Synthesis of Bis(pentafluoroethyl)germanes

Article abstract of DOI:10.1002/chem.201505084

The chemistry of bis(pentafluoroethyl)germanes (C₂F₅)₂GeX₂ is presented. The synthesis of such species requires Br₂GePh₂, wherein the phenyl substituents function as suitable protecting groups. After treatment with two equivalents of LiC₂F₅, (C₂F₅)₂GePh₂ is produced. The replacement of the phenyl rings is smoothly effected by gaseous HBr or HCl in the presence of a Lewis acidic catalyst. The trigermoxane [(C₂F₅)₂GeO]₃ results from the reaction of (C₂F₅)₂GeBr₂ with Ag₂CO₃. Its crystalline 1,10-phenanthroline adduct was fully characterised by X-ray diffraction. The combination of (C₂F₅)₂GeBr₂ with Bu₃SnH gave rise to the formation of (C₂F₅)₂GeH₂.

Full text of DOI:10.1002/chem.201505084

DOI: 10.1002/chem.201505084
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Main-Group Chemistry |Hot Paper|
Synthesis of Bis(pentafluoroethyl)germanes
Stefanie Pelzer,[a] Beate Neumann,[a] Hans-Georg Stammler,[a] Nikolai Ignat’ev,[b] and
Berthold Hoge*[a]
Chem. Eur. J. 2016, 22, 4758 – 4763
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Abstract: The chemistry of bis(pentafluoroethyl)germanes
(C2F5)2GeX2 is presented. The synthesis of such species re-
quires Br2GePh2, wherein the phenyl substituents function as
suitable protecting groups. After treatment with two equiva-
lents of LiC2F5, (C2F5)2GePh2 is produced. The replacement of
the phenyl rings is smoothly effected by gaseous HBr or HCl
in the presence of a Lewis acidic catalyst. The trigermoxane
[(C2F5)2GeO]3 results from the reaction of (C2F5)2GeBr2 with
Ag2CO3. Its crystalline 1,10-phenanthroline adduct was fully
characterised by X-ray diffraction. The combination of
(C2F5)2GeBr2 with Bu3SnH gave rise to the formation of
(C2F5)2GeH2.
Introduction
the application of phenyl substituents as protecting groups al-
lowed the straightforward synthesis of the title compounds
(Scheme 1).
The field of trifluoromethylgermanium chemistry is well stud-
ied.[1] The replacement of methyl- by trifluoromethyl substitu-
ents in (CH3)4ÀnGeXn is accompanied by an increased Lewis
acidity of the central atom, which is easily rationalized by the
higher group electronegativity of the CF3 group.
Trifluoromethylgermanes have been synthesized by the reac-
tion of GeI4 with the highly toxic Hg(CF3)2. The latter reagent
cannot be replaced by LiCF3 because of its tendency to de-
compose at temperatures below À808C with liberation of LiF
and difluorocarbene.[2] Unfortunately, the use of Hg(CF3)2 led to
a product mixture which required a tedious and time-consum-
ing work-up. To circumvent those obstacles in the preparation
of perfluoroalkyl germanes, the use of pentafluoroethyl groups
is particularly promising. Owing to the decreased stability of
fluoro(trifluoromethyl)carbene, LiC2F5 is the C2F5 transfer re-
agent of choice. This organometallic compound is, in contrast
to LiCF3, stable in ethereal solution up to À408C.[3] It is readily
available by the reaction of n-butyllithium with pentafluoro-
ethane [Eq. (1)] at low temperatures and can be used directly
as a pentafluoroethylation reagent.
Scheme 1. Synthesis of dibromodiphenylgermane.
First, GePh4 was prepared in good yields by a previously de-
scribed Grignard reaction.[5] The elimination of two molecules
of benzene was achieved with gaseous HBr in a glass ampoule.
The produced Br2GePh2 was purified by fractional distillation.
