Synthesis of (RSn)4X6 adamantanes (X = O, S, Se) in liquid ammonia and in the two-phase system liquid ammonia/THF

Article abstract of DOI:10.1002/(sici)1099-0682(199905)1999:5<869::aid-ejic869>3.0.co;2-2

The reactions of trisSnBr₃ (1) [tris = (Me₃Si)₃C] and nBuSnCl₃ with Na₂X (X = O, S, Se) yield the heterocyclic adamantanes 2-6. The reaction of 1 with Na20 is carried out in liquid ammonia under norma

Full text of DOI:10.1002/(sici)1099-0682(199905)1999:5<869::aid-ejic869>3.0.co;2-2

FULL PAPER
Synthesis of (RSn)4X6 Adamantanes (X ؍ O, S, Se) in Liquid Ammonia
and in the Two-Phase System Liquid Ammonia/THF
Karsten Wraage,[a] Thomas Pape,[a] Regine Herbst-Irmer,[a] Mathias Noltemeyer,[a]
Hans-G. Schmidt,[a] and Herbert W. Roesky*[a]
Dedicated to Professor Dietmar Seyferth on the occasion of his 70th birthday
Keywords: Adamantane / Liquid ammonia / Oxygen / Sulfur and selenium / Tin
The reactions of trisSnBr3 (1) [tris = (Me3Si)3C] and nBuSnCl3
pressure at room temperature results in the formation of
with Na2X (X = O, S, Se) yield the heterocyclic adamantanes
(trisSn)4S6 (3) and (trisSn)4Se6 (4). nBuSnCl3 reacts with Na2S
2–6. The reaction of 1 with Na2O is carried out in liquid and Na2Se in liquid ammonia at –33 °C under normal
ammonia under normal pressure at –78 °C to give (trisSn)4O6
(2). However, the reaction of 1 with Na2S and Na2Se under
pressure to give (nBuSn)4S6 (5) and (nBuSn)4Se6 (6),
respectively.
gives a singlet at δ ϭ 0.32 for the protons of the methyl
groups of the tris ligand, and 119Sn- and 29Si-NMR spectra
also show singlets (at δ ϭ Ϫ237.4 and 1.8, respectively).
The mass spectrum exhibits a peak at m/z 575 [Mϩ Ϫ Me].
The spectral data and elemental analysis confirm the com-
position of the compound to be C10H27Br3Si3Sn (1).
Compound 1 reacts with Na2X (X ϭ O, S, Se) in liquid
ammonia to give (RSn)4X6 [R ϭ tris; X ϭ O (2), S (3), Se
(4)]. While Na2O reacts with 1 at Ϫ 78°C under normal
pressure in liquid ammonia, Na2S and Na2Se, generated in
situ in liquid ammonia at Ϫ78°C, react under pressure in
liquid ammonia (Equations 2 and 3). The formation of
Na2S and Na2Se in situ is indicated by a color change of the
reaction medium from blue to yellow and red, respectively.
Introduction
Compounds of the type (RE)4X6 (E ϭ Si, Ge, Sn; X ϭ
S, Se) with an adamantane or a double-decker structure
have been reported.[1Ϫ3] Unno et al. described the synthesis
of (RE)4X6 compounds (E ϭ Si and Ge; X ϭ S and Se),
with a double-decker structure, which afforded the corre-
sponding adamantane upon heating.[1] Another contri-
bution by Berwe and Haas dealt with the reaction of
RSnCl3 with Na2S · 9 H2O and Me3SiSSiMe3, where a het-
erocyclic adamantane (RSn)4S6 was reported to be the
major product.[2]
Herein the synthesis of the hitherto unknown trisSnBr3
(1) [tris ϭ (Me3Si)3C] and a general method for the prep-
aration of (RSn)4X6 [R ϭ tris; X ϭ O (2), S (3), Se (4);
R ϭ nBu; X ϭ S (5), Se (6)] are reported.
Results and Discussion
Synthesis and Spectra
trisSnBr3 (1) is easily obtained by the treatment of tin
tetrabromide with tris(trimethylsilyl)methyllithium in di-
ethyl ether (Equation 1).[4] Compound 1 is a colorless, sub-
limable crystalline solid, whereas n-butyltin trichloride is a
liquid.
