The addition of oxygen to tetramesityldigermene

Article abstract of DOI:10.1016/S0022-328X(01)01040-3

The addition of atmospheric oxygen to tetramesityldigermene under a variety of conditions was studied. The addition of oxygen to the digermene, prepared by the photolysis of hexamesitylcyclotrigermane in THF, cleanly afforded 3,3,4,4-tetramesityl-3,4-digermadioxetane (7). The photolysis of hexamesitylcyclotrigermane in toluene in the presence of triethylsilane under the ambient atmosphere gave a very complex product mixture, from which 2,2,4,4-tetramesityl-2,4-digermadioxetane (9), tetramesityldigermaoxirane (10) and 2,2,4,4,5,5-hexamesityl-2,4,5-trigermadioxolane (11) were isolated and identified. The structures of compounds 9 and 11 were determined by X-ray crystallography.

Full text of DOI:10.1016/S0022-328X(01)01040-3

Journal of Organometallic Chemistry 636 (2001) 130–137
www.elsevier.com/locate/jorganchem
The addition of oxygen to tetramesityldigermene
Mini S. Samuel, Michael C. Jennings, Kim M. Baines *
Department of Chemistry, Uni6ersity of Western Ontario, London, Ont., Canada N6A 5B7
Received 15 March 2001; accepted 30 April 2001
Dedicated to Professor O. Nefedov on the occasion of his 70th birthday
Abstract
The addition of atmospheric oxygen to tetramesityldigermene under a variety of conditions was studied. The addition of oxygen
to the digermene, prepared by the photolysis of hexamesitylcyclotrigermane in THF, cleanly afforded 3,3,4,4-tetramesityl-3,4-di-
germadioxetane (7). The photolysis of hexamesitylcyclotrigermane in toluene in the presence of triethylsilane under the ambient
atmosphere gave a very complex product mixture, from which 2,2,4,4-tetramesityl-2,4-digermadioxetane (9), tetramesityldiger-
maoxirane (10) and 2,2,4,4,5,5-hexamesityl-2,4,5-trigermadioxolane (11) were isolated and identified. The structures of compounds
9 and 11 were determined by X-ray crystallography. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Germanium; Digermene; Dioxygen reactions; Digermadioxetane
Tetramesityldigermene is a well-known, readily syn-
thesised digermene derivative [4,5]. However, despite
1. Introduction
the extensive investigations of the reactivity of this
Although oxygenation is, perhaps, the most ubiqui-
digermene [6], the reaction of tetramesityldigermene
tous reaction of digermenes [1], there are only two
with atmospheric oxygen has not been investigated. We
reports concerning this important and fundamental re-
report herein the oxidation of tetramesityldigermene
action. Masamune and co-workers have investigated
under a variety of conditions.
the oxygenation reactions of tetrakis(2,6-diethyl-
phenyl)digermene (1a) and tetrakis(2,6-diisopropy-
lphenyl)digermene (1b) [2] and, Weidenbruch and co-
workers have investigated the addition of oxygen to a
(Z)-diaminodisilyldigermene (5) [3].
2. Results and discussion
Triplet oxygen adds to the tetraaryldigermenes, 1, to
provide the corresponding 1,2-digermadioxetanes (2)
that undergo photochemical rearrangement (254 nm) to
the 1,3-digermadioxetanes (3). The 1,2-digermadioxe-
tanes undergo thermal isomerisation to give 1-oxa-2-
germacyclopent-3-enes (4) (Scheme 1).
In contrast, the addition of oxygen to the (Z)-di-
aminodisilyldigermene 5 furnished the 1,3-digermadiox-
etane 6, stereospecifically. No evidence for the
intermediate formation of a 1,2-digermadioxetane was
reported (Scheme 2).
Photolysis of hexamesitylcyclotrigermane in toluene
at −70 °C in the presence of triethylsilane followed by
bubbling compressed air into the solution yielded a 1:1
mixture of the 1,2-digermadioxetane 7 and the silylger-
1
mane 8 [6f], as determined by H-NMR spectroscopy.
Removal of the solvent in vacuo and addition of ben-
zene to the crude product mixture caused precipitation
of 7. Compound 7 was identified by NMR spectroscopy
and mass spectrometry.
The 1H- and 13C-NMR spectra both showed the
presence of only one type of mesityl group. The mass
spectrum indicated the presence of a cluster of peaks
centred at 654 amu, corresponding to the molecular
ion. The precise mass of this ion was determined to be
654.179 amu, in good agreement with the calculated
* Corresponding author. Fax: +1-519-661-3022.
