Heteroorganic betaines 8. Synthesis and structures of silicon- and germanium-containing organoarsenic betaines R13As(1+)-CR2R3-EMe2-S(1-)- (E = Si, Ge)

Article abstract of DOI:10.1023/A:1015828520503

The reactions of ylides R¹3As=CHR² with hexamethyl-2,4,6-trisila- and hexamethyl-2,4,6-trigermatrithiacyclohexanes afforded betaines R¹3As(1+)-CHR²-SiMe2-S(1-) (2) (R¹ = Et; R² = Ph (a), Me3Si (b); R¹ = R² = Ph (c)) and Et3As(1+)-CH(SiMe3)-GeMe2-S(1-) (3), respectively. Betaines 2a,b and 3 were characterized by multinuclear NMR spectroscopy. According to the X-ray diffraction data, in the crystals the As(1+)-C-E-S(1-) main chain (E = Si or Ge) of molecules 2a,b and 3 adopts a twisted cis conformation due to strong intramolecular Coulomb interactions between the anionic and cationic centers. The equilibrium geometries of isolated molecules 2a and 3, which were calculated within the framework of the density functional theory (the PBE functional, the TZ2P basis set), are in qualitative agreement with the X-ray data. In solutions, betaines 2a (in the absence of Li salts) and 2c (in the presence of LiBr) selectively decomposed according to the Corey-Chaykovsky reaction, which was accompanied by elimination of R3As and, probably, the intermediate formation of silathiirane. The subsequent transformation of the latter afforded 2,2,4,4-tetramethyl-5-phenyl-2,4-disila-1,3-dithiolane.

Full text of DOI:10.1023/A:1015828520503

678
Russian Chemical Bulletin, International Edition, Vol. 51, No. 4, pp. 678—683, April, 2002
Organometallic Chemistry
Heteroorganic betaines
8.* Synthesis and structures of siliconꢀ and germaniumꢀcontaining organoarsenic betaines
R1 As+—CR2R3—EMe2—S– (E = Si, Ge)
3
a
b
c
a
c
I. V. Borisova,a N. N. Zemlyanskii, V. N. Khrustalev, M. S. Nechaev, M. G. Kuznetsova, and Yu. A. Ustynyuk
ꢀ
aState Research Center of the Russian Federation
"State Research Institute of Chemistry and Technology of Organoelement Compounds",
38 sh. Entuziastov, 111123 Moscow, Russian Federation.
Fax: +7 (095) 273 1323. Eꢀmail: zemlyan@mail.cnt.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5085. Eꢀmail: xray@xray.ineos.ac.ru
cDepartment of Chemistry, M. V. Lomonosov Moscow State University,
Leninskie Gory, 119899 Moscow, Russian Federation.
Fax: +7 (095) 939 2677. Eꢀmail: yust@nmr.chem.msu.su
The reactions of ylides R1 As=CHR2 with hexamethylꢀ2,4,6ꢀtrisilaꢀ and hexamethylꢀ
3
2,4,6ꢀtrigermatrithiacyclohexanes afforded betaines R1 As+—CHR2—SiMe2—S– (2) (R1 = Et;
3
R2 = Ph (a), Me3Si (b); R1 = R2 = Ph (c)) and Et3As+—CH(SiMe3)—GeMe2—S– (3),
respectively. Betaines 2a,b and 3 were characterized by multinuclear NMR spectroscopy.
According to the Xꢀray diffraction data, in the crystals the As+—C—E—S– main chain
(E = Si or Ge) of molecules 2a,b and 3 adopts a twisted cis conformation due to strong
intramolecular Coulomb interactions between the anionic and cationic centers. The equilibꢀ
rium geometries of isolated molecules 2a and 3, which were calculated within the framework
of the density functional theory (the PBE functional, the TZ2P basis set), are in qualitative
agreement with the Xꢀray data. In solutions, betaines 2a (in the absence of Li salts) and 2c (in
the presence of LiBr) selectively decomposed according to the Corey—Chaykovsky reaction,
which was accompanied by elimination of R3As and, probably, the intermediate formation of
silathiirane. The subsequent transformation of the latter afforded 2,2,4,4ꢀtetramethylꢀ5ꢀ
phenylꢀ2,4ꢀdisilaꢀ1,3ꢀdithiolane.
