Heavy cyclopropene analogues R4SiGe2 and R4Ge3 (R = SiMetBu2) - New members of the cyclic digermenes family

Article abstract of DOI:10.1016/j.jorganchem.2006.03.049

1H-Siladigermirene R₄SiGe₂ (2a) and 1H-trigermirene R₄Ge₃ (2b) (R = SiMe^tBu₂) with a Ge{double bond, long}Ge double bond were synthesized by the reaction of tetrachlorodigermane RGeCl₂-GeCl₂R with dilithiosilane R₂SiLi₂ and dilithiogermane R₂GeLi₂, respectively. The skeletal Ge{double bond, long}Ge double bond of 2a is trans-bent (51.0(2)°) with a bond distance of 2.2429(6) A?. The reaction of both 2a and 2b with CH₂Cl₂ resulted in the formation of unusual four-membered ring compounds 5a and 5b as a result of a ring expansion reaction. 1H-Trisilirene 7a and 3H-disilagermirene 7b with an Si{double bond, long}Si double bond also smoothly reacted with CH₂Cl₂ to yield the four-membered ring systems 8a and 8b, respectively.

Full text of DOI:10.1016/j.jorganchem.2006.03.049

Journal of Organometallic Chemistry 692 (2007) 10–19
www.elsevier.com/locate/jorganchem
Heavy cyclopropene analogues R4SiGe2 and R4Ge3 (R = SiMetBu2)
– New members of the cyclic digermenes family
*
Vladimir Ya. Lee, Hiroyuki Yasuda, Masaaki Ichinohe, Akira Sekiguchi
Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
Received 23 February 2006; accepted 24 March 2006
Available online 1 September 2006
Abstract
1H-Siladigermirene R4SiGe2 (2a) and 1H-trigermirene R4Ge3 (2b) (R = SiMetBu2) with a Ge@Ge double bond were synthesized by
the reaction of tetrachlorodigermane RGeCl2–GeCl2R with dilithiosilane R2SiLi2 and dilithiogermane R2GeLi2, respectively. The skel-
˚
etal Ge@Ge double bond of 2a is trans-bent (51.0(2)ꢀ) with a bond distance of 2.2429(6) A. The reaction of both 2a and 2b with CH2Cl2
resulted in the formation of unusual four-membered ring compounds 5a and 5b as a result of a ring expansion reaction. 1H-Trisilirene 7a
and 3H-disilagermirene 7b with an Si@Si double bond also smoothly reacted with CH2Cl2 to yield the four-membered ring systems 8a
and 8b, respectively.
ꢁ 2006 Elsevier B.V. All rights reserved.
Keywords: Digermene; Trigermirene; Siladigermirene; Small ring; Ring expansion; X-ray crystallographic analysis
1. Introduction
polycyclic organometallics [3b–k]. The recent fast progress
in the field enabled us to claim the constitution of this new
class of organometallic compounds, heavy cyclopropenes, in
our preceding contribution [4]. However, until now no
other representatives of heteronuclear heavy cyclopropenes
(except for the above-mentioned 3H- and 1H-disilagermi-
renes GeSi2 [3a]) have been synthesized, although these
compounds are expected to possess unusual promising
properties.
In this paper, we present the synthesis, full structural
characterization, and unexpected reactivity of new repre-
sentatives of the heavy cyclopropenes family, heteronuclear
1H-siladigermirene SiGe2 and homonuclear trigermirene
Ge3, both featuring endocyclic Ge@Ge double bonds [5].
The research area of the cyclopropene analogs of hea-
vier group 14 elements of the type cyclo-[R2E0–E(R)@E(R)]
(E, E0 = Si, Ge, Sn; R = bulky silyl substituent) is becom-
ing an increasingly attractive field of modern organometal-
lic chemistry [1]. The major accomplishments in such
chemistry have been made by the research groups of Sekig-
uchi, Kira, and Wiberg, who have reported the synthesis of
heavy cyclopropenes of Si, Ge, and Sn atoms [2]: trigermi-
renes Ge3 [2a–c], trisilirenes Si3 [2d–g], and tristannirene
Sn3 [2h].
In 2000, we prepared the first hybrid compounds con-
taining two different group 14 elements, 3H- and 1H-disila-
germirenes GeSi2 [3a], and studied their particularly
attractive chemistry, a result of the favorable combination
of high ring strain and exceeding reactivity of the endocy-
clic E@E bond, which opened new unprecedented possibil-
ities for the synthesis of a number of novel cyclic and
2. Results and discussion
Our first attempts to synthesize the new hybrid 1H-sila-
digermirene derivative R4SiGe2 (R = SiMetBu2) by the
identical synthetic procedure to that of the previously
reported 3H-disilagermirene R4GeSi2 [3a] were unsuccess-
ful, because it required the preparation of tBu2MeSi–
*
Corresponding author. Tel./fax.: +81 29 853 4314.
E-mail address: sekiguch@staff.chem.tsukuba.ac.jp (A. Sekiguchi).
0022-328X/$ - see front matter ꢁ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.03.049

V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
11
GeX3 (X = Cl, Br) as one of the key starting materials
(Scheme 1). We found that compounds of this type, Bu2-
(p-tolyl)2–Ge(p-tolyl)2–SiMetBu2 (67%). The final dearyla-
t
t
tion–chlorination of Bu2MeSi–Ge(p-tolyl)2–Ge(p-tolyl)2–
MeSi–GeX3, are highly thermally unstable, in marked
contrast to the stable tBu2MeSi–SiBr3, because of the
higher tendency of the former to undergo a-elimination
SiMetBu2 with HCl/AlCl3 provided the desired starting
1,1,2,2-tetrachlorodigermane 1a in 95% yield (Scheme 2).
The corresponding 1,1,2,2-tetrabromodigermane tBu2MeSi
–GeBr2–GeBr2–SiMetBu2 (1b) was also synthesized by the
t
of Bu2MeSiX accompanied by the generation of dihalog-
ermylenes X2Ge: (Scheme 1).
bromination
of
tBu2MeSi–Ge(p-tolyl)2–Ge(p-tolyl)2–
This forced us to develop a new synthetic protocol for
the synthesis of the desired 1H-siladigermirene derivative,
using a 1,1,2,2-tetrahalodigermane unit as a starting
building block for the subsequent design of the endocyclic
Ge@Ge moiety. As such, tBu2MeSi–GeCl2–GeCl2–
SiMetBu2 (1a) was selected as the best candidate. The
synthesis of 1a commenced from the preparation of
(p-tolyl)3GeCl (50%), which was converted to (p-tolyl)3-
GeH (80%) followed by its lithiation and coupling with
tBu2MeSiBr to form tBu2MeSi–Ge(p-tolyl)3 (75%) (Scheme
SiMetBu2 with HBr/AlBr3, albeit in a lower yield of 52%
due to the partial decomposition of 1b at room
temperature.
