Study on the electronic effect on coordinating donors in heptacoordinate trichlorogermanes

Article abstract of DOI:10.1016/j.tet.2007.08.001

Trichloro[tris(2,5-dimethoxyphenyl)methyl]germane (1a), trichloro[tris(3-fluoro-6-methoxyphenyl)methyl]germane (1b), and trichloro[tris(2-methoxy-5-trifluoromethylphenyl)methyl]germane (1c) were synthesized. X-ray crystallographic analyses of 1a-c revealed their heptacoordinate geometries around the germanium atoms. The interatomic distances between the oxygen atoms and the central germanium atoms in the crystalline state were not significantly affected by change of functional groups on the benzene rings, while the optimized structures by theoretical calculations and Atoms in Molecules (AIM) analysis indicated linear relationship between the donating ability of functional groups and the O?Ge interatomic interactions.

Full text of DOI:10.1016/j.tet.2007.08.001

Tetrahedron 63 (2007) 10127–10132
Study on the electronic effect on coordinating donors in
heptacoordinate trichlorogermanes
*
Kohei Iwanaga, Junji Kobayashi and Takayuki Kawashima
Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Received 11 June 2007; revised 31 July 2007; accepted 1 August 2007
Available online 3 August 2007
Abstract—Trichloro[tris(2,5-dimethoxyphenyl)methyl]germane (1a), trichloro[tris(3-fluoro-6-methoxyphenyl)methyl]germane (1b), and
trichloro[tris(2-methoxy-5-trifluoromethylphenyl)methyl]germane (1c) were synthesized. X-ray crystallographic analyses of 1a–c revealed
their heptacoordinate geometries around the germanium atoms. The interatomic distances between the oxygen atoms and the central germa-
nium atoms in the crystalline state were not significantly affected by change of functional groups on the benzene rings, while the optimized
structures by theoretical calculations and Atoms in Molecules (AIM) analysis indicated linear relationship between the donating ability of
functional groups and the O/Ge interatomic interactions.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
groups as coordinating sites.5 X-ray structural analyses
and NMR spectroscopy showed the presence of heptacoordi-
nate structures both in the solid state and in solution, with
three interatomic interactions between the oxygen atoms
and the central germanium atom. Systematic comparisons
of these interatomic interactions were performed and it
was found that the Lewis acidity of the germanium atom
controls the strength of the interatomic interactions.
Hypercoordinate main group element compounds are well
studied because of their interesting structures and reactiv-
ities and also as models of the transition state or the inter-
mediate of SN2 type reaction.1 Among group 14 element
compounds, penta- and hexacoordinate silicon compounds
have been intensively and widely studied from a viewpoint
of usefulness of their synthetic applications,2 while germa-
nium and tin derivatives are rather less studied.3 In contrast
to penta- and hexacoordinate compounds, heptacoordinate
compounds are much rare. Although there have been several
reports of the synthesis of neutral heptacoordinate com-
pounds with four covalent bonds and three dative bonds,
the systematic comparisons of these structural properties
have been scant so far.4
In this type of heptacoordinate compounds, the interaction
between the central atom and the donor sites can be con-
trolled not only by altering the central atoms or the halogen
atoms attached to the central atom, but also by tuning the
electron-donating ability of oxygen atoms. From this point
of view, we report here the synthesis of trichlorogermanes
1a–c, which have a different functional group at para-
positions against coordinating methoxy groups on benzene
rings, and the comparison of the X-ray structures of the
compounds.
Recently, we have developed heptacoordinate trihaloger-
manes 1d–g (Fig. 1) by taking advantage of a triaryl-
methyl-type tetradentate ligand bearing three methoxy
2. Results and discussion
2.1. Syntheses
o-Bromoanisoles 4a–c were synthesized by the reported
methods. Triarylmethanes 6a–c were synthesized in similar
ways to that previously reported for triarylmethane 6d,5 but
some of the reaction conditions and reagents must be modi-
fied (Scheme 1). Triarylmethanols 5a and 5d were reduced
easily with ethanol in hydrochloric acid. However, triaryl-
methanols 5b and 5c with fluorine atoms and trifluoromethyl
groups, respectively, were not reduced to the corresponding
Figure 1. Heptacoordinate trihalogermanes.