Dibromodiphenylgermane selectively reacts with LiC2F5 to
form (C2F5)2GePh2, which was isolated from the reaction mix-
ture by distillation. The 19F NMR spectrum of the compound
shows a singlet at À81.2 ppm for the CF3 group and a singlet
at À117.3 ppm for the CF2 group. Subsequently, the remaining
protecting groups are removed by treatment with two equiva-
lents of gaseous HBr in the presence of AlBr3 at 708C to yield
bis(pentafluoroethyl)dibromogermane (Scheme 2). The purifica-
tion and separation from benzene was accomplished by iso-
thermal distillation.
ꢀC, Et2O
nBuLi þ C F H À80
LiC F
2 5
ð1Þ
ƒƒƒƒƒƒ!
2
5
ÀBuH
In the course of our enduring investigation of main-group
compounds featuring C2F5 groups, we turned our interest to
bis(pentafluoroethyl)germanium compounds.
Results and Discussion
A variety of tris(pentafluoroethyl)germanes was synthesized
previously[4] for which the use of the diethylamino substituent
was crucial as a protecting group. The direct treatment of
GeCl4 with three equivalents of LiC2F5 led to a plethora of
products.
Scheme 2. Synthesis of bis(pentafluoroethyl)dibromogermane.
The obvious reaction of Cl2Ge(NEt2)2 with two equivalents of
LiC2F5 as a possible method for (C2F5)2Ge(NEt2)2 suffered from
dismutation processes and was thus discarded. Fortunately,
A single crystal of (C2F5)2GeBr2 suitable for X-ray diffraction
analysis was grown by crystallisation of the liquid in a sealed
capillary in situ generating a crystal seed manually slightly
below the melting point at À918C followed by slow cooling to
À1738C (Figure 1). The compound crystallises in the chiral tet-
ragonal space group P43212. The GeÀBr bond lengths
(225.13(2) pm) are comparable to the one in (C2F5)3GeBr
(224.46(2) pm)[4] but significantly shorter than in dibromobis(2-
tert-butylphenyl)germane (dø 235 pm).[6] The coordination
sphere of the germanium atom is that of a slightly distorted
[a] S. Pelzer, B. Neumann, Dr. H.-G. Stammler, Prof. Dr. B. Hoge
Centrum für Molekulare Materialien
Fakultät für Chemie, Anorganische Chemie
Universität Bielefeld, Universitätsstrasse 25, 33615 Bielefeld (Germany)
E-mail: b.hoge@uni-bielefeld.de
[b] Dr. N. Ignat’ev
Consultant, Merck KGaA
Frankfurter Strasse 250, 64293 Darmstadt (Germany)
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The synthesis of (C2F5)2GeCl2 from (C2F5)2GePh2 was achieved
with anhydrous HCl and AlCl3 as a catalyst, under similar condi-
tions as the synthesis of (C2F5)2GeBr2. Unfortunately, it was im-
possible to separate benzene and the dichlorogermane
(C2F5)2GeCl2 by isothermal distillation because of their similar
properties. Therefore, a mixture of (C2F5)2GeCl2 and benzene
was used for characterisation. The 19F NMR data, complied in
Table 1, are comparable with (C2F5)2GeBr2.
Table 1. 19F NMR spectroscopic data for a series of bis(pentafluoroethyl)-
germanium compounds.
Compound
(C2F5)2GePh2
d (CF3) [ppm]
d (CF2) [ppm]
[a]
[b]
À81.2
À79.6
À81.1
À81.1
À83.6
À117.3
À116.5
À118.2
À120.8
À116.9
Figure 1. Molecular structure of (C2F5)2GeBr2 (ellipsoids set at 50% probabil-
ity). Selected bond lengths [pm] and angles [8]: Ge–Br 225.13(2), Ge–C
201.3(2); Br1-Ge-Br1’ 111.93(2), C1-Ge-C1’ 116.4(1), C1-Ge-Br1 109.72(5), C1-
Ge-Br1’ 104.61(5).
(C2F5)2GeBr2
[c]
(C2F5)2GeCl2
[d]
[(C2F5)2GeO]3
[a]
(C2F5)2GeH2
[a] CDCl3. [b] CHCl3. [c] n-pentane/[D6]acetone. [d] Et2O/[D6]acetone.
tetrahedron, with more obtuse angles for the Br-Ge-Br and C-
Ge-C than in comparison to the more compressed C-Ge-Br
angles (Figure 1).
