Hydrogallation of alkynes: Syntheses of carbon-gallium cages possessing heteroadamantane structures

Article abstract of DOI:10.1021/om020072u

A study was performed on hydrogallation of alkynes. The synthesis of carbon-gallium cages processing heteroadamantane structures was reported. The heteroadamantane-type compounds (GaR)₆(CR′)₄ were formed in which the positions of the methylene bridges of the carbon skeleton in adamantane were occupied by coordinatively unsaturated, tricoordinate gallium atoms.

Full text of DOI:10.1021/om020072u

Organometallics 2002, 21, 2365-2368
2365
Articles
Hyd r oga lla tion of Alk yn es: Syn th eses of
Ca r bon -Ga lliu m Ca ges P ossessin g Heter oa d a m a n ta n e
Str u ctu r es
Werner Uhl,* Lars Cuypers, Bernhard Neum u¨ ller, and Frank Weller
Fachbereich Chemie der Philipps Universit a¨ t Marburg, Hans-Meerwein-Strasse,
D-35032 Marburg, Germany
Received J anuary 30, 2002
Treatment of the alkynes R′CtCH (R′ ) Me, n-Pr) with dialkylgallium hydrides, R
R ) Me, Et), yielded symmetrical carbon-gallium cage compounds with release of
dihydrogen and subsequent addition of Ga-H to the CtC triple bonds. Heteroadamantane-
type compounds (GaR) (CR′) were formed in which the positions of the methylene bridges
2
GaH
(
6
4
of the carbon skeleton in adamantane were occupied by coordinatively unsaturated,
tricoordinate gallium atoms.
In tr od u ction
Sch em e 1
In some recent papers we reported the syntheses of
carbaalanes, a new class of compounds containing
1
-4
clusters of carbon and aluminum atoms.
These
compounds were obtained in high yield by the reaction
of dialkylaluminum hydrides with the corresponding
dialkyl(alkynyl)aluminum compounds. Two completely
different types of structures were determined. One has
the general formula (AlR′)8(CCH2R′′)5R 1 (R ) H, Ct
CPh, Scheme 1) and may be derived from a cube of eight
aluminum atoms, five faces of which are occupied by
carbon atoms. The sixth face is bridged by a hydrogen
atom.2 An open cage with one vertex of the aluminum
cube unoccupied was observed in one case only [(AlEt)7-
Resu lts a n d Discu ssion
,3
The syntheses of carbaalanes described above re-
quired the treatment of dialkyl(alkynyl)aluminum com-
pounds with an excess of the corresponding dialkylalu-
minum hydride. In some recent papers were published
2
(
CdCHPh)2(CCH2Ph)3H].4 The second type of car-
baalanes (AlR′)7(CCH2R′′)4R2 (R ) H, CtCMe) com-
prises cages with four carbon and seven aluminum
the facile syntheses of some dialkylgallium hydrides, R -
3
,4
6
7
8
atoms (2, Scheme 1).
Their structures are quite
GaH, with R ) Me, Et, iPr, iBu, neopentyl, and tBu,
similar to that of the closo-borate [B11H11]2 . Corre-
sponding gallium compounds were unknown until now.
We report here our first attempts to obtain such
compounds by hydrogallation reactions.
- 5
which were sufficiently thermally stable to allow a study
of their reactivity. In the cases of the gallium com-
pounds, we did not isolate the dialkyl(alkynyl)gallium
compounds, but generated them in situ by treatment
of the hydrides with the terminal alkynes propyne and
1
-pentyne. Hydrogen evolution was observed in each
(
1) (a) Uhl, W.; Breher, F. Eur. J . Inorg. Chem. 2000, 1. (b) Uhl, W.
In Carbaalanes-A New Class of Compounds Containing Clusters of
Aluminium and Carbon Atoms; Inorganic Chemistry Highlights;
Meyer, G., Wesemann, L., Naumann, D., Eds.; Wiley-VCH: Weinheim,
reaction. The postulated intermediates were consumed
immediately by the excess of the hydride while the
mixtures were stirred at room temperature. Pure,
crystalline products were isolated only in the case of the
dimethyl- and diethylgallium compounds. The corre-
2
002, p 229.
2) (a) Uhl, W.; Breher, F. Angew. Chem. 1999, 111, 1578; Angew.
