Clathrochelate monoribbed-functionalized iron(II)α-dioximates: Synthetic pathways and structural and electrochemical features

Article abstract of DOI:10.1039/b107021p

Monoribbed-functionalized (i.e. functionalization of only one of the three α-dioximate fragments) clathrochelate iron(II) tris-dioximates have been synthesized starting from the dichloride precursor FeBd₂(Cl₂Gm)(BF)₂ (where Bd^2- and Cl²Gm^2- are α-benzyldioxime and dichloroglyoxime dianions, respectively), obtained by condensation of the macrocyclic iron(II) bis-α-benzyldioximate [FeBd₂(BF₂)₂(MeCN)₂] with H₂Cl₂Gm. Thioalkyl, alkylamine, oxo- and azaoxocrown ether clathrochelates, as well as the bis-clathrochelate with a 1,5-diaminopentane bridging fragment, have been characterized using elemental analysis, PD mass, IR, UV-vis,⁵⁷Fe Moessbauer and¹H,¹³C and ¹¹B NMR spectroscopies, and X-ray crystallography [for the FeBd₂(Cl₂Gm)(BF)₂·2C₆H ₆, FeBd₂{(Et₂N)ClGm}(BF)₂·C ₆H₆ and FeBd₂{(MeS)₂Gm}(BF)₂ complexes]. Configurations intermediate between trigonal prismatic and trigonal antiprismatic have been deduced for the low-spin iron(II) ion coordination polyhedra of the monoribbed-functionalized clathrochelates using ⁵⁷Fe Moessbauer parameters. The products of de- and re-alkylation reactions of the methylthiol complex FeBd₂{(MeS)₂Gm}(BF)₂ have been identified. The correlation ofE_1/2 values for Fe³⁺/Fe²⁺ couples (from cyclic voltammograms) with Hammettσ_para constants for substituents in the functionalized fragments is discussed.

Full text of DOI:10.1039/b107021p

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Clathrochelate monoribbed-functionalized iron(II) ꢀ-dioximates:
synthetic pathways and structural and electrochemical features†
Yan Z. Voloshin,*a Valery E. Zavodnik,a Oleg A. Varzatskii,b Vitaly K. Belsky,a
Aleksei V. Palchik,b Nataly G. Strizhakova,b Ivan I. Vorontsovc and Mikhail Yu. Antipinc
a Karpov Institute of Physical Chemistry, 10 Vorontsovo Pole, 103064 Moscow, Russia.
E-mail: voloshin@cc.nifhi.ac.ru
b Vernadskii Institute of General and Inorganic Chemistry, 252142 Kiev, Ukraine
c Nesmeyanov Institute of Organoelement Compounds, 117813 Moscow, Russia
Received 2nd August 2001, Accepted 16th January 2002
First published as an Advance Article on the web 19th February 2002
Monoribbed-functionalized (i.e. functionalization of only one of the three α-dioximate fragments) clathrochelate
iron() tris-dioximates have been synthesized starting from the dichloride precursor FeBd2(Cl2Gm)(BF)2 (where
Bd2Ϫ and Cl2Gm2Ϫ are α-benzyldioxime and dichloroglyoxime dianions, respectively), obtained by condensation
of the macrocyclic iron() bis-α-benzyldioximate [FeBd2(BF2)2(MeCN)2] with H2Cl2Gm. Thioalkyl, alkylamine,
oxo- and azaoxocrown ether clathrochelates, as well as the bis-clathrochelate with a 1,5-diaminopentane bridging
fragment, have been characterized using elemental analysis, PD mass, IR, UV-vis, 57Fe Mössbauer and 1H, 13C and
11B NMR spectroscopies, and X-ray crystallography [for the FeBd2(Cl2Gm)(BF)2ؒ2C6H6, FeBd2{(Et2N)ClGm}(BF)2ؒ
C6H6 and FeBd2{(MeS)2Gm}(BF)2 complexes]. Configurations intermediate between trigonal prismatic and
trigonal antiprismatic have been deduced for the low-spin iron() ion coordination polyhedra of the monoribbed-
functionalized clathrochelates using 57Fe Mössbauer parameters. The products of de- and re-alkylation reactions
of the methylthiol complex FeBd2{(MeS)2Gm}(BF)2 have been identified. The correlation of E1/2 values for Fe3ϩ/Fe2ϩ
couples (from cyclic voltammograms) with Hammett σpara constants for substituents in the functionalized fragments
is discussed.
Introduction
Results and discussion
Clathrochelate ribbed-functionalized tris-dioximates have
attracted interest as they offer scope for the synthesis of poly-
nuclear complexes with targeted structural parameters and
physicochemical properties (especially redox characteristics).1,2
However, in most instances it is not necessary to functionalize
all α-dioximate fragments, and it appears to be sufficient to
modify only one of the three ribs in the clathrochelate frame-
work to alter its properties significantly. In particular, such an
approach is thought to be promising in creating new types of
DNA cleavage agents, since in order to intercalate a complex
into a DNA double helix, only one chelate fragment needs to be
functionalized.3 For example, in the majority of ruthenium()
tris-phenanthroline and tris-bipyridine complexes, intensively
studied in recent years in this respect, only one of the three
ligand fragments contains functional groups that exert an
appreciable and directed influence on the physicochemical
characteristics of the whole molecule.4–10
In the strong field of the macrobicyclic tris-dioximate ligands,
Fe2ϩ, Co3ϩ, Co2ϩ and Ru2ϩ ions have low-spin electronic con-
figurations, short M–N distances and form clathrochelates
with similar geometry and chemical properties.11–18 However,
the Fe2ϩ ion has proved to be the most accessible and efficient
template in the synthesis of macrobicyclic tris-dioximate com-
plexes.19,20 It is obvious that pathways developed for obtaining
ribbed-functionalized iron() clathrochelates and reactions for
modifying them should be employable without significant
changes for the synthesis of the corresponding complexes of
the other ions mentioned.
Synthesis
Several feasible synthetic routes to clathrochelate monoribbed-
functionalized tris-dioximates are shown in Scheme 1. It was
established previously21 that a direct template condensation
of a mixture of α-dioximes with Lewis acids on a metal ion
(route I) led to the formation of a poorly separable mixture
of nonsymmetric and symmetric products, in which the latter
predominate. Halogenation of the initial clathrochelate
monoglyoximate 1 (route II) is complicated, since by-products
are readily generated from partial halogenation of a glyoximate
moiety, and the aliphatic and aromatic substituents in the two
other dioximate fragments as well. The methods of preparation
developed for C3-nonsymmetric clathrochelates21 may be used
for the synthesis of tris-dioximates 2 and 3 from square-planar
macrocyclic bis-dioximates (type 4) and would seem to be
the most promising (routes III and IV). Route III makes use of
the condensation of the functionalized α-dioxime with the
previously mentioned bis-complex. However, the appearance of
additional coordinating groups and side reactions associated
with them dramatically reduces the yield of the desired product.
