Addition of methyl grignard reagents to germasilenes and digermenes: Unusual ligand exchange reaction of the resulting germyl grignard reagents

Article abstract of DOI:10.1021/ja981787k

Methylmagnesium iodide (or bromide) has been found to add to tetramesitylgermasilene and tetramesityldigermene. The addition to the germasilene is regioselective, with the methyl group adding to the silicon end of the silicon-germanium double bond to produce a germylmagnesium iodide (or bromide) species. The germyl Grignard reagents give the corresponding germanes upon hydrolysis. At 110 °C in the presence of excess methylmagnesium halide, the mesityl substituents on the germyl Grignard reagent germanium atom were exchanged for methyl groups. A mechanism involving the α-elimination of MesMgX followed by the addition of MeMgX to the intermediate germylene has been proposed to explain the observed ligand exchange. Evidence for the presence of intermediate germylenes has been obtained in trapping experiments with 2,3-dimethylbutadiene.

Full text of DOI:10.1021/ja981787k

J. Am. Chem. Soc. 1998, 120, 10365-10371
10365
Addition of Methyl Grignard Reagents to Germasilenes and
Digermenes: Unusual Ligand Exchange Reaction of the Resulting
Germyl Grignard Reagents
Craig E. Dixon, Matthew R. Netherton, and Kim M. Baines*
Contribution from the Department of Chemistry, UniVersity of Western Ontario,
London, Ontario, Canada N6A 5B7
ReceiVed May 22, 1998
Abstract: Methylmagnesium iodide (or bromide) has been found to add to tetramesitylgermasilene and
tetramesityldigermene. The addition to the germasilene is regioselective, with the methyl group adding to the
silicon end of the silicon-germanium double bond to produce a germylmagnesium iodide (or bromide) species.
The germyl Grignard reagents give the corresponding germanes upon hydrolysis. At 110 °C in the presence
of excess methylmagnesium halide, the mesityl substituents on the germyl Grignard reagent germanium atom
were exchanged for methyl groups. A mechanism involving the R-elimination of MesMgX followed by the
addition of MeMgX to the intermediate germylene has been proposed to explain the observed ligand exchange.
Evidence for the presence of intermediate germylenes has been obtained in trapping experiments with 2,3-
dimethylbutadiene.
Introduction
reagents, the addition of Grignard reagents to germasilenes
appeared to be a potentially novel way of generating these
compounds. Thus, the reaction between tetramesitylgermasilene
and -digermene (for comparison purposes) and methyl Grignard
reagents was examined under different conditions.
Much has been learned about the chemistry of relatively stable
or stable disilenes, germasilenes, and digermenes since the
discovery of these compounds about 15 years ago.1 Surpris-
ingly, however, the reactivity of these compounds toward
Grignard reagents is completely unknown. The only reports,
to our knowledge, on the reaction between Grignard reagents
and doubly bonded silicon or germanium compounds involve
the reaction with a stable silene2 or a stable germaphosphene.3
With such a paucity of information available, we decided to
investigate the reaction between Grignard reagents and tet-
ramesitylgermasilene. In particular, we were interested in the
regiochemistry of the reaction, if, indeed, the Grignard reagent
added. Furthermore, considering the recent interest in the
generation and chemistry of both germyl4 and silyl5 Grignard
Results and Discussion
The thermolysis6 or photolysis7 of hexamesitylsiladigermirane
(1) has been shown to give tetramesitylgermasilene and dimesi-
tylgermylene regioselectively. Hexamesitylsiladigermirane is
unreactive toward methylmagnesium bromide in the dark.
Similarly, the thermolysis8 or photolysis9 of hexamesitylcyclo-
trigermane10 (2) yields tetramesityldigermene and dimesitylger-
mylene (eq 1).
* To whom correspondence should be addressed. E-mail: kbaines2@
julian.uwo.ca.
(1) Reviews: (a) Okazaki, R.; West, R. AdV. Organomet. Chem. 1996,
39, 231-273. (b) Raabe, G.; Michl, J. In The Chemistry of Organic Silicon
Compounds; Patai, S., Rappoport, Z., Eds.; Wiley; New York, 1989; pp
1015-1142. (c) West, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 1201-
1211. (d) Baines, K. M.; Stibbs, W. G. AdV. Organomet. Chem. 1996, 39,
275-324. (e) Escudie´, J.; Couret, C.; Ranaivonjatovo, H.; Satge´, J. Coord.
Chem. ReV. 1994, 130, 427-480.
Hexamesitylsiladigermirane (1) was photolyzed at -78 °C
in toluene in the presence of excess tris(trimethylsilyl)silane.11
Methylmagnesium bromide was then added to the yellow
solution in the cold. The color of the solution did not fade,
(2) Brook, A. G.; Chiu, P.; McClenaghnan, J.; Lough, A. J. Organome-
tallics 1991, 10, 3292-3301.
(3) Escudie´, J.; Couret, C.; Andrianarison, M.; Satge´, J. J. Am. Chem.
Soc. 1987, 109, 386-390.
(4) (a) Castel, A.; Rivie`re, P.; Satge´, J.; Ko, Y.-H. J. Organomet. Chem.
1988, 342, C1-C4. (b) Castel, A.; Rivie`re, P.; Satge´, J.; Ahbala, M.;
Abdennadher, C.; Desor, D. Main Group Met. Chem. 1993, 16, 291-303.
(c) Mochida, K.; Chiba, H. J. Organomet. Chem. 1994, 473, 45-54. (d)
Nosov, K. S.; Lalov, A. V.; Egorov, M. P.; Nefedov, O. M. Russ. Chem.
Bull. 1996, 45, 2673-2674.
(5) (a) Reich, H. J.; Holtan, R. C.; Bolm, C. J. Am. Chem. Soc. 1990,
112, 5609-5617. (b) Comins, D. L.; Killpack, M. O. J. Am. Chem. Soc.
1992, 114, 10972-10974. (c) Krempner, C.; Oehme, H. J. Organomet.
Chem. 1994, 464, C7-C10. (d) Krempner, C.; Reinke, H.; Oehme, H.
Angew. Chem., Int. Ed. Engl. 1994, 33, 1615-1618. (e) Goddard, R.;
Kru¨ger, C.; Ramadan, N. A.; Ritter, A. Angew. Chem., Int. Ed. Engl. 1995,
34, 1030-1032.
(6) Baines, K. M.; Cooke, J. A. Organometallics 1991, 10, 3419-3421.
(7) Baines, K. M.; Cooke, J. A. Organometallics 1992, 11, 3487-3488.
(8) Ando, W.; Tsumuraya, T. J. Chem. Soc., Chem. Commun. 1989, 770-
772.
