Coordination chemistry of anticrowns. Complexation of cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 with the cyanoborohydride anion [H3BCN]- and triethylamineborane Et3NBH3

Article abstract of DOI:10.1007/s11172-008-0365-4

As was shown by IR spectroscopy, the reaction of the three-mercury anticrown (o-C₆F₄Hg)₃ (1) with the [H ₃BCN]ion in THF affords the complexes {[(o-C₆F ₄Hg)₃][H₃BCN](5) and [(o-C₆F ₄Hg)₃]₂[H₃BCN](6). Complex 6 was isolated from solution in the analytically pure state. According to X-ray diffraction data, complex 6 has a double-decker sandwich structure, in which the borohydride group of the [H₃BCN]^- anion is bound to one anticrown molecule by three B-H-Hg bridges, whereas the cyanide group is cooperatively coordinated by three mercury centers of another molecule 1 through the nitrogen atom. The reaction of compound 1 with triethylamineborane Et ₃NBH₃ in THF affords the 1: 1 complex {[(o-C ₆F₄Hg)₃][Et₃NBH₃]} (7). In this adduct, the binding of the aminoborane to the mercury anticrown is also accomplished by B-H-Hg bridges. The stability constants of complexes 5 and 6 in THF were determined.

Full text of DOI:10.1007/s11172-008-0365-4

Russian Chemical Bulletin, International Edition, Vol. 57, No. 12, pp. 2540—2547, December, 2008
2540
Coordination chemistry of anticrowns. Complexation of
cyclic trimeric perfluoroꢀoꢀphenylenemercury (oꢀC6F4Hg)3
with the cyanoborohydride anion [H3BCN]–
and triethylamineborane Et3NBH3
V. N. Tsupreva, O. A. Filippov, F. M. Dolgushin, K. I. Tugashov, A. I. Krylova, V. I. Bragin,
I. A. Tikhonova, V. B. Shur, L. M. Epstein, and E. S. Shubina
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5085. Eꢀmail: vbshur@ineos.ac.ru; shu@ineos.ac.ru
As was shown by IR spectroscopy, the reaction of the threeꢀmercury anticrown (oꢀC6F4Hg)3
(1) with the [H3BCN]– ion in THF affords the complexes {[(oꢀC6F4Hg)3][H3BCN]}– (5) and
{[(oꢀC6F4Hg)3]2[H3BCN]}– (6). Complex 6 was isolated from solution in the analytically pure
state. According to Xꢀray diffraction data, complex 6 has a doubleꢀdecker sandwich structure,
in which the borohydride group of the [H3BCN]– anion is bound to one anticrown molecule
by three B—H—Hg bridges, whereas the cyanide group is cooperatively coordinated by
three mercury centers of another molecule 1 through the nitrogen atom. The reaction
of compound 1 with triethylamineborane Et3NBH3 in THF affords the 1 : 1 complex
{[(oꢀC6F4Hg)3][Et3NBH3]} (7). In this adduct, the binding of the aminoborane to the mercury
anticrown is also accomplished by B—H—Hg bridges. The stability constants of complexes 5
and 6 in THF were determined.
Key words: anticrowns, macrocyclic multidentate Lewis acids, polymercuramacrocycles,
anionic boron hydrides, aminoboranes, complexes, IR spectroscopy, Xꢀray diffraction study.
Anticrowns are chargeꢀreversed analogs of crown ethers
A large number of complexes of this anticrown with variꢀ
ous anions and neutral oxygen, nitrogen, sulfur, and carꢀ
bon Lewis bases were synthesized and structurally characꢀ
terized. There is also evidence that compound 1 shows
promise in organic synthesis and catalysis,1,2,11,12 for the
molecular recognition,13 as a ionophore for ionꢀselective
electrodes,14 and for the design of new luminescent maꢀ
terials.5
and related macrocycles. They contain several Lewis acidic
atoms in the macrocyclic chain and so can efficiently bind
various anions and neutral Lewis bases to form unusual
complexes, in which a Lewis base molecule is cooperatively
coordinated by all Lewisꢀacid centers of the macrocycle
(see reviews,1—6 recent articles,7,8 and references
therein). ff
Among the presently known anticrowns, cyclic trimeric
perfluoroꢀoꢀphenylenemercury (oꢀC6F4Hg)3 (1) conꢀ
taining three mercury atoms in the planar nineꢀmembered
ring is one of the most studied members of the family.9,10
Earlier,15 we have studied the reaction of macrocycle 1
with the borohydride anion in THF by IR and NMR
spectroscopy and have shown that this reaction afꢀ
fords the complexes {[(oꢀC6F4Hg)3][BH4]}– (2),
{[(oꢀC6F4Hg)3][BH4]2}2– (3), and {[(oꢀC6F4Hg)3]2[BH4]}–
(4), in which the anionic species is bound to the mercury
centers of the anticrown by B—H—Hg bridges. According
to quantum chemical calculations,15 compounds 2, 3, and
4 should have pyramidal (halfꢀsandwich), bipyramidal, and
sandwich structures, respectively (Fig. 1). However, none
of these complexes were isolated from the mixture in the
individual state. Hence, their precise structures remain unꢀ
known.
