Photochemical reactions of digermanyl-substituted naphthalenes: The germyl migration to the aromatic ring

Article abstract of DOI:10.1016/S0022-328X(97)00499-3

Photochemical reactions of digermanyl-substituted naphthalenes have been investigated by chemical studies using trapping agents, laser flash photolysis, and ab initio MO calculations. Irradiation of 1-(pentamethyldigermanyl)naphthalene (1) afforded mainly an isomer, 1-(dimethylgermyl)-8-(trimethylgermyl)naphthalene (4), via photochemical formation of a pair of trimethylgermyl radical and 1- naphthyldimethylgermyl radical, and then recombination at the 8-position of the latter followed by an intramolecular 1,4-hydrogen shift. At the same time a small amount of 1-(trimethylgermyl)naphthalene (5) was formed through the dimethylgermylene extrusion from 1. From photolysis of 2-(pentamethyldigermany)naphthalene a high molecular weight polymer was obtained. The excited states of digermanyl-substituted naphthalenes responsible for the photodecomposition are also discussed.

Full text of DOI:10.1016/S0022-328X(97)00499-3

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Journal of Organometallic Chemistry 553 1998 163–171
Photochemical reactions of digermanyl-substituted naphthalenes: The
germyl migration to the aromatic ring
a
b
b,c
Kunio Mochida a,), Hiroyuki Ginyama , Masae Takahashi , Mitsuo Kira
a
Department of Chemistry, Faculty of Science, Gakushuin UniÕersity, 1-5-1 Mejiro, Toshima-ku, Tokyo 171, Japan
Photodynamics Research Center, The Institute of Physical and Chemical Research Riken , 19-1399 Koeji, Nagamachi, Aoba-ku,
b
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)
Sendai 980, Japan
c
Department of Chemistry, Graduate School of Science, Tohoku UniÕersity, Aoba-ku, Sendai 980-77, Japan
Received 20 May 1997; received in revised form 5 August 1997
Abstract
Photochemical reactions of digermanyl-substituted naphthalenes have been investigated by chemical studies using trapping agents,
Ž .
Ž
.
laser flash photolysis, and ab initio MO calculations. Irradiation of 1- pentamethyldigermanyl naphthalene 1 afforded mainly an isomer,
Ž
.
Ž
.
Ž .
1- dimethylgermyl -8- trimethylgermyl naphthalene 4 , via photochemical formation of a pair of trimethylgermyl radical and 1-
naphthyldimethylgermyl radical, and then recombination at the 8-position of the latter followed by an intramolecular 1,4-hydrogen shift.
Ž
.
Ž .
At the same time a small amount of 1- trimethylgermyl naphthalene 5 was formed through the dimethylgermylene extrusion from 1.
Ž
.
From photolysis of 2- pentamethyldigermany naphthalene a high molecular weight polymer was obtained. The excited states of
digermanyl-substituted naphthalenes responsible for the photodecomposition are also discussed. q 1998 Elsevier Science S.A.
Keywords: Photolysis; Migration; Naphthylgermane; Laser photolysis; Germyl radical
1. Introduction
Recently, much attention has been focused on the photochemistry of aryl-substituted dimetals of group-14 elements
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.
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x
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.
E from both mechanistic and synthetic viewpoints 1–28 . In the photolysis of these s E–E -p conjugated
systems, highly reactive group-14 element species such as R2 E5CR2 , R2 E5ER2 , R3E, and R2 E: Rsalkyl, aryl,
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.
etc. are formed via various modes of reactions, and lead to many novel group-14 element compounds. However,
studies of photochemical reactions of arylated digermanes are very limited compared with those of the corresponding
disilanes.
We have recently reported the results of a study on photochemical reactions of arylated digermanes by chemical
w
x
reactions using trapping agents and nanosecond laser flash photolysis techniques 29–37 . Photolysis of the arylated
digermanes results in germanium–germanium bond homolysis to give a pair of two germyl radicals, which abstract a
hydrogen atom from hydrogen sources to give the corresponding hydromonogermanes, or couple to afford digermanes
as main products. In sharp contrast to the case of the aryldisilanes, germyl migration products to aromatic rings
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.
formal 1,3-germyl migration products could not be detected up to this time. Photochemical reaction pathways of
aryldigermanes may depend on the nature of the p system. Thus, we have examined photochemical reactions of
digermanyl-substituted naphthalenes and found the photochemical migration of a germyl group to the aromatic ring of
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.
arylated digermanes. In this paper, we report on the photochemical behavior of digermanyl naphthalenes by chemical
studies using trapping agents, laser flash photolysis, and ab initio MO calculations. The excited states of
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.
digermanyl naphthalenes responsible for the photoreactions are also discussed.
)
Corresponding author.
0022-328Xr98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.

