Reactivity of a 1-germapropadiene

Article abstract of DOI:10.1021/om980555r

α-Lithiofluorogermane 3 eliminated lithium fluoride to give 1-germapropadiene 1 even at -75°C. The reactivity of 1-germapropadiene 1 was investigated. Compound 1 was not stable above 0°C in solution or 90°C in the solid state. Two C-H insertion cyclic compounds, 8 and 9, were formed as a result of decomposition. Water, methanol, and ethanol added across the Ge=C double bond of 1 to give vinylalkoxy (hydroxy) germanes. Benzophenone did not react with 1 at 0°C, but benzaldehyde gave oxagermetane 13 in good yield. When acetone was introduced to 1, it gave the unexpected product 10, the water adduct.

Full text of DOI:10.1021/om980555r

540
Organometallics 1999, 18, 540-545
Rea ctivity of a 1-Ger m a p r op a d ien e
Barrett E. Eichler, Douglas R. Powell, and Robert West*
Department of Chemistry, The University of Wisconsin, Madison, Wisconsin 53706
Received J uly 1, 1998
R-Lithiofluorogermane 3 eliminated lithium fluoride to give 1-germapropadiene 1 even at
-75 °C. The reactivity of 1-germapropadiene 1 was investigated. Compound 1 was not stable
above 0 °C in solution or 90 °C in the solid state. Two C-H insertion cyclic compounds, 8
and 9, were formed as a result of decomposition. Water, methanol, and ethanol added across
the GedC double bond of 1 to give vinylalkoxy (hydroxy) germanes. Benzophenone did not
react with 1 at 0 °C, but benzaldehyde gave oxagermetane 13 in good yield. When acetone
was introduced to 1, it gave the unexpected product 10, the water adduct.
Sch em e 1
In tr od u ction
In the last six years, much has been accomplished in
the synthesis of stable group 14 heteronuclear allene
analogues. A stannaketenimine1 was synthesized by
Gru¨tzmacher in 1992, but did not give trapping reaction
characteristics of heavy alkenes. The following year we
prepared a 1-silapropadiene,2 but this molecule revealed
very little in terms of reactivity because of the severe
steric restraints put on it by large substituents. In 1997,
other less sterically hindered 1-silapropadienes3 were
made that gave us insight into the reactivity of this
moiety. With the recent synthesis of a stable 1-germa-
phosphaallene4 and a trapping product of a 1-germapro-
padiene with chalcogens,5 our focus shifted to the
synthesis of a stable 1-germapropadiene.
Resu lts a n d Discu ssion
Utilizing the salt-elimination method following a
facile synthesis of a phenylethynylfluorogermane, 2, we
synthesized and characterized a stable 1-germapropa-
diene, 1 (Scheme 1).6 An exactly analogous lithium
fluoride elimination was employed earlier to synthesize
the isostructural silicon analogue, 4.3 In the 1-silapro-
padiene synthesis, the intermediate lithium compound
was stable in solution up to 0° C, but the corresponding
germanium intermediate 3 eliminated LiF rapidly even
at -75 °C. This contrasting behavior may reflect the
difference in bond strengths, the Si-F bond being
stronger than Ge-F. Recently the synthesis and crystal
structure of a second example of a 1-germapropadiene
have been reported.7
Decom p osition . Thermolysis of 1-silapropadiene 4
at 130 °C in a C6D6 solution3 led to a C-H insertion
into an ortho isopropyl group to form silacyclobutane 5
(eq 1). 1-Silapropadiene 6, which lacks a tertiary C-H
In this paper we report several chemical reactions of
1 and compare them with those of the silicon analogue
4. Differences between these two molecules are revealed
in reactions with alcohols, ketones, and aldehydes, as
well as in their modes of decomposition.
bond, decomposed at 90 °C in Et2O by SidC insertion
into one of the tert-butyl C-H bonds, forming five-
membered ring 7 (eq 2). In both of these reactions, only
one product was formed. Under much less vigorous
conditions, above 0 °C in solution or above 90 °C in the
solid state, 1 undergoes both reactions, giving com-
pounds 8 and 9 in a ratio of 60:40. It has become evident
that this type of C-H insertion cyclization reaction is
a significant decomposition route for kinetically sta-
blized group 14 multiple bonds8 as well as for a germyl-
ene.9 The formation of these rings emphasizes the
(1) Gru¨tzmacher, H.; Freitag, S.; Herbst-Irmer, R.; Sheldrick, G. S.
Angew. Chem., Int. Ed. Engl. 1992, 31, 437.
(2) Miracle, G. E.; Ball, J . L.; Powell, D. R.; West, R. J . Am. Chem.
Soc. 1993, 115, 11598.
(3) Trommer, M.; Miracle, G. E.; Eichler, B. E.; Powell, D. R.; West,
R. Organometallics 1997, 16, 5737.
(4) Ramdane, H.; Ranaivonjatovo, H.; Escudie´, J .; Mathieu, S.;
Knouzi, N. Organometallics 1996, 15, 3070.
(5) Kishikawa, K.; Tokitoh, N.; Okazaki, R. Organometallics 1997,
16, 5127.