Route IV is free from all these disadvantages. The first stage
produces a reactive dihalogenide precursor 2 that readily
undergoes modification by well-known procedures, hence, this
route was chosen for the synthesis of a series of monoribbed-
functionalized clathrochelate iron() dioximates. The synthesis
of the dichloride precursor 6 was carried out via the first stage
from dichloroglyoxime (H2Cl2Gm) and macrocyclic iron()
bis-α-benzyldioximate 5 [reaction (1)]. Complex 5 was chosen
as the starting compound because of its availability and relative
stability to disproportionation, yielding symmetric FeBd3(BF)2
clathrochelate, a product favoured by the steric effects of the
bulky phenyl substituents.
† Electronic supplementary information (ESI) available: packing
diagrams, NMR and IR data. See http://www.rsc.org/suppdata/dt/b1/
b107021p/
DOI: 10.1039/b107021p
J. Chem. Soc., Dalton Trans., 2002, 1193–1202
This journal is © The Royal Society of Chemistry 2002
1193

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Scheme 1
(1)
the monodiethylamine-containing complex 9. An attempt to
isolate the corresponding disubstituted complexes was not
successful. The monofunctionalized complexes 8 and 9 may
undergo further functionalization, especially with primary
aliphatic amines. The use of primary aliphatic diamines enables
the functionalized spacer-containing clathrochelate 10 and the
bis-clathrochelate 11 (Scheme 2) to be obtained.
The dichloride precursor readily reacted with sterically
unhindered primary amines (n-butylamine in particular) to
form disubstituted products (7).Secondary amines underwent
a reaction that involved substitution of only one of the two
chlorine atoms. The reaction of precursor 5 with an excess of
aza-18-crown-6 (aza-18-C-6) and diethylamine resulted in the
formation of the monocrown-substituted clathrochelate 8 and
1194
J. Chem. Soc., Dalton Trans., 2002, 1193–1202

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Scheme 2
The synthesis of the functionalized macrobicyclic com-
products in an excess of the thiolate ion. This process occurred
pound 12, containing one crown ether dioximate fragment
(Cw), was carried out according to reaction (2) using the
approach proposed previously for triribbed-functionalized
clathrochelates.1
most readily for the methylthiol derivative 13 [reaction (4)].
Complex 13 also readily underwent de- and re-alkylation,
especially with the n-octylthiolate ion (n-OctS) in DMF
(Scheme 3).
Reaction (3) of the precursor 5 with potassium aliphatic
thiolates such as MeSK and n-C8H17SK was complicated by
side reactions, namely the stepwise dealkylation of the resulting
The products of de- and re-alkylation reactions of clathro-
chelate 13 were identified by PD and FAB MS techniques. The
purification can be improved and the yield of the desired
(2)
(3)
J. Chem. Soc., Dalton Trans., 2002, 1193–1202
1195

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(4)
Scheme 3
product increased by addition of the corresponding alkyl iodide
at the final stage of this process.
Crystal and molecular structures
A summary of the X-ray data for the precursor 6 (Fig. 1) and
the functionalized complexes 9 and 13 (Figs. 2 and 3) along with
those for their symmetric and C3-nonsymmetric analogs are
presented in Table 1.
It should be noted first of all that the distortion angle φ
(approximately 25–27Њ) of the iron() coordination polyhedron
[φ = 0Њ for a trigonal prism (TP) and φ = 60Њ for a trigonal
antiprism (TAP)] to a trigonal antiprism for the complexes
synthesized is close to that of the symmetric FeBd3(BF)2
α-benzyldioximate (φ = 29.3Њ). This distortion is roughly half-
way between a TP and a TAP. Meanwhile the Fe–N distances
(approximately 1.91 Å) and bite angles α (half the chelate angle,
ca. 39Њ) in clathrochelates 6, 9 and 13 are typical for boron-
containing iron() tris-dioximates.21–29 As a result, the increased
coordination polyhedron distortion angle causes a squeeze
along the B–Fe–B axes, and the distance h between the
polyhedron bases is minimal in FeBd3(BF)2, Fe{(n-BuNH)2-
Gm}2(Cl2Gm)(BPh)2, FeBd2{(Et2N)ClGm}(BF)2 (9) and
FeBd2{(MeS)2Gm}(BF)2 (13) complexes along with the
maximal distortion angle (Table 1).
Fig. 1 View of 6 with displacement ellipsoids drawn at the 40%
probability level and labeling scheme. H atoms have been omitted for
clarity.
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J. Chem. Soc., Dalton Trans., 2002, 1193–1202

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etry, we utilized the results of indirect methods and, initially,
57Fe Mössbauer spectra. The parameters of these spectra
(Table 1) characterize the compounds obtained as low-spin
complexes of Fe2ϩ ion in the high field of the clathrochelate
ligand. The isomer shift (IS) values, characterizing the
s-electron density on the central metal ion nucleus, are practic-
ally identical for the synthesized C3-nonsymmetric clathro-
chelates and their symmetric analogs, which have been reported
previously.1 The quadrupole splitting (QS), which is determined
by the electric field gradient (EFG) on the iron atom nucleus,
was used30,31 to obtain the geometries of the low-spin iron()
complexes by predicting the magnitude of the distortion angle
φ. The QS values for the synthesized C3-nonsymmetric com-
plexes occupy a position intermediate between the QS values
for the corresponding symmetric analogs (after allowing for the
influence of a substituent at the boron atom). Replacement of
phenyl and n-butyl substituents by fluorine in the case of the
majority of alicyclic and aliphatic α-dioximate clathrochelates
results in an increase in the QS magnitude about 0.1–0.2 mm
Fig. 2 View of 9 with displacement ellipsoids drawn at the 40%
probability level and labeling scheme. H atoms have been omitted for
clarity.
s
Ϫ1. The QS values for the clathrochelates, consideration of the
X-ray analysis data for the symmetric analogs1 and for
FeBd2(Cl2Gm)(BF)2ؒ2C6H6 (6), FeBd2{(Et2N)ClGm}(BF)2ؒ
C6H6 (9) and FeBd2{(MeS)2Gm}(BF)2 (13), the correlation
relationship “QS versus φ”,30 and a modern version of the
partial quadrupole splitting concept,31 allowed the prediction
of the distortion angle φ, listed in Table 1. A positive QS sign
was postulated for all boron-containing clathrochelates. The
geometries of the synthesized complexes were found to be
closer to a trigonal prism than that of the FeBd3(BF)2
clathrochelate.