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2. Results and discussion
2.1. Photolysis of 1-digermanyl-substituted naphthalenes
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.
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.
Each of cyclohexane solutions of 1- pentamethyldigermanyl naphthalene 1 , 1- pentamethyldigermanyl -2-methyl-
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.
Ž . Ž
.
naphthalene 2 , and 1- pentamethyldigermanyl -8-methylnaphthalene 3 ca. 0.1 M in a quartz photolysis cell was
degassed and then irradiated with a 110 W low pressure Hg arc lamp at room temperature under argon for 30 min.
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.
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.
Photolysis of a cyclohexane solution of 1a produced mainly an isomer, 1- dimethylgermyl -8- trimethylgermyl naph-
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. Ž
.
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.
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. Ž
. Ž
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thalene 4a 59% , along with 46% of recovered 1a and of 1- trimethylgermyl naphthalene 5a -1% Eq. 1 .
Products 4a and 5a were isolated in pure state and their structures were confirmed by GC-mass, IR, and H and 13C
1
NMR spectroscopic analysis. The IR, NMR, and GC-mass spectra of 5a were identical with those of the authentic
samples.
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.
To get information on the origin of hydrogermane 4a, photolysis of 1a in deuteriocyclohexane C6 D12 were
1
carried out under the same conditions. The H NMR spectrum of 4a thus obtained showed a septet resonance at d
5.25 ppm due to a Ge–H proton. No deuterium is incorporated in the photoproducts. A similar irradiation of
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.
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.
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.
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1- pentamethyldigermanyl heptadeuterionaphthalene 1b in cyclohexane gave 1- dimethyldeuteriogermyl -8- trimeth-
.
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.
ylgermyl deuterio-naphthalene 4b , which showed no resonance due to a Ge–H proton by NMR. The mass spectrum
q
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.
of 4b showed a parent ion M at mrz 355, indicating that 4b contains a deuterium bonded to a germanium atom.
These results indicate that the hydrogen on a germanium atom must come from the naphthyl ring, but not from the
solvent used. Photolysis of 2, in which the C2 position is occupied by a methyl group, afforded an isomer,
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.
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.
Ž . Ž
.
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.
1- dimethylgermyl -2-methyl-8- trimethylgermyl naphthalene 6 33% , together with 1- trimethylgermyl -2-methyl-
Ž . Ž
.
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Ž ..
naphthalene 7 4% in cyclohexane Eq. 2 . The photoisomerization of 1 and 2 to 4 and 6, respectively, clearly
indicates that the trimethylgermyl group attached to the a-germanium at the C1 position migrates to the C8 position
of the naphthyl ring. On the other hand, monogermanes 5 and 7 should be produced through the dimethylgermylene
extrusion from 1 and 2, respectively.
A similar photolysis of 3 in cyclohexane, in which the C8 position of the naphthyl ring is occupied by a methyl
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.
Ž . Ž
.
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.
group, yielded a variety of products; 1- trimethylgermyl -8-methylnaphthalene 8 17% , 1- dimethylgermyl -8-meth-
Ž . Ž . Ž
.
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.
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.
ylnaphthalene 9 1% , and octamethylcyclotetragermane 10 1% , together with 1-methylnaphthalene -1% .
w
x
Compound 10 may be formed via tetramerization of dimethylgermylene 37 . Expectedly, no migration products of
the germyl group to C8 position of the naphthyl ring were detected in the reaction mixture. A possible product formed
migration of the germyl group to the C2 position was not detected in the reaction mixture by means of GC-mass.

