Reactions of germenes with various naphthoquinones controlled by substituent effects

Article abstract of DOI:10.1039/b921729k

The germene Mes₂GeCR₂1 (Mes = 2,4,6-trimethylphenyl, CR₂ = fluorenylidene) reacts with 5-methoxy-1,4-naphthoquinone to yield, via the o-quinodimethane 8, the endoperoxyde 9 by simple reaction with molecular oxygen. By contrast, 1 with 2,3-dichloro-1,4-naphthoquinone gives the tetracyclic compound 7 by a double [2 + 4] cycloaddition between the GeC double bond and the conjugated system OC-CHCH. The new steric demanding germene Mes₂GeCR′₂5 (CR′₂ = 2,7-di-tert-butylfluorenylidene) undergoes similar [2 + 4] cycloadditions with various substituted or unsubstituted naphthoquinones, leading to tetracyclic adducts 10-12. The germene 5, the endoperoxide 9 and the cycloadducts 10 and 12 have been structurally characterized.

Full text of DOI:10.1039/b921729k

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Reactions of germenes with various naphthoquinones controlled
by substituent effects†
Dumitru Ghereg,a Heinz Gornitzka,*b Henri Ranaivonjatovoa and Jean Escudie´*a
Received 16th October 2009, Accepted 18th November 2009
First published as an Advance Article on the web 12th January 2010
DOI: 10.1039/b921729k
=
The germene Mes2Ge CR2 1 (Mes = 2,4,6-trimethylphenyl, CR2 = fluorenylidene) reacts with
5-methoxy-1,4-naphthoquinone to yield, via the o-quinodimethane 8, the endoperoxyde 9 by simple
reaction with molecular oxygen. By contrast, 1 with 2,3-dichloro-1,4-naphthoquinone gives the
=
tetracyclic compound 7 by a double [2 + 4] cycloaddition between the Ge C double bond and the
=
=
=
conjugated system O C–CH CH. The new steric demanding germene Mes2Ge CR¢2 5 (CR¢2 =
2,7-di-tert-butylfluorenylidene) undergoes similar [2 + 4] cycloadditions with various substituted or
unsubstituted naphthoquinones, leading to tetracyclic adducts 10–12. The germene 5, the endoperoxide
9 and the cycloadducts 10 and 12 have been structurally characterized.
Introduction
=
Over the past two decades, metallaalkenes >M C< (M = Si,
Ge, Sn) have received great attention and have been the subject
of a number of structural, theoretical and mechanistic studies
(for reviews, see ref.1a–1i (Si), and ref. 1j and k (Ge, Sn)).1 Such
unsaturated silicon, germanium and tin compounds present a very
high reactivity, much higher than their carbon analogues, and
constitute valuable building blocks for the synthesis of unusual
derivatives owing to addition and cycloaddition reactions onto
=
the >M C< double bond. Thus, they are extremely useful in
organometallicand heterocyclic chemistry. Although the reactivity
of such doubly-bonded derivatives towards various carbonyl com-
pounds such as saturated or a-ethylenic aldehydes and ketones,
esters, anhydrides, diketones is now well known,2 their chemical
Scheme 1 Reaction of germene 1 with naphthoquinone.
behavior towards quinones is still poorly documented. For o-
3
=
quinones only their reaction towards Ge C has been reported.
In the case of p-quinones we have recently described the reaction
of 1,4-naphthoquinone with the dimesityl(fluorenylidene)germane
=
Mes2Ge CR2 1 (Mes = 2,4,6-trimethylphenyl, CR2 = fluo-
Chart 1 Tetraenic and biradicalar structures for o-quinodimethane.
renylidene) leading to a mixture of the tetracyclic compound 2
and the o-quinodimethane type derivative 3 in a 50 : 50 ratio.4
Oxidation of the latter by air-oxygen, without any activation, led
to endoperoxide 4 a member of a family of derivatives which often
presents interesting biological activities4 (Scheme 1).
versial question about the real structure of o-quinodimethanes,
biradicalar (A) or tetraenic (B) (Chart 1).5
The X-ray structure of 3 showed a tetraenic structure and
allowed us to answer, at least in this special case, the contro-
In order to control the reaction pathway of the two different
cyclization reactions and to determine the factors influencing
the formation of the different products, we have studied various
possibilities: in a first approach we can change the substituents
around the naphthoquinone and the sterical hindrance of the
germene. For the last case, the difficult stabilization of such
compounds strongly restricted our outlook in this direction.
aUniversite´ de Toulouse, UPS, LHFA, 118 Route de Narbonne, F-31062
Toulouse, France; CNRS, LHFA, UMR 5069, F-31062 Toulouse cedex
09, France. E-mail: escudie@chimie.ups-tlse.fr; Fax: (+33)561558204;
Tel: (+33)561558347
bCNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de
Narbonne, F-31077 Toulouse Cedex 4, France, Universite´ de Toulouse,
UPS, INP, LCC, F-31077 Toulouse, France. E-mail: Heinz.Gornitzka@lcc-
toulouse.fr; Fax: (+33)561553003; Tel: (+33)561333161
=
Thus, we synthesized a new stable germene, Mes2Ge CR¢2 5,
substituted on the fluorenylidene group (CR¢2) by two bulky tert-
butyl groups, showing a slightly higher steric hindrance than 1.
The confrontation of the two germenes 1 and 5 towards diversely
substituted naphthoquinones is presented in this paper.