The proton-NMR spectrum of (trisSn)4O6 (2) shows four
singlets (δ ϭ 0.13, 0.24, 0.28, 0.51), as does the 29Si-NMR
spectrum (δ ϭ Ϫ1.0, Ϫ0.42, Ϫ0.27, Ϫ0.17), which indicates
that the tris groups are not equivalent. However, the four
tin atoms are equivalent and the compound gives only one
119Sn resonance (δ ϭ 94.3). The mass spectrum exhibits the
molecular ion peak at m/z (%) 1496 (100) [Mϩ].
Compound 1 was characterized by mass spectrometry
and NMR-spectral studies. The 1H-NMR spectrum of 1
[a]
Institut für Anorganische Chemie der Universität Göttingen,
Tammannstraße 4, D-37077 Göttingen, Germany
Fax: (internat.) ϩ 49(0)551/393373
E-mail: hroesky@gwdg.de
Eur. J. Inorg. Chem. 1999, 869Ϫ872
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ1948/99/0505Ϫ0869 $ 17.50ϩ.50/0
869

H. W. Roesky et al.
FULL PAPER
12 of the whole molecule exists in the asymmetric unit. Due
to this symmetry, each of the Sn atoms shows a distorted
tetrahedral geometry with three equivalent bridging oxygen
atoms and a terminal tris(trimethylsilyl)methyl group head-
ing away from the core. All SnϪO bond lengths are equal
[196.8(1) pm], as well as the SnϪC bond lengths [213.4(3)
pm] and the corresponding bond angles [OϪSnϪO
103.8(1)°, OϪSnϪC 114.7(1)°]. Two solvent molecules of
benzene exist close to the special position 1/4, 1/4, 0 and
appear to rotate freely.
Compounds (trisSn)4S6 (3) and (trisSn)4Se6 (4) were
characterized by elemental analysis, multinuclear NMR
spectra and mass spectrometry. Unlike in the case of 2, the
1H-NMR spectra of both compounds 3 and 4 show singlets
at δ ϭ 0.22 and 0.20, respectively. Similarly, the 29Si-NMR
spectra of 3 and 4 give singlets at δ ϭ 4.5. This indicates
that in both compounds the tris ligands are equivalent, un-
like in the case of 2. The 119Sn-NMR spectrum of 3 shows
a singlet (δ ϭ 72.8) which is downfield shifted compared to
that of 1 (δ ϭ Ϫ237.4) due to the formation of the hetero-
cyclic adamantane. It should be pointed out that 119Sn- and
77Se-NMR spectra could not be recorded in the case of 4
due to its instability in solution. Compound 4 decomposed
with the formation of selenium. The same behavior was ob-
served for the corresponding tellurium derivative.
The mass spectrum of 3 exhibits two intense peaks (m/z
1594 [Mϩ], 1579 [Mϩ Ϫ CH3]). However, no molecular ion
peak [Mϩ] could be observed for compound 4, instead a
peak at m/z (%) 1645 (100) [Mϩ Ϫ tris] was observed.
Similar to 1, nBuSnCl3 reacts with Na2S and Na2Se in
liquid ammonia at refluxing temp. (Ϫ33°C) to give
(nBuSn)4S6 (5) and (nBuSn)4Se6 (6), respectively.
Figure 1. Crystal structure of 2
3 (see Figure 2) is isomorphous with 2 but the O atoms
are replaced by S. This substitution leads to longer bonds
in the adamantane core [SnϪS 240.8(3) pm] and a longer
SnϪC bond [223(2) pm] in 3, causing the terminal tris(tri-
methylsilyl)methyl group to be disordered. Because of this
Compounds 5 and 6 were characterized by elemental
analysis, mass spectrometry and multinuclear NMR-spec-
1
tral studies. The H-NMR spectra of 5 and 6 give a typical
spectral pattern due to the nbutyl group. The 119Sn-NMR
spectra of 5 and 6 show singlets at δ ϭ 144 and Ϫ22, respec-
tively. This difference in resonances is due to the difference
in electronegativities of S and Se. The 77Se-NMR spectrum
of 6 exhibits a singlet at δ ϭ Ϫ169.9. Thus, the NMR-spec-
tral studies agree well with the proposed adamantane struc-
ture. The mass spectrum of 5 shows a peak at m/z (%) 839
(70) [Mϩ Ϫ n-butyl]. 6 is characterized in the gas phase by
two peaks: first the molecular ion peak at m/z (%) 1177
(20) and second the fragment at m/z (%) 1120 (90) [Mϩ
n-butyl].
Ϫ
In all cases we were unable to detect the coupling con-
stants of 117Sn/119Sn, 119Sn/77Se and 119Sn/29Si.