Key words: heteroorganic betaines, arsenic ylides, organosilicon and organogermanium
compounds, Xꢀray diffraction analysis, NMR spectroscopy, density functional theory.
Heteroorganic betaines have been extensively investiꢀ
gated in recent years. Various types of these compounds
were surveyed in reviews.2—5 Previously, we have reported
the synthesis of betaines R1 P+—CR2R3—ER4R5—S– (1)
3
(E = Si, Ge; R1—R5 = H, Alk, Ar) by the reactions of
"nonstabilized" phosphorus ylides with organocycloꢀ
* For Part 7, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 627—631, April, 2002.
1066ꢀ5285/02/5104ꢀ678 $27.00 © 2002 Plenum Publishing Corporation

Heteroorganic betaines. Synthesis and structure
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 4, April, 2002
679
silthianes (2,4,6ꢀtrisilatrithiacyclohexanes)6 and hexaꢀ
methylcyclotrigermathiane (2,4,6ꢀtrigermarithiacycloꢀ
hexane).1 The structures and major directions of decomꢀ
position of these betaines are similar to those observed in
the reactions of phosphorus ylides with thiocarbonyl comꢀ
pounds.7,8 The reactions of organocyclosilthianes and
hexamethylcyclotrigermathianes with arsenic ylides whose
reactivities are much higher than those of phosphorus
ylides9,10 allow one to prepare betaines bearing the arsoꢀ
Scheme 1
nium cationic center R1 As+—CR2R3—ER4R5—S– (E =
3
Si (2) or Ge (3)). These compounds can be prepared
with the use not only of "nonstabilized" but also of "semiꢀ
stabilized" arsenic ylides, which substantially extends the
scope of the synthesis of heteroorganic betaines containꢀ
ing the pnictogen cationic center.
E = Si (2a—c), Ge (3)
Previously,11,12 it has been demonstrated that carꢀ
bonꢀcontaining organophosphorus betaines bearing the
thiolate center can form a continuum of structures interꢀ
mediate between the open betaine and cyclic thiaꢀ
phosphetane structures. The true structures of these comꢀ
pounds depend substantially on small structural variaꢀ
tions and even the conditions in which these betaines are
studied. Previously, we have noted7 that the P—C—Si—S
R
1 = Et (2a,b, 3), Ph (2c)
R2 = Ph (2a,c), MeSi (2b, 3)
parameters of the compounds under study are given in
Table 1. The As+.....S– distances in betaines 2a,b and 3
(3.518, 3.497, and 3.565 Å, respectively) are substanꢀ
tially smaller than the sum of the van der Waals radii of
the S and As atoms (∼4.5 Å) and the P....S distances in
P,E—S betaines (E = Si, Ge). At the same time, the
As+.....S– distance is essentially larger than the As—S
single bond length (2.20—2.50 Å 13). In betaines 2b and
3, the As—C—E—S dihedral angle (E = Si, Ge) in the
main chain (22°) has the smallest value of all the known
betaines (25—38°) studied by us previously.1,7 The quanꢀ
tumꢀchemical DFT calculations for structures 2a and 3
with the extended splitꢀvalence basis set (PBE/TZ2P),
dihedral angles in betaines R1 P+—CR2R3—SiR4R5—S–
3
(1) vary essentially with the type of the substituents
R2–R5, which enables one to extend the range of
heteroorganic betaines. Investigations of betaines of the
arsenic series are of obvious theoretical interest for the
purpose of elucidating the effect of the type of the catꢀ
ionic center on the relative stabilities of the open and
cyclic forms of theses compounds.
The present study was devoted to heteroorganic beꢀ
taines 2 and 3 with the arsonium cationic center.
