Tribromogermyl monochelates - Derivatives of N,N-disubstituted 2-hydroxycarboxylic amides

Article abstract of DOI:10.1007/s11172-010-0159-3

Reactions of GeBr₄ with N,N-dimethyl-2- trimethylsiloxypropionamide (2a), (S)-2-trime-thylsiloxypropionpyrrolidide ((S)-2b), and N,N-dimethyl-O-(trimethylsilyl)mandelamide (2c) afforded pentacoordinated neutral (O,O)-monochelates, viz., N,N-dimethyl-2-tribromoger- myloxypropionamide (3a), (S)-2-tribromogermyloxypropionpyrrolidide ((S)-3b), and N,N-dimethyl-O-(tribromogermyl)mandelamide (3c), respectively. X-ray diffraction study was performed for tribromides 3a, (S)-3b, and 3c, as well as for the N,N-dimethylmandelamide (1c) described earlier. According to the X-ray diffraction data, the Ge atom in tribromides 3a, (S)-3b, and 3c is pentacoordinated and has trigonal bipyramidal configuration with two halogen atoms and oxygen atom of the ether group in the equatorial positions and the halogen atom and the amide oxygen atom in the axial fragment, the bonds in which are somewhat longer as compared to the analogous bonds in tetracoordinated Ge compounds.

Full text of DOI:10.1007/s11172-010-0159-3

Russian Chemical Bulletin, International Edition, Vol. 59, No. 4, pp. 761—770, April, 2010
761
Tribromogermyl monochelates — derivatives of N,Nꢀdisubstituted
2ꢀhydroxycarboxylic amides
A. G. Shipov,a S. V. Grüner,b A. A. Korlyukov,c E. P. Kramarova,a T. P. Murasheva,a S. Yu. Bylikin,a
Vad. V. Negrebetskii,a F. A. Ivashchenko,b D. V. Airapetyan,b G. Ya. Zueva,d M. Yu. Antipin,c and Yu. I. Baukova
aRussian State Medical University,
1 ul. Ostrovityanova, 117997 Moscow, Russian Federation.
Fax: +7 (495) 434 0329. Eꢀmail: baukov@rsmu.ru
bDepartment of Chemistry, M. V. Lomonosov Moscow State University,
Build. 3, 1 Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (495) 939 5546. Eꢀmail: svgrun@org.chem.msu.ru
cA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5085. Eꢀmail: alex@xrlab.ineos.ac.ru
dA. M. Prokhorov Institute of General Physics, Russian Academy of Sciences,
38 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 0270
Reactions of GeBr4 with N,Nꢀdimethylꢀ2ꢀtrimethylsiloxypropionamide (2a), (S)ꢀ2ꢀtrimeꢀ
thylsiloxypropionpyrrolidide ((S)ꢀ2b), and N,NꢀdimethylꢀOꢀ(trimethylsilyl)mandelamide (2c)
afforded pentacoordinated neutral (O,O)ꢀmonochelates, viz., N,Nꢀdimethylꢀ2ꢀtribromogerꢀ
myloxypropionamide (3a), (S)ꢀ2ꢀtribromogermyloxypropionpyrrolidide ((S)ꢀ3b), and N,Nꢀdiꢀ
methylꢀOꢀ(tribromogermyl)mandelamide (3c), respectively. Xꢀray diffraction study was perꢀ
formed for tribromides 3a, (S)ꢀ3b, and 3c, as well as for the N,Nꢀdimethylmandelamide (1c)
described earlier. According to the Xꢀray diffraction data, the Ge atom in tribromides 3a,
(S)ꢀ3b, and 3c is pentacoordinated and has trigonal bipyramidal configuration with two haloꢀ
gen atoms and oxygen atom of the ether group in the equatorial positions and the halogen atom
and the amide oxygen atom in the axial fragment, the bonds in which are somewhat longer as
compared to the analogous bonds in tetracoordinated Ge compounds.
Key words: pentacoordinated germanium compounds, synthesis, Xꢀray diffraction study,
quantum chemical calculations.
Hypercoordinated germanium compound attract atꢀ
tention of researchers by their structural features, reactiviꢀ
ty, stereochemical nonrigidity in solutions,1a,b as well as
biological activity.1c Among them, pentaꢀ and hexacoorꢀ
dinated complexes containing (O,O)ꢀ and (S,S)ꢀdianionꢀ
ic, (C,O)ꢀ, (C,N)ꢀ, and (O,N)ꢀmonoanionic chelate
ligands are studied relatively well.1a In particular, we deꢀ
veloped convenient methods for the preparation of neutral
and cationꢀanionic monoꢀ and bisꢀchelate complexes of
pentaꢀ and hexacoordinated germanium containing biꢀ
dentate amidomethyl or lactamomethyl (C,O)ꢀchelating
ligands2,3 and studied their structure, reactivity, and beꢀ
havior in solutions. At the same time, information on
their structurally characterized (O,O)ꢀchelate analogs is
very scarce (see, for example, Refs 4a—c and references
cited therein).
ing (O,O)ꢀmonoanionic bidentate ligands based on 2ꢀhyꢀ
droxycarboxylic acid amides, (O→Ge)ꢀchelate Oꢀ[(chloꢀ
romethyl)dichlorogermyl]mandelic4a and Oꢀtrichlorogerꢀ
mylꢀ(S)ꢀmandelic acid N,Nꢀdimethylamides.4c In conꢀ
tinuation of this study, the present work is devoted to the
synthesis, Xꢀray diffraction and quantum chemical studꢀ
ies of three representatives of monochelate tribromogerꢀ
myl complexes with monoanionic bidentate (O,O)ꢀchelatꢀ
ing ligands based on 2ꢀhydroxycarboxylic acid N,Nꢀdiꢀ
substituted amides, as well as Xꢀray diffraction analysis
for the ligand described earlier,5 viz., N,Nꢀdimethylꢀ
mandelamide.
Results and Discussion
Synthesis and structure. We have found that the reacꢀ
tion of GeBr4 with Oꢀtrimethylsilyl derivatives of N,Nꢀdiꢀ
substituted 2ꢀhydroxycarboxylic amides leads to pentacoꢀ
Recently, we have described the first representatives of
neutral pentacoordinated germanium complexes containꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 745—754, April, 2010.
1066ꢀ5285/10/5904ꢀ0761 © 2010 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
Shipov et al.
ordinated (O,O)ꢀmonochelate tribromogermyl complexes.