* Corresponding author. Tel.: +81 3 5841 4338; fax: +81 3 5800 6899;
e-mail: takayuki@chem.s.u-tokyo.ac.jp
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.08.001

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K. Iwanaga et al. / Tetrahedron 63 (2007) 10127–10132
Scheme 1. Synthetic route of heptacoordinate trichlorogermanes 1a–d.
triarylmethanes 6b and 6c under the same conditions, due to
destabilization of intermediary carbocation by the electron
withdrawing effect of fluorine atom or trifluoromethyl
group. Even the reaction with triethylsilane in acetic acid
gave the corresponding triarylmethanes 6b and 6c only in
the low conversion yields. However, addition of 1.1 equiv
of trifluoroacetic acid accelerated the reaction to give 6b
or 6c in a good yield. The deprotonations of triarylmethanes
6a–c were achieved by treatment with n-butyllithium in
a similar way to that for 6d. But, the reaction time in the
cases of 6b and 6c, was remarkably reduced (6–7 h) com-
pared with 12 h in the case of 6d, due to the stabilization
of formed carbanion by electron withdrawing substituents
at the meta-positions. The side-product, in which n-butyl
groups were introduced on the benzene rings, was formed
in the case of the reaction of 6b, presumably via the benzyne
intermediate. Target compounds 1a–c were obtained by
subsequent treatment of in situ generated carbanions with
tetrachlorogermane in low to moderate yields.
compounds have approximate C3 symmetrical propeller-like
structures, as had been found in the previously reported tri-
chlorogermane 1d.5 The oxygen atoms adopt backside posi-
tions to the halogen atoms (O/Ge–Cl angles are 170–178ꢀ),
and the three aryl rings have the same twist angles out of their
common coordination plane with the germanium atom.
The each O/Ge interatomic distance of trichlorogermanes
1a–c showed no significant difference among 1a–c (Table 1).
This result shows sharp contrast to the systematic difference
of the O/Ge distances of 1d–g, when changing halogen
atoms on the central germanium atom. Torsion angles
Ge–C1–C2–C3 were also converged within the standard
deviations.
2.3. Theoretical calculations
For the detailed investigation, Atoms in Molecules (AIM)
analyses of 1a–c and a model compound 1h (R¼H)
were performed at the B3PW91/6-31+G(d)[Cl,Ge,O]:6-
31G(d)[C,F,H] level (Table 2)6,7. The X-ray structures are
well reproduced by theoretical calculations, and bond criti-
cal points were found on the bond paths between the oxygen
atoms and the germanium atom in their optimized structures,
indicating the existence of bonding interaction between
oxygen and germanium atoms. These interactions showed
a systematic tendency between functional group (R) and
O/Ge distances, as well as electron densities on the bond
2.2. Structures
Single crystals of 1a–c suitable for X-ray analyses were ob-
tained in each case by slow evaporation from acetonitrile/
hexane solution for 1a, benzene/CHCl3 solution for 1b and
CHCl3 solution for 1c, respectively. The crystal structures
of 1a–c were determined by X-ray crystallographic analyses,
and the ORTEP drawings are shown in Figure 2. All the
Figure 2. ORTEP drawings of trihalogermanes (a) 1a, (b) 1b, and (c) 1c (50% probability level).

K. Iwanaga et al. / Tetrahedron 63 (2007) 10127–10132
10129
Table 1. Selected interatomic distances and torsion angles in 1a–ga
an argon atmosphere unless otherwise noted. Solvents
were purified by MBRAUN MB-SPS system. Wet column
chromatography (WCC) was performed using Kanto Silica
Gel 60 N. Gel permeation liquid chromatography (GPLC)
was performed using LC-918 or LC-908 with JAIGEL
1H+2H columns (Japan Analytical Industry) using chloro-
form or toluene as solvents, respectively. NMR spectra
were recorded by a JEOL AL-400 spectrometer (1H,
400 MHz; 13C, 100 MHz; 19F, 396 MHz) and a Bruker
DRX-500 spectrometer (1H, 500 MHz; 13C, 126 MHz).
Chemical shifts are reported in d. 1H NMR spectra are refer-
enced to residual protons in deuterated solvent; 13C NMR
spectra are referenced to carbon-13 in the deuterated sol-
vent; 19F NMR spectra are referenced to an external standard
of CFCl3. High resolution mass spectra were recorded by
a JEOL JMS-700P using PEG400, PEG600, or UltramarkÒ
as internal standards. All melting points were measured
with Yanaco MP-S3 and uncorrected. Elemental analyses
were performed by the Microanalytical Laboratory of De-
partment of Chemistry, Faculty of Science, The University
of Tokyo.