(9) Ando, W.; Sato, S.; Tsumuraya, T. Organometallics 1988, 7, 2015-
2019.
(10) Ando, W.; Tsumuraya, T. J. Chem. Soc., Chem. Commun. 1987,
1514-1515.
(11) Our initial attempts to separate the products from the photolysis of
1 at -78 °C in toluene in the presence of Et3SiH as a trapping reagent for
Mes2Ge: were unsuccessful, and thus (Me3Si)3SiH was chosen as an
alternative trapping reagent: Pannell, K. H.; Brun, M.-C.; Sharma, H.; Jones,
K.; Sharma, S. Organometallics 1994, 13, 1075-1077.
S0002-7863(98)01787-9 CCC: $15.00 © 1998 American Chemical Society
Published on Web 09/25/1998

10366 J. Am. Chem. Soc., Vol. 120, No. 40, 1998
Dixon et al.
and thus the reaction mixture was warmed slowly to room
temperature. The reaction mixture was hydrolyzed using
aqueous NH4Cl. Two major products, 5 and 6, were observed
dation of HSi(SiMe3)3, HSi(SiMe3)(OSiMe3)2, which may have
been present in small amounts.15 We are continuing to
investigate this possibility.
1
by H NMR spectroscopy in approximately a 1:1 ratio (eq 2).
To compare the observed reactivity of tetramesitylgermasilene
and methylmagnesium bromide with tetramesityldigermene,
hexamesitylcyclotrigermane (2) was photolyzed at -78 °C in
the presence of excess HSi(SiMe3)3 (eq 2). Addition of
Grignard reagent to a cold solution of the digermene resulted
in the immediate discharge of the yellow-green color associated
with the digermene. Following quenching of the reaction
mixture with aqueous NH4Cl, two products, 6 and 7,4b were
formed in a 1:1 ratio as determined by 1H NMR spectroscopy.
Cophotolysis of either hexamesitylsiladigermirane or -cyclo-
trigermane in the presence of methylmagnesium iodide at
approximately -70 °C also results in the formation of 5 and 7,
respectively, in addition to MeMes2GeH16 (8), apparently from
addition of the Grignard reagent to dimesitylgermylene. Thus,
at low temperature, it appears that the Grignard reagent will
add across the double bond of the dimetallene (generated by
the photolysis of 1 or 2), producing a germyl Grignard
intermediate, which can be protonated by hydrolysis to give
the observed products (eq 3). With tetramesitylgermasilene,
Compound 5 was readily identified by NMR and IR spectros-
copy and mass spectrometry. The H NMR spectrum of 5
1
exhibited resonances for two different mesityl groups as well
as singlets consistent with an M-H moiety (5.73 ppm) and an
M-Me group (1.24 ppm). The IR spectrum showed an
absorbance at 2026 cm-1, which supports the assignment of
the M-H resonance in the 1H NMR spectrum as Ge-H. The
resonance observed at -17.83 ppm in the 29Si NMR spectrum
of 5 is not in the correct chemical shift range for a diaryl Si-H
moiety. The 29Si NMR chemical shift for the isomeric Mes2-
MeGeSiHMes2 was observed at -48.41 ppm (1JSi-H ) 189
Hz),12 confirming the assigned regiochemistry of 5.
Compound 6 was also identified by IR and NMR spectros-
1
copy and mass spectrometry. The H NMR spectrum of 6
the anionic portion of the Grignard reagent adds to the silicon
end of the Si-Ge double bond regioselectively. The high
regioselectivity is, most probably, the result of the greater
electronegativity of germanium in comparison to that of
silicon,17 although the greater strength of the Si-C versus the
Ge-C bond may contribute.18 The regioselectivity of the
cleavage of the π bond of the germasilene is the same as that
observed in the anionic cleavage of Si-Ge σ bonds.19
The initial results suggest that addition of methylmagnesium
halides to the M1-M2 double bonds of germasilenes and
digermenes is straightforward. However, when tetramesitylger-
masilene or -digermene was generated thermally from 1 or 2,
respectively, in the presence of an excess of methylmagnesium
bromide or iodide, some very unexpected chemistry was
observed. Thermolysis of 1 in the presence of methylmagne-
sium bromide followed by quenching with aqueous NH4Cl
yielded a single product, 9, in very high yield (eq 4). Compound
9 was identified by NMR and IR spectroscopy and mass
spectrometry. The 1H NMR spectrum showed one distinct
mesityl group along with a septet, a singlet, and a doublet
revealed one type of mesityl group, one M-H resonance at 5.32
ppm, and two different trimethylsilyl groups in a ratio of 2:1.
The highest mass ion was found at m/z 592. Exact mass
determination of the parent ion corresponded to a molecular
formula of C27H50GeO2Si4. The IR absorption at 1995 cm-1
as well as the absence of any large coupling in the 1H-coupled
29Si NMR spectrum led to the assignment of the Ge-H moiety.
The chemical shifts of 8.71 and -20.58 ppm in the 29Si NMR
spectrum are consistent with a trimethylsiloxy- and a silyl-
substituted trimethylsilyl group, respectively.13 All these data
led to the structural assignment of 6. The structure (Me3Si)2-
(Me3SiO)SiOGeMes2H was eliminated on the basis of the
chemical shift of the germane hydrogen (5.32 ppm). Silyl-
substituted dimesitylgermanes have a chemical shift of ap-
proximately 5-6 ppm (for example: MeMes2SiGeMes2H, GeH
at 5.73 ppm; MeOMes2SiGeMes2H, GeH at 5.57 ppm6), whereas
the chemical shifts of alkoxy- or chloro-substituted dimesi-
tylgermanes are typically about 1 ppm downfield (for ex-
ample: (MeO)Mes2GeH, GeH at 6.67 ppm;6 ClMes2GeH, GeH
at 6.7 ppm14). The formation of 6 is, indeed, surprising. It is
known that the addition of the Grignard reagent to tetramesi-
tyldigermene (and, presumably, also the germasilene) is not
related to the formation of 6: photolysis of hexamesitylcyclo-
trigermane (2) at -70 °C in toluene in the presence of HSi-
(SiMe3)3 followed by quenching with methanol gave a 1:1 ratio
of 6 and Mes2Ge(OMe)GeHMes2.6 It is possible that dimesi-
tylgermylene inserts preferentially into the product of autoxi-
(15) Chatgilialoglu, C.; Guarini, A.; Guerrini, A.; Seconi, G. J. Org.
Chem. 1992, 57, 2207-2208.
(16) Castel, A.; Rivie`re, P.; Satge´, J.; Ko, H. Y. Organometallics 1990,
9, 205-210.
