Reactivity of a germa-alkyne: Evidence for a germanone intermediate in the hydrolysis and alcoholysis processes

Article abstract of DOI:10.1016/j.jorganchem.2009.03.005

The formation of a new transient germa-alkyne Ar-Ge{partial triple bond, top dashed}C-SiMe₃ [Ar = 2,4-di-tert-butyl-6-(diisopropylaminomethyl)phenyl] is achieved by photolysis of the corresponding trimethylsilyldiazomethylgermylene ArGeC(N₂)SiMe₃ (2). The germa-alkyne is characterized by trapping reactions with H₂O and an equimolar mixture of tert-butanol and water. The respective adducts, the gem-germanediol 5 and the alkoxygermanol 4 have been fully characterized by spectroscopic methods. A study of the mechanism is proposed and in both cases, the addition involves the transient formation of a germanone. The structures of 2 and 5 are determined by single-crystal X-ray diffraction.

Full text of DOI:10.1016/j.jorganchem.2009.03.005

Journal of Organometallic Chemistry 694 (2009) 2246–2251
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Reactivity of a germa-alkyne: Evidence for a germanone intermediate
in the hydrolysis and alcoholysis processes
c
a,b
Eric Bonnefille a,b, Stéphane Mazières a,b, , Nathalie Saffon , Claude Couret
*
a Université de Toulouse, UPS, LHFA, 118 Route de Narbonne, F-31062 Toulouse, France
b CNRS, LHFA UMR 5069, F-31062 Toulouse, France
c Université Paul Sabatier, Structure Fédérative Toulousaine en Chimie Moléculaire, FR2599, 118 Route de Narbonne, F-31062 Toulouse, France
a r t i c l e i n f o
a b s t r a c t
Article history:
The formation of a new transient germa-alkyne Ar-Ge§C–SiMe3 [Ar = 2,4-di-tert-butyl-6-(diisopropy-
laminomethyl)phenyl] is achieved by photolysis of the corresponding trimethylsilyldiazomethylgermyl-
ene ArGeC(N2)SiMe3 (2). The germa-alkyne is characterized by trapping reactions with H2O and an
equimolar mixture of tert-butanol and water. The respective adducts, the gem-germanediol 5 and the alk-
oxygermanol 4 have been fully characterized by spectroscopic methods. A study of the mechanism is pro-
posed and in both cases, the addition involves the transient formation of a germanone. The structures of 2
and 5 are determined by single-crystal X-ray diffraction.
Received 19 December 2008
Received in revised form 3 March 2009
Accepted 4 March 2009
Available online 12 March 2009
Keywords:
Germa-alkyne
Trimethylsilyldiazomethylgermylene
Germylene–carbene
Germanone
Ó 2009 Elsevier B.V. All rights reserved.
Hydroxygermene
1. Introduction
the corresponding chlorogermylene 1 (of general formula: ArGeCl)
is generated and leads by substitution reaction with the lithium
For nearly 30 years, in organometallic main group chemistry,
unsaturated compounds with metal–carbon multiple bonds pres-
ent a particular interest. This is in relation with their chemical
reactivity which is quite different and much greater than their cor-
responding organic analogues. If metal14-alkenes such as silenes
ꢀSi'Cꢁ [1], germenes ꢀGe'Cꢁ [2] and stannenes ꢀSn'Cꢁ [3]
are now numerous, metalla-alkynes of general formula –M§C–
(M = Si, Ge, Sn) are still rare or unknown. Indeed, only one
germa-alkyne [4] and two stanna-alkynes [5] are described in the
literature. These compounds still have a short lifetime and are
characterized by trapping reactions.
salt of the trimethylsilyldiazomethane to the substituted-diazom-
ethylgermylene ArGeC(N2)SiMe3 2. The latter is decomposed by
photolysis to generate the corresponding germylene–carbene
which can be written in a contribution form as a germa-alkyne 3
(Scheme 1).
2.1.1. Synthesis and characterization of the chlorogermylene 1
The chlorogermylene 1 is obtained by reaction of the lithium
derivative ArLi [Ar = 2,4-di-tert-butyl-6-(diisopropylaminometh-
yl)phenyl] with the dichlorogermylene Á dioxane complex, as sum-
marized in Scheme 2.