˚
R
X
Ge/O/A
Ge–C1–C2–C3/ꢀ
1a
1b
1bb
1c
1d
1e
1f
OMe
F
F
CF3
t-Bu
t-Bu
t-Bu
t-Bu
Cl
Cl
Cl
Cl
Cl
F
2.769(2)
2.793(4)
2.760(4)
2.781(2)
2.768(5)
2.621(4)
2.821(3)
2.853(5)
50.9(2)
53.2(5)
54.3(5)
52.5(3)
51.5(7)
47.8(2)
55.3(4)
54.7(6)
Br
I
1g
a
Values are the average of the symmetric parts of the compounds.
There were two independent structures in the unit cell.
b
Table 2. AIM analyses of 1a–c and 1h
˚
R
Ge/O/A
Ge–C–C–C/ꢀ
ra/e aꢁ0 3
V2rb/e aꢁ0 5
4.1.1. 2-Bromo-1,4-dimethoxybenzene 4a.8 In the open at-
mosphere, to a solution of 1,4-dimethoxybenzene 3a (16.8 g,
121 mmol) in AcOH (170 mL) was added a solution of bro-
mine (6.7 mL, 130 mmol) in AcOH (90 mL) by dropwise at
room temperature. After stirring for 1 h, H2O (100 mL) was
added to the reaction mixture. After stirring for another 1 h,
the organic layer was extracted with CHCl3. The extracts
were combined and dried over anhydrous MgSO4, and
then the solvent was removed under reduced pressure. The
residue was distilled in vacuo (105 ꢀC at 1 mmHg) to afford
1a
1h
1b
1c
OMe
H
F
CF3
2.778
2.785
2.790
2.812
51.28
51.27
51.55
52.26
0.01921
0.01897
0.01883
0.01801
0.0490
0.0486
0.0482
0.0470
a
Electron density at the bond critical points.
Laplacian value of electron density.
b
critical points, that is, electron withdrawing groups (F, CF3)
weaken the electronic interactions at the bond critical points
presumably due to decrease in the electron density of
methoxy groups, while electron-donating methoxy groups en-
hance the electronic interaction. These results indicate that
altering functional groups on benzene rings affects the inter-
atomic interactions. However, these effects are too small to
be observed in crystalline state because of other factors
like packing effect will also affect the molecular structures.
1
4a (19.3 g, 73%). Compound 4a: brown liquid. H NMR
(400 MHz, 27 ꢀC) d 3.78 (s, 3H), 3.84 (s, 3H), 6.81–6.83
(m, 2H), 7.12 (d, 1H, J¼2.4 Hz).
4.1.2. Tris(2,5-dimethoxyphenyl)methane 6a. To Mg turn-
ings (3.25 g, 134 mmol) was added a solution of 4a (19.3 g,
89.0 mmol) in THF (50 mL) and the reaction mixture was
refluxed for 4 h. To the reaction mixture was added a solution
of diethyl carbonate (3.6 mL, 30 mmol) in THF (10 mL) and
the reaction mixture was refluxed overnight. The reaction
mixture was treated with EtOH (30 mL) and solvent was re-
moved in vacuo. To the residue, EtOH (200 mL) and aq HCl
(30 mL) were added and heated at 60 ꢀC for 3.5 h. The reac-
tion mixture was concentrated to 100 mL in vacuo, and neu-
tralized with aq NaOH, and extracted with CHCl3. The
extracts were combined and dried over anhydrous MgSO4,
and then the solvent was removed under reduced pressure.
The residue was subjected to column chromatography on
silica gel. Elution with CHCl3 gave 6a, which was further
purified by washing with EtOH to afford pure product
(4.67 g, 37%). Compound 6a: white crystal, mp 157.3–
3. Conclusion
In conclusion, we reported the synthesis, structures, and
theoretical calculations of trichlorogermanes with various
functional groups on their benzene rings. While all the tri-
chlorogermanes had heptacoordinate geometries, the signif-
icant differences of the interatomic distances between
oxygen atoms and germanium atoms were not observed in
the crystalline state. However, the theoretical calculations
suggest the existence of the bonding interactions and the
relationship between functional groups and the strength of
theinteractions. Theseresultsindicatethattheelectroniceffect
on the donating oxygen atom caused by electron-donating
ability of the functional groups at its para-position may be
too small to detect those differences in the crystalline state.
