Silylgermylpotassium compounds

Article abstract of DOI:10.1021/om0491894

By the reactions of potassium tert-butoxide with a number of oligosilylgermanes, oligosilylgermylpotassium compounds were generated. Their chemistry very much resembles that of the analogous oligosilylsilylpotassium compounds. However, the ease of formation is even more pronounced in the case of the germyl anions. Again potassium tert-butoxide proved to be a highly selective metalation reagent, leading to no unwanted cleavage of Si - Ge or Ge - Ge bonds. A number of new and potentially useful oligosilylgermyl mono- and dianions have been prepared in this manner.

Full text of DOI:10.1021/om0491894

Organometallics 2005, 24, 1263-1268
1263
Silylgermylpotassium Compounds
Jelena Fischer, Judith Baumgartner, and Christoph Marschner*
Institut f u¨ r Anorganische Chemie der Technischen Universit a¨ t Graz,
Stremayrgasse 16, A-8010 Graz, Austria
Received October 20, 2004
By the reactions of potassium tert-butoxide with a number of oligosilylgermanes,
oligosilylgermylpotassium compounds were generated. Their chemistry very much resembles
that of the analogous oligosilylsilylpotassium compounds. However, the ease of formation is
even more pronounced in the case of the germyl anions. Again potassium tert-butoxide proved
to be a highly selective metalation reagent, leading to no unwanted cleavage of Si-Ge or
Ge-Ge bonds. A number of new and potentially useful oligosilylgermyl mono- and dianions
have been prepared in this manner.
Introduction
Scheme 1. Formation of
Tris(trimethylsilyl)germylpotassium (1)
While the chemistry of oligosilyl anions has received
increasing attention over the last few years,1 the
analogous chemistry of silyl-substituted germanium
compounds was very much limited to the chemistry of
2
the tris(trimethylsilyl)germyl fragment. Brook et al.
introduced this moiety in an attempt to obtain germenes
3
via photolytic rearrangement of acylgermanes. For the
Results and Discussion
synthesis of tris(trimethylsilyl)germyllithium they uti-
lized a route pioneered by Gilman et al. for the synthesis
of tris(trimethylsilyl)silyllithium. Starting from tet-
rakis(trimethylsilyl)germane, reaction with methyllith-
ium cleaved a trimethylsilyl group and formed tris-
trimethylsilyl)germyllithium and tetramethylsilane.
Some structural investigations of this germyllithium
reagent were carried out, and it eventually became the
reagent of choice for the introduction of this particular
germyl substituent into transition metal and main
group compounds. While tris(trimethylsilyl)germyl-
Recent work by Teng and Ruhlandt-Senge concerning8
the synthesis of tris(trimethylsilyl)germylpotassium
prompts us to report our own results of research in this
area. In analogy with the above-mentioned work, we
reacted tetrakis(trimethylsilyl)germane with potassium
tert-butoxide to obtain tris(trimethylsilyl)germylpotas-
sium (1) (Scheme 1). In accordance with our experiences
with the tris(trimethylsilyl)silylpotassium chemistry,9
the reaction could be conducted either in THF or in an
aromatic solvent. The latter case, though, required the
presence of crown ether.
4
(
5
6
lithium usually is coordinated by three THF molecules,
recently the unsolvated reagent became available and
The reactivity of 1 very much resembles that of tris-
(trimethylsilyl)silylpotassium. Reactions with electro-
philes gave the expected products (Scheme 2). Simple
hydrolysis with aqueous sulfuric acid gave the respec-
7
was shown to exist as a trimer in solid state.
*
Corresponding author. Tel: ++43-316-873-8209. Fax: ++43-316-
8
73-8701. E-mail: marschner@anorg.tu-graz.ac.at.
3
tive germanium hydride (2); reaction with ethyl bro-
(
1) (a) Lickiss, P. D.; Smith, C. M. Coord. Chem. Rev. 1995, 145,
mide yielded tris(trimethylsilyl)ethylgermane (3). Re-
7
1
5-124. (b) Tamao, K.; Kawachi, A. Adv. Organomet. Chem. 1995, 38,
-58. (c) Belzner, J.; Dehnert U. In The Chemistry of Organic Silicon
Compounds; Rappoport, Z., Apeloig Y., Eds.; J. Wiley & Sons: New
York, 1998; Vol. 2, p 779-825. (d) Sekiguchi, A.; Lee, V. Y.; Nanjo, M.
Coord. Chem. Rev. 2000, 210, 11-45.
(6) (a) Braunschweig, H.; Colling, M.; Kollann, C.; Englert, U. J.
Chem. Soc., Dalton Trans. 2002, 2289-2296. (b) Linti, G.; Rodig, A.
Chem. Commun. 2000, 127-128. (c) Sekiguchi, A.; Fukaya, N.;
Ichinohe, M.; Takagi, N.; Nagase, S. J. Am. Chem. Soc. 1999, 121,
11587-11588. (d) Mallela, S. P.; Saar, Y.; Hill, S.; Geanangel, R. A.
Inorg. Chem. 1999, 38, 2957-2960. (e) Schwan, F.; Mallela, S. P.;
Geanangel, R. A. J. Chem. Soc., Dalton Trans. 1996, 4183-4187. (f)
Mallela, S. P.; Geanangel, R. A. Inorg. Chem. 1994, 33, 6357-6360.