N,Nꢀdimethylꢀ2ꢀhydroxypropionamide (1a), (S)ꢀ2ꢀhydrꢀ
oxypropionpyrrolidide ((S)ꢀ1b), and N,Nꢀdimethylmanꢀ
delamide (1c) were used as the starting compounds, which
were silylated with hexamethyldisilazane in the presence
of a small amount of chlorotrimethylsilane to the correꢀ
sponding Oꢀtrimethylsilyl derivatives 2a, (S)ꢀ2b, and 2c
(Scheme 1). The reactions of the latter with GeBr4 in an
inert solvent, similarly to the analogous reaction involving
going from Oꢀtrimethylsilyl to tribromogermyl derivatives,
that was also noted4c for N,Nꢀdimethylamide Clꢀ3c.
To assign the vibration frequencies more precisely,
we performed calculations of the vibration spectra for
the molecules 3a, (S)ꢀ3b, and 3c by the DFT method
(mpw1pw91/6ꢀ311g(d,p)) in the framework of the Gaussꢀ
ian 03W program.5 Based on the calculations with allowꢀ
ance for the scaling factor6 (0.9567), the frequencies for
asymmetric (1634, 1626, and 1636 cm–1) and symmetric
(1505, 1473, and 1501 cm–1) vibrations for the chelate
NCO fragments were obtained, which were close enough to
those observed in the experiment. In our view, the differꢀ
ences in the vibrational frequencies present can be attributꢀ
ed to the various phase states of the molecules in the
experiment and calculations. Note that in contrast to
(O→M)ꢀchelate (M = Si, Ge) Nꢀsilylmethyl7 and Nꢀgerꢀ
mylmethyl8 amide and lactam derivatives, vibrational
frequencies for the NCO fragment in the tribromides under
study are less characteristic due to the small shift of
the frequency with respect to the frequency of the starting
Oꢀtrimethylsilyl derivatives for asymmetric vibrations
and low frequencies for symmetric vibrations, whose
bands overlap with vibrations for other fragments of the
molecule.
4c
GeCl4 and independent on the ratio of reagents (see
Experimental), leads to the isolation of the 1 : 1 reaction
products, viz., (O→Ge)ꢀchelate of N,Nꢀdisubstituted
2ꢀ(tribromogermyloxy)carboxylic amides 3a, (S)ꢀ3b, and 3c.
The yields of the final products calculated from GeBr4
were 70—80%.
Scheme 1
1
The H NMR spectra correspond to the suggested
structures. The lowꢀfield shift of the signal in the 29Si NMR
spectra of the trimethylsilyl derivatives 2a and (S)ꢀ2b
(δ 16.1 and 15.7 ppm), as well as (S)ꢀ2c (δ 21.3 ppm)4c
indicates the absence of coordination interaction in them.
This is also confirmed by the highꢀfield shift (by 2—3 ppm)
of the signal for the carbonyl group in their 13C NMR
spectra as compared to pentacoordinated tribromogermyl
complexes 3a, (S)ꢀ3b, and 3c. Analogous effect has been
observed earlier2b,9 also for the C,Oꢀchelate complexes
with intramolecular coordination O→M (M = Si, Ge) on
their comparison with nonchelate model compounds.
Xꢀray diffraction study. General views of complexes
3a, (S)ꢀ3b, and 3c, as well as dimethylamide 1c used as
the starting compound, are given in Figs 1—4. Selected
R1 = Me, R2 = R3 = Me (a); R1 = Me, R2R3 = (CH2)4 (b);
R
1 = Ph, R2 = R3 = Me (c)
The structures of compounds (S)ꢀ1b, 2a—c, and 3a—c
obtained in the present work and unknown earlier were
inferred from the elemental analysis (except complex 3a),
IR and NMR spectroscopic data. The structures of comꢀ
plexes 3a, (S)ꢀ3b, 3c, as well as dimethylamide 1c were
confirmed by the Xꢀray diffraction study.
C(4)
C(3)
The IR spectra of Oꢀtrimethylsilyl derivatives 2a,
(S)ꢀ2b, and 2c contain intensive absorption bands in the
region 1700—1400 cm–1, which are attributed to the asymꢀ
metric vibrations of the NCO fragment, νas(NCO), at
1652, 1664, and 1648 cm–1, respectively (which are acꢀ
companied by a band of weak intensity at 1620 cm–1 asꢀ
signed by us to the vibrations of the aromatic system). In
the indicated region, the spectra of chelates 3a, (S)ꢀ3b,
and 3c contain intensive absorption bands νas(NCO) at
1630, 1639, and 1640 cm–1, respectively, as well as addiꢀ
tional bands of medium intensities for the symmetric viꢀ
C(2)
O(2)
N(1)
C(1)
Br(1)
C(5)
Ge(1)
O(1)
Br(2)
Br(3)
brations of this fragment at 1485, 1464, and 1480 cm–1
,
Fig. 1. General view of molecule 3a in representation of atoms
by ellipsoids of thermal vibrations with 50% probability. Hydroꢀ
gen atoms are not shown.
respectively. Note that the band for the asymmetric vibraꢀ
tions insignificantly shifts to the longꢀwave region when

Pentacoordinated germanium complexes
C(3)
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
763
Br(3)
structural parameters for complexes 3a, (S)ꢀ3b, and 3c are
given in Table 1. The bond distances and bond angles in
the structure of 1c agree with the values characteristic of
2ꢀhydroxycarboxylic acid amides.10 In molecules 3a,
(S)ꢀ3b, and 3c, the Ge atoms are pentacoordinated, the
monoanionic ligands based on 2ꢀhydroxycarboxylic acid
amides are bidentate and form the O,Oꢀchelate rings at
the germanium atom. A special feature of complex 3c is
spontaneous separation of the enantiomers (the structure
crystallizes in the P212121 chiral space group), which alꢀ
lowed us to assign the (S)ꢀconfiguration of the asymmetꢀ
ric atom C(2). The absolute (S)ꢀconfiguration of atom
C(2) in complex (S)ꢀ3b is realized due to the use of enanꢀ
tiomer (S)ꢀ1b as the starting compound. It is impossiꢀ
ble to assign absolute configuration for compound 3a
(the space group is Pꢀ1).