† CCDC reference numbers 751860–751863. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b921729k
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Results and discussion
Synthesis of the new germene 5
The new germene
5 was synthesized by dehydrofluori-
nation of bis(2,4,6-trimethylphenyl)-2,7-di-tert-butylfluorenyl-
(fluoro)germane 6 with tert-butyllithium in Et2O at low tempera-
ture (Scheme 2). Based on our experience with germene 1,6 fluorine
was chosen on the germanium atom instead of another halogen
in order to avoid reduction or alkylation reactions which could
occur with chlorine or bromine. Elimination of LiF was observed
around 0 ◦C. The germene 5 was crystallized from pentane as air
sensitive orange crystals and was characterized by X-ray structure
analysis (Fig. 1) and by H and 13C NMR data which display
equivalent Mes and t-Bu groups; the carbon atom doubly-bonded
to the germanium gives a signal at low field (133.63 ppm) in the
expected range for such a carbon atom.
1
Scheme
2,3-dichloronaphthoquinone.
3
Reaction of germene
1
with 5-methoxy- and
different; the presence of a methoxy group on the aromatic ring
directed the reaction towards the o-quinodimethane 8, probably
both for electronic and steric reasons. Due to its extreme air
sensitivity, only the endoperoxide 9 obtained by oxidation in
air was isolated in excellent yield and was characterized by X-
ray structure determination (Fig. 2). Whatever the experimental
conditions (temperature, solvent, number of equivalents of each
compound) these two derivatives 7 and 8 were obtained.
Scheme 2 Synthesis of germenes.
Fig. 2 Molecular structure of 9 (thermal ellipsoids at the 50% probability
level); H atoms and non-coordinated solvent molecules are omitted,
mesityl and fluo◦renyl groups are simplified for clarity; selected bond lengths
Fig. 1 Molecular structure of 5 (thermal ellipsoids at the 50% probability
level); H atoms and disorders of the t-Bu are omitted for clarity; selected
◦
˚
bond lengths (A) and angles ( ): Ge–C1 1.806(4), Ge–C12 1.932(3), C1–C2
˚
(A) and angles ( ): Ge1–O4 1.831(2), Ge1–C43 2.052(3), Ge2–O5 1.824(2),
1.465(4), C1–Ge–C12 120.3(1), C12–Ge–C12A 119.4(2), C2–C1–C2A
105.1(3).
Ge2–C12 2.055(3), O4–C1 1.373(4), O5–C8 1.362(4).
Thus, by substituting the aromatic or the quinonic ring,
regioselective reactions occur leading to the sole tetracyclic or
endoperoxide derivatives, respectively.
Reaction of germene 1 with 2,3-dichloro-1,4-naphthoquinone and
5-methoxy-1,4-naphthoquinone
In order to study the influence of the steric hindrance on the
course of the reactions, we replaced 1 by 5 and studied its chemical
behavior towards the same substituted naphthoquinones.
Addition of 0.5 equivalent of 1,3-dichloro-1,4-naphthoquinone to
germene 1 at low temperature led exclusively to the tetracyclic
derivative 7, by a double [2 + 4] cycloaddition involving the unsat-
=
=
urated C O bonds and C C bonds of the adjacent aromatic ring
(Scheme 3). Formation of an o-quinodimethane type compound
was disfavored in this case by the presence of chlorine atoms in
positions 2 and 3 on the former quinonic ring. By contrast, the
reaction of 1 with 5-methoxy-1,4-naphthoquinone was completely
Reaction of germene 5 with naphthoquinone, 2,3-dichloro-1,4-
naphthoquinone and 5-methoxy-1,4-naphthoquinone
Addition of these quinones to solutions of germene 5 in Et2O
(as the NMR data display that the germene is obtained nearly
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quantitatively, reactions were performed on crude solutions of
germene containing LiF) resulted in their rapid decoloration.
NMR analyses show the formation of a sole product in all cases
(Scheme 4), identified as the tetracyclic compounds 10, 11 and 12.
Cycloadducts 10 and 12 were also characterized by X-ray structure
determinations (Fig. 3 and 4). The unique formation of 11 from
2,3-dichloro-1,4-naphthoquinone, like in the case of germene 1,
was expected due to the presence of the two chlorine atoms on the
quinonic ring. In the reaction of 5 with 1,4-naphthoquinone, the
steric hindrance caused by the two tert-butyl groups disfavors the
formation of o-quinodimethane in which the two CR¢2 groups
should be on vicinal carbon atoms. A similar selective result7
=
was reported in the case of the stannene Tip2Sn CR¢2 (Tip =
2,4,6-triisopropylphenyl)8 which possesses the same 2,7-di-tert-
butylfluorenylidene group. More surprising is the similar selective
reaction between 5-methoxy-1,4-naphthoquinone and germene 5
leading to the tetracyclic derivative 12, in spite of the presence
of the methoxy group, while an o-quinodimethane derivative was
obtained starting from germene 1 and this quinone; thus, the steric
hindrance caused by the two tert-butyl groups appears as a very
important factor for the selectivity of the reactions.
Fig. 4 Molecular structure of 12 (thermal ellipsoids at the 50% probability
level); H atoms, a disorder of a t-Bu and non-coordinated solvent molecules
are omitted, mesityl and fluorenyl groups are simplified for clarity; selected
◦
˚
bond lengths (A) and angles ( ): Ge1–O1 1.828(4), Ge1–C12 2.010(7),
Ge2–O2 1.810(5), Ge2–C33 2.013(6), O1–C1 1.375(7), O2–C4 1.372(7).
their adducts due to the large steric hindrance. One of the main
characteristics is that the signals of the o-Me groups of the
Mes units are spread over a very large range, generally more than
2 ppm, due to their special position in relation to the fluorenyl
moieties: for example 0.64 to 2.88 ppm for 9, 0.52 to 2.73 ppm
for 11 and 0.46 to 2.68 ppm for 12. With symmetrical quinones
(naphthoquinone and dichloroquinone) the two Mes2Ge units are
equivalent, whereas the two Mes groups on each Ge atom are
non-equivalent, due to the presence of chiral carbons; by contrast,
in the case of the 5-methoxy-1,4-naphthoquinone, the 4 Mes
groups in endoperoxide 9 and in derivative 12 are non-equivalent.