The slightly increased QS values obtained for the synthesized
compounds compared with those expected can be accounted
for by the fact that the molecules have no C3 symmetry axis
passing through the apical boron atoms and the central iron
ion, and this induces an additional increase in the EFG.
NMR spectra
1
The H and 13C NMR spectra of the complexes (see ESI) con-
tain signals characteristic of both types of dioximate fragments,
which (in addition to the ratio of line integral intensities in the
1H NMR and PD mass spectra) confirmed their composition,
as well as the presence of a C2 symmetry axis passing through
the middle of the C–C bond in the functionalized chelate ring
and the iron atom. The fully nonsymmetric clathrochelates
proved to be the only exception; assignment of the signals
in their 13C NMR spectra was performed by recording these
Fig. 3 View of 13 with displacement ellipsoids drawn at the 30%
probability level and labeling scheme. H atoms have been omitted for
clarity (except hydrogen atoms of methyl groups).
Specific features of the structures for complexes 6 and 9 that
should be highlighted are a tendency for the C–C᎐N angles in
᎐
1
spectra with and without decoupling of the spin–spin H–13C
the chlorine-containing chelate fragments to have larger values
compared to those in phenyl-containing substituents (Table 1).
In 9, the dihedral angle between the plane C7–N7–C9 of the
diethylamine group and that of the C1–Fe1–C2 fragment is
37.7(2)Њ. In the clathrochelates 6, 9 and 13, the phenyl sub-
stitutents have similar mutual orientations: the dihedral angles
between phenyl-substituted and corresponding C–Fe–C frag-
ments are in the range 44.2(4)–60.4(8)Њ (average ∼ 50Њ). The
average inclination of the benzene rings to each other for the
same chelate fragment is approximately 53Њ. Despite the fact
that the molecular geometries of these clathrochelates look in
some respects alike, their molecular packing arrangements are
substantially different (see ESI). There are no specific inter-
molecular interactions in the structures of 6 and 9, but the
molecular packing of complex 13 is characterized particularly
by S ؒ ؒ ؒ F intermolecular contacts of 3.120(6) Å (see ESI). The
negative thermal expansion of the crystal 9 along the a axis in
the range 103–160 K should also be noted.
interaction. The 11B NMR spectra of these compounds (see
ESI) contain two doublets, governed by the spin–spin 11B–19F
interactions, unlike the 11B NMR spectra of other compounds
11B–19
F
that contain one doublet. The low values of the J
con-
stant (approximately 15 Hz) are also characteristic of boron
atoms in a highly symmetric tetrahedral environment.
UV-vis spectra
A single intense Md
Lπ* charge transfer band (CTB) was
evident in the visible region of the UV-vis spectra of the
synthesized clathrochelates. However, with certain C3-non-
symmetric clathrochelates, two bands of nearly identical
intensity have been detected in other studies.21 These arise from
metal to ligand charge transfer into the π*-orbitals of different
types of dioximate fragments. In all other instances, only one
band was observed, with λmax intermediate between the values
found for the corresponding symmetric clathrochelate tris-
dioximates.21 An analogous situation was observed for the
complexes described herein. The position of the CTB in the
UV-vis spectra depends somewhat on the nature of the capping
group, and therefore the resemblance between the λmax values
of the compounds synthesized and those of the FeBd3(BF)2
57Fe Mössbauer spectra
Attempts to obtain crystals of other synthesized monoribbed-
functionalized complexes suitable for X-ray analysis were not
successful. Therefore, to obtain information about their geom-
J. Chem. Soc., Dalton Trans., 2002, 1193–1202
1197

Table 1 Parameters of 57Fe Mössbauer spectra and the main X-ray data for the complexes obtained and their analogs
X-Ray crystallographic data
Average structural parameters of capping
fragments
57Fe Mössbauer data
Average structural parameters of chelating fragments
IS/
QS/
φ found
(calc.)/Њ
O–B–C
(O–B–F)/Њ
Compound
mm sϪ1
mm sϪ1
ha/Å αb/Њ
∆c/Å
N᎐C–C᎐Nd/Њ
Fe–N/Å
C–C/Å
C᎐N/Å
᎐
C–C᎐N/Њ N–O/Å
B–O/Å
O–B–O/Њ
᎐
᎐
᎐
Fe(Cl2Gm)3(BF)2ؒ2THF1
Fe{(n-BuNH)2Gm}2(Cl2Gm)(BPh)2
(type A)1
0.37
0.38
0.64
0.69
17.1
27.3
2.36 39.0
2.33 39.5
0.083
0.102
8.1
9.8
1.91
1.92
1.429
1.427
1.276
1.306
112.3
111.5
1.370
1.362
1.464
1.500
108.0
108.7