In the present work, we investigated the interaction of
macrocycle 1 with the cyanoborohydride anion [H3BCN]–
and triethylamineborane Et3NBH3 bearing a negative
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2489—2496, December, 2008.
1066ꢀ5285/08/5712ꢀ2540 © 2008 Springer Science+Business Media, Inc.

Anticrowns
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 12, December, 2008
2541
spectrum of a solution of [H3BCN]– in THF shows three
ν(BH) bands at 2304 (A1), 2284 (E), and 2208 (E) cm–1
The stretching band ν(CN) of the cyanide group is obꢀ
served at 2155 cm–1
2–
.
.
The gradual addition of macrocycle 1 to an excess of
[PPN][H3BCN] (PPN = (Ph3P)2N+) in THF at 20 °C
([H3BCN]0 = 0.01 mol L–1) is accompanied by a deꢀ
–
crease in the intensity of the ν(BH) and ν(CN) bands of
the free [H3BCN]– ion in the IR spectrum and by the
appearance of new absorption bands at 2323 and 2137 cm1
indicative of the complexation of [H3BCN]– with the merꢀ
cury atoms of the macrocycle. When the 1 : [H3BCN]–
molar ratio reaches (1—2) : 1, the bands of the uncoordiꢀ
nated [H3BCN]– anion almost completely disappear, and
the spectrum of a solution shows, in the 2000—2500 cm–1
region, only the aboveꢀmentioned bands ν(BH) and ν(CN)
at 2323 and 2137 cm–1, respectively (Fig. 2), which proved
to belong to complex 5.
2
3
H
B
Hg
The band at 2137 cm–1, which is shifted to lower freꢀ
quencies by 18 cm–1 with respect to the ν(CN) band of the
free [H3BCN]– ion, can be assigned to stretching vibraꢀ
tions of the C≡N bond coordinated to the mercury centers
of the anticrown. The band at 2323 cm–1, which is shifted
to higher frequencies with respect to the ν(BH) bands of
the starting anion, is apparently assigned to B—H groups,
which are not bound to the anticrown. Since lowꢀfrequenꢀ
cy shifts of the ν(BH) bands are not observed in the IR
spectrum, it can be concluded that only the cyanide group
of the [H3BCN]– ion is involved in the coordination to the
macrocycle in complex 5.
The 199Hg NMR spectrum of an equimolar mixture of
compound 1 and [H3BCN]– in acetoneꢀd6 at 20 °C
([1]0 = 0.02 mol L–1) shows a poorly resolved multiplet
shifted downfield by 45 ppm with respect to the signal of
the free macrocycle. However, the 1H and 11B NMR specꢀ
4
Fig. 1. Structures of complexes 2—4 based on calculations by the
AM1 method.15
charge on the borohydride group and a positive
charge on the triethylamino group. The reaction of comꢀ
pound 1 with the [H3BCN]– ion in THF gives the
complexes {[(oꢀC6F4Hg)3][H3BCN]}– (5) and
{[(oꢀC6F4Hg)3]2[H3BCN]}– (6), which were detected in
solution by IR spectroscopy. Complex 6 was isolated in
the analytically pure state, and its structure was estabꢀ
lished by Xꢀray diffraction. Unlike [H3BCN]–, triethylꢀ
amineborane reacts with macrocycle 1 to form the only
complex {[(oꢀC6F4Hg)3][Et3NBH3]} (7). The structure of
7 was also established by Xꢀray diffraction.
A
Results and Discussion
0.20
ν(BH)
ν(CN)
The [H3BCN]– ion contains two types of functional
groups (the cyanide group and hydride hydrogen atoms),
which could be bound to the mercury centers of the antiꢀ
crown. Hence, it was of interest to study the behavior of
this bifunctional anion in the reaction with macrocycle 1.
To answer this question, we investigated the interaction of
[H3BCN]– with compound 1 in THF by IR spectroscopy
at different 1 : [H3BCN]– ratios.
The IR spectrum of the [H3BCN]– anion in the ν(BH)
frequency region is rather complex. In accordance with
symmetry, the [H3BCN]– ion is characterized by three
BH stretching vibrations, viz., the vibration A1 and the
doubly degenerate vibration E.16 All three vibrations are
active in the IR spectra. The doubly degenerate vibration E
should be observed as one band; however, the solvation
effect removes the degeneration and, consequently, the IR
0.15
ν(CN)
0.10
ν(BH)
1
3
0.05
2
2400
2300
2200
ν/cm–1
Fig. 2. The ν(BH) and ν(CN) frequency region of the IR spectra
of the [PРN][H3BCN] compound (0.01 mol L–1) (1) and comꢀ
plexes 5 (1 : [H3BCN]– = 2 : 1) (2) and 6 (1 : [H3BCN]– = 6 : 1)
(3) in THF.

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Tsupreva et al.
Hg(3A)
tra of this mixture virtually do not differ from the correꢀ
sponding spectra of the free [H3BCN]– anion, which is
consistent with the conclusion that the BH3 group of
the cyanoborohydride anion is not involved in the formaꢀ
tion of complex 5. Therefore, the cyanide group of the
[H3BCN]– anion acts in this reaction as a stronger base
than the BH3 group. This result correlates with the earliꢀ
er data17 on the reaction of the [H3BCN]– ion with Brønꢀ
sted acids.