(g) Mallela, S. P.; Geanangel, R. A. Inorg. Chem. 1994, 33, 1115-1120.
(h) Mallela, S. P.; Geanangel, R. A. Inorg. Chem. 1993, 32, 2, 5623-
5625. (i) Bonasia, P. J.; Christou, V.; Arnold, J. J. Am. Chem. Soc.
1993, 115, 6777-6781. (j) Maerkl, G.; Wagner, R. Tetrahedron Lett.
1986, 27, 4015-4018.
(7) Nanjo, M.; Nanjo, E.; Mochida, K. Eur. J. Inorg. Chem. 2004,
2961-2967.
(8) Teng, W.; Ruhlandt-Senge, K. Organometallics 2004, 23, 952-
956.
(9) (a) Marschner, Ch. Eur. J. Inorg. Chem. 1998, 221-226. (b)
Kayser, Ch.; Fischer, R.; Baumgartner, J.; Marschner, Ch. Organo-
metallics 2002, 21, 1023-1030. (c) Fischer, R.; Frank, D.; Gaderbauer,
W.; Kayser, Ch.; Mechtler, Ch.; Baumgartner, J.; Marschner, Ch.
Organometallics 2003, 22, 3723-3731.
(
2) (a) Freitag, S.; Herbst-Irmer, R.; Lameyer, L.; Stalke, D. Orga-
nometallics 1996, 15, 2839-2841. (b) Heine, A.; Stalke, D. Angew.
Chem. 1994, 106, 121-123; Angew. Chem. Int. Ed. 1994, 33, 113-
1
15.
(
3) Brook, A. G.; Abdesaken, F.; S o¨ llradl, H. J. Organomet. Chem.
1
986, 299, 9-13.
(
4) (a) Gilman, H.; Holmes, J. M.; Smith, C. L. Chem. Ind. (London)
1
1
965, 848-849. (b) Gutekunst, G.; Brook, A. G. J. Organomet. Chem.
982, 225, 1-3.
(
5) (a) Nanjo, M.; Oda, T.; Mochida, K. Bull. Chem. Soc. Jpn. 2003,
7
6, 1261-1264. (b) Nanjo, M.; Oda, T.; Mochida, K. J. Organomet.
Chem. 2003, 672, 100-108. (c) Nanjo, M.; Oda, T.; Mochida, K. Chem.
Lett. 2002, 108-109. (d) Casty, G. L.; Tilley, T. D.; Yap, G. P. A.;
Rheingold, A. L. Organometallics 1997, 16, 4746-4754. (e) Mitchell,
G. P.; Tilley, T. D. Organometallics 1996, 15, 3477-3479. (f) Mallela,
S. P.; Schwan, F.; Geanangel, R. A. Inorg. Chem. 1996, 35, 745-748.
(
1
g) Campion, B. K.; Heyn, R. H.; Tilley, T. D. Organometallics 1993,
2, 2584-2590. (h) Arnold, J.; Roddick, D. M.; Tilley, T. D.; Rheingold,
A. L.; Geib, S. J. Inorg. Chem. 1988, 27, 3510-3514.
1
0.1021/om0491894 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 02/10/2005

1264 Organometallics, Vol. 24, No. 6, 2005
Fischer et al.
Scheme 2. Reactions of
Tris(trimethylsilyl)germylpotassium (1)
Scheme 4. Formation of Germyl Mono- (6a) and
1,4-Dianion (6b)
Scheme 5. Use of 6b for the Synthesis of
Germa-Sila-Heterocycles
Scheme 3. Formation of Germylsilyl and
Digermyl Mono- and Dipotassium Compounds
compound 5b, with the second metalation step being
much slower (Scheme 3). Again, this behavior is in
accordance with our previous observations on the syn-
thesis of oligosilyl dianions.11 The potassium tert-
butoxide cleavage of hexakis(trimethylsilyl)digermane
(7) was also examined. Depending on the amount of
potassium alkoxide used, either the mono- (7a) or di-
(7b) potassium compound was obtained (Scheme 3).
In a further attempt to compare the germanium
chemistry to that of silicon also the mono- (6a) and di-
(6b) anions of 6 were generated by reaction with either
1 or 2 equiv of potassium tert-butoxide (Scheme 4). Both
reactions proceeded smoothly in full accordance with
what had been observed before in the case of the silicon
analogues. The second metalation step was comparably
fast, and it was found that for the formation of 6b the
use of crown ether can be avoided if the reaction was
carried out in THF.
action with zirconocene dichloride gave tris(trimeth-
ylsilyl)germylzirconocene chloride (4), a substance
previously prepared by Tilley and co-workers using the
germyllithium reagent. Reaction with tris(trimethyl-
silyl)silyl chloride gave tris(trimethylsilyl)[tris(tri-
methylsilyl)silyl]germane (5). To introduce two tris-
1
0
(
1
trimethylsilyl)germyl units in one molecule, 2 equiv of
was reacted with 1,2-dibromotetramethyldisilane to
obtain 1,2-bis[tris(trimethylsilyl)germyl]tetramethyl-
disilane (6). Also, in close analogy with the chemistry
of the tris(trimethylsilyl)silyl anion, the formation of
3
hexakis(trimethylsilyl)digermane (7) was achieved by
reaction of 1 with 1,2-dibromoethane. All these reactions
proceeded cleanly, giving the expected products in good
to excellent yields.