(17) (a) Allred, A. L.; Rochow, E. G. J. Inorg. Nucl. Chem. 1958, 5,
269-288. (b) Allred, A. L.; Rochow, E. G. J. Inorg. Nucl. Chem. 1958, 5,
264-268. (c) Allred, A. L. J. Inorg. Nucl. Chem. 1961, 17, 215-221.
(18) (a) Jackson, R. A. J. Organomet. Chem. 1979, 166, 17-19. (b)
Basch, H.; Hoz, T. In The Chemistry of Organic Germanium, Tin and Lead
Compounds; Patai, S., Ed.; Wiley, New York, 1995; pp 1-96. The strength
of the Si(Ge)-Mg bond is unknown.
(19) (a) Kabaki, M.; Inoue, S.; Nagata, Y.; Sato, Y. Synth. Commun.
1990, 20, 3245-3252. (b) Mochida, K.; Suzuki, H.; Nanba, M.; Kugita,
T.; Yokoyama, Y. J. Organomet. Chem. 1995, 499, 83-88. (c) Dixon, C.
E.; Liu, H. W.; Vander Kant, C. M.; Baines, K. M. Organometallics 1996,
15, 5701-5705.
(12) Baines, K. M.; Groh, R. J.; Joseph, B.; Parshotam, U. Organome-
tallics 1992, 11, 2176-2180.
(13) Marsmann, H. In NMR Basic Principles and Progress; Diehl, P.,
Fluck, E., Kosfeld, R., Eds.; Springer-Verlag: Berlin, 1981; Vol. 17, pp
65-235.
(14) Rivie`re, P.; Rivie`re-Baudet, M.; Castel, A.; Satge´, J. Synth. React.
Inorg. Met.-Org. Chem. 1987, 17, 539-557.

Ligand Exchange with Germyl Grignard Reagents
J. Am. Chem. Soc., Vol. 120, No. 40, 1998 10367
Scheme 1
consistent with the Ge-H, the Si-CH3, and the Ge(CH3)2
moieties found in 9, respectively. The IR spectrum exhibited
an absorbance at 2100 cm-1, which is consistent with a Ge-H
stretching vibration. The 29Si NMR resonance at -20.20 ppm,
again, suggests the absence of a diaryl Si-H moiety.
Similarly, thermolysis of 2 in the presence of an excess of
methylmagnesium iodide followed by quenching with aqueous
NH4Cl yielded a single product, 10 (eq 4). The spectral data
of 10 were very similar to those of 9.
nesium bromide yielded 16 upon quenching of the reaction
mixture with D2O (eq 5). This result supports the presumption
The isolation of 9 and 10 as the sole reaction products from
the above experiments was interesting for a number of reasons.
First, there appears to have been an exchange of mesityl groups
for methyl groups at the germanium atom. Second, there were
no compounds observed that were obviously derived from
reaction between dimesitylgermylene and the Grignard reagent.
The products of the cyclotrigermane thermolyses in the presence
of the Grignard reagent vary with time. For example, if the
thermolysis of 2 is quenched after 4 h, products 8 and 11 are
isolated; however, after 18 h, products 10 and 11 are obtained.
The ratio of the products also appears to be dependent on the
reaction conditions. Compound 10 is the only product formed
when the amount of ether (the Grignard reagent solvent) is kept
to a minimum. The isolation of 11 suggests that the mesityl-
methyl exchange was occurring in a stepwise manner.
that the final product in each of the thermolysis experiments is
basic in nature and that the compound is, presumably, 15.
Central to this mechanism is the assumption that the first-
formed intermediate in these thermolyses reactions is the germyl
Grignard reagent 12. When a solution of 1223 and 17, generated
by photolysis of 1 or 2 at -70 °C in the presence of an excess
of methylmagnesium iodide, is heated to 110 °C followed by
hydrolysis with aqueous NH4Cl, 9 (M ) Si) and 10 (M ) Ge)
are isolated as the sole products of reaction, respectively (eq
6). The formation of 9 and 10 from solutions containing
To explain the mesityl-methyl exchange, one may invoke
an R-elimination of MesMgBr from the initially formed germyl
Grignard species 12 to generate the metallylgermylene 13
(Scheme 1). A second equivalent of methylmagnesium bromide
may then add to the metallylgermylene intermediate to give the
germyl Grignard species 14. A similar series of R-eliminations
and additions would result in the formation of the germyl
Grignard species 15. Hydrolysis of 15 (M ) Si) would yield
9, whereas hydrolysis of both intermediates 14 and 15 (M )
Ge) would give 11 and 10, respectively.
There are accounts in the literature that offer precedents for
the proposed mechanism. For example, Glockling and Hooton
have reported that Bu3SnLi apparently dissociates, by R-elim-
ination, to Bu2Sn: and BuLi.20 A similar R-elimination has
been reported by Castel and co-workers to occur from Ph2GeHLi
to give LiH and the corresponding germylene species, which
reacts further to yield polygermanes, following hydrolysis.16
Furthermore, Seyferth21 and others22 have postulated that
diorganogermylenes, R2Ge:, may react with Grignard reagents,
RMgX, to form germyl Grignard species of the type R3GeMgX.
Confirmation of the presence of a germyl Grignard reagent,
as proposed in the above mechanism, was obtained by trapping
experiments with deuterium oxide. Thermolysis of hexamesi-
tylsiladigermirane in the presence of an excess of methylmag-
intermediates 12 and 17 supports the idea that intermediates 12
(M ) Si or Ge) and 17 are formed first upon the thermolysis
of hexamesitylsiladigermirane or -cyclotrigermane in the pres-
ence of methylmagnesium halide, and that thermolysis of 12
(M ) Si or Ge) and 17 ultimately leads to 9 and 10, respectively.
Consistent with the earlier thermolyses, there were no products
isolated from either experiment that could be identified as being
derived from reaction of intermediate 17, which is the expected
product of reaction from dimesitylgermylene and methylmag-
nesium bromide or iodide.
It is believed that intermediate 17 also undergoes a series of
R-eliminations (of MesMgX) and additions of CH3MgX, the
end result of which is the production of trimethylgermylmag-
nesium halide. Upon hydrolysis, however, trimethylgermyl-
(20) Glockling, F.; Hooton, K. A. J. Chem. Soc. 1963, 1849-1854.
(21) Seyferth, D. J. Am. Chem. Soc. 1957, 79, 2738-2740.
(22) Mendelsohn, J.-C.; Metras, F.; Lahourne`re, J.-C.; Valade, J. J.
Organomet. Chem. 1968, 12, 327-340.