Taking into account the intrinsic inclination of halosilyl-
germanes >Ge(X)SiR3 to undergo easy a-elimination of
R3SiX to produce germylenes >Ge:, the stability of 1a is
surprising. The composition of 1a was reliably established
with a complete set of spectral and analytical data, and
the crystal structure of 1a was determined by X-ray crystal-
lography (Fig. 1). The Si1–Ge1–Ge1#–Si1# atom chain
has the anticipated all-trans conformation resulting in a
characteristic zigzag shape of the molecule with normal
bond distances. One should note that only a couple of
examples of R3Si–GeCl2–GeCl2–SiR3 type compounds
have been prepared and structurally characterized:
t
2). The reaction of Bu2MeSi–Ge(p-tolyl)3 and an equiva-
lent amount of CF3SO3H followed by subsequent treat-
ment with NH4Cl produced tBu2MeSi–Ge(p-tolyl)2Cl
(84%), which was reacted with Li resulting in the formation
of the tetraaryldigermane derivative tBu2MeSi–Ge
R
R
Ge
Na
2 tBu2MeSiSiBr3 + (tBu2MeSi)2GeCl2
toluene
Si
Si
R
R
3H-disilagermirene R4GeSi2
(R = SiMetBu2)
R
R
Si
Na
2 tBu2MeSiGeX3 + (tBu2MeSi)2SiBr2
toluene
Ge
Ge
R
R
α-elimination
1H-siladigermirene R4SiGe2
(R = SiMetBu2)
tBu2MeSiX + X2Ge:
(X = Cl, Br)
Scheme 1.
1) nBuLi
LiAlH4
(p-tolyl)3GeCl
(p-tolyl)3GeH
80%
tBu2MeSi-Ge(p-tolyl)3
t
2) Bu2MeSiBr
75%
1) CF3SO3H
2) NH4Cl
Li
tBu2MeSi-Ge(p-tolyl)2Cl
84%
tBu2MeSi-Ge(p-tolyl)2-Ge(p-tolyl)2-SiMetBu2
67%
HX / AlX3
tBu2MeSi-GeX2-GeX2-SiMetBu2
(X = Cl, Br)
1a: X = Cl (95%)
1b: X = Br (52%)
Scheme 2.

12
V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
and a second molecule of (tBu2MeSi)2SiLi2 [10], leading
to formation of 2a and 3a in the experimentally observed
2:1 ratio (Scheme 3).
The 1H-siladigermirene 2a is the first representative of
hybrid heavy cyclopropenes of SiGe2 composition featur-
ing a skeletal Ge@Ge double bond; that is, 2a belongs also
to the class of the cyclic digermenes [2a–c,3i]. The NMR
spectra of 2a are rather simple, reflecting its symmetrical
structure: only two sets of signals were observed for both
t
Me and Bu groups in 1H and 13C NMR spectra. The
29Si NMR spectrum revealed three resonances at ꢀ110.6,
5.8, and 40.8 ppm: the most upfield signal at ꢀ110.6 ppm
was in the reasonable range for an sp3-Si atom in the
three-membered ring, whereas the other two signals were
attributed to the substituent Si atoms. The large difference
in the chemical shifts of substituent Si atoms bound to
either skeletal Si (5.8 ppm) or Ge (40.8 ppm) atoms is evi-
dently due to the different hybridization degree of these
skeletal atoms: sp3-Si vs. sp2-Ge.
Fig. 1. Crystal maker view of 1a (hydrogen atoms are not shown).
Selected bond lengths (A): Ge1–Ge1# = 2.448(2), Ge1–Cl1 = 2.205(3),
Ge1–Cl2 = 2.186(3), Si1–Ge1 = 2.447(3). Selected bond angle (ꢀ): Si1–
Ge1–Ge1# = 131.94(10).
˚
(Me3Si)3Si–GeCl2–GeCl2–Si(SiMe3)3 [6] and tBu3Si–
GeCl2–GeCl2–SitBu3 [7]. However, in both these cases the
structural refinement suffered from either disorder [6] or
co-crystallization with other compounds [7].
X-ray crystallography of 2a revealed an isosceles SiGe2
triangle structure, in complete accord with the symmetrical
structure of 2a in solution (vide supra). Both skeletal
The reaction of 1a with 1,1-dilithiosilane (tBu2MeSi)2Si-
Li2 [8] in toluene cleanly resulted in the formation of a cou-
ple of products, the desired tetrakis(di-tert-butylmethylsi-
lyl)-1H-siladigermirene (tBu2MeSi)4SiGe2 (2a) (26%) and
tetrakis(di-tert-butylmethylsilyl)disilene (tBu2MeSi)2Si@Si-
(SiMetBu2)2 (3a) [9] in a 2:1 ratio (Scheme 3).
˚
Ge@Ge (2.2429(6) A) as well as Si–Ge (2.4168(10) and
˚
2.4165(10) A) bond lengths are typical for the heavy cyclo-
propene systems [1] (Fig. 2). As was expected for digerm-
enes [11], the Ge@Ge bond in 2a is highly trans-bent with
the Si4–Ge1–Ge2–Si5 torsional angle of 51.0(2)ꢀ.
Using dilithiogermane (tBu2MeSi)2GeLi2 [12] instead of
1,1-dilithiosilane (tBu2MeSi)2SiLi2, we synthesized
a
Interestingly, among several possible products of this
reaction, namely 1,4-disila-2,3-digermabuta-1,3-diene, 2,4-
disila-1,3-digermabicyclo[1.1.0]butane, and 1H-siladiger-
mirene, only the last compound was formed. The two com-
pounds, dark-red 1H-siladigermirene 2a and deep-blue
disilene 3a [9], were separated by column chromatography
(SiO2, hexane) in a glovebox followed by recrystallization
from pentane. The possible reaction pathway might include
the initial formation of 2,3-dichlorosiladigermirane (4a)
followed by the fast Li–Cl exchange reaction between 4a
germanium analogue of 2a, a novel trigermirene derivative
tetrakis(di-tert-butylmethylsilyl)-1H-trigermirene (2b)
(22%) by the reaction of (tBu2MeSi)2GeLi2 and 1a in tolu-
ene (Scheme 3). Quite similar to the case of 1H-siladigermi-
rene 2a, the formation of 2b was accompanied with the
production of half an equivalent of digermene (tBu2MeSi)2-
Ge@Ge(SiMetBu2)2 (3b). Both products were separated
employing the same experimental procedure: column
chromatography in a glove-box followed by the recrystalli-
R
R
E
toluene
RGeCl2GeCl2R + 2 R2ELi2
+ 1/2 R2E=ER2
Ge
Ge
-LiCl
3a: E = Si
3b: E = Ge
R
R
E = Si, Ge
R = SiMetBu2
2a: E = Si; 2b: E = Ge
R2ELi2
-LiCl
R
-LiCl
x 2 -LiCl
+ R2E(Li)Cl
R
R
R
E
R2ELi2
E
Cl
R
R
Li
R
R
Ge
Ge
Li-Cl exchange
Ge
Ge
Cl
Cl
4a: E = Si; 4b: E = Ge
Scheme 3.