Hg(2A)
Hg(1A)
H
H
B(1)
H
C(19)
C(14)
N(1)
C(1)
The stoichiometry of the formation of complex 5 was
determined by the methods of molar ratios and isomoꢀ
lar series.18 It was found that complex 5 contains one
[H3BCN]– ion per macrocyclic molecule, i.e., its comꢀ
position can be expressed by the formula
{[(oꢀC6F4Hg)3][H3BCN]}–. The stability constant (K1) of
complex 5 in THF at 20 °C evaluated from the IR spectroꢀ
scopic data is rather high (1.2•103 L mol–1). Nevertheless,
attempts to isolate this complex from solution in the indiꢀ
vidual state failed.
Hg(1)
C(7)
C(2)
Hg(2)
C(13)
Hg(3)
C(8)
Fig. 3. Molecular structure of complex 6 in the crystal. All nonꢀ
hydrogen atoms are represented by thermal ellipsoids drawn at
the 30% probability level. For the coordinated [H3BCN]– ion,
only one of two orientations is shown.
The addition of additional amounts of the anticrown to
a solution containing complex 5 leads to further changes
in the spectral pattern, viz., the intensities of the ν(BH)
and ν(CN) bands of compound 5 decrease, and new ν(BH)
and ν(CN) bands at 2231 and 2150 cm–1, respectively,
belonging to complex 6 appear. With increasing concenꢀ
tration of the anticrown, the content of complex 6 in the
mixture increases, and the conversion of compound 5 into
complex 6 is 35% at the ratio 1 : [H3BCN]– = 6 : 1
(see Fig. 2).
anion. The structure of compound 6 was established by
Xꢀray diffraction and is shown in Fig. 3. Selected bond
lengths and bond angles are given in Table 1.
In the crystal, complex 6 occupies a special position on
an inversion center (0 1/2 1/2), resulting in the disorder of
the [H3BCN]– anion over two sites. The refinement of the
structure in the noncentrosymmetric space group P1 also
results in the disorder of the anion. As can be seen from
Fig. 3, complex 6 is a doubleꢀdecker sandwich. In this
sandwich, the [H3BCN]– ion is located between two muꢀ
tually parallel planes of two macrocycles and is coordinatꢀ
ed to the macrocycles by the cyanide and borohydride
groups. The binding of the cyanide group to the anticrown
is accomplished through the nitrogen atom, which interꢀ
acts with all three mercury centers to form a pyramidal
fragment. The Hg—N distances in complex 6 are close to
Unlike the spectrum of complex 5, the IR spectrum of
complex 6 shows the ν(BH) band at lower frequencies
compared to the ν(BH) bands of the free [H3BCN]– anꢀ
ion, which indicates that the BH3 group is involved in the
coordination to the anticrown in this adduct. Since this
coordination should lead to a decrease in the electron denꢀ
sity on the cyanide group, the ν(CN) band in the spectrum
of complex 6 is shifted to higher frequencies (by 13 cm–1
)
with respect to the corresponding band in the IR spectrum
of compound 5.
Table 1. Selected bond lengths (d) and bond angles (ω) in
complex 6
The stoichiometry of the formation of complex 6 was
also determined by the methods of molar ratios and isoꢀ
molar series. According to these methods, complex 6 has
the composition {[(oꢀC6F4Hg)3]2[H3BCN]}–, i.e., it conꢀ
tains one [H3BCN]– ion per two anticrown molecules.
The stability constant (K2) of compound 6 in THF at 20 °C
is 1.9•104 L2 mol–2, which is almost three orders of
magnitude smaller than the corresponding constant
(107 L2 mol–2) found for borohydride complex 4 of similar
composition (see above).15
Parameter
Bond
Value
Parameter
Bond
Value
d/Å
d/Å
Hg(1)—N(1)
Hg(2)—N(1)
Hg(3)—N(1)
Hg(1A)—B(1)*
Hg(2A)—B(1)*
Hg(3A)—B(1)*
Hg(1)—C(1)
2.713(15) Hg(1)—C(14)
2.758(16) Hg(2)—C(2)
2.780(14) Hg(2)—C(7)
3.24(4)
3.41(4)
3.24(4)
2.079(7)
2.084(7)
2.078(8)
2.070(7)
2.068(7)
1.12(4)
Hg(3)—C(8)
Hg(3)—C(13)
C(19)—N(1)
2.073(7) B(1)—C(19)
1.55(4)
Complex 6 was isolated in the crystalline state in 55%
yield by evaporating an acetone solution of a mixture of
[PPN][H3BCN] and macrocycle 1 followed by the treatꢀ
ment of the resulting oily residue with methanol. The eleꢀ
mental analysis showed that the adduct actually contains
two molecules of the mercury anticrown per [H3BCN]–
Angle
ω/deg Angle
ω/deg
C(1)—Hg(1)—C(14)177.6(3) C(8)—Hg(3)—C(13) 175.3(3)
C(2)—Hg(2)—C(7) 175.8(3) B(1)—C(19)—N(1) 178(2)
* The equivalent atoms are generated by the symmetry operation
–x, –y + 1, –z + 1.