(23) The presence of 12 (M ) Si or M ) Ge) and 17 was confirmed
prior to heating by analysis of an aliquot of the reaction mixture. Following
hydrolysis of the aliquot, the only products observable by 1H NMR
spectroscopy were 5 (M ) Si) or 7 (M ) Ge) and 8.

10368 J. Am. Chem. Soc., Vol. 120, No. 40, 1998
Dixon et al.
magnesium halide will yield trimethylgermane, which is a
relatively volatile compound (bp ) 26 °C) and, thus, difficult
to isolate. To support, or exclude, the formation of Me3GeH
when intermediate 17 is heated in the presence of an excess of
methylmagnesium iodide, hexamesitylcyclotrigermane was heated
to 110 °C for 12 h in the presence of excess methylmagnesium
iodide. Following hydrolysis with NH4Cl, analysis of the
headspace gas revealed the presence of two additional com-
pounds in the GC-MS trace, as compared to the GC-MS trace
of the headspace gas of the reaction mixture prior to hydrolysis.
One of the compounds was readily identified as mesitylene
(1,3,5-trimethylbenzene) by comparison of the experimental
mass spectrum with the known mass spectrum for mesitylene.
The mass spectrum of the other compound was found to be
consistent with Me3GeH. There was a fragment cluster at m/z
118.24 A comparison of the calculated theoretical cluster for
C3H10Ge to the experimental fragment cluster found at m/z 118
showed a very good correlation between the observed and
calculated isotopic ratios. Thus, Me3GeH appears to be a
product in the thermolysis of hexamesitylcyclotrigermane in the
presence of excess methylmagnesium iodide.
Intercepting a reactive intermediate proposed to be participat-
ing in a reaction has long been taken as evidence for the
existence of that intermediate and, thus, taken as support for a
proposed mechanism. Therefore, support for the R-elimination
mechanism may be obtained by intercepting any of the proposed
germylene intermediates thought to be produced by the R-e-
limination of MesMgBr. Since conjugated dienes are well-
known traps for germylene species,25 any germylene interme-
diates produced during the thermolysis experiments should
readily be intercepted by the diene. Isolation of any such
trapped germylene species could be taken as strong evidence
for the presence of these species in the reaction mixture and,
furthermore, taken as evidence for the operation of the proposed
R-elimination mechanism.
NMR spectrum as CH2, and the HETCOR NMR spectrum
demonstrated that this signal correlates with the resonances at
2.05 and 2.28 ppm in the H dimension. Furthermore, reso-
1
nances found at 18.92 and 4.69 ppm were shown to be CH3 by
the DEPT NMR spectrum, and these signals correlated with
1
resonances at 1.69 and 0.98 ppm in the H NMR spectrum,
which are assigned to the dC-CH3 and Ge-CH3 moieties,
respectively. The IR and mass spectra also agree with the
assignment for 18. Compound 19 was readily identified by 1H
and 13C NMR spectroscopy. Resonances for a single mesityl
group and two singlets, which may be assigned to the CdC-
CH3 (1.75 ppm) and Ge-CH3 (0.41 ppm) methyl groups in
structure 19, were observed in the 1H NMR spectrum. Signals
consistent with an AB spin system (1.68 and 2.02 ppm; JAB
)
15 Hz) were also clearly observable in the 1H NMR spectrum,
which is again entirely compatible with the assigned germacy-
clopentene structure of 19. The 13C NMR spectrum exhibited
the correct number of resonances, which are in the correct
chemical shift range for the carbon atoms found in the above
structure. Again, the IR and mass spectra also agree with the
assignment for 19.
Photolysis of hexamesitylcyclotrigermane in the presence of
exactly 2 equiv of methylmagnesium iodide produced a solution
of 12 (M ) Ge) and 17 in a 1:1 ratio as determined by
examination of a hydrolyzed aliquot by1H NMR spectroscopy.
Addition of 2,3-dimethylbutadiene to the solution of 12 (M )
Ge) and 17 followed by heating of the reaction mixture to 110
°C for several hours produced 18 and 19 (eq 7).
Structures 18 and 19 are consistent with the trapping of
mesityl(dimesitylmethylgermyl)germylene (13, M ) Ge, Scheme
1) and mesitylmethylgermylene (produced by R-elimination of
MesMgI from 17) by 2,3-dimethylbutadiene. The formation
of these germylene intermediates is consistent with the R-elim-
ination mechanism proposed for the mesityl-methyl substitution
observed in the thermolysis experiments. Thus, isolation of 18
and 19 is taken as support for the operation of this mechanistic
pathway.
The identification of 18 was readily achieved by 1H and 13
C
NMR spectroscopy and mass spectrometry. The 1H NMR
spectrum exhibited resonances for two different mesityl groups
in a ratio of 2:1 as well as a singlet at 0.98 ppm, which is
assigned to the Ge-CH3 group. Moreover, a singlet at 1.69
Summary
In summary, the work detailed in this paper represents the
first investigations into dimetallene reactivity toward Grignard
reagents. It has been found that, under mild conditions,
methylmagnesium halide will add, with apparently high regi-
oselectivity, to tetramesitylgermasilene. The methyl group of
the Grignard reagent adds to the silicon atom of the Si-Ge
double bond, producing an intermediate germyl Grignard
species. The germyl Grignard species so produced can then
be protonated upon hydrolysis to yield the corresponding
germane.
Likewise, tetramesityldigermene will add methylmagnesium
halide under mild conditions to yield a germyl Grignard reagent
that gives the corresponding germane upon hydrolysis. Quali-
tatively, MeMgX adds more readily to the digermene (rapid
reaction at -78 °C), compared to the germasilene (reaction at
approximately -10 °C) presumably because of the greater
polarizability of the Ge-Ge double bond. The nature of the
addition is unknown at this point.
1
ppm in the H NMR spectrum is consistent with the vinylic
methyl group of the germacyclopentene ring. There is also an
AB spin system (2.05 and 2.28 ppm; JAB ) 15 Hz) in the1H
NMR spectrum, which is compatible with the methylene
hydrogen atoms of the germacyclopentene structure assigned
to 18. The DEPT and 1H/13C HETCOR NMR spectra are each
supportive of these assignments. For example, the DEPT NMR
spectrum identifies the signal found at 30.76 ppm in the 13C
(24) Shifts in mass peaks to lower apparent masses have been reported
in ion trap mass spectrometry: Bortolini, O.; Traldi, P. In Practical Aspects
of Ion Trap Mass Spectrometry; March, R. E., Todd, J. F. J., Eds.; CRC
Press: Boca Raton, FL, 1995; Vol. 2, pp 145-159.