V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
13
ing from each other only by the skeletal atoms (Si or Ge,
or their combinations) (Fig. 3).
Comparing the structures of 2a and 7a (or 2b and 7b),
one can easily recognize that the Ge@Ge bond is more
trans-bent than the Si@Si bond in both cases: 51.0(2)ꢀ vs.
31.9(2)ꢀ (or 60.5(2)ꢀ vs. 37.0(2)ꢀ), which is quite normal
because of the well-known tendency for increasing trans-
bending on descending a group 14 [11]. On the other hand,
comparing cyclic digermenes 2a and 2b (or cyclic disilenes
7a and 7b), another tendency becomes apparent: the trans-
bending of the same bond Ge@Ge (or Si@Si) is more pro-
nounced when the sp3-skeletal atom is Ge but not Si. This
should be ascribed to the immediate influence of the elec-
tronegativity difference of Si and Ge atoms (Ge is more
electronegative), because the electronegative substituents
R increase the pyramidalization degree of doubly-bonded
atoms E (E = heavier group 14 element) in compounds of
the type R2E = ER2 [11]. Thus, 1H-trigermirene 2b should
be recognized as the most highly trans-bent (60.5(2)ꢀ)
heavy cyclopropene known to date.
Fig. 2. Crystal maker view of 2a (hydrogen atoms are not shown).
Selected bond lengths (A): Ge1–Ge2 = 2.2429(6), Si3–Ge1 = 2.4168(10),
Si3–Ge2 = 2.4165(10), Ge1–Si4 = 2.3995(11), Ge2–Si5 = 2.3943(11), Si3–
Si6 = 2.3993(13), Si3–Si7 = 2.4033(13). Selected bond angles (ꢀ): Ge2–
Ge1–Si3 = 62.34(11), Ge1–Ge2–Si3 = 62.36(3), Ge1–Si3–Ge2 = 55.30(2).
Torsional angle (ꢀ): Si4–Ge1–Ge2–Si5 = 51.0(2).
˚
Apart from their particular structures, both 2a and 2b
exhibited an interesting reactivity toward halogenated
hydrocarbons, especially CH2Cl2. Thus, both 2a and 2b
smoothly reacted with an excess of dry CH2Cl2 to form
unexpected products, trans-2,4-dichloro-1,1,2,4-tetra-
kis(di-tert-butylmethylsilyl)-1,2,4-siladigermetane (5a) and
trans-1,3-dichloro-1,2,2,3-tetrakis(di-tert-butylmethylsilyl)-
1,2,3-trigermetane (5b), respectively, as the result of the
ring enlargement reaction (Scheme 4). Both 5a and 5b were
isolated in 71% and 69% yield and fully characterized by
spectral and crystallographic data. The most diagnostic
feature of both 5a and 5b was the markedly low-field sig-
nals of the methylene unit of the four-membered ring:
2.79 and 2.98 ppm (1H NMR spectrum), 42.6 and
44.9 ppm (13C NMR spectrum). Such an observation is in
evident contrast to other known cyclobutane derivatives
featuring the RR0Si–CH2–SiRR0– fragment, which charac-
zation from pentane to afford dark-red crystals of 2b and
deep-blue crystals of the previously unknown digermene
3b [13]. The 1H-trigermirene 2b was completely isostruc-
tural to 1H-siladigermirene 2a crystallizing in the same
monoclinic P21/c space group with very similar bond dis-
tances and bond angles [14]. However, the degree of
trans-bending of Ge@Ge double bond in 2b is more
pronounced than that in 2a: 60.5(2)ꢀ vs. 51.0(2)ꢀ. From this
structural viewpoint, the comparison of both 2a and 2b
with 1H-trisilirene (tBu2MeSi)4Si3 (7a) [2e] and 3H-disila-
germirene (tBu2MeSi)4GeSi2 (7b) [3a] (both previously
synthesized by us) is particularly instructive, because all
these compounds have the same substituents, distinguish-
1
teristically exhibit the H NMR resonances of methylene
SiR3
SiR3
R3Si
R3Si
51.0(2)o
Ge
60.5(2)o
Ge
Si
Ge
Ge
Ge
SiR3
SiR3
R3Si
R3Si
2a
2b
R3Si
R3Si
SiR3
SiR3
Si
37.0(2)o
Si
31.9(2)o
Si
Ge
Si
Si
SiR3
SiR3
R3Si
R3Si
7a
7b
R3Si = SiMetBu2
Fig. 3. Schematic representation of heavy cyclopropene analogs 2a, 2b, 7a, 7b and torsional angles.

14
V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
R
R
R
R
R
R
E
E
E
R
Cl
R
hexane
R
Cl
R
+ CH2Cl2
Ge
Ge
Ge
Ge
Ge
Ge
Cl
Cl
R
R
C
CH2
H2
2a: E = Si
2b: E = Ge
5a: E = Si; 5b: E = Ge
6a: E = Si; 6b: E = Ge
R = SiMetBu2
Scheme 4.
protons in the high-field region of 0.18–0.89 ppm [15]. Such
a remarkable spectral feature of 5a and 5b might be attrib-
uted to the hyperconjugative mixing of r(C–H)–r*(Ge–Cl)
orbitals, definitely resulting in the deshielding of both H
and C nuclei of the CH2-moiety.
rings 2a and 2b is of particular interest. Although we
do not have direct spectroscopic evidence for formation
of any detectable intermediates, we can suggest the fol-
lowing reaction scheme. The initial 1,2-addition of
CH2Cl2 across the Ge@Ge double bond to form the inter-
mediate cyclopropane derivatives 6a, 6b can be assumed
as the reasonable first step of the reaction. The analogous
1,2-addition of the simple chloroalkanes (CH2Cl2, CHCl3,
CCl4) to the stable tetrasilyldisilenes [17a] and transient
digermenes [17b,c] has been recently reported. The next
step of the reaction is assumed to be a formal intramolec-
ular insertion of the CH2-unit into the skeletal Ge–Ge
bond accompanied by the migration of Cl atom from C
to Ge. One of the evident driving forces for the ring
expansion step should be release of the ring strain on
going from a three- to a four-membered ring. Indeed,
our calculations at the B3LYP/6-31G(d) level of theory
with the GAUSSIAN 98 program package on the model
compounds 5a, 5b (R = SiH3) revealed that the final
four-membered rings 5a and 5b are much more stable
than the transient three-membered rings 6a and 6b by
41.7 and 41.8 kcal/mol, respectively.