(
Chem., Int. Ed. 1999, 38, 1477. (b) Uhl, W.; Breher, F.; Mbonimana,
A.; Gauss, J .; Haase, D.; L u¨ tzen, A.; Saak, W. Eur. J . Inorg. Chem.
2
001, 3059.
3) (a) Uhl, W.; Breher, F.; Grunenberg, J .; L u¨ tzen, A.; Saak, W.
(
(6) (a) Baxter, P. L.; Downs, A. J .; Goode, M. J .; Rankin, D. W. H.;
Robertson, H. E. J . Chem. Soc., Chem. Commun. 1986, 805. (b) Baxter,
P. L.; Downs, A. J .; Goode, M. J .; Rankin, D. W. H.; Robertson, H. E.
J . Chem. Soc., Dalton Trans. 1990, 2873.
Organometallics 2000, 19, 4536. (b) Uhl, W.; Breher, F.; Neum u¨ ller,
B.; L u¨ tzen, A.; Saak, W.; Grunenberg, J . Organometallics 2001, 20,
5
478.
(
4) Uhl, W.; Breher, F.; L u¨ tzen, A.; Saak, W. Angew. Chem. 2000,
(7) Uhl, W.; Cuypers, L.; Geiseler, G.; Harms, K.; Massa, W. Z.
Anorg. Allg. Chem., in press.
1
12, 414; Angew. Chem., Int. Ed. 2000, 39, 406.
(
5) Volkov, O.; Dirk, W.; Englert, U.; Paetzold, P. Z. Anorg. Allg.
(8) Uhl, W.; Cuypers, L.; Graupner, R.; Molter, J .; Vester, A.;
Neum u¨ ller, B. Z. Anorg. Allg. Chem. 2001, 627, 607.
Chem. 1999, 625, 1193.
1
0.1021/om020072u CCC: $22.00 © 2002 American Chemical Society
Publication on Web 05/09/2002

2
366 Organometallics, Vol. 21, No. 12, 2002
Uhl et al.
sponding trialkylgallium derivatives were detected as
byproducts in all reactions by NMR spectroscopy and
were removed in a vacuum at room temperature. As was
shown by crystal structure determinations (see below),
compounds were formed that differ from the carbaalanes
and contain heteroadamantane-like skeletons (GaR)6-
(CR′)4 with six coordinatively unsaturated gallium
atoms bridging four C-R′ groups (eq 1). The different
F igu r e 1. Molecular structure of 3. The thermal ellipsoids
are drawn at the 40% probability level. Methyl groups are
omitted for clarity. Important bond lengths (Å) and angles
(
deg): C(1)-Ga(1) 1.965(4), C(1)-Ga(4) 1.992(7), C(2)-Ga-
(
1) 1.980(4), C(2)-Ga(2) 1.968(4), C(2)-Ga(3) 1.981(4),
C(3)-Ga(3) 198.1(4), C(3)-Ga(4) 1.989(7), Ga(1)-C(11)
2
.067(4), Ga(2)-C(21) 1.981(7), Ga(3)-C(31) 1.984(4), Ga-
4)-C(41) 1.976(8), C(1)-Ga(1)-C(2) 120.9(2), C(2)-Ga-
(
(2)-C(2′) 118.7(3), C(2)-Ga(3)-C(3) 118.9(2), C(1)-Ga(4)-
C(3) 118.2(3), Ga(1)-C(1)-Ga(4) 102.7(2), Ga(1)-C(1)-
Ga(1′) 105.0(3), Ga(1)-C(2)-Ga(2) 101.7(2), Ga(2)-C(2)-
Ga(3) 109.4(2), Ga(1)-C(2)-Ga(3) 100.7(2), Ga(3)-C(3)-
Ga(3′) 106.6(3), Ga(3)-C(3)-Ga(4) 103.5(2); Ga(1′), Ga(3′),
and C(2′) generated by x, -y+0.5, z.
behavior may be caused by the different charge separa-
tion in organoaluminum and organogallium compounds.
The aluminum atoms bear a considerable positive
charge, and they are strong Lewis acids, while the
nature of the carbon-gallium bonds is rather covalent
with a preference of lower coordination numbers at
gallium. The obvious consequence of these differences
is the structure of trimethylaluminum, which in con-
trast to trimethylgallium forms a stable dimer via
carbanionic carbon bridges.
mantane cage. Further emissions in the range of Ga-C
stretching vibrations were detected between 275 and
-
1
5
55 cm
The molecular structures of compounds 3 and 4 were
established by two crystal structure determinations
Figures 1 and 2). They contain heteroadamantane
.
