike, their crystal packings are sig-
nificantly different. In the crystals of the clathrochelate
precursors CoBd2(HGmCl)(BF)2·2CHCl3 and CoBd2(Cl2Gm)
(BF)2·C7H16, numerous Cl⋯F, Cl⋯π, C–H⋯π and Cl⋯H–C
interactions are observed, whereas in the crystal CoBd2((n-
C4H9NH)2Gm)(BF)2·CH2Cl2, each of the clathrochelate mol-
ecules is involved in two contacts {N7–H⋯F1 with ri(H⋯F) =
2.917(4) Å and N8–H⋯O6 with ri(H⋯O) = 3.001(4) Å; ∠N7–
H–F1 = 156° and ∠N8–H–O6 = 140°, respectively} with one of
the neighboring macrobicyclic entities (Fig. 7). Thus, infinite
chains parallel to the crystallographic axis c are observed in this
crystal. In the crystal CoBd2(((C2H5)2N)GmCl)(BF)2·C6H6,
there are hydrogen-bonded five-membered rings H21A⋯O1–N1
= C1–Cl1 {ri(H⋯Cl) = 2.90 Å and ri(H⋯O) = 2.57 Å;
∠C–H⋯Cl = 120° and ∠C–H⋯O = 174°}. The crystal structure
of the complex CoBd2((n-C4H9O)2Gm)(BF)2·2C6H6 contains a
number of contacts C–H⋯π, C–H⋯F and C–H⋯O. The phenyl
substituents in one of the two α-benzyldioximate chelate frag-
ments of the clathrochelate CoBd2((n-C4H9O)2Gm)(BF)2 are
located between two phenyl groups of the same chelate frag-
ments of the neighboring macrobicyclic molecule; so the short
contacts H30A⋯C5, H30A⋯N5 and even H30A⋯Co1 with ri
= 2.87, 2.65 and 3.10 Å, respectively, are observed. The redistri-
bution of the electron density through these interactions may be
the reason why the Co1–N5 distance is the largest among the
The anodic waves with current ratio of the direct and reverse
waves equal to 1 in the CVs of the complexes CoBd2(HGmCl)
(BF)2, CoBd2(Cl2Gm)(BF)2 and CoBd2(((C2H5)2N)GmCl)(BF)2
correspond to the one-electron processes assigned to the cobalt-
centered Co2+/3+ oxidations (Fig. 8, Table 2). As it can be seen
from Table 2, their potentials depend on the electromeric charac-
teristics of the substituents in the functionalized chelate α-dioxi-
mate fragment of the corresponding macrobicyclic ligand
and shift in the negative range with a decrease of their
Hammett σpara constants. Indeed, the dichloroclathrochelate
CoBd2(Cl2Gm)(BF)2 is the most difficult to oxidize. As it was
expected, the oxidation potential is much lower for the mono-
chlorine-containing precursor CoBd2(HGmCl)(BF)2 than that for
the cobalt(II) dichloroclathrochelate. Nucleophilic substitution of
one of its two chlorine atoms by a strong electron-donating
diethylamine substituent leads to a further decrease in the
Co2+/3+ oxidation potential. The differences ΔE = Ea − Ec ,
p
p
which characterize the reversibility of the redox processes, are
equal to 120 and 90 mV for the clathrochelates CoBd2(HGmCl)
(BF)2 and CoBd2(Cl2Gm)(BF)2, respectively. These values are
typical of the quasi-reversible redox processes accompanied by
negligible structural changes in the clathrochelate framework. In
the case of the clathrochelate CoBd2(((C2H5)2N)GmCl)(BF)2
with electron-donating ribbed diethylamine substituent, the ΔE
value is much lower (70 mV) and close to that of a reversible
one-electron process (56 mV18). The quasi-reversible character
of the oxidation processes in the case of the complexes
Fig. 7 The hydrogen-bonded chains in the crystal CoBd2((n-
C4H9NH)2Gm)(BF)2·CH2Cl2. Hydrogen atoms that are not involved in
this bonding are omitted for clarity. The N–H⋯O and N–H⋯F inter-
actions are depicted as dashed lines.
6084 | Dalton Trans., 2012, 41, 6078–6093
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Table 2 The oxidation (Eox) and reduction (Ered) potentials (mV) and characteristics of the electrochemical processes for the cobalt(II)
clathrochelates synthesized and their analogs
Oxidation
Ea Ec
Reduction
a
c
a
Complex
σpara
av. σpara
ΔE
Ic/Ia
Ep
Ep
ΔE
Ic/Ia
p
p
CoBd2(HGmCl)(BF)2
0 (H)
0.227 (Cl)
0.031
740
620
120
1
–370
−305
65
1
−0.01 (Ph)
CoBd2(Cl2Gm)(BF)2
0.227 (Cl)
0.069
920
460
620
630
830
400
550
570
90
60
70
60
1
1
1
1
−310
−570
−450
−390
−250
−470
−350
−300
60
1
1
1
1
−0.01 (Ph)
CoBd2((n-C4H9NH)2Gm)(BF)2
CoBd2((n-C12H25S)2Gm)(BF)2
CoBd2(HGm(SCH2CH2SH))(BF)2
−0.65 (n-C4H9NH)
−0.01 (Ph)
−0.223
−0.009
−0.008
100
100
90
−0.007(SCH2CH2)
−0.01 (Ph)
0 (H)
−0.007 (SCH2CH2)
−0.01 (Ph)
920
600
Irreversible
540 60
CoBd2(HGm(SCH2CH2SCH2CH2SH))(BF)2
0 (H)
−0.008
1
−410
−310
100
1
−0.007 (SCH2CH2)
−0.01 (Ph)
970
Irreversible
1d
Co(Cl2Gm)3(Bn-C4H9)2
Co(Cl2Gm)3(BC6H5)2
CoBd2((C2H5)2NGmCl)(BF)2
0.227
0.227
0.227
−0.127
1130
1170
570
1020
1060
500
110
110
70
0.85
0.90
0.95
−260
−270
−460
−200
−210
−365
60
60
95
1
1
1
1d
0.227
−0.95 ((C2H5)2N)
0.227 (Cl)
−0.01 (Ph)
CoBd2(S2-Nx)(BF)2
CoBd2(N2-Nx)(BF)2
−0.007 (SCH2CH2)
−0.01 (Ph)
−0.009
−0.427
550
510
490
445
60
65
1
1
−430
−560
−350
−465
80
95
1
1
−0.63 (NCH2CH2)
−0.01 (Ph)
a Hammett σpara constants for the substituents in α-dioximate fragments. av. σpara = [n/(m + n)]σ1 + [m/(m + n)] σ2.