(6) Eichler, B. E.; Powell, D. R.; West, R. Organometallics 1998, 17,
2147.
(7) Tokitoh, N.; Kishikawa, K.; Okazaki, R. Chem. Lett. 1998, 811.
10.1021/om980555r CCC: $18.00 © 1999 American Chemical Society
Publication on Web 01/21/1999

Reactivity of a 1-Germapropadiene
Organometallics, Vol. 18, No. 4, 1999 541
instability of heteronuclear multiple bonds. Under even
mild conditions (as for 1), the germanium-carbon
double bond forms strained four- and five-membered
rings rather than remaining as a double bond.
Compounds 8 and 9 were synthesized by simply
warming 1 to room temperature overnight in diethyl
ether or hexane (eq 3) and separating them by flash
F igu r e 1. Molecular structure of germacyclobutane, 8.
Thermal ellipsoid (50% probability level) drawing with
hydrogen atoms omitted for clarity. Selected bond lengths
(Å) and angles (deg): Ge-C(1) 1.951(3), Ge-C(13) 1.993-
(3), Ge-C(19) 2.015(3), Ge-C(28) 1.983(3), C(13)-C(14)
1.403(4), C(14)-C(19) 1.516(4), C(1)-C(2) 1.339(4); Ge-
C(1)-C(2) 138.0(3), C(1)-Ge-C(28) 113.68(12), C(1)-Ge-
C(19) 107.92(13), C(1)-Ge-C(13) 113.37(12), C(19)-Ge-
C(28) 114.45(12), C(13)-Ge-C(28) 126.13(12), C(13)-Ge-
C(19) 73.17(12), Ge-C(13)-C(14) 90.2(2), Ge-C(19)-C(14)
86.3.
triisopropylphenyl group in the 70-80% intensity range.
1
In the H NMR of 9 the vinyl proton is evident at +6.36
ppm. The resonance at 1.59 ppm in 9 is assigned to the
methyl group on the five-membered ring, by analogy
with the 1.49 ppm resonance in 8. The 1.59 ppm reso-
nance appears as a singlet; for some reason, the coupling
with the adjacent C-H proton must be very small.
Rea ction s w ith Wa ter a n d Alcoh ols. In the syn-
thesis of 4, the R-lithiofluorosilane was stable up to 0
°C, so we initially assumed the same would be true for
3. In an endeavor to trap the R-lithiofluorogermane 3,
we added methanol as a mild protic reagent. This would
replace the lithium with a hydrogen, giving an air- and
moisture-stable product that was still a fluorogermane.
Methanol was syringed into a solution of 2 and tert-
butyllithium in ether at -78 °C, and the reaction
product was purified by bulb-to-bulb distillation. The
resulting oil was washed with hot methanol, yielding a
white solid, 11, the formal methanol trapping product
of the 1-germapropadiene 1. Compound 11 was char-
column chromatography. Compound 8 was character-
ized by single-crystal X-ray diffraction (Figure 1).
There are two slightly different molecules (Z ) 4) in
the unit cell of 8. In the two molecules, the four-
membered ring of 8 is folded to an angle of 7.3° and 9.6°
between the planes of Ge-C(19)-C(14) and Ge-C(13)-
C(14). The Ge-C(13) bond lengths are 1.993 and 1.979
Å, and the Ge-C(19) bond lengths are 2.015 and 2.035
Å. It is evident that the four-membered ring of 8 is very
strained, since the C(13)-Ge-C(19) bond angle (73.2
°) is very small compared to the ideal value of 90°. A
large residual peak in the final difference map was
located about 1 Å from Ge(1A), which is believed due to
a small amount of twinning in the crystal. One isopropyl
group was disordered and modeled in two orientations.
The occupancies of atoms C(22B)-C(24B) and C(22′′)-
C(24′′) refined to 0.483(12) and 0.517(12).
Compound 9 did not provide crystals of sufficient
quality for X-ray analysis. The structure of 9 is tenta-
tively assigned on the basis of similarities of the 1H and
13C NMR spectra and mass spectra of 8 and 9. The mass
spectrum of 9 is almost identical to that of 8. Both
compounds show M+ at m/z ) 638, loss of a tert-butyl
group as the 100% peak (m/z ) 581), and loss of a
1
acterized by H and 13C NMR, mass spectroscopy, and
single-crystal X-ray crystallography (Figure 2). There
were two slightly different molecules in the unit cell of
11, but the differences were not extraordinary. The
Ge-O bonds were similar in both molecules [Ge(1A)-
O(1A) ) 1.812(3) Å and Ge(1B)-O(1B) ) 1.822(4) Å],
but the Ge-C(1) bonds were different by over 0.03 Å
[Ge(1A)-C(1A) ) 1.970(5) Å and Ge(1B)-C(1B) )
1.936(5) Å]. The O-Ge-C(1) bond angles were also
slightly different [O-Ge-C(1A) ) 111.2(2)° and O-Ge-
C(1B) ) 109.1(2)°]. A large residual peak in the final
difference map was located about 1 Å from Ge(1B). This
peak is believed to be due to a small amount of twinning
in the crystal. Two isopropyl groups were disordered and
both modeled in two orientations. The occupancies of
atoms C(37A)-C(39A) and C(37′)-C(39′) refined to 0.43-
(8) (a) Baines, K. M.; Groh, R. J .; Babu, J .; Parshotam, U. R.
