Synthesis and structure of the first oxygen-donor-stabilized organogermanium(II) compounds

Article abstract of DOI:10.1021/om000679f

GeCl₂·dioxane reacts with 1 and 2 equiv of [2,4-di-tert-butyl-6-(tert-butoxymethyl)phenyl]lithium (t-BomxLi) to give the germanium(II) compounds t-BomxGeCl (1) and [t-Bomx]₂Ge (2), respectively. Reaction with 2 equiv of [2,4-di-tert-

Full text of DOI:10.1021/om000679f

42
Organometallics 2001, 20, 42-46
Syn th esis a n d Str u ctu r e of th e F ir st
Oxygen -Don or -Sta bilized Or ga n oger m a n iu m (II)
Com p ou n d s†
Peter J utzi,* Silke Keitemeyer, Beate Neumann, Anja Stammler, and
Hans-Georg Stammler
Faculty of Chemistry, University of Bielefeld, Universita¨tsstrasse, 33615 Bielefeld, Germany
Received August 7, 2000
GeCl2‚dioxane reacts with 1 and 2 equiv of [2,4-di-tert-butyl-6-(tert-butoxymethyl)phenyl]-
lithium (t-BomxLi) to give the germanium(II) compounds t-BomxGeCl (1) and [t-Bomx]2Ge
(2), respectively. Reaction with 2 equiv of [2,4-di-tert-butyl-6-(iso-propoxymethyl)phenyl]-
lithium (i-PomxLi) affords [i-Pomx]2Ge (3). Compounds 1-3 show intramolecular coordination
of the alkoxy ligand to the germanium(II) center. The use of the 2,4-di-tert-butyl-6-
(methoxymethyl)phenyl ligand (Momx) does not lead to the expected base-stabilized
germanium(II) species Momx2Ge but gives the germanium(IV) compound MomxGe[OCH2-
(2,4-di-tert-butylphenyl)](Me) (4) as the result of an intramolecular O-CH3 bond oxidative
addition process; X-ray crystal structure determinations are presented for 1, 2, and 4.
Ch a r t 1
The organometallic chemistry of donor-stabilized ger-
manium(II) compounds has developed into an active
area of research.1 Whereas compounds with substitu-
ents bearing nitrogen2 or phosphorus3 donors are well
established, systems stabilized with oxygen donors are
unknown thus far. As demonstrated in the chemistry
of donor-stabilized silicenium ions (R3Si+), variation of
the donor element results in astonishing changes in
structure, bonding, and reactivity;4 comparable phe-
nomena can be expected also in the chemistry of
germanium(II) compounds. Here we report the synthesis
and characterization of three oxygen-donor-stabilized
germanium(II) species. Furthermore, we describe the
formation of a germanium(IV) compound, which results
from intramolecular oxidative addition to the corre-
sponding germanium(II) center as a consequence of
reduction of steric bulk and of the +I-effect of the alkyl
group at the oxygen side-chain functionalized substitu-
ent.
We have used as substituents the 2,4-di-tert-butyl-6-
(methoxymethyl)phenyl group (Momx ) methoxymeth-
yl-m-xylyl group) (A), published by Yoshifuji in 1993,5
as well as the systems i-Pomx (i-propoxymethyl-m-xylyl
group) (B) and t-Bomx (t-butoxymethyl-m-xylyl group)
(C), which have been developed in our group (Chart 1).
In B and C the abbreviations explained above are used
in analogy to that of A, introduced by Yoshifuji. The “x”
refers to the substitution pattern of m-xylene although
tert-butyl groups are used instead of methyl substitu-
ents of the m-xylyl group.5
Reaction of GeCl2‚dioxane with t-BomxLi in THF in
1:1 ratio at -80 °C afforded [t-Bomx]GeCl (1) in 45%
yield. Treatment with 2 equiv of t-BomxLi led to the
formation of the homoleptic germanium(II) species
[t-Bomx]2Ge (2) (Scheme 1). Crystals of 1 and 2 suitable
for X-ray structure analysis were obtained from n-
hexane solution. The molecular structures are shown
in Figures 1 and 2. Crystallographic data are given in
Table 1; selected bond lengths and angles are presented
in Tables 2 and 3.