CoBd2(N2-Nx)(BF)2 with electron-donating functionalizing sub-
stituents are reversibly oxidized with ΔEs of approximately
60–65 mV. Their oxidation potentials are significantly shifted
towards the cathodic range compared to those for the dichloro-
clathrochelate precursor due to the electromeric effects of these
substituents, which stabilize the oxidized clathrochelate cationic
species.
The cathodic ranges of the CVs for the mono- and dichloro-
clathrochelate cobalt(II)-containing precursors and their mono-
ribbed-functionalized macrobicyclic derivatives contain quasi-
reversibile waves with the current ratio of the direct and reverse
waves being approximately 1, which were assigned to the encap-
sulated cobalt-centered Co2+/+ reduction processes. For the
mono- and dichloroclathrochelate precursors, the ΔE values are
approximately 60–65 mV, and their reduced anionic forms are
stable in the CV time scale due to the stabilization of these elec-
trochemically generated cobalt(I)-containing species by the elec-
tron-withdrawing ribbed substituent(s) in the macrobicyclic
framework. The ΔE values for the electrochemical reduction of
the macrobicycles CoBd2((n-C4H9NH)2Gm)(BF)2, CoBd2((n-
C12H25S)2Gm)(BF)2, CoBd2(S2-Nx)(BF)2 and CoBd2(N2-Nx)
(BF)2 are higher than that for their dihalogen-containing precur-
sor. This may be explained by a destabilizing electronic effect of
the electron-donating substituents in their chelate fragment, as
well as by the formation of negatively charged electron-rich 20-
electron systems. In addition, the HOMOs of the monoribbed-
functionalized cobalt(II) clathrochelates that are involved in the
reductions are antibonding. As a result, the transfer of an electron
to these orbitals leads to a decrease in the bonding energy
between the encapsulated cobalt ion and the donor nitrogen
atoms.1d The cathodic shift of their reduction potentials as
Fig. 8 CV for the clathrochelate precursor CoBd2(Cl2Gm)(BF)2.
CoBd2(HGmCl)(BF)2 and CoBd2(Cl2Gm)(BF)2 may be ex-
plained by a destabilization of the 3+ oxidation state of an encap-
sulated cobalt ion due to the electron-withdrawing effect of
the ribbed chlorine atom(s) in their macrobicyclic ligands.
The macrobicycle CoBd2(((C2H5)2N)GmCl)(BF)2 contains the
chlorine atom as a strong electron-withdrawing substituent
and the diethylamine group as a strong electron-donating one
in the same π-conjugated chelate fragment, and this oxidation
state is stable in the CV time scale. The sulfide and amine
monoribbed-functionalized complexes CoBd2((n-C4H9NH)2Gm)-
(BF)2, CoBd2((n-C12H25S)2Gm)(BF)2, CoBd2(S2-Nx)(BF)2 and
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compared to those of the dichlorine-containing precursor may be
also explained by the differences in the electromeric effects of
the functionalizing ribbed substituents.
the potential E°(2H+/H2) for this producing system and that for
an electrocatalyst19). With an overpotential in the range
0–100 mV, the yield of molecular hydrogen decreases slightly,
whereas increasing it further causes a dramatic decrease in this
yield. It should be noted that the natural hydrogenases also
efficiently operate at the overpotentials less than 100 mV.20
Thus, the cobalt(II) clathrochelates obtained can be considered as
promising functional biomimetic models.
The efficiency of the electrocatalytic production of hydrogen
from H+ ions can be enhanced by immobilization of the catalyst
on the surface of the working electrode: the rate of this electro-
chemical process considerably increases due to the increase in
the concentration of catalyst on the clathrochelate-modified elec-
trode surface. The working gold electrode was modified by the
complexes CoBd2(HGm(SCH2CH2SCH2CH2SH))(BF)2 and
CoBd2(HGm(SCH2CH2SH))(BF)2 with terminal mercapto
groups by retaining them in their dichloromethane solutions for
a long time. The surface concentrations of the immobilized com-
plexes were deduced from the CVs as the integrated charge
under the corresponding CV peaks; they are equal to 5.3 × 10−12
and 5.5 × 10−12 mol cm−2, respectively. Considering the clathro-
chelate molecules as spheres with a diameter of approximately
6 Å (estimated from the single-crystal X-ray diffraction exper-
iments), the largest surface concentrations21 of the cage com-
plexes were calculated as 4.8 × 10−12 mol cm−2. Therefore,
these experimental values suggest a highly dense packing of the
clathrochelate molecules on the gold surface.
The electrochemical oxidation of the complexes CoBd2-
(HGm(SCH2CH2SH))(BF)2 and CoBd2(HGm(SCH2CH2SCH2-
CH2SH))(BF)2 with terminal mercapto groups on a GC working
electrode in their acetonitrile solutions is significantly different
from those for other monoribbed-functionalized cobalt(II) cla-
throchelates. In the anodic range, their CVs contain two oxi-
dation waves (Fig. 9, Table 2). The first one (at 630 mV for
CoBd2(HGm(SCH2CH2SH))(BF)2 and at 600 mV for
CoBd2(HGm(SCH2CH2SCH2CH2SH))(BF)2) is a one-electron
and reversible process (ΔE = 60 mV) with the current ratio of the
direct and reverse waves equal to 1. These oxidations are metal-
localized and assigned to the redox-couple Co2+/3+. The resulting
cationic cobalt(III)-containing complexes are stable in the CV
time scale due to the electrometric effects of the ribbed sulfide
substituents. The second oxidation wave at 920 and 970 mV,
respectively, is irreversible and corresponds to the oxidation of
the terminal mercapto groups with the formation of unstable S-
centered radical cations. These radicals very quickly detach the
H+ ions to form the highly reactive species that then undergo the
subsequent chemical reactions.
In the cathodic range, the solution CVs of these complexes
contain quasi-reversible waves with a current ratio of the direct
and reverse waves equal to 1, which were assigned to the Co2+/+
reduction couple. Thus, the cobalt(I)-containing clathrochelate
anions formed are stable in the CV time scale.