1
157.7 ꢀC (dec). H NMR (500 MHz, CDCl3, 27 ꢀC) d 3.63
(s, 9H), 3.64 (s, 9H), 6.33 (s, 1H), 6.38 (d, 3H, J¼3.1 Hz),
6.67 (dd, 3H, J¼3.1, 8.8 Hz), 6.76 (d, 3H, J¼8.8 Hz); 13C
NMR (126 MHz, CDCl3, 27 ꢀC) d 37.4 (d), 55.4 (q), 56.6
(q), 110.3 (d), 111.9 (d), 116.9 (d), 133.7 (s), 151.7 (s),
153.2 (s). Anal. Calcd for C25H28O6: C, 70.74; H, 6.65.
Found: C, 70.58; H, 6.78.
4. Experimental
4.1. General
General chemicals were used as received. All manipulations
were carried out using modified Schlenk technique under
4.1.3. Trichloro[tris(2,5-dimethoxyphenyl)methyl]ger-
mane 1a. To a solution of 6a (1.50 g, 3.53 mmol) in benzene

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K. Iwanaga et al. / Tetrahedron 63 (2007) 10127–10132
(50 mL) was added n-BuLi (1.67 M hexane solution,
17.7 mmol) at 50 ꢀC. The reaction mixture was stirred at
50 ꢀC for 8 h. After removal of the solvent under reduced
pressure, DME (25 mL) and HMPA (2.50 mL, 14.4 mmol)
were added to the residue. To the mixture was added tetra-
chlorogermane (4.05 mL, 35.3 mmol) at 0 ꢀC. The reaction
mixture was stirred at 0 ꢀC for 2 h and at room temperature
overnight. After removal of the solvent, the residue was
treated with 30 mL of EtOH and then 20 mL of H2O. The or-
ganic layer was extracted with CHCl3. After removal of the
solvent under reduced pressure, the residue was dissolved in
ether, and insoluble solids were filtered off. The filtrate was
washed with 2% aq NaOH, and the organic layer was dried
over anhydrous MgSO4, and the solvent was removed under
reduced pressure. The residue was subjected to GPLC to
afford 1a (265 mg, 37%). Compound 1a: colorless crystal,
4.1.6. Tris(3-fluoro-6-methoxyphenyl)methane 6b. To the
solution of 5b (1.26 g, 3.12 mmol) in AcOH (15 mL) with
CF3COOH (0.27 mL, 3.52 mmol) was added Et3SiH
(6.5 mL, 40.7 mmol) and the solution was stirred at 90 ꢀC
for 14 h, and then 100 ꢀC overnight. H2O (30 mL) was added
to the reaction mixture and white precipitate was collected
by filtration. The precipitate was subjected to column chro-
matography on silica gel. Elution with hexane/CHCl3¼1:4
to afford 6b (772 mg, 64%). Compound 6b: white crystal,
1
mp 183.1–183.3 ꢀC. H NMR (500 MHz, CDCl3, 27 ꢀC)
4
d 3.66 (s, 9H), 6.26 (s, 1H), 6.44 (dd, 3H, JHH¼3.1 Hz,
3
4
3JHF¼9.5 Hz), 6.78 (dd, 3H, JHH¼8.9 Hz, JHF¼4.6 Hz),
3
4
3
6.88 (ddd, 3H, JHH¼8.9 Hz, JHH¼3.1 Hz, JHF¼8.9 Hz);
13C NMR (126 MHz, CDCl3, 27 ꢀC) d 37.6 (d), 56.3 (q),
3
2
111.7 (dd, JCF¼8 Hz), 113.3 (dd, JCF¼23 Hz), 116.3
2
3
(dd, JCF¼24 Hz), 133.1 (d, JCF¼7 Hz), 153.3 (s), 156.9
1
1
19
mp 230.8–231.1 ꢀC. H NMR (500 MHz, CDCl3, 27 ꢀC)
(d, JCF¼238 Hz); F NMR (376 MHz, CDCl3, 27 ꢀC)
d 7.11–7.16 (m). Anal. Calcd for C22H19F3O3: C, 68.04;
H, 4.93. Found: C, 67.80; H, 5.12.