Whereas all peaks of the o-Me groups can be observed in the
adducts from germene 1 (even if in some cases they give broad
signals), some of them completely disappear in the baseline of the
1H NMR spectra of 10 and 12, obtained from bulkier germene
5 because of a slow rotation and a coalescence phenomenon. A
surprising feature is also the high-field shift of m-CH of Mes, up
to 6.27 ppm (12), and of H1 and H8 up to 6.28 ppm (11), due
to the mutual position of these aromatic groups; the shielding is
even much more important (5.07 ppm) in the case of 9 due to the
additional presence of the endoperoxide bridge. It is also worthy
to note that no coupling is observed for the 4 protons of the R2C–
Scheme 4 Reactions of germene 5 with various naphthoquinones.
=
CH–CH CH–CH–CR2 unit in 7 and 10–12 which give only 2
singlets at very close chemical shifts: for example 4.10/4.13 and
4.30/4.47 ppm for 7 and 11, respectively and 4.25 and 4.38 ppm
(10).
In mass spectrometry, the molecular peak was observed, and
the germene was one of the fragments.
Fig. 3 Molecular structure of 10 (thermal ellipsoids at the 50% probability
level); H atoms, a disorder of a t-Bu and non-coordinated solvent molecules
are omitted, mesityl and fluorenyl groups are simplified for clarity; selected
◦
˚
bond lengths (A) and angles ( ): Ge1–O1 1.799(4), Ge1–C11 2.023(5),
Ge2–O2 1.825(4), Ge2–C32 2.003(5), O1–C1 1.370(6), O2–C4 1.384(6).
X-Ray crystallographic analyses
Molecular structures for compounds 5, 9, 10 and 12 are shown
=
in Fig. 1–4, respectively. Germene 5 displays a short Ge C
1H and 13C spectroscopic studies
˚
double bond (1.806(4) A), about the same as in the dime-
6b
˚
Whereas a free rotation was observed for the Mes groups in
sityl(fluorenylidene)germane 1 (1.803(3) A), and among the
the starting germenes 1 and 5, a hindered rotation occurs in
shortest Ge–C distance. The shortening is about 7% compared to
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9
˚
Aldrich and were used without further purification. Deuterated
=
the Ge–C(Mes) single bonds (1.932(3) A). The only shorter Ge C
˚
bond length was reported in germene 13 (1.771(16) A),10 whereas it
˚
solvents were dried and stored over 4 A molecular sieves. NMR
is generally from 1.82 to 1.84 A in germenes 1411 or bis(germenes)
˚
spectra were recorded in CDCl3 (when other solvent is not
mentioned) on Bruker Avance 300 and 400 instruments at the
following frequencies: 300.13 or 400.13 MHz for 1H, 282.38 MHz
15.12 It is even longer in germenes 1613 (1.850(4) to 1.859(1) A due
˚
to a delocalization of p-electrons resulting from the conjugation
of P N and Ge C bonds and to an intramolecular complexation
of the germanium by a nitrogen atom) and in the cyclic germene
17 (1.859 A). The long Ge C distance (2.085(3) A) in derivative
18 was explained by a structure of type 18b15 (Scheme 5).
1
for 19F (ref. CFCl3) and 75.47 or 100.62 MHz for 13C{ H}. 1H and
=
=
1
13C{ H} NMR assignments were confirmed by 1H COSY, HSQC
14
˚
˚
(1H-13C) and HMBC (1H-13C) experiments. Mass spectra were
measured on a Nermag R10-10 spectrometer by CI (NH3 or CH4).
Melting points were determined on a Leitz microscope heating
stage 250 or Electrothermal apparatus (capillary). Elemental
analyses were performed by the “Service de Microanalyse de
l’Ecole de Chimie de Toulouse”. The yields were calculated from
the starting Mes2Ge(F)–CHR2.
=
All data for structures were collected at low temperature using
an oil-coated shock-cooled crystal on a Bruker-AXS Apex II
˚
diffractometer with Mo Ka radiation (l = 0.7107 A) and are
summarized in Table 1. The structures were solved by direct
methods16 and all non-hydrogen atoms were refined anisotropi-
cally using the least-squares method on F2.17 CCCD-751860 (5),
CCCD-751861 (9), CCCD-751862 (10) and CCDC-751863 (12)
contain the supplementary crystallographic data for this paper.†
Starting compounds were synthesized according to the litera-
ture: Mes2GeF2,18 2,7-di-tert-butylfluorene,19 and 5-methoxy-1,4-
naphthoquinone.20
For the 1H and 13C NMR study, the carbon atoms of the
fluorenyl and 2,7-di-tert-butylfluorenyl groups are numbered as
shown below (Chart 2).
=
Scheme 5 Ge C bond lengths in germenes.
Conclusion
In conclusion, the course of the reaction is extremely dependent
on the size of the fluorenylidene moiety doubly-bonded to the
germanium atom in the starting germene, and, to a less extent,
of the substitution pattern of the quinone. With the bulky
2,7-di-tert-butylfluorenylidenegermane, the formation of the o-
quinodimethane was not possible for steric reasons and only prod-
ucts involving [2 + 4] cycloadditions on the aromatic ring of the
quinone were observed. In the case of the fluorenylidenegermane,
the presence of two chlorine atoms on the quinonic ring disfavored
the formation of the o-quinodimethane and led also to the double
[2 + 4] cycloadduct with the aromatic ring. By contrast, a methoxy
group on the aromatic ring led to the unique formation of an
extremely reactive o-quinodimethane, which gave after simple
oxidation by triplet oxygen the corresponding endoperoxide. The
studies concerning other factors, such as the nature of the metal,
the role of the oxygen atom, which could be replaced by other
isoelectronic hetero atoms such as sulfur or selenium, as well as
the use of heteroquinones are under strong investigation.
Chart 2 Numbering scheme for fluorenyl groups.