The symmetric shape of the CV curves obtained with a gold
electrode, as well as the electrochemical characteristics of the
clathrochelate species immobilized on its surface, are close to
the ideal theoretical ones for the reversible processes of the
immobilized redox-active species {namely, a small difference
between the cathodic and reverse anodic peaks at low scan rates
(E = 10 and 17 mV for the complexes CoBd2(HGm(SCH2-
We studied the electrocatalytic properties of the cobalt clathro-
chelates obtained and their analogs in the production of hydro-
gen from H+ ions using perchloric acid as the source of these
ions and a GC electrode. The addition of HClO4 to the aceto-
nitrile solutions of all these complexes resulted in the formation
of the same catalytic cathodic reduction Co2+/+ waves. An
increase in concentration of HClO4 causes a slight negative shift
of these waves, together with an increase in their intensities
reaching a plateau; the controlled-potential electrolysis with gas
chromatography analysis of the gaseous reaction products
confirmed the production of molecular hydrogen in high Faraday
yields. This suggests that the observed enhancements of current
are caused by the electrocatalytic proton reduction. As it can be
seen from Fig. 10, the Faraday yield of the reaction 2H+/H2
decreases with a decrease in the reduction potential of the cla-
throchelate electrocatalyst and with a cathodic shift of the
working potential of the electrocatalytic process due to an
increase in the overpotential value (i.e., the difference between
Fig. 10 Plot of the Faraday yields of the clathrochelate-catalyzed
hydrogen production from HClO4 acetonitrile solutions versus E for
the macrobicyclic electrocatalysts ( ) Co(Cl2Gm)3(Bn-C4H9)2, ( )
Co(Cl2Gm)3(BC6H6)2, ( ) CoBd2(Cl2Gm)(BF)2, ( ) CoBd2(HGmCl)-
(BF)2, ( ) CoBd2(S2-Nx)(BF)2, ( ) CoBd2(HGm(SCH2CH2SH))(BF)2,
( ) CoBd2((n-C12H25S)2Gm)(BF)2, ( ) CoBd2(HGm(SCH2CH2-
SCH2CH2SH))(BF)2, ( ) CoBd2(N2-Nx)(BF)2, ( ) CoBd2(((C2H5)2N)-
GmCl)(BF)2, ( ) CoBd2((n-C4H9NH)2Gm)(BF)2.
Fig. 9 CVs for the thiol-terminated monoribbed-functionalized
clathrochelates CoBd2(HGmSCH2CH2SCH2CH2SH)(BF)2 (a) and
CoBd2(HGmSCH2CH2SH)(BF)2 (b).
6086 | Dalton Trans., 2012, 41, 6078–6093
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Fig. 11 CVs for the gold-immobilized complexes CoBd2(HGm(SCH2CH2SH))(BF)2 (a) and CoBd2(HGm(SCH2CH2SCH2CH2SH))(BF)2 (b) in 0.1
M ((n-C4H9)4N)BF4 acetonitrile solutions in the presence of HClO4: 10 ( ), 15 ( ), and 25 mM ( ) at scan rate 20 mV s−1, vs. Ag/AgCl/KClaq.
Inserts: the cathodic range of the CVs for these immobilized complexes at scan rate 50 mV s−1
.
CH2SH))(BF)2 and CoBd2(HGm(SCH2CH2SCH2-CH2SH))-
(BF)2, respectively) and the cathodic and reverse anodic peak
currents being equal, as well as a linear correlation of the peak
current versus the scan rate}. In this case, the rate-limiting stage
is an electron transfer from the electrode surface to the immobi-
lized encapsulated metallocenter rather than a charge transfer
between the redox centers in their clathrochelate-containing
surface layers. So, these electrocatalysts should be highly active
in the catalytic production of molecular hydrogen from H+ ions.
The CVs for the immobilized cobalt clathrochelates in a catho-
dic range (Fig. 11) contain the one-electron waves assigned
to the redox-couple Co2+/+. The potentials of these reduction
processes are very close to those for the parent macrobicyclic
complexes with terminal mercapto groups in acetonitrile
solutions.
The electrocatalytic activity of the immobilized monoribbed-
functionalized cobalt(II) clathrochelates for the production of
molecular hydrogen from H+ ions was studied for HClO4 aceto-
nitrile solution. The stepwise addition of this solution caused an
increase in the catalytic wave current that was observed at the
first reduction potential. Such increase is characteristic of the
effective electrocatalytic process. To study the stability of the cla-
throchelate-modified electrodes in time, we performed the elec-
trolysis for 5 h. As it can be seen from Fig. 12, the yields of H2
with clathrochelate-modified electrodes are constant in this time
interval. After the electrolysis, these electrodes were removed
from acetonitrile solutions, repeatedly washed with acetonitrile
and studied by CV. According to the CV data, the surface con-
centration of the clathrochelate catalysts persists. This indicates a
high electro- and chemical stability of the clathrochelate-
modified electrodes and an absence of the desorption of the
immobilized cobalt cage complexes (i.e., the transport of these
catalysts from a gold electrode surface to the acetonitrile
solution).
Fig. 12 Plot of the yield of H2 versus time of the electrolysis with the
clathrochelate-modified electrodes {CoBd2(HGm(SCH2CH2SH))(BF)2
(■) and CoBd2(HGm(SCH2CH2SCH2CH2SH))(BF)2 ( )};
E
=
−500 mV, 0.01 M HClO4 acetonitrile solution, 0.1 M ((n-C4H9)4N)BF4,
vs. Ag/AgCl/KCl.
electrocatalytic activity for the production of molecular hydrogen
from H+ ions and chemical stability for a long time.
Experimental section
General considerations
The reagents used, CoCl2·6H2O, BF3·O(C2H5)2, triethylamine,
α-benzyldioxime, n-butylamine, 1-dodecanethiol, 1,2-ethane-
dithiol, bis(2-mercaptoethyl)sulfide and ethylenediamine, as well
as organic solvents and silica gel (0.035–0.070 mm, for column
chromatography) were obtained commercially (Acros). The
dichloroglyoxime was prepared by the chlorination of glyoxime
as described in Ref. 22. Monochloroglyoxime was obtained as
described elsewhere.23 Cadmium amide Cd(N(Si(CH3)3)2)2 was
prepared as described earlier.12
Conclusions
Thus, all the cobalt(II) clathrochelates obtained (both in a sol-
ution and immobilized on a gold electrode) demonstrate a high
Analytical data (C, H, N contents) were obtained by gas
chromatography with a Carlo Erba model 1106 microanalyzer as
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well as by gravimetry (C and H contents only). Cobalt content
was determined by X-ray fluorescence analysis. Boron content
was determined gravimetrically. Fluorine content was determined
spectrophotometrically. Sulfur content was determined by Shoe-
niger mecurimetric titration.
The MALDI-TOF mass spectra were recorded in both the
positive and negative spectral regions using a MALDI-TOF-MS
Bruker Autoflex mass spectrometer in reflecto-mol mode. The
ionization was induced by UV-laser with wavelength 336 nm.
The sample was applied to a nickel plate, 2,5-dihydroxybenzoic
acid was used as a matrix. The accuracy of measurements was
0.1%.
thoroughly deaerated before and during the CV experiments
using argon flow.