Organometallics 1998, 11, 2176. (b) Weidenbruch, M.; Schafers, K.;
Schlaefke, J .; Peters, K.; von Schnering, H. G. J . Organomet. Chem.
1991, 415, 343.
(9) J utzi, P.; Schmidt, H.; Neumann, B.; Stammler, H.-G. Organo-
metallics 1996, 15, 741.

542 Organometallics, Vol. 18, No. 4, 1999
Eichler et al.
F igu r e 3. Molecular structure of methoxygermane, 11.
Thermal ellipsoid (50% probability level) drawing with
hydrogen atoms omitted for clarity. Selected bond lengths
(Å) and angles (deg): Ge-C(1) 1.970(5), Ge-O 1.812(3),
Ge-C(13) 1.994(4), Ge-C(28) 2.005(5), O-C(43) 1.424(6),
C(1)-C(2) 1.340(6); O-Ge-C(1) 111.2(2), O-Ge-C(13)
105.4(2), O-Ge-C(28) 111.6(2), Ge-O-C(43) 119.2(3),
C(1)-Ge-C(13) 118.1(2), C(1)-Ge-C(28) 100.7(2), C(13)-
Ge-C(28) 109.9(2), Ge-C(1)-C(2) 133.4(4).
F igu r e 2. Molecular structure of hydroxygermane, 10.
Thermal ellipsoid (50% probability level) drawing with
hydrogen atoms omitted for clarity. Selected bond lengths
(Å) and angles (deg): Ge-C(1) 1.952(2), Ge-O 1.7879(13),
Ge-C(13) 1.979(2), Ge-C(28) 1.987(2), C(1)-C(2) 1.343-
(3); Ge-C(1)-C(2) 132.20(14), O-Ge-C(1) 110.22(7),
O-Ge-C(13) 101.27(7), O-Ge-C(28) 114.26, C(13)-Ge-
C(28) 109.99(7).
(3) and 0.57(3). The occupancies of atoms C(37B)-
C(39B) and C(37′′)-C(39′′) refined to 0.721(12) and
0.279(12).
We thought that this result could have originated
from the hot methanol wash of the proposed fluoroger-
mane, so we decided to use the same procedure with
ethanol as the trapping agent. If this experiment led
again to compound 11, it would mean that we had
replaced the fluoride with a methoxy group when it was
exposed to hot methanol. Conversely, if the experiment
resulted in compound 12, the formal ethanol trapping
product of 1, it would be clear that we were trapping 1
and not 3. In fact, when ethanol was added to the
reaction solution at -78 °C, the product was the ethanol
adduct 12, which was also studied by X-ray crystal-
lography (Figure 3). The isopropyl group C(22)-C(24)
was disordered and modeled in two orientations with
refined occupancies of 0.322(12) for the unprimed atoms
and 0.678(12) for the primed atoms.
As our syntheses continued, it became clear that
water was a fast, efficient trapping reagent that could
be utilized for gas chromatographic studies to verify that
the 1-germapropadiene 1 was still in solution. In a
similar manner, water was added to the reaction solu-
tion at -78 °C, yielding the water adduct of the
germapropadiene, 10 (eq 4). The latter was also inves-
tigated by X-ray crystallography (Figure 4).
F igu r e 4. Molecular structure of ethoxygermane, 12.
Thermal ellipsoid (50% probability level) drawing with
hydrogen atoms omitted for clarity. Selected bond lengths
(Å) and angles (deg): Ge-C(1) 1.958(2), Ge-O 1.7850(12),
Ge-C(13) 1.985(2), Ge-C(28) 1.982(2), O-C(43) 1.426(2),
C(1)-C(2) 1.331(2); O-Ge-C(1) 110.77(7), O-Ge-C(13)
105.27(7), O-Ge-C(28) 110.22(6), Ge-O-C(43) 119.09(11),
O-C(43)-C(44) 108.8(2), C(1)-Ge-C(13) 114.50(7), C(1)-
Ge-C(28) 106.53(7), C(13)-Ge-C(28) 109.58(7), Ge-C(1)-
C(2) 131.1(2).
Rea ction s w ith Ca r bon yl Com p ou n d s. Germenes
can react with carbonyl groups by 2+2 cycloaddition (eq
5) to form 1,2-oxagermetanes.10 To find out if 1 behaves
in a similar manner, we first treated it with benzophe-
none. No reaction occurred at 0 °C even after 3 days.
The 1-silapropadiene 4 did react with benzophenone to
form a 1,2-oxasiletane, but only when reacted at room
temperature for 8 h.
It is interesting that the Ge-C(1)-C(2) bond angles
(10 ) 132.2°, 11 ) 133.4°, 12 ) 131.1°) are considerably
greater than the 120° value for sp2-hybridized carbons.
Steric factors evidently force the CdC(t-Bu)Ph fragment
away from the larger Tip groups.