Anticrowns
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 12, December, 2008
2543
each other (2.713(15), 2.758(16), and 2.780(14) Å; the
average value is 2.75 Å) and are substantially smaller than the
sum of the van der Waals radii of mercury (1.73—2.00 Å,19,20
2.1 Å21) and nitrogen (1.6 Å21) atoms. Essentially longer
Hg—N distances (2.87—2.96 Å) have been found earlier in
pyramidal complexes of macrocycle 1 with organic nitriles
(acrylonitrile and nꢀbutyronitrile).22,23 This result can be
attributed to a lower electron density on the cyanide group
in electroneutral organic nitriles compared to that in the
[H3BCN]– anion. The same factor is responsible for
a substantial elongation of the Hg—N bonds in the sandꢀ
wich complex of macrocycle 1 with the doubly charged
nitroprusside anion compared to the corresponding disꢀ
tances in the sandwich complex of this macrocycle with
the triply charged hexacyanoferrate anion.24
Hg...Hg, 3.806(1) Å; Hg...F, 3.52(1)—3.55(1) Å;
B(H)...F, 3.13(3)—3.20(3) Å.
The IR spectrum of complex 6 in Nujol mull shows the
ν(BH) band at 2225 cm–1, which is close to the ν(BH)
band observed for a solution of this adduct in THF
(at 2231 cm–1). At the same time, the ν(CN) band in the
IR spectrum of solid complex 6 (observed at 2182 cm–1) is
shifted to higher frequencies by 32 cm–1 with respect to the
analogous band (at 2150 cm–1) in the spectrum of a soluꢀ
tion of 6. This fact may be indicative of definite differencꢀ
es in the coordination mode of the cyanide group of
the [H3BCN]– ion to the mercury centers of the anticrown
in THF and in the solid state. The dissolution of comꢀ
pound 6 in THF is accompanied by its partial dissociation
to form an equilibrium mixture of complexes 5 and 6 and
free macrocycle 1. The constant (K3) of the equilibrium
Unfortunately, we failed to locate the hydrogen atoms
of the borohydride group because of disorder of the
[H3BCN]– anion in complex 6. However, the Hg—B disꢀ
tances in this adduct (3.24(4), 3.24(4), and 3.41(4) Å) are
substantially smaller than the sum of the van der Waals
radii of the mercury (see above) and boron (1.75 Å21) atꢀ
oms, which unambiguously indicates that the BH3 group
of the [H3BCN]– ion is bound to the mercury centers of
the anticrown by B—H—Hg bridges. Similar Hg—B disꢀ
tances (3.317—3.550 Å; the average value is 3.36 Å) were
found25,26 in the structures of complexes of macrocycle 1
5 + 1
6 at 20 °C is 16 L mol–1. Analogous equiꢀ
libria for the doubleꢀdecker sandwich complexes
{[(oꢀC6F4Hg)3]2[B10H10]}2–, {[(oꢀC6F4Hg)3]2[B12H12]}2–,
and {[(oꢀC6F4Hg)3]2[B12H11SCN]}2– synthesized earliꢀ
er25,26 are characterized by the comparable constants (26,
14, and 62 L mol–1, respectively).
To obtain additional data on the structures of comꢀ
plexes 5 and 6, we performed quantum chemical studies of
the interaction of the [H3BCN]– ion with cyclic trimeric
difluorovinylenemercury (C2F2Hg)3 (8) as the simplest
analog of macrocycle 1. The calculations were carried out
by the ab initio B3LYP method28,29 with the use of the
pseudopotential LANL2DZ for Hg atoms combined with
the LANL2DZ basis set28,29 for valence electrons, the
6ꢀ31G basis set for the other atoms of the macrocycle, and
the 6ꢀ311++G(d,p) basis set for the [H3BCN]– anion.
The calculations showed that there are two local minima
on the potential energy surface for the 1 : 1 adduct, and
these minima correspond to complexes 9 and 10 (Fig. 4),
which differ in the coordination mode of the [H3BCN]–
ion to compound 8. In pyramidal complex 9, as in comꢀ
plex 5, the nitrogen atom of the cyanide group is involved
in the coordination to the macrocycle (Hg—N, 2.760,
2.760, and 2.761 Å), whereas the hydride hydrogen atoms
of the BH3 group are bound to the mercury centers of the
macrocycle in adduct 10 (Hg—H, 2.459, 2.468, and
2.478 Å). It should be emphasized that adduct 9 is energetꢀ
ically more favorable (by 11.47 kcal mol–1) than adduct 10
(Table 2). Apparently complex 5,
with the polyhedral closo anions [B10H10]2–, [B12H12]2–
,
and [B12H11SCN]2–. In these complexes, the hydroꢀ
gen atoms of the anionic boranes were located, and it was
shown that they form B—H—Hg bridges with the mercury
anticrown.
Interestingly, a quite different coordination mode of
the anionic species is observed in the multidecker sandꢀ
wich complex of macrocycle 1 with the linear thiocyanate
anion27 in spite of the similar sizes of the [SCN]– and
[BH3CN]– anions. In this adduct, the thiocyanate anion is
bound to the mercury centers of the nearest anticrown
molecules through the sulfur atom, whereas the cyanide
group is not involved in the coordination.