E-mail address: kbaines2@uwo.ca (K.M. Baines).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01040-3

M.S. Samuel et al. / Journal of Organometallic Chemistry 636 (2001) 130–137
131
Scheme 1.
mass of 654.177. Although the spectral data are also
consistent with 2,2,4,4-tetramesityl-2,4-digermadioxe-
tane, the data do not match that of the 1,3-digerma-
dioxetane, which has been unambiguously identified
(vide infra) (Scheme 3).
The addition of compressed air to a solution of
tetramesityldigermene (produced by the photolysis
of hexamesitylcyclotrigermane and triethylsilane) at
−70 °C in THF yielded only the 1,2-digermadioxetane,
7. No evidence for the formation of the silylgermane 8
was found. Addition of benzene to the THF solution
caused 7 to precipitate from the solution as a fine white
solid.
The absence of Et3SiGe(H)Mes2 (8) or any products
derived from the germylene, Mes2Ge:, was surprising.
THF is expected to form a donor complex with
Mes2Ge: [7]. THF donor adducts of dimethylsilylene
have been shown to decrease the rate of addition of the
silylene to various reagents [8]. Thus, it appears that the
THF-complexed germylene reacts with Et3SiH at an
appreciably slower rate. However, dimerisation of the
germylene to the digermene must still occur at a reason-
able rate. This is further corroborated by the isolated
yield of the 1,2-digermadioxetane 7. If the yield of 7 is
calculated based on the assumption that one equivalent
of cyclotrigermane produces one equivalent of diger-
mene, one obtains a yield of greater than 100%. How-
ever, a reasonable yield of 89% is obtained if the
cyclotrigermane is assumed to produce 1.5 equivalents
of the digermene.
NMR (CDCl3) and mass spectral data of 9 are in
complete accord with published data for this known
1
compound [9], the H-NMR chemical shifts in C6D6
were not consistent with the known values [10]. How-
ever, 9 was unequivocally identified by a single-crystal
X-ray structure determination. The molecular structure
of the molecule is presented in Fig. 1.
The molecular structure of 9 possesses two crystallo-
graphic twofold axes which bisect an almost square and
perfectly planar cyclodigermoxane ring. The mesityl
groups are attached to the cyclodigermoxane ring in a
roughly helical fashion. The GeꢀO bond distances are
,
all equal at 1.812(1) A, the GeꢀAr bond distances are
,
all equal at 1.949(2) A and the GeꢀGe distance is
,
2.6073(6) A. The GeꢀOꢀGeA and O(1)ꢀGeꢀO(1A)
bond angles are 92.03(9) and 87.97(10)°, respectively.
These values agree well with the published structure of
the tetraaryl-substituted 1,3-digermadioxetane (la) pre-
pared by Masamune and co-workers [2].
Since 9 was only obtained from the cophotolysis
reactions of the cyclotrigermane with oxygen, com-
pound 9 is believed to arise from the photochemical
rearrangement of the 1,2-digermadioxetane 7 which is
formed from the initial addition of oxygen to tetrame-
sityldigermene. At this time it is not known whether
this rearrangement is also thermal. The 1,2-digerma-
dioxetane 7 was found to rearrange in solution and as
a solid to the 1,3-digermadioxetane at room tempera-
ture; however, no measures were taken to exclude light.
Photolysis of hexamesitylcyclotrigermane in toluene
in the presence of triethylsilane at −70 °C under the
ambient atmosphere, yielded a complex mixture of
products including 8–11, and a small amount of 7
(Scheme 4).
The products were separated by preparative thin
layer chromatography. There were two or three other
products present in the crude product mixture that
1
could not be isolated or identified. Although the H-
Scheme 2.

132
M.S. Samuel et al. / Journal of Organometallic Chemistry 636 (2001) 130–137
Scheme 3.
Scheme 4.