The thiol-terminated cobalt(II) clathrochelates CoBd2(HGm
(SCH2CH2SH))(BF)2 and CoBd2(HGm(SCH2CH2SCH2CH2-
SH))(BF)2 were immobilized on a gold electrode. This electrode
was initially thoroughly polished with 0.3 μm alumina slurry for
5 min, rinsed with acetone and then electrochemically cleaned
by scanning in the potential range −1500 to 1500 mV at scan
rate 100 mV s−1 (50 cycles in acetonitrile). The cleaned gold
electrode was rinsed with dichloromethane and then immersed in
a 1 mM dichloromethane solution of the thiol-terminated
complex under study for 3 h. The clathrochelate-modified gold
electrode was washed with dichloromethane and dried under
argon.
The IR spectra of the solid samples (KBr tablets) in the range
400–4000 cm−1 were recorded with a Perkin Elmer FT-IR Spec-
trum BX II spectrometer.
Gas chromatography analysis of the gases evolved during the
electrolysis was performed with a Varian 450 GC equipped with
a pulsed discharge helium ionization detector D-4-I-VA38-R.
Hydrogen production was quantitatively detected using a 30 m-
in-length stainless steel column with an inside diameter of
250 μm at 120 °C for the detector and at 80 °C for the oven. The
The UV-vis spectra of the solutions in dichloromethane
were recorded in the range 220–900 nm with a Lambda 9
Perkin Elmer spectrophotometer. The individual Gaussian com-
ponents of these spectra were calculated using the SPECTRA
program.
The 1H, 13C{1H} and 19F NMR spectra were recorded
from CD2Cl2 solutions using Bruker Avance 400 and 600
spectrometers.
carrier gas was helium, flowing at a rate of 40 mL min−1
.
The injections (250 μL) were performed via a sampling loop.
The retention time of gaseous H2 was 2.48 min.
The magnetic susceptibility of the fine-crystalline samples was
measured in the temperature range 5–400 K using an automatic
Quantum Design MPMS-5 SQUID magnetometer at an external
Synthesis
field strength of 0.1 and 0.5 T with a gradient of 10 T m−1
.
[CoII(HBd)2Py2]. CoCl2·6H2O (6.5 g, 27.3 mmol) and pyri-
dine (10.5 mL, 130 mmol) were dissolved in ethanol (75 mL)
under argon, and the reaction mixture was stirred for 4 min.
Then α-benzyldioxime (12.48 g, 52 mmol) and ethanol (35 mL)
were added to the light-blue solution/suspension formed. The
dark-brown reaction mixture was stirred for 11 h, left overnight
and filtered under argon. The solid was washed with ethanol
(60 mL, in two portions) and dried in vacuo. The product was
stored under an inert atmosphere. Yield: 16.9 g (94%).
HgCo(NCS)4 was used as the calibrating standard. The accuracy
of temperature and magnetic susceptibility measurements was
0.1 K and 1·10−7 cm3 g−1, respectively. For recalculation
from mass to molar magnetic susceptibilities, the corrections for
diamagnetism (Pascal constants and the temperature-independent
paramagnetism of d-metal ions24) were applied. The dependence
of magnetization on the external field was measured to check for
the presence of ferromagnetic admixtures. The Origin 6.0
program was used in the iterational treatment of the magneto-
chemical data.
X-band EPR spectra were acquired on a Bruker Elexsys E580
X/Q-band EPR spectrometer equipped with ER 4118X-MD5W
resonator and Oxford Instruments cryogenic system. The glassy
samples for the EPR experiments were obtained from 5 mM (or
less, if a compound under study was less soluble) toluene sol-
utions of the clathrochelate complexes. The EPR spectra were
registered using the following parameters: microwave frequency
9.4 GHz, microwave power in the range 20–0.002 mW, sweep
width 1800 G, modulation frequency 100 kHz, modulation
amplitude 3 G, conversion time and time constant in the range
20.48–81.92 ms, resolution 2048 points.
CV experiments were carried out in acetonitrile solutions with
0.10 M ((n-C4H9)4N)BF4 as a supporting electrolyte using a
Parstat model 2273 potentiostat (Prinston Applied Research,
USA) in a conventional and one-compartment three-electrode
cell (10 mL of solution). A glassy carbon (GC) disk electrode
with an active surface area of 0.125 cm2 was used as a working
electrode in solution. The electrode was thoroughly polished and
rinsed before measurements. A platinum counter electrode and
standard Ag/AgCl/KCl reference electrode (RE) were used. All
potentials were referred to this RE. The measurements were per-
formed at scan rates of 20 and 50 mV s−1. All solutions were
[CoIIBd2(CH3CN)2(BF2)2]. Complex [CoII(HBd)2Py2] (24.9 g,
35.8 mmol) and hexamethyldisiloxane (1.5 mL) were dissolved/
suspended in diethyl ether–acetonitrile 1 : 1 mixture (220 mL)
under argon. The reaction mixture was stirred for 5 min,
and BF3·O(C2H5)2 (22.7 mL, 180 mmol) was added dropwise
for 5 min to the stirring solution/suspension. Then the
reaction mixture was stirred for 5 min and the light-brown pre-
cipitate formed was filtered under argon. The product was
washed with diethyl ether–acetonitrile mixture (200 mL, in
two portions), diethyl ether–acetonitrile–hexamethyldisiloxane
210 : 42 : 1 mixture (126.5 mL, in two portions) and dried in
vacuo. The product was stored under an inert atmosphere. Yield:
20.9 g (82%).
CoBd2(Cl2Gm)(BF)2. Triethylamine (12.2 mL, 88 mmol) was
added dropwise to the stirring solution of BF3·O(C2H5)2
(14.8 mL, 117 mmol) in nitromethane (150 mL) under argon,
and then dichloroglyoxime (5.06 g, 32 mmol), complex
[CoIIBd2(CH3CN)2(BF2)2] (20.92 g, 29 mmol), hexamethyldisi-
loxane (1.9 mL, 8.8 mmol) and nitromethane (10 mL) were
added to the reaction mixture. The red-brown solution/suspen-
sion was vigorously stirred at 125 °C for 40 min with partial dis-
tillation of a solvent (90 mL); the reaction course was controlled
6088 | Dalton Trans., 2012, 41, 6078–6093
This journal is © The Royal Society of Chemistry 2012

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by TLC (eluent: dichloromethane–hexane 2 : 1 mixture). Then
the reaction mixture was cooled to r.t., and dichloromethane
(50 mL) was added. The solution obtained was washed with
water (600 mL, in three portions), diluted with dichloromethane
(70 mL) and dried with CaCl2. The dichloromethane solution
was filtered off and rotary evaporated to dryness. The oily
residue was extracted with benzene (200 mL), the extract was
filtered and then flash chromatographed through a silica gel
(30 mm layer). The filtrate was evaporated to dryness, the solid
residue was washed with hexane (40 mL) and dried in vacuo.