The B(1)—C(19)—N(1) bond angle in the coordinatꢀ
ed [H3BCN]– ion of molecule 6 is close to 180°. The
B(1)—C(19)—N(1) group essentially deviates from the
perpendicular to the mean planes of the central nineꢀmemꢀ
bered mercuracycles (for the B(1)...N(1) vector, this deviꢀ
ation is 18.5°). The mutual arrangement of the macrocyꢀ
cles in compound 6 corresponds to a staggered conformaꢀ
tion. The projections of the centroids of the macrocycles
onto the plane parallel to these rings are shifted with reꢀ
spect to each other by 0.67 Å.
like molecule 9, has also a pyramidal
structure. For the 2 : 1 adduct of comꢀ
pound 8 with [H3BCN]–, the local
minimum on the potential energy surꢀ
The crystal structure of complex 6 consists of alternatꢀ
ing anionic and cationic layers lying parallel to the crystalꢀ
lographic plane (1 1 0). There are no specific interacꢀ
tions between the layers. In the anionic layer, there
are a number of shortened (compared to the correspondꢀ
ing van der Waals distances) intermolecular contacts:
face corresponds to sandwich complex
11 (see Fig. 4) structurally similar to
complex 6. In molecule 11, the nitroꢀ
gen atom of the cyanide group of the [H3BCN]– ion forms
a pyramidal fragment with the mercury centers (Hg—N,
2.836, 2.837, and 2.838 Å), and the binding of the BH3

2544
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Tsupreva et al.
H
Table 2. Thermodynamic characteristics of complexes 9—11
evaluated by quantum chemical calculations
H
H
B
Complex
–ΔE*
–ΔG°
–ΔS°
298
298
/kcal mol–1 deg–1
kcal mol–1
C
N
9
10
11
47.56
36.09
68.42
37.16
27.18
49.57
35.03
28.21
58.88
F
F
Hg
C
Hg
C
C
C
C
C
* The energy of formation of the complexes from the startꢀ
ing reagents with the ZPE (zeroꢀpoint energy) correction.
F
F
Hg
F
F
constant of complex 6 in THF compared to that estimated
for complex 5.
9
We succeeded in preparing complex 7 in the crystalline
state in 70% yield by evaporating a THF solution of an
equimolar mixture of macrocycle 1 and Et3NBH3. The
elemental analysis showed that this complex has the comꢀ
position {[(oꢀC6F4Hg)3][Et3NBH3]}, i.e., it contains one
aminoborane molecule per molecule of the macrocycle.
The IR spectrum of compound 7 in Nujol mulls shows
ν(BH) bands at 2374 and 2216 cm–1, which are shifted to
lower frequencies by 12 and 65 cm–1, respectively, with
respect to the ν(BH) bands in the IR spectrum of free
Et3NBH3, thus indicating that all three hydrogen atoms of
the BH3 group are involved in the coordination to the
anticrown. However, the dissolution of complex 7 in THF
leads to its complete dissociation, and so it was impossible
to study the complexation of macrocycle 1 with Et3NBH3
in this solvent by IR spectroscopy. In the 199Hg NMR
spectrum recorded in the presence of a tenfold excess of
Et3NBH3 with respect to the anticrown, the downfield
shift of the mercury resonance in THF is no larger than
4 ppm, i.e., the amount of complex 7 in solution is negligiꢀ
ble even under such conditions. Hence, it can be concludꢀ
ed that the formation of compound 7 from macrocycle 1
and Et3NBH3 in THF occurs in the step of crystal precipiꢀ
tation during the removal of the solvent.
N
C
B
H
H
H
C
F
F
Hg
C
Hg
C
C
C
C
F
F
Hg
F
F
10
F
Hg
C
F
F
F
C
C
C
Hg
Hg
N
C
C
F
H
H
H
B
C
The Xꢀray diffraction study of complex 7 showed that
in this adduct, only the negatively charged BH3 group of
the aminoborane is coordinated to the mercury centers of
the anticrown and, in agreement with the IR spectroscopic
data, all three hydrogen atoms interact with the mercury
atoms of the macrocycle to form two types of B—H—Hg
bridges (Fig. 5). In one type of the bridges, the BH group
of aminoborane is cooperatively coordinated by all three
mercury atoms of the anticrown to form a pyramidal strucꢀ
ture. The B(1)—H(3) group of the Et3NBH3 molecule
is involved in this type of binding. The Hg(1)—H(3),
Hg(2)—H(3), and Hg(3)—H(3) distances in complex 7
are 2.76(5), 2.96(5), and 2.70(5) Å, respectively (Table 3).
All these distances are essentially smaller than the sum of
the van der Waals radii of the mercury (see above) and
hydrogen (1.2 Å21) atoms. Another type of B—H—Hg
bridges is formed by the B(1)—H(1) and B(1)—H(2)
N
C
F
F
C
Hg
Hg
C
C
F
F
F
C
F
C
Hg
11
Fig. 4. Structures of model complexes 9—11 according to quanꢀ
tum chemical calculations.
group to the macrocycle is accomplished through B—H—Hg
bridges (Hg—H, 2.587, 2.595, and 2.620 Å). It is supposed
that such bridges are present also in molecule 6. Complex
11 is energetically much more favorable than adduct 9
(see Table 2), which is consistent with the larger stability

Anticrowns
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 12, December, 2008
2545
C(20)
C(19)
wich borohydride complex 4 (see Fig. 1). This can be conꢀ
sidered as a support of the validity of the proposed strucꢀ
ture for 4.