Compound 10 was identified from 1H- and 13C-
Compound 11 was unequivocally identified by a sin-
gle-crystal X-ray structure determination. The molecu-
lar structure of the molecule is presented in Fig. 2. The
five-membered ring in 11 is almost planar. The mesityl
groups are attached to the trigermadioxolane ring in a
roughly helical fashion. The GeꢀO bond distances in
the trigermadioxolane are 1.777(1), 1.785(1), 1.804(1)
NMR spectroscopy and mass spectrometry. The 1H-
and 13C-NMR spectra both showed the presence of
only one type of mesityl group. The mass spectrum
indicated the presence of a cluster of peaks centred at
638 amu, corresponding to the molecular ion with a
precise mass of 638.1827, which is in good agreement
with the calculated mass of 638.1825. This compound
appears to be relatively stable, as it was stored as a
solid for several months under the ambient atmo-
sphere without any signs of further oxidation to the
1,3-digermadioxetane. We were unable to obtain a
crystal of 10 suitable for a single-crystal X-ray struc-
ture determination. West et al. successfully prepared
the disilaoxirane of R2SiꢁSiR2 (R=2,4,6-triisopropy-
lphenyl) by reaction with an equimolar amount of
m-chloroperbenzoic acid [11]. An attempt was made
to synthesise 10 by addition of m-chloroperbenzoic
,
and 1.808(1) A and the GeꢀAr bond distances range
,
from 1.968(2) to 1.988(2) A. The GeꢀOꢀGe and
OꢀGeꢀGe bond angles are 124.22(7), 124.11(7)° and
94.57(4), 94.29(4)°, respectively, and the OꢀGeꢀO bond
angle is 102.79(6)°. These values agree well with the
only other published structure of a 2,4,5-trigermadiox-
olane, 2,2-di-tert-butyl-4,4,5,5-tetraphenyl-2,4,5-triger-
madioxolane, prepared by Puff and co-workers [12]
,
who reported values of 1.783(1)–1.800(1) A for the
,
GeꢀO bond lengths and values of 1.93(2)–1.97(2) A for
the GeꢀAr bond lengths. They also observed bond
angles of 120.7(6), 120.0(5)° and 95.7(3), 97.1(3)° for
the GeꢀOꢀGe and OꢀGeꢀGe bond angles, respectively.
The OꢀGeꢀGe angle was found to be 105.1(5)°.
acid to
a solution of tetramesityldigermene and
Et3SiGe(H)Mes2 in toluene. However, analysis of the
1
product mixture by H-NMR spectroscopy showed it
to be a mixture of 9 and 11, a compound with
has been tentatively assigned as (triethylsiloxy)-
dimesitylgermanol (12), and only a small amount of
10.
The 1H-NMR spectrum of 11 in C6D6 was very
misleading as it did not show the presence of two
1
different mesityl groups. A H–13C HMBC spectrum
showed that the signals assigned to both p-methyl

M.S. Samuel et al. / Journal of Organometallic Chemistry 636 (2001) 130–137
133
aromatic hydrogens of the mesityl groups in the 1H
dimension were also accidentally coincident at 6.63
ppm. The observed precise mass of 965.267 is in good
agreement with the calculated mass of 965.263 for the
molecular ion.
The formation of compound 11 can be explained
easily by insertion of Mes2Ge: into the oxygen–oxygen
bond of the 1,2-digermadioxetane, 7. To provide evi-
dence for this hypothesis, a solution of equimolar
amounts of hexamesitylcyclotrigermane and 7 was pho-
tolysed in toluene at −70 °C. The reaction was
quenched by the addition of methanol. Analysis of the
1
product mixture by H-NMR spectroscopy revealed a
1:2:4 mixture of 9, 11 and 13. The results provide
support for the suggestion that Mes2Ge:, formed during
the photolysis of hexamesitylcyclotrigermane, may in-
deed insert into the oxygen–oxygen bond of 7 to
produce 11. Furthermore, since the reaction was per-
formed in the absence of air, 11 cannot be a direct
oxidation product of the cyclotrigermane. Compound 9
is believed to be formed from the competitive photo-
chemical rearrangement of 7. Tetramesityldigermene is
stable under the reaction conditions and, upon addition
of methanol, the methanol adduct 13 [13] of the diger-
mene is obtained (Scheme 5).
Cophotolysis of a solution of hexamesitylcyclotriger-
mane, Et3SiH, and air in THF, rather than toluene,
produced a product mixture similar in its complexity.
The notable difference between the two reactions is that
in THF, compound 8, derived from addition of Et3SiH
to Mes2Ge:, is present in only small amounts, consistent
,
Fig. 1. Molecular structure of 9. Important bond lengths (A) and
bond angles (°): GeꢀO(1)=1.8119(15), GeꢀC(11)=1.949(2),
GeꢀGeA=2.6073(6); O(1A)ꢀGeꢀO(1)=87.97(10), GeꢀO(1)ꢀGeA=
92.03(9), O(1A)ꢀGeꢀC(11)=114.61(6), O(1)ꢀGeꢀC(11)=107.74(6),
C(11)ꢀGeꢀC(11A)=119.85(12), O(1A)ꢀGeꢀGeA=43.99(5), C(11)ꢀ
GeꢀGeA=120.08(6), C(16)ꢀC(11)ꢀC(12)=119.4(19), C(16)ꢀC(11)ꢀ
Ge=116.63(15), C(12)ꢀC(11)ꢀGe=123.63(15).