(10) (a) Lazraq, M.; Couret, C.; Escudie´, J .; Satge´, J .; Drager, M.
1991, 10, 1771. (b) Wiberg, N.; Kim, C. K. Chem. Ber. 1986, 119, 2980.

Reactivity of a 1-Germapropadiene
Organometallics, Vol. 18, No. 4, 1999 543
Realizing that benzophenone was probably too hin-
dered to react with 1 at 0 °C, we next tried the reaction
with benzaldehyde. An overnight reaction of 1 with
benzaldehyde at 0 °C gave the desired 2+2 cycloaddition
product 13 (eq 5). This is the first example of a
1,2-oxagermetane with an exocyclic double bond. Com-
pound 13 was studied by single-crystal X-ray diffraction
(Figure 5), which revealed the angle between the planes
of Ge-C(1)-C(43) and Ge-C(1)-O to be 9.8°. It is of
note that the O-Ge-C(1) bond angle is only 74.1°. One
isopropyl group was disordered and modeled in two
orientations with occupancies of 0.666(9) and 0.334(9)
for C(38), C(39) and C(38′), C(39′), respectively.
Oxagermetanes that are not very sterically hindered
typically decompose by cleavage of the Ge-C and O-C
bonds of the ring, producing a germanone and an
alkene.11 Compound 13 shows no sign of this mode of
decomposition to the germanone and the allene (eq 6)
up to 135 °C, but the 100% intensity peak for the mass
spectrum corresponds to the allene fragment.
F igu r e 5. Molecular structure of 1,2-oxagermetane, 13.
Thermal ellipsoid (50% probability level) drawing with
hydrogen atoms omitted for clarity. Selected bond lengths
(Å) and angles (deg): Ge-C(1) 1.970(3), Ge-O 1.843(2),
Ge-C(13) 1.975(3), Ge-C(28) 1.971(3), C(1)-C(2) 1.348-
(4), C(1)-C(43) 1.545(4), O-C(43) 1.454(4); O-Ge-C(1)
74.10(11), Ge-O-C(43) 96.48(17), O-C(43)-C(1) 100.1(2),
C(43)-C(1)-Ge 88.5(2), Ge-C(1)-C(2) 134.1(2), C(2)-
C(1)-C(43) 132.9(3), C(13)-Ge-C(28) 112.64(14), O-Ge-
C(28) 105.46(13), O-Ge-C(13) 110.54(12), C(1)-Ge-C(13)
119.74(14), C(1)-Ge-C(28) 123.99(14), C(1)-C(2)-C(3)
118.4(3), C(1)-C(2)-C(9) 125.4(3), C(3)-C(2)-C(9) 116.1-
(3).
Sch em e 2
Compared to compounds 8, 10, 11, and 12, which have
more freedom of rotation around the Ge-C(1) bond, the
four-membered ring of the 1,2-oxagermetane locks 13
into a rigid conformation, as evidenced by the complex-
ity of 1H and 13C NMR spectra. Compounds 10-12
typically show the hydrogen atom on the tertiary
carbons of the isopropyl groups on the Tip ligands in a
ratio of 4:2 (ortho:para). In contrast, the 1H NMR
spectrum of compound 13 shows six separate inequiva-
lent signals for the six isopropyl hydrogens. This is also
revealed in the many doublets for the isopropyl methyl
groups of the Tip ligands compared to compounds 10-
12. The 13C NMR spectrum is also much more complex
than the spectra of compounds 10-12. The 13C NMR
peak for C(43) is easily identifiable at +85.79 ppm, well
downfield of the other aliphatic carbons.
The reaction of 1 with acetone was also investigated.
Addition of carefully dried acetone to the reaction
solution at -78 °C led not to a carbonyl adduct of 1,
but to the water adduct 10. The latter could arise by
initial formation of a germyl enol ether,10a followed by
hydrolysis during the workup, as shown in Scheme 2.
However, the 1H and 13C NMR of the solution before
workup showed no evidence of a germyl enol ether;
instead the NMR spectra appeared identical to that of
10. Acetone can dimerize to form diacetone alcohol,
which can decompose to mesityl oxide and water. Thus
it seems likely that 1 may serve to dehydrate acetone
directly.
Con clu sion s
Germapropadiene 1 follows the reactivity pattern of
the analogous silapropadiene 4, but with a few signifi-
cant differences. Both heteropropadienes add alcohols
across the MdC double bond in a similar manner.
Because of the instability of 1, it did not react with
benzophenone as 4 did (to form a 1,2-oxasiletane). The
less bulky carbonyl compound benzaldehyde however
added to the germapropadiene to form a 1,2-oxagerme-
tane. The most pronounced differences between the two
analogues lie in their stabilities and modes of decom-
position. Compound 1 survives only to 0 °C in solution,
whereas compound 4 is much more stable, decomposing
only at 130 °C. The silapropadiene decomposes to a
single product, a silacyclobutane (5), but the germapro-
padiene rearranges to two products, a germacyclobutane
(8) and a germacyclopentane (9).
(11) Satge´, J . Adv. Organomet. Chem. 1982, 21, 241.