Br(1)
O(2)
C(2)
Ge(1)
C(7)
O(1)
C(1)
N(1)
C(6)
C(5)
C(4)
Br(2)
Fig. 2. General view of molecule (S)ꢀ3b in representation of
atoms by ellipsoids of thermal vibrations with 50% probability.
Hydrogen atoms are not shown.
In complexes 3a, (S)ꢀ3b, and 3c, the fiveꢀmembered
chelate ring corresponds to the envelope conformation
with the atom C(2) coming out by 0.25, 0.12, and 0.28 Å,
respectively. The coordination leads to the elongation of
the C(1)—O(1) bond in the structure of 3c by ∼0.02 Å as
compared to the analogous C(3)—O(1) bond in compound
1c (see Fig. 4).
C(9)
C(8)
C(10)
C(7)
C(5)
A coordination polyhedron of the germanium atom is
of the highest interest, it corresponds to a distorted trigoꢀ
nal bipyramid. The Ge atom coming out of the plane of
equatorial atoms Br(2), Br(3), and O(2) in complexes 3a,
(S)ꢀ3b, and 3c toward Br(1) atom changes within narꢀ
row enough range of 0.12—0.15 Å. The bond distance
Ge(1)—O(1) is low sensitive to the change in the nature of
substituents on atoms C(1) and C(2) (see Table 1). Тhis is
true for the axial Ge(1)—Br(1) bond as well. Nevertheless,
in complexes (S)ꢀ3b and 3c the Ge(1)—O(1) bond is shortꢀ
er than in 3a by 0.02 Å. To sum up, the coordination
C(6)
O(2)
C(4)
C(2)
C(1)
N(1)
Br(1)
Ge(1)
O(1)
C(3)
Br(3)
Br(2)
Fig. 3. General view of molecule 3c in representation of atoms
by ellipsoids of thermal vibrations with 50% probability. Hydroꢀ
gen atoms are not shown.
Table 1. The main bond distances (d) and bond angles (ω) in
molecules 3a, (S)ꢀ3b, and 3c in crystals
Parameter
3a
(S)ꢀ3b
d/Å
3c
O(1)
O(2)
Bond distance
C(4)
C(3)
N(1)
Ge(1)—O(1)
Ge(1)—O(2)
Ge(1)—Br(1)
Ge(1)—Br(2)
Ge(1)—Br(3)
C(1)—O(1)
2.036(4)
1.773(4)
2.3956(9)
2.3008(9)
2.3154(9)
1.277(7)
1.311(7)
0.147(2)
2.0134(19)
1.7865(19)
2.3956(4)
2.3192(4)
2.3047(4)
1.280(3)
2.014(2)
1.787(2)
2.3971(5)
2.3016(5)
2.3082(5)
1.271(4)
1.308(4)
0.136(1)
C(6)
C(5)
C(10)
C(7)
C(8)
C(1)
C(1)—N(1)
1.300(4)
0.1213(9)
C(2)
C(9)
Δ
*
Ge
Angle
ω/deg
Fig. 4. Molecular structure of potential ligand 1c in representaꢀ
tion of atoms by ellipsoids of thermal vibrations with 50% probaꢀ
bility. Average values of the main bond distances (Å) are:
O(1)—C(3) 1.254(5), O(2)—C(4) 1.427(4), N(1)—C(3) 1.338(5),
C(3)—C(4) 1.530(5).
O(1)—Ge(1)—Br(1) 171.46(12)
C(1)—O(1)—Ge(1) 111.6(4)
169.28(6)
110.69(18)
174.03(7)
113.0(2)
* The Ge atom coming out of the equatorial plane toward
Br(1) atom.

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Shipov et al.
center of the Ge(1) atom can be described as "rigid", simꢀ
ilarly to that in complex Clꢀ3c studied earlier.4c
tinuum or the system of point charges were used.13—15
Despite satisfactory description of the changes in molecuꢀ
lar geometry depending on the solvent dielectric constant
value, the impossibility to directly study strength of the
intermolecular interactions in solution is an obvious disꢀ
advantage of these methods. Allowance for the solvent
effect is important for the revealing abilities of the comꢀ
plex with the axial Ge—Br bonds to dissociate to the comꢀ
plex cation and Br– anion, which is important for the
understanding the mechanism of further transformations
of compounds under consideration.
To analyze the solvent effect, we used an approach
based on the (PBE0/6ꢀ311G(d,p)) quantum chemical calꢀ
culation of systems including one molecule of a complex
and a number of solvent molecules. Since the strucꢀ
tures of the coordination sites of the Ge(1) atom in 3a,
(S)ꢀ3b, and 3c are close, the quantum chemical calculaꢀ
tions were performed for the most simple complex 3a.
Acetonitrile was chosen as a solvent, since it has no tenꢀ
dency to dissociation, has simple enough structure, and
was used in the synthesis of compounds 3a, (S)ꢀ3b, and
3c. The general views of some calculated associates (solꢀ
vate clusters) are given in Figs 5—7.
The low sensitivity of geometric parameters of the coꢀ
ordination site to the ligand nature distinguishes the
O,Oꢀchelate complexes of trihalogermanes from the
C,Oꢀchelates containing the OGeC3Hal (Hal = F, Cl,
Br) coordination center, in which the interatomic Ge...O
distance changes within a very wide range (for discussion
on these structural regularities, see Refs 4c and 11).
The presence of the strong enough coordination
Ge(1)—O(1) bond leads to a noticeable weakening of the
axial Ge(1)—Br(1) bond as compared to the equatorial
Ge—Br bonds. The differences between distances of the
bonds under consideration are 0.08—0.09 Å, which is larger
than those in complex Clꢀ3c.4c This is not surprising, since
the bond between the Br atom and the 14 group element is
more polarizable than analogous bond with the Cl atom.12
With allowance for the weakening of the axial
Ge(1)—Br(1) bond observed, it can be suggested that in
polar solvents the molecular geometry of (S)ꢀ3b and 3c is
close to the experimental. This, in turn, allows one to conꢀ
sider a possibility of elimination of the axial Br(1) atom
under mild conditions due to the formation of hydrogen
bonds with the solvent. In such a case, elimination of the
Br(1) atom can be one of the steps of the process for the
formation of cyclic germylium cations, the structure and
chemical properties of which will be a subject of our further
studies. For the evaluation of the solvent influence on the
electronic structure and strength of the bonds in the coorꢀ
dination site of the Ge(1) atom, we have performed quanꢀ
tum chemical calculations.