The silicon analogue of 6b had served as a versatile
precursor for the syntheses of a number of homo- and
heterocyclosilanes.9 Accordingly, 6b also was used for
the preparation of stanna- (8) and a zirconocena- (9)
disilacyclogermanes (Scheme 5). Both reactions pro-
ceeded as expected to give the five-membered rings in
good yield.
c,12
As we have studied the formation of numerous oli-
gosilylpotassium compounds by reaction of oligosilanes
with potassium tert-butoxide, it was of interest to
investigate analogous chemistry with 5, 6, and 7.
Especially 5 was considered an interesting molecule
with respect to this. The fact that there are three
trimethylsilyl groups at each of the central silicon and
germanium atoms should exclude any kinetic prefer-
ences for one side of the molecule. Surprisingly, reaction
of 5 with 1 equiv of potassium tert-butoxide afforded
metalation exclusively at the germanium atom (5a)
X-ray Crystallography. The two dianons 6b and 7b
as well as the 1-stanna-2,5-digermacyclopentasilane 8
were studied by single-crystal structure analysis (Table
1). 7b (Figure 1) could be compared to the analogous
1,2-dipotassium disilane.11 Due to a different content
of solvent (benzene) in the crystal, the compounds did
not belong to the same space group. In addition to one
and a half molecules of 7b, one benzene molecule was
found in the asymmetric unit. As had already been
observed for the 1,2-dipotassiodisilane,11 in the case of
7b the central Ge-Ge bond is also elongated by 0.1 Å
to 2.5805(9) Å. The elongation of the Si-Ge bonds is
less pronounced but still significant to values from
2.4017(17) to 2.4062(13) Å. The degree of pyramidization
is relatively high, as can be judged from the small angles
for Si(1)-Ge(1)-Si(2) (92.52(5)°) and Si(3)-Ge(2)-
Si(4) (95.47(5)°).
(
Scheme 3). While it seems evident that thermodynamic
reasons favor the formation of a germanide over that of
a silanide, it could be likely that at an early stage of
the reaction both 5a and the respective silylpotassium
compounds are formed. Attempts to detect such mix-
tures by means of NMR spectroscopy, however, were not
successful. At least at room temperature the reaction
seems to be too fast to observe any kinetically controlled
product ratio.
Reaction of 5 with 2 equiv of potassium tert-butoxide
in the presence of crown ether gave the 1,2-dipotassium
(
10) Arnold, J.; Roddick, D. M.; Tilley, T. D.; Rheingold, A. L.; Geib,
(11) Fischer, R.; Konopa, T.; Baumgartner, J.; Marschner, C. Or-
ganometallics 2004, 23, 1899-1907.
S. J. Inorg. Chem. 1988, 27, 3510-3514.

Silylgermylpotassium Compounds
Organometallics, Vol. 24, No. 6, 2005 1265
Table 1. Crystallographic Data for Compounds 6b, 7b, and 8
6b
7b
8
empirical formula
Mw
C52H108Ge2K2O12Si6
C60H132Ge3K3O18Si6
C18H54Ge2Si6Sn
1317.30
1645.27
703.02
temp [K]
size [mm]
cryst syst
space group
a [Å]
100(2)
100(2)
100(2)
0.55 × 0.38 × 0.20
0.50 × 0.35 × 0.24
0.44 × 0.32 × 0.02
monoclinic
triclinic
monoclinic
P2(1)/c
P1h
C2/c
17.911(4)
11.906(2)
15.901(3)
b [Å]
18.560(4)
19.793(4)
9.5497(19)
c [Å]
11.320(2)
20.304(4)
22.498(5)
R [deg]
90
114.50(3)
90
â [deg]
105.69(3)
91.99(3)
92.68(3)
γ [deg]
90
102.03(3)
90
3
V [Å ]
3623.1(13)
4219.0(15)
3412.7(12)
Z
2
2
4
Fcalc [g cm-3]
1.207
1.295
1.368
abs coeff [mm-1]
F(000)
1.092
1.351
2.692
1404
1746
1440
θ range
1.61 to 25.00
25 315/6373 [R(int) ) 0.1147]
25.00 [99.9]
1.77 to 25.00
1.81 to 24.00
10 582/2658 [R(int) ) 0.0706]
24.00 [99.2]
no. of reflns collected/unique
completeness to θ [%]
abs corr
30 078/14 665 [R(int) ) 0.0417]
25.00 [98.7]
SADABS
SADABS
SADABS
no. of data/restraints/params
goodness of fit on F
6373/0/342
14 665/3/829
2658/0/132
2
1.073
1.031
1.219
final R indices [I>2σ(I)]
R indices (all data)
R1 ) 0.0846, wR2 ) 0.1947
R1 ) 0.1128, wR2 ) 0.2120
1.288 and -1.557
R1 ) 0.0522, wR2 ) 0.1399
R1 ) 0.0707, wR2 ) 0.1506
1.735 and -1.666
R1 ) 0.0918, wR2 ) 0.2229
R1 ) 0.0958, wR2 ) 0.2252
3.041 and -1.395
-
3
largest diff peak/hole [e /Å ]
The structure of 6b (Figure 2) exhibited a similar but
less distinct picture. Half of a molecule was found in
the asymmetric unit together with one benzene mol-
ecule. Again the Ge-Si bond along the main chain is
the longest: Ge(1)-Si(3) 2.4291(18) Å. The bond dis-
tances to the trimethylsilyl groups (2.3924(19) and
Ge(1)-Si(2) 97.77(7)°, Si(1)-Ge(1)-Si(3) 105.83(7)°,
Si(2)-Ge(1)-Si(3) 100.53(6)°), but considerably smaller
than for 7b.