The 1H NMR spectrum of 1 is characteristic of such a structure,
especially concerning the signal relative to the diastereotopic
benzylic hydrogen atoms, which appears as an AX system. The
chirality of the germanium atom, which is enhanced by the intra-
molecular coordination N ? Ge explains the non-equivalence of
these hydrogen atoms. Also by the 13C NMR analysis we can notice
that the isopropyl groups are not equivalent and generate twice as
many signals. We grew crystals of 1, but unfortunately, with insuf-
ficient quality for a satisfactory X-ray analysis (see Supplementary
materials). Nevertheless, a few interesting data can be extracted
and the main feature is the strong donation of the nitrogen to
the germanium center (dGe–N = 2.153 Å). This is in relation with
the marked withdrawing effect of the chlorine atom. As expected,
this coordination causes the lengthening of the Ge–Cl bond
(2.338 Å) and thus increases the leaving ability of the chlorine.
In this paper we present the synthesis of a new germa-alkyne
and many aspects of its chemical reactivity. A study of the mecha-
nisms of the hydrolysis and alcoholysis reactions is investigated.
2. Results and discussion
2.1. Synthesis of the germa-alkyne Ar-Ge§C–SiMe3 3 [Ar = 2,4-di-
tert-butyl-6-(diisopropylaminomethyl)phenyl]
Based on our previously described synthetic pathway [4], the
synthesis of the germa-alkyne involves successive reactions. First
* Corresponding author. Address: Université de Toulouse, UPS, LHFA, 118 Route
de Narbonne, F-31062 Toulouse, France. Tel.: +33 5 61 55 63 54; fax: +33 5 61 55 82
04.
E-mail address: mazieres@chimie.ups-tlse.fr (S. Mazières).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.03.005

E. Bonnefille et al. / Journal of Organometallic Chemistry 694 (2009) 2246–2251
2247
hν
Ar Ge
C
SiMe3
Ar Ge
C
SiMe3
Ar Ge
C
SiMe3
- N2
N2
3
2
Ar = 2,4-di-tert-butyl-6-(diisopropylaminomethyl)phenyl
Scheme 1.
H
H
N(i-Pr)
_
N(i-Pr)2
n-BuLi
THF, - 78°C
N(i-Pr)2
GeCl2.diox.
2
t-Bu
Ge Cl
t-Bu
t-Bu
Br
Li
..
THF, -78°C
t-Bu
t-Bu
t-Bu
1
Scheme 2.
N(iPr)2
N(iPr)2
N(iPr)2
Br
THF / -78°C
THF / -78°C
t-Bu
t-Bu
t-Bu
Ge
..
C
SiMe3
Ge Cl
..
1. + n-BuLi
Me3SiC(N)2Li
N2
2. + GeCl2.diox.
3. + Me3SiC(N)2Li
t-Bu
t-Bu
t-Bu
2
1
Scheme 3.
Indeed, easy nucleophilic substitutions on the germanium atom
can be carried out, such as the reaction with the trimethylsilyldia-
zomethane anion which leads to the diazomethylgermylene 2 with
good yields (Scheme 3).
2.1.2. Synthesis and characterization of the diazomethylgermylene 2
The synthesis of 2 can be realized from 1 by reaction with the
trimethylsilyldiazomethane anion or can also be brought about di-
rectly by a one pot reaction starting from the brominated ligand
(Scheme 3).
As for 1, the 1H NMR spectrum of 2 shows a characteristic AB
system for the benzylic protons. The presence of the diazoic moiety
is evidenced first by 13C NMR with a signal at 28.83 ppm for the
diazo carbon, which is in accordance with the value previously
found for a similar compound [4]. Also the vibration observed in
CN2 = 2002.9 cmÀ1) and the UV absorption
ꢀ
m
the infrared analysis (
*
(n–
p transition at 366 nm, e
: 126 L molÀ1 cmÀ1) are in agreement
with the diazo structure (see Fig. 1).
X-ray analysis of 2 shows a monomeric structure in the solid
state with a strong interaction between the germanium and the
nitrogen atom of the side chain. Indeed, the Ge–N(3) distance
(2.252 Å) is appreciably shorter than the sum of van der Waals
Fig. 1. Molecular structure of 2 in the solid state. Thermal ellipsoids are at the 50%
probability level. Hydrogen atoms are omitted for clarity.
radii (3.74 Å) [6] but longer than a usual germanium–nitrogen
r
bond (1.84 Å) [7]. Ge–C(1) and Ge–C(2) bonds are nearly in an
orthogonal position (97°); Ge–C(1) (2.031 Å) and C(1)–Si
(1.846 Å) bond lengths are close to the standard values for these
R
N
R
N
R
R
R
corresponding
r bonds, 1.94 and 1.85 Å, respectively [7]. The angle
Ge–C(1)–Si (126.6°) suggests an sp2 hybridization for the C(1) car-
bon atom and is slightly increased by the steric repulsion around
the germanium atom on one side and by the trimethylsilyl group
on the other side.