=
Synthesis of germene Mes2Ge CR2 1
6
=
Germene Mes2Ge CR2 was prepared as previously described by
dropwise addition of 1.05 molar equivalents of tert-butyllithium
(1.7 M in pentane) to a solution of 1.00 mmol of the starting
fluorogermane Mes2Ge(F)–CHR2 in 10 mL of diethyl ether cooled
to -78 ◦C. Warming to room temperature afforded an orange
=
solution of Mes2Ge CR2 with a precipitate of LiF. According to
1
=
a H NMR experiment, germene Mes2Ge CR2 was formed in
nearly quantitative yield. Thus, all reactions were performed on
the crude reaction mixture containing LiF.
Bis(2,4,6-trimethylphenyl)-2,7-di-tert-butylfluorenyl(fluoro)-
germane Mes2Ge(F)-CHR¢2 6
Experimental
To a solution of 2,7-di-tert-butylfluorene (1.39 g, 5.0 mmol) in
THF (15 mL) cooled to -78 ◦C was added a solution of n-
BuLi (1.6 M in hexane, 3.2 mL, 5.1 mmol). The solution turned
immediately red and was allowed to warm to room temperature.
After stirring for 30 min, this solution was slowly added to a
suspension of Mes2GeF2 (1.74 g, 5.0 mmol) in THF (10 mL)
General experimental details
All experiments were performed in oven-dried glassware under
argon atmosphere using standard vacuum-line, Schlenk and can-
nula techniques, with solvents being distilled over standard drying
agents and degassed before use. All reagents were purchased from
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Table 1 Crystal data for 5, 9, 10 and 12
5
9·0.5C5H12
10·CH2Cl2
12·C5H12
Empirical formula
Formula weight
T/K
C39H46Ge
587.35
173(2)
Monoclinic
C2/c
15.315(2)
20.473(3)
11.685(2)
—
113.839(2)
—
3351.2(8)
4
1.164
C75.5H74Ge2O5
1206.53
173(2)
Triclinic
¯
P1
11.5384(3)
14.2970(4)
20.0687(5)
74.574(2)
81.440(2)
72.261(2)
2984.0(2)
2
C89H100Cl2Ge2O2
1417.77
173(2)
Monoclinic
P21/n
17.304(2)
25.114(2)
19.401(2)
—
112.691(2)
—
7778.8(13)
4
1.211
C94H112Ge2O3
1435.02
173(2)
Triclinic
¯
P1
12.547(1)
17.429(1)
19.423(2)
95.521(2)
93.110(3)
108.741(3)
3987.3(3)
2
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
V/A
Z
rc/Mg m-3
1.343
1.061
1262
1.195
0.803
1528
m/mm-1
0.938
1248
0.888
2992
F(000)
Crystal size/mm
q Range for data collection/◦
Reflections collected
Independent reflections
R(int)
0.6*0.1*0.1
5.19–25.35
8738
3053
0.0560
1.0000/0.3794
3053/36/213
0.998
0.0436
0.0872
0.5*0.2*0.1
5.10–25.35
26 341
10 826
0.0618
0.9013/0.6189
10 826/38/779
0.964
0.0442
0.0933
0.1*0.1*0.05
5.11–25.35
56 978
14 120
0.2136
0.1*0.05*0.05
5.11–25.03
33 775
13 802
0.2098
Max./min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
R1 (I > 2s(I))
—
—
14 120/172/959
0.980
0.0764
0.1507
0.1811
0.1909
0.604/-0.410
13 802/86/943
0.703
0.0680
0.0859
0.2580
0.1266
0.521/-0.583
wR2 (I > 2s(I))
R1 (all data)
0.0749
0.0971
0.401/-0.238
0.0898
0.1084
0.630/-0.502
wR2 (all data)
-3
˚
Drmax/min/e A
cooled to -78 ◦C. The brown-red reaction mixture was slowly
warmed to room temperature and then turned orange. After
additional 2 h of stirring, removal of solvents under reduced
pressure, 50 mL of pentane were added and the lithium salts
were removed by filtration. White crystals of fluorogermane 6
the reaction mixture was allowed to warm to room temperature
and stirred for 30 min; it became orange. 1H and 19F-NMR
analyses showed the total consumption of the starting 6 and nearly
=
quantitative formation of Mes2Ge CR¢2. The reaction mixture
was concentrated to 10 mL and crystallized in a sealed tube giving
orange crystals of germene 5 (0.49 g, 83%, mp 178 ◦C). 1H NMR
(C6D6, 300.13 MHz): 1.15 (s, 18H, CMe3), 2.03 (s, 6H, p-Me of
Mes), 2.35 (s, 12H, o-Me of Mes), 6.70 (s, 4H, m-CH of Mes),
were obtained from pentane at -20 ◦C (2.28 g, 75%). mp 183 ◦C.