† Dedicated to Professor Herbert Schumann on the occasion of his
65th birthday.
(1) Barrau, J .; Rima, G. Coord. Chem. Rev. 1998, 178, 593.
(2) (a) Dias, H. V. R.; Wang, Z. J . Am. Chem. Soc. 1997, 119, 4650.
(b) Foley, S. R.; Bensimon, C.; Richeson, D. S. J . Am. Chem. Soc. 1997,
119, 10359. (c) Ossig, G.; Meller, A.; Bro¨nneke, C.; Mu¨ller, O.; Scha¨fer,
M.; Herbst-Irmer, R. Organometallics 1997, 16, 2116. (d) Leung, W.-
P.; Kwok, W.-H.; Weng, L.-H.; Law, L. T. C.; Zhou, Z. Y.; Mak, T. C.
W. J . Chem. Soc., Dalton Trans. 1997, 4301. (e) Drost, C.; Hitchcock,
P. B.; Lappert, M. F.; Pierssens, L. J .-M. J . Chem. Soc., Chem.
Commun. 1997, 1141. (f) Schmidt, H.; Keitemeyer, S.; Neumann, B.;
Stammler; H.-G., Schoeller, W. W.; J utzi, P. Organometallics 1998,
17, 2149. (g) Benet, S.; Cardin, C. J .; Cardin, D. J .; Constantine, S. P.,
Heath, P.; Rashid, H.; Teixeira, S.; Thorpe, J . H.; Todd, A. K.
Organometallics 1999, 18, 389. (h) J utzi, P.; Keitemeyer, S.; Neumann,
B.; Stammler, H.-G. Organometallics 1999, 18, 4778 and references
therein. (i) Winter, J . G.; Portius, P.; Kociok-Ko¨hn, G.; Steck, R.;
Filippou, A. Organometallics 1998, 17, 4176. (j) Constantine, S. P.; Cox,
H.; Hitchcock, P. B.; Lawless, G. A. Organometallics 2000, 19, 317.
(k) Drost, C.; Hitchcock, P. B.; Lappert, M. F. Organometallics 1998,
17, 3838. (l) Filippou, A. C.; Portius, P.; Kociok-Ko¨hn, G. Chem.
Commun. 1998, 2327. (m) Benet, S.; Cardin, C. J .; Cardin, D. J .;
Constantine, S. P.; Heath, P.; Rashid, H.; Teixeira, S.; Thorpe, J . H.;
Todd, A. K. Organometallics 1999, 18, 389. (n) Foley, S. R.; Zhou, Y.;
Yap, G. P. A.; Richeson, D. S. Inorg. Chem. 2000, 39, 924.
(3) Karsch, H. H. Russ. Chem. Bull. 1993, 42, 1937 and references
therein.
In 1 the side-chain functionalized substituent coor-
dinates in a bidentate fashion, leading to a remarkable
(4) Berlekamp, U.-H.; J utzi, P.; Mix, A.; Neumann, B.; Stammler,
H.-G.; Schoeller, W. W. Angew. Chem. 1999, 111, 2071.
(5) Yoshifuji, M.; Kamijo, K.; Toyota, K. Tetrahedron Lett. 1994, 35,
3971.