X-ray Structures of 2 and 3
The structure of 2 (see Figure 1) shows a highly sym-
metric, regular adamantane core (point group T) consisting
of tin and oxygen atoms. This geometry is defined by a
threefold axis through the SnϪC bond and three equivalent
twofold axes through two opposite O atoms, so that only 1/ Figure 2. Crystal structure of 3
870
Eur. J. Inorg. Chem. 1999, 869Ϫ872

Synthesis of (RSn)4X6 Adamantanes (X ϭ O, S, Se)
FULL PAPER
was opened and the liquid ammonia vaporized. Subsequently, the
residue was dissolved in 20 mL of toluene, the sodium bromide
filtered off and the filtrate concentrated in vacuo. Recrystallization
from benzene afforded 0.6 g (75%) of yellow crystals (decomp.
168°C). Ϫ C40H108S6Si12Sn4 (1593.56): calcd. C 30.15, H 6.78, S
disorder a mirror plane is added to the symmetry of the
data, the space group is FdϪ3m instead of FdϪ3 as in 2.
Conclusion
1
12.07, Si 21.15; found C 31.3, H 7.1, S 11.8., Si 21.3. Ϫ H NMR
(200 MHz, C6D6): δ ϭ 0.22 {s, 108 H, 4 C[Si(CH3)3]3}. Ϫ 29Si
NMR (49.7 MHz, C6D6): δ ϭ 4.5 (SiMe3). Ϫ 119Sn NMR(93.3
MHz, C6D6): δ ϭ 72.8 (Snad). Ϫ MS (EI); m/z (%): 1579 (100) [Mϩ
Ϫ Me], 1594 (45) [Mϩ].
In summary, we have shown that tin adamantanes con-
taining the chalcogens oxygen, sulfur and selenium are
easily accessible using liquid ammonia as a reaction media.
The structure of (trisSn)4O6 has been shown to have the
most regular adamantane core of this series
Syntheses of 4:Compound 4 was synthesized in an analogous man-
ner to that of 3. The reaction and isolation afforded 0.38 g (81%) of
a yellow/red powder (decomp. 195Ϫ205°C). Ϫ C40H108Se6Si12Sn4
(1874.92): calcd. C 25.62, H 5.81; found C 26.0, H 5.7. Ϫ 1H NMR
(200 MHz, CDCl3): δ ϭ 0.20 {s, 108 H, C[Si(CH3)3]3}. Ϫ 29Si
NMR (49.7 MHz, CDCl3): δ ϭ 4.5 (SiMe3). Ϫ MS (EI); m/z (%):
1645 (100) [Mϩ Ϫ tris].
Experimental Section
General: All reactions were carried out under dry nitrogen using
Schlenk techniques and a drybox. Solvents were dried and distilled
1
under nitrogen prior to use. Ϫ H NMR (200 MHz): Bruker AM
Synthesis of 5: Sulfur (0.144 g, 4.5 mmol) was suspended in 40 g
of liquid ammonia in a 100-mL Schlenk flask at Ϫ78°C. Sodium
(0.207 g, 9 mmol) was slowly added to this mixture. The reaction
mixture was stirred until it became yellow. nBuSnCl3 (0.847 g, 3
mmol) was then added to the suspension which was then allowed
to warm up to Ϫ33°C and refluxed in liquid ammonia for 2 h. The
liquid ammonia vaporized overnight. The residue was dissolved in
20 mL of n-hexane, the precipitate of sodium chloride filtered off
and the filtrate concentrated in vacuo, yielding 0.3 g (45%) of a
yellow powder (decomp. 130°C). Ϫ C16H36S6Sn4 (895.7): calcd. C
200. Ϫ 29Si NMR (49.7 MHz), 119Sn NMR (93.3 MHz), 77Se NMR
(47.7 MHz): Bruker AC 250 NMR, tetramethylsilane, tetrameth-
yltin and dimethylselenium, respectively, as external standards. Ϫ
MS: Bruker AM 200 MS, Bruker MSL 400 MS . Ϫ M.p.: Bühler
SPA-1. Ϫ The starting materials trisLi[4] and Na2X (X ϭ S, Se)[5]
were prepared by literature methods. Tin tetrabromide and n-but-
yltin trichloride were commercially available.