The dichlorogermane solution was also analysed by IR spec-
troscopy in the gas phase (Table 2). The symmetrical and anti-
symmetric stretching vibrations of the GeCl2 unit were as-
signed to bands at 464 cmÀ1 and 440 cmÀ1 and agree well with
those in (CF3)2GeCl2 (466/442 cmÀ1).[7]
Dibromogermane (C2F5)2GeBr2 was further studied by IR
spectroscopy in the gas phase (Figure 2). As the bands for the
GeÀBr stretching vibrations appear below 400 cmÀ1, the here
obtained spectrum just shows the vibrations of the (C2F5)2Ge-
framework. The band at highest energy (1330 cmÀ1) is assigned
to the symmetrical CÀC stretching vibration of the C2F5
groups. The antisymmetric vibration is observed at a slightly
lower energy (1310 cmÀ1). The band with the highest intensity
at 1229 cmÀ1 and that at 1131 cmÀ1 result from C-F stretching
vibrations of the CF3 and the CF2 groups, respectively. The sym-
metrical and antisymmetric stretching vibrations of the GeÀC
bonds give rise to a band at 961 cmÀ1. At the lowest energy,
the bending vibrations of the CF3 groups afford a band at
747 cmÀ1.
Table 2. Selected IR spectroscopic data of (C2F5)2GeX2 (X=Br, Cl, H) in the
gas phase.
(C2F5)2GeBr2
n˜ [cmÀ1
(C2F5)2GeCl2
n˜ [cmÀ1
(C2F5)2GeH2
n˜ [cmÀ1
type of vibration
]
]
]
ns(CÀC)
1330
1310
1229
1131
961
747
–
1333
1312
1230
1134
965
748
464/440
–
1338
1316
1123
1140
968
724
2160/2143
846/724
nas(CÀC)
n(CÀF), CF3
n(CÀF), CF2
ns+as(GeÀC)
d(CF3)
n(Ge-X)
d(Ge-H2)
–
The reaction of dibromogermane (C2F5)2GeBr2 with dry silver
carbonate at 110 8C afforded the trigermoxane [(C2F5)2GeO]3
[Eq. (2)]. Despite the fact that this compound shows a high
tendency to crystallise, no single crystal of sufficient quality for
an X-ray study was obtained.
110 ꢀC, 4 days
ðC2F5Þ2GeBr2 þ Ag2CO3
1=3 ½ðC F Þ GeOŠ
ð2Þ
ƒƒƒƒƒƒƒ!
2
5
2
3
À2 AgBr, ÀCO2
Treatment of the heterocycle with 1,10-phenanthroline
(phen) gave an adduct that provides single crystals suitable for
X-ray diffraction. The germoxane adduct [(C2F5)2GeO]3·phen
crystallises in the orthorhombic space group Pccn (Figure 3).
The (GeO)3 six-membered ring is slightly puckered with torsion
angles below 88. As a consequence of the coordination of
phen, Ge1 is in the centre of a distorted octahedron and there
are two different values for the Ge-O-Ge (131.74(9)8/125.7(1)8)
Figure 2. IR spectra of (C2F5)2GeBr2 (gas phase), (C2F5)2GeCl2 (gas phase),
[(C2F5)2GeO]3 (ATR), and (C2F5)2GeH2 (gas phase) from bottom to top. Stars in-
dicate vibrations of benzene.
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1
1
Figure 4. 1H NMR spectra of (C2F5)2GeH2. Bottom: H, top: H{19F}.
Figure 3. Molecular structure of [(C2F5)2GeO]3·phen (ellipsoids set at 50%
probability). Selected bond lengths [pm] and angles [8]: Ge1–C1 2.057(3),
Ge2A–C3A 2.030(3), Ge2A–C5A 2.012(3), Ge1–O1 186.3(2), Ge2–O1 171.0(2),
Ge2–O2 176.1(1), Ge1–N1 210.5(2); O1-Ge1-O1 103.3(1), Ge1-O1-Ge2
131.74(9), O1-Ge2-O2 113.49(9), Ge2-O2-Ge2 125.7(1).