C(3)
C(2)
C(4)
Results and Discussion
C(5)
Compounds 2 and 3 were obtained in good yields by
mixing stoichiometric amounts of hexamethylcyclotriꢀ
silaꢀ or hexamethylcyclotrigermatrithianes with arsenic
ylides in THF or ether at ∼20 °C (Scheme 1).
S(1)
C(7)
As(1)
C(6)
Betaines 2a,b and 3 are crystalline white compounds,
which are stable for ∼1.5—6 months upon storage in the
solid state under an atmosphere of argon or in solutions
placed in a sealed vessel evacuated to ∼10–3 Torr. In
solution, betaine 2c is unstable and readily elimiꢀ
nates Ph3As.
According to the Xꢀray diffraction data, the main
chain +As—C—E—S– (E = Si, Ge) of compounds 2a,b
and 3 (Figs. 1—3), like that in all their siliconꢀ and
germaniumꢀcontaining organophosphorus analogs studꢀ
ied by us previously,7 adopts a sterically hindered
gaucheꢀcisoid conformation due to the intramolecular
Coulomb attractive As+.....S– interactions between the
cationic and anionic centers. The principal geometric
C(1)
Si(1)
C(8)
C(14)
C(15)
C(9)
C(10)
C(13)
C(12)
C(11)
Fig. 1. Molecular structure of compound 2a with thermal ellipꢀ
soids drawn at 50% probability level.

680
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 4, April, 2002
Borisova et al.
C(7)
C(3)
C(4)
C(5)
C(3)
C(5)
C(4)
C(6)
S(1)
C(6)
C(7)
As(1)
C(1)
C(2)
C(2)
S(1)
As(1)
Si(1)
C(1)
Si(2)
C(9)
Ge(1)
C(8)
C(11)
C(12)
Si(1)
C(11)
C(10)
C(12)
C(10)
C(9)
Fig. 2. Molecular structure of compound 2b with thermal ellipꢀ
soids drawn at 50% probability level.
C(8)
which were carried out analogously to those for betaines
of the phosphorus series, adequately reproduced the geꢀ
ometry observed in the crystals.1 The calculated geometꢀ
ric parameters and the Xꢀray diffraction data are given in
Table 1. The maximum corresponding to the cyclic form
is absent on the potential energy surface of 2a. However,
the results of calculations adequately reproduce the exꢀ
perimentally observed variations in the dihedral angle of
the main chain as the type of the cationic center changes.
It should also be noted that Xꢀray diffraction analysis
revealed the presence of a short nonbonded contact beꢀ
tween the hydrogen atom in the оrtho position of the
phenyl ring and the As atom (As(1)...H(9), 3.23(1) Å) in
compound 2a. This contact was attributed to steric hinꢀ
drances. Hence, the coordination polyhedron about the
As atom in 2a can be considered both as a distorted
tetrahedron and a distorted trigonal bipyramid with the
arsenic atom (0.655 Å) deviating substantially from the
equatorial C(1)—C(2)—C(6) plane of the bipyramid. In
solution, rotation about the CH—Ph bond is hindered
due to steric factors. This is manifested in broadening
both of the resonance signals for the Co and Cm atoms of
the phenyl ring in the 13C NMR spectrum and of the
Fig. 3. Molecular structure of compound 3 with thermal ellipꢀ
soids drawn at 50% probability level.