10.1021/om000679f CCC: $20.00 © 2001 American Chemical Society
Publication on Web 12/09/2000

O-Donor-Stabilized Organogermanium(II) Compounds
Organometallics, Vol. 20, No. 1, 2001 43
Ta ble 1. Cr ysta llogr a p h ic Da ta for 1, 2, a n d 4
empirical formula
fw
C19H31ClGeO, 1
383.48
C38H62GeO2, 2
623.47
C32H50GeO2, 4
539.31
cryst. color, habit
cryst. size, mm3
temp, K
colorless, rhombic
0.6 × 0.6 × 0.3
173(2)
yellow, irregular
0.7 × 0.5 × 0.3
173(2)
colorless, irregular
0.7 × 0.4 × 0.2
173(2)
radiation (λ, Å)
space group
Mo KR (0.71073 Å), graphite monochromator
P21/c
P21/n
P-1
unit cell dimensions, Å
a ) 11.441(4)
b ) 12.158(3)
c ) 14.579(6)
R ) 90
a ) 12.324(5)
a ) 10.559(4)
b ) 11.866(4)
c ) 13.140(3)
R ) 75
â ) 77.72(2)
γ ) 74.45(3)
1513.8(8)
2
1.183
2.17-28.50
8064
7659 (0.0385)
empirical
0.0562
0.1234
5782
b ) 19.887(9)
c ) 14.962(7)
unit cell angles, deg
R ) 90
â ) 96.57(3)
γ ) 90
â ) 92.28(3)
γ ) 90
V, Å3
Z
2014.6(12)
4
1.264
2.19-30.00
6135
5869 (0.0418)
semiempirical
0.0515
0.1047
4232
3664(3)
4
density (calcd), Mg/m3
θ range, data collection
reflns collected
independent reflns (Rint
1.130
2.02-30.03
11132
10 689 (0.0746)
semiempirical
0.0732
0.1214
5718
338
0.495/0.612
Siemens P2(1)
)
absorption correction from ψ-scans
final RF [I > 2σ(I)]
2
final RF [I > 2σ(I)]
no. of reflns used
parameters
218
328
largest diff. peak/hole, e Å3
diffractometer used
programs used
0.630/0.532
Siemens P2(1)
0.726/0.508
Siemens P2(1)
Siemens SHELXTL plus SHELXL-97
structure refinement
full-matrix least squares on F2
Sch em e 1
F igu r e 1. Molecular structure of 1 (50% probability).
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 1
Ge(1)-O(1)
2.073(2)
2.3331(11)
2.009(3)
82.04(9)
96.29(8)
91.24(7)
Ge(1)-Cl(1)
Ge(1)-C(1)
C(1)-Ge(1)-O(1)
C(1)-Ge(1)-Cl(1)
O(1)-Ge(1)-Cl(1)
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 2
Ge(1)-O(1)
2.189(3)
2.041(4)
2.058(4)
Ge(1)-C(1)
Ge(1)-C(20)
C(1)-Ge(1)-O(1)
C(1)-Ge(1)-C(20)
O(1)-Ge(1)-C(20)
80.32(12)
109.13(14)
91.52(12)
F igu r e 2. Molecular structure of 2 (50% probability).
geometry at the germanium center. The angle R (C1-
Ge-O) is 82.04°, the angle â (C1-Ge-Cl) is 96°, and the
angle γ (O-Ge-Cl) is nearly rectangular (∼91°). The
OfGe donor bond is unexpectedly short [2.073(2) Å],
much shorter than the Ge-O bond lengths in GeCl2‚
dioxane (2.48 and 2.41 Å);6 the observed distance
approaches that in covalent O-Ge(II) bonds as present
in [(t-Bu)3CO]2Ge [1.896(16) and 1.832(11) Å]7 and in
Ge[O(2,6-(t-Bu)2-4-Me-(C6H2)]2 [1.802(8) and 1.812(7)
Å].8 Similar Ge-O bond lengths (1.99 and 1.84 Å) are
present in the binuclear germanium calix[4]arene [t-Bu
-
(6) Kulishov, V. I.; Bokii, N. G.; Struchkov, Y. T.; Nefedov, O. M.;
Kolesnikov, S. P.; Perl’mutter, B. L. J . Struct. Chem. 1970, 11, 61.
(7) Fjeldberg, T.; Hitchcock, P. B.; Lappert, M. F.; Smith, S. J .,
Thorne, A. J . J . Chem. Soc., Chem. Commun. 1985, 939.

44 Organometallics, Vol. 20, No. 1, 2001
J utzi et al.