In the isolated molecule 3a, the Ge(1)—O(1) bond is
elongated by 0.2 Å as compared to that in the crystal
(Table 2).
Including two molecules of MeCN into the calculaꢀ
tions is the reason for the significant shortening interꢀ
atomic Ge(1)—O(1) distance and the corresponding inꢀ
crease in the interatomic Ge(1)—Br(1) distance. When
the rest of the MeCN molecules are added, more monotoꢀ
nous change in the interatomic distances above occurs.
Finally, the incorporation of the H2O and HBr molecules
into the solvate cluster, which are able to form strong
H...Br bonds, does not lead to noticeable elongation of the
Ge(1)—Br(1) bond. Dissociation of the axial Ge(1)—Br(1)
bond proved possible on the interaction of the Br(1) atom
with a strong proton donor, for which the cation H3O+
was used. Thus, the calculation shows that in the polar
solvent the presence of only weak C—H...Br and C—H...O
contacts is not enough for the elimination of the axial
Br(1) atom.
Quantum chemical calculations of complex 3a and its
solvate clusters with MeCN. Earlier,4c,11 during the study
of hypercoordinated complexes containing the GeCl3 fragꢀ
ment we have shown that stabilization of their cyclic form
is favored by the intermolecular H...Cl contacts. Similarꢀ
ly, the presence of intermolecular H...Br interactions in
solutions of polar solvents can promote elongation of the
Ge(1)—Br(1) bond. For the quantum chemical simulaꢀ
tion of the interaction of a solvent with compounds of
pentacoordinated silicon, the methods describing solvate
effects as the interaction with uninterrupted dielectric conꢀ
Table 2. The bond distances (d/Å) of the coordination site in the isolated molecule and in the solvate clusters of
3a with MeCN
Compound
Ge(1)—O(1)
Ge(1)—O(2)
Ge(1)—Br(1) Ge(1)—Br(2)
Ge(1)—Br(3)
3a
2.213
2.138
2.075
2.040
2.035
2.018
1.845
1.799
1.800
1.793
1.797
1.795
1.796
1.757
2.344
2.377
2.388
2.411
2.421
2.442
4.573
2.322
2.321
2.339
2.340
2.342
2.332
2.251
2.325
2.326
2.339
2.333
2.329
2.328
2.260
3a•2MeCN
3a•4MeCN
3a•6MeCN
3a•6MeCN•H2O
3a•6MeCN•HBr
3a•6MeCN•H3O+

Pentacoordinated germanium complexes
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
765
To study the electronic structure of the isolated moleꢀ
cule 3a and its solvate clusters, we performed topological
analysis of the calculated function of the electron density
distribution in the framework of the "Atoms in the moleꢀ
cules" theory (AM).16 The critical points (CT) (3, –1) are
localized for all chemical bonds, as well as for weak
intermolecular interactions. The topological parameters
of the bonds formed by the Ge atom are given in Table 3
(the electron density values (ρ(r)), its Laplacian (Χ2ρ(r)),
the local energy density (He(r)), and the potential energy
density (Ve(r)) in the CT (3, –1)).
O(1)
Ge(1)
Br(1)
Similarly to the complexes studied earlier,4c which conꢀ
tain the GeCl3 fragment, the bonds formed by the Ge
atom in molecule 3a and its associates correspond to the
interactions of the intermediate type in the framework of
the AM theory (the values Χ2ρ(r) > 0, whereas the values
He(r) < 0 in the CT (3, –1)). From Table 3, it follows
that for the antibatic change of the Ge(1)—O(1) and
Ge(1)—Br(1) bond distances, the changes of the ρ(r) and
Ve(r) values bear the same character. Quantitative evaluaꢀ
tion of the change in the bond strength in the coordination
environment of the Ge atom was performed based on the
correlational dependence suggested by Espinosa, Molins,
and Lecomte (EML).17 The Ge—O and Ge—Br bond
energies are given in Table 3.
Fig. 5. General view of associate 3a•6MeCN•H2O. Hydrogen
atoms are not shown.*
Ge(1)
Br(1)
O(1)
An increase in the number of MeCN molecules leads
to the strengthening of the axial Ge(1)—O(1) bond by
∼14 kcal mol–1, with the weakening the axial Ge(1)—Br(1)
bond being much less (∼5 kcal mol–1). The Ge(1)—O(1)
bond in the isolated molecule 5a is somewhat stronger
than those in the isolated molecules of the complexes with
the GeCl3 fragment.11 The change in the Ge(1)—O(1)
and Ge(1)—Br(1) bond distances when the number of
MeCN molecules is increased is accompanied by the forꢀ
mation of weak Hꢀbonds C—H...Br, C—H...N, and
C—H...O both between the solvent and complex 3a and
between MeCN molecules.
Br
Fig. 6. General view of associate 3a•6MeCN•HBr. Hydrogen
atoms are not shown.
Molecules of H2O and HBr are bound to MeCN
and complex 3a by the weak O—H...Br and O—H...Br
hydrogen bonds. When a number of solvent molecules inꢀ
creases, not only weak hydrogen bonds are formed, but
interactions of the type "ledge—cavity" emerge as well,
which correspond to the orientational interactions between
lone electron pairs on the N or Br atoms and regions
of local rarefaction of electron density (the central C atom
of the acetonitrile molecule or the N atom of the dimethylꢀ
amino group). Such bonds in the framework of the AM theory
correspond to the interactions of the closed shell type.
The EML correlation scheme was used for the calcuꢀ
lation of energies for all weak interactions between moleꢀ
cules of the solvent and 3a. The overall value of these
interactions (Esolv) regularly increases with the increase of
a number of the solvent molecule, in the limit it can be
described as the solvation energy at 0 K. In the case of
solvate clusters 3a•2MeCN and 3a•4MeCN, the contriꢀ
Br(1)
Ge(1)
O(1)
Fig. 7. General view of associate 3a•6MeCN•H3O+. Hydrogen
atoms are not shown.
* Figures 5—7 are available in full color in the onꢀline version of
the journal (http://www.springerlink.com).

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Shipov et al.