R = i-Pr
N
R
Moreover the examination of the main data from the previously
described diazogermylene [4], with two side arms on the aryl
group, allows an interesting comparison with 2 concerning these
two kinds of ligand (types I and II) (see Fig. 2).
Type I
Type II
Fig. 2. Ligands.

2248
E. Bonnefille et al. / Journal of Organometallic Chemistry 694 (2009) 2246–2251
This kind of type II ligand (with R = Me) was introduced by
the formation of solid polymeric materials of general formula
(ArGeCSiMe3)n. The total disappearance of 2 is confirmed by
NMR analysis and the 1H NMR spectrum shows broad signals char-
acteristic of such polymeric structures. Otherwise, when this pho-
tolysis is performed at low temperature (À50 °C) we do not
observe any evolution of nitrogen. It is interesting to notice that
a blue emission occurs during the irradiation. This phenomenon
does not take place at room temperature, indicating that it is due
to phosphorescence. A thermal activation barrier should be in-
volved in this photochemical process, and this mainly tells us that
it is not possible to generate such unsaturated species at low
temperature.
Yoshifuji and coworkers in 1994 [8a] and used later by Jutzi in ger-
manium chemistry [8b]. This ligand combines the steric features of
a supermesityl group and the electronic properties of the o-((diiso-
propylamino)methyl)phenyl system. On the other hand, type I
which is known as a pincer ligand combines mainly the electronic
effects of the two side arms.
The most significant difference of these ligands (Ar) is the stron-
ger intramolecular coordination occulting in type II. This can be re-
lated to the germanium–nitrogen distances observed for the
corresponding diazo compounds ArGeC(N2)SiMe3. These distances
are much longer in the diazocompound using the type I ligand (Ge–
N: 2.359 and 3.05 Å) where the two nitrogen atoms interact suc-
cessively with the germanium center, leading to a dynamic system
[4]. In contrast, the Ge–N bond length (2.252 Å) observed in 2
shows a strong interaction, indicating a static system where the
germanium is in constant coordination with the nitrogen. This dif-
ference in structure will lead to a different chemical behavior.
2.1.4. Photochemical decomposition with a trapping reagent
The same photolysis is performed in a toluene solution and in
presence of an excess of 2-methylpropan-2-ol (tert-butyl alcohol)
as a trapping agent, at room temperature. The choice of such a ter-
tiary alcohol is justified because it is non-reactive towards the dia-
zocompound 2. Surprisingly and contrary to what was already
described [4], we do not observe the formation of the expected
dialkoxygermane ArGe(Ot-Bu)2CH2SiMe3 resulting from the addi-
tion of two equivalents of tert-butyl alcohol to the germanium–car-
bon triple bond in relation with its polarity Ged+–CdÀ. In our case,
only polymeric materials are obtained and the trapping agent does
not play any role.
Next we realized the decomposition of 2 in a toluene solution in
the presence of tert-butyl alcohol in excess and a stoichiometric
amount (1 equiv.) of water. We checked beforehand that in our
experimental conditions (toluene solution at room temperature)
H2O does not react with 2. Under these conditions we observe
the formation of the alkoxygermanol ArGe(Ot-Bu)(OH)CH2SiMe3
4 in nearly quantitative yield. The same reaction, performed in
the presence of tert-butyl alcohol but with 2 equiv. of water, leads
almost exclusively to the gem-germanediol ArGe(OH)2CH2SiMe3 5.
Compound 4 appears as a waxy material, impossible to crystal-
lize, but it is unambiguously identified by usual spectroscopic
methods (see Section 4). On the other hand, single crystals of 5
are obtained allowing an X-ray analysis (see Fig. 3).