(25) (a) Neumann, W. P. Chem. ReV. 1991, 91, 311-334. (b) Rivie`re,
P.; Rivie`re-Baudet, M.; Satge´, J. In ComprehensiVe Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon
Press: New York, 1982; Vol. 2, pp 399-518. (c) Rivie`re, P.; Rivie`re-
Baudet, M.; Satge´, J. In ComprehensiVe Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Davies, A. G., Eds.; Pergamon:
New York, 1995; Vol. 2, pp 137-216.

Ligand Exchange with Germyl Grignard Reagents
J. Am. Chem. Soc., Vol. 120, No. 40, 1998 10369
(dimesitylmethylgermyl)dimesitylgermane (7) (17 mg) in a ratio of 10:1
The reactivity of tetramesitylgermasilene toward methylmag-
nesium iodide (or bromide) under thermal conditions revealed
some interesting and unexpected chemistry. It was found that,
at elevated temperatures, the germyl Grignard intermediate
generated by reaction of the methyl Grignard reagent with the
germasilene underwent an unprecedented mesityl-methyl ligand
exchange. The exchange was also observed upon addition of
MeMgX to tetramesityldigermene at elevated temperatures. The
formation of the products can be explained by R-elimination of
MesMgI (or Br) from the germyl Grignard intermediate to give
a germylene which subsequently reacts with the excess MeMgX.
The intermediate germylene was trapped with 2,3-dimethylb-
utadiene, providing excellent support for the proposed mecha-
nism.
1
as determined by H NMR spectroscopy.
(Dimesitylmethylsilyl)dimesitylgermane (5): IR (thin film, cm-1
)
2921 (s), 2025 (m, Ge-H), 1603 (s), 1551 (w), 1451 (s), 1027 (m),
1
847 (s), 803 (m), 739 (m), 703 (w), 684 (w); H NMR (ppm) 6.73 (s,
4 H, Mes H), 6.67 (s, 4 H, Mes H), 5.73 (s, 1 H, GeH), 2.28 (s), 2.25
(s, 24 H total, Mes oCH3), 2.11 (s), 2.08 (s, 12 H total, Mes pCH3),
1.24 (s, 3 H, SiCH3); 13C NMR (ppm) 144.54, 143.86, 138.58, 137.67,
136.65, 134.37 (Mes C), 129.87, 129.02 (Mes CH), 24.82, 24.78, 20.99,
20.90 (Mes CH3), 6.34 (Si-CH3); 29Si NMR (ppm) -17.83; MS (m/z)
594 (M+, 0.86), 431 (Mes3Ge, 2.1), 312 (Mes2Ge, 35), 281 (Mes2SiCH3,
100), 192 (MesGe - H, 14); high-resolution MS, calcd for C37H48-
SiGe 594.2737, found 594.2521.
[Bis(trimethylsiloxy)(trimethylsilyl)silyl]dimesitylgermane (6): IR
1
(thin film, cm-1) 1995 (m, GeH); H NMR (ppm) 6.78 (s, 4 H, Mes
H), 5.32 (s, 1 H, GeH), 2.53 (s, 12 H, Mes oCH3), 2.11 (s, 6 H, Mes
pCH3), 0.15 (s, 9 H, SiSi(CH3)3), 0.14 (s, 18 H, OSi(CH3)3); 13C NMR
(ppm) 143.69, 137.66, 135.49, 128.76 (Mes C), 25.29 (Mes oCH3),
21.01 (Mes pCH3), 2.25 (OSi(CH3)3), -1.56 (SiSi(CH3)3); 29Si NMR
(ppm) 8.71 (decet, OSi(CH3)3, J ) 6.6 Hz), -15.99 (multiplet, central
Si), -20.58 (decet, Si(CH3)3, J ) 6.6 Hz); MS (m/z) 592 (M+, 3), 577
(M+ - CH3, 1), 312 (Mes2Ge, 10), 279 ((Me3SiO)2SiSiMe3, 100), 191
(51), 117 (Me3SiOSi, 13), 91 (Me3SiO, 14), 73 (Me3Si, 40); high-
resolution MS calcd for C27H50GeO2Si4 592.2100, found 592.2080, calcd
for C9H27O2Si4 279.1088, found 279.1095.
Photolysis of Hexamesitylcyclotrigermane in the Presence of
(Me3Si)3SiH Followed by Addition of Methylmagnesium Bromide.
A solution of Ge3Mes6 (100 mg, 0.11 mmol) and excess (Me3Si)3SiH
in toluene (4 mL) was photolyzed at -78 °C for 16 h. The reaction
mixture was quenched with excess (5×) CH3MgBr dissolved in diethyl
ether. The green-yellow color of the solution disappeared immediately
upon addition of the Grignard reagent. The reaction mixture was then
hydrolyzed with saturated NH4Cl solution. The aqueous and organic
layers were separated, and the aqueous phase was extracted with Et2O.
The combined organic extracts were dried over MgSO4 and then filtered
to remove the MgSO4, followed by evaporation of the solvent. The
products were separated by preparative chromatography using the
Chromatotron (8:92 CH2Cl2/hexanes) to give (Me3SiO)2(Me3Si)-
SiGeMes2H (6) (56 mg, 0.095 mmol, 86%) and (dimesitylmethylgermyl)-
dimesitylgermane4b (7) (50 mg, 0.078 mmol, 71%).
We believe this is the first evidence for the facile elimination
of (aryl) Grignard reagents from germyl Grignard reagents. Our
findings are important for two reasons. Germylenes are
important intermediates in organogermanium chemistry.25 Our
results provide a new and unique source of germylenes.
Furthermore, considering the recent interest in germyl Grignard
reagents,4 this new aspect of the reactivity of these compounds
should play a critical role in understanding the chemical
reactions involving these compounds. We are continuing our
investigations into the generality of the addition of Grignard
reagents and other organometallic reagents to stable dimetallenes
as well as the chemistry of the resulting adducts.
Experimental Section
All experiments were carried out in flame-dried glassware under an
atmosphere of argon. Toluene and Et2O were freshly distilled from
sodium/benzophenone. Methylmagnesium iodide and bromide were
used in the following experiments. Methylmagnesium bromide was
obtained from the Aldrich Chemical Co., whereas methylmagnesium
iodide was prepared in the laboratory with magnesium purchased from
Lancaster Chemical Co. and methyl iodide purchased from BDH. The
choice of halide did not appear to influence the outcome of the reactions.
Selection of which reagent was to be used was based solely on
availability. Chromatography was carried out using a Chromatotron
(Harrison Research) or on conventional silica gel preparative plates.
Photolyses were carried out at 350 nm using a Rayonet photochemical
reactor.