Table 3. The topological characteristic and the bond energy values formed by the Ge atom in the isolated
molecule 3a and its solvate clusters
Compound
Ge(1)—O(1)
Ge(1)—O(2)
Ge(1)—Br(1)
Ge(1)—Br(2) Ge(1)—Br(3)
ρ(r)/e Å–3
3a
0.37
0.43
0.50
0.53
0.54
0.56
0.82
0.90
0.90
0.92
0.91
0.92
0.92
1.02
0.59
0.55
0.55
0.52
0.51
0.49
—
0.61
0.61
0.59
0.59
0.59
0.60
0.69
0.61
0.61
0.59
0.60
0.61
0.61
0.70
3a•2MeCN
3a•4MeCN
3a•6MeCN
3a•6MeCN•H2O
3a•6MeCN•HBr
3a•6MeCN•H3O+
2
∇ ρ(r)/e Å–5
3a
3.25
3.86
4.53
5.01
5.09
5.41
10.54
12.29
12.19
12.60
12.36
12.40
12.40
14.49
0.67
0.77
0.80
0.84
0.86
0.92
—
0.58
0.51
0.65
0.65
0.67
0.64
0.40
0.63
0.63
0.67
0.65
0.64
0.63
0.48
3a•2MeCN
3a•4MeCN
3a•6MeCN
3a•6MeCN•H2O
3a•6MeCN•HBr
3a•6MeCN•H3O+
Ee(r)/e Å–3
3a
–0.08
–0.11
–0.15
–0.17
–0.17
–0.18
–0.30
–0.34
–0.35
–0.36
–0.36
–0.36
–0.36
–0.43
–0.27
–0.24
–0.23
–0.22
–0.21
–0.19
—
–0.28
–0.28
–0.27
–0.27
–0.27
–0.28
–0.36
–0.28
–0.28
–0.27
–0.28
–0.28
–0.28
–0.35
3a•MeCN
3a•MeCN
3a•MeCN
3a•MeCN•H2O
3a•6MeCN•HBr
3a•6MeCN•H3O+
Ve(r)/au
3a
–0.06
–0.07
–0.09
–0.10
–0.10
–0.11
–0.20
–0.23
–0.23
–0.24
–0.23
–0.24
–0.24
–0.28
–0.09
–0.08
–0.08
–0.07
–0.07
–0.07
—
–0.09
–0.09
–0.09
–0.09
–0.09
–0.09
–0.11
–0.09
–0.09
–0.09
–0.09
–0.09
–0.09
–0.11
3a•2MeCN
3a•4MeCN
3a•6MeCN
3a•6MeCN•H2O
3a•6MeCN•HBr
3a•6MeCN•H3O+
Eb/kcal mol–1
3a
18.2
22.9
28.6
32.0
32.4
34.4
62.5
72.2
72.5
74.7
73.4
74.2
74.2
87.1
27.3
24.8
24.2
22.6
22.0
20.7
—
28.2
28.6
27.3
27.0
26.9
27.7
34.7
28.2
28.2
27.3
27.6
28.0
28.4
34.1
3a•2MeCN
3a•4MeCN
3a•6MeCN
3a•6MeCN•H2O
3a•6MeCN•HBr
3a•6MeCN•H3O+
bution of intermolecular C—H...Br interactions into
the values Esolv (3.3 and 9.3 kcal mol–1) is 2.2 and
3.8 kcal mol–1. In solvate clusters of more complicated
structure, the contribution of C—H...Br yet decreases,
whereas the value Esolv significantly increases (for
3a•6MeCN, 3a•6MeCN•H2O, and 3a•6MeCN•HBr it
is 15.6, 18.4, and 19.7 kcal mol–1, respectively).
value does not exceed 6.0 kcal mol–1 (in 5a•6MeCN),
despite a large number of such interactions (6—11). Inꢀ
corporation of an H2O molecule into the solvate cluster
3a•6MeCN resulted only in insignificant increase (to
6.3 kcal mol–1) of the overall energy of the interactions
involving bromine atoms. The part of the intermolecular
interactions is illustrated by the dependence between the
relative strengthening the Ge(1)—O(1) bond (as compared
to 3a) and the value Esolv. This dependence can be deꢀ
Almost in all solvate clusters, interactions between
the Br atoms and MeCN molecules are weak, their overall

Pentacoordinated germanium complexes
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
767
ΔGe—O
sion on the fact that transition of the electron density
occurs from the Ge(1) and Br(1) atoms toward the O(1)
atom. Thus, transition of electron density in the structure
of 3a occurs in the opposite direction as compared to comꢀ
pounds containing pentacoordinated silicon atom. This
agrees with the results of the work20 devoted to the quanꢀ
tum chemical calculations of halogermatranes.
Interaction of molecules 3a and the solvent makes posꢀ
sible redistribution of the electron density between them.
Analysis of atomic charge values allowed us to establish
the value and direction of the electron density transition.
It turned out that on the interaction of molecule 3a with
the solvent molecule, it acquires a small negative charge
(from –0.03 to –0.04 e) that indicates a certain outflow of
electron density from the solvent molecules.
In conclusion, the coordination Ge—O bond in comꢀ
plexes 3a, (S)ꢀ3b, and 3c proved stronger than in analoꢀ
gous complexes with the GeCl3 fragment studied
earlier.4c,11 The influence of a polar solvent leads to
a noticeable strengthening of the Ge—O bond and the
corresponding weakening the Ge—Br bond, which is acꢀ
companied by the increase in polarization of these bonds.
n = 6 + HBr
n = 6
0.20
0.18
0.16
0.14
0.12
0.10
0.08
n = 6 + H2O
n = 4
n = 2
4
6
8
10
12
14 16
20 Esolv
Fig. 8. The change of the bond distances (ΔGe—O) versus solvaꢀ
tion energy values (Esolv) calculated using the EML correlaꢀ
tion,17 the line obeys the equation ΔGe—O = 0.05 + 0.0744Esolv
.
scribed as linear with the correlation coefficient equal to
0.96 (Fig. 8).
The change of the Ge(1)—Br(1) and Ge(1)—O(1)
bond energies is a consequence of redistribution of elecꢀ
tron density in the axial O(1)—Ge(1)—Br(1) fragment.
Analysis of the charges calculated in the framework of the
AM theory (Table 4) showed that the largest changes are
observed for the Ge(1) atoms and the axial Br(1) atoms.