1
groups in the H dimension were accidentally coinci-
dent at 2.06 ppm and the signals assigned to the
,
Fig. 2. Molecular structure of 11. Important bond lengths (A) and bond angles (°): Ge(1)ꢀO(1)=1.777(1), Ge(1)ꢀO(2)=1.785(l), Ge(1)ꢀC(21)=
1.968(2), Ge(1)ꢀC(11)=1.970(2), Ge(2)ꢀO(1)=1.804(1), Ge(2)ꢀC(31)=1.985(2), Ge(2)ꢀC(41)=1.988(2), Ge(2)ꢀGe(3)=2.504(3), Ge(3)ꢀO(2)=
1.808(1), Ge(3)ꢀC(51)=1.978(2), Ge(3)ꢀC(61)=1.982(2); O(1)ꢀGe(1)ꢀO(2)=102.79(6), O(1)ꢀGe(2)ꢀGe(3)=94.57(4), O(2)ꢀGe(3)ꢀGe(2)=
94.29(4), Ge(1)ꢀO(1)ꢀGe(2)=124.22(7), Ge(1)ꢀO(2)ꢀGe(3)=124.11(7).

134
M.S. Samuel et al. / Journal of Organometallic Chemistry 636 (2001) 130–137
Scheme 5.
with the previous conclusion that the rate of reaction of
the THF-complexed germylene with triethylsilane is
appreciably slower.
stated. Tetrahydrofuran was distilled freshly from
sodium/benzophenone ketyl prior to use. Toluene and
Et3SiH were distilled from LiAlH4 prior to use. m-
Chloroperbenzoic acid was obtained from the Aldrich
Chemical Co. Hexamesitylcyclotrigermane was pre-
pared following the published procedure [15]. Chro-
matography was carried out on silica gel preparative
plates obtained from BDH Co.
In summary, the oxidation of tetramesityldigermene
closely parallels the oxidation of tetraaryldigermenes la
and 1b. The direct addition of oxygen to digermenes yield
a 1,2-digermadioxetane which can photochemically (and,
possibly, thermally) rearrange to the 1,3-isomer. The
cophotolysis of the cyclotrigermane and oxygen pro-
duced a complex mixture of products, as a consequence
of the method used to generate the digermene and
competing photochemical processes. Interestingly, the
use of THF as a solvent reduced the complexity of these
reactions presumably because of the reduced reactivity of
the THF donor adduct of dimesitylgermylene.
It is interesting to compare the oxygenation of diger-
menes with their silicon analogues. There have been
several publications which describe the usual course of
the oxidation [14]. Typically, oxygenation of disilenes in
solution gives the 1,2-disiladioxetane as the major
product accompanied by a smaller quantity of the
disilaoxirane. The 1,2-dioxetanes undergo thermal rear-
rangement to give the corresponding 1,3-disiladioxe-
tanes. Direct formation of the 1,3-disiladioxetanes is also
observed.
Photolyses were carried out at 350 nm using a Rayo-
net Photochemical Reactor. Low temperature photoly-
ses were carried out by cooling the sample using an
Endocal model ULT-70 low temperature external bath
circulator to force cold (−70 °C) MeOH through a
vacuum jacketed Pyrex immersion well. Melting points
(m.p.) were measured using a Gallencamp metal block
apparatus and are uncorrected. NMR spectra were
1
recorded on a Varian Gemini 200 (200.1 MHz for H,
50.3 MHz for 13C), a Varian XL or a Gemini 300 (299.9
1
MHz for H, 75.4 MHz for 13C), or a Varian Inova 400
1
(399.8 MHz for H, 100.5 MHz for 13C) using benzene-
d6 as a solvent, unless otherwise noted. The standards
were as follows: residual C6D5H 7.15 ppm for 1H
spectra; C6D6 central transition 128.00 ppm for 13C-
NMR spectra. Literature 1H-NMR chemical shifts were
comparable to 90.01 ppm. IR spectra were recorded
(cm−1) as thin films on a Perkin–Elmer System 2000
FTIR spectrometer. A Finnigan MAT model 8200 in-
strument, with an ionizing voltage of 70 eV, was used
to obtain electron impact mass spectra reported in
mass-to-charge units, m/z, with ion identity and peak
intensities relative to the base peak in parentheses and
a Finnigan 4615B GC/MS quadrupole mass spectrome-
ter (San Jose, CA) was used to obtain potassium (K+)
ionisation of desorbed species (K+IDS) spectra. The
detailed experimental procedure to perform K+IDS has
been described elsewhere [16].
