Versatile reactivity of the germene Mes2Ge=CR2 toward esters and related carbonyl derivatives

Article abstract of DOI:10.1021/om060917s

Dimesitylfluorenylidenegermane, MeS₂Ge=CR₂ (1; Mes -2,4,6-trimethylphenyl, CR₂ = fluorenylidene), undergoes a [2 + 4] cycloaddition with the C=CC=O system of α-ethylenic esters such as methyl acrylate, dimethyl maleate and dimethyl fumarate, and diethyl fumarate, leading to the 1,2-oxagerma-5-cyclohexenes 2 and 3a,b, respectively. With diethyl oxalate, maleic anhydride, and cyclopent-2-ene-1,3-dione [2 + 2] cycloadditions are observed between the Ge=C double bond and the carbonyl function, with formation of 1,2-oxagermetanes 4-6, respectively. In the last case, a double [2 + 2] cycloaddition on both CO groups to form a tricyclic compound occurs with excess germene. Germene 1 reacts exclusively by an ene reaction with 2-methyl-l,3-pentadione to give the corresponding (germyloxy)cyclopentenone 8.

Full text of DOI:10.1021/om060917s

Organometallics 2007, 26, 3729-3734
3729
Versatile Reactivity of the Germene Mes2GedCR2 toward Esters
and Related Carbonyl Derivatives
Sakina Ech-Cherif El Kettani,† Mohamed Lazraq,† Henri Ranaivonjatovo,‡ Jean Escudie´,*,‡
Heinz Gornitzka,‡ and Fatima Ouhsaine†,‡
Laboratoire d’Inge´nierie Mole´culaire et Organome´tallique (LIMOM), BP 1796, Faculte´ des Sciences Dhar
El Mehraz, UniVersite´ Sidi Mohamed Ben Abdellah, Fe`s-Atlas, Fe`s, Morocco, and He´te´rochimie
Fondamentale et Applique´e, UMR CNRS 5069, UniVersite´ Paul Sabatier, 118 route de Narbonne,
31062 Toulouse Cedex 09, France
ReceiVed October 6, 2006
Dimesitylfluorenylidenegermane, Mes2GedCR2 (1; Mes ) 2,4,6-trimethylphenyl, CR2 ) fluorenyl-
idene), undergoes a [2 + 4] cycloaddition with the CdCCdO system of R-ethylenic esters such as methyl
acrylate, dimethyl maleate and dimethyl fumarate, and diethyl fumarate, leading to the 1,2-oxagerma-
5-cyclohexenes 2 and 3a,b, respectively. With diethyl oxalate, maleic anhydride, and cyclopent-2-ene-
1,3-dione [2 + 2] cycloadditions are observed between the GedC double bond and the carbonyl function,
with formation of 1,2-oxagermetanes 4-6, respectively. In the last case, a double [2 + 2] cycloaddition
on both CO groups to form a tricyclic compound occurs with excess germene. Germene 1 reacts exclusively
by an ene reaction with 2-methyl-1,3-pentadione to give the corresponding (germyloxy)cyclopentenone
8.
Introduction
The isolation of compounds containing low-coordinate group
14 metal atoms, namely silicon, germanium, and tin analogues
of olefins, has been a major breakthrough in recent organome-
tallic chemistry. Unsaturated silicon, germanium, and tin
compounds show a heightened reactivity and constitute valuable
In contrast, the influence of another oxygen atom at the
carbonyl carbon atom, as in esters, is still relatively poorly
documented.4
Thus, we report in this paper the reactivity of dimesitylfluo-
renylidenegermane, Mes2GedCR2 (1;5 Mes ) 2,4,6-trimeth-
ylphenyl, CR2 ) fluorenylidene), toward various esters (R-
ethylenic esters and γ-diesters) and closely related carbonyl
derivatives such as anhydrides and a comparison with cyclic
diketones which have a similar structure.
building blocks for the synthesis of unusual derivatives by means
of addition or cycloaddition reactions onto a MdX double bond1
(M ) Si, Ge, Sn; X ) C, M, N, P). Thus, the behavior of the
silenes, germenes, and stannenes >MdC< toward carbonyl
compounds such as saturated aldehydes and ketones, R-ethylenic
aldehydes and ketones, and a quinone are well-known (for
reviews on the reactivity of carbonyl compounds, see refs 1f-h
(SidC), 1i-k (GedC), 2 (with references cited therein), and
3). Saturated aldehydes and ketones normally undergo [2 + 2]
reactions leading to four-membered heterocycles of type A,
except those with a mobile hydrogen atom lead to ene reactions
(type B) and R-unsaturated species give six-membered hetero-
cycles C by [2 + 4] reactions.
Results and Discussion
Methyl Acrylate, Dimethyl Maleate, Dimethyl Fumarate,
and Diethyl Fumarate. These derivatives theoretically offer
various possibilities of [2 + 2] or [2 + 4] cycloadditions with
the GedC double bond of germenes: a [2 + 2] cycloaddition
onto the CdO double bond, as with saturated aldehydes and
ketones,3a,b,d or onto the CdC double bond. Although 1 does
not react generally with alkenes, it could give a cycloadduct
with the activated CdC double bond of methyl acrylate. For
example, a [2 + 2] cycloaddition has been observed by Wiberg
between the CdC double bond of methyl vinyl ether and the
GedC double bond of the germene Me2GedC(SiMe3)2, leading
to a four-membered-ring heterocycle.3b A [2 + 4] cycloaddition
onto the conjugated CdCCdO system could also occur, as in
the case of R-ethylenic aldehydes and ketones.3c,d Such a [2 +
4] cycloaddition has been observed by Brook between a silene
† Universite´ Sidi Mohamed Ben Abdellah.
‡ Universite´ Paul Sabatier.
(1) For reviews, see: (a) Power, P. P. Chem. ReV. 1999, 99, 3463. (b)
Okazaki, R.; West, R. AdV. Organomet. Chem. 1996, 39, 231. (c) West, R.
