Preparation of Discrete Branched Oligogermanes
Organometallics, Vol. 27, No. 9, 2008 1983
5.85 (s, 1H, Ge-H) ppm. 13C NMR (C6D6, 25 °C) δ 136.5 (ipso-
C), 128.8 (o-C), 128.6 (p-C), 127.5 (m-C) ppm. IR (Nujol mull)
1953 cm-1 (υ Ge–H). Anal. Calcd for C54H46Ge4: C, 65.83; H,
4.71. Found: C, 65.27; H, 4.62.
and 8a-c therefore appear to have varying contributions to the
overall relative energies of the σ and σ* orbitals in these
systems. The preparation of 8a–c from compound 4 suggests
that these compounds and related derivatives can thus serve as
useful building blocks for the rational construction of higher
branched oligomers and also possibly dendridic structures.
Preparative-Scale Synthesis of HGe(GePh3)3 (3). To a solution
of 1 (0.200 g, 0.188 mmol) in CH2Cl2 (1.1 mL) was added triflic
acid (0.017 mL, 0.029 g, 0.19 mmol) under a stream of N2. The
reaction mixture was sealed in a Schlenk tube and stirred for 4 h.
The volatiles were removed in vacuo with use of a water bath to
yield a white solid. The 19F NMR in benzene-d6 exhibited a single
line at δ –77.7 ppm. The solid product was dissolved in Et2O (10
mL) and treated with LiAlH4 (0.0080 g, 0.21 mmol) in Et2O (5
mL). The reaction mixture was stirred for 18 h at 25 °C and the
solvent was removed in vacuo to yield 0.171 g (92%) of 3 as a
white solid. The spectral attributes of the product were identical
with those described above.
Experimental Section
All manipulations were carried out under an inert N2 atmosphere
with standard Schlenk, syringe, and glovebox techniques.46 All
nondeuterated solvents were purchased from Aldrich and were
purified with use of a Glass Contour solvent purification system.
The germanes R2Ge(NMe2)CH2CH2OEt (5a: R ) Bu; 5b: R ) Et;
5c: R ) Ph) were prepared according to a published procedure28
and PhGeH3 was prepared by reaction of PhGeCl3 (Gelest, Inc.)
with LiAlH4.47 NMR spectra were recorded on a Varian Gemini
2000 spectrometer operating at 300.0 MHz (1H), 282.3 (19F), or
75.5 MHz (13C). The 19F NMR spectra were referenced to C6H5CF3
set at δ –63.72 ppm while 1H and 13C NMR spectra were referenced
to the C6D6 solvent. UV/visible spectra were recorded on a Hewlett-
Packard Agilent UV/visible spectroscopy system. Elemental analy-
ses were conducted by Midwest Microlab, LLC (Indianapolis, IN).
Synthesis of PhGe(GePh3)3 (1). To a solution of PhGeH3 (0.191
g, 1.25 mmol) in acetonitrile (10 mL) was added a solution of
Synthesis of PhGe(GeBu2CH2CH2OEt)3 (4). To a solution of
PhGeH3 (0.200 g, 1.31 mmol) in CH3CN (10 mL) was added a
solution of Bu2Ge(NMe2)CH2CH2OEt (5a)28 (1.195 g, 3.932 mmol)
in CH3CN (30 mL). The reaction mixture was sealed in a Schlenk
tube and heated at 85 °C for 72 h. The volatiles were removed in
vacuo to yield a viscous yellow oil. The crude product was distilled
in a Kugelrohr oven (180 °C, 0.050 torr) to furnish 4 (1.163 g,
95%) as a colorless viscous oil. 1H NMR (C6D6, 25 °C) δ 7.66 (d,
J ) 6.3 Hz, 2H, o-C6H5), 7.18–7.08 (m, 3H, m-C6H5 and p-C6H5),
3.59 (t, J ) 7.2 Hz, 6H, GeCH2CH2O-), 3.31 (q, J ) 7.2 Hz, 6H,
-OCH2CH3), 1.55–1.32 (m, 36H, -CH2CH2CH2CH3), 1.14
(t, J ) 7.2 Hz, 18H, -CH2CH2CH2CH3), 0.96 (t, J )
7.2 Hz, 6H, GeCH2CH2O-), 0.91 (t, J ) 7.2 Hz, 9H, -OCH2CH3)
ppm. 13C NMR (C6D6, 25 °C) δ 138.4 (ipso-C6H5), 136.1
(o-C6H5), 128.4 (p-C6H5), 127.6 (m-C6H5), 68.8 (-OCH2CH3), 65.7
(-GeCH2CH2-), 28.8 (GeCH2CH2CH2CH3), 27.1 (GeCH2CH2O-),
26.9 (GeCH2CH2CH2CH3), 16.8 (GeCH2CH2CH2CH3), 16.0
(-OCH2CH3), 13.8 (GeCH2CH2CH2CH3) ppm. Anal. Calcd for
C42H86Ge4O3: C, 54,27; H, 9.33. Found: C, 53.79; H, 9.88.