(
cages comprising four carbon and six gallium atoms
with carbon in µ3-bridging positions. The carbon atoms
are in a tetrahedral arrangement, while the gallium
atoms span a distorted octahedron. All gallium atoms
are coordinatively unsaturated, and this results in
The NMR spectra are in agreement with the observed
1
molecular structures. In the H NMR spectra of the
ethylgallium compounds 3 and 4 quartets were observed
for the different methylene groups in 2:3 intensity ratio.
The resonances of the groups attached to gallium are
shifted to a higher field (δ ) 1.0) compared to those that
are bonded to the carbon atoms of the cages (δ ) 2.8 on
average). An almost identical chemical shift (δ ) 2.7)
was observed for the methylene protons of the methyl
compound 5, while the methyl groups directly attached
to gallium showed a resonance at higher field (δ ) 0.18).
highly Lewis acidic molecular centers. In contrast to the
1-4
carbaalanes,
which, owing to electronic delocaliza-
tion, have long Al-C distances in their clusters, the
Ga-C distances of the gallium-carbon adamantanes
(1.965(4)-1.999(4) Å) do not show a significant depen-
dence on the terminal or inner-cage arrangement.
Exceptions are a few terminal Ga-C bonds which are
strongly elongated (2.067(4) Å, Ga(1)-C(11) and Ga(1′)-
C(11′) in compound 3; 2.060(7) Å, Ga(3)-C(31) in 4).
They seem to be influenced by some disorder, which,
however, could not be resolved satisfactorily in both
cases. The intramolecular Ga-Ga contacts are between
3.039 and 3.223 Å, smaller than twice the van der Waals
1
3
Similar differences were observed in the C NMR
spectra with about δ ) 0-10 for those carbon atoms of
the substituents that are attached to gallium and 26-
3
4 ppm for the methylene groups bonded to the carbon
9
atoms of the cage. The cage atom signals show unusu-
ally low-field shifts of δ ) 93-95, which may be caused
by the coordination of three electropositive, unsaturated
gallium atoms and by low-lying excited states. Similar
observations were reported for the analogous hexabora
adamantanes (δ ≈ 70), which are discussed in more
detail below. Raman spectra of 3-5 revealed very strong
radius (3.8 Å ), but much longer than Ga-Ga distances
in neutral clusters or than the bond lengths of Ga-Ga
1
0
single bonds (<2.7 Å ).
Carbon-element heteroadamantanes similar to com-
pounds 3-5 with elements of the third main group in
all µ2-bridging positions have been completely charac-
-1
(9) Huheey, J . E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry,
emissions at 195 cm for both ethyl derivatives and 217
4
th ed.; Harper Collins: New York, 1993.
10) (a) Uhl, W. Rev. Inorg. Chem. 1998, 18, 239. (b) Uhl, W. Coord.
Chem. Rev. 1997, 163, 1. (c) Uhl, W. Chem. Soc. Rev. 2000, 29, 259.
-
1
cm for the methylgallium compound 5, which may be
(
assigned to the symmetric breathing mode of the ada-

Hydrogallation of Alkynes
Organometallics, Vol. 21, No. 12, 2002 2367
Ta ble 1. Cr ysta l Da ta , Da ta Collection
P a r a m eter s, a n d Str u ctu r e Refin em en t Deta ils for
Com p ou n d s 3 a n d 4
3
4
formula
cryst syst
space group
Z
C24H50Ga6
C32H66Ga6
tetragonal
orthorhombic
Pnma (No. 62)15 P43 (No. 78)
15
4
4
temp, K
Dcalcd, g/cm3
a, Å
193(2)
1.706
193(2)
1.568
19.342(2)
13.2690(10)
11.4840(10)
2947.4(5)
5.416
16.1617(8)
16.1617(8)
14.0998(8)
3682.9(3)
4.345
b, Å
c, Å
V, 10
µ, mm
-
30
m3
-
1
cryst dimens, mm
radiation
0.2 × 0.1 × 0.04 0.2 × 0.2 × 0.1
Mo KR; graphite-monochromator
2
θ range, deg
4.1 e 2θ e 49.7
-21 e h e 22
3.5 e 2θ e 49.7
-19 e h e 19
-19 e k e 19
-16 e l e 16
6347
index ranges
-
15 e k e 15
13 e l e 12
-
F igu r e 2. Molecular structure of 4. The thermal ellipsoids
are drawn at the 40% probability level. Methyl and butyl
groups are omitted for clarity. Important bond lengths (Å)
and angles (deg): Ga(1)-C(1) 1.976(4), Ga(1)-C(2) 1.978-
no. of unique rflns
2670
[
Rint ) 0.0557]
[Rint ) 0.0513]
no. of params
R1 (reflns I > 2σ(I))
wR2 (all data)
161
0.0301 (2003)
0.0579
354
0.0261 (5771)
0.0541
0.652/-0.502
(
4), Ga(2)-C(1) 1.981(4), Ga(2)-C(3) 1.965(4), Ga(3)-C(3)
max./min. residual electron 0.690/-0.413
1
.970(4), Ga(3)-C(4) 1.987(4), Ga(4)-C(2) 1.980(4), Ga(4)-
density, 10 e/m3
30
C(4) 1.972(4), Ga(5)-C(2) 1.972(4), Ga(5)-C(3) 1.991(4),
Ga(6)-C(1) 199.4(4), Ga(6)-C(4) 1.974(4), Ga(1)-C(11)
1
-pentyne (ACROS Organics) was employed without further
1
.999(4), Ga(2)-C(21) 1.995(4), Ga(3)-C(31) 2.060(7), Ga-
purification.