Dimetallenes with sterically demanding ligands, such
as the disilene, Tip2SiꢁSiTip2 (Tip=2,4,6-triisopropy-
lphenyl) and the digermene, Dep2GeꢁGeDep2 (Dep=
2,6-diethylphenyl) undergo the thermal rearrangement of
their 1,2-dimetalladioxetanes to compounds with the
1-oxa-2-metallacyclo-pent-3-ene structure. This type of
rearrangement has not been observed for less bulky
dimetallenes such as the mesityl-substituted dimetallenes.
3. Experimental
3.2. Addition of air to tetramesityldigermene in toluene
3.1. General
All experiments were carried out in flame-dried glass-
ware under an inert atmosphere of Ar, unless otherwise
Ge3Mes6 (50 mg, 0.054 mmol) and Et3SiH (0.1 ml,
excess) were dissolved in toluene (4 ml) and photolysed

M.S. Samuel et al. / Journal of Organometallic Chemistry 636 (2001) 130–137
135
(350 nm) at −70 °C for 16 h. After irradiation, the
reaction mixture was clear and bright yellow in colour.
Air was bubbled through the solution until the colour
completely faded (ꢀ30 s). The solvent was removed to
yield an oily white residue. The residue was analysed by
1H-NMR spectroscopy and it was found to be an
approximately 1:1 mixture of 7 and 8 [6f].
3.4.1. 2,2,4,4-Tetramesityl-2,4-digermadioxetane (9)
M.p.: 149–150 °C; IR (thin film, cm−1): 3364 (w),
2919 (m), 1603 (m), 1558 (s), 1449 (s), 1412 (m), 1377
1
(m), 846 (s), 803 (s); H-NMR: l 6.63 (s, 8H, Mes CH),
2.52 (s, 24H, Mes oCH3), 2.06 (s, 12H, Mes pCH3);
13C-NMR: l 143.21, 139.33, 135.21 (Mes C), 129.40
(Mes CH), 23.09 (Mes oCH3), 21.01 (Mes pCH3); MS;
m/z: 654 [M+, 15], 623 [M+−O2, 8], 535 [M+−Mes,
45], 415 [M+−Mes2, 32], 327 [Mes2GeO, 72], 311
[Mes2Ge, 28], 235 (38), 221 [MesGeOO, 32], 119 [Mes,
100], 105 [GeO2, 72]; K+IDS MS; m/z: 687–701 [M+
+39 cluster].
3.2.1. 3,3,4,4-Tetramesityl-3,4-digermadioxetane (7)
M.p.: 142–143 °C; 1H-NMR: l 6.62 (s, 8H, Mes
CH), 2.64 (s, 24H, Mes oCH3), 2.01 (s, 12H, Mes
pCH3); 13C-NMR: l 142.92, 139.82, 135.67 (Mes C),
129.25 (Mes CH), 22.64 (Mes oCH3), 21.09 (Mes
pCH3); MS; m/z: 654 [M+, 2], 632 [M+−O, 1], 533
[M+−Mes, 4], 516(4), 429 [GeMes3, 6], 415 [M+
−Mes2, 5], 311 [Mes2Ge, 12], 192 [MesGe, 20], 119
[Mes, 12], 84 (100); HRMS: Found, 654.179. Calc. for
C36H44 72Ge74GeO2: 654.177.
3.4.2. Tetramesityldigermaoxirane (10)
IR (thin film, cm−1): 3649 (w), 2923 (s), 2854 (s),
1718 (m), 1602 (m), 1558 (w), 1451(m), 1410 (w), 1378
(w), 1289 (m), 1031(m), 907 (w), 847 (m), 803 (w);
1H-NMR: l 6.67 (s, 8H, Mes CH), 2.41 (s, 24H, Mes
oCH3), 2.08 (s, 12H, Mes pCH3); 13C-NMR: l 143.56,
138.87, 138.08 (Mes C), 129.62 (Mes CH), 23.62 (Mes
oCH3), 20.95 (Mes pCH3); MS; m/z: 638 [M+, 13], 536
(9), 431 [Mes3Ge, 23], 329 [Mes2GeO, 100], 311
[Mes2Ge−H, 43], 192 [MesGe, 66], 119 [Mes, 93];
3.3. Addition of air to tetramesityldigermene in THF
Ge3Mes6 (63 mg, 0.068 mmol) and Et3SiH (0.1 ml,
excess) were dissolved in THF (4 ml) and photolysed
(350 nm) at −70 °C for 16 h. After irradiation, the
reaction mixture was clear and bright yellow in colour.