Synthesis of 1: A solution of (trisLi)2 · 4 THF (4.4 g, 5.7 mmol,
dissolved in 40 mL of diethyl ether) was added dropwise to a solu-
tion of SnBr4 (5.0 g, 11.4 mmol, dissolved in 30 mL of diethyl
ether) at Ϫ78°C while stirring. The reaction mixture was allowed
to warm up to room temp., and the residue was dissolved in 50 mL
of n-hexane and the precipitate of lithium bromide filtered off. 50%
of the solvent was removed in vacuo. Recrystallization of the crude
product at Ϫ30°C afforded 6.0 g (89%) of a colorless crystalline
1
21.46, H 4.05, S 21.48; found C 20.9, H 4.2, S 22.3. Ϫ H NMR
(200 MHz, CDCl3):
CH2CH2Snad), 1.35Ϫ1.50 (m,
δ
ϭ
0.85Ϫ0.95 (t, 12 H, CH3CH2-
H, CH3CH2CH2CH2Snad),
8
1.70Ϫ1.80 (m, 16 H, CH3CH2CH2CH2Snad). Ϫ 119Sn NMR (93.3
MHz, CDCl3): δ ϭ 144 (Snad). Ϫ MS (EI); m/z (%): 839 (70) [Mϩ
Ϫ nBu], 655 (100) [Mϩ Ϫ nBu Ϫ Sn Ϫ 2 S].
1
solid (sublimation at 155°C). Ϫ H NMR (200 MHz, C6D6): δ ϭ
Synthesis of 6: Selenium (0.355 g, 4.5 mmol) was suspended in 40
g of liquid ammonia in a 100-mL Schlenk flask at Ϫ78°C. Sodium
(0.207 g, 9 mmol) was added slowly to this mixture while stirring,
until the solution became red. Finally, n-butyltin trichloride (0.847
g, 3 mmol) was added. After warming up to Ϫ33°C, the mixture
was refluxed for 5 h. The liquid ammonia was vaporized overnight.
The residue was dissolved in 20 mL of n-hexane, the precipitated
sodium chloride filtered off and the solvent removed in vacuo to
yield 0.6 g (68%) of a yellow powder (decomp. 118°C). Ϫ
C16H36Se6Sn4 (1177.06): calcd. Sn 40.34; found Sn 40.5. Ϫ 1H
NMR (200 MHz, CDCl3): δ ϭ 0.90Ϫ1.00 (t, 12 H, 4 CH3-
CH2CH2CH2Snad), 1.35Ϫ1.55 (sext, 8 H, 4 CH3CH2CH2CH2Snad),
1.65Ϫ1.80 (quint, 8 H, 4 CH3CH2CH2CH2Snad), 1.90Ϫ1.98 (t, 8
H, 4 CH3CH2CH2CH2Snad). Ϫ 119Sn NMR (93 MHz, CDCl3): δ ϭ
Ϫ22 (Snad). Ϫ 77Se NMR (47 MHz, CDCl3): δ ϭ Ϫ165.5 (Snad-
Se1.5ad). Ϫ MS (EI); m/z (%): 1120.4 (90) [Mϩ Ϫ nBu], 1177 (20)
[Mϩ].
0.32 {s, 27 H, C[Si(CH3)3]3}. Ϫ 29Si NMR (49.7 MHz, C6D6): δ ϭ
1.8 [C(SiMe3)3]. Ϫ 119Sn NMR (93.3 MHz, C6D6): δ ϭ Ϫ237.4
(trisSnBr3). Ϫ MS (EI); m/z (%): 575 (100) [Mϩ Ϫ Me].
Synthesis of 2: Na2O (0.093 g, 1.5 mmol) was suspended in 30 g of
liquid ammonia at Ϫ78°C. 1 (0.59 g, 1 mmol) was dissolved in 20
mL of THF and added dropwise to the suspension of Na2O while
stirring. The reaction mixture was cooled at Ϫ78°C for 6 h and
then warmed up slowly to room temp. THF was removed in vacuo.