C(23)
The B(1)—N(1) bond vector in molecule 7 deviates
from the perpendicular to the mean plane of the nineꢀ
membered mercuracycle by 33.1°, which is substantially
larger than the analogous deviation of the B(1)...N(1) vecꢀ
tor in complex 6. The B(1)—N(1) bond length of the coorꢀ
dinated triethylamineborane in compound 7 (1.607(7) Å)
is virtually equal to the B—N distance (1.616 Å)30 in free
trimethylamineborane Me3NBH3.
C(24)
C(21)
C(22)
N(1)
H(1)
H(2)
H(3)
B(1)
C(1)
C(14)
C(8)
Hg(1)
C(7)
C(13)
Hg(3)
C(2)
Hg(2)
In the crystal structure of complex 7, the free planes of
the macrocycles in pairs of molecules 7 are closely spaced
to form centrosymmetric dimers characterized by shortꢀ
ened intermolecular Hg...Hg (3.759(1) and 3.901(1) Å)
and Hg...C (3.293(6)—3.511(6) Å) contacts. In each
dimer, the mutually parallel planes of the central Hg3C6
rings of the macrocycles are at a distance of 3.36 Å from
each other. The projections of the centroids of the Hg3C6
rings onto the plane parallel to these rings are shifted with
respect to each other by 1.25 Å. The macrocyclic fragꢀ
ments in the dimer have a staggered conformation. Analoꢀ
gous centrosymmetric dimers have been observed earlier in
the crystal structures of the 1 : 1 complexes of macrocycle
1 with nꢀbutyronitrile,23 acetone,31 nitrobenzene,8 and
1,3,5ꢀtrithiane.7
Fig. 5. Molecular structure of complex 7 in the crystal. The
hydrogen atoms of the ethyl groups are omitted. All nonhydroꢀ
gen atoms are represented by thermal ellipsoids drawn at the 30%
probability level.
groups, each of which interacts with one mercury center of
the macrocycle (Hg(1)—H(1), 3.01(5) Å; Hg(2)—H(2),
2.61(5) Å). The H(1)B(1)H(2) plane in molecule 7 is virꢀ
tually parallel to the mean plane of the central nineꢀmemꢀ
bered ring of the anticrown (the dihedral angle is 11°), and the
N(1)B(1)H(3) plane is almost perpendicular to this mean
plane (the dihedral angle is 80°). The B(1)—H(3)—Hg(3)
group is nearly linear (the B(1)—H(3)—Hg(3) bond angle
is 165(4)°). The other B—H—Hg angles are in the range of
95(3)—113(3)° (see Table 3). The boron atom in complex
7 is shifted from the threefold axis of the macrocycle, reꢀ
sulting in the difference in the Hg—B distances. Two of
these distances (Hg(1)—B(1), 3.331(6) Å; Hg(2)—B(1),
3.261(6) Å) are comparable with the corresponding
distances in complex 6, whereas the third distance
(Hg(3)—B(1), 3.805(6) Å) is substantially larger and apꢀ
proximates the upper limit of the van der Waals Hg...B
distances (2.1 + 1.75 = 3.85 Å). According to quantum
chemical calculations,15 exactly the same geometry of
the coordination of the BH3 group to the macrocycle
should be observed in the halfꢀsandwich fragment of sandꢀ
The Hg—C bond lengths in complexes 6 and 7 are
unexceptional (2.068(7)—2.084(7) Å). The C—Hg—C
bond angles are in the range of 174.1(2)—177.6(3)°, which
indicates that the mercury atoms of the macrocycle retain
the sp hybridization in molecules 6 and 7.