Photolysis of 2 (50 mg) under the same conditions followed by
quenching the reaction mixture with excess methanol gave a 1:1 ratio
1
of 6 and Mes2(OMe)GeGeMes2H6 as determined by H NMR spec-
troscopy. The reaction was worked up in the usual manner and the
resulting product mixture separated by preparative thin-layer chroma-
tography (92:8 hexanes/CH2Cl2) to give 6 (2.6 mg) and Mes2(OMe)-
GeGeMes2H (5.1 mg).
NMR spectra were recorded on a Varian Gemini 200 (200.1 MHz
for 1H, 50.3 MHz for 13C), an XL-300, or a Varian Gemini 300 (299.9
1
MHz for H, 75.4 MHz for 13C, 59.6 MHz for 29Si) using benzene-d6
(Dimesitylmethylgermyl)dimesitylgermane (7): IR (thin film,
cm-1) 2965 (s), 2922 (s), 2029 (m, Ge-H), 1601 (m), 1555 (m), 1453
(s), 1288 (w), 1261 (w), 1027 (m), 848 (m), 805 (m); 1H NMR (ppm)
6.71 (s, 4 H, Mes H), 6.69 (s, 4 H, Mes H), 5.90 (s, 1 H, GeH), 2.28
(s, 12 H, Mes oCH3), 2.25 (s, 12 H, Mes oCH3), 2.10, 2.09 (each s, 12
H total, Mes pCH3), 1.30 (s, 3 H, GeCH3); 13C NMR (ppm) 143.77,
143.57, 138.44, 137.91, 137.84, 136.11 (Mes C), 129.56, 129.07 (Mes
CH), 24.59, 21.00, 20.89 (Mes CH3), 7.84 (GeCH3); MS (m/z) 637
(M+ - H, 0.3), 623 (M+ - CH3, 0.2), 431 (Mes3Ge, 18), 327 (Mes2-
GeCH3, 100), 313 (Mes2GeH, 14), 191 (MesGe, 14); high-resolution
MS calcd for C37H4774Ge72Ge (M+ - H) 637.2110, found 637.2098.
Thermolysis of Hexamesitylsiladigermirane in the Presence of
Methylmagnesium Bromide. SiGe2Mes6 (100 mg, 0.11 mmol) and
approximately 2 mL of 3.1 M CH3MgBr in diethyl ether (excess) were
dissolved in toluene (4 mL) and heated in an oil bath at 110 °C for 18
h. A cream-colored precipitate was observed. The reaction mixture
was then hydrolyzed with a saturated NH4Cl solution. The aqueous
and organic layers were separated, and the aqueous phase was extracted
with ether/toluene. The combined organic extracts were dried over
MgSO4. Filtration to remove the MgSO4 followed by evaporation of
the solvent yields 9 (40 mg, 95%). Compound 9 can be purified by
chromatography.
as a solvent, unless otherwise noted. The standards were as follows:
residual C6D5H 7.15 ppm for 1H spectra; C6D6 or CDCl3 central
transition for13C NMR spectra; and Me4Si as an external standard, 0
ppm for 29Si. IR spectra were recorded (cm-1) as thin films on a Perkin-
Elmer System 2000 FT IR spectrometer. A Finnegan MAT model 8230
instrument, 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).
Photolysis of Hexamesitylsiladigermirane in the Presence of
(Me3Si)3SiH Followed by Addition of Methylmagnesium Bromide.
A solution of SiGe2Mes6 (40 mg, 0.046 mmol; contaminated with some
Ge3Mes6) and excess (Me3Si)3SiH in toluene (4 mL) was photolyzed
at -78 °C for 8 h. The reaction mixture was quenched with excess
(100×) CH3MgBr dissolved in diethyl ether. The reaction mixture was
kept cold overnight and then allowed to warm gradually over 8 h. The
reaction mixture was then hydrolyzed with saturated NH4Cl solution.
The aqueous and organic layers were separated, and the aqueous phase
was extracted with an Et2O/toluene mixture. The combined organic
extracts were dried over MgSO4 and then filtered to remove the MgSO4,
followed by evaporation of the solvent. The residue was separated by
preparative chromatography using the Chromatotron (1:9 CH2Cl2/
hexanes) to give (Me3SiO)2(Me3Si)SiGeMes2H (6) (13 mg, 0.022 mmol,
48%) and a mixture of (dimesitylmethylsilyl)dimesitylgermane (5) and
(Dimesitylmethylsilyl)dimethylgermane (9): IR (thin film, cm-1
)
1
2001 (m, GeH); H NMR (ppm) 6.69 (s, 4 H, Mes H), 4.15 (septet, 1

10370 J. Am. Chem. Soc., Vol. 120, No. 40, 1998
Dixon et al.
H, J ) 4 Hz, GeH), 2.33 (s, 12 H, Mes oCH3), 2.09 (s, 6 H, Mes
pCH3), 0.82 (s, 3 H, SiCH3), 0.30 (d, 6 H, J ) 4 Hz, GeCH3); 13C
NMR (ppm) 143.18, 138.34, 133.98, 129.53 (Mes C), 24.53, 20.97
(Mes CH3), 3.71 (SiCH3), -4.95 (GeCH3); 29Si NMR (ppm) -20.20;
MS (m/z) 386 (M+, 2), 281 (Mes2SiCH3, 100), 161 (MesSiCH3 - H,
13); high-resolution MS calcd for C21H31SiGe (M+ - H) 385.14068,
found 385.14072.
The reaction was repeated (15 mg of SiGe2Mes6). The thermolysis
was carried out in C6D6 for 18 h at 105 °C in the presence of excess
MeMgBr in ether. The reaction mixture was quenched with a saturated
NH4Cl solution. The aqueous and organic layers were separated, and
the aqueous phase was extracted with deuterated benzene. The
combined organic extracts were dried over MgSO4 and then analyzed
by 1H NMR spectroscopy. Mesitylene was found to be present as
confirmed by spiking the sample with authentic material.
(dimesitylmethylsilyl)dimesitylgermane (5) and dimesitylmethylger-
mane16 (8). The original reaction mixture was heated to 110 °C (from
-10 °C) for 6 h. The remaining reaction mixture was then hydrolyzed
with a saturated NH4Cl solution. The aqueous and organic layers were
separated, and the aqueous phase was extracted with hexanes (20 mL
total). The combined organic extracts were dried over MgSO4 prior
to filtration and solvent evaporation, which yielded a white solid residue.
The crude reaction mixture was purified by preparative thin-layer
chromatography (1:9 CH2Cl2/hexanes) to yield (dimesitylmethylsilyl)-
dimethylgermane (9) as the only identifiable product.