The remaining solid was dissolved in 50 mL of n-hexane, the pre-
cipitate of sodium bromide filtered off and the filtrate concentrated
in vacuo. The residue was a white solid (0.28 g, 80%). Recrystalliza-
tion from benzene resulted in colorless single crystals (m.p. >
250°C). Ϫ C40H108Si12Sn4O6 (1398.38): calcd. C 32.11, H 7.71;
1
found C 31.9, H 7.7. Ϫ H NMR (200 MHz, C6D6): δ ϭ 0.13 {s,
27 H, C[Si(CH3)3]3}, 0.24 {s, 27 H, C[Si(CH3)3]3}, 0.28 {s, 27 H,
C[Si(CH3)3]3}, 0.51 {s, 27 H, C[Si(CH3)3]3}. Ϫ 29Si NMR (49.7
MHz, C6D6): δ ϭ Ϫ1.0 (SiMe3), Ϫ0.42 (SiMe3), Ϫ0.27 (SiMe3),
X-ray Crystallographic Study:[6] Crystals were grown by cooling a
saturated solution of benzene (2) or benzene/trichloromethane (3)
to 8°C and then mounted on a glass fiber in a rapidly cooled per-
fluoro polyether.[7] Ϫ Crystal data for 2: C40H108O6Si12Sn4 ϩ 3
C6H6, M ϭ 1731.43, space group FdϪ3, a ϭ 2541.2(3) pm, V ϭ
Ϫ0.17 (SiMe3). Ϫ 119Sn NMR (93.3 MHz, C6D6): δ ϭ 94.3 (Snad
)
(ad ϭ adamantane). Ϫ MS (EI); m/z (%): 1496 (100) [Mϩ], 1481
(75) [Mϩ Ϫ Me].
Synthesis of 3: Sulfur (0.096 g, 3 mmol) was suspended in liquid
ammonia in a glass autoclave at Ϫ78°C. Sodium (0.138 g, 6 mmol) 16.41(10) nm3, Z ϭ 8, ρcalcd. ϭ 1.402 g cmϪ3, data collection: Stoe-
was added to the suspension while stirring. The stirring was con-
tinued until the color changed from blue to yellow. Solid 1 (1.18 g, CCD area detector, graphite-monochromated Mo-Kα radiation,
2 mmol) was added to the stirred suspension of sodium sulfide, and crystal size 0.5 ϫ 0.4 ϫ 0.4 mm, all measurements at 133(2) K, φ-
Siemens-Huber four-circle diffractometer, coupled to a Siemens
the glass autoclave was closed. The reaction mixture was allowed to and ω-collecting mode, 4.5° Յ 2θ Յ 59.5°, 92370 reflections meas-
warm up to room temp. After 25 min, the color of the reaction
mixture changed from yellow to green. After 24 h, the autoclave
ured, 1940 unique (Rint ϭ 0.0270), 1795 with I > 2σ(I), 1.419 mmϪ1
absorption coefficient, semi-empirical absorption correction from
Eur. J. Inorg. Chem. 1999, 869Ϫ872
871

H. W. Roesky et al.
FULL PAPER
tures (see Tables 1 and 2) were solved by direct methods using
SHELXS-97[8] and refined against F2 on all data by full-matrix
least squares with SHELXL-97.[9] All non-hydrogen atoms except
those of the solvent molecules were refined anisotropically. Hydro-
gen atom positions were calculated from idealized geometries and
refined using a riding model. In 2 solvent benzene molecules close
to the special position 1/4, 1/4, 0 could not be resolved properly,
and were refined using strong restraints on geometry and displace-
ment parameters. Special position constraints were suppressed. In
3 the electron density for the solvent showed an even more dis-
ordered site than in 2 so that the solvent molecules were refined as a
rigid benzene molecule and a strongly restrained trichloromethane
molecule. The two molecules share the same position, the sum of
their occupation factors is 1. Since this model does not describe
the true situation very well the difference electron density is compa-
ritively high. The severe disorder in structure 3 leads to a signifi-
cantly worse refinement compared to structure 2.
Table 1. Selected bond lengths [pm] and angles [°] of 2; symmetry
transformations for equivalent atoms are indicated
Sn(1)ϪO(1)
196.8(1)
213.4(3)
190.8(1)
103.8(1)
114.7(1)
120.0(1)
112.9(1)
105.8(1)
Sn(1)ϪC(1)
Si(1)ϪC(1)
O(1)ϪSn(1)ϪO(1)[a]
O(1)ϪSn(1)ϪC(1)
Sn(1)ϪO(1)ϪSn(1)[b]
Si(1)[c]ϪC(1)ϪSi(1)
Si(1)[c]ϪC(1)ϪSn(1)
[a]
[b]
[c]
Ϫx ϩ 3/4, Ϫy ϩ 3/4, z. Ϫ Ϫx ϩ 5/4, y, Ϫz ϩ 1/4. Ϫ x Ϫ
1/2, Ϫy ϩ 3/4, Ϫz ϩ 1/4.