The crystal structure analysis of 5a disclosed a folded
SiGe2C-four-membered ring (folding angle 33ꢀ) with the
trans-arrangement of the two Cl atoms bound to the
skeletal Ge atoms. The skeletal Si–Ge bonds of 2.475(2)
˚
and 2.547(3) A significantly exceeded the normal values
˚
of Si–Ge bond distances (2.384–2.462 A [16]), which was
explained by the great steric congestion around the Ge1–
Si2–Ge3 fragment of the cyclic skeleton (Fig. 4). The
˚
exocyclic Ge–Cl bonds of 2.229(2) and 2.236(2) A are con-
˚
siderably longer than the typical values of 2.08–2.15 A [16],
a fact that can also be taken as another manifestation of
the r(C–H)–r*(Ge–Cl) hyperconjugative interaction.
The mechanism for the formation of the four-mem-
bered rings 5a and 5b starting from the three-membered
We found that the ring expansion reaction with CH2Cl2
is general for all heavy cyclopropenes of the type
0
t
ð Bu2MeSiÞ4EE2 (E, E0 = Si, Ge). Thus, 1H-trisilirene 7a
and 3H-disilagermirene 7b (previously prepared by us) also
smoothly reacted with CH2Cl2 to yield the four-membered
ring systems 8a and 8b, totally isostructural to the above
described 5a and 5b (Scheme 5). The new compounds 8a
and 8b were isolated in a pure form and characterized by
NMR spectral and X-ray crystallography data.
It should be noted that CH2Cl2 is quite a unique reagent
toward 2 and 7 to give the ring enlargement products.
Thus, CCl4 reacted with both 2a and 2b to produce the cor-
responding dichlorocyclopropane derivatives, trans-2,
3-dichloro-1,1,2,3-tetrakis(di-tert-butylmethylsilyl)siladi-
germirane (9a) and trans-1,2-dichloro-1,2,3,3-tetrakis(di-
tert-butylmethylsilyl)trigermirane (9b), respectively, instead
of the four-membered ring compounds (Scheme 6). That is,
carbon tetrachloride in these reactions acts purely as a
chlorinating reagent.
Fig. 4. Crystal maker view of 5a (hydrogen atoms are not shown). Selected
˚
bond lengths (A): Si2–Ge1 = 2.547(3), Si2–Ge3 = 2.475(2), Ge1–C1 =
The striking difference in the reactivity of CH2Cl2 and
CCl4 toward the Ge@Ge double bond of 2a and 2b might
be caused by the greater steric bulk of the ÆCCl3 radical
compared with that of the ÆCH2Cl radical, which precludes
1.998(10), Ge3–C1 = 1.956(10), Ge1–Cl1 = 2.229(2), Ge3–Cl2 = 2.236(2),
Ge1–Si5 = 2.443(3), Ge3–Si8 = 2.490(3), Si2–Si6 = 2.449(4), Si2–Si7
= 2.450(4). Selected bond angles (ꢀ): Ge1–Si2–Ge3 = 73.88(6), Si2–Ge3–
C1 = 90.0(3), Ge3–C1–Ge1 = 99.5(4), C1–Ge1–Si2 = 87.0(3).

V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
15
R
R
R
R
E
E
R
Cl
R
hexane
+
CH2Cl2
Si
Si
Si
Si
Cl
R
R
CH2
7a: E = Si
7b: E = Ge
8a: E = Si
8b: E = Ge
R = SiMetBu2
Scheme 5.
(700 ml)] was slowly added to the solution of GeCl4
(105.2 g, 0.49 mol) in THF (600 ml) over a period of 2 h
at 0 ꢀC. Then the temperature was raised to room temper-
ature and the reaction mixture was refluxed overnight.
THF (600 ml) was distilled off and dry hexane (600 ml)
was added. After the usual work-up (filtration, evapora-
tion of solvents) the residue was recrystallized from hex-
ane to give (p-tolyl)3GeCl as a colorless solid (93.8 g,
R
R
R
R
E
E
hexane
+ CCl4
R
Cl
R
Ge
Ge
Ge
Ge
R
R
Cl
2a: E = Si
2b: E = Ge
9a: E = Si; 9b: E = Ge
1
R = SiMetBu2
50%). H NMR (C6D6) d 2.30 (s, 9H, Me–C6H4–), 6.99
(d, 3J = 7.5 Hz, 6H, Harom), 7.66 (d, 3J = 7.5 Hz, 6H,
Scheme 6.
H
arom); 13C NMR (C6D6) d 21.4, 129.7, 132.3, 134.6,
140.6.
the formation of the CCl3-adduct. The same reaction
course was previously observed in the reaction of 1H-trisil-
irene 7a and 3H-disilagermirene 7b with CCl4, resulting in
the quantitative formation of dichloro derivatives analo-
gous to 9a, b [3c]. The reaction of both 2a and 2b with
CHCl3 produced complicated reaction mixtures, probably
due to the operation of several competing reaction
pathways.
3.3. Synthesis of (p-tolyl)3GeH
A solution of (p-tolyl)3GeCl (61.5 g, 0.16 mol) in Et2O
(400 ml) was slowly added to a suspension of LiAlH4
(6 g, 0.16 mol) in Et2O (200 ml), and the reaction mixture
was refluxed for 4 h. After usual water work-up, (p-tolyl)3-
GeH was isolated by Kugelrohr distillation as a colorless
1
solid (45.0 g, 80%). H NMR (C6D6) d 2.09 (s, 9H, Me–
C6H4–), 5.93 (s, 1H, Ge–H), 7.02 (d, 3J = 7.5 Hz, 6H,
3. Experimental
H
arom), 7.54 (d, 3J = 7.5 Hz, 6H, Harom); 13C NMR
(C6D6) d 21.4, 129.6, 132.8, 135.6, 139.0.
3.1. General procedures
t
3.4. Synthesis of Bu2MeSi–Ge(p-tolyl)3
All experiments were carried out using high-vacuum line
techniques or in an argon atmosphere of MBRAUN MB
150B-G glove box. The solvents were predried over sodium
benzophenone ketyl and finally dried and degassed over
potassium mirror in vacuum immediately prior to use.