Polyhedron 2002, 21, 467. (d) Sekiguchi, A.; Lee, V. Ya. Chem. ReV. 2003,
103, 1429. (e) Tokitoh, N. Acc. Chem. Res. 2004, 37, 86. (f) Brook, A. G.;
Baines, K. M. AdV. Organomet. Chem. 1986, 25, 1. (g) Brook, A. G.; Brook,
M. A. AdV. Organomet. Chem. 1996, 39, 71. (h) Mu¨ller, T.; Ziche, W.;
Auner, N. In The Chemistry of Organic Silicon Compounds; Rappoport,
Z., Apeloig, Y., Eds.; Wiley: Chichester, U.K., 1998; Vol. 2, Chapter 16,
p 857. (i) Barrau, J.; Escudie´, J.; Satge´, J. Chem. ReV. 1990, 90, 283. (j)
Baines, K.; Stibbs, W. G. AdV. Organomet. Chem. 1996, 39, 275. (k)
Escudie´, J.; Ranaivonjatovo, H. AdV. Organomet. Chem. 1999, 44, 113.
(2) Mosey, N. J.; Baines, K. M.; Woo, T. K. J. Am. Chem. Soc. 2002,
124, 13306.
(3) (a) Lazraq, M.; Couret, C.; Escudie´, J.; Satge´, J.; Dra¨ger, M.
Organometallics 1991, 10, 1771. (b) Wiberg, N.; Kim, Ch. K. Chem. Ber.
1986, 119, 2980. (c) Lazraq, M.; Escudie´, J.; Couret, C.; Satge´, J.; Soufiaoui,
M. Organometallics 1992, 11, 555. (d) Delpon-Lacaze, G.; Couret, C.;
Escudie´, J.; Satge´, J. Main Group Met. Chem. 1993, 16, 419. (e) Meiners,
F.; Haase, D.; Koch, R.; Saak, W.; Weidenbruch, M. Organometallics 2002,
21, 3990.
(4) Brook, A. G.; Hu, S. S.; Saxena, A. K.; Lough, A. J. Organometallics
1991, 10, 2758.
(5) (a) Couret, C.; Escudie´, J.; Satge´, J.; Lazraq, M. J. Am. Chem. Soc.
1987, 109, 4411. (b) Lazraq, M.; Escudie´, J.; Couret, C.; Satge´, J.; Dra¨ger,
M.; Dammel, R. Angew. Chem., Int. Ed. Engl. 1988, 27, 828.
10.1021/om060917s CCC: $37.00 © 2007 American Chemical Society
Publication on Web 06/22/2007

3730 Organometallics, Vol. 26, No. 15, 2007
Ech-Cherif El Kettani et al.
Scheme 1
derivatives are stable toward air and moisture, probably owing
to the high steric hindrance.
Thus, germene 1 appears to be much more reactive toward
R-ethylenic esters, such as methyl acrylate, dialkyl fumarates,
and dialkyl maleates, than toward saturated esters since, under
the same experimental conditions of solvent or temperature, no
reaction was observed between 1 and diethyl malonate or
PhCOOMe. Note that, even with an excess of germene, no
further reaction was observed with the thus nonconjugated
COOR moiety of 3.
Diethyl Oxalate. Between 1 and diethyl oxalate, an R-diester
with two conjugated CO groups (OdCCdO instead of OdCCd
C, as was used previously), two types of reactions could
theoretically occur: a [2 + 4] cycloaddition of the GedC double
bond with the OdCCdO system, leading to a six-membered
heterocycle, and a [2 + 2] cycloaddition between GedC and
CdO, with one or both CdO units leading to four-membered-
ring compounds. Only the reaction between one CO group and
the unsaturated GedC bond occurred, leading to the oxager-
metane 4, substituted by a COOEt moiety (eq 1).
Chart 1
and various acrylates, maleates, and fumarates, leading to six-
membered-ring derivatives with the oxygen bonded to the silicon
atom.4
The 13C NMR signal at 168.14 ppm indicates that one CdO
moiety is still present. Even with an excess of germene, only
the formation of the monoadduct 4 could be evidenced. Thus,
when one ester function has reacted, the second one becomes
inert toward the germene under the conditions of the reaction,
as in the previous case of 3, confirming again that the activation
of the ester function, here by a vicinal carbonyl group, is
necessary.
Maleic Anhydride, 4-Cyclopentene-1,3-dione, and 2-Meth-
yl-1,3-cyclopentanedione. After R-ethylenic esters and R-di-
esters, we have examined the reactivity of anhydrides. It
appeared interesting to us to compare the reactivity of this
anhydride to that of closely related derivatives (same five-
membered-ring structures with two CO groups in a â-position)
which possess a ketonic function.
Unlike R-ethylenic esters such as acrylates, maleates, and
fumarates, maleic anhydride and 4-cyclopentene-1,3-dione
feature a rigid transoid CdCCdO system, preventing a [2 +
4] cycloaddition with the GedC double bond. Thus, an exclusive
[2 + 2] cycloaddition between the GedC and the CdO
unsaturations occurred, leading to oxagermetanes 5 and 6
(Scheme 2).
The presence of the CHdCH moiety with nonequivalent
ethylenic protons at 5.77/7.17 ppm (JHH ) 5.5 Hz) for 5 and
5.89/8.55 ppm (3JHH ) 6 Hz) for 6 in the 1H NMR spectra and
of signals at 169.35 ppm for 5 (lactonic carbon atom) and 206.8
ppm for 6 (CdO group) in the 13C NMR spectra shows that
only one CdO group has reacted.
Among all of these possibilities of reactions, only the [2 +
4] cycloaddition between germene 1 and the conjugated system
of methyl acrylate, dimethyl maleate, dimethyl fumarate, and
diethyl fumarate was observed with the clean formation of 1,2-
oxagerma-5-cyclohexenes 2 and 3a,b, respectively (Scheme 1).