110.9
110.2
40.3
(Cl2Gm) 0.282
39.0
(Cl2Gm)
(N2Gm)
(Cl2Gm)
26.8
(N2Gm)
(N2Gm)
10.0
1.89
(Cl2Gm)
1.96
(N2Gm)
1.91
(Cl2Gm)
1.458
(N2Gm)
(Cl2Gm)
1.305
(N2Gm)
(Cl2Gm)
1.396
(N2Gm)
(N2Gm) (N2Gm)
Fe{(n-BuNH)2Gm}2(Cl2Gm)(BPh)2
0.38
0.69
29.2
2.30 39.5
0.105
1.435
1.304
111.3
1.367
1.490
1.49
108.4
107
110.7
(type B)1
40.4
(Cl2Gm)
(Cl2Gm)
19.2
19.6
(N2Gm)
13.8
1.89
(Cl2Gm)
1.93
(N2Gm)
1.91
(Cl2Gm)
1.476
(N2Gm)
(Cl2Gm)
1.291
(N2Gm)
(Cl2Gm)
1.400
(N2Gm)
(Cl2Gm) 0.203
39.0 0.206
(N2Gm) (N2Gm)
22
FeBd3(BF)2
0.32
0.35
0.25
0.62
29.3
24.8
2.29 39.3
0.15
1.51
1.25
1.32
110
1.38
112
FeBd2(Cl2Gm)(BF)2ؒ2C6H6 (6)
2.33 39.3
0.08
0.08
7.7(2)
7.6(2)
(Cl2Gm)
7.8(2)
1.909(1)
1.913(1)
(Cl2Gm)
1.908(1)
(Ph2Gm)
1.909(3)
1.924(3)
(ClGm)
1.924(3)
(NGm)
1.900(3)
1.902(5)
1.898(5)
1.435(2)
(Cl2Gm)
1.456(2)
1.301(2)
(Cl2Gm) (Cl2Gm)
1.312(2) 111.1(1)
112.6(1)
1.370(2) 1.486(2) 108.0(2)
110.9(2)
(Cl2Gm)
0.08
(Ph2Gm) (Ph2Gm)
0.09
(ClGm)
0.10
(NGm)
0.12
(Ph2Gm)
0.05
(Ph2Gm) (Ph2Gm) (Ph2Gm)
FeBd2{(Et2N)ClGm}(BF)2ؒC6H6 (9)
0.34
0.32
0.31
0.36
26.6
25.8
2.31 39.3
9.2(5)
(ClNGm)
10.6(5)
1.447(6)
(ClNGm) (NGm)
1.464(6) 1.281(5)
(Ph2Gm) (ClGm)
1.309(5)
1.323(5)
109.7(4)
(NGm)
113.9(4)
(ClGm)
110.8(4)
1.374(4) 1.483(6) 107.9(4)
111.2(3)
111.8(5)
(Ph2Gm)
(Ph2Gm) (Ph2Gm)
1.321(8) 111.8(6)
(Ph2Gm) (Ph2Gm) (Ph2Gm)
FeBd2{(MeS)2Gm}(BF)2 (13)
2.31 39.3
3.9
1.42(1)
1.373(7) 1.479(9) 107.0(6)
(Ph2Gm) (Ph2Gm)
0.07
(S2Gm)
6.7
(S2Gm)
(Ph2Gm) 1.46(1)
1.283(8)
(S2Gm)
111.7(4)
(S2Gm)
1.910(8)
(S2Gm)
(S2Gm)
FeBd2{(n-BuNH)2Gm}(BF)2 (7)
FeBd2{(aza18-C-6)ClGm}(BF)2 (8)
FeBd2{(Et2N)[NH2(CH2)5NH]Gm}-
(BF)2 (10)
[FeBd2{(Et2N)Gm}(BF)2]2NH(CH2)5-
NH (11)
0.35
0.34
0.34
0.76
0.45
0.53
(24–29)
(24–29)
(24–29)
0.34
0.47
(24–29)
FeBd2(CwGm)(BF)2 (12)
FeBd2{(n-OctS)2Gm}(BF)2 (14)
0.36
0.32
0.50
0.34
(24–29)
(26–31)
a Distance between the coordination polyhedron bases (the height of the distorted trigonal prism). b Bite angle (half the chelate angle). c Mean deviation of the coordinated nitrogen atoms from the C–Fe–C plane.
d Dihedral angles for the chelating fragments.

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Table 2 The electrochemical characteristics of clathrochelate iron() α-benzyldioximates (in CH2Cl2)
Tomesˇ
criterion/
mV
E1/2
mV
/
a
a
Compound
σI
σpara
FeBd2(Cl2Gm)(BF)2 (6)
0.47
0.10
0.227
Ϫ0.63
1100
400
70
FeBd2{(n-BuNH)2Gm}(BF)2 (7)
75
375b
720
60b
56
FeBd2{(aza18-C-6)ClGm}(BF)2 (8)
0.06 (aza)
0.47 (Cl)
0.47 (Cl)
0.06 (Et2N)
0.06 (Et2N)
0.10 [NH(CH2)5NH2]
0.06 (Et2N)
0.10 [NH(CH2)5NH]
0.38
Ϫ0.95 (aza)
0.227 (Cl)
0.227 (Cl)
Ϫ0.95(Et2N)
Ϫ0.95 (Et2N)
Ϫ0.63 [NH(CH2)5NH2]
Ϫ0.95 (Et2N)
Ϫ0.63 [NH(CH2)5NH]
Ϫ0.32
0.26
0.26
0.08
0.08
Ϫ0.36
Ϫ0.36
Ϫ0.79
Ϫ0.79
·
·
·
·
·
·
·
·
720
430
450
56
56
56
FeBd2{(Et2N)ClGm}(BF)2 (9)
FeBd2{(Et2N)[NH2(CH2)5NH]Gm}(BF)2 (10)
[FeBd2{(Et2N)Gm}(BF)2]2NH(CH2)5NH (11)
FeBd2(CwGm)(BF)2 (12)
FeBd2{(MeS)2Gm}(BF)2 (13)
FeBd2{(n-OctS)2Gm}(BF)2 (14)
800
880
90
70
100
60b
65
0.19
0.17
0.00
Ϫ0.06
920
890b
1040
890
FeBd2Gm(BF)2
0
0
c
FeBd2Nx(BF)2
FeBd3(BF)2
Ϫ0.05
0.10
Ϫ0.15
Ϫ0.01
56
21, c
925
100
70b
60
940b
875
21
FeBd2Dm(BF)2
Ϫ0.05
Ϫ0.17
900b
70b
a Taft (σI) and Hammett (σpara) constants for substituents in α-dioximate fragments. σΣ = [n/(m ϩ n)]σ1 ϩ [m/(m ϩ n)]σ2, σn
= σn/2.5. b Data for
ϩ
1
solution in acetonitrile. c Nx2Ϫ and Dm2Ϫ are cyclohexanedion-1,2-dioxime (nioxime) and dimethylglyoxime dianions, respectively.
complex is obvious, unlike the λmax values for the triribbed-
functionalized clathrochelates. This indicates that the influence
of two diphenylglyoximate fragments on the electronic system
of a highly conjugated macrobicyclic ligand predominates over
that of the functionalized fragment.
Electrochemistry
Most of the clathrochelates synthesized undergo quasi-
reversible or irreversible oxidations, which are comparable to
those observed for other clathrochelate iron() complexes. They
are assigned to metal-based Fe3ϩ/2ϩ redox couples.1,11,13,14 Their
electrochemical properties are characterized by the half-wave
potential value, E1/2, which depends on the electron-donating
properties of the substituents both in the capping groups and
α-dioximate fragments. Table 2 lists these E1/2 values for various
clathrochelates as well as the Tomesˇ criterion values (∆E),
which characterize the reversibility of an electrochemical
process (the Tomesˇ criterion is determined as ∆E = E3/4 Ϫ E1/4
and for a one-electron reversible process, this value is equal to
56 mV at 298 K32–34).