5
1H NMR (300.13 MHz): 1.16 (s, 18H, CMe3), 2.01 (d, JHF
=
1.8 Hz, 12H, o-Me of Mes), 2.24 (s, 6H, p-Me of Mes), 4.68 (d,
3JHF = 5.1 Hz, 1H, CHR¢2), 6.77 (s, 4H, m-CH of Mes), 7.28
7.24 (dd, JHH = 7.8 Hz, JHH = 1.8 Hz, 2H, H3 and H6), 7.61
(d, 4JHH = 1.8 Hz, 2H, H1 and H8), 7.80 (d, 3JHH = 7.8 Hz, 2H,
H4 and H5). 13C NMR (75.47 MHz): 21.16 (p-Me of Mes), 24.15
(o-Me of Mes), 31.69 (CMe3), 34.90 (CMe3), 118.37, 119.38 and
121.73 (C1, C3, C4, C5, C6 and C8), 129.06 (m-CH of Mes), 133.63
3
4
4
3
(d, JHH = 1.5 Hz, 2H, H1 and H8), 7.36 (dd, JHH = 7.8 Hz,
4JHH = 1.5 Hz, 2H, H3 and H6), 7.67 (d, 3JHH = 7.8 Hz, 2H, H4
and H5). 13C NMR (75.47 MHz): 20.97 (p-Me of Mes), 22.92 (d,
4JCF = 4.1 Hz, o-Me of Mes), 31.29 (CMe3), 34.65 (CMe3), 46.24
(d, 2JCF = 13.0 Hz, CHR¢2), 118.96 (C4 and C5), 121.34 (d, 4JCF
=
(C Ge), 136.84 (ipso-C of Mes), 140.79 (p-C of Mes), 143.25 (o-
=
0.9 Hz, C1 and C8), 123.41 (C3 and C6), 129.04 (m-CH of Mes),
133.62 (d, 2JCF = 10.1 Hz, ipso-C of Mes), 138.79 (d, 4JCF = 0.8 Hz,
C12 and C13), 139.72 (p-C of Mes), 142.86 (d, 3JCF = 2.3 Hz, o-C
of Mes), 143.03 (C10 and C11), 149.44 (C2 and C7). 19F NMR
(282.38 MHz): -173.89. MS m/z (% relative intensity): 608 (M, 8),
C of Mes), 143.29 and 143.79 (C10,11 and C12,13), 148.21 (C2
=
and C7). MS m/z (% relative intensity): 588 (Mes2Ge CR¢2, 10),
311 (Mes2Ge - 1, 100), 276 (R¢2C, 15), 191 (MesGe - 2, 25), 119
(Mes, 10). Anal. Calcd for C39H46Ge (587.421) C, 79.74; H, 7.89%.
Found: C, 79.54; H, 7.55%.
=
589 (Mes2Ge CR2 + 1, 4), 331 (Mes2GeF, 100), 311 (Mes2Ge -
1, 10), 277 (R2CH, 17), 191 (MesGe - 2, 12), 119 (Mes, 8). Anal.
Calcd for C39H47GeF (607.427) C, 77.11; H, 7.80%. Found: C,
77.19; H, 7.52%.
=
Reaction of Mes2Ge CR2 with 2,3-dichloro-1,4-naphthoquinone
A solution of 2,3-dichloro-1,4-naphthoquinone (0.5 mmol)
in THF (20 mL) was cannulated to the crude solution of
◦
=
Mes2Ge CR2 (1.0 mmol) cooled to -78 C. The initially orange
=
Synthesis of germene Mes2Ge CR¢2 5
reaction mixture turned green and then yellow on warming to
room temperature. After removal of LiF by filtration, diethyl ether
was evaporated under vacuum and replaced by pentane (10 mL).
The crystallization at -20 ◦C afforded white crystals of 7 (0.46 g,
78%). 1H NMR (300.13 MHz): 0.57 and 2.59 (2 s, 2 ¥ 6H, o-Me of
To a solution of fluorogermane Mes2Ge(F)–CHR¢2 (0.607 g,
1.0 mmol) in diethyl ether (40 mL) cooled to -78 C was added
dropwise by syringe a solution of t-BuLi (1.7 in pentane, 0.6 mL,
1.0 mmol). The solution turned immediately yellow. After 15 min
◦
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1
Mes), 1.19 and 2.54 (2brs, 2 ¥ 6H, o-Me of Mes), 2.04 and 2.19 (2 s,
2 ¥ 6H, p-Me of Mes), 4.10 and 4.13 (2 s, 2 ¥ 2H, CH-CHCR2),
6.29 and 6.67 (2 s, 2 ¥ 2H, m-CH of Mes), 6.48 and 6.88 (2brs, 2 ¥
2H, m-CH of Mes), 6.31 and 6.41 (2d, 3JHH = 7.5 Hz, 2 ¥ 2H, H1
and H8), 6.77 and 6.92 (2t, 3JHH = 7.5 Hz, 2 ¥ 2H, H2 and H7), 7.11
were obtained (0.49 g, 74%). H NMR (300.13 MHz): 0.46 and
2.57 (2 s, 2 ¥ 6H, o-Me of Mes) (due to a coalescence phenomenon,
only 2 Mes can be observed in NMR) 0.94 and 1.02 (2 s, 2 ¥ 18H,
CMe3), 2.10 and 2.20 (2 s, 2 ¥ 6H, p-Me of Mes), 4.25 (s, 2H,
CHCR¢2), 4.38 (s, 2H, CH-CHCR¢2), 6.29 and 6.67 (2d, JHH
4
=
and 7.21 (2t, 3JHH = 7.5 Hz, 2 ¥ 2H, H3 and H6), 7.58 (d, 3JHH
=
1.5 Hz, 2 ¥ 2H, H1 and H8), 6.30 and 6.72 (2 s, 2 ¥ 2H, m-CH
7.5 Hz, 4H, H4 and H5). 13C NMR (75.47 MHz): 20.85 and 21.06
(p-Me of Mes), 22.70, 22.86 and 22.98 (br, o-Me of Mes), 39.88
(CHCR2), 55.10 (CR2), 119.30 and 119.54 (C4 and C5), 123.03,
123.27 (C–CO and C(Cl)–CO), 123.53, 124.75, 125.47, 126.45,
126.61, 126.73, 127.00, 127.67, 128.86, 129.64 and 130.95 (C1, C2,
C3, C6, C7, C8, m-CH of Mes and CH-CHCR2), 132.99, 135.21
(ipso-C of Mes), 139.11 and 139.67 (p-C of Mes), 141.11, 141.59,
142.00, 143.95, 144.17, 144.25, 144.78, 145.40 and 146.65 (o-C of
Mes, C10–C13, C–O). MS m/z (% relative intensity): 1196 (M +
of Mes), 6.91 (s, 2H, OCCHCHCO), 7.24 and 7.29 (2dd, 3JHH
=
4
7.8 Hz, JHH = 1.8 Hz, 2 ¥ 2H, H3 and H6), 7.64 and 7.67 (2d,
3JHH = 7.8 Hz, 2 ¥ 2H, H4 and H5). 13C NMR (75.47 MHz): 20.71
and 20.79 (p-Me of Mes), 22.65 and 23.63 (o-Me of Mes), 30.88
and 31.32 (CMe3), 34.46 and 34.57 (CMe3), 39.79 (CHCR2), 56.50
(CR2), 118.34 and 118.50 (C4 and C5), 118.77 (OCCHCHCO),
120.93 and 123.36 (C1 and C8), 123.53 and 124.09 (C3 and C6),
124.12 (CH–CHCR2), 124.75 (C–CO), 127.49 and 129.33 (m-CH
of Mes), 133.64 and 135.35 (ipso-C of Mes), 138.17 and 138.19,
139.04 and 139.41 (p-C of Mes, C12 and C13), 142.40 and 143.89
(o-C of Mes), 144.31 and 145.89 (C10 and C11), 149.17, 149.21
and 150.30 (C2, C7 and C–O). MS m/z (% relative intensity):
+
NH4 , 100), 1179 (M + 1, 5), 1059 (M–Mes, 5). Anal. Calcd for
C72H64Cl2Ge2O2 (1177.38) C, 73.45; H, 5.48%. Found: C, 73.24;
H, 5.35%.