Sch em e 2
calix]Ge2.9 The Ge-Cl bond length is 2.3331(11) Å,
comparable to that in the related amino-functionalized
germanium(II) species [2,4-(t-Bu)2-6-(CH2NMe2)-(C6H2)]-
GeCl (MamxGeCl) [2.3283(4) Å] described in a previous
work.2f In 2 the structural features of the [t-Bomx]Ge
frame are quite similar to those found for 1; the
geometry at the germanium center and the Ge-C and
GerO bond lengths are comparable. As shown in Figure
2, only one of the two ether groups coordinates to the
germanium center. VT-NMR spectra show that the side
chains exchange their positions in solution. This dy-
namic process is fast on the NMR time scale at 80 °C
but slow at -40 °C. The Gibbs free energy of activation
(∆G#) as estimated from the coalescence of the diaste-
reotopic CH2 groups is ∼47 kJ /mol at 233 K.
F igu r e 3. Molecular structure of 4 (50% probability).
Sch em e 3
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 4
On reducing the steric bulk and the +I-effect of the
alkyl group on the oxygen center by the use of i-Pomx
(B) instead of t-Bomx (C), the corresponding monochlo-
rogermanium(II) compound is too unstable to permit its
characterization; only unidentifiable products were
obtained. However, the stable homoleptic species
[i-Pomx]2Ge (3) was formed by reaction of GeCl2‚dioxane
with i-PomxLi in THF at -80 °C in 1:2 ratio (Scheme
2). The solution NMR data of 3 are comparable to those
collected for 2. Dynamic behavior is observed at room
temperature but can be frozen out at -80 °C. The Gibbs
free energy of activation (∆G#) for the dynamic process
as estimated from the coalescence of the (CH3)2CH
groups is ∼43 kJ /mol at 223 K.
Ge(1)-O(1)
1.805(2)
1.959(3)
1.960(3
Ge(1)-C(16)
Ge(1)-C(1)
Ge(1)-C(17)
1.991(3)
C(1)-Ge(1)-O(1)
O(1)-Ge(1)-C(16)
C(16)-Ge(1)-C(1)
O(1)-Ge(1)-C(17)
C(16)-Ge(1)-C(17)
C(1)-Ge(1)-C(17)
91.31(11)
103.93(15)
103.40(14)
102.63(11)
128.05(14)
119.74(12)
In summary, we have prepared three novel oxygen-
donor-stabilized germanium(II) species (1-3) belonging
to a so far unknown class of compounds, by making use
of various 2,4-di-tert-butyl-6-(alkoxymethyl)phenyl sub-
stituents. Additionally, we have demonstrated that some
steric bulk and a pronounced +I-effect of the alkyl group
at the oxygen center are necessary for the stabilization
of such germanium(II) compounds.
Comparing the results of the chemistry of alkoxy-
methyl side-chain functionalized germanium(II) species
with those for related aminomethyl side-chain function-
alized compounds of the type MamxGeR (Mamx )
methylaminomethyl-m-xylyl derivative),2f,h similarities
as well as differences are observed. Common to all
compounds is a very strong DfGe donor-acceptor
interaction, leading to an ammonium or oxonium char-
acter at the donor atom. The average DfGe bond
lengths (2.09-2.19 Å for NfGe systems and 2.073-
2.189 Å for the OfGe systems) are more in the range
of covalent than in the range of coordinative bonds; the
latter are typical of other base-stabilized germanium-
(II) compounds.1,2
Upon utilization of the Momx group (A), which is less
bulky than B or C and which possesses a smaller +I-
effect, neither a heteroleptic nor a homoleptic germa-
nium(II) compound could be isolated. GeCl2‚dioxane
reacted with MomxLi in 1:2 ratio at -80 °C to give the
germanium(IV) compound MomxGe[OCH2-(2,4-di-tert-
butylphenyl)](Me) (4) (Scheme 3). 4 is the product of an
intramolecular O-CH3 oxidative addition at the ger-
manium center of the assumed intermediate germa-
nium(II) compounds MomxGeCl or Momx2Ge, which
could not be obtained even at low (-80 °C) temperature.
The solid-state structure of 4 was determined by
X-ray diffraction studies. Crystallographic data are
given in Table 1; selected bond lengths and angles are
collected in Table 4. The molecular structure depicted
in Figure 3 shows a distorted tetrahedral geometry at
the germanium center. The angle R (C1-Ge-O ) 91.3°)
is reduced as a consequence of the ring strain. Due to
this fact and due to the steric requirements of the second
alkoxy ligand, the angles â (C1-Ge-C17) and γ (C17-Ge-
C16) are enlarged (â ) 119.74°, γ ) 128.05°); the angles
δ (O-Ge-C17) and ꢀ (O-Ge-C16) are ∼103°.