The unique regiochemistry involving the oxygen atom bonded
to the germanium atom probably arises from the anticipated
polarities of the germene double bond and of the R,â-unsaturated
system, as commmonly prevails in [2 + 4] cycloadditions. The
reverse regiochemistry occurring from the Brook silene, which
has two electropositive silicon atoms on the metal and an oxygen
atom on the sp2 carbon and, thus, is electronically very different
from germene 1, has been explained in terms of predominant
frontier orbital interactions.4
The structures of 2 and 3a,b were determined by their
physicochemical analysis such as 13C NMR spectroscopy with
characteristic chemical shifts for the O2CdCH pattern (159-
160 and 68-70 ppm, respectively); the C9 carbon atom (see
Chart 1 for the numbering scheme) of the CR2 group resonates
between 48 and 50 ppm, in the expected range for such a carbon
atom of a fluorenylidene group bonded to a germanium and a
carbon atom. In the case of the reverse regiochemistry, this C9
atom would be bonded to an oxygen atom and should display
a chemical shift at lower field, between 80 and 100 ppm. In
the mass spectrometry of 3, the fragment at m/z 329 corresponds
to Mes2GeO + 1 and provides further support to the regio-
chemistry of the reaction, which has been unambiguously
established by a X-ray structure determination. These data
clearly confirm the expected regiochemistry of the addition,
which is probably influenced by the well-known oxophilic
character of germanium and the polarities of the reactants
(Geδ+dCδ- and Cδ+dCCdOδ-).
In contrast with the case of maleic anhydride, a double [2 +
2] cycloaddition occurs between the second CdO group of
4-cyclopentene-1,3-dione and the GedC double bond when the
reaction is carried out with 2 equiv of germene 1, leading to
derivative 7. Only one diastereoisomer was formed with the
two oxagermetane rings in a trans position in relation to the
cyclopentene mean plane, since the methylene protons appear
to be equivalent in the 1H NMR spectrum (singlet at 1.97 ppm).
Although the Ge-O bond, and particularly the GeOCdC
moiety, are generally extremely sensitive to water, these

ReactiVity of the Germene Mes2GedCR2
Organometallics, Vol. 26, No. 15, 2007 3731
Scheme 2
This reaction confirms again the greater reactivity of germene
toward ketones than toward esters.
A completely different reaction occurs between germene 1
and 2-methyl-1,3-cyclopentanedione, leading exclusively to the
(germyloxy)cyclopentenone 8. In contrast to the case of maleic
anhydride and 4-cyclopentene-1,3-dione, the [2 + 2] cycload-
dition of the GedC double bond with the carbonyl group was
not observed. Thus, the ene reaction is faster than the [2 + 2]
cycloaddition between the GedC moiety and the carbonyl
group; such a reaction is not surprising, since an ene reaction
has previously been observed between 1 and acetone, leading
after the Lutsenko rearrangement6 to the germyl ketone 93a (eq
2).
Figure 1. Molecular structure of 3a (thermal ellipsoids at the 50%
probability level). H atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Ge-O1 ) 1.843(2), C1-O1 )
1.323(4), C1-O2 ) 1.367(3), C1-C2 ) 1.328(4), C2-C3 )
1.502(4), C3-C7 ) 1.586(4), Ge-C7 ) 2.017(3), Ge-C20 )
1.960(3), Ge-C29 ) 1.970(3), C3-C5 ) 1.519(4); C7-Ge-O1
) 98.50(11), C1-O1-Ge ) 123.7(2), O1-C1-C2 ) 127.8(3),
C1-C2-C3 ) 122.0(3), C3-C7-Ge ) 102.7(18).
Such a germanotropic rearrangement is not observed in the
case of the (germyloxy)cyclopentenone 8, due to both steric
reasons and the presence of the conjugated OdCCdC moiety.
1H and 13C Spectroscopic Studies. Sharp signals for the
ortho methyl groups of the equivalent mesityl groups are
1
observed in the H NMR spectrum of 8, indicating that the
germanium atom is not included in a cyclic structure.
Mass Spectrometry. The mass spectra of both four- and six-
membered heterocycles by EI at 70 eV (or by DCI/NH3 for 7)
showed some similarities: the molecular peak was observed
(except for 3b), and fragments corresponding to the germylene
Mes2Ge and to the starting germene Mes2GedCR2 were also
found. In the case of 3b, fragmentations leading to both
Mes2GedCR2 and to Mes2GedO appeared. The only exception
is 6, in which only the Mes2GedO fragment was observed; such
a [2 + 2] fragmentation leading to a germanone and to an alkene
is classic in oxagermetane rings.7
X-ray Crystallographic Analyses. The structures of 3a, 5,
and 8 have been determined by a X-ray study. The main feature
is the lenghtening of the Ge-CR2 and Ge-O bonds due to the
large steric congestion: 1.997-2.0227 and 1.819-1.863 Å,
respectively (standard Ge-C and Ge-O bond lengths lie
generally in the ranges 1.94-1.988 and 1.73-1.79 Å, respective-
ly).8a In the six-membered ring of oxagermacyclohexene 3a
In contrast, in the four- and six-membered-ring heterocycles
3-7, extremely broad signals are observed for ortho methyl
groups (half-width up to 120 Hz for 5). As the two mesityl
groups are nonequivalent, due to the presence of an asymmetric
carbon atom, extremely different chemical shifts (0.91 and 2.61
ppm for the two ortho methyl groups of the same mesityl in 5)
are observed, due to their special positions in relation to different
groups; this is due to a hindered rotation on the NMR time scale
caused by the large steric hindrance. Whereas this hindered
rotation is observed for all the mesityl groups of 3, 6, and 7, it
is not the case for derivatives 4 and 5, in which one broad singlet
was observed for the two ortho methyl groups of one Mes group
and two broad singlets were observed for the ortho methyl
groups of the other one, indicating a hindered rotation of only
one mesityl on the NMR time scale (possibly the Mes in a cis
position in relation to the COOEt group in 4 and to the OCO
moiety in 5). The two para methyl groups of the mesityl groups
appear as sharp singlets, since they are not influenced by the
slow or hindered rotation around the Ge-C(Mes) bond.