Experimental
Macrocycle 1 was synthesized according to a procedure deꢀ
scribed earlier.9 The starting compound [PPN][H3BCN] was
synthesized by the metathesis reaction of [PPN]Cl (Aldrich) in
an aqueous ethanolic solution with an aqueous solution of
Na[H3BCN] (Merck). The solvents were purified from moisture
and other impurities according to standard methods and were
Table 3. Selected bond lengths (d) and bond angles (ω) in complex 7
Bond
d/Å
Bond
d/Å
Angle
ω/deg
Angle
ω/deg
Hg(1)—H(3)
Hg(2)—H(3)
Hg(3)—H(3)
Hg(1)—H(1)
Hg(2)—H(2)
Hg(1)—B(1)
Hg(2)—B(1)
Hg(3)—B(1)
B(1)—H(1)
B(1)—H(2)
B(1)—H(3)
2.76(5)
2.96(5)
2.70(5)
3.01(5)
2.61(5)
3.331(6) Hg(1)—C(14)
3.261(6) Hg(2)—C(2)
3.805(6) Hg(2)—C(7)
B(1)—N(1)
C(21)—N(1)
C(19)—N(1)
C(23)—N(1)
Hg(1)—C(1)
1.607(7)
1.504(6)
1.505(6)
1.510(6)
2.072(5)
2.074(5)
2.074(6)
2.076(6)
2.077(5)
2.074(5)
Hg(1)—H(1)—B(1)
Hg(2)—H(2)—B(1)
Hg(1)—H(3)—B(1)
Hg(2)—H(3)—B(1)
Hg(3)—H(3)—B(1)
C(1)—Hg(1)—C(14) 174.1(2) C(19)—N(1)—C(23) 107.6(4)
C(2)—Hg(2)—C(7) 176.4(2) C(21)—N(1)—C(23) 109.3(4)
C(8)—Hg(3)—C(13) 175.9(2) C(19)—N(1)—B(1) 106.2(4)
96(3) N(1)—B(1)—H(3)
113(3) H(1)—B(1)—H(2)
109(3) H(1)—B(1)—H(3)
95(3) H(2)—B(1)—H(3)
107(3)
109(4)
113(4)
108(4)
165(4) C(19)—N(1)—C(21) 111.1(4)
1.17(5)
1.20(5)
1.14(5)
Hg(3)—C(8)
Hg(3)—C(13)
N(1)—B(1)—H(1)
N(1)—B(1)—H(2)
112(3) C(21)—N(1)—B(1) 112.2(4)
108(3) C(23)—N(1)—B(1) 110.3(4)

2546
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 12, December, 2008
Tsupreva et al.
distilled under argon before use. Triethylamineborane was purꢀ
chased from Merck. The IR spectra were measured on a Specord
Mꢀ82 spectrometer and an INFRALUM FTꢀ801 FTIR specꢀ
trometer. The spectroscopic studies were carried out in CaF2
cells (d = 0.04—0.12 cm) in the BH and CN stretching region
Complex [PPN]{[(oꢀC6F4Hg)3]2[H3BCN]} (6). Compound
1 (0.07 g, 0.067 mmol) was added to a solution of [PPN][H3BCN]
(0.04 g, 0.069 mmol) in acetone (2.5 mL). The solvent was disꢀ
tilled off under a stream of argon, and methanol (~1 mL) was
added to the oily residue. The white crystals of complex 6 that
formed were separated by decantation and dried at room temperꢀ
ature under a stream of argon. The yield was 0.06 g (55%). Found
(%): C, 33.11; H, 1.47; F, 17.45; P, 2.36. C73H33BF24Hg6N2P2.
Calculated (%): C, 32.82; H, 1.24; F, 17.08; P, 2.32.
(2100—2400 cm–1) at different concentrations (10–2—10–3 mol L–1
)
and different [H3BCN]– : 1 ratios (10 : 1—1 : 10). The IR
spectra of solid samples were recorded as Nujol mulls in the
1
1200—4000 cm–1 region. The 199Hg, 11B, and H NMR spectra
were measured on a Bruker Avanceꢀ600 spectrometer with the
use of HgMe2, BF3•Et2O, and Me4Si, respectively, as the exterꢀ
nal standards.
Complex {[(oꢀC6F4Hg)3][Et3NBH3]} (7). Triethylamineboꢀ
rane Et3NBH3 (0.052 mL, 0.038 mmol) was added to a solution
of compound 1 (0.04 g, 0.038 mmol) in THF (2.5 mL). The
reaction mixture was concentrated at room temperature, after
which white crystals of complex 7 precipitated. The yield was
0.03 g (70%). Found (%): C, 24.83; H, 1.56; B, 0.93; F, 19.64;
Hg, 51.8; N, 1.21. C24H18BF12Hg3N. Calculated (%): C, 24.78;
H, 1.55; B, 0.95; F, 19.62; Hg, 51.9; N, 1.21.
The compositions of the complexes in solution were deterꢀ
mined from the IR spectroscopic data by the methods of molar
ratios and isomolar series.18 In the studies by the method of
molar ratios, the absorbances of the ν(CN) bands at 2137 cm–1
(complex 5) and 2150 cm–1 (complex 6) were measured for
a series of solutions with the same initial concentration of the
[H3BCN]– ion (2•10–2 mol L–1) and at different concentrations
of macrocycle 1 (10–1—10–2 mol L–1). The composition of the
complex was determined from the inflection point in the plot of
the absorbance versus the concentration ratio [1]0/[H3BCN–]0.
In the studies by the method of isomolar series, the absorbances
of the aboveꢀmentioned bands were measured for a series of
Xꢀray diffraction study of complexes 6 and 7. Crystallographic
data and data collection and structure refinement parameters for
compounds 6 and 7 are given in Table 4. The Xꢀray diffraction data
sets were collected on a Bruker SMART 1000 CCD diffractomeꢀ
ter32 equipped with an area detector (graphite monochromator,
λ(MoꢀKα) = 0.71073 Å, ωꢀscanning technique, T = 120 K). The
semiempirical absorption correction was applied with the use of
the SADABS program.33 The structures were solved by direct
methods and refined by the fullꢀmatrix leastꢀsquares method
solutions at different concentrations (1.5•10–2—3•10–3 mol L–1
)
of macrocycle 1 and the [H3BCN]– ions but with the same total
concentration (3•10–2 mol L–1). In this case, the composition of
the complex was determined from the position of the maxiꢀ
mum in the plot of the absorbance versus the concentration ratio
[1]0/([1]0 + [H3BCN–]0). The results obtained by both methods
are in agreement with each other.