The consequences of the strong DfGe bond are quite
different. In the case of the Momx substituent, the
pronounced oxonium character in an intermediate co-
ordination compound (MomxGeCl or [Momx]2Ge) leads
via methyl-group transfer to the final oxidation product
4. In contrast, alkyl-group transfer is not observed in
compounds with the Mamx or with the i-Pomx or
t-Bomx substituent.
(8) Cetinkaya, B.; Gu¨mru¨kcu¨, I.; Lappert, M. F.; Atwood, J . L.;
Rogers, R. D.; Zaworotko, M. J . J . Am. Chem. Soc. 1980, 102, 2088.
(9) McBurnett, B. G.; Cowley, A. H. Chem. Commun. 1999, 17.

O-Donor-Stabilized Organogermanium(II) Compounds
Organometallics, Vol. 20, No. 1, 2001 45
7.47 (s, 2H, aryl). 13C NMR (C6D6): δ 28.2, 31.5, 33.8 (C(CH3)3),
34.9, 38.1 (C(CH3)3), 71.6 (-CH2-), 85.3 (OC(CH3)3), 116.8, 121.7,
143.0, 150.6, 154.5, 155.9 (aryl C). MS [CI; m/z (Irel)]: 383 (7,
Investigations concerning the chemistry of 1-3 in
comparison to related aminomethyl-functionalized spe-
cies are in progress.
M+ - H), 347 (2, [t-BomxGe]+ - 2H), 203 [100, [t-Bomx]+
-
(Ot-Bu)]. Anal. Calcd for C19H31OGeCl (Mr ) 383.55): C, 59.49;
H, 8.14. Found: C, 59.12, H, 8.46.
Exp er im en ta l Section
P r ep a r a t ion of Bis[2,4-d i-ter t-b u t yl-6-(ter t-b u t oxy-
m eth yl)p h en yl]ger m a n iu m (II) (2). To a stirred solution of
1.15 g (3.24 mmol) of 2,4-di-tert-butyl-6-(tert-butoxymethyl)-
phenyl bromide in 10 mL of THF was added 2.02 mL of n-BuLi
(1.6 M in hexane) at -80 °C. After stirring for 2 h, a solution
of 0.37 g (1.62 mmol) of GeCl2‚dioxane in 5 mL of THF was
added at that temperature. The reaction mixture was allowed
to warm to room temperature within 1.5 h, and the solvent
was removed in vacuo. The residue was extracted with
n-hexane. Cooling the extracts to -30 °C afforded 2 as yellow
crystals (0.62 g, 1.00 mmol, 62%). 1H NMR (C6D6): δ 0.95, 1.39
(2s, 18H, C(CH3)3), 1.71 (br s, 18H, OC(CH3)3), 4.50, 4.57 (2d,
2H, -CH2-, 2J ) 12 Hz), 7.35-7.55 (only integral, 2H, aryl),
7.58 (s, 2H, aryl). 13C NMR (C6D6): δ 27.6, 31.6, 33.8 (C(CH3)3),
34.8, 38.3 (C(CH3)3), 68.0 (-CH2-), 77.7 (OC(CH3)3), 119.1, 121.9,
Gen er a l Da ta . All manipulations were carried out under
a purified argon atmosphere by standard vacuum techniques.
The solvents were commercially available and were purified
by conventional means and distilled immediately prior to use.
KOt-Bu and n-BuLi (1.6 M solution in n-hexane) were com-
mercially available. Momx, 2-Bromo-3,5-di-tert-butylbenzyl-
bromide, and NaOi-Pr were prepared according to the litera-
ture. Elemental analyses were performed by the Microanalytical
Laboratory of the Univerista¨t Bielefeld. The NMR spectra were
recorded on a Bruker Avance DRX 500 spectrometer (1H 500.1
MHz; 13C{1H}125.8 MHz). Chemical shifts are reported in
parts per million (ppm) and are referenced to the solvent as
an internal standard. Mass spectrometry was performed on a
VG Autospec spectrometer. Only characteristic fragments and
isotopes of the highest abundance are listed.