(7) (a) Rivie`re, P.; Castel, A.; Satge´, J. J. Am. Chem. Soc. 1980, 102,
5413. (b) Marchand, A.; Gerval, P.; Duboudin, F.; Joanny, M.; Mazerolles,
P. J. Organomet. Chem. 1984, 267, 93. (c) Barrau, J.; Rima, G.; El Amine,
M.; Satge´, J. Synth. React. Inorg. Met.-Org. Chem. 1988, 18, 317.
(8) (a) Baines, K. M.; Stibbs, W. G. Coord. Chem. ReV. 1995, 145, 157.
(b) Holloway, C. E.; Melnik, M. Main Group Met. Chem. 2002, 25, 185.
(6) (a) Lutsenko, I. F.; Foss, V. L.; Semenenko, N. M. Zh. Obshch. Khim.
1969, 39, 1174. (b) Semenenko, N. M.; Foss, V. L.; Lutsenko, I. F. Zh.
Obshch. Khim. 1971, 41, 2458.

3732 Organometallics, Vol. 26, No. 15, 2007
Ech-Cherif El Kettani et al.
Figure 3. Molecular structure of 8 (thermal ellipsoids at the 50%
probability level). H atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Ge-O1 ) 1.819(4), O1-C1 )
1.344(8), Ge-C7 ) 2.017(7), Ge-C20 ) 1.961(7), Ge-C29 )
1.975(6), C1-C2 ) 1.334(8), C2-C3 ) 1.433(10), C3-C4 )
1.532(9), C4-C5 ) 1.529(9), C5-C1 ) 1.515(8); Ge-O1-C1
) 128.2(4), C7-Ge-C20 ) 106.9(2), C7-Ge-O1 ) 101.3(2),
C7-Ge-C29 ) 124.8 (3), C20-Ge-C29 ) 110.9(3), C20-Ge-
O1 ) 107.3(3), C29-Ge-O1 ) 104.0(2).
Figure 2. Molecular structure of 5 (thermal ellipsoids at the 50%
probability level). H atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Ge-C5 ) 2.0227(17), Ge-O1 )
1.8631(12), O1-C1 ) 1.400(2), C1-C5 ) 1.561(2), Ge-C18 )
1.9548(17), Ge-C27 ) 1.9519(17), C1-C4 ) 1.508(2), C1-O3
) 1.461(2), C4-C3 ) 1.318(3), C3-C2 ) 1.478(3), C2-O3 )
1.365(2), C2-O2 ) 1.199(2); Ge-C5-C1 ) 83.17(10), Ge-O1-
C1 ) 93.81(9), O1-C1-C5 ) 102.96(13), C5-Ge-O1 ) 73.12-
(6), C18-Ge-C27 ) 115.21(7), C5-Ge-C27 ) 120.63(7), C5-
Ge-C18 ) 117.62(7), O1-Ge-C27 ) 110.37(6), O1-Ge-C18
) 111.31(7).
the quasi-planar C(1)-C(5) five-membered ring and the fluo-
renyl group (angle between these two planes: 10°) and an
acyclic Ge-O bond (1.819(4) Å) shorter than the intracyclic
ones in 3 (1.843(2) Å) and 5 (1.863(1) Å).
In conclusion, dimesitylfluorenylidenegermane (1) behaves
as an extremely reactive and versatile partner toward various
carbonyl derivatives and constitutes a very useful building block
in organogermanium chemistry. It reacts with esters activated
by a CdC double bond or by a carbonyl group but is unreactive
when they are not activated, in contrast to the case of closely
related ketones which undergo a [2 + 2] cycloaddition or an
ene reaction.
(Figure 1), the five atoms Ge, O(1), C(1), C(2), and C(3) are
approximately in a plane; the mean deviation in relation to this
mean plane is 0.05 Å, and the maximum deviation is 0.08 Å
for O(1). The angle between the mean plane GeO(1)C(1)C-
(2)C(3) and the plane GeC(7)C(3) is 50.2°. Derivative 5 (Figure
2) exhibits, as expected from the steric congestion of the four-
membered ring, the longest intracyclic Ge-O and Ge-CR2
bonds; in the distorted oxagermetane ring, the angle between
the planes C(5)C(1)O(1)/C(5)Ge(1)O(1) and C(1)C(5)Ge(1)/Ge-
(1)O(1)C(1) are 28.4 and 27.7°, respectively. The folding is
higher than in other oxagermetanes obtained from 1 and
benzaldehyde or benzophenone (23 and 12°, respectively)3a and
in an oxagermetane featuring an exocyclic PdC double bond
obtained from the phosphagermaallene -PdCdGe< and fluo-
renone (18.7 and 18.9°).9 More acute bond angles are generally
observed in oxasiletanes10 or in symmetrical 1,3,2,4-dioxadi-
germetanes11 and wider fold angles in 1,3-digermazanes (34-
38°)12 and in cyclobutanes. The angle between the four-
membered and the planar five-membered rings at the C(1)
carbon atom (planes C(5)C(1)O(1) and C(4)C(1)O(3)) is 88.4°,
close to the ideal 90°. The small angle O(1)-Ge(1)-C(5)
(73.12(6)°) at the germanium atom is in the range of similar
angles reported in other four-membered heterocycles (74.1°
in a 1,3,2,4-dioxadigermetane,11 75 and 75.6° in a 1,2-
oxagermetane,3a and 75° in a 1,2-phosphagermetane).13 In 8
(Figure 3), the main features are the near parallelism between
Experimental Section
General Procedures. All manipulations were carried out under
N2 or Ar using standard Schlenk techniques with solvents freshly
distilled from sodium benzophenone. 1H and 13C NMR spectra were
recorded in CDCl3 on Bruker AC 250 and Avance 300 instruments
at 250.13 and 300.13 MHz (1H) and 75.47 MHz (13C), respectively.