presence of the chiral carbon atom in molecule 2a, as
well as in betaines 2b,c and 3, causes diastereotopic douꢀ
bling of the signals of the methyl groups at the silicon or
germanium atom analogously to that observed previously
for their Si,Pꢀanalogs containing the asymmetric carbon
atom in the P—C—Si—S fragment.6
Betaine 2a, like its Si—P analog,8 selectively decomꢀ
posed according to the Corey—Chaykovsky reaction
upon irradiation of its solution in pyridineꢀd5 with UV
light using a mediumꢀpressure mercury lamp for 12 h
(Scheme 2). This reaction afforded disiladithiolane (5),
which was formed in virtually quantitative yield, and
triethylarsine as the final products. The reaction proꢀ
ceeded analogously to photodecomposition of betaines
of the phosphorus series, which we have studied previꢀ
ously.8
Highly reactive intermediate silathiirane 4 immediꢀ
ately reacted with the starting betaine 2a, which served
as a chemical scavenger. Subsequent elimination of
1
signals for the Ho atoms in the H NMR spectrum. The
Table 1. Principal geometric parameters* of betaines 2a,b and 3 containing the –S—E—C—As+ fragment accorring to the results of
Xꢀray diffraction analysis and PBE/TZ2P calculations
Betaine
Method
E
d/Å
ω/deg
E—C—As
ϕ/deg
S—E—C—As
S—E
E—C
C—As
S—As
S—E—C
2a
Xꢀray data
PBE/TZ2P
РСА
РСА
PBE/TZ2P
Si 2.0455(11)
2.083
1.946(4)
1.969
1.956(13)
2.032(3)
2.103
1.936(2)
1.986
1.931(13)
1.924(3)
1.944
3.518(2)
3.040
3.497(2)
3.565
109.97(8)
102.0
113.1(5)
111.68(9)
108.7
111.44(17)
105.1
110.0(7)
110.15(15)
1.944
33.13(19)
24.4
22.3(8)
21.74(16)
21.0
2b
3
Si
2.049(6)
Ge 2.1448(14)
2.164
3.441
* The distances (d), bond angles (ω), and torsion angles (ϕ).

Heteroorganic betaines. Synthesis and structure
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 4, April, 2002
681
Scheme 2
10–3 Torr immediately before use into an NMR tube containꢀ
ing the compound to be analyzed. Organochlorosilanes of reꢀ
agent grade purity were purchased from the Redkinskii pilotꢀ
production plant.
Chloromethyltrimethylsilane,14 tetramethylꢀ15 and diꢀ
methyldichlorogermane,16 hexamethyldisilthiane,17 hexaꢀ
methylcyclotrisilaꢀ18 and hexamethylcyclotrigermatrithiane,18
triethylꢀ19 and triphenylarsine,20 benzyl bromide,21 arsonuim
salts and arsenic ylides (except for benzylidenetriethylꢀ
arsenic),22,23 and sodium bis(trimethylsilyl)amide24 were preꢀ
pared according to procedures reported previously.
2ꢀMethylꢀ3ꢀphenylꢀ3ꢀtriethylarsonioꢀ2ꢀsilapropaneꢀ2ꢀ
thiolate, Et3As+—CHPh—SiMe2—S– (2a). The starting arsenic
ylide was prepared by the gradual addition of a solution of
NaN(SiMe3)2 (1.91 g, 10.4 mmol) in THF (20 mL) to a stirred
suspension of the salt [Et3As—CH2Ph]+ Br– (3.39 g, 10.2 mmol)
in THF (25 mL) at ∼10 °C. The reaction mixture was refluxed
for 10 min and then cooled. The precipitate of NaBr was filꢀ
tered off and washed on a filter with THF (∼20 mL). The
brightꢀorange volatile products were removed from the soluꢀ
tion at ∼20 °C (1 Torr). The oily residue was washed with
hexane, decanted, and kept at ∼20 °C (1 Torr) for 30 min. A
brownꢀred viscous oil was obtained in a yield of 2.11 g (82.3%).