Compound 8 was found to exhibit a C2 symmetric
half-chair conformation (Figure 3). This is similar to
what was found for a related compound with a diphen-
ylstannylene unit and silicon instead of the germanium
atoms.9b The Sn(1)-Ge(1) distance of 2.6120(16) Å is
in the range of values observed for similar compounds.6
The same can be said about the germanium-silicon
bond lengths, which range from 2.37 to 2.39 Å.
NMR Spectroscopy. For the chemistry of trifold
silylated silylpotassium compounds it was found that
the 29Si NMR resonances of the negatively charged
silicon atoms undergo a pronounced upfield shift of
2.413(2) Å), however, are close to this value. The central
Si-Si bond (2.378(3) Å) is not affected by the anionic
character. The deviation from the perfect tetrahedral
angle around the germanium is still obvious (Si(1)-
g,13
Figure 1. Molecular structure and numbering of 7b with
3
0% probability thermal ellipsoids; all hydrogen atoms
have been omitted for clarity. Only one molecule of two in
the asymmetric unit is drawn. Selected bond lengths [Å]
and bond angles [deg] with estimated standard devia-
tions: K(1)-Ge(1) 3.5223(17), K(2)-Ge(2) 3.4968(16),
Ge(1)-Si(1) 2.4017(17), Ge(1)-Si(2) 2.4062(13), Ge(1)-Ge-
Figure 2. Molecular structure and numbering of 6b with
30% probability thermal ellipsoids; all hydrogen atoms
have been omitted for clarity. Selected bond lengths [Å]
and bond angles [deg] with estimated standard devia-
tions: K(1)-Ge(1) 3.4208(17), Ge(1)-Si(1) 2.3924(19),
Ge(1)-Si(2) 2.413(2), Ge(1)-Si(3) 2.4291(18), Si(3)-Si(3A)
2.378(3), Si(1)-Ge(1)-Si(2) 97.77(7), Si(1)-Ge(1)-Si(3)
105.83(7), Si(2)-Ge(1)-Si(3) 100.53(6), Si(1)-Ge(1)-K(1)
96.99(6), Si(2)-Ge(1)-K(1) 117.62(6), Si(3)-Ge(1)-K(1)
132.10(5), Si(3A)-Si(3)-Ge(1) 116.05(10).
(
2) 2.5805(9), Ge(2)-Si(3) 2.4049(13), Ge(2)-Si(4)
.4057(18), Si(1)-Ge(1)-Si(2) 92.52(5), Si(1)-Ge(1)-Ge-
2) 98.28(4), Si(2)-Ge(1)-Ge(2) 98.75(4), Si(1)-Ge(1)-K(1)
2
(
134.23(4), Si(2)-Ge(1)-K(1) 99.65(4), Ge(2)-Ge(1)-K(1)
122.72(3), Si(3)-Ge(2)-Si(4) 95.47(5), Si(3)-Ge(2)-Ge(1)
97.30(4), Si(4)-Ge(2)-Ge(1) 98.73(4), Si(3)-Ge(2)-K(2)
126.59(4), Si(4)-Ge(2)-K(2) 115.68(4), Ge(1)-Ge(2)-K(2)
117.62(3), K(1)-Ge(1)-Ge(2)-K(2) -159.15(3).

1
266 Organometallics, Vol. 24, No. 6, 2005
Table 2. 29Si NMR Shifts for Me
compound E ) Si
Fischer et al.
3
Si and (Me
2
Si) Groups (δ in ppm)
E ) Ge
∆Si-Ge
(
(
(
(
(
(
Me3Si)4E
-9.6
-3.9
-5.5
4.1
Me3Si)3EK
-3.3
0.6
Me3Si)3EH
Me3Si)3EEt
Me3Si)3EZr(Cl)Cp2
Me3Si)3EE(SiMe3)3
-10.9
-12.3
-6.1
-6.5
4.4
-7.4
4.9
-2.1
4.0
-9.0
-5.0
4.0
K(Me3Si)2EE(SiMe3)3
K(Me3Si)2EE(SiMe3)2K
-8.9/ -11.7
-5.4
-4.9/ -6.8
-5.3
4.0/4.9
0.1
(
Me3Si)3SiGe(SiMe3)3
Me3Si)3SiGe(SiMe3)2K
-9.9
-4.9
5.0
(
-10.5 [(Me3Si)3Si]
-5.4 [(Me3Si)2Ge]
a
a
K(Me3Si)2SiGe(SiMe3)2K
Me3Si)3E(SiMe2)2E(SiMe3)3
-5.6
-4.8
0.8
4.6
0.3
2.6
3.8
(
-9.6 (-29.8)
-3.7 (-24.5)
-2.4 (-29.2)
-5.4 (-22.2)
-5.0 (-24.4)
-3.4 (-22.4)
-5.0 (-24.4)
-1.0 (-16.8)
K(Me3Si)2E(SiMe2)2E(SiMe3)2K
Cp2Zr[E(SiMe3)2SiMe2]2
Me2Sn[E(SiMe3)2SiMe2]2
a
Unambiguous assignment was not possible.