The increase of the positive charge on the Ge atom and
the negative charge on the Br(1) atom indicate polarizaꢀ
tion of the axial Ge(1)—Br(1) bond. The largest positive
charge on the Ge bond is observed in the case of full
dissociation of the Ge(1)—Br(1) bond. Charges on the
rest of the atoms are virtually unchanged on the shortenꢀ
ing of the Ge(1)—Br(1) bond.
Experimental
IR spectra were recorded on a Specord IRꢀ75 spectrometer
in KBr and Bruker IRꢀ20 IR Fourier in 0.1ꢀmm CaF2 cuvettes
for ∼5% solutions of compounds. 1H and 13C NMR spectra of
compounds studied in different solvents (C6D6, CDCl3, CD3CN,
DMSOꢀd6) were recorded on a Bruker Avance 400 and Varian
VXRꢀ400 spectrometers (400 and 100 MHz, respectively) with
Me4Si as an internal standard.
Specific rotation of optically active compounds was meaꢀ
sured on a VNIIKIProdmash 1ꢀEPO polarimeter in 0.5ꢀdm cuꢀ
vettes.*
According to the concept of the donating bond formuꢀ
lated for silatranes,13 transition of the electron density
occurs from the lone electron pair on the N atom to the
region of the Si—X bond (X is the exocyclic substituent).
The same notions were also used for the explanation of
a chemical bond in various monochelates with pentacoorꢀ
dinated Si atom.18,19 The use of charges calculated in the
framework of the AM theory allows one to draw concluꢀ
Commercial methyl (S)ꢀ2ꢀhydroxypropionate ((S)ꢀ4)
(Acros), [α]D22 –8.1° (c 2.00, CH2Cl2) was used in the work.
5ꢀMethylꢀ1,3ꢀdioxolanꢀ4ꢀone (5)21 and 5ꢀphenylꢀ1,3ꢀdiꢀ
oxolanꢀ4ꢀone (6)22 were obtained according to the procedures
described earlier.
* The authors are grateful to V. M. Dem´yanovich and E. Yu.
Smirnova for the measurement of specific rotation.
Table 4. The charges on the germanium atom and bound to it atoms calculated in the framework of the
AM theory
Compound
Ge(1)
O(1)
O(2)
Br(1)
Br(2)
Br(3)
3a
1.82
1.83
1.85
1.86
1.86
1.86
1.93
–1.17
–1.17
–1.17
–1.18
–1.18
–1.18
–1.15
–1.13
–1.14
–1.12
–1.13
–1.13
–1.13
–1.10
–0.45
–0.49
–0.50
–0.52
–0.51
–0.51
–0.29
–0.46
–0.42
–0.44
–0.44
–0.44
–0.44
–0.33
–0.46
–0.43
–0.44
–0.43
–0.43
–0.43
–0.35
3a•2MeCN
3a•4MeCN
3a•6MeCN
3a•6MeCN•H2O
3a•6MeCN•HBr
3a•6MeCN•H3O+

768
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
Shipov et al.
N,NꢀDimethylꢀ2ꢀtrimethylsiloxypropionamide (2a). Diꢀ
(CH2); 45.7, 46.1 (both s, NCH2); 69.7 (MeCH); 170.6 (C=O).
29Si (C6D6, δ: 15.7.
oxolanꢀ4ꢀone 5 (80.1 g, 0.78 mol) (see Ref. 21) was added dropꢀ
wise to a 30% aqueous dimethylamine (180 mL, 54 g, 1.2 mol)
with stirring. The reaction mixture was stirred for 1.5 h, then
kept for 2 days at ~20 °C, and fraction distilled to obtain
N,Nꢀdimethylꢀ2ꢀhydroxypropionamide (1a) (32.6 g, 36%),
(O→Ge)ꢀChelate (S)ꢀ2ꢀtribromogermyloxypropionpyrrolidide
((S)ꢀ3b). A (the ratio of reagents 2 : 1). Germanium tetrabroꢀ
mide (0.43 g, 0.001 mol) was added to a solution of pyrrolidide
(S)ꢀ2b (0.47 g, 0.002 mol) in hexane (6 mL), which was accomꢀ
panied by immediate formation of a light pink crystalline precipꢀ
itate. The reaction mixture was stirred for 1 h, the precipitate
was filtered off, washed with hexane, dried in vacuo of an oil
pump to yield pyrrolidide (S)ꢀ3b (0.31 g, 30%), m.p. 162.5 °C
(MeCN).
20
b.p. 130—132 °C (40 Torr), nD 1.4580 (cf. Ref. 23: b.p.
25
78.6—79.6 °C (4 Torr), nD 1.4571). Hexamethyldisilazane
(80 mL, 61.9 g, 0.53 mol) and Me3SiCl (10 mL, 8.6 g, 0.08 mol)
were added to the obtained dimethylamide 1a (32.6 g, 0.277 mol).
The reaction mixture was refluxed for 1.5 h and fraction distilled
to yield dimethylamide 2a (39.7 g, 75%), b.p. 96—98 °C
(14 Torr), nD20 1.4310. Found (%): C, 50.45; H, 10.13; N, 7.50.
C8H19NO2Si. Calculated (%): C, 50.75; H, 10.11; N, 7.40. IR
(CHCl3), ν/cm–1: 1630 (C=O). 1H NMR (CDCl3), δ: 0.07
B (the ratio of reagents 1 : 1). Pyrrolidide (S)ꢀ3b was obꢀ
tained similarly to the preceding experiment from pyrrolidide
(S)ꢀ2b (1.00 g, 0.005 mol) and GeBr4 (1.82 g, 0.005 mol). The
22
yield was 1.70 g (81%), m.p. 162 °C (with decomp.), [α]D
3
(s, 9 H, SiMe3); 1.31 (d, 3 H, CH3CH, JH,H = 6.9 Hz); 2.87,
–59.8° (c 1.85, CH2Cl2). The IR and 1H and 13C NMR spectra
of the samples synthesized in experiments A and B were identiꢀ
cal. Found (%): C, 18.63; H, 2.89; N, 3.10. C7H12Br3GeNO2.
3
3.06 (both s, 6 H, 2 NCH3); 4.51 (q, 1 H, CHCH3, JH,H
=
= 6.9 Hz). 13C NMR (CDCl3), δ: –0.22 (SiMe3); 20.88 (CHCH3);
35.71, 36.44 (NMe2); 68.62 (CHMe); 172.58 (C=O). 29Si
(CDCl3), δ: 16.1.