Mass spectra were measured on a Hewlett-Packard 5989 A
spectrometer by EI at 70 eV and on a Nermag R10-10 spectrometer
by CI (NH3). Melting points were determined on a Leitz microscope
heating stage 250. IR spectra were recorded on a Perkin-Elmer 1600
FT-IR spectrometer. Elemental analyses were performed by the
“Service de Microanalyse de l’Ecole de Chimie de Toulouse”.
For the 1H and 13C NMR study, the carbon atoms of the fluorenyl
group are numbered as shown in Chart 1.
Synthesis of Germene 1. Germene 1 was prepared as previously
described3 by addition of 1 mol equiv of tert-butyllithium (1.7 M
in pentane) to a solution of the fluorogermane Mes2Ge(F)CHR2
(1.00 g, 2.02 mmol) in Et2O (20 mL) cooled to -78 °C. Warming
to room temperature afforded an orange solution of 1 with a
precipitate of LiF. According to a 1H NMR experiment, 1 is
produced in a nearly quantitative yield. Thus, all reactions were
performed on the crude reaction mixture containing LiF without
isolation of 1.
(9) El Harouch, Y.; Gornitzka, H.; Ranaivonjatovo, H.; Escudie´, J. J.
Organomet. Chem. 2002, 643-644, 202.
(10) (a) Brook, A. G.; Chatterton, W. J.; Sawyer, J. F.; Hughes, D. W.;
Vorspohl, K. Organometallics 1987, 6, 1246. (b) Brook, A. G.; Vorspohl,
K.; Ford, R. R.; Hesse, M.; Chatterton, W. J. Organometallics 1987, 6,
2128.
(11) Masamune, S.; Batcheller, S. A.; Park, J.; Davis, W. M.; Yamashita,
O.; Ohta, Y.; Kabe, Y. J. Am. Chem. Soc. 1989, 111, 1888.
(12) Lazraq, M.; Couret, C.; Declercq, J. P.; Dubourg, A.; Escudie´, J.;
Rivie`re-Baudet, M. Organometallics 1990, 9, 845.
(13) Andrianarison, M.; Couret, C.; Declercq, J.-P.; Dubourg, A.; Escudie´,
J.; Satge´, J. J. Chem. Soc., Chem. Commun. 1987, 921.
General Procedure for the Reactions of 1 with Carbonyl
Compounds. To the reaction mixture of 1 and LiF cooled to -78
°C was added 1 equiv of the carbonyl reagent, neat (if liquid) or in

ReactiVity of the Germene Mes2GedCR2
Organometallics, Vol. 26, No. 15, 2007 3733
solution in Et2O or toluene (when solid) via syringe. After the end
of the addition, the reaction mixture was slowly warmed to room
temperature and stirred overnight, to lead to a yellow solution
(except for other colors when indicated). A 1H and 13C NMR study
of the crude solution showed in all cases the complete reaction of
1 and the unique formation of one type of adduct. The solvents
were removed under reduced pressure, 30 mL of pentane was added,
and LiF was removed by filtration. The yields in the cycloadducts
were calculated from isolated crystals (after crystallization at -20
°C in pentane) from the starting Mes2Ge(F)CHR2.
(OCdCH), 171.34 (COOEt). MS (EI, 70 eV, m/z): 477 (Mes2-
GedCR2 + H, 2), 329 (Mes2GeO + H, 5), 313 (Mes2Ge + H,
10), 165 (CHR2, 100). IR: ν(CO), 1742.4 cm-1; ν(CdC), 1605.3
cm-1. Anal. Calcd for C39H42GeO4 (647.350): C, 72.36; H, 6.54.
Found: C, 71.82; H, 6.30.
Synthesis of 4 (1 and Diethyl Oxalate). Yield: 1.04 g (79%)
of white crystals of oxagermetane 4 (mp 180 °C). 1H NMR (250.13
3
MHz): δ 0.39 (t, JHH ) 7.2 Hz, 3H, OCH2CH3), 0.88 (broad s,
3
3H, o-Me of Mes), 1.21 (t, JHH ) 7.2 Hz, 3H, OCH2CH3), 2.19
(s, 3H, p-Me of Mes), 2.24 (broad s, 6H, o-Me of Mes), 2.31 (s,
3H, p-Me of Mes), 2.70 (broad s, 3H, o-Me of Mes), 3.25 and
4.17 (2 dq, 2JHH ) 7.2 Hz, 3JHH ) 7.2 Hz, 2 × 1H, CHH′CH3 and
CHH′CH3 for one Et group), 3.46 and 3.80 (2 dq, 2JHH ) 10.7 Hz,
3JHH ) 7.3 Hz, 2 × 1H, CHH′CH3 and CHH′CH3 for the other Et
group), 6.35-6.80 (very broad s, 2H, arom H of Mes), 6.83 (s,
2H, arom H of Mes), 7.05 (1H), 7.16 (1H), and 7.36 (2H) (3 t,
3JHH ) 7.6 Hz, H2,3,6,7 of CR2), 7.28, 7.43, 7.24, and 7.99 (4 d,
3JHH ) 7.6 Hz, 4 × 1H, H1,4,5,8 of CR2). 13C NMR (75.47 MHz):
δ 13.13 and 14.78 (OCH2CH3), 21.01 and 21.13 (p-Me of Mes),
22.84 (o-Me of Mes), 59.51 and 60.32 (OCH2CH3), 70.20 (CR2),
106.14 (OCO), 119.24 and 119.31 (C4,5), 124.05, 126.52, 126.56,
126.67, 126.81, and 128.20 (C1-3, C6-8 of CR2), 128.60 (broad
s) and 129.18 (m-C of Mes), 131.33 and 131.72 (ipso-C of Mes),
139.85, 139.89, 140.01, 140.22, 141.15, 143.19, and 144.13 (C10-
13, o- and p-C of Mes), 168.14 (CO). MS (EI, 70 eV, m/z): 622
(M, 3), 577 (M - OEt, 5), 476 (Mes2GedCR2, 10), 357 (MesGed
CR2, 20), 311 (Mes2Ge - H, 60), 220 (R2CCOEt - H, 25), 165
(CHR2, 100). IR: ν(CO), 1725.4 cm-1. Anal. Calcd for C37H40-
GeO4 (621.312): C, 71.53; H, 6.49. Found: C, 71.52; H, 6.20.