previously studied oligosilylpotassium compounds. Com-
pared to silicon, the increased ability of germanium to
stabilize negative charge clearly facilitates the forma-
tion of the germanides. As a consequence, the use of a
crown ether, which is a real necessity for a rapid
formation of silyl-dianions, is not required for the rapid
formation of 6b. The reactivity of the obtained oligosi-
lylgermylpotassium compounds is comparable to that
of the analogous all-organosilicon compounds. Thus, the
described mono- and dipotassium compounds widely
extend the repertoire of existing nucleophilic bulky
germylation reagents. They can be considered interest-
ing reagents for further studies on the chemistry of
germanium transition metal and main group com-
pounds.
Figure 3. Molecular structure and numbering of 8 with
0% probability thermal ellipsoids; all hydrogen atoms
3
Experimental Part
have been omitted for clarity. Selected bond lengths [Å]
and bond angles [deg] with estimated standard devia-
tions: Sn(1)-Ge(1) 2.6120(16), Ge(1)-Si(2) 2.375(4),
Ge(1)-Si(1) 2.383(4), Ge(1)-Si(3) 2.390(4), Si(3)-Si(3A)
All reactions were carried out under an atmosphere of dry
argon or nitrogen. Solvents were dried using a column solvent
14
purification system. Potassium tert-butoxide was purchased
2
.358(8), C(1A)-Sn(1)-C(1) 105.2(8), Ge(1)-Sn(1)-Ge(1A)
04.78(8), Si(2)-Ge(1)-Si(1) 111.09(15), Si(2)-Ge(1)-
exclusively from Merck. All other chemicals were used as
received from several different chemical suppliers.
1
Si(3) 112.24(14), Si(1)-Ge(1)-Si(3) 112.93(15), Si(2)-
Ge(1)-Sn(1) 107.90(11), Si(1)-Ge(1)-Sn(1) 108.89(11),
Si(3)-Ge(1)-Sn(1) 103.34(11).
1
H (300 MHz), C (75.4 MHz), and 29Si (59.3 MHz) NMR
13
spectra were recorded on a Varian Unity INOVA 300 spec-
29
trometer. Samples for Si spectra were either dissolved in
deuterated solvents or in cases of reaction samples measured
about 60 ppm, while the trimethylsilyl groups attached
to these atoms move approximately 5 ppm to lower field.
For the germyl anions studied in this report we were
restricted to the observation of the trimethylsilyl reso-
nances. A comparison of the neutral silyl and germyl
compounds showed that the trimethylsilyl signals of the
germanium congeners are shifted about 4-5 ppm to
lower field compared to the silicon series (Table 2). If,
however, anionic derivatives were compared, the shift
differences decreased to values most times smaller than
with a D O capillary in order to provide a lock frequency signal.
2
2
9
To compensate for the low isotopic abundance of Si, the
INEPT pulse sequence was used for the amplification of the
signal. The completeness of reactions was usually controlled
by NMR spectroscopy. For X-ray structure analysis crystals
were mounted onto the tip of a glass fiber, and data collection
was performed with a Bruker-AXS SMART APEX CCD
diffractometer (wavelength 0.71073 Å). The data were reduced
15
2
16
to F
o
and corrected for absorption effects with SAINT and
SADABS, respectively. Structures were solved using direct
17
1
ppm. This effect is caused by the very slight change
(
12) Kayser, Ch.; Kickelbick, G.; Marschner, Ch. Angew. Chem.
2002, 114, 1031-1034; Int. Ed. 2002, 41, 989-992.
13) (a) Sharma, H. K.; Cervantes-Lee, F.; P a´ rk a´ nyi, L.; Pannell,
in chemical shift upon metalation of the germanium
compounds. This indicates a greatly reduced participa-
tion of the trimethylsilyl groups in the localization of
the negative charge for the germanium anions. For the
case of 7b an even smaller upfield shift compared to 7
can be observed.
(
K. H. Organometallics 1996, 15, 429-435; (b) Dinnebier, R. E.;
Bernatowicz, P.; Helluy, X.; Sebald, A.; Wunschel, M.; Fitch, A.; van
Smaalen, S. Acta Crystallogr. B 2002, 58, 52-61.
(
14) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518-1520.
(15) (a) Morris, G. A.; Freeman, R. J. Am. Chem. Soc. 1979, 101,
7
8
60-762; (b) Helmer, B. J.; West, R. Organometallics 1982, 1, 877-
79.
(
16) SAINTPLUS, Software Reference Manual, Version 6.45; Bruker-
Conclusion
AXS: Madison, WI, 1997-2003.