Immediately afterwards, its solution in THF (15 mL) was added
portionwise to a solution of (Me2SiS)3 (0.82 g, 3 mmol) in
THF (10 mL) at 15 °C (the solution of the ylide immediately
turned colorless). The reaction mixture was kept at ∼15 °C for
12 h and the solvent was removed in vacuo (1 Torr). The finely
crystalline white precipitate that formed (2.78 g) was recrysꢀ
tallized from THF. A white compound was obtained in a
yield of 1.31 g (45.8%) as large crystals, m.p. 125 °C (with
decomp., sealed tube). 1H NMR (C5D5N), δ: 0.41 and 0.57
(both s, 3 H each, nonequivalent Me2Si groups); 1.17 (t, 9 H,
Et3As=CHPh from betaine 6 that formed afforded
disiladithiolane (5). It is particularly remarkable that
silathiirane 4 did not undergo dimerization, which was
always observed for its analogs deprived of the phenyl
group at the carbon atom.7 Arsenic ylide, like other repꢀ
resentatives of this class of compounds,9,10 decomposed
by the carbenoid mechanism to form Et3As and stilbene.
In a solution in pyridineꢀd5, betaine 2c produced comꢀ
pound 5 even in the absence of UV irradiation.
The results of the present study demonstrate that arꢀ
senic ylides are more reactive with respect to cycloꢀ
trisilatrithianes and cyclotrigermatrithianes, which allows
one to carry out the reactions with semiꢀstabilized
ylides. Studies of the chemical behavior of new betaines
CH3CH2As+, 3JH,H = 7.8 Hz); 2.63 and 2.93 (both dq, 3 H each,
3
CH3CH2As+, AM portion of the AMX3 spectrum, 3JAM ≈ JXM
=
7.8 Hz, JAM = 13.8 Hz); 3.69 (s, AsCHSi); 7.20—7.27 (m, 1 H,
Hp); 7.36—7.39 (m, 2 H, Hm); 7.50—7.52 (br.m, 2 H, Ho).
13C NMR (C5D5N), δ: 7.64, 8.79 (nonequivalent Me2Si groups);
8.11 (CH2As); 16.99 (CH3CH2As); 39.52 (AsCHSi); 126.58
(Cp); 129.21 (Cm); 130.06 (br, Co); 137.89 (Ci).
R1 As+—CR2R3—ER4R5—S– (2 and 3) are being conꢀ
3
tinued.
2,4,4ꢀTrimethylꢀ3ꢀtriethylarsonioꢀ2,4ꢀdisilapentaneꢀ
2ꢀthiolate, Et3As+—CHSiMe3—SiMe2—S– (2b). Ylide
Et3As=CHSiMe3 (1.65 g, 6.7 mmol) was added portionwise
with stirring to a solution of (Me2SiS)3 (0.70 g, 7.8 mmol) in
ether (10 mL) at ∼10 °C. After 15 min, the layers that formed
were separated and the solvents were removed at 20—100 °C
(0.1 Torr). A white powder was obtained from the residues of
the lower (1.3 g) and upper (0.58 g) layers, decomposition
temperature > 100 °C (in a sealed tube). According to the
NMR spectra, the resulting compound was betaine 2b. The
total yield was 83.6%. 1H NMR (C5D5N), δ: 0.32 (s, 9 H,
Me3Si); 0.60 and 0.66 (both s, 3 H each, nonequivalent Me2Si
Experimental
The 1H, 13C, and 29Si NMR spectra were recorded on a
Bruker AMꢀ360 instrument in C5D5N. The chemical shifts in
the 1H and 13C NMR spectra were measured relative to the
signals of the solvent with an accuracy of 0.01 and 0.05 ppm,
respectively, and were converted to the δ scale using standard
formulas. The 29Si NMR spectra were measured with respect
to SiMe4. The spinꢀspin coupling constants are given with an
accuracy of 0.1 Hz. The assignments of the signals of SiMe4
in the 13C NMR spectra were made using the APT procedure.