Photolysis of Hexamesitylcyclotrigermane in the Presence of
Methylmagnesium Iodide Followed by Thermolysis. Ge3Mes6 (50
mg, 0.054 mmol) and approximately 0.25 mL of 4 M CH3MgI (excess)
were dissolved in toluene (5 mL) and photolyzed at -70 °C for 9 h. A
small portion (approximately 1 mL) of the reaction mixture was
removed and hydrolyzed with a saturated NH4Cl solution. The aqueous
and organic layers were separated, and the aqueous phase was extracted
with hexanes (10 mL total). The combined organic extracts were dried
over MgSO4 prior to filtration and solvent evaporation, which yielded
a white solid residue. Examination of this residue showed it to be a
1:1 mixture of (dimesitylmethylgermyl)dimesitylgermane (7) and
dimesitylmethylgermane16 (8). The original reaction mixture was heated
to 110 °C (from -70 °C) for 4 h. The reaction mixture was then
hydrolyzed with a saturated NH4Cl solution. The aqueous and organic
layers were separated, and the aqueous phase was extracted with
hexanes (20 mL total). The combined organic extracts were dried over
MgSO4 prior to filtration and solvent evaporation, which yielded a white
solid residue. The crude reaction mixture consisted mainly of (di-
mesitylmethylgermyl)dimethylgermane (10) as determined by 1H NMR
spectroscopy.
The reaction was repeated (30 mg of SiGe2Mes6 contaminated with
Ge3Mes6). The reaction was hydrolyzed with D2O and then worked
up in the usual manner. The product was purified by chromatography
(1:9 CH2Cl2/hexanes) to give a mixture of 16 and (dimesitylmethylger-
myl)deuteriodimethylgermane.
1
(Dimesitylmethylsilyl)deuteriodimethylgermane (16): H NMR
(ppm) 6.71, 6.69, 2.33, 2.10, 2.09, 0.90, 0.81, 0.32, 0.29 (all singlets);
2H{1H} NMR (C6H6, ppm) 4.34 (s, GeD of (dimesitylmethylgermyl)-
deuteriodimethylgermane), 4.17 (GeD of 16).
Thermolysis of Hexamesitylcyclotrigermane in the Presence of
Methylmagnesium Bromide. (1) Ge3Mes6 (100 mg, 0.11 mmol) and
approximately 2 mL of 3.1 M CH3MgBr in diethyl ether (excess) were
dissolved in toluene (3 mL) and heated in an oil bath at 80 °C for 4 h.
A white precipitate was observed to form. The reaction mixture was
then hydrolyzed with a saturated NH4Cl solution. The aqueous and
organic layers were separated, and the aqueous phase was extracted
with ether. The combined organic extracts were dried over MgSO4
and filtered, and the solvents were evaporated. Analysis of the crude
Thermolysis of Hexamesitylcyclotrigermane in the Presence of
Methylmagnesium Iodide and GC-MS Analysis of Headspace Gas.
Ge3Mes6 (70 mg, 0.075 mmol) and approximately 0.3 mL of 4 M CH3-
MgI (excess) were dissolved in toluene (5 mL) and heated to 110 °C
for 12 h. Following this time, 100 µL of the headspace gas was
withdrawn from the reaction vessel and injected into a Varian Saturn
4D GC-MS (-40 °C). Once the reference GC-MS trace was
obtained, the reaction was quenched by injecting 1 mL of a saturated
NH4Cl solution into the sealed reaction vessel. When the exothermic
reaction due to quenching subsided, a second 100 µL of the headspace
gas was injected into the GC-MS. With the GC-MS analysis
complete, the aqueous and organic layers of the hydrolyzed reaction
mixture were separated, and the aqueous phase was extracted with
hexanes. The combined organic extracts were dried over MgSO4 prior
to filtration and solvent evaporation. Analysis of the crude reaction
1
reaction mixture by H NMR spectroscopy revealed the presence of
816 and 11. Chromatographic separation (8:92 CH2Cl2/hexanes) yielded
11 (52 mg, 0.098 mmol, 89%). Compound 8 was not isolated.
(2) Ge3Mes6 (60 mg, 0.066 mmol) and approximately 1.5 mL of
3.1 M CH3MgBr in diethyl ether (excess) were dissolved in toluene (4
mL) and heated in an oil bath at 105 °C for 18 h. Following this time,
the reaction mixture was hydrolyzed with a saturated NH4Cl solution.
The aqueous and organic layers were separated, and the aqueous phase
was extracted with ether. The combined organic extracts were dried
over MgSO4 and filtered, and the solvents were evaporated. Analysis
1
of the crude reaction mixture by H NMR spectroscopy revealed the
presence of 10 and 11 in a 1:1.3 ratio, respectively. Chromatographic
separation (Chromatotron; eluent varied from 8% CH2Cl2 in hexanes
to 25%) of the reaction mixture gave 11 (17 mg, 0.033 mmol, 50%).
Compound 10 was not isolated from this reaction mixture.
1
mixture by H NMR spectroscopy revealed the presence of 10 as the
major product. Preparative thin-layer chromatography (5:95 CH2Cl2/
hexanes) gave 7 (21 mg, 60%) in pure form.
1,1-Dimesityl-1,2,2-trimethyldigermane (10): IR (thin film, cm-1
)
1,1,2-Trimesityl-1,2-dimethyldigermane (11): IR (thin film cm-1
)
3032 (m), 2972 (s), 2920 (s), 2875 (m), 2008 (s, GeH), 1611 (m), 1563
(m), 1454 (m), 1417 (m), 1035 (m), 852 (m), 837 (m); 1H NMR (ppm)
6.71 (s, 4 H, Mes H), 4.32 (septet, 1 H, J ) 3.9 Hz, GeH), 2.33 (s, 12
H, Mes oCH3), 2.10 (s, 6 H, Mes pCH3), 0.90 (s, 3 H, GeCH3), 0.32
(d, 6 H, J ) 3.9 Hz, GeCH3); 13C NMR (ppm) 142.57, 137.71, 137.66,
2967 (s), 2919 (s), 2030 (m, GeH), 1602 (m), 1557 (m), 1454 (s), 1289
(w), 1235 (w), 1027 (w), 849 (s), 803 (s), 780 (s); H NMR (ppm)
1
6.72 (s, Mes H), 6.70 (s, Mes H), 6.69 (s, Mes H), 5.19 (q, J ) 4.1 Hz,
GeH), 2.31 (s, Mes oCH3), 2.19 (s, Mes oCH3), 2.18 (s, Mes oCH3),
2.11 (s, Mes pCH3), 2.09 (s, Mes pCH3), 0.97 (s, GeCH3), 0.75 (d, J
) 4.1 Hz, GeCH3); 13C NMR (ppm) 144.09, 143.21, 142.89, 139.29,
138.53, 138.25, 138.03, 137.96, 134.87, 129.68, 129.57, 129.13, 25.21,
25.07, 24.98, 21.36, 21.28, 21.25, 5.55, -1.68; MS (m/z) 550 (4), 533
(M+, 3), 327 (Mes2GeCH3, 100), 312 (Mes2Ge, 13), 221 (MesGe(CH3)2,
23), 206 (MesGeCH3, 21), 191(MesGe, 16), 119 (Mes, 55).