NMR spectra were recorded on Bruker AC-300FT
NMR (1H NMR at 300.13 MHz; 13C NMR at 75.47
MHz; 29Si NMR at 59.63 MHz) and Bruker ARX-400FT
NMR (1H NMR at 400.23 MHz; 13C NMR at 100.64
MHz; 29Si NMR at 79.52 MHz) spectrometers. MS spectra
were measured on Shimadzu GCMS-QP5000 instrument
and on JEOL JMS SX-102 instrument. UV-spectra were
recorded on Shimadzu UV-3150 UV–Vis spectrophotome-
ter in hexane.
n
A 1.6 M solution of BuLi in hexane (82 ml, 0.13 mol)
was slowly added to a solution of (p-tolyl)3GeH (45.0 g,
0.13 mol) in Et2O (250 ml), and the reaction mixture was
stirred for 1 h at room temperature. The resulting solu-
tion of (p-tolyl)3GeLi in Et2O was added dropwise to
t
the solution of Bu2MeSiBr (31.4 g, 0.13 mol) in THF
(250 ml), and the reaction mixture was stirred overnight
at room temperature. After usual water work-up,
tBu2MeSi–Ge(p-tolyl)3 was isolated by Kugelrohr
distillation as
a colorless solid (52.4 g, 80%). Bp
200–220 ꢀC/0.2 mmHg, mp 106–107 ꢀC; 1H NMR
t
(C6D6) d 0.49 (s, 3H, Me), 1.07 (s, 18H, Bu), 2.09 (s,
9H, Me–C6H4–), 7.05 (d, 3J = 7.5 Hz, 6H, Harom), 7.74
(d, 3J = 7.5 Hz, 6H, Harom); 13C NMR (C6D6) d 4.69,
21.3, 21.8, 30.0, 129.3, 136.5, 137.6, 137.9; 29Si NMR
3.2. Synthesis of (p-tolyl)3GeCl
(C6D6) d 11.6; MS (m/z): 504 (M+), 447 (M+ꢀ Bu),
t
A solution of p-tolylMgCl [prepared from p-tolylCl
(192.0 g, 1.51 mol) and Mg (36.50 g, 1.5 mol) in THF
347 (M+ꢀSiMetBu2).

16
V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
t
3.5. Synthesis of Bu2MeSi–Ge(p-tolyl)2Cl
complete in 10 h at room temperature. Then solvent was
evaporated, dry hexane was added to the residue and the
resulting suspension was filtered through Celite. After
CF3SO3H (5.3 ml) was slowly added to the solution of
tBu2MeSi–Ge(p-tolyl)3 (30 g, 59.5 mmol) in CH2Cl2
(150 ml) at 0 ꢀC. The reaction was complete in 1 h, then
the fine powder of dry NH4Cl (32 g, 598 mmol) was
added at room temperature, and the reaction mixture
was stirred for 54 h. Then excess of NH4Cl was filtered
t
evaporation of hexane Bu2MeSi–GeBr2–GeBr2–SiMetBu2
was obtained as a white solid (0.15 g, 52%). Mp 74–
1
79 ꢀC; H NMR (C6D6) d 0.52 (s, 6H, Me), 1.19 (s, 36H,
tBu); 13C NMR (C6D6) d ꢀ4.7, 23.7, 29.5; 29Si NMR
(C6D6) d 43.7.
t
off and CH2Cl2 was evaporated. Bu2MeSi–Ge(p-tolyl)2Cl
was isolated by Kugelrohr distillation as a colorless oil
3.9. Synthesis of tetrakis(di-tert-butylmethylsilyl)-1H-
siladigermirene (tBu2MeSi)4SiGe2 (2a)
(22.4 g, 84%). Bp 150–170 ꢀC/0.07 mmHg; 1H NMR
t
(C6D6) d 0.45 (s, 3H, Me), 1.03 (s, 18H, Bu), 2.03 (s,
3
6H, Me–C6H4–), 7.01 (d, J = 8 Hz, 4H, Harom), 7.81 (d,
A mixture of (tBu2MeSi)2SiLi2 [prepared from 1,1-
bis(di-tert-butylmethylsilyl)-2,3-bis(trimethylsilyl)-1-silacy-
cloprop-2-ene (500 mg, 0.98 mmol) and Li (35 mg,
5.0 mmol) in THF (4 ml)] and 1a (200 mg, 0.33 mmol)
was placed in a reaction tube with a magnetic stirring
bar. Dry oxygen-free toluene (4 ml) was introduced by vac-
uum transfer, and the dark-green reaction mixture was stir-
red for 1 h at room temperature. After evaporation of
solvent and filtration of inorganic salts, the reaction mix-
ture was separated by column chromatography on silica
gel (hexane eluent) in a glove box, followed by the recrys-
tallization from pentane at ꢀ30 ꢀC to produce pure 2a as
dark-red crystals (68 mg, 26%). Mp 193–195 ꢀC; 1H
NMR (C6D6) d 0.43 (s, 6H, Me), 0.53 (s, 6H, Me), 1.21
3J = 8 Hz, 4H, Harom); 13C NMR (C6D6) d 6.2, 21.3,
21.8, 29.4, 129.6, 134.0, 137.9, 139.2; 29Si NMR (C6D6)
d
16.1; MS (m/z): 448 (M+), 413 (M+ꢀCl), 291
(M+ꢀSiMetBu2).
t
3.6. Synthesis of Bu2MeSi–Ge(p-tolyl)2–Ge(p-tolyl)2–
SiMetBu2
A
solution of tBu2MeSi–Ge(p-tolyl)2Cl (22.4 g,
50 mmol) in THF (150 ml) was added to the suspension
of Li (710 mg, 101 mmol) in THF (50 ml), and the reaction
mixture was refluxed overnight. After usual work-up the
solvent was evaporated, and the residue was recrystallized
t
t
t
from toluene to give Bu2MeSi–Ge(p-tolyl)2–Ge(p-tolyl)2–
(s, 36H, Bu), 1.30 (s, 36H, Bu); 13C NMR (C6D6) d
ꢀ3.9, ꢀ2.1, 22.8, 23.4, 29.8, 31.2; 29Si NMR (C6D6)
ꢀ110.6 (skeletal Si), 5.8 and 40.8 (substituent Si); UV (hex-
ane) kmax nm (e) 236 (21800), 311 (2400), 403 (1000), 470
(1200); Anal. Found: C, 54.06; H, 10.33. Calc. for
C36H84Ge2Si5: C, 53.87; H, 10.55%.
SiMetBu2 as a colorless solid (13.8 g, 67%). Mp 235–
238 ꢀC; 1H NMR (C6D6) d 0.18 (s, 6H, Me), 0.95 (s,
t
3
36H, Bu), 2.16 (s, 12H, Me–C6H4–), 7.11 (d, J = 7.7 Hz,
8H, Harom), 7.91 (d, J = 7.7 Hz, 8H, Harom); 13C NMR
3
(C6D6) d ꢀ4.0, 21.4, 23.0, 30.3, 128.7, 137.7, 137.9, 138.1;
29Si NMR (C6D6) d 19.3.