Gen er a l P r oced u r e for th e P r ep a r a tion of 2,4-Di-ter t-
bu tyl-6-(iso-p r op oxym eth yl)p h en yl Br om id e a n d 2,4-Di-
ter t-bu tyl-6-(ter t-bu toxym eth yl)p h en yl Br om id e. A solu-
tion of 19.29 g (53.3 mmol) of 2-bromo-3,5-di-tert-butylbenzyl
bromide in 80 mL of THF was added dropwise to a suspension
of 160.00 mmol of the alkoxide (2 ) NaOi-Pr, 3 ) KOt-Bu) in
40 mL of THF at 0 °C. The reaction mixture was allowed to
warm to room temperature and then stirred for another 12 h.
The resulting suspension was hydrolyzed with 350 mL of water
and extracted with diethyl ether (1 × 200 mL; 2 × 150 mL).
The combined organic layers were dried over Na2SO4. After
removal of the solvent, the residue was distilled in vacuo to
give 2,4-di-tert-butyl-6-(iso-propoxymethyl)phenyl bromide or
2,4-di-tert-butyl-6-(tert-butoxymethyl)phenyl bromide.
1
142.9, 149.2, 155.3, 155.4 (aryl C). H NMR (toluene-d8, -80
°C): δ 0.83, 1.05, 1.38, 1.44, 1.48, 2.09 (6s, 9H, C(CH3)3), 4.38,
2
4.51 (2d, 1H, -CH2- (noncoordinating), J ) 11 Hz), 4.43, 4.56
(2d, 1H, -CH2- (coordinating), 2J ) 14 Hz), 7.02, 7.50,7.50,
8.11 (4s, 1H, aryl). 13C NMR (toluene-d8, -80 °C): δ 26.6, 27.7,
31.3, 35.0, 37.3, 39.0 (C(CH3)3), 24.2, 27.2, 31.0, 34.6, 65.9, 69.4
(C(CH3)3), 72.1, 82.2 (-CH2-), 111.3, 117.6, 119.7, 121.0, 138.5,
146.5, 147.6, 149.4, 152.4, 154.3, 154.9, 157.5 (aryl C). MS [CI;
m/z (Irel)]: 625 (1, M+ + H), 569 [21, M+ - HC(CH3)3], 511
[82, M+ - 2C(CH3)3], 495 [13, M+ - 2C(CH3)3-CH3]. Anal. Calcd
for C38H62O2Ge (Mr ) 623.55): C, 73.19; H, 10.02. Found: C,
73.13, H, 10.06.
P r ep a r a t ion of Bis[2,4-d i-ter t-b u t yl-6-(iso-p r op oxy-
m eth yl)p h en yl]ger m a n iu m (II) (3). Within 5 min, 3.75 mL
(6.0 mmol) of a 1.6 M solution of n-BuLi in n-hexane was added
to a stirred solution of 2,4-di-tert-butyl-6-(iso-propoxymethyl)-
phenyl bromide (2.05 g, 6.00 mmol) in 20 mL of THF at -80
°C. The reaction mixture was stirred at that temperature for
2 h and then slowly added to a stirred solution of 0.69 g (3.00
mmol) of GeCl2‚dioxane in 20 mL of THF at -80 °C. The yellow
solution was warmed to room temperature within 1.5 h. The
solvent was removed in vacuo, and the residue was extracted
with n-hexane. Cooling the extracts to -30 °C after filtration
and concentration yielded 0.73 g (1.23 mmol, 41%) of 3 as a
2,4-Di-ter t-b u t yl-6-(iso-p r op oxym et h yl)p h en yl Br o-
m id e. Bp 90 °C, 0.01 mbar. Yield 14.74 g (43.17 mmol, 81%).