Calculated (%): C, 18.50; H, 2.66; N, 3.08. IR (CH2Cl2), ν/cm–1
:
1639 (NCO). 1H NMR (C6D6), δ: 0.83, 0.93 (both m, 4 H,
CH2CH2); 1.14 (d, 3 H, Me); 2.06, 2.14 (both m, 2 H, NCH2);
2.75, 2.85 (both m, 2 H, NCH2); 4.16 (q, 1 H, MeCH). 13C NMR
(CD3CN), δ: 19.2 (Me); 23.4 (CH2); 25.1 (CH2); 47.7, 48.8
(both s, NCH2); 68.5 (MeCH); 173.3 (C=O).
(O→Ge)ꢀChelate N,Nꢀdimethylꢀ2ꢀtribromogermyloxyproꢀ
pionamide (3a). Germanium tetrabromide (7.86 g, 0.02 mol) was
added dropwise to a solution of dimethylamide 2a (3.78 g,
0.02 mol) in hexane (35 mL) with stirring, which was continued
for another 2 h, then the reaction mixture was kept for 1 day at
~20 °C. Crystals formed were filtered off and washed with hexꢀ
ane to yield tribromide 3a (6.1 g, 71%), m.p. 117—120 °C (in
a capillary tube). A part of the compound was refluxed in MeCN.
The structure of oily crystals of tribromide 3a formed was conꢀ
firmed by Xꢀray diffraction analysis (see Fig. 1).
N,NꢀDimethylmandelamide (1c).* A solution of dioxolanꢀ4ꢀ
one (6)22 (10.5 g, 0.064 mol) in diethyl ether (10 mL) was added
dropwise to a solution of anhydrous dimethylamine (10.2 g,
0.226 mol, 15 mL) in anhydrous diethyl ether (20 mL) with
stirring and cooling to –5 °C. The reaction mixture was stirred
for 1 h at cooling and for another 20 min at ~20 °C. A precipitate
formed was filtered off and dried in vacuo to yield dimethylꢀ
amide 1c (11.4 g, 99%), m.p. 152—153 °C (hexane) (cf. Ref. 25:
m.p. 141—143 °C (ethyl acetate)). IR (Nujol), ν/cm–1: 1632
(C=O), 1620 (Ph). 1H NMR (CDCl3), δ: 2.76, 3.01 (both s, 6 H,
NMe2); 4.77 (br.s, 1 H, OH); 5.2 (s, 1 H, MeCH); 7.3—7.37
(m, 5 H, Ph). 13C NMR (CDCl3), δ: 36.3, 36.4 (NMe2); 71.6
(MeCH); 127.5, 128.5, 129 (Ph); 141.3 (Ci, Ph); 172.4 (C=O).
N,NꢀDimethylꢀOꢀtrimethylsilylmandelamide (2c). A mixture
of dimethylamide 1c (11.5 g, 0.065 mol), hexamethyldisilazane
(7.1 g, 0.044 mol), and Me3SiCl (0.1 g, 0.001 mol) was refluxed
with vigorous stirring for 3 h, during which dimethylamide 1c
was dissolved. Unreacted reagents were evaporated in vacuo,
fraction distillation yielded dimethylamide 2c (14 g, 86%), b.p.
93—94 °C (1 Torr). The compound solidified on standing, m.p.
Attempted purification of the crystals from the oil by recrysꢀ
tallization from acetonitrile or reprecipitation from the solution
in hot benzene by addition of hexane again led to oily crystals.
1
IR (CHCl3), ν/cm–1: 1630 (NCO). H NMR (CDCl3), δ: 1.47
3
(br.d, 3 H, CH3CH, JH,H = 6.9 Hz); 3.23—3.40 (br.m, 6 H,
3
2 NMe); 4.92 (br.q, 1 H, CHMe, JH,H = 6.9 Hz).
(S)ꢀ2ꢀHydroxypropionpyrrolidide ((S)ꢀ1b) was obtained from
methyl ester (S)ꢀ4 and pyrrolidine according to the procedure
described for the synthesis of racemic 1b.24 The yield was 60%,
20
b.p. 95—97 °C (1 Torr), nD 1.4890 (cf. Ref. 24 for racemate:
20
22
b.p. 134—135 °C (7 Torr), nD 1.4900), [α]D –53.6° (c 2.23,
CH2Cl2). Found (%): C, 58.52; H, 9.00; N, 9.87. C7H13NO2.
Calculated (%): C, 58.74; H, 9.09; N, 9.79. IR (neat), ν/cm–1
:
1654 (C=O). 1H NMR (C6D6), δ: 1.24 (m, 4 H, CH2CH2); 1.28
(d, 3 H, CH3CH); 2.65, 2.72 (both m, 2 H, NCH2); 3.24, 3.35
(both m, 2 H, NCH2); 4.17 (q, 1 H, MeCH). 13C NMR (C6D6),
δ: 20.6 (CH3CH); 23.5, 25.6 (both s, CH2); 45.2, 45.9 (both s,
NCH2); 65.4 (MeCH); 173.4 (C=O).
20
56—58 °C (cf. Ref. 4c: b.p. 154—155 °C (9 Torr), nD 1.4971).
Found (%): C, 62.45; H, 8.39; N, 5.35. C13H21NO2Si. Calcuꢀ
lated (%): C, 62.11; H, 8.42; N, 5.57. IR (CHCl3), ν/cm–1: 1648
1
(C=O), 1620 (Ph). H NMR (CDCl3), δ: 0.13 (s, 9 H, Me3Si);
(S)ꢀ2ꢀTrimethylsiloxypropionpyrrolidide ((S)ꢀ2b). Hexameꢀ
thyldisilazane (1.74 g, 0.011 mol) and Me3SiCl (0.1 g, 0.001 mol)
were added to compound (S)ꢀ1b (2.00 g, 0.014 mol), the mixture
was refluxed for 3 h with vigorous stirring, unreacted reagents
were evaporated in vacuo. Fraction distillation of the residue
gave pyrrolidide (S)ꢀ2b (2.05 g, 57%), b.p. 97—99 °C (1 Torr),
nD 1.4608, [α]D –20.4° (c 2.16, CH2Cl2). Found (%):
C, 55.88; H, 10.05; N, 6.74. C10H21NO2Si. Calculated (%):
C, 55.77; H, 9.83; N, 6.50. IR (neat), ν/cm–1: 1664 (C=O).
