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Crystalline -Radicals Containing Germanium.

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Crystalline n-Radicals Containing Germanium[**]
By Hartmut B. Stegmann, Klaus Scheffier,
and Fritz Stocker[*]
spectra and, further, are split by the protons and nitrogen
present in the molecule. Actually, with 390-fold increase in
spectrometer sensitivity, further HFS components that we
No success has previously attended attempts to prepare
paramagnetic organogermanium compounds by, in particular, dissociation of hexaaryldigermanesI’]. Hyperfine
structure that could be ascribed to magnetic coupling of a
free electron with 73Ge has never been found in ESR
studies of radical anions containing germanium”’ or of
Ge-substituted alkyl radicals13- ’I. We have, however,
now isolated paramagnetic compounds containing germanium as products of the reaction of 2-amino-4,6-ditert-butylphenoxyl ( I j with diarylgermanium dihalides.
Structure (4) is indicated by elemental analysis[61,mass
spectra, and chemical behavior.
The new compounds can also be prepared from the
corresponding tin171and lead compounds[81 when these
are treated with diarylgermanium halides.
Fig. 1. ESR spectrum of ( 4 a ) in benzene at room temperature.
ascribe to the 73Ge can be found both on the low-field
and on the high-field side of the main spectrum (Fig. 2).
Since the magnetic coupling with the 73Ge is relatively
small, each of the two lines furthest from the center are
single and correspond to the terms m73,e = +9/2 and
(51
/ 4 a ) , R=C,H,, m.p. 196°C;
141
( 4 6 ) , R=p-CH,C6H,, m.p. 241°C
The radicals ( 2 j to ( 4 ) are stable, so that they can be
isolated without special procedures. The diamagnetic
N-H heterocycles are formed on reduction by H,/Pt
and are at once oxidized by atmospheric oxygen back to
the radicals. Concentrated mineral acids degrade the
radicals. Elimination of the organometallic group affords
the phenoxazinyl radical (5)r91without loss of the paramagnetism being observed.
The radicals ( 4 a ) and ( 4 6 ) in ethanol or benzene afford
first a 15-line ESR signal. This hyperfine structure (HFS)
(Fig. 1) can be interpreted as due to magnetic coupling
of the free electron with two pairs of protons and the
14N nucleus.
HFS components that could be ascribed to Ge coupling
are to be expected only at increased sensitivity. In the
natural isotope mixture there is only one magnetic nucleus,
73Ge, in 7.6% amount. This isotope has nuclear spin
1=9/2, so that the ten Ge-HFS components can be
observed with very weak intensity only at the edges of the
Fig. 2. Left: high-field side of the ’3Ge isotope spectrum of ( 4 a ) in
benzene at room temperature. Right : simulated high-field isotope
spectrum.
-9/2. The remainder of the isotope spectrum is degraded.
The HFS found is in very good agreement with these
considerations, as the simulation[“’ (Fig. 2) of the spectrum
shows.
In accord with the other findings, the ESR spectrum
shows the new organogermanium derivatives to be
11,l I-disubstituted 1,3,7,9-tetra-tert-butyldibenzo[d,g][I,3,6,2]dioxagermanocin-5-yls.The coupling parameters are
[l] P. W: Selwood, J. Amer. Chem. SOC.61, 3168 (1939).
[ 2 ] A.L. Allred and L. W: Bush, J. Amer. Chem. SOC.90, 3352 (1968).
[3] A . Hudson and H . A . Hussain, J. Chem. SOC.B 1969, 793.
[4] P. J . Krusic and J a y K. Kochi, J. Amer. Chem. SOC. 91,6161 (1969).
[S] J . H . Mackey and D . E . Wood, Mol. Phys. 18, 783 (1970).
[6] We thank Dr. 7: Niedermeier, BASF, Ludwigshafen, for the ger-
manium determinations.
[ 7 ] H.B. Stegmann, K . Scheffler and F. Srocker, Chem. Ber. 103, 1279
[ * ] Priv.-Doz. Dr. H. B. Stegmann and F. Stocker
(1970).
Chemisches Institut der Universitat
74 Tiibingen, Wilhelmstr 33 (Germany)
Dr. K. Scheffler
Conseil Europeen pour la Recherche NuclCaire
CH-1211 Geneve-Meyrin (Switzerland)
[**I This work was supported by the Deutsche Forschungsgemeinschaft.
[ 8 ] H.B. Stegmann, K. Schemer, and F . Stocker, Angew. Chem. 82,
481 (1970);Angew. Chem. internat. Edit. 9. 456 (1970).