All operations were carried out under an atmosphere of dry
oxygenꢀfree argon using the standard Schlenk technique or in
vacuo (10–3 Torr) in seamlessꢀsoldered apparatus with the use
of a techniques of broken walls and tubes. Tetrahydrofuran and
Et2O were distilled over Na or LiAlH4, stored over sodium
benzophenone ketyl, and distilled over the latter into reaction
vessels immediately before use. The hydrocarbon solvents were
distilled over Na or LiAlH4; C5D5N used in NMR spectrosꢀ
copy was distilled over CaH2 and recondensed with LiAlH4 at
3
groups); 1.26 (t, 9 H, CH3CH2As+, JH,H = 7.7 Hz); 1.41 (s,
1 H, AsCHSi); 2.61 and 3.05 (both dq, 3 H each, CH3CH2As+,
3
AM portion of the AMX3 spectrum, JAM
≈
3JXM = 7.8 Hz,
2JAM = 13.6 Hz). 13C NMR (C5D5N), δ: 3.19 (Me3Si); 8.49
(CH3CH2As); 11.33, 12.37 (nonequivalent Me2Si groups); 16.06
(AsCHSi); 19.37 (CH2As). 29Si NMR (C5D5N), δ: +0.24
(Me2Si); +1.88 (Me3Si).
2,4,4ꢀTrimethylꢀ3ꢀtriethylarsonioꢀ2ꢀgermaꢀ4ꢀsilapentaneꢀ
2ꢀthiolate, Et3As+—CHSiMe3—GeMe2—S– (3). Ylide

682
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 4, April, 2002
Borisova et al.
Et3As=CHSiMe3 (2.33 g, 9.4 mmol) was added portionwise
with stirring to a solution of (Me2GeS)3 (1.27 g, 9.4 mmol) in
ether (20 mL) at ∼20 °C. After 2 h, the solvent was decanted
from the precipitate that formed and the compound was dried
in vacuo (1 Torr). A white crystalline compound was obtained
in a yield of 2.73 g (75.6%). This compound deliquesced upon
heating in a sealed tube at 71—72 °C and decomposed at
mal parameters for nonhydrogen atoms. The positions of the
hydrogen atoms were located from difference Fourier syntheses
and refined isotropically. The absolute structure was deterꢀ
mined by the refinement of Flack's parameter (0.00(1)). The
final R factors were as follows: R1 = 0.0383 for 4240 indepenꢀ
dent reflections with I > 2σ(I ) and wR2 = 0.0932 for all
4979 independent reflections.
1
98—100 °C (the product turned green). H NMR (C5D5N), δ:
A single crystal of compound 2b of dimensions
0.30 (s, 9 H, Me3Si); 0.77 and 0.82 (both s, 3 H each,
nonequivalent Me2Ge groups); 1.27 (t, 9 H, CH3CH2As+,
3JH,H = 7.7 Hz); 1.41 (br.s, 1 H, AsCHGe); 2.64 and 3.13
(both dq, 3 H each, CH3CH2As+, AM portion of the AMX3
spectrum, JAM ≈ JXM = 7.7 Hz, JAM = 13.6 Hz). 13C NMR
(C5D5N), δ: 2.96 (Me3Si); 8.35 (CH3CH2As); 11.87 and 13.11
(nonequivalent Me2Si groups); 14.47 (AsCHSi); 19.21 (CH2As).
29Si NMR (C5D5N), δ: + 0.59.
0.3×0.3×0.2 mm, which rapidly decomposed in air, was sealed
in a glass capillary in vacuo.
Crystals of 2b (C12H31AsSSi2, M = 338.53) are monoclinic,
space group P21/n, at T = 293 K a = 10.370(2), b = 12.681(3),
c = 14.550(3) Å, β = 99.99(3)°, V = 1884.2(7) Å3, Z = 4, dcalc
=
3
3
2
1.193 mg cm–3, F(000) = 720, µ = 2.023 mm–1
.