Air was bubbled through the solution until the colour
completely faded (ꢀ30 s). The solvent removed in
vacuo to yield 7 (59.6 mg, 89%) as an off-white crys-
talline solid.
HRMS: Found, 638.1827. Calc. for C36H Ge74GeO:
72
44
638.1825.
3.4.3. 2,2,4,4,5,5-Hexamesityl-2,4,5-trigermadioxolane
(11)
M.p. 302–303 °C; IR (thin film, cm−1): 2920 (m),
1603 (m), 1558 (w), 1457 (m), 1409 (m), 1378 (m), 847
1
3.4. Photolysis of hexamesitylcyclotrigermane in
(m), 809 (s); H-NMR: l 6.63 (s, 12H, Mes CH), 2.56
toluene under the ambient atmosphere
(s, 12H, Mes oCH3), 2.35 (s, 24H, Mes oCH3), 2.06 (s,
18H, Mes pCH3); 13C-NMR: l 143.27, 142.92, 141.25,
138.72, 138.50, 137.27 (Mes C), 129.27, 129.20 (Mes
CH), 24.67, 22.80 (Mes oCH3), 21.06, 20.97 (Mes
pCH3); MS; m/z: 966 [72Ge74Ge, M+−H, 12], 845
(84), 724 (22), 623 [Mes4Ge2−H, 46], 503
[Mes272Ge74GeMes, 31], 431 [GeMes3, 100], 311
[Mes2Ge−H, 91], 192 [MesGe, 21], 119 [Mes, 15];
Ge3Mes6 (50 mg, 0.054 mmol) and Et3SiH (0.1 ml,
excess) were dissolved in toluene (4 ml) and photolysed
(350 nm) at −70 °C for 16 h under the ambient
atmosphere. After irradiation, the reaction mixture was
clear and colourless. The solvent was removed under
1
vacuum from the reaction mixture. The H-NMR spec-
HRMS: Found, 965.263. Calc. for C54H Ge74Ge2O2
72
trum of the crude product showed varying amounts of
7–11 and an unidentified compound (1H-NMR: l 2.09,
2.37, 6.72). C6D6 (0.5 ml) was added to the crude
product. Compound 9 crystallised from the solution (5
mg, 14%) as clear, colourless crystals. The crystals were
filtered from the solution and the remaining products
were separated by preparative thin layer chromatogra-
phy (50/50 CH2Cl2–hexanes) to give 10 contaminated
with traces of 9 and 11 (5 mg, 15%) as a waxy white
solid and a mixture of 8 and 11 (14.7 mg). The solid 8
was air-oxidised to the germanol by allowing the ger-
mane to stand under the ambient atmosphere over a
period of at least 3 weeks. The resulting mixture was
separated by preparative thin layer chromatography
(30/70 CH2Cl2–hexanes) to give 11 (6.4 mg, 17%). The
dioxolane was recrystallised from hexanes to give 11 as
clear, colourless crystals.
66
−H+, 965.267.
3.5. Addition of m-chloroperbenzoic acid to
tetramesityldigermene in toluene
Ge3Mes6 (50 mg, 0.054 mmol) and Et3SiH (0.1 ml,
excess) were dissolved in toluene (4 ml) and photolysed
(350 nm) at −70 °C for 18 h. After irradiation, the
reaction mixture was clear and bright yellow in colour.
m-Chloroperbenzoic acid (12.2 mg, 85% pure, 0.060
mmol) dissolved in dried, degassed toluene (3 ml) was
added to the reaction mixture via cannula. Upon addi-
tion, the yellow colour of the reaction mixture faded to
clear and colourless. The reaction mixture was washed
with saturated Na2SO3 (30 ml total), followed by a
wash with water (30 ml total). The solvent was removed

136
M.S. Samuel et al. / Journal of Organometallic Chemistry 636 (2001) 130–137
under vacuum to yield a white residue (65 mg). The
products were separated by preparative thin layer chro-
matography (90/10 CH2Cl2–hexanes) to give 9 (3 mg,
9%), a small amount of 10 (1.6 mg, 5%), 11(7.8 mg,
15%), and an oily yellow product which has been
tentatively assigned as 12 (9.2 mg, 37%).