Synthesis of 2 (1 and Methyl Acrylate). Yield: 1.01 g (85%)
of white crystals of oxagermacyclohexene 2 (mp 220 °C). 1H NMR
(300.13 MHz): δ 1.30-3.20 (extremely broad m, 20H, Me of Mes
3
and CH2), 3.71 (s, 3H, OMe), 3.89 (t, JHH ) 5.2 Hz, 1H, CHd),
6.73 (very broad s (half-width 40 Hz), 4H, arom H of Mes), 7.12-
3
7.44 (m, 6H, arom H of CR2), 7.81 (d, JHH ) 7.9 Hz, 2H, H on
C1,8 or C4,5 of CR2). 13C NMR (75.47 MHz): δ 20.99 (p-Me of
Mes), 22.72 (o-Me of Mes), 34.31 (CH2), 48.42 (CR2), 54.60
(OMe), 68.72 (CHd), 119.72 (C4,5), 125.03, 126.67, 126.92,
129.28 (C1-3, C6-8, m-CH of Mes), 134.41, 139.38, 140.47,
148.38 (ipso-, o-, and p-C of Mes and C10-13), 160.23 (OCd).
MS (EI, 70 eV, m/z): 562 (M, 3), 476 (Mes2GedCR2, 65), 311
(Mes2Ge - H, 100). Anal. Calcd for C35H36GeO2 (561.260): C,
74.90; H, 6.47. Found: C, 75.05; H, 6.60.
Synthesis of 3a (1 and (Z)- and (E)-MeOOCCHdCHCOOMe).
(a) Dimethyl maleate: yield 0.87 g (70%) of white crystals of
oxagermacyclohexane 3a (mp 209 °C). (b) Dimethyl fumarate:
yield 0.97 g (78%). 1H NMR (300.13 MHz): δ 0.70 (broad s, 3H,
o-Me of Mes), 1.40 (very broad s (half-width 45 Hz), 3H, o-Me of
Mes), 2.04 and 2.27 (2 s, 2 × 3H, p-Me of Mes), 2.34 (broad s,
3H, o-Me of Mes), 2.70 (very broad s (half-width 40 Hz), 3H, o-Me
of Mes), 2.83 and 3.67 (2 s, 2 × 3H, OMe), 3.84 and 4.34 (2 d,
3JHH ) 2.4 Hz, 2 × 1H, OCdCHCHCOOMe), 6.38 and 6.65 (2
broad s, 2 × 2H, arom H of Mes), 6.73, 7.55, 7.71, and 7.73 (4 d,
3JHH ) 7.6 Hz, 4 × 1H, H1,4,5,8 of CR2), 7.01, 7.20, 7.26, and
Synthesis of 5 (1 and Maleic Anhydride). The carbonyl
compound was dissolved in Et2O, and the reaction mixture turned
green and then turquoise blue. Yield: 0.87 g (75%) of white crystals
1
of oxagermetane 5 (mp 243 °C). H NMR (250.13 MHz): δ 0.91
(broad s, 3H, o-Me of Mes), 2.20 (extremely broad s (half-width
120 Hz), 6H, o-Me of Mes), 2.23 and 2.32 (2 s, 2 × 3H, p-Me of
3
7.33 (4 t, JHH ) 7.6 Hz, 4 × 1H, H2,3,6,7 of CR2). 13C NMR
3
Mes), 2.61 (broad s, 3H, o-Me of Mes), 5.77 (d, JHH ) 5.5 Hz,
(75.47 MHz): δ 20.79 and 21.08 (p-Me of Mes), 22.74 (o-Me of
Mes), 48.69, 51.08, and 54.77 (CHCR2 and 2 OCH3), 50.31 (CR2),
69.16 (OCdCH), 119.36 and 119.53 (C4,5), 125.07, 125.87, 126.11,
126.29, 126.87, 127.02, 127.14, and 129.70 (C1-3, C6-8, and
m-C of Mes), 133.30 and 134.24 (ipso-C of Mes), 139.27, 139.98,
141.13, 141.80, 143.85, and 145.60 (C10-13, o- and p-C of Mes),
160.16 (OCdCH), 171.72 (COOEt). MS (EI, 70 eV, m/z): 620
(M, 2), 606 (M - Me + H, 1), 589 (M - OMe, 2), 561 (M -
COOMe, 1), 476 (Mes2GedCR2, 100), 311 (Mes2Ge - H, 90),
165 (CHR2, 30). Anal. Calcd for C37H38GeO4 (619.296): C, 71.76;
H, 6.18. Found: C, 71.92; H, 6.20.
1H, dCHCdO), 6.58 (broad s, 1H, arom H of Mes), 6.87 (broad
3
s, 3H, arom H of Mes), 7.17 (d, JHH ) 5.5 Hz, 1H, OCCHd),
7.16, 7.23, 7.34, and 7.39 (4 t, 3JHH ) 7.6 Hz, 4 × 1H, H2,3,6,7 of
3
CR2), 7.46, 7.66, 7.77, and 7.80 (4 d, JHH ) 7.6 Hz, 4 × 1H,
H1,4,5,8 of CR2). 13C NMR (75.47 MHz): δ 21.04, 21.09, 22.16,
22.61, and 22.93 (o- and p-Me of Mes), 70.95 (CR2), 116.12 (CO2),
119.46 and 120.16 (C4,5 of CR2), 122.90, 124.26, 127.12, 127.49,
and 127.70 (C1-3, C6-8 of CR2, OdCCHd), 128.55 and 129.05
(2 broad s, m-CH of Mes), 130.53 and 131.20 (ipso-C of Mes),
139.10, 139.68, 140.31, 140.43, 140.62, 142.25, 143.04, and 143.60
(C10-13 of CR2, o- and p-C of Mes), 152.14 (O-CCHd), 169.35
(CdO). MS (EI, 70 eV, m/z): 574 (M, 5), 476 (Mes2GedCR2,
10), 411 (M - Mes - CO2, 7), 311 (Mes2Ge - H, 20), 246 (M -
Mes2GeO, 45), 218 (M - Mes2GeO - CO, 50), 193 (MesGe, 50),
189 (M - Mes2Ge - CO2 - CO - H, 100), 165 (CHR2, 60), 44
(CO2, 65). IR: ν(CO), 1695.0 cm-1. Anal. Calcd for C35H32GeO3
(573.227): C, 73.34; H, 5.63. Found: C, 73.52; H, 5.86.