based on F2 with anisotropic thermal parameters for all nonꢀ
hkl
hydrogen atoms. All hydrogen atoms in the structure of complex
Table 4. Crystallographic data, data collection, and structure reꢀ
finement parameters for compounds 6 and 7
The stability constants of complexes 5 and 6 for the equilibria
(оꢀС6F4Hg)3 + [H3BCN]–
{[(оꢀС6F4Hg)3][H3BCN]}–,
Parameter
6
7
Molecular formula
Molecular weight
Crystal system
Space group
a/Å
b/Å
c/Å
α/deg
β/deg
C73H33BF24Hg6N2P2 C24H18BF12Hg3N
2670.30
1160.97
Triclinic
P–1
Triclinic
2 (оꢀС6F4Hg)3 + [H3BCN]–
{[(оꢀС6F4Hg)3]2[H3BCN]}–,
–
P1
9.098(2)
11.000(2)
18.136(3)
103.719(4)
101.805(4)
91.121(4)
1721.6(5)
1
10.957(1)
11.404(1)
11.751(1)
105.341(2)
94.409(2)
103.960(2)
1358.5(2)
2
{[(оꢀС6F4Hg)3][H3BCN]}– + (оꢀС6F4Hg)3
{[(оꢀС6F4Hg)3]2[H3BCN]}–
γ/deg
3
were calculated according to the following equations:
V/Å
Z
K1 = [CCN – ACN/(εCNd)]/{[ACN/(εCNd)][CHg
– (CCN – ACN/(εCNd))]},
–
dcalc/g cm–3
2θmax/deg
μ/cm–1
2.576
58
134.85
2.838
58
170.08
Tmin/Tmax
Number of indepenꢀ
0.059/0.294
9105 (0.0404)
0.281/0.483
7132 (0.0274)
K2 = K1K3,
dent reflections (Rint
R1 (based on F
for reflections
with I > 2σ(I))
wR2 (based on F2
for all reflections)
Number of
)
K3 = [CCN – ACN/(εCNd) – A5/(ε d)]/{[A5/(ε d)][CHg
–
5
5
0.0392 (6486)
0.0284 (5770)
– (CCN – ACN/(εCNd) – A5/(ε d))]}.
5
Here CCN and CHg are the initial concentrations of the [H3BCN]–
ion and macrocycle 1, respectively, ACN is the absorbance of the
ν(BH) band at 2304 cm–1 of the free [H3BCN]– ions, A5 is the
0.0880
502
0.0656
382
absorbance of the ν(BH) band at 2323 cm–1 of complex 5, ε
CN
refined parameters
GOF
and ε are the extinction coefficients of the ν(BH) bands at 2304
5
0.968
1.074
and 2323 cm–1, respectively, and d is the cell thickness.

Anticrowns
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 12, December, 2008
2547
6 were positioned geometrically and refined using a riding modꢀ
el. The hydrogen atoms of the BH3 group in complex 7 were
located in difference Fourier maps and refined isotropically. The
other hydrogen atoms in the structure of complex 7 were posiꢀ
tioned geometrically and refined using a riding model. All calcuꢀ
lations were carried out on a PC using the SHELXTL program
package.34 The complete tables of the atomic coordinates, bond
lengths, bond angles, and anisotropic thermal parameters were
deposited with the Cambridge Structural Database.
17. O. A. Filippov, A. M. Filin, N. V. Belkova, V. N. Tsupreva,
Y. V. Shmyrova, I. B. Sivaev, L. M. Epstein, E. S. Shubina,
J. Mol. Struct., 2006, 790, 114.
18. M. I. Bulatov, I. P. Kalinkin, Prakticheskoe rukovodstvo po
fotokolorimetricheskim i spektrofotometricheskim metodam
analiza [Manual on Photocolorimetric and Spectrophotometꢀ
ric Methods of Analysis], Khimiya, Moscow, 1968, p. 178
(in Russian).
19. A. J. Canty, G. B. Deacon, Inorg. Chim. Acta, 1980, 45,
L255.
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos 07ꢀ03ꢀ00739
and 08ꢀ03ꢀ00332), the Council on Grants of the President
of the Russian Federation (Program for State Support of
Leading Scientific Schools of the Russian Federation,
Grant NShꢀ3019.2008.3), and the Russian Science Supꢀ
port Foundation.
20. P. Pyykkö, M. Straka, Phys. Chem. Chem. Phys., 2000,
2, 2489.
21. S. S. Batsanov, Zh. Neorg. Khim., 1991, 36, 3015 [Russ. J.
Inorg. Chem., 1991, 36 (Engl. Transl.)].
22. I. A. Tikhonova, F. M. Dolgushin, A. I. Yanovsky, Z. A.
Starikova, P. V. Petrovskii, G. G. Furin, V. B. Shur, J. Orgaꢀ
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23. I. A. Tikhonova, F. M. Dolgushin, K. I. Tugashov, G. G.
Furin, P. V. Petrovskii, V. B. Shur, Izv. Akad. Nauk,
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Received June 24, 2008;
in revised form December 17, 2008