(4)-C(41) 1.993(4), Ga(5)-C(51) 1.990(5), Ga(6)-C(61)
Syn th esis of Deca eth yl-2,4,6,8,9,10-h exa ga lla a d a m a n -
ta n e (Ga Et) (CEt) , 3. Diethylgallium hydride (3.01 g, 0.023
6 4
1
.980(5), C-Ga-C (cage) 119.6 (av), Ga-C-Ga 103.9 (av).
mol) was frozen with liquid nitrogen. Propyne (0.234 g, 0.0058
mol) was distilled onto the solid in a vacuum. The mixture
was warmed to -30 °C and stirred for 1 h. Stirring was
continued for 2.5 h after warming to room temperature. Gas
evolution was observed. All volatile components were removed
in a vacuum (10 Torr). The yellow residue was recrystallized
from n-pentane (20/-30 °C). Yield: 0.931 g (85%), yellow
crystals. Mp (argon, sealed capillary): 95 °C. Anal. Calcd for
terized only with the lightest element, boron. They were
obtained by different routes: by thermolysis of tri-
methylborane at 450 °C,11 by treatment of a 1,5-dicarba-
1
2
-3
closo-pentaborane(5) with potassium and iodine, or by
thermolysis of organoboron halides such as CH(BCl2)3
and Me2BBr.13 Remarkably, a rearrangement was ob-
served on heating of one of these compounds, [(BEt)6-
24 6
C H50Ga (757.0): C, 38.1; H, 6.7. Anal. Found: C, 37.8; H,
1
3
CMe)4], to 160 °C.12 A nido-carbaborane was formed
6.7. H NMR (C
Hz, Ga ), 1.25 (12 H, t, J H‚‚‚H ) 7.3 Hz, Ga
C-CH3
.22 (18 H, t, J H‚‚‚H ) 7.8 Hz, Ga-C-CH ), 0.97 (12 H, q, J H‚
, 100.6 MHz): δ 94.8
6 6
D , 200 MHz): δ 2.78 (8 H, q, J H‚‚‚H ) 7.3
(
3
3
2
3
3
C-C-CH ),
which, in contrast to the adamantane starting com-
pound, had direct B-B and C-C bonding interactions
and which was found to possess a dynamic B6C4 mo-
lecular center. A similar rearrangement was not ob-
served with the gallium compounds 3 and 4 up to now.
Elemental gallium precipitated upon heating of 3 and
3
1
‚
3
1
3
‚H ) 7.8 Hz, Ga-CH
Ga C), 26.6 (Ga C-C), 24.1 (Ga
.2 (GaC-CH ). IR (CsBr plates, paraffin, cm ): 1302 m δ-
2
). C NMR (C
6 6
D
(
9
3
3
3
C-C-CH
3
2
), 10.5 (GaCH ),
-1
3
(
CH); 1084 w, 1067 w, 1043 m, 1000 w, 981 w, 966 w, 931 w,
891 m ν(CC), δ,F(CH); 722 m, 664 vs, 650 vs, 633 vs δ(CC);
519 s, 431 s ν(GaC). Raman (powder, 633 nm, cm- ): 1449 w,
1419 vw, 1372 vw, 1308 vw, 1268 vw δ(CH); 1188 m, 1170 w,
1
4
without a solvent to 200 or 220 °C, respectively, but
in all cases the NMR spectra showed the resonances of
the starting components almost exclusively. New, un-
known compounds were formed in trace amounts, as
indicated by their very low NMR intensities; they could
not be enriched by recrystallization.