=
1333 (M, 15), 1056 (M–CR¢2 - 1, 20), 588 (Mes2Ge CR¢2, 30),
311 (Mes2Ge - 1, 100), 277 (R¢2CH, 15), 119 (Mes, 15). Anal.
Calcd for C88H98Ge2O2 (1332.995) C, 79.29; H, 7.41%. Found: C,
79.34; H, 7.50%.
=
Reaction of Mes2Ge CR2 with 5-methoxy-1,4-naphthoquinone
To the crude solution of 1 cooled to -78 ◦C was slowly added
via cannula 0.5 equivalent of the 5-methoxy-1,4-naphthoquinone
dissolved in 20 mL of THF. The reaction mixture progressively
turned to red by warming to room temperature. Its air exposure
followed by crystallization from pentane led to white crystals of
product 9 (0.44 g, 75%). 1H NMR (300.13 MHz): 0.64, 0.74, 1.46,
1.75, 1.76, 2.53, 2.56 and 2.88 (8 s, 8 ¥ 3H, o-Me of Mes), 2.10,
2.12, 2.18 and 2.19 (4 s, 4 ¥ 3H, p-Me of Mes), 3.19 and 4.05
=
Reaction of Mes2Ge CR¢2 with 2,3-dichloro-1,4-naphthoquinone
The reaction was carried out following the same procedure as in
the case of Mes2Ge CR2 to afford 11 (0.48 g, 67%). H NMR
(300.13 MHz): 0.52 and 2.73 (2 s, 2 ¥ 6H, o-Me of Mes), 1.28 and
2.71 (2brs, 2 ¥ 6H, o-Me of Mes), 1.02 and 1.08 (2 s, 2 ¥ 18H,
CMe3), 2.14 and 2.27 (2 s, 2 ¥ 6H, p-Me of Mes), 4.30 (s, 2H,
CHCR2) and 4.47 (s, 2H, CH CH), 6.28 and 6.72 (2d, JHH
1.2 Hz, 2 ¥ 2H, H1 and H8), 6.65 and 6.78 (2 s, 2 ¥ 2H, m-
CH of Mes), 6.61 and 6.95 (2brs, 2 ¥ 2H, m-CH of Mes), 7.32
1
=
3
(2d, JHH = 7.8 Hz, 2 ¥ 1H CHCH), 3.92 (s, 3H, OMe), 5.07,
4
5.19, 6.19, 6.75, 6.89, 6.94, 7.08 and 8.73 (8d, 3JHH = 7.5 Hz, 8 ¥
=
=
1H, H1, H4, H5 and H8), 6.15, 6.17, 6.70, 6.88, 7.18 (5t, 3JHH
=
7.5 Hz, 5 ¥ 1H, 5H among H2, H3, H6 and H7), 6.22 (s, 2H,
m-CH of Mes), 6.43 (s, 4H, m-CH of Mes), 6.80 and 6.85 (2 s,
2 ¥ 1H, m-CH of Mes), 7.27-7.45 (m, 6H, CHCHCHCOMe and
3H among H2, H3, H6 and H7). 13C NMR (75.47 MHz): 20.71,
20.83 and 20.88 (p-Me of Mes), 22.27, 22.35 (broad signal), 22.40,
22.87, 23.03 (broad signal), 23.52 and 24.37 (o-Me of Mes), 53.43
and 57.73 (CHCH), 55.49 (OMe), 57.71 and 59.38 (CR2), 106.79
and 107.76 (OCO), 112.41, 114.59, 118.33, 118.78, 120.09, 120.47,
122.54, 122.90, 124.70, 124.74, 125.01, 125.45, 125.73, 125.92,
126.18, 126.32, 127.02, 127.70, 128.11, 128.28, 129.03, 129.42,
129.72, 130.07 (C1-C8, m-CH of Mes and CHCHCHCOMe),
125.06, 133.21, 134.88, 135.21, 135.98, 137.76138.46, 138.48,
138.56, 138.99, 139.06, 141.70, 141.85, 142.60, 143.12, 144.06,
144.13, 144.63, 144.71 (C10–C13, ipso-C, o-C and p-C of Mes
and CCCOMe), 154.32 (COMe). MS m/z (% relative intensity):
3
4
and 7.37 (2dd, JHH = 7.8 Hz, JHH = 1.2 Hz, 2 ¥ 2H, H3 and
3
H6), 7.62 and 7.64 (2d, JHH = 7.8 Hz, 2 ¥ 2H, H4 and H5).