d 3.60 (s, 9H), 3.65 (s, 9H), 6.03 (d, 3H, J¼2.9 Hz), 6.82
(d, 3H, J¼8.8 Hz), 6.87 (dd, 3H, J¼2.9, 8.8 Hz); 13C
NMR (126 MHz, CDCl3, 27 ꢀC) d 54.2 (q), 55.5 (q), 67.9
(s), 110.2 (d), 112.9 (d), 117.3 (d), 127.8 (s), 150.8 (s),
153.5 (s). Anal. Calcd for C25H27Cl3GeO6: C, 49.84; H,
4.52. Found: C, 49.69; H, 4.55.
4.1.7. Trichloro[tris(3-fluoro-6-methoxyphenyl)methyl]-
germane 1b. To a solution of 6b (1.00 g, 2.57 mmol) in
benzene (30 mL) was added n-BuLi (1.67 M hexane solu-
tion, 13 mmol) at 50 ꢀC. The reaction mixture was stirred
at 50 ꢀC for 7 h. After removal of the solvent under reduced
pressure, DME (15 mL) and HMPA (1.80 mL, 10.0 mmol)
were added to the residue. To the reaction mixture was
added tetrachlorogermane (3.0 mL, 26 mmol) at 0 ꢀC.
The reaction mixture was stirred at 0 ꢀC for 2 h and at
room temperature overnight. After removal of the solvent,
the residue was treated with 20 mL of EtOH and then
10 mL of H2O. The organic layer was extracted with
CHCl3. After removal of the solvent under reduced pres-
sure, the residue was dissolved in ether, and insoluble
solids were filtered off. The filtrate was washed with 2%
aq NaOH, and the organic layer was dried over anhydrous
MgSO4, and the solvent was removed under reduced pres-
sure. The residue was subjected to GPLC to afford 1b
(293 mg, 60%). Compound 1b: colorless crystal, mp
4.1.4. 2-Bromo-4-fluoroanisole 4b.9 In the open atmo-
sphere, to a solution of 4-fluoroanisole 3b (16.8 g,
121 mmol) in CH2Cl2 (100 mL) was added a solution of bro-
mine (12 mL, 230 mmol) in AcOH (100 mL) dropwise at
room temperature. After the solution was stirred overnight,
aq Na2SO3 (100 mL) was added. The organic layer was ex-
tracted with CHCl3. The extracts were combined and dried
over anhydrous MgSO4, and then the solvent was removed
under reduced pressure. The residue was distilled in vacuo
(70 ꢀC at 1 mmHg) to afford 4b (36.0 g, 88%). Compound
1
4b: colorless liquid. H NMR (400 MHz, 27 ꢀC) d 3.86 (s,
3
4
3H), 6.83 (dd, 1H, JHH¼9.2 Hz, JHF¼4.8 Hz), 6.99 (ddd,
3
4
3
1H, JHH¼9.2 Hz, JHH¼2.8 Hz, JHF¼8.0 Hz), 7.29 (dd,
4JHH¼2.8 Hz, JHF¼8.0 Hz); F NMR (376 MHz, 27 ꢀC)
3
19
d 8.72.
1
241.4–241.9 ꢀC (dec). H NMR (500 MHz, CDCl3, 27 ꢀC)
4
3
4.1.5. Tris(3-fluoro-6-methoxyphenyl)methanol 5b. To
Mg turnings (3.25 g, 134 mmol) was added a solution of
4b (18.0 g, 87.8 mmol) in THF (50 mL) and the reaction
mixture was refluxed for 4 h. To the reaction mixture was
added a solution of diethyl carbonate (2.6 mL, 22 mmol)
in THF (10 mL) and the reaction mixture was refluxed over-
night. The reaction mixture was treated with EtOH (30 mL)
and then H2O (20 mL). The organic layer was extracted with
CHCl3. The extracts were combined and dried over anhy-
drous MgSO4, and then the solvent was removed under
reduced pressure. The residue was purified by reprecipita-
tion from hexane/CHCl3 to afford 5b (2.23 g, 24%). Com-
pound 5b: white crystal, mp 160.5–161.0 ꢀC (dec). 1H
NMR (500 MHz, CDCl3, 27 ꢀC) d 3.48 (s, 9H), 5.47 (s,
d 3.68 (s, 9H), 6.16 (dd, 3H, JHH¼3.0 Hz, JHF¼9.9 Hz),
3
4
6.88 (dd, 3H, JHH¼8.9 Hz, JHF¼4.4 Hz), 7.08 (ddd, 3H,
4
3
3JHH¼8.9 Hz, JHH¼3.0 Hz, JHF¼9.9 Hz); 13C NMR
(126 MHz, CDCl3, 27 ꢀC) d 54.4 (q), 66.7 (s), 111.0 (dd,
3JCF¼8 Hz), 115.9 (dd, JCF¼24 Hz), 116.9 (dd, JCF
¼
2
2
24 Hz), 127.5 (d, 3JCF¼8 Hz), 157.2 (d, 1JCF¼239 Hz); 19
F
NMR (376 MHz, CDCl3, 27 ꢀC) d 8.01–8.08 (m). Anal.