Fig. 4 Correlation of E1/2 for Fe3ϩ/Fe2ϩ couples of the monoribbed-
functionalized fluoroboronic clathrochelates with the Hammett σpara
constants for the substituents in the functionalized α-dioximate
fragments.
As can be seen from Table 2, the oxidation process for most
of the fluoroboron-containing clathrochelates is reversible (∆E
= 56–60 mV) or quasi-reversible (∆E = 65–75 mV). For these
complexes, except FeBd2(Cl2Gm)(BF)2 (6) and FeBd2Gm(BF)2,
the reduction waves were observed on reversing the potential
scan. Both direct and reverse waves were reproduced under
repeated cycling. However, the FeBd2(Cl2Gm)(BF)2 (6) and
FeBd2Gm(BF)2 clathrochelate oxidation processes were
accompanied by destruction of the oxidation products, since
there were no reverse waves were observed in the voltammo-
grams, moreover, the working electrode was also passivated.
The complexes FeBd2(CwGm)(BF)2 (12), FeBd2{(n-OctS)2-
Gm}(BF)2 (14) and FeBd3(BF)2 also oxidised irreversibly in
methylene dichloride, which was evident from both the Tomesˇ
criterion values (90–100 mV) and from the absence of reverse
waves. However, a reverse wave for the FeBd2{(n-OctS)2Gm}-
(BF)2 (14) complex was registered in acetonitrile, and both
direct and reverse waves were reproducible. Thus, the stability
of the oxidation product in acetonitrile is clearly higher than
that in methylene dichloride (in cyclic voltammetry time scale).
The E1/2 values for the complexes correlate reasonably well
with the Hammett σpara constants of substituents in the
functionalized fragment (the correlation coefficient is 0.94;
Fig. 4), though there was no correlation between the E1/2 values
and the inductive Taft σI constants.
Experimental
General procedures
The reagents used, FeCl2ؒ4H2O, α-benzyldioxime (H2Bd),
C6H5SH, MeSH, BF3ؒOEt2, sorbents, 1-aza-18-crown-6
(abbreviated as aza-18-C-6), 1,5-diaminopentane (cadaverine),
organic bases and their salts, and organic solvents were
obtained commercially (Fluka). Bis[2-(o-oxyphenoxy)]diethyl
ether and the [Fe(HBd)2py2] complex were prepared as
described in refs. 35 and 36, respectively. The dichloroglyoxime
(denoted as H2Cl2Gm) was obtained by chlorination of
glyoxime (H2Gm) as described in ref. 37.
Analytical data (C, H, N content) were obtained with a Carlo
Erba model 1106 microanalyzer. Iron content was determined
spectrophotometrically.
J. Chem. Soc., Dalton Trans., 2002, 1193–1202
1199

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The plasma desorption (PD) mass spectra were recorded in
the positive spectral range using a BC MS SELMI time-of-
flight biochemical mass spectrometer and an accelerating
voltage of 20 kV. The ionization was induced by 252Cf spon-
taneous decay fragments, and typically 20 000 decay acts were
registered. The samples (approximately 1–2 mg) were applied to
a gilded disk or a nitrocellulose layer.
ether and then with hexane, and dried in vacuo. Yield: 23 g
(63%). Anal. calc. for C30H20N6O6B2Cl2F2Fe: C, 48.23; H, 2.68;
N, 11.25; Cl, 9.51; Fe, 7.48; found: C, 48.21; H, 2.73; N, 11.17;
Cl, 9.42; Fe, 7.38%. MS(PD): m/z 747 [M]ϩ , 624 [M Ϫ
ؒ
Cl2C2N2]ϩ . UV-vis (CHCl3): λmax (10Ϫ3 ε) 243 (25), 283 (12), 428
ؒ
(3.4), 469 nm (23 dm3 molϪ1 cmϪ1).
The IR spectra of solid samples (KBr tablets) in the range
400–4000 cmϪ1 were recorded with a Specord M-80 Carl Zeiss
spectrophotometer.
UV-vis spectra of solutions in chloroform were recorded
in the range 230–800 nm with a Lambda 9 Perkin Elmer
spectrophotometer. The individual Gauss components of these
spectra were calculated using the SPECTRA program.38
The 1H, 13C and 11B NMR spectra were recorded from CDCl3
solutions with a Bruker AC-200 FT-spectrometer.
FeBd2{(n-BuNH)2Gm}(BF)2 (7). Complex 6 (0.75 g, 1 mmol)
was suspended in acetonitrile (20 ml), and an excess of
n-butylamine (1 ml) was added. The reaction mixture was
left overnight and then refluxed for 2 h. The resulting dark-red
solution was precipitated with a 5-fold volume of water. The
solid was filtered off, dried in vacuo and dissolved in chloro-
form. The solution was filtered through Silasorb SPH-300 and
evaporated to dryness. Yield: 0.73 g (90%). Anal calc. for
C38H40N8O6B2F2Fe: C, 55.65; H, 4.88; N, 13.67; Fe, 6.81; found:
57Fe Mössbauer spectra were obtained with a YGRS-4M
spectrometer with a constant acceleration mode. The spectra
were collected with a 256-multichannel amplitude analyzer. The
isomer shift was measured relative to sodium nitroprusside, and
an α-Fe foil was used for the velocity scale calibration. 57Co in a
Cr matrix was used as the source, which was always kept at
room temperature. The minimal absorption line-width in the
spectrum of a standard sample of sodium nitroprusside was
C, 55.71; H, 4.88; N, 13.57; Fe, 6.82%. MS(PD): m/z 819 [M]ϩ
.
ؒ
UV-vis (CHCl3): λmax (10Ϫ3 ε) 249 (27), 292 (19), 365 (5.5), 432
(3.4), 506 nm (20 dm3 molϪ1 cmϪ1).
FeBd2{(aza18-C-6)ClGm}(BF)2 (8). Complex 6 (0.75 g, 1
mmol) and aza-18-C-6 (0.53 g, 2 mmol) were dissolved/
suspended in dry acetonitrile (15 ml) and left overnight. Then,
the reaction mixture was refluxed for 3 h and evaporated to 3
ml. Triethylamine (0.5 ml) was added, and the dark-red product
was precipitated with methanol (10 ml). The solid was washed
with a small amount of diethyl ether, and then with hexane,
and dried in vacuo. Yield: 0.65 g (70%). Anal calc. for
C42H44N7O11B2ClF2Fe: C, 51.80; H, 4.52; N, 10.07; Cl, 3.65; Fe,
5.74; found: C, 51.77; H, 4.52; N, 9.94; Cl, 3.66; Fe, 5.77%.