The unit cell parameters and intensities of 2731 reflections
were measured on an automated fourꢀcircle Siemens P3/PC
Reaction of benzylidenetriphenylarsorane with hexamethylꢀ
cyclotrisilthiane. A solution of Ph3As=CHPh, which was
prepared from a solution of [Ph3As+CH2Ph] Br– (7.91 g,
16.50 mmol) in ether (50 mL) and an ethereal 1 N solution of
PhLi (16.2 mL), was added to a solution of (Me2SiS)3 (1.49 g,
16.5 mmol) in ether (20 mL). The mixture was stirred for 1 h,
the solvents were decanted from the precipitate that formed,
and the precipitate was washed with hexane and dried in vacuo
(1 Torr). According to the NMR spectra, the resulting solid
compound was a mixture of 2,2,4,4ꢀtetramethylꢀ5ꢀphenylꢀ2,4ꢀ
disilaꢀ1,3ꢀdithiolane (5), triphenylarsine, and 1,2ꢀdiphenylꢀ
ethylene. 1H NMR of compound 5 (C5D5N), δ: 0.26, 0.48,
0.72, and 0.78 (all s, 3 H each, nonequivalent MeSi groups),
4.11 (CHPh); 7.09—8.81 (region of the Ar protons, overlapꢀ
ping of the signals of the Ph ring of disilolane 5 and isomers of
symmꢀdiphenylethylene). 13C NMR of compound 5 (C5D5N),
δ: 0.20, 1.33, 6.11, and 7.51 (nonequivalent MeSi groups);
41.26 (CH); 126.70, 128.05, 128.88, and 140.83 (Carom). The
13C NMR spectra of triphenylarsine correspond to the data
published in the literature.25
diffractometer (T = 293 K, λꢀMoꢀK radiation, θ/2θ scanning
α
technique, θmax = 23°). The absorption was ignored. The strucꢀ
ture was solved by direct methods and refined by the fullꢀ
matrix leastꢀsquares method with anisotropic thermal paramꢀ
eters for nonhydrogen atoms. The hydrogen atoms were placed
in geometrically calculated positions and refined isotropically
with fixed positional (the riding model) and thermal paramꢀ
eters. The final R factors were as follows: R1 = 0.1093 for
1611 independent reflections with I > 2σ(I ) and wR2 = 0.2847
for all 2530 independent reflections. The rather high R factor
was associated with the poor quality of the single crystal, the
high background intensity of Xꢀray radiation, and the fact that
it was impossible to correctly take into account absorption due
to the glass capillary used.
Crystals of 3 (C12H31AsGeSSi, M = 383.03) are monoꢀ
clinic, space group P21/n, at T = 120 К, a = 10.348(7), b =
12.307(8), c = 14.652(10) Å, β = 99.446(13)°, V = 1841(2) Å,
Z = 4, dcalc = 1.382 mg cm–3, F(000) = 792, µ = 3.607 mm–1
.
The unit cell parameters and intensities of 21309 reflections were
measured on an automated SMART CCD 1000 diffractometer
(T = 120 K, λꢀMoꢀKα radiation, ω scanning technique, scan
Photolysis of betaine 2a (NMR control). According to the
NMR spectroscopic data, irradiation of a solution of comꢀ
pound 2a (0.23 g) in pyridineꢀd5 (0.8 mL) in a sealed evacuated
Pyrexꢀcompatible NMR tube for 12 h (40—50 °C) afforded
2,2,4,4ꢀtetramethylꢀ5ꢀphenylꢀ2,4ꢀdisilaꢀ1,3ꢀdithiolane 5 (the
yield was ∼96%), Et3As (quantitative yield), and 1,2ꢀdiphenylꢀ
ethylene (quantitative yield).
step was 0.3°, frames were exposed for 10 s, θ
= 30°). The
max
absorption correction was applied using the SADABS program.26
The structure was solved by direct methods and refined by the
fullꢀmatrix leastꢀsquares method with anisotropic thermal paꢀ
rameters for nonhydrogen atoms. The positions of the hydroꢀ
gen atoms were located from difference Fourier syntheses and
refined isotropically. The final R factors were as follows: R1 =
0.0366 for 3651 independent reflections with I > 2σ(I ) and
wR2 = 0.826 for all 5391 independent reflections. All calculaꢀ
tions were carried out using the SHELXTL PLUS program
package (Version 5.10).27
NMR spectra of disiladithiolane 5 are identical with those
given above.