544 Organometallics, Vol. 18, No. 4, 1999
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p ou n d s 8 a n d 10-13
Eichler et al.
8
10
11
12
13
formula
fw
C
42H60GeO
C42H62GeO
655.51
0.35 × 0.35 × 0.25
31.267(2)
12.3157(6)
22.6568(11)
90
113.9091(7)
90
monoclinic
C2/c
C43H64GeO
669.53
C44H66GeO
683.56
0.60 × 0.20 × 0.10
33.6377(7)
47.2748(2)
10.4827(3)
90
C49H66GeO
743.61
637.49
cryst size (mm3)
a (Å)
0.38 × 0.34 × 0.30
12.6624(7)
17.2347(12)
17.8359
84.572(3)
87.898(4)
79.855(2)
triclinic
P1h
0.36 × 0.18 × 0.14
9.6460(9)
11.8734(8)
38.0722(4)
84.459(4)
87.213(4)
69.440(4)
triclinic
P1h
0.35 × 0.35 × 0.02
20.9235(12)
10.8125(6)
19.2080(9)
90
91.876(2)
90
monoclinic
P21/c
4343.2(4)
1.137
b (Å)
c (Å)
R (deg)
â (deg)
90
90
γ (deg)
cryst syst
space group
vol (Å3)
orthorhombic
Fdd2
16669.8(6)
1.089
3813.5(4)
1.110
7975.9(7)
1.092
4063.1(5)
1.095
Dcalcd (gcm-3
)
Z
4
8
4
16
0.710 73
133(2)
4
wavelength (Å)
temp (K)
0.710 73
133(2)
0.829
semiempirical
0.813/0.956
42 178
18 394
12 036
797
0.710 73
133(2)
0.796
semiempirical
0.734/0.831
19 062
9611
7129
397
0.710 73
133(2)
0.782
semiempirical
0.678/0.962
35 860
13 932
8809
855
0.710 73
133(2)
0.738
empirical
0.7821/0.9854
16 591
7537
4918
479
abs coeff (mm-1
abs correction
min/max trans
)
0.764
semiempirical
0.576/0.746
20 266
7843
6733
no. of reflns collected
no. of indep reflns
no. of obsd reflns
no. of params
455
restraints
94
3.0-25.0
1.014
2.671
-0.757
0.0586
0
92
3.0-25.0
1.015
3.161
-1.392
0.0694
101(disorder)
3.0-25.0
0.918
0.373
-0.278
0.0252
32(disorder)
2.36-25.00
0.912
0.672
-0.529
0.0510
q range (deg)
3.0-25.0
0.984
0.578
-0.410
0.0367
Goof on F2
largst diff peak (e Å-3
)
)
largst diff hole (e Å-3
R1 (%)
wR2 (%)
largest & mean D/esd
0.1506
-0.005/0.000
0.0954
-0.001/0.000
0.1812
-0.001/0.000
0.0489
-0.002/0.000
0.1237
0.006/0.000
was slowly allowed to warm from 0 °C to room temperature
overnight. Reaction yields were analyzed by gas chromatog-
raphy, which showed that compounds 8 and 9 were present
in a ratio of 3:2, with only traces of other products. The solvent
was removed in vacuo, and the compounds were separated by
flash column chromatography (silica gel, hexane/diethyl ether
(99.5:0.5)). Removal of solvent by rotary evaporation gave 8
as a solid (crude yield ) 0.33 g, 31%). This was recrystallized
once from a 2-methoxyethanol/diethyl ether mixture to give
0.24 g of crystals of 8 (0.38 mmol, 23%). Mp (2-methoxyetha-
Exp er im en ta l Section
1H and 13C NMR spectra were recorded on a Bruker AC-
300 spectrometer. Chemical shifts are given relative to exter-
nal standards (1H and 13C, tetramethylsilane). All 13C spectra
were 1H decoupled. High-resolution electron-impact ionization
mass spectrometry was performed on an MS80 Kratos spec-
trometer. Elemental analyses were carried out at INEOS,
Russian Academy of Sciences, Moscow. X-ray crystal structure
determinations were performed on a Siemens P4 diffractome-
ter equipped with a CCD area detector, using Mo KR radiation.
The structures of all compounds were solved by direct methods
and refined by full-matrix least-squares refinement with
anisotropic displacement parameters. Hydrogen atoms in all
models were refined using a riding model with isotropic
displacement parameters. Details of the data collection and
refinement are given in Table 1.