13C NMR (75.47 MHz): 20.77 and 20.82 (p-Me of Mes), 22.41
and 22.75 (o-Me of Mes), 22.25 and 25.06 (brs, o-Me of Mes),
30.90 and 31.09 (CMe3), 34.50 (CMe3), 39.71 (CHCR¢2), 55.73
(CR’2), 118.60 and 118.97 (C4 and C5), 120.93 and 123.15 (C1
and C8), 122.68 (C–Cl), 124.01 (C–CO), 123.67 and 124.35 (C3
=
and C6), 123.67 (CH CH), 127.17 and 129.45 (m-CH of Mes),
129.70 and 130.60 (br, m-CH of Mes), 133.02 and 135.05 (ipso-
C of Mes), 138.28, 138.61, 139.33 and 139.41 (p-C of Mes, C12
and C13), 141.84 and 144.78 (o-C of Mes), 143.16 and 144.17 (br,
o-C of Mes), 143.80 and 144.98 (C10 and C11), 147.07 (C–O),
149.37 and 149.50 (C2 and C7). Anal. Calcd for C88H96Cl2Ge2O2
(1401.81) C, 75.40; H, 6.90%. Found: C, 75.34; H, 6.52%.
+
1188 (M + NH4 , 55), 1170 (M, 35), 1155 (M - Me, 15), 1138
(M–O2, 100), 1051 (M - Mes, 20). Anal. Calcd for C73H68Ge2O5
(1170.51) C, 74.91; H, 5.86%. Found: C, 75.01; H, 6.02%.
=
Reaction of Mes2Ge CR¢2 with 5-methoxy-1,4-naphthoquinone
=
To a crude solution of Mes2Ge CR¢2 (1.0 mmol) in Et2O
(40 mL) cooled to -78 ◦C was added 0.5 mmol of 5-methoxy-
1,4-naphthoquinone dissolved in 20 mL of THF. The reaction
mixture was allowed to warm to room temperature and its color
slowly turned from orange to brown. After overnight stirring and
elimination of LiF by filtration, solvent was removed in vacuo
and replaced by 10 mL of pentane. Crystallization at -20 ◦C
afforded a pure crystalline white compound identified to 12 (0.53 g,
=
Reaction of Mes2Ge CR¢2 with 1,4-naphthoquinone
=
To a solution of germene Mes2Ge CR¢2 (1.0 mmol) in Et2O
(40 mL) cooled to -78 ◦C was slowly added 0.5 mmol of 1,4-
naphthoquinone dissolved in 10 mL of diethyl ether. The reaction
mixture became green and progressively turned brown-red after
2 h of stirring at room temperature. After filtration to eliminate
lithium salts and crystallization from pentane, white crystals of 10
1
77%). H NMR (300.13 MHz): 0.46, 0.47, 2.63 and 2.68 (due
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to a coalescence phenomenon, only 2 Mes can be observed in
NMR) o-Me of Mes), 0.97, 0.98, 1.02 and 1.03 (4 s, 4 ¥ 9H,
CMe3), 1.82 (OMe), 2.10, 2.13, 2.22 and 2.25 (4 s, 4 ¥ 3H, p-Me
1; (g) A. G. Brook and M. A. Brook, Adv. Organomet. Chem., 1996,
39, 71; (h) T. Mu¨ller, W. Ziche and N. Auner, in The Chemistry of
Organic Silicon Compounds, vol 2, ed. Z. Rappoport and Y. Apeloig,
Wiley, Chichester, 1998, ch. 16, p 857); (i) J. Barrau, J. Escudie´ and J.
Satge, Chem. Rev., 1990, 90, 283; (j) K. Baines and W. G. Stibbs, Adv.
Organomet. Chem., 1996, 39, 275; (k) J. Escudie´ and H. Ranaivonjatovo,
Adv. Organomet. Chem., 1999, 44, 113.
2 (a) N. Wiberg and Ch. K. Kim, Chem. Ber., 1986, 119, 2980; (b) M.
Lazraq, C. Couret, J. Escudie´, J. Satge´ and M. Dra¨ger, Organometallics,
1991, 10, 1771; (c) M. Lazraq, J. Escudie´, C. Couret, J. Satge´ and M.
Soufiaoui, Organometallics, 1992, 11, 555; (d) G. Delpon-Lacaze, C.
Couret, J. Escudie´ and J. Satge´, Main Group Met. Chem., 1993, 16, 419;
(e) N. J. Mosey, K. M. Baines and T. K. Woo, J. Am. Chem. Soc., 2002,
124, 13306.
3 F. Meiners, D. Haase, R. Koch, W. Saak and M. Weidenbruch,
Organometallics, 2002, 21, 3990.
4 D. Ghereg, S. Ech-Cherif El Kettani, M. Lazraq, H. Ranaivonjatovo,
W. W. Schoeller, J. Escudie´ and H. Gornitzka, Chem. Commun., 2009,
4821.
5 C. R. Flynn and J. Michl, J. Am. Chem. Soc., 1974, 96, 3280.
6 (a) C. Couret, J. Escudie´, J. Satge´ and M. Lazraq, J. Am. Chem. Soc.,
1987, 109, 4411; (b) M. Lazraq, J. Escudie´, C. Couret, J. Satge´, M.
Dra¨ger and M. Dammel, Angew. Chem., Int. Ed. Engl., 1988, 27, 828.
7 D. Ghereg, H. Ranaivonjatovo, N. Saffon, H. Gornitzka and J. Escudie´,
Organometallics, 2009, 28, 2294.