3.10. Synthesis of tetrakis(di-tert-butylmethylsilyl)-1H-
trigermirene (tBu2MeSi)4Ge3 (2b)
t
3.7. Synthesis of Bu2MeSi–GeCl2–GeCl2–SiMetBu2 (1a)
t
Dry gaseous HCl was bubbled into a solution of Bu2-
Compound 2b was prepared by the procedure analogues
to that of 2a, starting from (tBu2MeSi)2GeLi2 [prepared
from 1,1-bis(di-tert-butylmethylsilyl)-2,3-bis(trimethylsi-
lyl)-1-germacycloprop-2-ene (200 mg, 0.36 mmol) and Li
(20 mg, 2.86 mmol) in a mixture of solvents THF
(0.3 ml) + Et2O (1.2 ml)] and 1a (83 mg, 0.14 mmol) in tol-
uene (1.5 ml). 2b was isolated as dark-red crystals (75 mg,
22%). Mp 188–190 ꢀC; 1H NMR (C6D6) d 0.46 (s, 6H,
MeSi–Ge(p-tolyl)2–Ge(p-tolyl)2–SiMetBu2 (5.5 g, 6.66
mmol) in benzene (70 ml), containing AlCl3 (200 mg,
1.49 mmol). Reaction progress was monitored by 1H
NMR spectroscopy, which showed that the reaction was
complete in 1 h at room temperature. The solvent was then
evaporated, dry hexane was added to the residue, and the
resulting suspension was filtered through Celite. After
evaporation of hexane Bu2MeSi–GeCl2–GeCl2–SiMetBu2
Me), 0.54 (s, 6H, Me), 1.23 (s, 36H, Bu), 1.29 (s, 36H,
t
t
was obtained as a white solid (3.8 g, 95%). Mp 92–95 ꢀC;
tBu); 13C NMR (C6D6) d ꢀ3.8, ꢀ1.9, 22.7, 23.7, 29.8,
31.0; 29Si NMR (C6D6) d 17.0 and 39.1 (substituent Si);
UV (hexane) kmax nm (e) 234 (13600), 324 (2400), 407
(700), 457 (700); Anal. Found: C, 50.71; H, 9.77. Calc.
for C36H84Ge3Si4: C, 51.04; H, 9.99%.
t
1H NMR (C6D6) d 0.45 (s, 6H, Me), 1.14 (s, 36H, Bu);
13C NMR (C6D6) d ꢀ6.1, 22.9, 29.2; 29Si NMR (C6D6) d
42.6.
t
3.8. Synthesis of Bu2MeSi–GeBr2–GeBr2–SiMetBu2 (1b)
3.11. Synthesis of trans-2,4-dichloro-1,1,2,4-tetrakis(di-tert-
butylmethylsilyl)-1,2,4-siladigermetane (5a)
t
Dry gaseous HBr was bubbled into a solution of Bu2-
MeSi–Ge(p-tolyl)2–Ge(p-tolyl)2–SiMetBu2 (0.3 g, 0.36
mmol) in benzene (10 ml), containing AlBr3 (60 mg,
0.22 mmol). The reaction progress was monitored by H
NMR spectroscopy, which showed that the reaction was
1H-siladigermirene 2a (244 mg, 0.30 mmol) was placed
in a reaction tube and dry oxygen-free hexane (1 ml) and
CH2Cl2 (1 ml) were introduced by vacuum transfer, then
1

V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
17
t
the reaction mixture was stirred for 3 h at room temper-
ature. After the evaporation of solvents the residue was
recrystallized from pentane to give 5a as colorless crys-
(s, 6H, Me), 0.75 (s, 6H, Me), 1.21 (s, 36H, Bu), 1.23 (s,
18H, Bu), 1.28 (s, 18H, Bu), 2.35 (s, 2H, CH2); 13C
NMR (C6D6) d ꢀ5.2, 1.8, 22.3, 22.9, 23.3, 23.7, 30.1,
30.3, 31.3, 31.9, 32.7 (CH2); 29Si NMR (C6D6) d 10.3,
30.2, 32.5 (skeletal Si).
t
t
1
tals (183 mg, 71%). Mp 152–154 ꢀC; H NMR (C6D6) d
t
0.46 (s, 6H, Me), 0.79 (s, 6H, Me), 1.20 (s, 18H, Bu),
1.21 (s, 18H, tBu), 1.24 (s, 18H, tBu), 1.31 (s, 18H,
tBu), 2.79 (s, 2H, CH2); 13C NMR (C6D6) d ꢀ4.8, 1.1,
22.5, 23.1, 23.5, 24.3, 29.8, 30.0, 31.4, 31.8, 42.6 (CH2),
29Si NMR (C6D6) d 21.5 (skeletal Si), 28.6, 30.7; Anal.
Found: C 49.81, H 9.82. Calc. for C37H86Cl2Ge2Si5: C
50.07, H 9.77%.
3.15. Synthesis of trans-2,3-dichloro-1,1,2,3-tetrakis(di-tert-
butylmethylsilyl)siladigermirane (9a)
1H-siladigermirene 2a (50 mg, 0.062 mmol) was
reacted with an excess of dry CCl4 (0.5 ml). Reaction
immediately occurred upon melting of CCl4, and the
color of the reaction mixture was changed from dark-
red to yellow. 9a was isolated by the recrystallization
from hexane as yellow crystals (38.7 mg, 71%). Mp
3.12. Synthesis of trans-1,3-dichloro-1,2,2,3-tetrakis(di-tert-
butylmethylsilyl)-1,2,3-trigermetane (5b)
1
Trigermirene 2b (100 mg, 0.12 mmol) was placed in a
reaction tube and dry oxygen-free hexane (0.5 ml) and
CH2Cl2 (0.5 ml) were introduced by vacuum transfer,
then the reaction mixture was stirred for 3 h at room
temperature. After the evaporation of solvents the residue
was recrystallized from pentane to give 5b as colorless
crystals (68 mg, 69%). Mp 149–152 ꢀC; 1H NMR
(C6D6) d 0.46 (s, 6H, Me), 0.84 (s, 6H, Me), 1.201 (s,
131–133 ꢀC (dec.); H NMR (C6D6) d 0.50 (s, 6H, Me),
t
t
0.57 (s, 6H, Me), 1.27 (s, 18H, Bu), 1.29 (s, 18H, Bu),
1.31 (s, 18H, tBu), 1.35 (s, 18H, tBu); 13C NMR
(C6D6) d ꢀ2.8, 2.5, 22.8, 23.7, 23.8, 24.1, 29.9, 30.1,
30.9, 31.4; 29Si NMR (C6D6) d ꢀ83.0, 26.0, 39.1.
3.16. Synthesis of trans-1,2-dichloro-1,2,3,3-tetrakis(di-tert-
butylmethylsilyl)trigermirane (9b)
t
t
t
18H, Bu), 1.203 (s, 18H, Bu), 1.23 (s, 18H, Bu), 1.30
(s, 18H, Bu), 2.98 (s, 2H, CH2); 13C NMR (C6D6) d
Trigermirene 2b (50 mg, 0.059 mmol) was reacted with
an excess of dry CCl4 (0.5 ml). Reaction immediately
occurred upon melting of CCl4, and the color of the reac-
tion mixture was changed from dark-red to yellow. 9b
was isolated by the recrystallization from hexane as yellow
t
ꢀ4.9, 1.3, 22.9, 23.3, 23.5, 24.2, 29.8, 30.0, 31.2, 31.6,
44.9 (CH2); 29Si NMR (C6D6) d 27.7, 31.0; Anal. Found:
C 47.74, H 9.32. Calc. for C37H86Cl2Ge3Si4: C 47.68, H
9.30%.