2.1.3. Photochemical decomposition of diazomethylgermylene 2
The photolysis is performed in toluene at room temperature
with a Medium-Pressure mercury lamp (Oriel Company) with a
maximum wavelength of 365 nm and causes the expected dinitro-
gen evolution. A complete decomposition of 2 is observed in less
than 30 min for a standard experiment (see Section 4). When the
photolysis is monitored without a trapping reagent, we observe
Concerning 5 which has a dimeric structure in the solid state,
we can observe that the coordination N ? Ge disappears and is re-
placed by an hydrogen bond between the nitrogen atom of the arm
and the hydrogen atom of a hydroxyl moiety (N–H(1) = 1.979 Å).
This hydrogen bonding is evidenced by
a
NÁÁÁO distance of
2.712 Å, which indicates a quite strong NÁÁÁH interaction in the so-
lid state [9]. This intramolecular bond leads to a decrease of the an-
gle C(1)–Ge–O(1) (106.04°) in the seven membered pseudo-cycle
compared to the external angle C(1)–Ge–O(2) (115.16°).
Such stable gem-germanediols are interesting compounds
and only a few are reported in the literature [10 and references
therein].
Fig. 3. Molecular structure of 5 in the solid state. Thermal ellipsoids are at the 50%
probability level. Hydrogen atoms are omitted for clarity.
H2O
Ar Ge CH2 SiMe3
Ar Ge CH SiMe3
OH
3
O
6
7
H2O
2 t-BuOH
Ot-Bu
t-BuOH
OH
OH
Ar Ge CH2 SiMe3
Ar Ge CH2 SiMe3 Ar Ge CH2 SiMe3
Ot-Bu
Ot-Bu
OH
4
5
Scheme 4.

E. Bonnefille et al. / Journal of Organometallic Chemistry 694 (2009) 2246–2251
2249
2.1.5. Study of the mechanism of alcoholysis and hydrolysis reactions
of the germa-alkyne
The photolysis of trimethylsilyldiazomethylgermylene 2 effi-
ciently generates the corresponding germylene–carbene which
can be considered as a contributing structure of a germa-alkyne
3 (as shown in Scheme 1), after evolution of dinitrogen.
Laboratory of the Laboratoire de Chimie de Coordination, Toulouse,
France. ArBr was prepared as for the methyl derivative described in
the literature [13].
4.2. Synthesis of 1-bromo-2,4-di-tert-butyl-6-
(diisopropylaminomethyl)benzene
Our experimental results show that tert-butyl alcohol does not
react with the germa-alkyne 3 and the presence of water is neces-
sary to observe a reaction. So we can postulate that the first step of
this reaction is the addition of H2O on the germanium–carbon tri-
ple bond. This addition can be explained by a better reactivity of
H2O compared to the tertiary alcohol t-BuOH, relative to their cor-
responding acidity. This electrophilic addition leads to the
hydroxygermene 6 or its keto-tautomer 7. Germanones, which
can be considered as heavy analogues of ketones, are known to
be extremely reactive intermediates [10 and references therein].
And it is known that the reaction of germa-alkenes are quite slow
with tertiary alcohols, mainly due to the acidity which plays a
dominant role [11]. In our process, 7 could then react with t-BuOH
to lead to the alkoxygermanol 4 or with H2O to generate the gem-
germanediol 5 (Scheme 4).
A similar mechanism was postulated by Tokitoh and coll. for the
hydrolysis and alcoholysis reactions of a digermyne [12]. The
authors, using theoretical calculations, found for their Dmp model
(Dmp = 2,6-dimethylphenyl) that the germanone (DmpGe(O)-
GeH2Dmp) was 9.9 kcal/mol more stable than the enol tautomer.
In accordance with these results, and due to the fact that 3 does
not react directly with tert-butyl alcohol, it seems reasonable to
postulate that in our case the germanone 7 is the active intermedi-
ate in the hydrolysis and alcoholysis of the germa-alkyne.
A solution of diisopropylamine (74 mL, 0.41 mol) and 2-bromo-
1-bromomethyl-3,5-di-tert-butylbenzene (68.42 g, 0.19 mol) in
toluene (400 mL) was refluxed for 48 h. Diisopropylammonium
bromide was eliminated by filtration then the solvent was re-
moved in vacuum leading to yellow oil which was purified by
distillation.