1
nol): 150 °C. H NMR (300 MHz, CDCl3): δ 1.02-1.03 (br m,
6 H), 1.12 (s, 12 H), 1.23 (d, 3 H, J ) 6.4 Hz), 1.24 (d, 3 H, J
) 6.8 Hz), 1.26 (d, 6 H, J ) 6.8 Hz), 1.30 (d, 9 H, J ) 6.6 Hz),
1.37 (d, 3 H, J ) 6.8 Hz), 1.49 (s, 3 H), 2.86 (sept., 2 H, J ) 7.0
Hz), 3.11-3.24 (m, 3 H), 5.82 (s, 1 H), 6.73 (d, 1 H, J ) 1.2
Hz), 6.98 (s, 2 H), 7.04-7.07 (m, 3 H), 7.18-7.24 (m, 3 H). 13
C
NMR (75.3 MHz, CDCl3): δ 22.8, 23.7, 23.91, 23.95, 24.1, 24.2,
25.2, 26.3, 26.9, 28.0, 30.6, 33.3, 34.0, 34.5, 37.8, 39.5, 117.1,
121.2, 122.4, 125.7, 125.9, 127.1, 128.6, 136.2, 142.3, 147.0,
All reactions were carried out under an atmosphere of dry
argon in flame- or oven-dried glassware. Bis(2,4,6-triisopro-
pylphenyl)phenylethynylfluorogermane (2) and 1,1-bis(2,4,6-
triisopropylphenyl)-3-tert-butyl-3-phenyl-1-germa-1,2-propa-
diene (1) were prepared as described in the literature.6 Diethyl
ether was distilled from sodium/benzophenone prior to use.
Acetone was dried by refluxing over anhydrous CaSO4 over-
night and distilling onto 4 Å molecular sieves. Methanol and
ethanol were refluxed overnight with Mg and I2 and distilled
the next day. Benzophenone, benzaldehyde, and t-BuLi were
used as received.
F or m a tion of Ger m a p r op a d ien e 1 a t -75 °C. A solution
of 2 (0.10 g, 0.17 mmol) in 0.7 mL of dry diethyl ether was
prepared in an NMR tube sealed with a septum and cooled to
-75 °C. The 13C NMR spectrum was that previously recorded
for 2.6 A solution of tert-butyllithium (1.7 M in pentane, 0.10
mL, 0.170 mmol) was added at -75°, leading to immediate
formation of an orange-red color, characteristic for 1. The 13C
NMR spectrum was identical to that of 1.
149.3, 150.8, 151.9, 152.9, 161.8, 164.5. Anal. Calcd for C42H60
-
Ge: C, 79.13; H, 9.49; Ge, 11.39. Found: C, 79.20; H, 9.48;
Ge, 11.16. MS[EI] [m/z(Irel)]: 638 [7.3, M+], 581 [100, - t-Bu],
434 [74.0, - Tip and H].
1-(2,4,6-Tr iisop r op ylp h en yl)-4,6-(d iisop r op ylp h en yl)-
1-(2-p h en yl-3,3-d im et h ylb u t -1-en yl)-3-m et h ylger m a cy-
clop en t a n e (9). Compound 9 (larger Rf value than 8) was
isolated from the same reaction mixture as 8 during flash
column chromatography (crude yield ) 0.20 g, 0.31 mmol,
19%). This was recrystallized from a 2-methoxyethanol/diethyl
ether mixture, yielding 0.14 g (0.22 mmol, 13%) of 9 as a white
solid. Mp (2-methoxyethanol): 133 °C. 1H NMR (300 MHz,
CDCl3): δ 0.95-0.98 (m, 3 H), 1.00 (br s, 12 H), 1.07 (d, 6 H,
J ) 5.3 Hz), 1.17 (d, 3 H, J ) 6.8 Hz), 1.22-1.29 (m, 18 H),
1.59 (s, 3 H), 2.61 (sept., 1 H, J ) 6.8 Hz), 2.70 (sept., 2 H, J
) 6.6 Hz), 2.84 (sept., 1 H, J ) 6.8 Hz), 2.85 (sept., 1 H, J )
6.8 Hz), 6.36 (s, 1 H), 6.68 (d, 2 H, J ) 7.2 Hz), 6.73 (d, 1 H,
J ) 1.3 Hz), 6.83 (s, 2 H), 6.88 (t, 2 H, J ) 7.5 Hz), 6.96 (d, 1
H, J ) 1.3 Hz), 7.05 (t, 1 H, J ) 7.4 Hz). 13C NMR (75.3 MHz,
CDCl3): δ 23.1, 24.0, 24.2, 25.4, 26.4, 26.7, 27.7, 29.6, 33.1,
1-(2,4,6-Tr iisop r op ylp h en yl)-4,6-(d iisop r op ylp h en yl)-
1-(2-p h en yl-3,3-d im eth ylbu t-1-en yl)-2,2-d im eth ylger m a -
cyclobu ta n e (8). A solution of 1 (1.00 g, 1.67 mmol) in diethyl
ether was prepared as described in the literature.6 The solution

Reactivity of a 1-Germapropadiene
Organometallics, Vol. 18, No. 4, 1999 545
34.1, 34.2, 34.6, 38.3, 39.1, 117.0, 120.5, 122.3, 123.9, 126.1,
126.4, 129.4, 135.5, 141.6, 142.4, 149.1, 150.7, 151.7, 153.0,
161.8, 164.7. Anal. Calcd for C42H60Ge: C, 79.13; H, 9.49.
Found: C, 78.95; H, 9.66. MS[EI] [m/z(Irel)]: 638 [9.7, M+], 581
[100, - t-Bu], 434 [79.1, - Tip and H].