Diffraction data using a crystal with the dimensions of
0.32×0.32×0.12 mm were collected on a Nonius
Kappa-CCD diffractometer using COLLECT (Nonius,
1998) software. Of a total of 21 869 reflections collected
up to 2q=52.8° (05h515, 05k525, 05l518) in
ꢀ–2q mode using graphite monochromated Mo–Ka
radiation, 1868 were independent (Rint=0.057). These
data were corrected for absorption using the integration
method. Hydrogen atoms were calculated geometrically
and were either riding, or in the case of methyl groups,
riding as rigid groups on their respective carbon atoms.
There were four molecules in the unit cell and thus
symmetry was imposed on the molecule. Only one
mesitylene group needed to be refined and the germa-
nium atom and the oxygen atom were on special posi-
tions and given a site occupancy of 1/2. Similarly for
the benzene of solvation, only 112 carbon atoms were
found and the rest of the molecule was generated by
symmetry. Non-hydrogen atoms were refined an-
isotropically based on F2 by full-matrix least-squares
method. A molecular structure drawing is shown in Fig.
1. The X-ray crystallographic and processing parame-
ters are given in Table 1.
3.5.1. (Triethylsiloxydimesityl)germanol (12)
IR (thin film, cm−1): 3435 (s), 3023 (w), 2957 (m),
2921 (m), 2876 (m), 2052 (w), 1603 (m), 1653 (m), 1457
1
(m), 1261(m), 1021(m), 847 (m), 803 (m); H-NMR: l
6.72 (s, 4H, Mes CH), 2.49 (s, 12H, Mes oCH3), 2.10 (s,
6H, Mes pCH3), 0.89–0.98 (m, 15H, CH2CH3); MS;
m/z: 460 [M+, 3], 445 [M+−CH3, 9], 431 [M+
(72Ge)−CH2CH3,
31],
415
[M+(72Ge)−CH3,
−CH2CH3, −H, 36], 401 [M+(72Ge)−(CH2CH3)2,
−H, 24], 329 [Mes274GeOH, 51], 312 [Mes274Ge, 100],
192 [Mes74Ge−H, 94], 119 [Mes, 74].
3.6. Photolysis of hexamesitylcyclotrigermane in the
presence of 7
Ge3Mes6 (21.4 mg, 0.023 mmol) and 7 (15 mg, 0.023
mmol) were dissolved in toluene (4 ml) and photolysed
(350 nm) at −70 °C for 17 h. After irradiation, the
reaction mixture was clear and bright yellow in colour.
Methanol (1 ml, excess) was added to the cold reaction
mixture and the yellow colour completely faded. The
solvent was removed under vacuum to yield a pale
yellow solid (53.3 mg). The residue was analysed by
1H-NMR spectroscopy and found to be mainly a 1:2:4
mixture of 9, 11 and 13 [13].
Table 1
X-ray crystallographic and processing parameters for 9·C6H6 and
11·hexane
9·C6H6
11·hexane
Empirical formula
Colour, habit
C36H44Ge2O2·C6H6
colourless plates
0.71073
orthorhombic
Ccca
C54H66Ge3O2·C6H14
colourless block
0.71073
,
Wavelength (A)
Crystal system
triclinic
(
Space group
Crystal size (mm)
Unit cell dimensions
P1
0.32×0.32×0.12
0.34×0.27×0.26
3.7. Photolysis of hexamesitylcyclotrigermane in THF
under the ambient atmosphere
,
a (A)
12.0626(4)
20.5462(5)
14.7391(4)
90
90
90
4
12.8435(2)
13.0922(2)
16.2660(3)
83.2037(11)
85.2049(10)
83.0911(10)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
Ge3Mes6 (50 mg, 0.054 mmol) and Et3SiH (0.1 ml,
excess) were dissolved in THF (4 ml) and photolysed
(350 nm) at −70 °C for 16 h under the ambient
atmosphere. After irradiation, the reaction mixture was
clear and colourless. The solvent was removed under
Z
Diffractometer
Nonius Kappa-CCD Nonius Kappa-CCD
Method of collection ƒ–ꢀ Scans
Reflections collected 21 869
ƒ–ꢀ Scans
26 281
0.031
1
vacuum from the reaction mixture. The H-NMR spec-
Rint
0.057
trum of the crude product showed varying amounts of
7–11 and two, possibly three, other compounds which
could not be identified. C6D6 (0.5 ml) was added to the
crude product. Compound 9 crystallised from the solu-
tion (3.6 mg, 10%) as clear, colourless crystals. The
crystals were filtered from the solution and the remain-
ing products were separated by preparative thin layer
chromatography (CH2Cl2) to give 10 (2 mg, 6%) and 11
(15.2 mg, 29%).