Table 2. Selected bond lengths [pm] and angles [°] of 3; symmetry
transformations for equivalent atoms are indicated
Sn(1)ϪC(1)
223(2)
Sn(1)ϪS(1)
240.8(3)
191.2(7)
108.1(1)
110.8(1)
106.7(2)
112.3(5)
106.5(6)
C(1)ϪSi(1)
C(1)ϪSn(1)ϪS(1)
S(1)[a]ϪSn(1)ϪS(1)
Sn(1)ϪS(1)ϪSn(1)[b]
Si(1)ϪC(1)ϪSi(1)[a]
Si(1)ϪC(1)ϪSn(1)
Acknowledgments
This work was financially supported by the Deutsche Forschungs-
gemeinschaft.
[a]
[b]
Ϫx ϩ 3/4, Ϫy ϩ 1/4, z ϩ 1/2. Ϫ Ϫx ϩ 5/4, y ϩ 0, Ϫz ϩ 1/4.
[1]
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[2]
equivalents (0.5373Ϫ0.6007 transmission factors). Data/restraints/
parameters: 1940/181/124, final R1 ϭ 0.0265 for I > 2 σ(I) and
wR2 ϭ 0.0635 for all data {R1 ϭ ΣԽԽFoԽ Ϫ ԽFcԽԽ/ΣԽFoԽ, wR2 ϭ [Σ
H. Berwe, A. Haas, Chem. Ber. 1987, 120,1175Ϫ1182.
[3]
W. Ando, T. Kadowaki, Y. Kabe, M. Ishii, Angew. Chem. 1992,
104, 84Ϫ85; Angew. Chem. Int. Ed. Engl. 1992, 31, 59.
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S. S. Dua, C. Eaborn, D. A. R. Happer, S. P. Hopper, K. D.
2
2 2
w(Fo Ϫ Fc ) /Σ w(Fo2)2]1/2, wϪ1 ϭ σ2(Fo)2 ϩ (0.0180·P)2
ϩ
Safa, D. R. M. Walton, J. Organomet. Chem. 1979, 178, 75Ϫ82.
2
2
[5]
79.5121·P, P ϭ [Fo ϩ 2Fc ]/3}, largest peak and hole in final diff.
map 642 and Ϫ745 Crystal data for 3:
E. Zintl, A. Harder, B. Dauth, Z. Elektrochem. 1934, 40,
588Ϫ593.
ϭ
e
nmϪ3
. Ϫ
[6]
Further details of the crystal structure investigations are avail-
C40H108S6Si12Sn4 ϩ 1.57 C6H6 ϩ 0.43 CHCl3, M ϭ 1767.39, space
group FdϪ3m, a ϭ 2554.1(3) pm, V ϭ 16.66(10) nm3, Z ϭ 8,
ρcalcd. ϭ 1.409 g cmϪ3, data collection: Stoe-Siemens-AED2 four-
circle diffractometer, graphite-monochromated Mo-Kα radiation,
crystal size 0.5 ϫ 0.4 ϫ 0.4 mm, all measurements at 150(2) K,
learnt-profile method, 7.8° Յ 2θ Յ 49.3°, 6642 reflections meas-
ured, 713 unique (Rint ϭ 0.1007), 544 with I > 2σ(I), data/re-
straints/parameters: 713/33/76, final R1 ϭ 0.0673 for I > 2 σ(I) and
able on request from the Cambridge Crystallographic Data
Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK on
quoting the depository numbers CCDC-111980 for 2 and
-111981 for 3, the names of the authors, and the journal citation
[Fax: int. code ϩ 44-1223/336-033; E-mail: deposit@ccdc.cam.
ac.uk].
[7]
J. Kottke, D. Stalke, J. Appl. Crystallogr. 1993, 26, 615.
[8]
G. M. Sheldrick, SHELXS-97, Programm zur Strukturlösung,
Universität Göttingen, 1997.
[9]
G. M. Sheldrick, SHELXL-97, Programm für die Kristall-
wR2 ϭ 0.2304 for all data, wϪ1 ϭ σ2(Fo)2 ϩ (0.1268·P)2
ϩ
strukturverfeinerung, Universität Göttingen, 1997.
Received December 7, 1998
[I98419]
304.6513·P, largest peak and hole in final diff. map ϭ 1260 and
Ϫ1049 e nmϪ3. Ϫ Structural analysis and refinement: Both struc-
872
Eur. J. Inorg. Chem. 1999, 869Ϫ872