10 equiv). The solution was warmed to room temperature
overnight and worked up in the same manner as 10 (method
A), yielding 12 as a colorless oil. The oil was recrystallized
once from hot methanol and once from 2-methoxyethanol/
diethyl ether to give colorless crystals of 12 (0.59 g, 0.86 mmol,
51%). Mp: 110 °C. 1H NMR (300 MHz, CDCl3): δ 0.56 (t, 3 H,
J ) 6.8 Hz), 0.91 (d, 12 H, J ) 6.5 Hz), 0.94 (d, 12 H, J ) 6.5
Hz), 1.07 (s, 9 H), 1.18 (d, 12 H, J ) 6.8 Hz), 2.68 (q, 2 H, J )
7.0 Hz), 2.80 (sept., 2 H, J ) 6.8 Hz), 3.40 (m, 4 H), 6.25 (s, 1
H), 6.89 (s, 4 H), 7.15-7.17 (m, 2 H), 7.25-7.27 (m, 3 H). 13C
NMR (75.3 MHz, CDCl3): δ 18.2, 23.87, 23.91, 24.2, 24.5, 29.9,
32.9, 34.1, 38.8, 59.4, 121.7, 125.8, 126.1, 126.7, 129.4, 135.1,
141.8, 149.4, 153.7, 161.7. Anal. Calcd for C44H66GeO: C, 77.31;
H, 9.73; Ge, 10.62. Found: C, 77.56; H, 9.53; Ge, 10.68. MS-
[EI] [m/z(Irel)]: 638 [9.7, - EtOH], 581 [26.7, - EtOH and
t-Bu], 480 [62.7, - Tip and H], 434 [100, - EtOH, H and Tip].
2,2-Bis(2,4,6-tr iisopr opylph en yl)-3-(3,3-dim eth yl-2-ph en -
ylbu t-1-ylid en e)-4-p h en yl-1,2-oxa ger m eta n e (13). To a
deep red ethereal solution of 1 (1.00 g, 1.67 mmol) at -78 °C
was added dry benzaldehyde (0.34 mL, 3.3 mmol, 2.0 equiv),
turning the solution orange. The solution was left at 0 °C
overnight. The solvents were removed in vacuo, and the solid
was purified by flash column chromatography (silica gel,
hexane/diethyl ether (99.5:0.5)). Removal of solvent by rotary
evaporation gave 13 as a solid (crude yield ) 0.92 g, 74%).
The solid was recrystallized once from a hot 2-methoxyethanol/
diethyl ether mixture to give colorless crystals of 13 (0.73 g,
1,1-Bis(2,4,6-tr iisopr opylph en yl)h ydr oxyger m yl-2-ph en -
yl-3,3-d im eth ylbu t-1-en e (10). Meth od A. To a deep red
ethereal solution of 1 (1.01 g, 1.68 mmol) at -78 °C was added
water (0.20 mL, 11.1 mmol, 6.6 equiv), decolorizing the solution
immediately. The solution was warmed to room temperature
overnight. The solvents were removed in vacuo, and the solid
was taken up in diethyl ether and washed with water. The
organic layer was dried with MgSO4 and gravity filtered, and
the ether was removed by rotary evaporation. Bulb-to-bulb
distillation (195-210 °C/0.02 Torr) gave 10 as a colorless oil
(crude yield ) 0.77 g, 71%). The oil was recrystallized once
from 2-methoxyethanol/diethyl ether solution giving colorless
crystals of 10 (0.57 g, 0.89 mmol, 53%).
Meth od B. To a deep red ethereal solution of 1 (1.00 g, 1.67
mmol) at -78 °C was added dry acetone (0.25 mL, 3.4 mmol,
2.0 equiv), decolorizing the solution immediately. The solution
was warmed to room temperature overnight. A workup
procedure analogous to that of method A gave 10 as a colorless
oil. The oil was recrystallized once from hot methanol and then
once from a hot 2-methoxyethanol/diethyl ether solution, giving
colorless crystals of 10 (0.66 g, 1.01 mmol, 60%). Mp (2-
methoxyethanol): 138 °C. 1H NMR (300 MHz, CDCl3): δ 0.97
(d, 12 H, J ) 6.6 Hz), 1.01 (d, 12 H, J ) 6.8 Hz), 1.11 (s, 9 H),
1.18 (d, 12 H, J ) 7.0 Hz), 2.80 (sept., 2 H, J ) 7.0 Hz), 3.42
(sept., 4 H, J ) 6.8 Hz), 6.31 (s, 1 H), 6.92 (s, 4 H), 7.18-7.20
(m, 2 H), 7.31-7.34 (m, 3 H). 13C NMR (75.3 MHz, CDCl3): δ
23.9, 24.4, 24.6, 29.5, 33.0, 34.2, 38.6, 121.6, 126.1, 127.3, 127.8,