Yield: 9.41 g (43%). Calcd for C30H20N6B2F2Cl2CoO6 (%): C,
48.05; H, 2.67; N, 11.20; Cl, 9.47. Found (%): C, 48.20; H,
2.85; N, 11.11; Cl, 9.38. MS: m/z (I, %): 750(100) [M]+˙, 773
(20) [M + Na+]+, 789(15) [M + K+]+. 1H NMR (CD2Cl2):
δ(ppm) 6.55 (br. s, 8H, meta-Ph), 9.02 (br. s, 4H, para-Ph),
10.02 (br. s, 8H, ortho-Ph). 13C{1H} NMR (CD2Cl2): 80.0 (s,
(s, CH2CH2CH3), 117.1 (s, para-Ph), 146.2 (s, meta-Ph), 177.8
(s, ortho-Ph). IR (cm−1, KBr): 901, 931, 1097, 1121 ν(N–O);
1212m ν(B–O) + ν(B–F); 1560 ν(NCvN); 1587 ν(PhCvN).
UV-vis (CH2Cl2): λmax/nm (ε × 10−3, mol−1 l cm−1): 231 (31),
255 (15), 267 (8.3), 285 (18), 308 (11), 341 (5.3), 357 (3.0), 391
(4.4), 445 (3.7), 514 (2.9).
CoBd2((n-C12H25S)2Gm)(BF)2. Complex CoBd2(Cl2Gm)(BF)2
(0.2 g, 0.27 mmol) was dissolved/suspended in dichloromethane
(2.5 mL), and 1-dodecanethiol (0.16 mL, 0.68 mmol) and tri-
ethylamine (0.1 mL, 0.68 mmol) were added. The reaction
mixture was stirred for 1 h; the reaction course was controlled by
TLC (eluent: dichloromethane–hexane 2 : 1 mixture). Then 1-
dodecanethiol (0.1 mL, 0.42 mmol) was added. The reaction
mixture was stirred for 45 min, and hexane (8 mL) was added.
The solution/suspension formed was filtered off and the filtrate
was flash chromatographed through a silica gel (30-mm layer).
The hexane elute was thrown out, and the target complex was
eluted with a dichloromethane–hexane 2 : 1 mixture. The
orange-brown elute was evaporated to dryness, the solid residue
was washed with ethanol (12 mL, in four portions) and dried in
vacuo. Yield: 0.19 g (65%). Calcd for C54H70N6B2CoF2O6S2
(%): C, 59.94; H, 6.48; N, 7.77; Co, 5.46; B, 2.04. Found (%):
C, 60.04; H, 6.65 (gravimetrically found: C, 59.92; H, 6.58); N,
7.60; Co, 5.38; B, 1.93. MS: m/z: 1081 [M]+˙. 1H NMR
(CD2Cl2): δ(ppm) −0.77 (br. s, 6H, CH3), 1.15 (br. s, 40H,
CH2), 5.03 (br. s, 4H, CH2S), 6.51 (br. s, 8H, meta-Ph), 8.86 (br.
s, 4H, para-Ph), 9.57 (br. s, 8H, ortho-Ph). 13C{1H} NMR
(CD2Cl2): 12.3 (s, CH3), 15.8, 24.6, 30.3, 30.6, 31.2, 31.4, 31.5,
31.6, 33.8, 36.3 (all s, CH2), 84.1 (s, ortho-Ph), 122.9 (s, para-
Ph), 133.9 (s, meta-Ph). IR (cm−1, KBr): 917, 945, 1072, 1122
ν(N–O); 1201m ν(B–O) + ν(B–F); 1556 ν(SCvN), 1579
ortho-Ph), 124.9 (s, para-Ph), 130.6 (s, meta-Ph). IR (cm−1
,
KBr): 935m, 1076, 1113, 1140 ν(N–O); 1207m ν(B–O) +
ν(B–F); 1565 ν(ClCvN), 1581 ν(PhCvN). UV-vis (CH2Cl2):
λmax/nm (ε × 10−3, mol−1 l cm−1): 248 (31), 289 (16), 366 (7.7),
380 (4.3), 443 (5.1), 485 (8.5), 524 (2.1).
CoBd2(HGmCl)(BF)2. This complex was synthesized like the
previous one, except that monochloroglyoxime (4.48 g,
37 mmol) was used instead of dichloroglyoxime. Yield: 15.2 g
(64%). Calcd for C30H21N6B2F2ClCoO6 (%): C, 50.31; H, 2.94;
N, 11.74; Cl, 4.96. Found (%): C, 50.12; H, 3.07; N, 11.55; Cl,
1
5.05. MS: m/z: 715 [M]+˙. H NMR (CD2Cl2): δ(ppm) 6.37 (br.
s, 4H, meta-Ph), 6.61 (br. s, 4H, meta-Ph), 8.90 (br. s, 2H, para-
Ph), 9.38 (br. s, 2H, para-Ph), 9.80 (br. s, 4H, ortho-Ph), 10.49
(br. s, 4H, ortho-Ph). 13C{1H} NMR (CD2Cl2): δ(ppm) 70.9,
83.0 (two s, ortho-Ph), 122.5, 125.0 (two s, para-Ph), 130.5,
132.1 (two s, meta-Ph). IR (cm−1, KBr): 933m, 1074, 1130
ν(N–O); 1207m ν(B–O) + ν(B–F); 1556m ν(ClCvN +
HCvN), 1585 ν(PhCvN). UV-vis (CH2Cl2): λmax/nm (ε ×
10−3, mol−1 l cm−1): 243 (14), 258 (5.5), 281 (4.2), 302 (4.5),
354 (3.9), 380 (1.7), 445 (1.6), 486 (3.7), 529 (0.7).
ν(PhCvN). UV-vis (CH2Cl2): λmax/nm (ε × 10−3, mol−1
l
cm−1): 253 (30), 284 (3.9), 295 (15), 340 (7.1), 389 (10), 465
(3.5), 500 (8.0).
CoBd2(HGm(SCH2CH2SCH2CH2SH))(BF)2. A solution of
complex CoBd2(HGmCl)(BF)2 (0.3 g, 0.42 mmol) and triethyl-
amine (0.061 mL, 0.44 mmol) in dichloromethane (15 mL) was
added dropwise for 2.5 h to the stirring solution of bis(2-mercap-
toethyl)sulfide (0.27 mL, 2.1 mmol) in dichloromethane
(10 mL) under argon; the reaction course was controlled by TLC
(eluent: dichloromethane–hexane 2 : 1 mixture). The reaction
mixture was stirred for 40 min and then washed with water
(40 mL), 10% Na2CO3 aqueous solution (90 mL, in three por-
tions) and again with water (150 mL, in three portions). The
dichloromethane solution obtained was dried with CaCl2, filtered
off, evaporated to a small volume and precipitated with hexane.