Calcd for C22H18Cl3F3GeO3: C, 46.65; H, 3.20. Found: C,
46.47; H, 3.39.
4.1.8. 4-Trifluoromethylanisole 3c.10 In the open atmo-
sphere, to a solution of 4-fluorophenol 2c (5 g, 30 mmol)
and potassium carbonate (4.30 g, 30.1 mmol) in acetone
(50 mL) was added iodomethane (4.29 mL, 46.3 mmol)
and the mixture was refluxed for 1 day. After the solvent
was removed under reduced pressure, H2O (50 mL) was
added and the mixture was extracted from AcOEt. The ex-
tracts were combined and dried over anhydrous MgSO4,
and then the solvent was removed under reduced pressure
to afford 3c (4.79 g, 88%). The product was used without
3
4
1H), 6.81 (dd, 3H, JHH¼8.8 Hz, JHF¼4.6 Hz), 6.91 (dd,
4
3
3
3H, JHH¼3.0 Hz, JHF¼10.3 Hz), 6.95 (ddd, 3H, JHH
¼
8.8 Hz, 4JHH¼3.0 Hz, 3JHF¼10.3 Hz); 13C NMR (126 MHz,
3
CDCl3, 27 ꢀC) d 56.1 (q), 79.3 (s), 113.2 (dd, JCF¼8 Hz),
2
2
114.5 (dd, JCF¼23 Hz), 116.6 (dd, JCF¼25 Hz), 134.2
3
1
(d, JCF¼6 Hz), 153.2 (s), 156.8 (d, JCF¼238 Hz);
19F NMR (376 MHz, CDCl3, 27 ꢀC) d 7.01–7.04 (m). Anal.
Calcd for C22H19F3O4: C, 65.34; H, 4.74. Found: C, 65.13;
H, 4.88.
1
further purification. Compound 3c: white solid. H NMR
(400 MHz, 27 ꢀC) d 3.85 (s, 3H), 4.94–4.96 (m, 2H), 7.53–
7.50 (m, 2H).

K. Iwanaga et al. / Tetrahedron 63 (2007) 10127–10132
10131
4.1.9. 2-Bromo-4-trifluoromethylanisole 4c.10 In the open
atmosphere, to a solution of 4-trifluoromethylanisole 3c
(4.79 g, 27.2 mmol) and sodium acetate (2.50 g,
30.5 mmol) in AcOH (100 mL) was added a solution of bro-
mine (1.6 mL, 31 mmol) in AcOH (10 mL) by dropwise at
room temperature. After the reaction mixture was stirred
for 1 day, bromine (0.5 mL, 9.8 mmol) was added. After stir-
ring for 1 day, the mixture was treated with aq Na2SO3
(100 mL) and extracted with CHCl3. The extracts were com-
bined and dried over anhydrous MgSO4, and then the solvent
was removed under reduced pressure. The residue was
distilled in vacuo (41 ꢀC at 1 mmHg) to afford 4c (2.77 g,
40%). Compound 4c: colorless liquid. 1H NMR (400 MHz,
27 ꢀC) d 3.95 (s, 3H), 7.67 (d, 1H, J¼8.8 Hz), 7.54 (dd,
1H, J¼1.5, 8.8 Hz), 7.80 (d, 1H, J¼1.5 Hz).
55.81; H, 3.80; HRMS-FAB (m/z): [M]+ calcd for
C25H19F9O3: 538.1190, found: 538.1177.
4.1.12. Trichloro[tris(2-methoxy-5-trifluoromethylphe-
nyl)methyl]germane 1c. To a solution of 6c (600 mg,
1.11 mmol) in benzene (15 mL) was added n-BuLi (1.67 M
hexane solution, 5.6 mmol) at 50 ꢀC. The mixture was stirred
at 50 ꢀC for 6 h. After removal of the solvent under reduced
pressure, DME (15 mL) and HMPA (0.78 mL, 4.5 mmol)
were added to the residue. To the mixture was added tetra-
chlorogermane (1.2 mL, 11 mmol) at 0 ꢀC. The mixture
was stirred at 0 ꢀC for 2 h and at room temperature overnight.