1
crystals (35.2 mg, 65%). Mp 125–127 ꢀC (dec.); H NMR
3.13. Synthesis of trans-1,3-dichloro-1,2,2,3-tetrakis(di-tert-
butylmethylsilyl)-1,2,3-trisiletane (8a)
(C6D6) d 0.49 (s, 6H, Me), 0.63 (s, 6H, Me), 1.26 (s, 18H,
t
t
tBu), 1.30 (s, 36H, 2 Bu), 1.35 (s, 18H, Bu); 13C NMR
(C6D6) d ꢀ3.1, 2.6, 23.2, 23.6, 24.0, 24.1, 29.9, 30.0, 30.7,
31.3; 29Si NMR (C6D6) d 35.6, 36.9.
Trisilirene 7a (500 mg, 0.702 mmol) was placed in a
reaction tube and dry oxygen-free hexane (1 ml) and
CH2Cl2 (1 ml) were introduced by vacuum transfer, then
the reaction mixture was stirred for 4 h at room temper-
ature. After the evaporation of solvents the residue was
recrystallized from pentane to give 8a as colorless crys-
3.17. Crystal structure analyses of the compounds 1a, 2a and
5a
The single crystals of compounds 1a, 2a and 5a for
X-ray diffraction study were grown from the saturated hex-
ane solutions. Diffraction data were collected at 120 K on a
Mac Science DIP2030 Image Plate Diffractometer with a
rotating anode (50 kV, 90 mA) employing graphite-mono-
1
tals (420 mg, 75%). Mp 161–163 ꢀC; H NMR (C6D6) d
t
0.41 (s, 6H, Me), 0.71 (s, 6H, Me), 1.22 (s, 36H, Bu),
1.24 (s, 18H, tBu), 1.35 (s, 18H, tBu), 2.20 (s, 2H,
CH2); 13C NMR (C6D6) d ꢀ5.0, 1.6, 22.6 (2C), 22.9,
23.8, 30.2, 30.4, 31.0 (CH2), 31.7, 32.0; 29Si NMR
(C6D6) d ꢀ16.8 (skeletal Si), 11.2, 21.5, 31.0 (skeletal
Si–Cl).
˚
chromatized Mo-Ka radiation (k = 0.71070 A). The
structures were solved by the direct method, using SIR-92
program [18], and refined by the full-matrix least-squares
method by SHELXL-97 program [19]. The crystal data and
experimental parameters for the X-ray analysis of 1a, 2a,
and 5a are listed in Table 1. Crystallographic data of 1a,
2a and 5a have been deposited with the Cambridge
Crystallographic Data Centre: CCDC No. 298969 (1a),
CCDC No. 273374 (2a) and CCDC No. 273375 (5a).
Copies of this information may be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html or from the
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: +44 1223 336033; e-mail: deposit@ ccdc.cam.
ac.uk).
3.14. Synthesis of trans-1,3-dichloro-1,2,2,3-tetrakis(di-tert-
butylmethylsilyl)[1,3,2]disilagermetane (8b)
3H-disilagermirene 7b (500 mg, 0.660 mmol) was placed
in a reaction tube and dry oxygen-free hexane (1 ml) and
CH2Cl2 (1 ml) were introduced by vacuum transfer, then
the reaction mixture was stirred for 4 h at room tempera-
ture. After the evaporation of solvents the residue was
recrystallized from pentane to give 8b as colorless crystals
1
(392 mg, 70%). Mp 157–159 ꢀC; H NMR (C6D6) d 0.40

18
V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
Table 1
Crystallographic data and experimental parameters for the crystal structure analysis of 1a, 2a and 5a
1a
2a
5a
Empirical formula
Formula mass (g molꢀ1
C18H42Cl4Ge2Si2
601.68
C36H84Ge2Si5
802.66
C37H86Cl2Ge2Si5
887.59
)
Collection temperature (K)
k (Mo-Ka) (A)
Crystal system
Space group
120
0.71070
Monoclinic
P 21/n
120
120
˚
0.71070
Monoclinic
P 21/c
0.71070
Monoclinic
Cc
Unit cell parameters
˚
a (A)
7.925(3)
14.864(3)
12.013(5)
90
94.091(16)
90
1411.5(8)
2
1.416
24.1020(6)
11.6190(9)
17.7300(16)
90
110.206(4)
90
4659.6(6)
4
1.144
23.1270(16)
12.4550(14)
17.8730(19)
90
109.567(6)
90
4850.9(8)
4
1.215
˚
b (A)
˚
c (A)
a (ꢀ)
b (ꢀ)
c (ꢀ)
3
˚
V (A )
Z
Dcalc (g cmꢀ3
l (mmꢀ1
F(000)
)
)
2.597
620
1.440
1736
1.496
1904
Crystal dimensions (mm)
h Range (ꢀ)
0.30 · 0.01 · 0.01
2.18–28.05
0 6 h 6 10
0 6 k 6 18
ꢀ15 6 l 6 15
13749
0.30 · 0.25 · 0.05
2.14–28.00
ꢀ31 6 h 6 29
ꢀ15 6 k 6 0
0 6 l 6 22
44850
0.15 · 0.10 · 0.02
2.06–28.02
0 6 h 6 30
0 6 k 6 16
ꢀ23 6 l 6 22
24669
Index ranges
Collected reflections
Independent reflections
Rint
3039
0.1470
10257
0.0620
5764
0.0970
Reflections used
Parameters
3039
119
1.069
0.1235/0.0000
0.0817
0.2547
0.994/ꢀ1.237
10257
389
1.008
0.0967/3.3310
0.0544
0.1611
1.087/ꢀ1.224
5764
416
0.999
0.0821/0.0000
0.0580
0.1548
0.756/ꢀ0.936
Sa
Weight parameters a/bb
c
R1 [I > 2r(I)]
d
wR2 (all data)
ꢀ3
˚
Maximum/minimum residual electron density (eA
)
P
S ¼ f ½wðF 20 ꢀ F 2cÞ ꢁ=ðn ꢀ pÞg0:5, n = no. of reflections; p = no. of parameters.
2
a
b
c
2
w ¼ 1=½r2ðF 20Þ þ ðaPÞ þ bPꢁ, with P ¼ ðF 02 þ 2F 2cÞ=3.
P
P
R1 = iF0j ꢀ jFci/ jF0j.