The precipitate was washed with hexane and diethyl ether, and
then dissolved in a small volume of dichloromethane. The
dichloromethane solution was flash chromatographed through a
silica gel (30 mm layer), evaporated to a small volume and preci-
pitated with hexane. The solid product was washed with hexane
CoBd2((n-C4H9NH)2Gm)(BF)2. Complex CoBd2(Cl2Gm)(BF)2
(0.2 g, 0.27 mmol) was dissolved/suspended in dichloromethane
(4 mL), and n-butylamine (0.13 mL, 1.35 mmol) was added
dropwise to the stirring solution in air. The reaction mixture was
stirred for 1.5 h; the reaction course was controlled by TLC
(eluent: dichloromethane–hexane 2 : 1 mixture). Then the sol-
ution obtained was precipitated with hexane (20 mL) and filtered
off. The precipitate was washed with hexane (15 mL, in three
portions), ethanol (15 mL, in three portions) and diethyl ether
(10 mL, in two portions) and dried in air. The solid was dis-
solved in a small amount of dichloromethane and precipitated
with hexane. The precipitate was filtered and dried in vacuo.
Yield: 0.16 g (73%). Calcd for C38H40N8B2CoF2O6 (%): C,
55.41; H, 4.86; N, 13.61; Co, 7.17; B, 2.67. Found (%): C,
55.26; H, 4.68 (gravimetrically found: C, 55.44; H, 4.80); N,
13.45; Co, 7.03; B, 2.58. MS: m/z: 823 [M]+˙. 1H NMR
(CD2Cl2): δ(ppm) −14.73 (br. s, 2H, NH), −1.68 (br. s, 4H,
CH2CH3), −1.39 (br. s, 6H, CH3), −0.90 (br. s, 4H,
CH2CH2CH3), 6.77 (br. s, 8H, meta-Ph), 8.22 (br. s, 8H, ortho-
Ph), 8.53 (br. s, 4H, para-Ph), 23.34 (br. s, 4H, CH2N). 13C{1H}
NMR (CD2Cl2): 17.0 (s, CH3), 18.9 (s, CH2CH2CH3), 98.9
and dried in vacuo. Yield: 0.145
g (41%). Calcd for
C34H30N6B2F2CoO6S3 (%): C, 48.98; H, 3.60; N, 10.08. Found
1
(%): C, 48.84; H, 3.64; N, 9.90. MS: m/z: 833 [M]+˙. H NMR
(CD2Cl2): δ(ppm) 2.63 (br. s, 2H, CH2S), 2.75 (br. s, 2H,
CH2S), 3.26 (br. s, 2H, CH2S), 3.48 (br. s, 2H, CH2S–Clt), 6.53
(br. s, 4H, meta-Ph), 6.56 (br. s, 4H, meta-Ph), 9.06 (br. s, 2H,
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 6078–6093 | 6089

View Online
para-Ph), 9.16 (br. s, 2H, para-Ph), 10.08 (br. s, 8H, ortho-Ph).
13C{1H} NMR (CD2Cl2): 33.3, 33.4, 37.9 (all s, CH2S), 40.5 (s,
CH2S–Clt), 79.0, 81.7 (two s, ortho-Ph), 122.6, 123.2 (two s,
para-Ph), 133.1, 133.5 (two s, meta-Ph). IR (cm−1, KBr): 928,
948, 1124 ν(N–O); 1203m ν(B–O) + ν(B–F); 1541 ν(HCvN),
1558 ν(SCvN), 1576 ν(PhCvN). UV-vis (CH2Cl2): λmax/nm
(ε × 10−3, mol−1 l cm−1): 241 (14), 246 (11), 259 (7.1),
278 (15), 329 (6.7), 383 (7.0), 440 (2.7), 488 (2.7), 491 (5.2).
meta-Ph). 19F NMR (CD2Cl2) δ(ppm) −100.5, −103.9 (two m,
nonequivalent O3BF capping groups). IR (cm−1, KBr): 932m,
1125 ν(N–O); 1203m ν(B–O) + ν(B–F); 1543m ν(ClCvN) +
v(NCvN), 1597 ν(PhCvN). UV-vis (CH2Cl2): λmax/nm (ε ×
10−3, mol−1 l cm−1): 249 (33), 278 (15), 302 (9.0), 337 (7.3),
370 (5.8), 390 (4.1), 427 (4.0), 479 (3.3), 502 (4.9).
CoBd2(N2-Nx)(BF)2. Complex CoBd2(Cl2Gm)(BF)2 (0.1 g,
0.13 mmol) was dissolved/suspended in dichloromethane
(3 mL), and ethylenediamine (0.026 mL, 0.39 mmol) was added
dropwise to the stirring solution. The reaction mixture was
stirred for 50 min; the reaction course was controlled by TLC
(eluent: dichloromethane). Then hexane (6 mL) was added to the
reaction mixture. The precipitate formed was filtered off, washed
with water (10 mL, in two portions), ethanol (16 mL, in four
portions), hexane (3 mL) and dried in air. The solid was dis-
solved in dichloromethane–acetonitrile 5 : 1 mixture (35 mL),
and the solution was flash chromatographed through a silica gel
(30 mm layer). The filtrate was evaporated to dryness and dried
in vacuo. Yield: 0.06 g (63%). Calcd for C32H26N8B2F2CoO6:
C, 52.10; H, 3.53; N, 15.20; Co, 8.00. Found (%): C, 52.03; H,
CoBd2(HGm(SCH2CH2SH))(BF)2. A solution of complex
CoBd2(HGmCl)(BF)2 (0.3 g, 0.42 mmol) and triethylamine
(0.075 mL, 0.53 mmol) in dichloromethane (20 mL) was added
dropwise for 3 h to the stirring solution of 1,2-ethanedithiol
(0.18 mL, 2.1 mmol) in dichloromethane (15 mL) under argon;
the reaction course was controlled by TLC (eluent: dichloro-
methane–hexane 2 : 1 mixture). The reaction mixture was stirred
for 1.5 h, and hexane (15 mL) was added. The solution was
rotary evaporated to 1/3 volume. The precipitate formed was
filtered off, washed with hexane (15 mL), ethanol (30 mL, in six
positions) and warm diethyl ether (25 mL, in five portions).