After removal of the solvent, the residue was treated with
20 mL of EtOH and then 10 mL of H2O. The mixture was ex-
tracted with CHCl3. The residue was dissolved in ether and
washed with 2% aq NaOH. The organic layer was dried
over anhydrous MgSO4, and the solvent was removed under
reduced pressure. The residue was subjected to GPLC to af-
ford 1c (166 mg, 21%). Compound 1c: colorless crystal, mp
4.1.10. Tris(2-methoxy-5-trifluoromethylphenyl)meth-
anol 5c. To Mg turnings (1.33 g, 54.6 mmol) was added a
solution of 4c (9.29 g, 36.4 mmol) in THF (20 mL) and
the reaction mixture was refluxed for 3 h. To the reaction
mixture was added a solution of diethyl carbonate (1.10 mL,
9.10 mmol) in THF (10 mL) and the reaction mixture was
refluxed overnight. The reaction mixture was treated with
EtOH (20 mL) and then H2O (10 mL). The organic layer
was extracted with CHCl3. The extracts were combined
and dried over anhydrous MgSO4, and then the solvent
was removed under reduced pressure. The residue was
subjected to GPLC to afford 5c (239 mg, 1.2%) and a mixture
including 5c (2.45 g). The mixture was used in the next step
of reactions without further purification. Compound
5c: white crystal, mp 188.4–188.7 ꢀC (dec). 1H NMR
(500 MHz, CDCl3, 27 ꢀC) d 3.56 (s, 9H), 5.30 (s, 1H),
6.94 (d, 3H, J¼8.6 Hz), 7.44 (d, 3H, J¼1.9 Hz), 7.56 (dd,
1
280.1–281.4 ꢀC (dec). H NMR (500 MHz, CDCl3, 27 ꢀC)
d 3.72 (s, 9H), 6.68 (d, J¼1.9 Hz), 7.05 (d, J¼8.6 Hz), 7.71
13
(dd, J¼1.9, 8.6 Hz); C NMR (126 MHz, CDCl3, 27 ꢀC)
d 54.5 (q), 66.9 (s), 110.6 (d), 123.5 (q, 2JCF¼33 Hz), 124.0
1
3
(q, JCF¼272 Hz), 125.6 (s), 127.1 (dq JCF¼3.5 Hz),
127.7 (dq JCF¼3.6 Hz), 158.8 (d); 19F NMR (376 MHz,
3
CDCl3, 27 ꢀC) d ꢁ63.6. Anal. Calcd for C25H18Cl3F9GeO3:
C, 41.91; H, 2.53. Found: C, 41.92; H, 2.70; HRMS-FAB
(m/z): [M–F]+ calcd for C25H1835Cl3F874GeO3: 696.9406,
found: 696.9405; calcd for C25H1835Cl237ClF874GeO3:
698.9376, found, 698.9377; calcd for C25H1835Cl3F872GeO3:
694.9415, found: 694.9521.
4.2. X-ray structural analysis
13
3H, J¼1.9, 8.6 Hz); C NMR (126 MHz, CDCl3, 27 ꢀC)
d 55.4 (q), 79.6 (s), 111.7 (d), 122.2 (q, 2JCF¼33 Hz), 124.5
Single crystals of 1a–c were grown from appropriate solu-
tion (acetonitrile/hexane solution for 1a, benzene/CHCl3 so-
lution for 1b and CHCl3 solution for 1c). The intensity data
were collected on a Rigaku/MSC Mercury CCD with Mo Ka
1
3
(q, JCF¼272 Hz), 126.3 (dq, JCF¼3.8 Hz), 127.0 (dq,
3JCF¼3.7 Hz), 131.6 (s), 159.2 (s); 19F NMR (376 MHz,
CDCl3, 27 ꢀC) d ꢁ63.5. HRMS-FAB (m/z): [M]+ calcd
for C25H19F9O4: 554.1140, found: 554.1134. Anal. Calcd
for C25H19F9O4: C, 54.16; H, 3.45. Found: C, 54.19;
H, 3.59.