(64.8 g, 0.17 mol, 90% yield); Eb: 122 °C/0.2 mmHg; 1H NMR
3
(C6D6), d (ppm): 0.96 (d, JH/H = 6.5 Hz, 12H, CH(CH3)2), 1.36 (s,
3
9H, C(CH3)3), 1.63 (s, 9H, C(CH3)3), 2.93 (sept, JH/H = 6.5 Hz, 2H,
4
CH(CH3)2), 3.89 (s, 2H, CH2), 7.52 (d, JH/H = 3.2 Hz, 1H, H5), 7.98
4
(d, JH/H = 3.2 Hz, 1H, H3); 13C NMR (C6D6),
d (ppm): 20.68
(CH(CH3)2), 30.16 (C(CH3)3), 31.26 (C(CH3)3), 34.71 (C(CH3)3),
37.21 (C(CH3)3), 48.63 (CH(CH3)2), 51.02 (CH2), 121.30 (1-aryl-C),
123.09 (5-aryl-C), 125.65 (3-aryl-C), 142.94 (2-aryl-C), 146.80 (4-
aryl-C), 148.82 (6-aryl-C); SM–IE (70 eV), m/z (%): 381 (M+,17),
366 (M+ÀMe,50), 281 (M+ÀN(iPr)2,100).
4.3. Synthesis of 1-chloro-1-[4,6-di-tert-butyl-2-
(diisopropylaminomethyl)phenyl]germylene (1) (ArGeCl)
A solution of n-butyllithium (1.1 mL, 1.75 mmol, 1.6 M in
hexane) was added dropwise to a solution of 1-bromo-2,4-di-tert-
butyl-6-(diisopropylaminomethyl)benzene (0.61 g, 1.59 mmol) in
THF (6 mL) at (À78 °C). The brown mixture was stirred for 30 min
then added dropwise to a solution of GeCl2–dioxane (0.37 g,
1.59 mmol,) in THF at À78 °C. The mixture was allowed to warm
to room temperature. Solvents were removed under vacuum to gen-
erate crude 1 which was dissolved in pentane 20 mL). After filtration
through Celite the pentane was removed leading to a yellow solid.
(0.51 g, 1.25 mmol, 79% yield); m.p.: 168–169 °C; 1H NMR (C6D6),
d (ppm): 0.75 (d, 3JH/H = 6.7 Hz, 3H, CH(CH3)2), 0.80 (d, 3JH/H = 9.1 Hz,
3. Conclusion
The synthesis of the germyne Ar-Ge§C–SiMe3 3 [Ar = 2,4-di-
tert-butyl-6-(diisopropylaminomethyl)phenyl], as well as its
chlorogermylene ArGeCl and diazogermylene ArGeC(N2)SiMe3 pre-
cursors, have been reported. This new organometallic alkyne was
evidenced by trapping reactions with water and tert-butyl alcohol.
Using different stoichiometric amounts of reactants, it was demon-
strated that the active intermediate is the germanone ArGe(O)CH2-
SiMe3 resulting from the electrophilic addition of H2O onto the
germanium–carbone triple bond. The gem-germanediol and the
alkoxygermanol obtained arose respectively from the subsequent
addition of H2O or t-BuOH onto the germanone intermediate.
These results show that unsaturated organometallic com-
pounds such as germa-alkynes or germanones can lead to similar
reactions to those of their corresponding organic compounds, but
present a very much higher reactivity.
3H, CH(CH3)2), 0.82 (d, 3JH/H = 6.7 Hz, 3H, CH(CH3)2), 1.32 (d, 3JH/H
=
6.7 Hz, 3H, CH(CH3)2), 1.35 (s, 9H, C(CH3)3), 1.62 (s, 9H, C(CH3)3),
3
3.04 (sept, JH/H = 6.7 Hz, 1H, CH(CH3)2), 3.77–4.57 (AX system,
2JH/H = 15.0 Hz, 2H, CH2N), 4.08 (sept, 3JH/H = 6.7 Hz, 1H, CH(CH3)2),
4
4
7.02 (d, JH/H = 3.4 Hz, 1H, H5), 7.48 (d, JH/H = 3.4 Hz, 1H, H3); 13C
NMR (C6D6), d (ppm): 18.16 (CH(CH3)2), 20.61 (CH(CH3)2), 20.97
(CH(CH3)2), 22.69 (CH(CH3)2), 31.35 (C(CH3)3), 33.22 (C(CH3)3),
34.59 (C(CH3)3), 37.47 (C(CH3)3), 51.17 (CH(CH3)2), 57.47
(CH(CH3)2), 60.23 (CH2), 117.67 (3-aryl-C), 120.69 (5-aryl-C),
146.79 (2-aryl-C), 150.65 (4-aryl-C), 155.43 (6-aryl-C), 156.56 (1-
aryl-C); EI–MS (70 eV), m/z (%): 411 (M+, 85), 376 (M+ÀCl, 90), 368
(M+ÀiPr, 100), 354 (M+–tBu, 60). Anal. Calc. for C21H36NClGe: C,
61.43, H, 8.84, N, 3.41, Found: C, 61.58, H, 8.91, N, 3.33%.