Angew. Chem. internat. Edit. 1 Vol. 10 (1971) 1 No. 7
[ 9 ] H.B. Sregmann, K. Schefler, F. Stocker, and H . Biirk. Chem. Ber.
101, 262 (1968); K . Scheffler and H.B. Stegmann. Tetrahedron Lett.
1968,3619.
[ l o ] The spectrum simulation was carried out on the CDC 3300 at
the Zentrum fur Datenverarbeitung, Universitat Tiibingen (Germany)
499
ascribed by US principally by analogy with the corresponding tin compoundsr71(Table 1).
As expected, the substituent R has only slight influence on
the coupling constants. The large line widths (ca. 700 mG)
may be ascribed to the unresolved proton HFS of the
On catalysis by HCI (14 days' stirring at 20°C), formic acid
(60% labeled by 13C; 0.50g, 10.8mmol) and thiophenol
(3.30 ml, 33.0 mmol) gavel6' a 72% yield of labeled tris(pheny1thio)methane; the NMR spectrum of its methine H
is shown in Fig. 1a : J13c-H= 168 Hz, 60% of 13C and
.
,C6H5
( C&),C-C(
Table 1. ESR data for the radicals 14) (gauss), measured in benzene at
room temperature; AH=line width.
(la)
14bl
aHl,a
iiHza
1.36
1.41
3.02
3.01
N'
6.13
6.27
3.02
3.44
2.002906
2.002978
C6H5-C,
C6H5
(1)
AH
a73r;e
C6H5)3
(2)
0.65
0.72
tert-butyl groups ; intramolecular movements are not the
cause of the line widening because the spectra are almost
unchanged between -70 and + 120°C.
Received: April 6,1971 {Z 419 i E j
German version: Angew. Chem. 83,538 (1971)
Homolysis of the Ethane C-C Bond: Detection of
Tris@henylthio)methyl by 3C-Labelingr*'1
By Dieter Seebach, Hartmut B. Stegmann, and
Albert K . Beck"]
Since the beginning of the century hexaphenylethane (I)
has been held to be the simplest ethane whose C-C bond
dissociates already at room temperature. However, it was
shown recently''] that the trityl radical (2)r21really dimerizes to (3)[31.We have reported[41that the persubstituted ethane ( 4 ) at slightly above 100°Caffords a radical that
is readily detected by ESR spectroscopy; we have assigned
the spectrum, which shows no hyperfine structure, to the
methyl ( 5 ) mainly on the basis of chemical findings: four
40% of 12Cmolecules. When heated with xylene, samples
of the labeled ethane (4) prepared from the methane[71gave
the ESR spectrum shown in Fig. lb[81.The relative intensities of the three lines (3:4: 3) correspond to a methyl radical
with 60% content of "C. The coupling constant a , 3c = 43.69
gauss is largelgl and so indicates that the lone electron is
only slightly delocalized over the three S atoms of the tris(pheny1thio)methyl.Since the appropriate a-o-parameters
are unknown it is not yet possible to determine the spin
density distribution exactly["! The spectrum cannot be
brought into accord with the paramagnetic molecule (71,
as is shown by a glance at the spectrum simulated["] for
this ethyl radical (Fig. 1c).
The question of how (6) is formed was solved by the following scrambling experiment :
unscrambled
mixture
scrambled
product
of the five products isolated in >95% yield after pyrolysis
of ( 4 ) are derived from the "half molecule"151;the fifth is
the ethylene (6) which could arise directly from the ethane
cia (7).
By using the ethane labeled by I3C on the central atoms we
can now answer the following questions:
1) Do we really observe the ESR spectrum of the methyl
(5)?
2) If so, is the ready dissociation of the ethane ( 4 ) caused
by stabilization of the methyl formed owing to delocalization of the unpaired electron over the three S atoms?
3) Is the ethylene (6) also formed after dissociation of the
ethane?
I
I
"
F
c
p
w
9
w
p] Doz. Dr. D. Seebach and A. K. Beck
Institut fur Organische Chernie der Universitat
75 Karlsruhe, Richard-Willstatter-Allee (Germany)
Doz. Dr. H. B. Stegmann
Chemisches Institut der Universitat
74 Tiibingen, Ludwigstrasse (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.
&m
8G
1-
I**]
Fig. 1. (a) 'H-NMR spectrum of labeled tris(pheny1thio)methane. (b)
ESR spectrum of labeled tris(pheny1thio)methyl. (c) Simulated ESR
spectrum of labeled pentakis(pheny1thio)ethyl.
500
Angew. Chem. internat. Edit. / Vol. 10 ( 1 9 7 1 ) 1 No. 7
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