A crystal suitable for X-ray diffraction analysis was obtained
by in situ crystallisation of the liquid (C2F5)2GeH2 sealed into
a glass capillary by manually generating a seed crystal slightly
below the melting point of À988C. The germane (C2F5)2GeH2
crystallises in the orthorhombic space group Fdd2 (Figure 5).
and O-Ge-O (103.3(1)8/113.49(9)8) angles, respectively. For com-
parison, in the noncoordinated trigermoxane (tBu2GeO)3 angles
of 107.0(1)8 (O-Ge-O) and 133.0(1)8 (Ge-O-Ge) were measured.[8]
In [(C2F5)2GeO]3·phen we encountered three different GeÀO dis-
tances (Ge1ÀO1 186.3(2) pm, Ge2ÀO1 171.0(2) pm, Ge2ÀO2
176.1(1) pm). Again, they differ essentially from those in
(tBu2GeO)3 (GeÀO 178.1(1) pm).[8]
Treatment of a solution of the trigermoxane [(C2F5)2GeO]3
with water showed on the one hand the stability of the GeÀC
bond against hydrolysis. On the other hand the formation of
the germanol species (C2F5)2Ge(OH)2 was observed by 19F NMR
spectroscopy. This compound was also detected in the reac-
tion of (C2F5)2GeBr2 with water (Scheme 3).
Figure 5. Molecular structure of (C2F5)2GeH2 (ellipsoids set at 50% probabil-
ity). Selected bond lengths [pm] and angles [8]: Ge–H 131(3), Ge–C1 199.8(1);
C1-Ge-C1’ 101.95(6), H1-Ge-C1 112(1), H1-Ge-C1’ 114(1).
Scheme 3. Formation of the digermanol (C2F5)Ge(OH)2.
The GeÀH bond lengths of 131(3) pm are comparable to those
found in bis(2,6-dimesitylbenzyl)germane (130(4) pm).[9] With
the germanium atom coordinated nearly tetrahedrally, the
angles are clinched for the C-GeÀC angle (101.95(6)8) and wid-
ened for the H-GeÀC angles (112(1)8/114(1)8).
The pentafluoroethylated germane (C2F5)2GeH2 resulted from
the reaction of (C2F5)2GeBr2 with two equivalents of Bu3SnH
[Eq. (3)].
The gas-phase IR spectrum of (C2F5)2GeH2 (Figure 2) shows,
along with the fundamental vibrations of the (C2F5)2Ge unit,
also bands for the stretching vibrations of the GeH2 unit at
2160 cmÀ1 (asymmetrical) and 2143 cmÀ1 (symmetrical). De-
formation vibrations for the GeH2 unit are detected at
846 cmÀ1 (scissoring) and 724 cmÀ1 (wagging). These vibrations
are comparable with those of (CF3)2GeH2 and appear in the ex-
pected range.[10] However, comparison of the GeÀH stretching
vibrations with those of nonfluorinated germanes, such as
Et2GeH2 (2042 cmÀ1)[11] or PhGeH2 (2062 cmÀ1),[11] clearly shows
a hypsochromic shift.
18 h, rt
ðC F Þ GeBr þ 2 Bu SnH
ðC F Þ GeH
ð3Þ
ƒƒƒƒƒ!
2
5
2
2
3
2
5
2
2
À2 Bu3SnBr
3
Owing to a J(F,H) coupling of 10.2 Hz, the signal for the CF2
group in the 19F NMR spectrum was observed as a triplet at
À116.9 ppm. The signal for the CF3 group also appears as
4
a triplet with a J(F,H) coupling of 1.9 Hz. These couplings also
1
appear in the H NMR spectrum, where the GeÀH resonance
gave rise to a quintet of septets (Figure 4). Consistently, the
19F-decoupled H NMR spectrum is characterised by a singlet
1
with 13C satellites.
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Conclusions
Table 3. Structure and refinement data of (C2F5)2GeBr2, (C2F5)2GeH2 and
[(C2F5)2GeO]3·phen.
We presented a selective method for the synthesis of bis-
(pentafluoroethyl)germanium compounds. Employing the
phenyl group as a protecting group opens a straightforward
route to (C2F5)2GePh2.