P
P
2
2
0:5
d
wR2 ¼ f ½wðF 20 ꢀ F c2Þ ꢁ= ½wðF 20Þ ꢁg
.
(d) T. Iwamoto, C. Kabuto, M. Kira, J. Am. Chem. Soc. 121 (1999) 886;
(e) M. Ichinohe, T. Matsuno, A. Sekiguchi, Angew. Chem., Int. Ed. 38
(1999) 2194;
(f) T. Iwamoto, M. Tamura, C. Kabuto, M. Kira, Science 290 (2000)
504;
Acknowledgements
This work was supported by a Grant-in-Aid for Scien-
tific Research (Nos. 14078204, 16205008, 17655014) from
the Ministry of Education, Culture, Sports, Science and
Technology and COE (Center of Excellence) program.
(g) M. Ichinohe, M. Igarashi, K. Sanuki, A. Sekiguchi, J. Am. Chem.
Soc. 127 (2005) 9978;
(h) N. Wiberg, H.-W. Lerner, S.-K. Vasisht, S. Wagner, K. Karaghi-
osoff, H. No¨th, W. Ponikwar, Eur. J. Inorg. Chem. (1999) 1211.
[3] (a) V.Ya. Lee, M. Ichinohe, A. Sekiguchi, N. Takagi, S. Nagase, J.
Am. Chem. Soc. 122 (2000) 9034;
References
(b) V.Ya. Lee, M. Ichinohe, A. Sekiguchi, J. Am. Chem. Soc. 122
(2000) 12604;
(c) V.Ya. Lee, T. Matsuno, M. Ichinohe, A. Sekiguchi, Heteroatom.
Chem. 12 (2001) 223;
(d) V.Ya. Lee, M. Ichinohe, A. Sekiguchi, Chem. Lett. (2001) 728;
(e) V.Ya. Lee, M. Ichinohe, A. Sekiguchi, Chem. Commun. (2001)
2146;
[1] (a) V.Ya. Lee, A. Sekiguchi, in: Z. Rappoport (Ed.), The Chemistry
of Organic Germanium, Tin and Lead Compounds, vol. 2, Wiley,
Chichester, 2002, Part 1; Chapter 14;
(b) A. Sekiguchi, V.Ya. Lee, Chem. Rev. 103 (2003) 1429;
(c) A. Sekiguchi, V.Ya. Lee, in: N. Auner, J. Weis (Eds.), Organo-
silicon Chemistry V (From Molecules to Materials), Wiley-VCH,
Weinheim, 2003, p. 92.
(f) V.Ya. Lee, M. Ichinohe, A. Sekiguchi, J. Organomet. Chem. 636
(2001) 41;
[2] (a) A. Sekiguchi, H. Yamazaki, C. Kabuto, H. Sakurai, S. Nagase, J.
Am. Chem. Soc. 117 (1995) 8025;
(g) V. Ya. Lee, M. Ichinohe, A. Sekiguchi, J. Am. Chem. Soc. 124
(2002) 9962;
(b) A. Sekiguchi, N. Fukaya, M. Ichinohe, N. Takagi, S. Nagase, J.
Am. Chem. Soc. 121 (1999) 11587;
(h) V.Ya. Lee, M. Ichinohe, A. Sekiguchi, Main Group Met. Chem.
25 (2002) 1;
(c) A. Sekiguchi, Y. Ishida, N. Fukaya, M. Ichinohe, N. Takagi, S.
Nagase, J. Am. Chem. Soc. 124 (2002) 1158;

V.Ya. Lee et al. / Journal of Organometallic Chemistry 692 (2007) 10–19
19
(i) V.Ya. Lee, K. Takanashi, M. Ichinohe, A. Sekiguchi, J. Am.
Chem. Soc. 125 (2003) 6012;
[12] A. Sekiguchi, R. Izumi, S. Ihara, M. Ichinohe, V. Ya. Lee, Angew.
Chem., Int. Ed. 41 (2002) 1598.
(j) V.Ya. Lee, A. Sekiguchi, Chem. Lett. 33 (2004) 84;
(k) V.Ya. Lee, K. Takanashi, M. Nakamoto, A. Sekiguchi, Russ.
Chem. Bull., Int. Ed. 53 (2004) 1102.
[13] The independent synthesis and physico-chemical characteristics of
digermene (tBu2MeSi)2Ge@Ge(SiMetBu2)2 will be reported in the
forthcoming publication.
[4] V.Ya. Lee, M. Ichinohe, A. Sekiguchi, J. Organomet. Chem. 685
(2003) 168.
[14] We do not discuss the structural parameters of 2b in details, because
its refinement was not sufficiently good.
[5] Preliminary communication: V. Ya. Lee, H. Yasuda, M. Ichinohe,
A. Sekiguchi, Angew. Chem., Int. Ed. 44 (2005) 6378.
[6] S.P. Mallela, R.A. Geanangel, Inorg. Chem. 30 (1991) 1480.
[7] H.-W. Lerner, F. Scho¨del, I. Sa¨nger, M. Wagner, M. Bolte, Z.
Naturforsch. 59b (2004) 277.
[15] (a) J.-H. Hong, J.S. Han, G.-H. Lee, I.N. Jung, J. Organomet.
Chem. 437 (1992) 265;
(b) J. Braddock-Wilking, M.Y. Chiang, P.P. Gaspar, Organometallics
12 (1993) 197.
[16] K.M. Baines, W.G. Stibbs, Coord. Chem. Rev. 145 (1995) 157.
[17] (a) M. Kira, T. Ishima, T. Iwamoto, M. Ichinohe, J. Am. Chem. Soc.
123 (2001) 1676;
[8] M. Ichinohe, Y. Arai, A. Sekiguchi, N. Takagi, S. Nagase, Organo-
metallics 20 (2001) 4141.
[9] A. Sekiguchi, S. Inoue, M. Ichinohe, Y. Arai, J. Am. Chem. Soc. 126
(2004) 9626.
(b) K. Mochida, T. Kayamori, M. Wakasa, H. Hayashi, M.P.
Egorov, Organometallics 19 (2000) 3379;
[10] Previously, the similar Na–Cl exchange, involving the electron
transfer steps, has been observed in the reactions of dichlorodisila-
(c) M.S. Samuel, M.C. Jennings, K.M. Baines, Organometallics 20
(2001) 590.
[18] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M.C.
Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr. 27 (1994)
435.
t
germirane, -trisilirane and -trigermirane with Bu3SiNa: Ref. [3c] and
M. Ichinohe, H. Sekiyama, N. Fukaya, A. Sekiguchi, J. Am. Chem.
Soc. 122 (2000) 6781.
[11] The Ge@Ge bond is typically trans-bent: P.P. Power, Chem. Rev. 99
(1999) 3463.
[19] G.M. Sheldrick, SHELXL-97, Program for Crystal Structure Refine-
ment, University of Go¨ttingen, Germany, 1997.