1H NMR (C6D6): δ 1.12 (d, 6H, CH(CH3)2, 3J ) 6 Hz), 1.27,
1.57 (2s, 9H, t-Bu), 3.48 (septet, 1H, CH(CH3)2, 3J ) 6 Hz),
4.64 (s, 2H, -CH2-), 7.51, 7.73 (2d, 1H, aryl, 4J ) 2 Hz). 13C
NMR (C6D6): δ 22.3 (CH(CH3)2), 30.3, 31.4 (C(CH3)3), 34.9, 37.4
(C(CH3)3), 71.4 (-CH2-), 71.8 (CH(CH3)2), 120.3 (quaternary aryl
C), 124.0, 142.1 (tertiary aryl C), 140.6, 147.1, 149.6 (quater-
nary aryl C). MS [CI; m/z (Irel)] 360 (59, M + NH4+), 298 [100,
M+ + H - (i-Pr)], 283 [42, M+-(t-Bu)]. Anal. Calcd for C18H29
-
1
yellow solid. H NMR (C6D6): δ 0.83, 0.88 (2d, 6H, CH(CH3)2,
OBr (Mr ) 341.34): C, 63.33; H, 8.56. Found: C, 62.90; H,
8.43.
3J ) 6 Hz), 1.38, 1.72 (2s, 18H, C(CH3)3), 3.48 (septet, 2H,
3
2
CH(CH3)2, J ) 6 Hz), 4.48, 4.52 (2d, 1H, -CH2-, J ) 12 Hz),
7.44 (br s, 2H, aryl), 7.60 (d, 2H, aryl, 4J ) 1 Hz). 13C NMR
(C6D6): δ 21.2 (CH(CH3)2), 31.6, 33.7 (C(CH3)3), 34.8, 38.3
(C(CH3)3), 71.3 (-CH2-), 73.3 (CH(CH3)2), 119.2, 122.0 (tertiary
aryl C), 142.6 149.4, 154.6, 155.9 (quaternary aryl C). 1H NMR
(-80 °C, toluene-d8): δ 0.61, 0.79, 0.92, 1.12 (4m, 3H, CH-
(CH3)2), 1.40, 1.42, 1.49, 2.19 (4s, 9H, C(CH3)3), 3.42, 3.58 (2m,
1H, CH(CH3)2), 4.15 (m, 2H, -CH2-), 4.58, 4.81 (2d, 1H, -CH2-,
2J ) 14 Hz), 6.94, 7.52, 7.84, 8.18 (4s, 1H, aryl). 13C NMR (-80
°C, toluene-d8): δ 19.3, 20.6, 20.7, 22.2 (CH(CH3)2), 31.4, 31.5,
31.7, 34.9 (C(CH3)3), 34.5, 35.0, 37.2, 40.0 (C(CH3)3), 70.0, 70.9
(CH(CH3)2), 70.3, 75.3 (-CH2-), 117.2, 120.1, 121.5, 121.8
(tertiary aryl C), 137.6, 147.2, 147.8, 149.5, 151.0, 154.0, 156.2,
2,4-Di-ter t-bu tyl-6-(ter t-bu toxym eth yl)ph en yl Br om ide.
Bp 95 °C, 0.01 mbar. Yield 14.96 g (42.11 mmol, 79%). 1H NMR
(C6D6): δ 1.17, 1.29, 1.58 (3s, 9H, t-Bu), 4.66 (s, 2H, -CH2-),
4
7.51, 7.83 (2d, 1H, aryl, J ) 2 Hz). 13C NMR (C6D6): δ 27.7,
30.3, 31.4 (C(CH3)3), 34.9, 37.5, 73.4 (C(CH3)3), 65.4 (-CH2-),
120.3 (quaternary aryl C), 123.9, 124.3 (tertiary aryl C), 141.1,
147.1, 149.6 (quaternary aryl C). MS [CI; m/z (Irel)]: 372 (15,
M + NH4+), 356 (14, M+), 298 [100, M+ + H - (t-Bu)], 219
[54, M+ + H - (t-Bu) - Br]. Anal. Calcd for C19H31OBr (Mr )
355.36): C, 64.21; H, 8.79. Found: C, 64.26, H, 8.93.