The solid residue was dissolved in dichloromethane–hexane 3 : 1
mixture, and the solution was flash chromatographed through a
silica gel (eluent: dichloromethane–hexane 3 : 1 mixture). The
filtrate was evaporated to dryness, washed with hexane and dried
in vacuo. Yield: 0.15 g (46%). Calcd for C32H26N6B2F2CoO6S2
(%): C, 49.68; H, 3.36; N, 10.87. Found (%): C, 49.54; H, 3.50;
N, 10.77. MS: m/z: 773 [M]+˙. 1H NMR (CD2Cl2): δ(ppm) 3.26
(br. s, 2H, CH2S), 3.87 (br. s, 2H, CH2S–Clt), 6.51 (br. s, 4H,
meta-Ph), 6.55 (br. s, 4H, meta-Ph), 9.06 (br. s, 2H, para-Ph),
9.15 (br. s, 2H, para-Ph), 10.12 (br. s, 8H, ortho-Ph). 13C{1H}
NMR (CD2Cl2): 39.5 (s, CH2SH), 40.9 (s, CH2S–Clt), 78.9,
81.6 (two s, ortho-Ph), 122.6, 123.1 (two s, para-Ph), 133.1,
133.5 (two s, meta-Ph). IR (cm−1, KBr): 942m, 1123 ν(N–O);
1201m ν(B–O) + ν(B–F); 1540m ν(HCvN) + v(SCvN), 1579
ν(PhCvN). UV-vis (CH2Cl2): λmax/nm (ε × 10−3, mol−1
l cm−1): 245 (25), 259 (12), 281 (10), 303 (9.8), 344 (5.3), 382
(6.7), 421 (3.2), 487 (2.0), 491 (5.5).
1
3.46; N, 15.06; Co, 7.90. MS: m/z: 737 [M]+˙. H NMR (dmso-
d6): δ(ppm) 4.17 (br. s, 4H, CH2N), 11.02 (br. s, 8H, meta-Ph),
14.32 (br. s, 8H, ortho-Ph), 15.16 (br. s, 4H, para-Ph). 13C{1H}
NMR (dmso-d6): 9.1 (s, CH2N), 97.4 (s, ortho-Ph), 112.6 (s,
para-Ph), 148.3 (s, meta-Ph). IR (cm−1, KBr): 912, 954, 981,
1017, 1056, 1117 ν(N–O); 1187m ν(B–O) + ν(B–F); 1545
ν(NCvN), 1578 ν(PhCvN), 1644 δ(N–H). UV-vis (CH2Cl2):
λmax/nm (ε × 10−3, mol−1 l cm−1): 260 (25), 297 (18), 342 (3.0),
364 (4.9), 393 (1.2), 428 (3.5), 509 (3.1).
CoBd2(S2-Nx)(BF)2. Complex CoBd2(Cl2Gm)(BF)2 (0.2 g,
0.27 mmol) was dissolved in dichloromethane (70 mL), and 1,2-
ethanedithiol (0.07 mL, 0.81 mmol) and triethylamine
(0.095 mL, 0.68 mmol) were added dropwise to the stirring sol-
ution. The reaction mixture was stirred for 1.5 h; the reaction
course was controlled by TLC (eluent: dichloromethane–hexane
2 : 1 mixture). Then the solution was evaporated to a small
volume and precipitated with hexane. The precipitate was filtered
off, washed with ethanol (20 mL, in four portions), diethyl ether
(20 mL, in four portions), hexane (5 mL) and dried in air. The
solid was extracted with dichloromethane (75 mL), and the
extract was separated by column chromatography on silica gel (1
× 10 cm column, eluent: dichloromethane). The brown elute was
evaporated to dryness, washed with hexane and dried in vacuo.
Yield: 0.11 g (54%). Calcd for C32H24N6B2F2CoO6S2 (%): C,
49.81; H, 3.11; N, 10.90; Co, 7.65; S, 8.30. Found (%): C,
49.69; H, 3.05; N, 10.82; Co, 7.60; S, 8.18. MS: m/z: 771 [M]+˙.
1H NMR (dmso-d6): δ(ppm) 3.35 (br. s, 4H, CH2S), 6.53 (br. s,
8H, meta-Ph), 9.1 (br. s, 4H, para-Ph), 9.97 (br. s, 8H, ortho-
Ph). 13C{1H} NMR (dmso-d6): 22.3 (s, CH2S), 75.7 (s, ortho-
Ph), 121.9 (s, para-Ph), 130.9 (s, meta-Ph). IR (cm−1, KBr):
922, 934, 1074, 1122 ν(N–O); 1202m ν(B–O) + ν(B–F); 1552
ν(NCvN), 1580 ν(PhCvN). UV-vis (CH2Cl2): λmax/nm (ε ×
10−3, mol−1 l cm−1): 255 (23), 285 (12), 304 (11), 342 (6.8),
387 (9.2), 458 (3.3), 497 (7.5).
CoBd2(((C2H5)2N)GmCl)(BF)2. Complex CoBd2(Cl2Gm)(BF)2
(0.2 g, 0.27 mmol) was dissolved/suspended in dichloromethane
(3 mL), and diethylamine (0.14 mL, 1.35 mmol) was added
dropwise to the stirring solution in air. The reaction mixture was
stirred for 2 h; the reaction course was controlled by TLC
(eluent: dichloromethane–hexane 2 : 1 mixture). Then the sol-
ution was precipitated with hexane (15 mL) and filtered off. The
precipitate was washed with water and dried in air. The solid was
dissolved in a small volume of dichloromethane, and the dichlor-
omethane solution was flash chromatographed through a silica
gel (30 mm layer). The filtrate was evaporated to a small volume
and precipitated with hexane. The product was filtered off,
washed with hexane and dried in vacuo. Yield: 0.09 g (43%).