1
0.98 mmol, 59%). Mp: 134 °C. H NMR (300 MHz, CDCl3): δ
0.13 (d, 3 H, J ) 6.3 Hz), 0.53 (d, 3 H, J ) 7.2 Hz), 0.56 (d, 3
H, J ) 7.0 Hz), 0.85 (d, 3 H, J ) 6.4 Hz), 0.95 (s, 9 H), 1.00 (d,
3 H, J ) 6.4 Hz), 1.18 (d, 3 H, J ) 7.0 Hz), 1.19 (d, 3 H, J )
6.8 Hz), 1.25 (d, 6 H, J ) 7.0 Hz), 1.27 (d, 3 H, J ) 6.4 Hz),
1.47 (d, 3 H, J ) 6.6 Hz), 1.50 (d, 3 H, J ) 6.8 Hz), 1.94 (sept.,
1 H, J ) 6.6 Hz), 2.60 (sept., 1 H, J ) 6.4 Hz), 2.65 (sept., 1 H,
J ) 6.8 Hz), 2.83 (sept., 1 H, J ) 7.0 Hz), 2.85 (sept., 1 H, J )
7.0 Hz), 4.46 (sept., 1 H, J ) 6.6 Hz), 6.49 (s, 1 H), 6.74-6.91
(m, 5 H), 7.09-7.13 (m, 7 H), 7.39-7.42 (m, 2 H). 13C NMR
(75.3 MHz, CDCl3): δ 22.9, 23.2, 23.9, 24.0, 25.2, 25.4, 25.54,
25.57, 25.7, 30.8, 31.4, 34.0, 34.17, 34.21, 35.3, 36.3, 38.5, 85.8,
121.50, 121.54, 122.19, 122.24, 126.3, 126.7, 127.8, 128.8,
136.8, 139.5, 143.2, 145.2, 150.2, 150.5, 150.6, 153.4, 153.9,
154.1, 154.2, 155.2. Anal. Calcd for C49H66GeO: C, 79.10; H,
8.95; Ge, 9.76. Found: C, 78.88; H, 8.90; Ge, 9.93. MS[EI]
[m/z(Irel)]: 744 [5.9, M+], 729 [9.9, - Me], 638 [14.4, - Ph(H)-
CO], 581 [22.8, - Ph(H)CO, - t-Bu], 497 [100, - PhCCdC(t-
Bu)Ph].
129.2, 136.5, 141.5, 149.4, 153.1, 161.5. Anal. Calcd for C42H62
-
GeO: C, 76.95; H, 9.53; Ge, 11.07. Found: C, 76.70; H, 9.53;
Ge, 10.84. MS[EI] [m/z(Irel)]: 638 [3.5, - H2O], 581 [14.6, -
H2O and t-Bu], 452 [88.9, - Tip and H], 434 [100, - H2O, H
and Tip].
1,1-Bis (2,4,6-t r iisop r op ylp h en yl)m et h oxyger m yl-2-
p h en yl-3,3-d im eth ylbu t-1-en e (11). To a solution of 1 (0.50
g, 0.83 mmol) at -78 °C was added dry methanol (0.50 mL,
12.5 mmol, 15 equiv), decolorizing the solution immediately.
The solution was warmed to room temperature overnight. A
workup procedure analogous to that of 10 (method A) gave 11
as a colorless oil. The oil was recrystallized once from hot
methanol and 2-methoxyethanol twice, giving colorless needles
of 11 (0.12 g, 0.18 mmol, 22%). Mp (2-methoxyethanol): 108
1
°C. H NMR (300 MHz, CDCl3): δ 0.93 (d, 12 H, J ) 6.8 Hz),
0.95 (d, 12 H, J ) 6.6 Hz), 1.08 (s, 9 H), 1.18 (d, 12 H, J ) 7.0
Hz), 2.49 (s, 3 H), 2.80 (sept., 2 H, J ) 6.8 Hz), 3.41 (sept., 4
H, J ) 6.8 Hz), 6.23 (s, 1 H), 6.90 (s, 4 H), 7.16-7.19 (m, 2 H),
7.25-7.28 (m, 3 H). 13C NMR (75.3 MHz, CDCl3): δ 23.86,
23.92, 24.4, 29.9, 32.9, 34.1, 38.8, 52.8, 121.7, 125.9, 126.2,
Ack n ow led gm en t. The authors thank J arrod Buffy
for technical assistance, and the National Science
Foundation for a grant in support of this work.
126.6, 129.6, 134.9, 141.9, 149.5, 153.6. Anal. Calcd for C43H64
-
Su ppor tin g In for m ation Available: Tables giving atomic
coordinates, hydrogen coordinates, anisotropic displacement
parameters, bond lengths, bond angles, and torsion angles, and
figures of the unit cell diagram of 8, 10, 11, 12, and 13 (59
pages). Ordering information is given on any current masthead
page.
GeO: C, 77.13; H, 9.63; Ge, 10.84. Found: C, 76.70; H, 9.55;
Ge, 10.97. MS[EI] [m/z(Irel)]: 638 [9.8, - MeOH], 581 [35.0, -
MeOH and t-Bu], 466 [84.2, - Tip and H], 434 [100, - MeOH,
H and Tip].
1,1-Bis(2,4,6-tr iisop r op ylp h en yl)eth oxyger m yl-2-p h en -
yl-3,3-d im eth ylbu t-1-en e (12). To a solution of 1 (1.00 g, 1.67
mmol) at -78 °C was added dry ethanol (1.00 mL, 17.0 mmol,
OM980555R