Synthesis of PhGe(GeBu2GeBu2CH2CH2OEt)3 (8a). To a
solution of 4 (0.280 g, 0.301 mmol) in benzene (25 mL) was
added a 1.0 M solution of DIBAL-H in hexanes (0.903 mL,
0.903 mmol). The reaction mixture was refluxed for 24 h and the
volatiles were removed in vacuo to yield a thick oil that was
dissolved in CH3CN (25 mL). The resulting solution was treated
with Bu2Ge(NMe2)CH2CH2OEt (5a)28 (0.275 g, 0.905 mmol) in
CH3CN (10 mL) and the reaction mixture was sealed in a
Schlenk tube and heated at 85 °C for 48 h. The volatiles were
removed in vacuo to yield a thick yellow oil that was eluted
through a 1.5 in. × 1.5 in. silica gel column with 40 mL of a
1:20 (v/v) mixture of Et2O:hexane as the eluent. The volatiles
were removed from the eluent in vacuo to furnish 8a (0.193 g,
48
Ph3GeNMe2 (1.31 g, 3.76 mmol) in acetonitrile (20 mL). The
reaction mixture was sealed in a Schlenk tube and then heated in
an oil bath at 85 °C for 48 h. The reaction mixture was allowed to
cool and the solvent was removed in vacuo. Distillation of the crude
product mixture (135 °C, 0.01 torr) yielded 1.131 g (85%) of 1 as
colorless crystals (mp 264 °C). 1H NMR (C6D6, 25 °C) δ 7.66
(d, J ) 7.5 Hz, 2H, o-H ((C6H5)3Ge)3Ge(C6H5)), 7.26 (d, J ) 7.5
Hz, 18H, o-H ((C6H5)3Ge)3Ge(C6H5)), 7.07 (m, 3H, m-H and
p-H (C6H5)3Ge)3Ge(C6H5)), 6.94 (m, 27H, m-H and p-H
(C6H5)3Ge)3Ge(C6H5)) ppm. 13C NMR (C6D6, 25 °C) δ 138.9 (ipso-
((C6H5)3Ge)3Ge(C6H5)), 138.6 (ipso-((C6H5)3Ge)3Ge(C6H5)), 136.6
(o-((C6H5)3Ge)3Ge(C6H5)), 134.9 (o-((C6H5)3Ge)3Ge(C6H5)), 128.9
(p-((C6H5)3Ge)3Ge(C6H5)), 128.6 (p-((C6H5)3Ge)3Ge(C6H5)), 128.5
(m-((C6H5)3Ge)3Ge(C6H5)), 128.2 (m-((C6H5)3Ge)3Ge(C6H5)) ppm.
UV/vis (CH2Cl2): λmax 256 nm (ꢀ ) 5.1 × 104 L mol-1 cm-1).
Anal. Calcd. for C60H50Ge4: C, 67.90; H, 4.75. Found: C, 67.43;
H, 4.69.