Calcd for C34H30N7B2F2CoClO6 (%): C, 51.91; H, 3.84; N,
12.46; Co, 7.50; B, 2.75; F, 4.83. Found (%): C, 52.03; H, 3.75;
1
N, 12.28; Co, 7.36; B, 2.85; F, 4.75. MS: m/z: 787 [M]+˙. H
NMR (CD2Cl2) δ(ppm) 0.35 (br. s, 6H, CH3), 6.09, 6.74 (both
br. s, 6H, meta-Ph), 7.70, 8.42 (both br. s, 6H, ortho-Ph), 7.79,
8.65 (both br. s, 4H, para-Ph), 13.37 (br. s, 4H, CH2). 13C{1H}
NMR (CD2Cl2): 40.7 (s, CH3), 77.3 (s, CH2), 87.7, 106.3 (two
s, ortho-Ph), 119.5, 125.6 (two s, para-Ph), 133.9, 138.1 (two s,
CoBd2((n-C4H9O)2Gm)(BF)2. Complex CoBd2(Cl2Gm)(BF)2
(0.2 g, 0.27 mmol) was dissolved/suspended in THF (5 mL),
and n-butanol (0.1 mL, 1.08 mmol) and a 0.32 M THF–hexane
6090 | Dalton Trans., 2012, 41, 6078–6093
This journal is © The Royal Society of Chemistry 2012

Table 3 Crystallographic data and refinement parameters for the crystals CoBd2(Cl2Gm)(BF)2·C7H16, CoBd2(HGmCl)(BF)2·2CHCl3, CoBd2((n-C4H9NH)2Gm)(BF)2·CH2Cl2, CoBd2(((C2H5)2N)
GmCl)(BF)2·C6H6, CoBd2((n-C4H9O)2Gm)(BF)2·2C6H6 and CoBd2(S2-Nx)(BF)2
CoBd2((n-C4H9NH)2Gm)
CoBd2(HGmCl)(BF)2·2CHCl3 (BF)2·CH2Cl2
CoBd2(((C2H5)2N)GmCl)
(BF)2·C6H6
CoBd2((n-C4H9O)2Gm)
(BF)2·2C6H6
CoBd2(Cl2Gm)(BF)2·C7H16
CoBd2(S2-Nx)(BF)2
Empirical
formula
Fw
Color, habit
Crystal size
(mm3)
a (Å)
b (Å)
c (Å)
α (°)
β (°)
C30H20B2Cl2CoF2N6O6·C7H16 C30H21B2ClCoF2N6O6·2CHCl3 C38H40B2CoF2N8O6·CH2Cl2 C34H30B2ClCoF2N7O6·C6H6 C38H38B2CoF2N6O8·2C6H6 C32H24B2CoF2N6O6S2
850.17
Brown, prism
0.19 × 0.13 × 0.12
954.26
Yellow-brown, prism
0.24 × 0.13 × 0.12
908.26
Dark brown, plate
0.55 × 0.40 × 0.15
864.76
Red-brown, prism
0.32 × 0.21 × 0.12
981.51
Red-brown, prism
0.18 × 0.11 × 0.06
771.24
Red-brown, plate
0.35 × 0.12 × 0.05
13.5294 (11)
17.7456 (15)
16.3800 (13)
15.485 (2)
13.6509 (18)
17.840 (3)
10.555 (4)
12.885 (4)
15.480 (5)
83.991 (7)
87.570 (7)
86.593 (7)
2088.6 (12)
2
21.434 (4)
17.448 (3)
21.475 (4)
12.3008 (12)
14.607 (2)
26.589 (4)
11.041(2)
12.489(3)
24.300(5)
94.896 (2)
92.809 (3)
γ (°)
V (Å3)
Z
3918.3 (6)
4
3766.6 (9)
4
8031 (2)
8
4777.4 (11)
4
3350.7(12)
4
Crystal
system
Space group P21/n
Monoclinic
Monoclinic
Triclinic
Orthorhombic
Orthorhombic
Orthorhombic
ˉ
P1
P21/n
Pbca
P212121
P212121
dcalc
1.441
1.683
1.444
1.430
1.365
1.529
(g cm−3
)
)
μ (mm−1
Min./max.
transmission
coeff.
0.64
—
1.02
0.856, 0.882
0.60
0.750, 0.915
0.56
—
0.43
—
0.70
0.791, 0.966
2θ max (°)
Independent 8.964 (0.092)
55
52
52
8145 (0)
52
60
57
7375 (0.109)
7857 (0.104)
13 909 (0.078)
8157 (0.051)
reflections
(Rint
)
Obs.refl./
restraints/
parameters
R,a % [F2 >
2σ(F2)]
4658/6 /506
0.049
4452/0/427
0.076
7246/0/549
0.050
4777/8/530
0.087
10 335/0/613
0.047
5141/3/421
0.059
Rw,b % (F2)
GOFc
0.078
1.00
0.170
1.00
0.109
1.01
0.194
1.00
0.084
1.03
0.148
1.04
Largest diff. 0.65 and −0.57
2.10 and −1.46
1.26 and −1.78
1.46 and −1.09
0.44 and −0.51
0.45 and −0.40
peak and
hole (e Å−3
)
F(000)
1748
1916
938
3560
2044
1572
2 2
2
a R = Σ||Fo| − |Fc||/Σ|Fo|. b Rw = [Σ(w(Fo2 − Fc ) )/Σ(w(Fo ))]1/2
.
c GOF = [Σw(Fo2 − Fc ) /(Nobs − Nparam)]1/2
2 2
.

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3 : 2 solution of Cd(N(Si(CH3)3)2)2 (1.7 mL, 0.54 mmol) was
added under argon. The reaction mixture was stirred for 2 h, and
4% aqueous acetic acid (80 mL) was added. The solution was
extracted with dichloromethane (50 mL), the extract was washed
with 10% Na2CO3 aqueous solution (60 mL), water (160 mL, in
two portions) and dried with Na2SO4. Then the dichloromethane
solution was filtered off and rotary evaporated to dryness. The
solid residue was washed with hexane and dried in vacuo. The
product was dissolved in dichloromethane and flash chromato-
graphed through a silica gel (30 mm layer). The filtrate was
evaporated to dryness, washed with hexane and dried in vacuo.
Yield: 0.13 g (59%). Calcd for C38H38N6B2F2CoO8 (%): C,
55.27; H, 4.61; N, 10.18; Co, 7.15. Found (%): C, 55.24; H,
4.72; N, 10.05; Co, 7.18. MS: m/z: 825 [M]+˙. 1H NMR
(CD2Cl2): δ(ppm) −0.23 (m, 14H, CH3CH2CH2), 6.27 (br. s,
8H, meta-Ph), 7.31 (br. s, 8H, ortho-Ph), 8.01 (br. s, 4H, para-
Ph), 11.04 (br. s, 4H, CH2O). 13C{1H} NMR (CD2Cl2): 14.4 (s,
CH3), 18.9 (s, CH3CH2), 42.6 (s, CH2CH2O), 71.4 (s, CH2O),
94.7 (s, ortho-Ph), 122.0 (s, para-Ph), 136.6 (s, meta-Ph). IR
(cm−1, KBr): 913, 946, 1066, 1119 ν(N–O); 1200–1216m ν(B–
O) + ν(B–F); 1545 ν(OCvN); 1580 ν(PhCvN). UV-vis
(CH2Cl2): λmax/nm (ε × 10−3, mol−1 l cm−1): 252 (24), 275
(18), 305 (9.7), 348 (6.1), 384 (5.3), 455 (4.6), 498 (4.0).
hydrogen atoms were calculated geometrically. The H(C) atoms
were included in the refinement by the riding model with
Uiso(H) = nUeq(C), where n = 1.5 for methyl groups and 1.2 for
the other atoms. All calculations were made using the
SHELXTL PLUS 5 program package.26
The crystallographic data and experimental details are listed in
Table 3.
Acknowledgements
The authors gratefully acknowledge support of RFBR (grants
10-03-00027, 10-03-00837, 10-03-00613, 11-03-00986, 12-03-
00955, 12-03-00961 and 12-03-90431), RAS (programs 6, 7
and 18) and Council of the President of the Russian Federation
(program of state support of the leading scientific schools, grant
NSh 7946.2010.3). We also thank Dr Matvey Fedin (Inter-
national Tomography Center SB RAS, Novosibirsk) for assist-
ance with the EPR spectra registration.
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