0.24 mm sϪ1
.
Cyclic voltammograms were recorded in methylene dichlor-
ide and acetonitrile under argon using a PI-50-1 potentiostat
coupled with a B7-45 tera-ohmic potentiometer as the current
voltage convertor. The scan rate was varied from 5 to 10 mV sϪ1
,
which is close to the steady-state conditions for ultramicro-
electrodes.34 Tetraethylammonium tetrafluoroborate (0.1 M)
was used as the supporting electrolyte. A platinum micro-
electrode 10 µm in diameter, thoroughly polished and rinsed
before measurements, was chosen as the working electrode.
A platinum wire was used as the auxiliary electrode. A standard
Ag/AgCl reference electrode was connected to the cell via a salt
bridge. All potentials were referenced to the redox potential of
the ferrocene (Fcϩ/Fc) couple as an internal standard. This
potential is at ϩ0.58 (for CH2Cl2 solutions) and ϩ0.45 V (for
MeCN solutions) vs. Ag/AgCl under the present experimental
conditions.
MS(PD): m/z 973 [M]ϩ . UV-vis (CHCl3): λmax (10Ϫ3 ε) 249 (27),
ؒ
288 (18), 347 (4.5), 484 nm (24 dm3 molϪ1 cmϪ1).
FeBd2{(Et2N)ClGm}(BF)2 (9). Complex 6 (0.75 g, 1 mmol)
and an excess of diethylamine (0.5 ml) were dissolved/
suspended in dry DMF (15 ml) and left overnight. Then the
reaction mixture was stirred for 7 h at 50 ЊC and the resulting
dark-orange solution was precipitated with a 2-fold volume of
water. The solid was filtered off and reprecipitated from DMF
solution with saturated aqueous NaClO4 solution. The result-
ing orange product was washed with water and a small amount
of methanol, and dried in vacuo. The solid was dissolved in
chloroform, and the solution was filtered through Silasorb
SPH-300 and evaporated to dryness. The solid residue was
washed with a small amount of chloroform, and then with
hexane, and dried in vacuo. Yield: 0.32 g (41%). Anal. calc. for
C34H30N7O6B2ClF2Fe: C, 52.11; H, 3.83; N, 12.52; Cl, 4.53; Fe,
Syntheses
[FeBd2(BF2)2(MeCN)2] (5). This compound was obtained
by a procedure similar to that used to prepare the [FeDm2-
(BF2)2(MeCN)2] complex.39
The complex [Fe(HBd)2py2] (108 g, 156 mmol) was sus-
pended in a dry diethyl ether–acetonitrile mixture (6 : 1, 700 ml)
with intensive stirring and freshly distilled BF3ؒOEt2 (85.4 ml,
690 mmol) was added dropwise under argon. The reaction
mixture was stirred for 30 min and filtered. The solid product
was washed with diethyl ether (200 ml), acetone–acetonitrile
mixture (9 : 1, 1000 ml in five portions), diethyl ether–aceto-
nitrile mixture (20 : 1; 150 ml in three portions), hexane–
hexamethyldisiloxane mixture (50 : 1, 100 ml in two portions)
and then with hexane (100 ml), and dried in vacuo. Yield: 96 g
(87%).
7.13; found: C, 51.98; H, 3.81; N, 12.42; Cl, 4.59; Fe, 7.12%.
ϩ
MS(PD): m/z 783 [M]ϩ , 748 [M Ϫ Cl] , 624 [M Ϫ ClC2-
ؒ
ؒ
ϩ ϩ
N2NEt2]ϩ . MS(MALDI-TOF): m/z 784 [M ϩ H ] , 806 [M ϩ
ؒ
Naϩ]ϩ, 822 [M ϩ Kϩ]ϩ. UV-vis (CHCl3): λmax (10Ϫ3 ε) 254 (28),
294 (14), 338 (4.0), 484 nm (22 dm3 molϪ1 cmϪ1).
FeBd2{(Et2N)[NH2(CH2)5NH]Gm}(BF)2 (10). Complex
9
(0.23 g, 0.3 mmol) and an excess of cadaverine (0.7 ml) were
dissolved/suspended in dry DMF (10 ml) and left overnight.
Then the resulting dark-red solution was precipitated with a
2-fold volume of water. The solid was filtered off and repre-
cipitated from DMF solution with saturated aqueous NaClO4
solution. The resulting red product was washed with methanol–
water (1 : 1) mixture, and dried in vacuo. The solid was dissolved
in chloroform and the solution was passed through a 30 mm
layer of Silasorb SPH-300. The chloroform elute was discarded
and the desired complex eluted with acetonitrile–chloroform
(1 : 3) mixture. The red solution was evaporated to dryness and
dissolved in a small amount of chloroform. The chloroform
solution obtained was diluted with a 3-fold volume of hexane
and evaporated to dryness. The solid residue was washed with
hexane and dried in vacuo. Yield: 0.055 g (22%). Anal. calc. for
C39H43N9O6B2F2Fe: C, 55.16; H, 5.07; N, 14.85; Fe, 6.58; found:
FeBd2(Cl2Gm)(BF)2 (6). Complex 5 (35 g, 50 mmol) and an
excess of H2Cl2Gm (9.4 g, 60 mmol) were dissolved/suspended
in a dry nitromethane–hexamethyldisiloxane mixture (6 : 1, 175
ml) with intensive stirring under argon. Triethylamine (21 ml,
150 mmol), BF3ؒOEt2 (18.6 ml, 150 mmol) and chloroform
(20 ml) were added dropwise to the reaction mixture. The
solution was heated to boiling point and a second portion of