2q Range for data
collection (°)
Absorption
6–53
3–53
1.68 Integration
1.706 Integration
coefficient (mm−1
and type
)
Data/restraints/
parameters
final R indices
[I\2|(I)]
1868/0/109
10 859/0/606
R1=0.0333,
wR2=0.0901
R1=0.0391,
wR2=0.0952
R1=0.0296,
wR2=0.0739
R1=0.0355,
wR2=0.0774
Full-matrix
R indices (all data)
Refinement method Full-matrix
3.8. X-ray structure determination of 9
least-squares on F2
Calc. geometrically
(riding model)
least-squares on F2
Calc. geometrically
(riding model)
Treatment of H
atoms
Colourless plate crystals of 9 were grown from a
concentrated benzene solution at room temperature.

M.S. Samuel et al. / Journal of Organometallic Chemistry 636 (2001) 130–137
137
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283.
3.9. X-ray structure determination of 11
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[6] For example see: (a) M.S. Samuel, M.C. Jennings, K.M. Baines,
Organometallics 20 (2001) 590;
Colourless plate crystals of 11 were grown from a
concentrated hexanes solution at room temperature.
Diffraction data using a crystal with the dimensions of
0.34×0.27×0.26 mm were collected on a Nonius
Kappa-CCD diffractometer using COLLECT (Nonius,
1998) software. Of a total of 26 281 reflections collected
up to 2q=52.8° (05h516, −165k516, −205
l520) in ꢀ–2qmode using graphite monochromated
Mo–Ka radiation, 10 859 were independent (Rint
=
(b) C.E. Dixon, M.R. Netherton, K.M. Baines, J. Am. Chem.
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(c) C.E. Dixon, J.A. Cooke, K.M. Baines, Organometallics 16
(1997) 5437;
(d) N.P. Toltl, W.J. Leigh, G.M. Kollegger, W.G. Stibbs, K.M.
Baines, Organometallics 15 (1996) 3732;
(e) T. Tsumuraya, Y. Kabe, W. Ando, J. Organomet. Chem. 482
(1994) 131;
(f) K.M. Baines, J.A. Cooke, J.J. Vittal, J. Chem. Soc. Chem.
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Netherton, Organometallics 13 (1994) 631;
(h) T. Tsumuraya, S. Sato, W. Ando, Organometallics 7 (1988)
2015.
0.031). These data were corrected for absorption using
the integration method. Hydrogen atoms were calcu-
lated geometrically and were either riding, or in the case
of methyl groups, riding as rigid groups on their respec-
tive carbon atoms. The hexane of solvation was well
behaved and refined satisfactorily. Non-hydrogen
atoms were refined anisotropically based on F2 by
full-matrix least-squares method. A molecular structure
drawing is shown in Fig. 2. The X-ray crystallographic
and processing parameters are given in Table 1.
[7] W. Ando, H. Itoh, T. Tsumuraya, H. Yoshida, Organometallics
7 (1988) 1880.
[8] G. Levin, P.K. Das, C. Bilgrien, C.L. Lee, Organometallics 8
(1989) 1206.
[9] G. Duverneuil, P. Mazerolles, E. Perrier, Appl. Organomet.
Chem. 8 (1994) 119.
[10] M. Lazraq, J. Escudie´, C. Couret, J. Satge´, M. Soufiaoui,
Organometallics 10 (1991) 1140.
[11] A.J. Millevolte, D.R. Powell, S.G. Johnson, R. West,
Organometallics 11 (1992) 1091.
[12] H. Puff, H. Heisig, W. Schuh, W. Schwab, J. Organomet. Chem.
303 (1986) 343.
[13] K.M. Baines, J.A. Cooke, Organometallics 10 (1991) 3419.
[14] (a) S. Willms, A. Grybat, W. Saak, M. Weidenbruch, H. Mars-
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(b) M. Weidenbruch, A. Pellman, S. Pohl, W. Saak, H. Mars-
mann, Chem. Ber. 128 (1995) 935;
4. Supplementary material
Crystallographic data for structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 158909 and 158910 for com-
pounds 11 and 9, respectively. Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(Fax: +44-1223-336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
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(d) K.L. McKillop, G.R. Gillette, D.R. Powell, R. West, J. Am.
Chem. Soc. 114 (1992) 5203;
We thank the NSERC (Canada) for financial support
and Dr W.J. Simonsick (Dupont Co., Philadelphia, PA)
for useful discussions and the K+IDS mass spectra.
(e) B.D. Shepherd, D.R. Powell, R. West, Organometallics 8
(1989) 2664;
(f) M.J. Michalczyk, M.J. Fink, K.J. Haller, R. West, J. Michl,
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