1H NMR of Et3As (C5D5N), δ: 1.10 (t, 9 H, CH3CH2As,
3JH,H = 7.7 Hz); 1.35 (quint, 6 H, CH3CH2As), which correꢀ
sponds to the data published in the literature.25 13C NMR of
Et3As (C5D5N), δ: 11.04 (CH3CH2As); 16.73 (CH3CH2As).
Xꢀray diffraction study. Crystals of betaine 2a (C15H27AsSSi,
M = 342.44) are orthorhombic, space group Pna21, at T =
110 K a = 15.4114(18), b = 8.6658(10), c = 12.8394(15) Å, V =
1714.7(3) Å3, Z = 4, dcalc = 1.326 mg cm–3, F(000) = 720, µ =
The tables of the atomic coordinates, bond lengths, bond
angles, torsion angles, and anisotropic thermal parameters for
compounds 2a,b and 3 were deposited with the Cambridge
Structural Database.
Calculation procedure. The calculations by the DFT method
were carried out using the original program.28 The exchangeꢀ
correlation energy was calculated with the use of the generalꢀ
ized gradient approximation and the PBE hybrid functional.29
The oneꢀelectron wave functions were expanded with the use
of the extended threeꢀexponential atomic TZ2P basis set of the
grouped Gaussian functions containing the polarization funcꢀ
tions. The stationary points were identified from the analysis of
the Hessian matrix. The second derivatives of the energy
2.158 mm–1
.
The unit cell parameters and intensities of 19298 reflecꢀ
tions were measured on an automated SMART CCD 1000
diffractometer (T = 110 K, λꢀMoꢀK , ω scanning technique,
α
scan step was 0.3°, frames were exposed for 10 s, θ
= 30°).
max
The absorption correction was applied using the SADABS proꢀ
gram.26 The structure was solved by direct methods and refined
by the fullꢀmatrix leastꢀsquares method with anisotropic therꢀ

Heteroorganic betaines. Synthesis and structure
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 4, April, 2002
683
with respect to the atomic coordinates were calculated anaꢀ
lytically.
12. T. Kawashima and R. Okazaki, Advances in Strained and
Interesting Organic Molecules, 1999, 7, 1.
13. Cambridge Crystal Structure Database, Cambridge, Reꢀ
lease 2000.
14. V. F. Mironov, Dokl. Akad. Nauk SSSR, 1956, 108, 266
[Dokl. Chem., 1956 (Engl. Transl.)].
15. L. H. Long and C. I. Pulford, J. Inorg. Nucl. Chem., 1968,
30, 2071.
16. H. Sakurai, K. Tominaga, T. Wantanabe, and M. Kumada,
Tetrahedron Lett., 1966, 5493.
17. J. H. So and P. Boudjouk, Synthesis, 1989, 306.
18. H.ꢀG. Horn and M. Hemeke, Chem. Ztg., 1982, 106, 263.
19. R. Appel and D. Rebhan, Chem. Ber., 1969, 102, 3955.
20. R. Armstrong, N. A. Gibson, J. W. Hosking, and D. C.
Weatherburn, Aust. J. Chem., 1967, 20, 2771.
21. Organischꢀchemisches Praktikum für das Grundstudium, VEB
Deutscher Verlag der Wissenschaften, Berlin, 1971.
22. I. Gosney, T. J. Zillie, and D. Lloyd, Angew. Chem., Int.
Ed. Engl., 1977, 16, 487.
23. W. Richter, Y. Yamamoto, and H. Schmidbaur, Chem. Ber.,
1977, 110, 1312.
24. Z. S. Novikova, S. N. Zdorova, V. A. Kirzner, and I. F.
Lutsenko, Zh. Obshch. Khim., 1976, 46, 575 [J. Gen. Chem.
USSR, 1976, 46 (Engl. Transl.)].
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos. 00ꢀ03ꢀ
32840a, 00ꢀ03ꢀ32807a, 00ꢀ03ꢀ32889a, and 00ꢀ15ꢀ97359).
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Received October 12, 2001