4. Experimental
4.1. General methods
4.4. Synthesis of ArGeC(N2)SiMe3 (2)
All reactions were carried out under an atmosphere of purified
argon using standard Schlenk techniques. Tetrahydrofuran, diethyl
ether, toluene, n-pentane were purified by distillation from so-
dium/benzophenone ketyl. Infrared spectra were recorded with a
Perkin–Elmer FT-IR 1600 spectrometer. The 1H (300.1 MHz), 13C
(75.4 MHz) and 29Si (59.6 MHz) NMR spectra were recorded on
the spectrometer Bruker Avance 300. Nucleus, frequence and
solvent were indicated for each compound. Chemical shifts are re-
ported in ppm units (parts per million) downfield from tetrameth-
ylsilane (1H, 13C, 29Si). Melting points were determined using
sealed argon purged capillaries with a Leitz Biomed 50 melting
point apparatus. Microanalyses were performed at the Analitycal
A
solution of lithiotrimethylsilyldiazomethane (7.52 mmol)
prepared from stoichiometric quantity of n-butyllithium
a
(8.32 mmol, 5.2 mL, 1.6 M in n-hexane) and trimethylsilyldiazome-
thane (7.52 mmol, 3.76 mL, 2 M in n-hexane) was added dropwise
at À78 °C to 1 (2.88 g, 7.52 mmol) in THF (15 mL). The brown solu-
tion was stirred for 2 h then allowed to warm to room tempera-
ture. All volatiles were removed under vacuum and the residue
dissolved in pentane. After filtration through Celite, removal of
the solvents in vacuum leads to 2 as a yellow solid.
(2.93 g, 6.02 mmol, 80% yield); m.p.: 113 °C (dec.); 1H NMR
(C6D6), d (ppm): 0.35 (s, 9H, Me3Si), 0.84 (d, JH/H = 6.7 Hz, 6H,
3

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E. Bonnefille et al. / Journal of Organometallic Chemistry 694 (2009) 2246–2251
3
CH(CH3)2), 0.90 (d, JH/H = 6.7 Hz, 3H, CH(CH3)2), 1.25 (d,
3JH/H = 6.7 Hz, 3H, CH(CH3)2), 1.35 (s, 9H, C(CH3)3), 1.58 (s, 9H,
For all the structures data were collected at low temperature
(173 K) on a Bruker-AXS APEX II diffractometer equipped with
the Bruker Kryo-Flex cooler device and using a graphite-mono-
3
C(CH3)3), 3.14 (sept, JH/H = 6.7 Hz, 1H, CH(CH3)2), 3.82–3.93 (AB
system, JH/H = 15.2 Hz, 2H, CH2N), 3.87 (sept, JH/H = 6.7 Hz, 1H,
2
3
chromated Mo Ka radiation (k = 0.71073 Å). The structures were
4
4
CH(CH3)2), 7.15 (d, JH/H = 3,2 Hz, 1H, H3), 7.54 (d, JH/H = 3.2 Hz,
1H, H5); 13C NMR (C6D6), d (ppm): À0.28 (CH3Si), 18.68 (CH(CH3)2),
20.58 (CH(CH3)2), 21.63 (CH(CH3)2), 23.40 (CH(CH3)2), 26.82 (CN2),
31.37 (C(CH3)3), 32.11 (C(CH3)3), 34.50 (C(CH3)3), 37.37 (C(CH3)3),
51.80 (CH(CH3)2), 57.37 (CH(CH3)2), 60.17 (CH2), 118.24 (3-aryl-
C), 120.66 (5-aryl-C), 145.98 (2-aryl-C), 149.64 (4-aryl-C), 153.88
(1-aryl-C), 155.60 (6-aryl-C); 29Si NMR (C6D6), d (ppm): À0.25; IR
ꢀ
solved by direct methods [14] and all non-hydrogen atoms were
refined anisotropically using the least-squares method on F2 [15].