Synthesis of 3b (1 and Diethyl Fumarate, (Z)-EtOOCCHd
CHCOOEt). Yield: 0.97 g (71%) of white crystals of 3b (mp 170
3
°C). 1H NMR (300.13 MHz): δ 0.40 (t, JHH ) 7.2 Hz, 3H,
OCH2CH3), 0.68 and 1.18 (2 broad s, 2 × 3H, o-Me of Mes), 1.26
3
(t, JHH ) 7.2 Hz, 3H, OCH2CH3), 2.01 and 2.24 (2 s, 2 × 3H,
p-Me of Mes), 2.31 (broad s, 3H, o-Me of Mes), 2.72 very broad
2
3
s, o-Me of Mes), 3.28 (AB q, JHH ) 9.0 Hz, JHH ) 7.2 Hz, 1H,
2
3
Synthesis of 6 (1 and 4-Cyclopentene-1,3-dione, 1:1 Molar
Ratio). The carbonyl compound was dissolved in toluene. Yield:
0.92 g (80%) of white crystals of oxagermetane 6 (mp 205 °C). 1H
NMR (300.13 MHz): δ 0.94 and 1.48 (2 broad s, 2 × 3H, o-Me
of Mes), 2.14 (d, 2JHH ) 18.6 Hz, 1H, CHH′), 2.16 and 2.27 (2 s,
2 × 3H, p-Me of Mes), 2.58 (broad s, 3H, o-Me of Mes), 2.60 (d,
2JHH ) 18.6 Hz, 1H, CHH′), 2.85 (broad s, 3H, o-Me of Mes),
5.89 (d, 3JHH ) 6.0 Hz, 1H, OdCCHd), 5.90, 6.51, 6.65, and 6.81
(4 broad s, 4 × 1H, arom H of Mes), 7.00-7.13 (m, 2H, arom H
of CR2), 7.25-7.32 (m, 3H, arom H of CR2), 7.54, 7.71, and 7.74
OCHAHBCH3), 3.29 (AB q, JHH ) 9.0 Hz, JHH ) 7.2 Hz, 1H,
3
OCHAHBCH3), 3.89 and 4.31 (2 d, JHH ) 2.4 Hz, 2 × 1H, OCd
CHCHCOOEt), 3.92 (q, 3JHH ) 7.2 Hz, 2H, OCH2CH3), 6.33 and
6.60 (2 broad s, 2 × 2H, arom H of Mes), 6.73, 7.59, 7.68, and
3
7.69 (4 d, JHH ) 7.6 Hz, 4 × 1H, H1,4,5,8 of CR2), 6.97, 7.16,
7.23, and 7.30 (4 t, 3JHH ) 7.6 Hz, 4 × 1H, H2,3,6,7 of CR2). 13
C
NMR (75.47 MHz): δ 13.31 and 14.96 (OCH2CH3), 21.08 and
21.11 (p-Me of Mes), 22.74 and 22.88 (o-Me of Mes), 48.73
(CHCR2), 50.44 (CR2), 59.90 and 62.84 (OCH2CH3), 70.61 (OCd
CH), 119.31 and 119.48 (C4,5), 125.29, 126.26, 126.31, 126.81,
127.04, and 127.15 (C1-3, C6-8), 128.55 and 129.71 (m-C of
Mes), 133.54 and 134.57 (ipso-C of Mes), 139.23, 139.92, 141.26,
142.56, 144.03, and 145.86 (C10-13, o- and p-C of Mes), 159.05
3
(3 d, JHH ) 7.8 Hz, 3 × 1H, H on C1, C4, C5, or C8), 8.15 (d,
3JHH ) 6.0 Hz, 1H, OCCHd). 13C NMR (75.47 MHz): δ 21.00
and 21.08 (p-Me of Mes), 22.38, 22.71, and 23.32 (o-Me of Mes),

3734 Organometallics, Vol. 26, No. 15, 2007
Ech-Cherif El Kettani et al.