(C2F5)2GeBr2
Crystallographic section
[(C2F5)2GeO]3·phen (C2F5)2GeH2
empirical formula C4Br2F10Ge
C24H8F30Ge3N2O3
1083.71(1)
1297.21(1)
2506.02(3)
3522.96(6)
4
C4H2F10Ge
1884.98(2)
1773.51(2)
536.552(8)
1793.71(4)
8
a [pm]
b [pm]
c [pm]
V”106 [pm3]
Z
864.616(8)
864.616(8)
1481.44(3)
1107.47(3)
4
The deprotection can be effected with gaseous HBr or HCl
under the assistance of a Lewis acidic catalyst at 708C. Treat-
ment of the dibromogermane (C2F5)2GeBr2 with Ag2CO3 gener-
ates the trigermoxane [(C2F5)2GeO]3, which readily forms a 1,10-
phenanthroline adduct. The latter was subjected to a X-ray
structural study. When the dibromogermane (C2F5)2GeBr2 was
treated with Bu3SnH, (C2F5)2GeH2 was formed. The molecular
structures of (C2F5)2GeBr2 and (C2F5)2GeH2 were elucidated by
X-ray diffraction after in situ crystallisation of the liquids sealed
into a glass capillary.
1calcd [mgmmÀ3
crystal system
space group
shape/colour
]
2.822
tetragonal
P43212
colourless in situ colourless
in a capillary fragment
2.187
2.315
orthorhombic
Pccn
orthorhombic
Fdd2
colourless in situ
in a capillary
crystal size
0.26”0.21”0.15 0.24”0.22”0.22 0.57”0.26”0.25
[mmÀ3
]
Data collection
diffractometer
Agilent
SuperNova
10.092
Nonius
Agilent
KappaCCD
2.737
SuperNova
3.542
m [mmÀ1
T [K]
]
Experimental Section
103(5)
200(2)
130.0(1)
All chemicals were obtained from commercial sources and used
without further purification. Standard high vacuum techniques
were employed throughout all preparative procedures. Nonvolatile
compounds were handled in a dry N2 atmosphere using Schlenk
techniques. The NMR spectra were recorded on a Bruker Model
Avance III300 spectrometer (19F 282.40 MHz; 13C 75.47 MHz; 1H
300.13 MHz) with positive shifts being downfield from the external
F(000)
864.0
2224
6.92 to 54.98
1184.0
8.226 to 90.586
2q range for data 6.664 to 60.06
collection [8]
À12ꢁhꢁ12
À14ꢁhꢁ14
À16ꢁkꢁ16
À32ꢁlꢁ32
41923
À37ꢁhꢁ37
À35ꢁkꢁ35
À10ꢁlꢁ10
70225
index ranges
À12ꢁkꢁ12
À20ꢁlꢁ20
60760
reflections
collected
1
standards (CCl3F (19F) and TMS (13C, H)). IR spectra were recorded
independent
reflections
data/restraints/
parameters
goodness-of-fit
on F2
1621
4036
3713
[R(int)=0.0374]
3713/1/74
on an ALPHA-FT-IR spectrometer (Bruker Daltonik GmbH, Bremen,
Germany) using a gas cell with KBr windows or an ATR unit with
a diamond crystal for liquids and solids. The crystal data were col-
lected using graphite-monochromated MoKa radiation (l=
71.073 pm). Using Olex2,[12] the structure was solved with the
ShelXS[13] structure solution program using direct methods and re-
fined with the ShelXL[13] refinement package using least-squares
minimization. All atoms were refined anisotropically, except hydro-
gen atoms, which were refined isotropically. Details of the X-ray in-
vestigations are given in Table 3. CCDC 1441604 ((C2F5)2GeBr2),
1441605 ([(C2F5)2GeO]3·phen), and 1441606 ((C2F5)2GeH2) contain
the supplementary crystallographic data for this paper. These data
are provided free of charge by The Cambridge Crystallographic
Data Centre.