Small-Scale Synthesis of (F3CO2SO)Ge(GePh3)3 (2). To a
solution of (Ph3Ge)3GePh (1) (0.090 g, 0.085 mmol) in CDCl3 (0.5
mL) in a screw-cap NMR tube was added neat triflic acid (7.4 µL,
0.013 g, 0.084 mmol) with a micropipetter. The reaction mixture
was kept at room temperature for 4 h, after which time the 19F
NMR spectrum of the solution exhibited a single resonance at δ
-77.7 ppm indicating complete consumption of HOSO2CF3 and
formation of (F3CO2SO)Ge(GePh3)3 (2). The solution was trans-
ferred to a conical flask and the volatiles were removed in vacuo
to yield 0.082 g (80%) of 2 as a white solid. IR (Nujol mull) 1305
(s, υas(SO3)), 1261 (m, υas(SO3)), 1237 (s), 1200 (s, υs(CF3)), 1150
1
43%) as a colorless oil. H NMR (C6D6, 25 °C) δ 7.73 (d, J )
7.5 Hz, 2H, o-C6H5), 7.28–7.17 (m, 3H, m-C6H5 and p-C6H5),
3.67 (t, J ) 7.8 Hz, 6H, GeCH2CH2O-), 3.41 (q, J ) 6.8 Hz,
6H, -OCH2CH3), 1.62–1.12 (m, 78 H, GeCH2CH2CH2CH3 and
GeCH2CH2O-), 1.03–0.97 (m, 45 H, GeCH2CH2CH2CH3 and
–OCH2CH3) ppm. 13C NMR (C6D6, 25 °C) δ 139.2 (ipso-C6H5),
136.2 (o-C6H5), 128.4 (p-C6H5), 128.2 (m-C6H5), 68.9 (-OCH2CH3),
65.8 (-GeCH2CH2-), 29.0 (GeCH2CH2CH2CH3), 28.8 (GeCH2-
CH2CH2CH3), 27.3 (GeCH2CH2O-), 27.1 (GeCH2CH2CH2CH3),
26.9 (GeCH2CH2CH2CH3), 16.0 (GeCH2CH2CH2CH3), 15.7
(GeCH2CH2CH2CH3), 14.8 (-OCH2CH3), 13.9 (GeCH2CH2-
CH2CH3 and GeCH2CH2CH2CH3) ppm. Anal. Calcd for
C66H140Ge7O3: C, 53.20; H, 9.47. Found: C, 53.52; H, 9.54.
Synthesis of PhGe(GeBu2GeEt2CH2CH2OEt)3 (8b). To a
solution of 4 (0.370 g, 0.398 mmol) in benzene (20 mL) was added
a 1.0 M solution of DIBAL-H in hexanes (1.19 mL, 1.19 mmol).
The reaction mixture was heated at reflux for 24 h and the volatiles
were removed in vacuo to yield a thick oil that was dissolved in
CH3CN (30 mL). The resulting solution was treated with
(s, υas(CF3)), 1094 (s), 1024 (m), 998 (m), 937 (s, υs(SO3)) cm-1
.
Small-Scale Synthesis of HGe(GePh3)3 (3). The sample of
compound 2 was dissolved in Et2O (5 mL) and treated with a
solution of LiAlH4 (0.0039 g, 0.10 mmol) in Et2O (5 mL). The
solution was stirred for 4 h at room temperature and the volatiles
were removed in vacuo. The crude product mixture was dissolved
in benzene (5 mL) and filtered through Celite. The Celite pad was
washed with benzene (3 × 2 mL) and the solvent was removed in
vacuo to yield 3 (0.054 g, 64% based on 1) as a white solid
(mp 210 °C). 1H NMR (C6D6, 25 °C) δ 7.26 (d, J ) 8.1 Hz, 18H,
o-H ((C6H5)3Ge)3Ge(C6H5)), 7.15–6.92 (m, 27H, m-H and p-H),
(47) Meyer, J. M.; Allred, A. L. J. Phys. Chem. 1968, 72, 3043–3045.
(48) Rivière, P.; Rivière-Baudet, M.; Couret, C.; Satgé, J. Synth. React.
Inorg. Met. Org. Chem. 1974, 4, 295–307.