(
17) Blessing, R. H. Acta Crystallogr. A 1995, 51, 33-38. SADABS,
The chemistry of the investigated oligosilylgermyl-
potassium compounds very much resembled that of the
Bruker/Siemens area detector absorption and other corrections Version
2.10; Bruker AXS, 1998-2003.

Silylgermylpotassium Compounds
Organometallics, Vol. 24, No. 6, 2005 1267
methods and refined by full-matrix least-squares method
of pentane a colorless low-melting solid was obtained (124 mg,
1
8
1
(
SHELXL97). All non-hydrogen atoms were refined with
95%). NMR (δ in ppm): H (C
6
D
6
): 1.23 (t, 3H, J ) 7.6 Hz);
1
3
anisotropic displacement parameters. All hydrogen atoms were
located in calculated positions to correspond to standard bond
lengths and angles. Crystallographic data can be found in
Table 1. More detailed information for all structures can be
found in the Supporting Information. All data have been
deposited at the Cambridge Crystallographic Deposition Cen-
tre: CCDC 253310 (6b), CCDC 253311 (7b), CCDC 258956
6 6
1.05 (q, 2H, J ) 7.6 Hz); 0.25 (s, 27H). C (C D ): 14.7; 1.9;
2
9
6 6
1.5. Si (C D ): -7.4.
Tris(trimethylsilyl)germylzirconocene Chloride (4).
To a solution of 1 (0.82 mmol) in THF (4 mL) was added
zirconocene dichloride (240 mg, 0.82 mmol). The red color of
the solution turned dark red, and after another 30 min the
solvent was removed in a vacuum, pentane was added, and
insoluble salts were removed by filtration. The product was
crystallized from pentane at -30 °C. Red crystals (378 mg,
(
8). The data can be retrieved via www.ccdc.cam.ac.uk/conts/
retrieving.html or can be ordered at the Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge CB21Ez;
fax: (+44) 1223-336-033.
8
4%) with spectroscopic properties identical to published data
10
1
were obtained. NMR (δ in ppm): H (C
0.40 (s, 27H). Si (C D ): -2.1. Anal. Calcd for C H ClGeSi -
6
D
6
): 6.01 (s, 10H);
29
Elemental analyses were performed with a Heraeus VARIO
ELEMENTAR EL analyzer. No satisfactory elemental analy-
ses of the germyl- and silylpotassium compounds could be
obtained. This is in accordance with our own previous observa-
tions and also those of other authors which report about
6
6
19 37
3
Zr (549.02): C 41.60, H 6.79. Found: C 41.66, H 6.58.
Reaction of 4 (50 mg, 0.09 mmol) with 2,6-dimethylphenyl
isonitrile (13 mg, 0.1 mmol) in C (0.6 mL) proceeded
according to NMR spectroscopy in a quantitative manner to
6
D
6
1
9
similar problems with alkali silyl compounds. Tetrakis-
1
give the isonitrile insertion product. NMR (δ in ppm):
): 6.74 (m, 1H); 6.60 (m, 2H); 5.90 (C ); 2.06 (s, 6H);
): 269.2; 148.4; 129.6; 128.9; 125.7;
): -4.7.
Tris(trimethylsilyl)[tris(trimethylsilyl)silyl]ger-
H
3
20
(
trimethylsilyl)germane, tris(trimethylsilyl)silyl chloride,
(
0
1
C
6
D
6
5 5
H
2
1
and 1,2-dibromotetramethyldisilane have been prepared
following previously published procedures.
13
6 6
.22 (s, 27H). C (C D
10.3; 20.4; 3.6. Si (C D
6 6
29
General Procedure A for the Synthesis of Germyl-
potassium Compounds in THF. To a solution of the respec-
tive silylgermane in THF was added potassium tert-butoxide
mane (5). A solution of 1 in benzene (0.55 mmol) was added
dropwise to a solution of chlorotris(trimethylsilyl)silane (155
mg, 0.55 mmol) in benzene. The mixture was stirred for
another 30 min. The solvent was removed in a vacuum, after
which pentane was added to extract the product. After
filtration and removal of pentane in a vacuum, a yellow solid
(
1 molar equiv). The reaction usually turned yellow im-
mediately and was stirred at room temperature until complete
2
9
conversion was reached (monitored either by Si NMR spec-
troscopy or GC/MS of a derivatized aliquot). The obtained
germylpotassium compound was either used for further reac-
tion as obtained in THF solution or isolated by removal of the
solvent in a vacuum.
was obtained (266 mg, 90%). Mp: 156-160 °C (subl), 280 °C
1
(
dec). NMR (δ in ppm): H (C
6
D
6
): 0.36 (s, 27H); 0.32 (s, 27H).
): -4.9; -9.9; -122.3. Anal. Calcd
(539.83): C 40.05, H 10.08. Found: C 39.82,
13
29
C (C
for C18
H 10.21.
,2-Bis[tris(trimethylsilyl)germyl]tetramethyldi-
6
D
H
6
): 4.9; 4.3. Si (C
6 6
D
General Procedure B for the Synthesis of Germyl-
potassium Compounds in the Presence of 18-crown-6.