1H NMR (CDCl3), δ: 0.24 (s, 9 H, Me3Si); 1.34, 1.39 (both m,
4 H, CH2CH2); 1.45 (m, 3 H, Me); 3.23, 3.29 (both m, 2 H,
NCH2); 3.43, 3.45 (both m, 2 H, NCH2); 4.49 (s, 1 H, MeCH).
13C NMR (CDCl3), δ: 0.4 (Me3Si); 20.5 (Me); 23.5 (CH2); 26.3
2.82, 2.85 (both s, 6 H, NMe2); 5.48 (s, 1 H, MeCH); 7.19—7.41
(m, 5 H, Ph). 13C NMR (CDCl3), δ: –0.28 (MeSi); 35.53, 36.20
(NMe2); 76.53 (MeCH); 125.3, 127.47, 128.32 (Ph); 140.7
(Ci, Ph); 171.41 (C=O).
(O→Ge)ꢀChelate N,NꢀdimethylꢀOꢀtribromogermylmandelaꢀ
mide (3c). A. Dimethylamide 2c (1.26 g, 0.005 mol) was added
dropwise to a mixture of GeBr4 (1.96 g, 0.005 mol) and hexane
(5 mL) with stirring. The reaction mixture was stirred for 3 h and
kept for 1 day. Crystals formed were filtered off and washed with
hexane (10 mL) to obtain tribromide 6a (1.87 g, 76%), m.p.
185—188 °C (MeCN). Found (%): C, 24.35; H, 2.41; N, 2.81.
20
22
* With participation of N. S. Ivanov.

Pentacoordinated germanium complexes
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
769
Table 5. The main parameters of the Xꢀray diffraction experiment and crystallostructural data for compounds 1c, 3a, (S)ꢀ3b, and 3c
Parameter
1c
3a
(S)ꢀ3b
3c
Molecular formula
Molecular weight
Space group
Temperature/K
a/Å
b/Å
с/Å
α/deg
β/deg
C10H13NO2
179.21
C5H10Br3GeNO2
C7H12Br3GeNO2
454.50
C10H12Br3GeNO2
490.53
428.46
ꢀ
P21/c
100
P1
P212121
100
8.5569(5)
11.6449(7)
12.5983(8)
90.00
90.00
90.00
1255.35(13)
4
P212121
100
7.4248(4)
10.7590(6)
17.6215(10)
90.00
90.00
90.00
1407.67(14)
4
120
6.6228(11)
9.5629(17)
9.7359(17)
102.421(3)
104.602(3)
96.943(3)
572.63(17)
2
20.959(5)
6.1085(15)
14.648(4)
90.00
109.849(7)
90.00
1763.9(7)
8
1.350
γ/deg
V/Å3
Z
dcalc/g cm–3
μ/cm–1
2.485
131.1
2.405
119.7
2.315
106.8
0.9
Crystal size/mm3
Diffractometer
Tmin/Tmax
Total number of reflections
Number of independent
0.20×0.20×0.05
«Bruker APEX II»
0.981/0.995
14134
0.1×0.1×0.3
«Bruker Smart 1000»
0.085/0.462
8229
0.23×0.14×0.11
«Bruker APEX II»
0.150/0.263
18695
0.10×0.05×0.05
«Bruker APEX II»
0.415/0.617
16748
3377
3306
4377
3629
reflections (Rint
)
(0.089)
(0.063)
(0.049)
(0.044)
Number of reflections
1919
2279
3948
3441
with I > 2σ(I)
θ
max/deg
26.0
30.1
32.0
28.7
Divergence factors
R [I > 2σ(I)]
wR2
0.073
0.189
0.043
0.095
0.025
0.047
0.022
0.052
GOF
0.98
0.99
1.00
1.00
Number of refined parameters
Residual electron density/e Å
239
0.56/–0.27
113
1.46/–2.17
128
0.70/–0.58
156
0.52/–0.84
–3
,
Δρmax/Δρ
min
The Flank parameter
—
—
0.022(11)
0.010(12)
C10H12Br3GeNO2. Calculated (%): C, 24.49; H, 2.47; N, 2.86.
IR (MeCN), ν/cm–1: 1640 (NCO). 1H NMR (CDCl3), δ: 2.77,
3.16 (both s, 6 H, NMe2); 5.76 (s, 1 H, CH); 7.35—7.53 (m, 5 H,
Ph). 13C NMR (DMSO), δ: 39.9 (NMe2); 73.5 (CH); 127.6,
129.5, 138.9 (Ph); 175.18 (C=O).
B. A mixture of dimethylamide 2c (0.93 g, 3.7 mmol), GeBr4
(0.73 g, 1.85 mmol) in hexane (5 mL) was stirred for 2.5 h. The
following day, crystals formed were filtered off to obtain tribroꢀ
mide 3c (1.37 g, 75.5%), m.p. 182—185 °C (MeCN).
Xꢀray diffraction study of compounds 1c, 3a, (S)ꢀ3b, and 3c.
Monocrystals of 1c for Xꢀray diffraction analysis were obꢀ
tained by recrystallization of a sample from hexane, of pyrrolꢀ
idide (S)ꢀ3b and dimethylamide 3c, from acetonitrile; moꢀ
nocrystals of dimethylamide 3a were selected from the reaction
mixture.
Quantum chemical calculations. All the quantum chemical
calculations for the isolated molecule 3a and its associates were
performed with the full optimization of geometry using the
PCꢀGAMESS/FIREFLY 7.1.F program,27 partially based on
the GAMESSꢀUS program code.28 To confirm that the
optimized structures belong to the local minima, calculation
of the hessian matrix was performed. Topological analysis
and calculation of charges were performed using the AIMALL
program.29
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos 07ꢀ03ꢀ01067,
08ꢀ03ꢀ01071, and 09ꢀ03ꢀ00669) in the framework of acꢀ
tivity of the Scientific and Education Center of RSMU.
The structures of 1c, 3a—c were solved by the direct method
and refined in the fullꢀmatrix anisotropic approximation from
F2. Hydrogen atoms were calculated from geometric considerꢀ
ations and refined isotropically with imposing analogous restricꢀ
tions. All the calculations were performed using the SHELXTL
PLUS program package.26
The main bond distances and bond angles in the structures
studied are given in Table 1 and Fig. 4 Captions, the main
crystallostructural data, in Table 5.
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Received July 8, 2009;
in revised form December 15, 2009