Table 1. Crystal Data for 3a, 5, and 8
3a
5
8
empirical formula
formula wt
temp (K)
cryst syst
space group
a (Å)
C37H38GeO4
619.26
173(2)
monoclinic
Pn
11.3333(13)
9.0086(10)
15.1704(18)
C35H32GeO3
573.20
133(2)
monoclinic
P21/n
11.4843(7)
21.4191(13)
11.6183(7)
C37H38GeO2
587.26
173(2)
triclinic
P1h
9.861(2)
b (Å)
c (Å)
10.976(2)
15.163(3)
R (deg)
108.034(4)
91.282(5)
108.565(5)
1466.0(6)
â (deg)
101.477(2)
103.8080(10)
γ (deg)
V (Å3)
1517.9(3)
2
1.049
8700
4251 (R(int) ) 0.0246)
semiempirical
0.786 204
4251/2/387
1.043
2775.3(3)
4
1.139
16 315
5715 (R(int) ) 0.0208)
semiempirical
0.678 852
5715/0/357
1.039
Z
2
abs coef (mm-1
)
1.077
4579
no. of rflns collected
no. of indep rflns
abs cor
4580 (R(int) ) 0.0000)
semiempirical
0.567 423
4580/0/371
1.004
R1 ) 0.0584, wR2 ) 0.1118
R1 ) 0.0886, wR2 ) 0.1241
1.066, -1.025
min/max transmissn
no. of data/restraints/params
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
R1 ) 0.0283, wR2 ) 0.0700
R1 ) 0.0301, wR2 ) 0.0712
0.678, -0.342
R1 ) 0.0284, wR2 ) 0.0712
R1 ) 0.0338, wR2 ) 0.0738
0.609, -0.274
largest diff peak, hole (e Å-3
)
49.61 (CR2), 70.16 (CH2), 90.40 (GeOC), 119.73 and 120.02 (C4,5),
124.51, 125.53, 126.65, 126.86, 126.94, 127.11, 128.49, 129.16,
and 131.60 (C1-3, C6-8, m-CH of Mes and dCHCdO), 130.94,
132.71, 139.73, 140.02, 140.11, 140.24, 140.43, and 145.86 (ipso-,
o- and p-C of Mes, C10-13), 164.60 (dCHCOGe), 206.80 (Cd
O). MS (EI, 70 eV, m/z): 572 (M, 1), 329 (Mes2GeO + H, 18),
311 (Mes2Ge - H, 10), 244 (M - Mes2GeO, 45), 119 (Mes, 90),
96 (M - Mes2GedCR2, 100). Anal. Calcd for C36H34GeO2
(571.255): C, 75.69; H, 6.00. Found: C, 75.52; H, 5.81.
Synthesis of 7 (1 and 4-Cyclopentene-1,3-dione. 2:1 Molar
Ratio). The carbonyl compound was dissolved in toluene. Yield:
0.90 g (82%) of white crystals of bis(oxagermetane) 7 (mp 171
°C). 1H NMR (300.13 MHz): δ 0.92 and 1.33 (2 broad s, 2 × 6H,
o-Me of Mes), 1.97 (s, 2H, CH2), 2.11 (broad s, 12H, o- and p-Me
of Mes), 2.17 (s, 6H, p-Me of Mes), 2.27 (broad s, 6H, o-Me of
Mes), 6.20 (s, 2H, CHd), 6.40, 6.51, 6.64, and 6.75 (4 broad s, 4
× 2H, arom H of Mes), 6.96-7.06 (m, 5H, arom H of CR2), 7.20-
7.27 (m, 7H, arom H of CR2), 7.68-7.71 (m, 4H, arom H of CR2).
13C NMR (75.47 MHz): δ 20.96 and 20.98 (p-Me of Mes), 22.24,
22.36, and 23.32 (o-Me of Mes), 53.05 (CR2), 70.69 (CH2), 93.25
(CO), 118.96 and 119.16 (C4,5), 125.86, 125.91, 125.96, 126.01,
126.10, 127.78, 127.96, 128.87, 129.33, 129.78, and 130.28 (C1-
3, C6-8, m-CH of Mes), 136.81 (CHd), 131.95, 132.97, 139.32,
139.49, 140.01, 140.24, 142.15, 142.83, 143.64, 144.56, and 145.75
(ipso-, o- and p-C of Mes, C10-13). MS (DCI/NH3, m/z): 1064
(M + 18, 20), 1047 (M + 1, 50), 720 (M - Mes2GeO + H, 100).
Anal. Calcd for C67H64Ge2O2 (1046.424): C, 76.90; H, 6.16.
Found: C, 77.12; H, 6.20.
NMR (300.13 MHz): δ 1.53-1.58 (m, 2H, CH2), 1.94-1.98 (m,
2H, CH2), 2.10 (s, 12H, o-Me of Mes), 2.12 (s, 3H, dCMe), 2.22
(s, 6H, p-Me of Mes), 4.88 (s, 1H, CHR2), 6.75 (s, 4H, arom H of
3
Mes), 7.03 and 7.27 (2 t, JHH ) 7.8 Hz, 2 × 1H, H2,3,6,7 of
3
CR2), 7.16 and 7.73 (2 d, JHH ) 7.8 Hz, 2 × 1H, H1,4,5,8 of
CR2). 13C NMR (75.47 MHz): δ 21.04 (p-Me of Mes), 23.31 (o-
Me of Mes), 23.52 (dCMe), 29.30 and 33.96 (CH2CH2), 45.74
(CHR2), 119.78 (C4,5), 124.50, 126.09 and 126.58 (C1-3, C6-
8), 129.25 (m-C of Mes), 135.46, 139.28, 140.23, 141.23, 142.59,
142.89, and 143.79 (C10-13, ipso-, o-, and p-C of Mes and Cd
C), 205.97 (CO). Anal. Calcd for C37H38GeO2 (587.298): C, 75.67;
H, 6.52. Found: C, 75.82; H, 6.20.
Crystal Data for 3a, 5, and 8. Crystallographic data for all
structures are presented in Table 1. All data were collected at low
temperatures using an oil-coated shock-cooled crystal on a Bruker-
AXS CCD 1000 diffractometer with Mo KR radiation (λ ) 0.710 73
Å). The structures were solved by direct methods,14 and all non-
hydrogen atoms were refined anisotropically using the least-squares
method on F2.15
Acknowledgment. We thank the CMIFM (Grant No. AI
MA/05/123) and the CNRS for financial support.
Supporting Information Available: CIF files for 3a, 5, and
8. This material is available free of charge via the Internet at
http://pubs.acs.org.
OM060917S
Synthesis of 8 (1 and 2-Methyl-1,3-cyclopentanedione). The
carbonyl compound was dissolved in toluene. Yield: 0.97 g (78%)
of yellow crystals of germyloxycylopentenone 8 (mp 216 °C). H
(14) Sheldrick, G. M. SHELXS-97. Acta Crystallogr. 1990, A46, 467.
(15) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement; University of Go¨ttingen, Go¨ttingen, 1997.
1