To a solution of the respective silylgermane and 18-crown-6
54GeSi
7
1
(
1 or 2 molar equiv for mono- or dianions, respectively) in
silane (6). From a solution of 1 (8.21 mmol) in THF the solvent
was removed in a vacuum and toluene (10 mL) was added.
The solution was cooled to -78 °C, and a solution of 1,2-
dibromotetramethyldisilane (1.16 g, 0.5 equiv, 4.10 mmol) in
toluene (40 mL) was added dropwise. The reaction mixture
was allowed to warm to room temperature and was stirred
overnight. After quenching with dilute sulfuric acid and
extraction with ether, the organic phase was dried over sodium
sulfate and the solvent was removed in a vacuum. White
crystals of pure product were obtained by recrystallization
from acetone at -80 °C (1.90 g, 66%). Mp: 208-213 °C. NMR
toluene or benzene potassium tert-butoxide was added 1 or 2
molar equiv of the germane for mono- or dianions, respectively,
and the reaction was stirred at room temperature until
complete conversion was reached (monitored either by Si
NMR spectroscopy or GC/MS of a derivatized aliquot). The
obtained potassium compound either was used for further
reaction as obtained in solution or in the case of the dianions
precipitates from solution.
2
9
Tris(trimethylsilyl)germylpotassium (1). 1 was pre-
pared as the crown ether adduct according to general proce-
1
dure B. NMR (δ in ppm): H (C
2
6
D
6
): 3.20 (s, 24H); 0.64 (s,
): -3.3.
Tris(trimethylsilyl)germane (2). A solution of 1 in THF
0.27 mmol) was added to an ether/dilute sulfuric acid mixture.
1
13
(
4
δ in ppm): H (C
6
D
6
): 0.36 (s, 54H); 0.57 (s, 12H). C (C
): -5.0; -24.4. Anal. Calcd for C22
(700.63): C 37.71, H 9.49. Found: C 37.11, H 9.36.
6
6
):
8
1
3
29
6 6 6 6
7H). C (C D ): 70.0; 8.1. Si (C D
.2; 2.1. 29Si (C
6
D
6
H
(
Hexakis(trimethylsilyl)digermane (7). 7 was obtained
in a procedure completely analogous to the preparation of 6
using ether instead of toluene as solvent and 1,2-dibromo-
ethane (770 mg, 0.5 equiv, 4.10 mmol) as the electrophilic
component. White crystals of pure product were obtained (1.80
g, 75%). Mp: 167-170 °C (subl), 285 °C (dec). NMR (δ in
After separating the layers, the ether phase was dried over
sodium sulfate and concentrated in a vacuum. The product
(
78 mg, 98%) was obtained as a colorless oil with spectroscopic
3
1
properties identical to published data. NMR (δ in ppm):
(C D ): 2.17 (s, 1H); 0.28 (s, 27H). C (C D ): 2.6. Si (C D ):
6 6 6 6 6 6
H
1
3
29
-
6.5.
Ethyltris(trimethylsilyl)germane (3). A solution of 1
0.41 mmol) in benzene was added dropwise to a benzene
1
13
29
ppm): H (C
5.0. Anal. Calcd for C18
Found: C 37.50, H 9.17.
6
D
6
): 0.39 (s, 54H). C (C
6 6 6 6
D ): 4.7. Si (C D ):
-
H
54Si
6
Ge (584.32): C 36.99, H 9.30.
2
(
solution of ethyl bromide (109 mg, 1.0 mmol). The mixture was
stirred for 15 min, and the solvent was then removed in a
vacuum, after which pentane was added to extract the product.
The mixture was filtered to remove the salts, and after removal
Bis(trimethylsilyl)[tris(trimethylsilyl)silyl]germyl-
potassium 18-Crown-6 (5a). 5a was obtained from 5 (220
mg, 0.41 mmol) according to general procedure B employing
1
1
equiv of potassium tert-butoxide. NMR (δ in ppm):
H
1
3
(
C
6
D
6
): 0.64 (s, 18H); 0.56 (s, 27H). C (C
Si (C ): -5.4; -10.5; -132.2.
Bis(trimethylsilyl)[potassiobis(trimethylsilyl)silyl]-
6
D
6
): 70.3; 9.2; 4.6.
(
18) Sheldrick, G. M. SHELX97 Programs for Crystal Structure
Analysis (Release 97-2); Universit a¨ t G o¨ ttingen, G o¨ ttingen (Germany),
998.
19) Jenkins, D. M.; Teng, W.; Englich, U.; Stone, D.; Ruhlandt-
Senge K. Organometallics 2001, 20, 4600-4606.
29
6
D
6
1
(
germylpotassium 2 × 18-Crown-6 (5b). 5b was obtained
from 5 (220 mg, 0.41 mmol) according to general procedure B
(
20) Gilman, H.; Harrell, R. L. J. Organomet. Chem. 1965, 5, 199-
employing 2 equiv of potassium tert-butoxide. NMR (δ in
2
00.
1
ppm): H (C
6
D
6
): 3.38 (s, 48H); 0.60 (s, 18H); 0.59 (s, 18H).
(21) Ishikawa, M.; Kumada, M.; Sakurai, H. J. Organomet. Chem.
1
3
29
1
970, 23, 63-69.
6 6 6 6
C (C D ): 70.2; 9.3; 8.9. Si (C D ): -4.8; -5.6; -178.0.