Photolysis of Hexamesitylsiladigermirane in the Presence of
Methylmagnesium Iodide Followed by Thermolysis. SiGe2Mes6 (50
mg, 0.058 mmol) and approximately 0.25 mL of 4 M CH3MgI (excess)
were dissolved in toluene (4 mL) and photolyzed at -60 °C for 4 h.
The reaction mixture was then warmed to -10 °C and allowed to stand
for 12 h. After standing at -10 °C, a small portion (approximately 1
mL) of the reaction mixture was removed and hydrolyzed with a
saturated NH4Cl solution. The aqueous and organic layers were
separated, and the aqueous phase was extracted with hexanes (10 mL
total). The combined organic extracts were dried over MgSO4 prior
to filtration and solvent evaporation, which yielded a white solid residue.
Examination of this residue showed it to be a 1:1 mixture of
129.30, 24.56, 20.96, 3.83, 1.40; MS (m/z) 430 (M+, 4), 415 (M+
-
CH3, 1.6) 327 (Mes2GeCH3, 100), 221 (MesGe(CH3)2, 19), 193 (MesGe,
17), 119 (Mes, 17), 105 ((CH3)2GeH, 8); high-resolution MS calcd for
C21H3272Ge74Ge 430.0937, found 430.0948.
Trimethylgermane: MS (m/z) 206 (10), 118 (85), 104 (100), 89
(50), 74 (15).
Thermolysis of Dimesityl(methyl)germylmagnesium Iodide and
(Dimesitylmethylgermyl)dimesitylgermylmagnesium Iodide in the
Presence of 2,3-Dimethylbutadiene. Ge3Mes6 (50 mg, 0.054 mmol)
and 0.32 mL of 0.33 M CH3MgI (0.11 mmol) were dissolved in toluene
(5 mL) and photolyzed at -70 °C for 4 h. Approximately 0.5 mL of
the reaction mixture was then hydrolyzed with a saturated NH4Cl
1
solution. Following extraction, analysis of this aliquot by H NMR
spectroscopy showed a 1:1 mixture of 7 and 8. Approximately 0.25
mL of 2,3-dimethylbutadiene was added to the remaining reaction
mixture, which was then heated to 110 °C for 16 h. Following this
time, the reaction mixture was quenched with NH4Cl. The aqueous

Ligand Exchange with Germyl Grignard Reagents
J. Am. Chem. Soc., Vol. 120, No. 40, 1998 10371
and organic layers were separated, and the aqueous phase was extracted
with hexanes. The combined organic extracts were dried over MgSO4
prior to filtration and solvent evaporation. Separation of the reaction
mixture by preparative thin-layer chromatography (12:88 CH2Cl2/
hexanes) gave 18 (10 mg, 0.017 mmol, 31%) and 19 (5 mg, 0.017
mmol, 32%), with the best results obtained if the preparative chroma-
tography plate was eluted twice. In addition, 19 was very to difficult
to visualize on the preparative plate. Under these solvent and elution
conditions, 19 has an Rf value of approximately 0.80.
1-Mesityl-1,3,4-trimethyl-1-germacyclopent-3-ene (19): IR (thin
film, cm-1) 3024 (w), 2927 (s), 2867 (m), 1615 (m), 1566 (m), 1499
(s), 1454 (m), 1413 (m), 1058 (m), 882 (w), 830 (w); 1H NMR (ppm)
6.78 (s, 2 H, Mes H), 2.29 (s, 6 H, Mes oCH3), 2.16 (s, 3 H, Mes
pCH3), 2.03 (d, 2 H, AB of CHAHB, J ) 15 Hz), 1.75 (bs with fine
splitting, 6 H, dC-CH3), 1.68 (d, 2 H, AB of CHAHB, J ) 15 Hz),
0.42 (s, 3 H, GeCH3); 13C NMR (ppm) 142.95, 130.45, 128.81, 29.95,
24.29, 21.06, 19.41, -1.13; MS (m/z) 290 (M+, 30), 208 (MesGeCH3,
30), 193 (MesGe, 100), 57 (C4H9, 28); high-resolution MS calcd for
C16H2474Ge, 290.1090, found 290.1091.
1-(Dimesitylmethylgermyl)-1-mesityl-3,4-dimethyl-1-germacyclo-
pent-3-ene (18): IR (thin film, cm-1) 3024 (w), 2927 (s), 2845 (s),
1705 (w), 1608 (m), 1566 (m), 1503 (m), 1458 (m), 1409 (m), 1379
Acknowledgment. Financial assistance from the Natural
Sciences and Engineering Research Council of Canada in the
form of a Summer Research Assistantship to M.R.N. and a grant
to K.M.B. is gratefully acknowledged. We also thank L. Scott
Black for technical assistance.
1
(w), 1058 (m), 882 (w), 852 (w), 834 (w); H NMR (ppm) 6.75 (s, 2
H, Mes H), 6.69 (s, 4 H, Mes H), 2.28 (d, 2 H, AB of CHAHB, J ) 15
Hz), 2.21 (s, 12 H, Mes CH3), 2.15 (s, 9 H, Mes CH3), 2.11 (s, 6 H,
Mes CH3), 2.05 (d, 2 H, AB of CHAHB, J ) 15 Hz), 1.69 (s, 6 H,
dC-CH3), 0.98 (s, 3 H, GeCH3); 13C NMR (ppm) 143.53, 142.70,
139.31, 137.85, 137.45, 136.92, 131.37 (Mes C and dC-CH3), 129.12,
128.73 (Mes CH), 31.14 (dC-CH2), 25.06, 24.63, 21.07, 20.96, 19.16
(Mes CH3), 5.03 (GeCH3); MS (m/z) 598 (M+, 1.5), 518 (Mes2(CH3)-
Supporting Information Available: 1H NMR spectra of
6, 7, 9, 10, 11, 18, and 19 (7 pages, print/PDF). See any current
masthead page for ordering information and Web access
instructions.
GeGeMes, 25), 480 (M+ - Mes, 1.5), 431 (Mes3Ge, 5) 327 (Mes2-
74
GeCH3, 100), 193 (MesGe, 20); high-resolution MS calcd for C34H46
-
Ge72Ge 600.2032, found 600.1918.
JA981787K