BF3ؒOEt2 (18.6 ml, 150 mmol) was added. Then, 120 ml of
solvent was distilled off with intensive stirring and the mixture
was allowed to cool to room temperature. The microcrystalline
orange solid was filtered off, washed with methanol, diethyl
1200
J. Chem. Soc., Dalton Trans., 2002, 1193–1202

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Table 3 Crystallographic data and experimental details for FeBd2(Cl2Gm)(BF)2ؒ2C6H6 (6), FeBd2{(Et2N)ClGm}(BF)2ؒC6H6 (9) and FeBd2-
{(MeS)2Gm}(BF)2 (13)
Data
6
9
13
Empirical formula
Fw
C42H32B2Cl2F2FeN6O6
903.11
C40H36B2ClF2FeN7O6
861.68
C32H26B2F2FeN6O6S2
770.18
Color, habit
Crystal dimensions/mm
Temperature/K
Dark-orange, prism
0.07 × 0.15 × 0.40
110
Dark-orange, prism
0.50 × 0.50 × 0.20
120
Orange–red, prism
0.42 × 0.38 × 0.32
293
a/Å
b/Å
c/Å
14.754(2)
10.339(1)
27.126(3)
90.942(2)
4137.1(8)
4
17.077(3)
21.551(4)
21.580(4)
90
7942(2)
8
9.993(1)
9.993(1)
34.575(7)
90
3452.7(9)
4
β/Њ
V/Å3
Z
Crystal system
Space group
Dcalc/g cmϪ3
µ/mmϪ1
Data/restraints/parameters
Weighting scheme
Monoclinic
P21/c
1.450
Orthorhombic
Pbca
1.441
Tetragonal
P41212
1.482
0.559
0.514
0.622
12081/0/678
9127/0/532
2402/0/231
2
2
2
1/[σ2(Fo ) ϩ (0.0804P)2ϩ 0.1263P],
1/[σ2(Fo ) ϩ (0.1243P)2ϩ 2.3045P],
1/[σ2(Fo ) ϩ (0.1348P)2ϩ 3.0994P],
P = (Fo2 ϩ 2Fc2)/3
P = (Fo2 ϩ 2Fc2)/3
P = (Fo2 ϩ 2Fc2)/3
0.0560
Ra [I > 2σ(I )]
Rw b [I > 2σ(I )]
F(000)
0.0426
0.1119
1848
1.068
—
0.0635
0.1884
3552
1.206
—
0.1696
1576
1.106
0.00(4)
GOFc
Absolute structure parameter
2
a R = (Σ Fo| Ϫ |Fc )/Σ|Fo|. b Rw = [(Σ [w(Fo2 Ϫ Fc2)2])/(Σ[w(Fo )2])]1/2
.
c GOF = [(Σ [w (Fo2 Ϫ Fc2)2])/(Nobs Ϫ Nparam)]1/2
.
C, 55.18; H, 5.03; N, 14.74; Fe, 6.62%. MS(PD): m/z 848 [M]ϩ
.
C46H36N6O11B2F2Fe: C, 57.30; H, 3.74; N, 8.72; Fe, 5.79; found:
ؒ
UV-vis (CHCl3): λmax (10Ϫ3 ε) 243 (26), 296 (11), 343 (4.6), 469
C, 57.22; H, 3.77; N, 8.63; Fe, 5.87%. MS(PD): m/z 964 [M]ϩ
.
ؒ
(5.1), 512 nm (14 dm3 molϪ1 cmϪ1).
UV-vis (CHCl3): λmax (10Ϫ3 ε) 261 (27), 295 (15), 340 (4.6), 437
(7.0), 488 nm (20 dm3 molϪ1 cmϪ1).
[FeBd2{(Et2N)Gm}(BF)2]2NH(CH2)5NH (11). Complex
9
(0.23 g, 0.3 mmol) was dissolved/suspended in dry DMF
(10 ml) and solution of cadaverine (0.018 ml, 0.15 mmol) and
triethylamine (0.042 ml, 0.3 mmol) in DMF (5 ml) was added
dropwise to the stirred reaction mixture. The reaction mixture
was left overnight and then was stirred at 50–60 ЊC for 3 h. The
product was precipitated from the resulting red solution with a
2-fold volume of water and the solid reprecipitated from DMF
solution with saturated aqueous NaClO4 solution. The result-
ing red product was washed with a small amount of methanol
and dried in vacuo. The solid was dissolved in chloroform and
the solution filtered through Silasorb SPH-300 and the orange–
red solution evaporated to dryness. The solid residue was
washed with hexane and dried in vacuo. Yield: 0.06 g (40%).
Anal. calc. for C73H72N16O12B4F4Fe2: C, 54.93; H, 4.51; N,
14.05; Fe, 7.00; found: C, 54.81; H, 4.48; N, 13.98; Fe, 7.07%.
FeBd2{(MeS)2Gm}2(BF)2 (13). Solutions of t-C5H11OK (3 ml,
1 M in THF) and MeSH (2 ml, 10% in THF) were added to dry
THF (10 ml) under argon and the reaction mixture was cooled
to Ϫ20 ЊC. Complex 6 (0.75 g, 1 mmol) was added to the
solution, and the reaction mixture was stirred for 2 h at room
temperature and refluxed for 2 h. Then 5 ml of solvent was
distilled off, the reaction mixture was cooled to room temper-
ature and MeI (0.5 ml) and K2CO3 (0.2 g) were added. After
stirring for 2 h, the reaction mixture was diluted with ethanol
(10 ml). Acetic acid (0.5 ml) was added and the reaction mixture
was heated to boiling point. The dark-orange solid was precipi-
tated with water (5 ml), added dropwise. The reaction mixture
was left for 3 h at 0 ЊC and filtered. The product was washed
with ethanol and hexane, dried in vacuo and dissolved in
chloroform. The solution was filtered through Silasorb
SPH-300 and evaporated to dryness. Yield: 0.58 g (76%). Anal.
calc. for C32H26N6O6B2F2FeS2: C, 49.90; H, 3.38; N, 10.92; Fe,
7.25; found: C, 49.92; H, 3.33; N, 10.87; Fe, 7.21%. MS(PD):
MS(PD): m/z 1595 [M]ϩ . MS(MALDI-TOF): m/z 1596 [M ϩ
ؒ
Hϩ]ϩ, 1618 [M ϩ Naϩ]ϩ, 1634 [M ϩ Kϩ]ϩ. UV-vis (CHCl3): λmax
(10Ϫ3 ε) 245 (60), 296 (23), 351 (9.0), 453 (6.5), 499 nm (36 dm3
molϪ1 cmϪ1).
m/z 770 [M]ϩ . UV-vis (CHCl3): λmax (10Ϫ3 ε) 258 (26), 291 (17),
ؒ
321 (4.0), 391 (4.2), 486 nm (27 dm3 molϪ1 cmϪ1).