Selected data for the diazomethylgermylene 2: C25H45GeN3Si,
M = 488.32, monoclinic, space group Cc, a = 11.688(2) Å, b =
22.024(4) Å, c = 11.1173(19) Å,
a = c = 90°, b = 97.968(3)°, V =
2834.2(8) Å3, Z = 4, crystal size 0.30 Â 0.20 Â 0.20 mm3, 7123
reflections collected (3972 independent, Rint = 0.0227), 310 param-
(C6D6):
m
(CN2) = 2002.9 cmÀ1; EI–MS (70 eV), m/z (%): 489 (M+,
eters, R1 [I > 2 (I)] = 0.0340, wR2 [all data] = 0.0807, largest difference
r
20), 446 (M+ÀiPr, 5), 376 (ArGe, 100); UV (pentane) kmax
(e
):
in peak and hole: 0.308 and À0.267 e ÅÀ3
.
366 nm (126). Anal. Calc. for C25H45N3GeSi: C, 61.49, H, 9.29, N,
8.60; Found: C, 61.60, H, 9.38, N, 8.49%.
Selected data for the gem-germanediol 5: C25H49GeNO2Si,
M = 496.33, monoclinic, space group C2/c, a = 21.8065(17) Å, b =
12.4031(10) Å, c = 23.1368(18) Å,
a = c = 90°, b = 113.376(2)°, V =
4.5. Reaction of 3 with t-BuOH/H2O, synthesis of 4
5744.1(8) Å3, Z = 8, crystal size 0.40 Â 0.30 Â 0.20 mm3, 12,395
reflections collected (4067 independent, Rint = 0.0841), 290 param-
A solution of 2 (77 mg, 0.16 mmol) in 2 mL of tert-butyl alcohol
eters, R1 [I > 2 (I)] = 0.0453, wR2 [all data] = 0.0773, largest difference
r
and 2.8
lL of water was photolyzed at room temperature in a
in peak and hole: 0.329 and À0.287 e ÅÀ3
.
quartz Schlenk for 30 min. Then the tert-butyl alcohol was elimi-
nated under vacuum and the residue, a waxy material, dissolved
in C6D6 was identified to 4.
Appendix A. Supplementary data
(75 mg, 0.136 mmol, 85% yield); 1H NMR (C6D6), d (ppm): 0.30
CCDC 713960 and 713961 contain the supplementary crystallo-
graphic data for 2 and 5. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif. Supplementary data associated with
this article (for 1) can be found, in the online version, at
doi:10.1016/j.jorganchem.2009.03.005.
2
(s, 9H, Me3Si), 0.74–0.87 (AB system, JH/H = 15.1 Hz, 2H,
3
3
CH2SiMe3), 1.05 (d, JH/H = 6.7 Hz, 6H, CH(CH3)2), 1.11 (d, JH/H
=
6.7 Hz, 6H, CH(CH3)2), 1.36 (s, 9H, C(CH3)3), 1.36 (s, 9H, OC(CH3)3),
1.65 (s, 9H, C(CH3)3), 3.00 (sept, 3JH/H = 6.7 Hz, 2H, CH(CH3)2), 3.90–
2
4.48 (AB system, JH/H = 15.1 Hz, 2H, CH2N), 7.63 (br, 1H, H3), 7.65
(br, 1H, H5), 7.98 (br s, 1H, OH); 13C NMR (C6D6), d (ppm): 1.01
(CH3Si), 13.13 (CH2SiMe3), 19.98 (CH(CH3)2), 21.73 (CH(CH3)2),
31.11 (C(CH3)3), 32.65 (OC(CH3)3), 33.33 (C(CH3)3), 34.66
(C(CH3)3), 37.13 (C(CH3)3), 47.37 (CH(CH3)2), 51.36 (CH2NiPr2),
73.38 (OC(CH3)3), 121.96 (3-aryl-C), 128.70 (5-aryl-C), 137.82 (1-
aryl-C), 147.00 (2-aryl-C), 150.86 (4-aryl-C), 155.14 (6-aryl-C);
29Si NMR (C6D6), d (ppm): 0.73; EI-MS (70 eV), m/z (%): 536
(MÀOH, 10), 480 (MÀOtBu, 30), 436 (MÀOHÀNiPr2, 100); CI-MS
(NH3), m/z (%): 554 (M+H+, 100).
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