1268 Organometallics, Vol. 24, No. 6, 2005
Fischer et al.
1
,1,4,4,4-Pentakis(trimethylsilyl)-2,2,3,3-tetramethyl-
(starting from 0.22 mmol 6) in toluene (3 mL) was added
dropwise to a solution of dimethyltin dichloride (49 mg, 0.22
mmol) in toluene (3 mL). The solution turned deep yellow and
was stirred overnight. After quenching with dilute sulfuric acid
and extraction with ether, the organic phase was dried over
sodium sulfate and the solvent was removed in a vacuum.
White crystals of 8 (131 mg, 87%) were obtained from a
pentane extract at -30 °C. Mp: 104-105 °C. NMR (δ in
2
6
,3-disila-1,4-digermanyl-1-potassium 18-Crown-6 (6a).
a was obtained from 6 (150 mg, 0.22 mmol) according to
general procedure B employing 1 equiv of potassium tert-
6 6
butoxide. NMR (δ in ppm): H (C D ): 3.20 (s, 24H); 0.83 (s,
1
13
6
8
H); 0.74 (s, 6H); 0.65 (s, 18H); 0.49 (s, 27H). C (C
D
6 6
): 69.7;
): -3.5; -5.3; -20.9; -25.1.
,1,4,4-Tetrakis(trimethylsilyl)-2,2,3,3-tetramethyl-2,3-
disila-1,4-digermanyl-1,4-dipotassium 2 × 18-Crown-6
2
9
6 6
.6; 5.2; 4.4; 2.6. Si (C D
1
1
13
6 6
ppm): H (C D ): 0.59 (s, 6H); 0.39 (s, 12H); 0.31 (s, 36H). C
(
6b). 6b was obtained from 6 (150 mg, 0.22 mmol) according
29
2
(
3
C
6
D
6
): 4.3; -1.0; -7.5. Si (C
6
D
6
): -1.0; -16.8 [ J(Si-Sn) )
to general procedure B employing 2 equiv of potassium tert-
butoxide. Yellow crystals of the product precipitated from the
benzene solution rapidly. The crystals were dissolved in a C
THF mixture and subjected to NMR analysis. NMR (δ in
119
0.0 Hz]. Sn (C
6
D
6
): -101.9. Anal. Calcd for C18
H
54Ge
2
6
Si -
Sn (703.06): C 30.75, H 7.74. Found: C 30.75, H 7.78.
6 6
D /
2
,2,5,5-Tetrakis(trimethylsilyl)-3,3,4,4-tetramethyl-1-
zirconocena-2,5-digermacyclopentasilane (9). A solution
of 6b (starting from 0.15 mmol 6) in benzene (3 mL) was added
dropwise to a solution of zirconocene dichloride (43 mg, 0.15
mmol) in benzene (3 mL). The solution turned deep red. The
reaction mixture was stirred overnight, after which the solvent
was removed in a vacuum. Pentane was then added, and the
salts were removed by filtration. After crystallization at -30
1
6 6
ppm): H (C D /THF): 3.40 (s, 48H); 0.44 (s, 12H); 0.49 (s,
1
3
29
1
8H). C (C
Pentakis(trimethylsilyl)digermylpotassium 18-Crown-6
7a). 7a was obtained from 7 (300 mg, 0.51 mmol) according
to general procedure B employing 1 equiv of potassium tert-
6 6 6 6
D ): 70.1; 8.6; 5.3. Si (C D ): -3.4; -22.4.
(
1
butoxide. NMR (δ in ppm): H (C
6 6
D ): 3.19 (s, 24H); 0.67 (s,
8H); 0.62 (s, 27H). 13C (C
29
1
-
6
D
6
): 69.9; 9.0; 5.1. Si (C
6.8.
Tetrakis(trimethylsilyl)digermyl-1,2-dipotassium 2 ×
8-Crown-6 (7b). 7b was obtained from 7 (300 mg, 0.51 mmol)
6 6
D ): -4.9;
°
C, red crystals were obtained (84 mg, 75%). NMR (δ in ppm):
1
13
H (C
): 108.5; 6.8; 4.1. Si (C
for C26 Si
H 7.45.
6 6
D
): 6.32 (s, 10H), 0.39 (s, 12H); 0.35 (s, 36H).
C
2
9
(
C
6
D
6
D
6 6
): -5.0; -24.4. Anal. Calcd
1
H58Ge
2
6
Zr (775.70): C 40.26, H 7.54. Found: C 39.89,
according to general procedure B employing 2 equiv of potas-
sium tert-butoxide. Red crystals of 7b that precipitated from
the benzene solution were dissolved in a C
6
D
6
/THF mixture
/THF): 3.40 (s,
): 70.0; 8.9. Si (C ): -5.3.
,2,5,5-Tetrakis(trimethylsilyl)-1,1,3,3,4,4-hexamethyl-
-stanna-2,5-digermacyclopentasilane (8). A solution of 6b
1
6 6
for NMR analysis. NMR (δ in ppm): H (C D
Supporting Information Available: This material is
available free of charge via the Internet at http://pubs.acs.org.
29
4
8H); 0.42 (s, 36H). 13C (C
D
6 6
6 6
D
2
1
OM0491894