FeBd2(CwGm)(BF)2 (12). Bis[2-(o-oxyphenoxy)]diethyl ether
(0.41 g, 1.43 mmol) was added to a solution of sodium meth-
oxide, prepared from metallic sodium (0.07 g, 3.0 mmol) and
dry methanol (15 ml). The reaction mixture was refluxed for
30 min and evaporated to dryness, and solid residue was left at
90–100 ЊC for 1 h in vacuo. The resulting salt and complex 6
(1.0 g, 1.3 mmol), along with the interphase carrier (n-Bu4N)Cl
(0.36 g), were dissolved/suspended in dry THF (100 ml) at Ϫ20
ЊC. The reaction mixture was stirred for 2 h at this temperature
and for 5 h at 50 ЊC, cooled to room temperature and filtered.
The filtrate was evaporated to dryness. The solid was washed
with water, methanol, a small amount of diethyl ether and then
with hexane. The chloroform solution of the product obtained
was filtered through Silasorb SPH-300 and evaporated to dry-
ness, dissolved in chloroform–hexane mixture (1 : 1, 50 ml) and
filtered. The filtrate was evaporated to dryness, washed with
hexane and dried in vacuo. Yield: 0.15 g (12%). Anal. calc. for
FeBd2{(n-OctS)2Gm}(BF)2 (14). A solution of t-C5H11OK (2
ml, 1 M in THF) and n-C8H17SH (n-OctSH, 0.38 ml, 2.2 mmol)
were dissolved in dry THF (10 ml) under argon. The complex
FeBd2(Cl2Gm)(BF)2 (0.75 g, 1 mmol) was added, and the
reaction mixture was stirred for 3 h at room temperate and
refluxed for 2 h. The solid product was precipitated with dilute
acetic acid (50 ml, 2% in water) and dissolved in chloroform.
The dried chloroform solution was filtered through Silasorb
SPH-300 and evaporated to ca. 1.5 ml. The orange product was
precipitated with pentane, washed with pentane and dried
in vacuo. Yield: 0.56 g (62%). Anal. calc. for C46H54N6O6B2F2-
FeS2: C, 57.18; H, 5.59; N, 8.70; Fe, 5.78; S, 6.63; found: C,
57.02; H, 5.51; N, 8.68; Fe, 5.70; S, 6.53%. MS(PD): m/z 966
[M]ϩ . UV-vis (CHCl3): λmax (10Ϫ3 ε) 245 (17), 286 (17), 378
ؒ
(3.7), 484 nm (26 dm3 molϪ1 cmϪ1).
J. Chem. Soc., Dalton Trans., 2002, 1193–1202
1201

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9 D. Burdinski, E. Bothe and K. Wieghardt, Inorg. Chem., 2000, 39,
105.
X-Ray crystallography
Details of the crystal data collection and refinement parameters
for FeBd2(Cl2Gm)(BF)2ؒ2C6H6 (6), FeBd2{(Et2N)ClGm}(BF)2ؒ
C6H6 (9) and FeBd2{(MeS)2Gm}(BF)2 (13) complexes are listed
in Table 3. Single crystals of these complexes were grown
from benzene–iso-octane (6 and 9) and methylene dichloride–
heptane (13) mixtures at room temperature.
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T. A. Bish, P. A. Finnegan, M. L. Hartenstein, C. S. Regitz, D. M.
Ryalls, M. E. Squires and H. J. Thomas, Inorg. Chem., 1993, 32,
5266.
15 C. Engtrakul, W. J. Shoemaker and J. J. Grzybowski, Inorg. Chem.,
2000, 39, 5161.
16 P. Chaudhuri, M. Winter, B. P. C. Della Vedova, P. Fleischhauer,
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19 N. A. Kostromina, Ya. Z. Voloshin and A. Y. Nazarenko,
Clathrochelates: Synthesis, Structure, Properties; Naukova Dumka,
Kiev, 1992.
20 N. V. Gerbeleu, V. B. Arion and F. J. Burgess, Template Synthesis of
Macrocyclic Compounds, Wiley-VCH, Weinheim, 2000.
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Acta, 1991, 184, 107.
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Y. A. Maletin and S. G. Kozachkov, J. Organomet. Chem., 1997, 536/
537, 207.
24 Ya. Z. Voloshin, M. I. Terekhova, Y. G. Noskov, V. E. Zavodnik and
V. K. Belsky, An. Quim., Int. Ed., 1998, 94, 142.
25 S. V. Linderman, Yu. T. Struchkov and Ya. Z. Voloshin,
Pol. J. Chem., 1993, 67, 1575.
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Chim. Acta, 1990, 170, 181.
31 A. Yu. Nazarenko, E. V. Polshin and Ya. Z. Voloshin, Mendeleev
Commun., 1993, 45.
Single-crystal X-ray diffraction experiments for complexes 6
and 9 were carried out with a Bruker SMART 1K CCD area
detector mounted on a 3-circle diffractometer, using graphite
monochromated Mo-Kα radiation (λ = 0.71073 Å). The data
collection nominally covered a hemisphere of reciprocal space40
by a combination of three sets of ω scans (step 0.3Њ), each set at
different φ angles (2θmax = 60 and 55Њ for crystals 6 and 9,
respectively). The temperature was maintained with a Cryo-
stream open-flow N2 gas cryostat (Oxford Cryosystems).
Reflection intensities were integrated using SAINT software40
and corrected for absorption by semi-empirical method
(SADABS program41) based on multiple measurements of
identical reflections and Laue equivalents. Data for a single
crystal of clathrochelate 13 were collected at 293 K on a CAD4
diffractometer using Mo-Kα (β-filtered) radiation (λ = 0.71073
Å) with θ/2θ scans (2θmax = 52Њ).
The structures were solved by the direct method and refined
by full-matrix least squares against F 2 of all data, using
SHELXTL software.42 Non-hydrogen atoms were refined with
anisotropic displacement parameters and hydrogen atoms with
isotropic ones for all structures, where a riding model was used.
In 9, there were some residual peaks of electron density, which
were situated near the nitrogen atom of the diethylamine group
and might be due to unresolved disorder of this fragment. The
nonequivalence of the C–N bond lengths in this group and
the large anisotropic displacement parameters probably have
the same cause. The unit cells of structures 6 and 9 contain one
crystallographically independent molecule of the clathrochelate
and a solvent benzene in a general position. The molecule of
complex 13 is situated in a special position on the 2-fold axis.
CCDC reference numbers 163718–163720.
See http://www.rsc.org/suppdata/dt/b1/b107021p/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
Support from the Russian Fund for Basic Research (grants
N99-03-32498, 00-03-32807 and 00-03-32578) is gratefully
acknowledged.
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