˚
radiation (l¼0.71069 A). The structures were solved by the
direct method and refined by full-matrix least squares on F2
using SHELXS-97.11 Crystallographic data are listed in
Table 3. The structures were refined anisotropically except
4.1.11. Tris(2-methoxy-5-trifluoromethylphenyl)me-
thane 6c. To a solution of the mixture including 5c
(2.45 g) and CF3COOH (0.40 mL, 5.2 mmol) in AcOH
(15 mL) was added Et3SiH (10.0 mL, 62.6 mmol) and the
reaction mixture was stirred at 100 ꢀC for 1 day. The mixture
was monitored by 1H NMR, and CF3COOH (0.10 mL,
1.3 mmol) was added twice after 24 h and 48 h. After the
completion of the reaction, the reaction mixture was treated
with aq NaOH and extracted with CHCl3. The extracts were
combined and dried over anhydrous MgSO4, and then the
solvent was removed under reduced pressure. The residue
was purified by recrystallization from EtOH to afford 6c
(740 mg, 14% from 4c). Compound 6c: white crystal, mp
Table 3. Crystallographic parameters of 1a–c
1a
1b
1c
R
Formula
OMe
C25H27Cl3GeO6 C22H18Cl3GeO3F3 C25H18Cl3F9GeO3
F
CF3
Temperature/K 120(2)
Crystal system Monoclinic
120(2)
Trigonal
R3
14.18(1)
14.18(1)
21.65(2)
—
3769(5)
6
1.497
7769
120(2)
Monoclinic
P21/c
16.911(5)
9.701(5)
18.464(5)
113.715(5)
2773(2)
4
Space group
˚
P21/c
a/A
˚
17.083(6)
10.045(3)
17.980(6)
110.381(2)
2892(2)
4
b/A
˚
c/A
b/ꢀ
˚
V/A
3
1
140.5–140.6 ꢀC (dec). H NMR (500 MHz, CDCl3, 27 ꢀC)
Z
Dcalcd/g cmꢁ3
Reflections
collected
1.478
15,370
1.716
16,902
d 3.71 (s, 9H), 6.24 (s, 1H), 6.92 (d, 3H, J¼8.7 Hz), 6.93
(d, 3H, J¼1.9 Hz), 7.51 (dd, 3H, J¼1.9, 8.7 Hz); 13C
NMR (126 MHz, CDCl3, 27 ꢀC) d 38.6 (d), 55.7 (q), 110.4
Unique
4378
2751
4833
2
1
(d), 122.3 (q, JCF¼33 Hz), 124.4 (q, JCF¼272 Hz), 125.5
reflections
3
3
Goodness of fit 1.104
R1 (I>2s(I)) 0.0259
wR2 (all data) 0.0628
1.049
0.0429
0.1203
1.065
0.0356
0.0900
(dq, JCF¼3.5 Hz), 126.2 (dq, JCF¼3.5 Hz), 130.9 (s),
19
159.5 (s); F NMR (376 MHz, CDCl3, 27 ꢀC) d ꢁ63.4.
Anal. Calcd for C25H19F9O3: C, 55.77; H, 3.56. Found: C,

10132
K. Iwanaga et al. / Tetrahedron 63 (2007) 10127–10132
Dalton Trans. 1993, 1489–1492; (f) Blunden, S. J.; Smith,
P. J. J. Organomet. Chem. 1982, 226, 157–163.
4. (a) Auner, N.; Probst, R.; Hahn, F.; Herdtweck, E.
hydrogen atoms. Hydrogen atoms were idealized by using
the riding models. Crystallographic data (excluding struc-
ture factors) for the structures in this paper have been depos-
ited with the Cambridge Crystallographic Data Centre as
supplementary publication nos. CCDC 649686, CCDC
649687, CCDC 649688. Copies of the data can be obtained,
free of charge, on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK, (fax: +44-(0)1223-336033 or
e-mail: deposit@ccdc.cam.ac.uk).
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Acknowledgements
5. Iwanaga, K.; Kobayashi, J.; Kawashima, T.; Takagi, N.;
Nagase, S. Organometallics 2006, 25, 3388–3393.
This study was supported by Grant-in-Aid for The 21st Cen-
tury COE Program for Frontiers in Fundamental Chemistry
and a Grant-in-Aid for Scientific Research from the Ministry
of Education, Culture, Sports, Science and Technology of
Japan. We also thank Tosoh Finechem Co., Ltd and Shinetsu
Chemicals for the generous gifts of alkyllithiums and silicon
compounds, respectively.
6. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
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