3
4
of Mes), 4.07 (dd, JHH = 3.2 Hz, JHH = 2.0 Hz, 1H, CHCR¢2),
´
4.11 (dd, 3JHH = 10.8 Hz, 4JHH = 2.0 Hz, 1H, CHC(OMe)CR¢2),
3
3
4.65 (dd, JHH = 10.8 Hz, JHH = 3.2 Hz, 1H, CHCHCR¢2),
6.27, 6.33, 6.74 and 6.78 (4 s, 4 ¥ 1H, m-CH of Mes), 6.32,
4
6.47 and 7.45 (3d, 3 ¥ 1H, JHH = 1.5 Hz, H1 and H8), 6.97
3
and 7.00 (2d, JHH = 12.4 Hz, 2 ¥ 1H, OCCHCHCO), 7.17 (dd,
3JHH = 8.0 Hz, 4JHH = 1.6 Hz, 1H, H3 or H6), 7.27-7.32 (m, 4H,
3
H3, H6 and H1 or H8), 7.46, 7.53, 7.56 and 7.58 (4d, JHH
=
8.0 Hz, 4 ¥ 1H, H4 and H5). 13C NMR (75.47 MHz): 20.63,
20.76, 20.79 and 20.87 (p-Me of Mes), 22.75, 23.10, 23.68 and
23.91 (o-Me of Mes), 31.01, 31.05, 31.20 and 31.24 (CMe3), 34.48,
34.52, 34.62 and 34.77 (CMe3), 39.76 (CHCR¢2), 50.33 (OMe),
54.52 and 61.81 (CR¢2), 78.89 (COMe), 118.18, 118.27, 118.64 and
119.09 (C4 and C5), 119.85 and 119.87 (OCCHCHCO), 121.00,
123.97, 124.62 and 125.02 (C1 and C8), 122.77 and 125.59 (arom
=
C C), 123.41, 123.55, 124.12 and 124.19 (C3 and C6), 125.35
(CHC(OMe)CR¢2), 127.49, 127.58, 129.25 and 129.28 (m-CH of
Mes), 128.94 (CHCCHCR¢2), 133.03, 134.86, 135.80 and 135.87
(ipso-C of Mes), 137.47, 137.87, 138.32, 138.33, 138.91, 139.26,
139.34, 140.11 (p-C of Mes, C12 and C13), 142.29, 142.31, 144.29
and 144.62 (o-C of Mes), 144.72, 144.77, 144.81 and 145.06 (C10
and C11), 148.81, 149.02, 149.23, 149.50, 149.57, 151.48 (C2,
C7 and C–O). MS m/z (% relative intensity): 1363 (M, 25), 1331
8 Abdoul Fatah, R. El Ayoubi, H. Gornitzka, H. Ranaivonjatovo and
J. Escudie´, Eur. J. Inorg. Chem., 2008, 2007.
9 For reviews on Ge–X bond lengths, see: (a) K. M. Baines and W. G.
Stibbs, Coord. Chem. Rev., 1995, 145, 157; (b) C. E. Holloway and M.
Melnik, Main Group Met. Chem., 2002, 25, 185.
10 N. Tokitoh, K. Kishikawa and R. Okazaki, J. Chem. Soc., Chem.
Commun., 1995, 1425.
11 H. Meyer, G. Baum, W. Massa and A. Berndt, Angew. Chem., Int. Ed.
Engl., 1987, 26, 798.
=
(M–MeOH, 45), 588 (Mes2Ge CR¢2, 50), 343 (Mes2Ge(OMe),
12 (a) F. Meiners, W. Saak and M. Weidenbruch, Organometallics, 2000,
19, 2835; (b) B. Pampuch, W. Saak and M. Weidenbruch, J. Organomet.
Chem., 2006, 691, 3540.
65), 311 (Mes2Ge - 1, 100). Anal. Calcd for C89H100Ge2O3
(1362.95) C, 78.43; H, 7.40%. Found: C, 78.24; H, 7.50%.
13 W.-P. Leung, K.-W. Kan, C.-W. So and T. C. W. Mak, Organometallics,
2007, 26, 3802.
Acknowledgements
14 V. Ya Lee, M. Ichinohe and A. Sekiguchi, J. Am. Chem. Soc., 2002, 124,
9962.
The CNRS (contract CNRS/JSPS no. PRC 450), ECOS CONI-
CYT (contract C08E01) and the ANR (contract ANR-08-BLAN-
0105-01) for financial support.
15 H. Schumann, M. Glanz, F. Girgsdies, F. Ekkehardt Hahn, M. Tamm
and A. Grzegorzewski, Angew. Chem., Int. Ed. Engl., 1997, 36, 2232.
16 G. M. Sheldrick, SHELXS-97, Acta Crystallogr, 1990, A46, 467.
17 G. M. Sheldrick, SHELXL-97, Program for Crystal Structure Refine-
ment, University of Go¨ttingen, 1997.
18 P. Rivie`re, M. Rivie`re-Baudet, A. Castel, D. Desor and C. Abdennad-
her, Phosphorus, Sulfur Silicon Relat. Elem., 1991, 61, 189.
19 (a) A. F. Kaplan and B. W. Roberts, J. Am. Chem. Soc., 1977, 99, 518;
(b) A. L. Carpino, H. G. Chao and J. H. Tie, J. Org. Chem., 1989, 54,
4302.
20 L. F. Tietze, C. Gu¨ntner, K. M. Gericke, I. Schuberth and G. Bunkoczi,
Eur. J. Org. Chem., 2005, 2459.
Notes and references
1 For reviews, see: (a) P. P. Power, Chem. Rev., 1999, 99, 3463; (b) R.
Okazaki and R. West, Adv. Organomet. Chem., 1996, 39, 231; (c) R.
West, Polyhedron, 2002, 21, 467; (d) A. Sekiguchi and V. Ya Lee, Chem.
Rev., 2003, 103, 1429; (e) N. Tokitoh, Acc. Chem. Res., 2004, 37, 86;
(f) A. G. Brook and K. M. Baines, Adv. Organomet. Chem., 1986, 25,
2022 | Dalton Trans., 2010, 39, 2016–2022
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The Royal Society of Chemistry 2010
©