1
074 vw, 1047 w, 958 vw, 906 vw, 891 vw ν(CC), δ,F(CH); 534
m, 518 m, 440 m, 427 w, 275 m, 195 vs ν,δ(GaC). UV/vis (n-
hexane; λmax, nm (log ꢀ)): 260 (3.8), 280 (3.9).
Syn th esis of 2,4,6,8,9,10-Hexa eth yl-1,3,5,7-tetr a bu tyl-
2
6 4
,4,6,8,9,10-h exa ga lla a d a m a n ta n e (Ga Et) (CBu ) , 4. Di-
ethylgallium hydride (1.82 g, 0.014 mol) was treated with 0.24
g (0.0035 mol) of 1-pentyne without a solvent at room tem-
perature. The mixture was stirred at that temperature for 4
h. Gas evolution was observed, and a solid precipitated. All
volatile components were removed in a vacuum (10 Torr).
The yellowish residue was recrystallized from n-pentane (20/
Exp er im en ta l Section
All procedures were carried out under purified argon.
n-Pentane was dried over LiAlH
4
; toluene over Na/benzophe-
-3
none. Dimethylgallium hydride and diethylgallium hydride
were obtained according to literature procedures. Gaseous
propyne (Aldrich) was dried by passing it through P
7
-
30 °C). Yield: 0.603 g (79%), colorless crystals. Mp (argon,
sealed capillary): 114 °C. Anal. Calcd for C32 (869.2):
C, 44.2; H, 7.7. Anal. Found: C, 43.8; H, 7.6. Molar mass (in
4
O10, and
H
66Ga
6
(
11) (a) Brown, M. P.; Holliday, A. K.; Way, G. M. J . Chem. Soc.,
Dalton Trans. 1975, 148. (b) Rayment, I.; Shearer, H. M. M. J . Chem.
Soc., Dalton Trans. 1977, 136.
12) (a) K o¨ ster, R.; Seidel, G.; Wrackmeyer, B. Angew. Chem. 1985,
7, 317; Angew. Chem. Int. Ed. Engl. 1985, 24, 326. (b) K o¨ ster, R.;
Horstsch a¨ fer, H.-J .; Binger, P.; Mattschei, P. K. Liebigs Ann. Chem.
975, 1339.
13) Haubold, W.; Keller, W.; Sawitzki, G. J . Organomet. Chem.
989, 367, 19.
1
benzene by cryoscopy). Found: 842 g/mol. H NMR (C
MHz): δ 2.82 (8 H, pseudo-t, Ga C-CH ), 1.54 (16 H, m, br,
Ga C-C-CH CH ), 1.26 (18 H, t, H‚‚‚H ) 7.9 Hz, Ga-C-
C-C -CH ), 1.00 (12
, partially covered by the
, 100.6 MHz): δ 93.0
2 4
-Me), 34.3 (Ga C-CH -C H -
6 6
D , 300
3
2
3
(
3
2
2
J
9
3
CH
3
), 1.04 (12 H, t, J H‚‚‚H ) 7.4 Hz, Ga
3
3
3
H, q, 3
J
H‚‚‚H ) 7.9 Hz, Ga-CH
2
1
1
3
preceding resonance). C NMR (C
(Ga C), 43.8 (Ga C-CH -C
6 6
D
(
1
3
3
2
2
H
4
3
2

2
368 Organometallics, Vol. 21, No. 12, 2002
Uhl et al.