P r ep a r a tion of [2,4-d i-ter t-bu tyl-6-(ter t-bu toxym eth -
yl)p h en yl]ger m a n iu m (II) Ch lor id e (1). During 3 min, 2.3
mL (3.69 mmol) of a 1.6 M solution of n-BuLi in n-hexane was
added to a stirred solution of 2,4-di-tert-butyl-6-(tert-butoxy-
methyl)phenyl bromide (1.31 g, 3.69 mmol) in 15 mL of THF
at -80 °C. The reaction mixture was stirred at that temper-
ature for 2 h and then slowly added to a cooled solution (-80
°C) of 0.85 g (3.69 mmol) of GeCl2‚dioxane in 20 mL of THF.
The yellow solution was warmed to room temperature during
1 h. The solvent was removed in vacuo, and the residue was
extracted with n-hexane. Cooling the solution to -30 °C after
filtration and concentration yielded 0.64 g (1.66 mmol, 45%)
of 1 as colorless crystals. 1H NMR (C6D6): δ 1.18, 1.33, 1.51
(3s, 9H, C(CH3)3), 4.41, 5.11 (2d, 1H, -CH2-, 2J ) 11 Hz), 6.97,
153.3 (quaternary aryl C). MS [CI; m/z (Irel)]: 613 (16, M+
+
NH3), 597 (77, M+ + H), 555 [46, M+ - CH(CH3)2 + 2H], 335
(66, i-PomxGe+ + H). Anal. Calcd for C36H58O2Ge (Mr
595.50): C, 72.61; H, 9.81. Found: C, 72.45; H, 9.71.
)
P r ep a r a tion of [2,4-d i-ter t-bu tyl-6-(m eth oxym eth yl)-
p h en yl](m et h yl)[2,4-d i-ter t-b u t ylp h en yl-6-oxym et h yl)-
ger m a n iu m (IV) (4). During 5 min 3.75 mL (6.0 mmol) of a
1.6 M solution of n-BuLi in n-hexane was added to a stirred
solution of 2,4-di-tert-butyl-6-(methoxymethyl)phenyl bromide
(1.88 g, 6.00 mmol) in 20 mL of THF at -80 °C. The reaction
mixture was stirred at that temperature for 2 h and then

46 Organometallics, Vol. 20, No. 1, 2001
J utzi et al.
slowly added to a solution of 0.69 g (3.00 mmol) GeCl2‚dioxane
in 20 mL of THF at -80 °C. The yellow solution was warmed
to room temperature within 1.5 h. The solvent was removed
in vacuo, and the residue was extracted with n-hexane. Cooling
the extracts to -30 °C after filtration and concentration yielded
0.87 g (1.62 mmol, 54%) of 4 as colorless crystals. 1H NMR
(C6D6): δ 1.22 (s, 3H, GeCH3), 1.26, 1.27, 1.28, 1.55 (4s, 9H,
C32H50O2Ge (Mr ) 539.39): C, 71.60; H, 9.34. Found: C, 71.31,
H, 9.46.
Ack n ow led gm en t. The financial support of the
Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie, as well as a gift of germanium
from Chemetall GmbH, Frankfurt/Main, are gratefully
acknowledged.
2
C(CH3)3), 2.67 (s, 3H, OCH3), 4.33, 4.51 (2d, 1H, -CH2-, J )
12 Hz), 5.44, 5.51 (2d, 1H, -CH2-, 2J ) 14 Hz), 7.11, 7.50, 7.66,
7.72 (4s, 1H, aryl). 13C NMR (C6D6): δ 15.1 (GeCH3), 31.2, 31.5,
32.6, 33.9 (C(CH3)3), 34.8, 34.9, 36.8, 37.1 (C(CH3)3), 57.4
(OCH3), 71.9, 74.6 (-CH2-), 122.6, 123.0, 125.4, 133.3, 135.8,
146.4, 148.5, 151.9, 153.3, 155.4, 158.0 (aryl C). MS [CI; m/z
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, positional and thermal parameters, and selected bond
lengths and angles (28 pages). Ordering information is given
on any current masthead page.
(Irel)]: 541 (30, M+ + H), 525 (37, M+ - CH3), 509 (33, M+
H - OCH3), 307 (100, M+ + H - Momx). Anal. Calcd for
+
OM000679F