[R(int)=0.0358] [R(int)=0.037]
1621/0/79
4036/0/281
1.103
1.065
1.101
R1/wR2 [Iꢁ2s(I)]
0.0118/0.0283
[1588]
0.0124/0.0285
0.37/À0.25
0.001(3)
0.0311/0.0814
[3590]
0.0362/0.0846
0.764/À0.409
0.0186/0.0445
[3416]
0.0223/0.0458
0.34/À0.46
R1/wR2 (all data)
D1max/min [eŠ
Flack parameter
CCDC number
À3
]
1441604
1441605
1441606
under reduced pressure yielded Br2GePh2 as a colourless liquid
(1.75 g, 4.55 mmol, 41%). B.p.: 908C (1·10-3 mbar); H NMR (CDCl3,
1
Synthesis of tetraphenylgermane: The Grignard reagent PhMgBr
was synthesized from magnesium (13.44 g, 53.0 mmol) and bromo-
benzene (54 mol) in THF (total 180 mL). Excess magnesium was re-
moved and a solution of GeCl4 (11.28 g, 52.61 mmol) in THF
(60 mL) was added dropwise at room temperature. The reaction
mixture was heated under reflux for 18 h. Cooling the mixture to
08C led to the separation of a precipitate, which was filtered off
and washed with diluted acetic acid. After drying in vacuo, GePh4
was obtained as colourless crystals (14.73 g, 38.66 mmol, 74%).
1H NMR (CDCl3, 258C): d=7.61–7.51 (m, 8H; Harom), 7.45–7.34 ppm
(m, 12H; Harom); 13C{1H} NMR (CDCl3, 258C): d=136.1 (s; Cipso), 135.4
(s; C(2,6)), 129.1 (s; C4), 128.3 ppm (s; C(3,5)); MS (EI, 70 eV, pos.):
m/z (%): 305 (100) [Ge(C6H5)3+], 228 (60) [Ge(C6H5)2+], 151 (9)
[Ge(C6H5)+].
208C): d=7.82–7. 61 (m, 4H; Harom), 7.62–7.43 ppm (m, 6H; Harom);
13C{1H} NMR (CDCl3, 208C): d=135.3 (s; Cipso), 132.7 (s; C(2,6)), 131.7
(s; C(4)), 129.0 ppm (s; C(3,5)); MS (EI, 70 eV, pos.): m/z (%): 386 (7)
[Ge(C6H5)2Br2 +], 307 (100) [Ge(C6H5)2Br+], 153 (18) [GeBr+], 151
C
(19) [GePh+], 77 (58) [C6H5+], 51 (45).
Synthesis of bis(pentafluoroethyl)diphenylgermane: A sample of
C2F5H (62 mmol) was condensed onto a mixture of a solution of n-
butyllithium in n-hexane (1.6m) (34 mL, 54 mmol) and Et2O
(100 mL) at À788C. The solution was stirred for 20 min, before
Br2GePh2 (8.98 g, 23.4 mmol) was added dropwise at À608C. The
reaction mixture was allowed to reach room temperature. The
formed precipitate was filtered off and the filtrate was freed from
solvent under reduced pressure. Fractional distillation of the crude
product in high vacuum yielded (C2F5)2GePh2 (9.23 g, 19.9 mmol,
85%) as a colourless liquid. B.p.: 718C (1”10À3 mbar); 1H NMR
(CDCl3, 238C): d=7.68–7.65 (m, 4H; Harom), 7.62–7.57 (m, 2H; Harom),
7.54–7.49 ppm (m, 4H; Harom); 13C NMR (CDCl3, 238C): d=135.1 (s,
Carom), 131.7 (s, Carom), 129.1 (s, Carom), 125.3 ppm (s, Cipso); 13C{19F}
NMR (CDCl3, 238C): d=121.1 (s; CF2), 119.5 ppm (s; CF3); 19F NMR
Synthesis of dibromodiphenylgermane: In a 750 mL glass am-
poule equipped with a Young valve, HBr (23.7 mmol) was con-
densed onto GePh4 (4.22 g, 11.10 mmol). The reaction mixture was
stirred for 3 days at 1408C. The obtained mixture was subjected to
a fractional condensation to remove excess HBr, and the product
mixture was collected in the À788C trap. Fractional distillation
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(CDCl3, 238C): d=À81.2 (s, 6F; CF3), À117.3 ppm (s, 4F; CF2); IR
(ATR): n˜ =3083 (w), 3062 (w), 1726 (w), 1489 (w), 1435 (m), 1323
(w), 1302 (m), 1196 (s), 1111 (s), 1087 (s), 1029 (w), 999 (w), 951 (s),
852 (w), 734 (s), 693 (s), 679 (w), 609 (w), 588 (w), 537 (w), 459 (s),
434 cmÀ1 (w); MS (EI, 70 eV, pos.): m/z (%): 589 (4), 571 (1), 489 (3),
427 (2), 411 (2), 373 (2), 347 (17) [Ge(C2F5)(C6H5)2+], 325 (2)
[Ge(C6H5)3F+], 305 (15) [Ge(C6H5)3+], 247 (100) [Ge(C6H5)2F+], 227
(2), 189 (9) [Ge(C6H5)F2+], 151 (23) [Ge(C6H5)+], 139 (30), 127 (22)
[C7H5F2+], 119 (11) [C2F5+], 93 (14) [GeF+], 77 (67) [C6H5+].