Me), 24.4 (Ga
Ga-CH -CH
3
C-CH
3
2
-C
3
2
H
4
-Me), 15.0 (Ga-CH
2
-CH
3
), 10.9
Cr ysta l Str u ctu r e Deter m in a tion s of 3 a n d 4. Single
crystals of 3 and 4 were obtained by cooling saturated solutions
in toluene (3) or n-pentane (4) to -30 °C. The crystallographic
data of both compounds were collected with a STOE image
plate diffractometer. The structure was solved by direct
(
2
), 9.8 (Ga
C-CH -C -Me). IR (CsBr plates,
2
2 4
H
-
1
paraffin, cm ): 1337 w, 1297 w, 1247 w, 1231 w δ(CH); 1187
vw, 1106 w, 1064 w, 1020 m, 972 m, 950 s, 897 vw, 874 vw
ν(CC), δ,F(CH); 793 vw, 721 w, 649 vs δ(CC); 521 s, 498 s, 393
-
1
14
w ν(GaC). Raman (powder, 633 nm, cm ): 2960 w, 2932 m,
899 m, 2870 m, 2858 m, 2824 m ν(CH); 1457 w, 1440 w, 1417
w, 1300 vw δ(CH); 1191 s, 1108 vw, 1069 w, 1032 w, 985 w,
methods and refined with the program SHELXL-97 by a full-
2
2
matrix least-squares method based on F . The molecules of 4
are located on a crystallographic mirror plane with the atoms
Ga2, Ga4, C1, and C3 on special positions. Crystal data, data
collection parameters, and structure refinement details are
given in Table 1. Further details of the crystal structure
determinations are available from the Cambridge Crystal-
lographic Data Center on quoting the depository numbers
CCDC-177349 (3) and -177350 (4).
9
3
64 vw, 939 vw, 899 vw, 876 w ν(CC), δ,F(CH); 534 sh, 512 vs,
98 vw, 196 vs ν,δ(GaC).
Syn th esis of 2,4,6,8,9,10-Hexa m eth yl-1,3,5,7-tetr a eth yl-
2
6 4
,4,6,8,9,10-h exa ga lla a d a m a n ta n e (Ga Me) (CEt) , 5. Di-
methylgallium hydride (0.836 g, 0.0083 mol) was frozen with
liquid nitrogen. Propyne (0.083 g, 0.0021 mol) was distilled
onto the solid in a vacuum. The mixture was allowed to warm
to -30 °C and stirred for 1 h. After warming to room
temperature, stirring was continued for 2.5 h. Gas evolution
occurred. All volatile components were removed in a vacuum,
and the colorless residue was recrystallized from toluene (20/
Ack n ow led gm en t. We are grateful to the Deutsche
Forschungsgemeinschaft and the Fonds der Chemischen
Industrie for generous financial support.
-
30 °C). Yield: 0.262 g (74%), colorless crystals. Dec pt (argon,
sealed capillary): >250 °C. Anal. Calcd for C18 (672.8):
C, 32.1; H, 5.7. Anal. Found: C, 31.6; H, 5.5. H NMR (C
H
38Ga
6
1
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, isotropic and anisotropic displacement param-
eters, and all bond lengths and angles. This material is
available free of charge via the Internet at http://pubs.acs.org.
6
6
D ,
3
3
00 MHz): δ 2.72 (8 H, q, J H‚‚‚H ) 7.4 Hz, Ga
3
C-CH
), 0.18 (18 H, s, Ga-
, 100.6 MHz): δ 94.4 (Ga C), 26.6 (Ga C-
C-C-CH ), 0.0 (Ga-CH ). IR (CsBr plates,
2
), 1.24
3
(12 H, t, J H‚‚‚H ) 7.4 Hz, Ga
3
C-C-CH
3
). 13C NMR (C
CH
CH
3
6
D
6
3
3
2
), 22.8 (Ga
3
3
3
-
1
OM020072U
paraffin, cm ): 1307 s δ(CH); 1187 m, 1152 s, 1083 m, 1068
m, 1044 s, 892 vs ν(CC), δ,F(CH); 793 w, 733 s, 683 vs δ(CC);
-1
6
08 vs, 538 vs, 432 vs ν(GaC). Raman (powder, 633 nm, cm ):
958 w, 2926 w, 2896 w, 2865 m, 2833 w ν(CH); 1448 w δ-
CH); 1190 m, 1167 m, 1057 w, 1049 w, 905 w, 895 w ν(CC),
δ,F(CH); 690 vw, 654 vw, 612 vw δ(CC); 555 s, 538 s, 442 m,
30 sh, 310 vw, 286 m, 217 vs, 148 w ν,δ(GaC).
(14) SHELXTL-Plus, REL. 4.1; Siemens Analytical X-Ray Instru-
ments Inc.: Madison, WI, 1990. Sheldrick, G. M. SHELXL-93, Program
for the Refinement of Structures; Universit a¨ t G o¨ ttingen, 1993.
2
(
(15) Hahn, T., Ed. International Tables for Crystallography, Space-
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4