[D6]acetone, 238C): d=À81.1 (s, 18F; CF3), À120.8 ppm (s, 12F;
CF2); IR (ATR): n˜ =1337 (w), 1313 (m), 1202 (s), 1114 (s), 966 (m),
875 (s), 745 (s), 613 (w), 589 (w), 541 (m), 529 (w), 433 (w),
419 cmÀ1 (w).
Complexation of hexakis(pentafluoroethyl)trigermoxane with
1,10-phenanthroline:
A
sample of [(C2F5)2GeO]3 (0.054 g,
0.55 mmol) was treated with 1,10-phenanthroline (0.010 g,
0.056 mmol) in acetonitrile (2 mL). Heating the reaction mixture up
to 508C and slowly cooling down to room temperature yielded
[(C2F5)2GeO]3·phen as single crystals suitable for X-ray diffraction
studies.
Synthesis of bis(pentafluoroethyl)dibromogermane: In a 750 mL
glass ampoule equipped with a Young valve HBr (22.9 mmol) was
condensed onto (C2F5)2GePh2 (3.15 g, 6.78 mmol) and AlBr3 (0.12 g,
0.45 mmol). The reaction mixture was stirred for 18 h at 708C. After
fractional condensation (À788C, À1968C) and removal of benzene
by isothermal distillation (1”10À3 mbar, À158C), the product was
obtained as a colourless liquid (1.68 g, 3.59 mmol; 53%). 13C{19F}
NMR (CHCl3/[D6]acetone, 238C): d=122.5 (s; CF3), 119.5 ppm (s;
CF2); 19F NMR (CHCl3/[D6]acetone, 238C): d=À79.6 (s, 6F; CF3),
À116.5 ppm (s, 4F; CF2); IR (gas phase): n˜ =1330 (m), 1310 (s),
1229 (vs), 1131 (s), 961 (m), 747 (m), 673 (w), 615 (vw), 588 (vw),
540 cmÀ1 (vw); MS (EI, 70 eV, pos.): m/z (%): 351 (19) [Ge(C2F5)Br2+],
Acknowledgements
This work was supported by Merck KGaA (Darmstadt, Ger-
many). Solvay (Hannover, Germany) is gratefully acknowledged
for donation of pentafluoroethane (Solkane 125). We also ac-
knowledge support by the Deutsche Forschungsgemeinschaft
(Core Facility GED@BI, Mi477/21-1). We thank Prof. Lothar
Weber and Dr. Julia Bader for helpful discussions, Dr. Simon
Steinhauer for the preparation of the capillaries with
(C2F5)2GeBr2 and (C2F5)2GeH2 as well as Annika Schrçder for
help in the laboratory.
291 (2) [Ge(C2F5)BrF+], 251 (42) [GeBr2F+], 232 (3) [GeBr2+], 191 (4)
+
[GeBrF2+], 153 (16) [GeBr+], 119 (12) [C2F5 ], 100 (100) [C2F4 +], 93
C
(15) [GeF+], 69 (21) [CF3+].
Synthesis of bis(pentafluoroethyl)dichlorogermane: In a 750 mL
glass ampoule equipped with a Young valve HCl (10.7 mmol) was
condensed onto (C2F5)2GePh2 (1.63 g, 3.51 mmol) and AlCl3 (0.06 g,
0.5 mmol). The reaction mixture was stirred for 18 h at 708C. After
fractional condensation (À788C, À1968C) a mixture of (C2F5)2GeCl2
and benzene in a ratio of 1:2 was obtained. 13C{19F} NMR (n-pent-
ane/[D6]acetone, 238C): d=118.9 (s; CF2), 117.9 ppm (s; CF3);
19F NMR (n-pentane/[D6]acetone, 238C): d=À81.1 (s, 6F; CF3),
À118.2 ppm (s, 4F; CF2); IR (gas phase): n˜ =3100 (w)*, 3047 (w)*,
1965 (w)*, 1804 (w)*, 1483 (w)*, 1333 (w), 1312 (m), 1230 (s), 1134
(s), 1037 (w)*, 965 (m), 748 (w), 673 (s)*, 464 (w), 441 cmÀ1 (w)
(*benzene); MS (EI, 70 eV, pos.): m/z (%): 347 (1) [Ge(C2F5)2Cl+], 307
(1), 263 (14) [Ge(C2F5)Cl2+], 247 (4) [Ge(C2F5)ClF+], 207 (2), 163 (48)
Keywords: fluorine
·
germane
·
Lewis
acids
·
pentafluoroethyl · trigermoxane
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[GeCl2F+], 147 (5) [GeClF2+], 135 (10), 119 (15) [C2F5+], 109 (14)
+
[GeCl ], 100 (100) [C2F4 +], 97 (14) [C2ClF2+], 93 (13) [GeF+].
C
Synthesis of bis(pentafluoroethyl)germane: A mixture of Bu3SnH
(0.93 mL, 3.5 mmol) and (C2F5)2GeBr2 (0.76 g, 1.6 mmol) was stirred
for 18 h at room temperature. The product was condensed off and
collected as a colourless liquid (0.34 g, 1.1 mmol, 68%). 1H NMR
(CDCl3, 238C): d=5.18 ppm (quin sept, 3J(F,H)=10.2, 4J(F,H)=1.9,
2H); 13C{19F} NMR (neat/[D6]acetone, 208C): d=119.2 (s; CF2),
3
119.1 ppm (t, J(C,H)=10.6; CF3); 19F NMR (CDCl3, 238C) d=À83.6
(t, 4J(F,H)=1.9, 6F; CF3), À116.9 ppm (t, 3J(F,H)=10.2, 4F; CF2); IR
(gas phase): n˜ =2160 (w), 2143 (w), 1338 (m), 1316 (m), 1223 (s),
1140 (m), 1103 (m), 697 (m), 846 (w), 745 (w), 724 (m), 597 cmÀ1
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(w); MS (EI, 70 eV, pos.): m/z (%): 213 (4) [Ge(C2F5)HF+], 195 (8)
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+
[Ge(C2F5)H2+], 119 (5) [C2F5+], 113 (20) [GeHF2 ], 100 (100) [C2F4 +],
C
93 (46) [GeF+], 69 (15) [CF3+], 51 (6).
Synthesis of hexakis(pentafluoroethyl)trigermoxane: In a glass
flask equipped with a Young valve, (C2F5)2GeBr2 (0.91 g, 1.9 mmol)
was treated with Ag2CO3 (0.69 g, 2.5 mmol) at 110 8C for 4 days.
The formed product was sublimed at 508C to afford colourless
crystals (0.53 g, 0.54 mmol; 84%). 13C{19F} NMR (Et2O/[D6]acetone,
238C): d=118.8 (s; CF2), 118.0 ppm (s; CF3); 19F NMR (Et2O/
[13] G. M. Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112–122.
Received: December 18, 2015
Published online on February 16, 2016
Chem. Eur. J. 2016, 22, 4758 – 4763
www.chemeurj.org
4763
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