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K. Mochida et al.rJournal of Organometallic Chemistry 553 1998 163–171
165
Formation of monogermanes, 5, 7, 8, and cyclotetragermane 10 in the photolysate implies that dimethylgermylene
is generated during the photolysis of 1–3. However, the photolysis of 1a in cyclohexane containing 10–20 fold excess
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x
of 2,3-dimethyl-1,3-butadiene as a germylene trap 38 afforded 4a alone in 94% yield; no dimethylgermylene adduct
was detected in the reaction mixture. The reason for no formation of germylene and remarkable increase of the yield
of 4a during photolysis of 1a in the presence of 2,3-dimethyl-1,3-butadiene is described later. On the other hand, the
formation of hydrogermane 9 on photolysis of 3 is indicative of an intermediacy of germyl radicals generated by
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.
homolysis of the germanium–germanium bond of 1- digermanyl naphthalenes. Since germyl radicals are well known
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x
to abstract a chlorine atom from polyhalomethanes effectively 39 , the photolyses of 1–3 were carried out in
cyclohexane containing a 5–10 fold excess of chloroform. A small amount of the corresponding chlorogermane,
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.
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1- dimethylchlorogermyl -8-methylnaphthalene 1% , was detected along with 10 2% , pentamethylchlorodigermane
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.
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.
28% , and 1-methylnaphthalene -1% during photolysis of 3. No chlorogermanes, however, were formed in
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.
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.
photolyses of 1a and 2 in the presence of chloroform. Again, isomer 4a 55% and 6 33% were produced as major
products in the reaction mixtures of 1 and 2, respectively. A geminate pair of germyl radicals is expected to undergo a
disproportionation to give the corresponding hydrogermanes and germenes. To prove the existence of the germene
40 , the photolyses of 1–3 in cyclohexane containing a large excess 40- and 100-fold excess of ethanol were
examined. However, no ethanol addition products to the germenes were detected in the resulted photolysis mixture.
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x
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.
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.
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.
The isomer 4a 56% and 6 31% were formed as the major products. In marked contrast to the photolysis of
w
phenylated digermanes 31,32 , the germenes are not involved as the reactive intermediates in the photolysis of the
1-naphthyl system.
The structure of 4a was verified with GC-mass, IR, and 1H and 13C NMR spectroscopic methods. The positions of
two germyl groups on the naphthyl ring in 4a were carefully determined by 13C NMR distortionless enhancement by
1
1
1
13
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.
polarization transfer DEPT , H– H COSY, H– C COSY, and COLOC spectra, respectively.
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)
2.2. Laser flash photolysis of 1- digermanyl naphthalene
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.
To obtain more direct information on reactive intermediates in photochemical reactions of 1- digermanyl naph-
thalenes, measurements of nanosecond transient absorption spectra were performed on the degassed solutions
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x
containing 1a at 293 K using both a XeCl laser and N2 laser as excitatory light sources 41 .
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The time dependence of absorbance of the transient absorption A t was measured with cyclohexane solutions of
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.
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1a ca. 0.2 M . The A t curves were measured in the wavelength region of 350–600 nm, where the time resolution
of the apparatus was about 10 ns.
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By using the A t curves observed at various wavelengths, the time-resolved absorption spectra of 1a were
obtained at 240 ns and 20 ms after laser excitation as shown in Fig. 1. Two separated transient absorptions both at ca.
400 and 440 nm for 1a were observed at 240 ns after photoexcitation. As shown in Fig. 1, both transients at 400 and
440 nm decayed, and a new transient peak at 460 nm appeared at 20 ms. The signals show a rapid rise and subsequent
decay. The transient peak at 440 nm is reasonably assigned to that due to dimethylgermylene from comparison of the
Fig. 1. Transient absorption spectra at 240 ns and 20 ms after photoexcitation of 1.

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K. Mochida et al.rJournal of Organometallic Chemistry 553 1998 163–171
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x
spectral characteristics with those previously reported 39 . Analysis of the transient absorption due to dimethylgermy-
7
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lene revealed approximately second-order decay kinetics kr´s2.5=10 , k is the second-order rate constant and ´
.
is the molar extinction coefficient , suggesting the formation of digermene. The consistency of decay kinetics of the
dimethylgermylene measured in this study with the life time of fluorescence for 1a estimated from that of naphthalene
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x
derivatives 42 suggests that dimethylgermylene is generated through the singlet excited state of 1a. The assignment
of the transient peak at ca. 400 nm is tentatively ascribed to the corresponding digermene by comparing their spectral
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x
shapes and positions with those previously reported 37 .
Ž .
On the other hand, the transient peak at 460 nm is assigned to that of T §T1 of 1a, by the following reasons: 1
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xn Ž .
The Tn §T1 transition in naphthalene has been reported to be 430 nm 40 . 2 The absorption peak at 460 nm did not
appear at 10 ns after photoexcitation, but appeared at 10 ms.
2.3. Photolysis of 2-digermanyl-substituted naphthalene
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.
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.
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.
In marked contrast to 1- digermanyl naphthalenes, photolysis of 2- pentamethyldigermanyl naphthalene 11 in
4
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.
cyclohexane gave high molecular weight polymer Mws3.7=10 . The molecular weight of the polymer is relative
to polystyrene standards by means of gel permeation chromatography. The NMR spectrum of the polymers obtained
roughly shows several kinds of methyl groups attached to the germanium atom and the naphthyl group. The photolysis
of 11 gave polymeric products even in the presence of a trapping agent such as isobutene, ethanol, or 2-propanol.
Ishikawa and co-workers have reported that photolysis of 2- pentamethyldisilanyl naphthalene in the presence of
isobutene produces 2-isobutyldimethylsilyl-3-trimethylsilylnaphthalene, but in the absence of isobutene affords
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.
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polymeric substances 20 .
2.4. Mechanism for photoreactions of 1-digermanylnaphthalenes
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.
Recently, Ishikawa and co-workers have reinvestigated the photolysis of 1- pentamethyldisilanyl naphthalene and
related compounds and found the preferred migration of terminal trimethylsilyl group to the C8 position of the
Scheme 1.

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K. Mochida et al.rJournal of Organometallic Chemistry 553 1998 163–171
167
Ž .
Fig. 2. Optimized structure at the UHFrLANL1MB level for naphthylgermyl radical A . The geometry was optimized under the constraint of the
˚
planar naphthyl ring having a fixed C–C bond distance of 1.40 A and a C–C–C bond angle of 1208.
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x
naphthyl ring 21 . The major parts of the results of the photochemical studies of 1-digermanylnaphthalenes and
related compounds are good in accord with the mechanism proposed by Isikawa et al. As shown in Scheme 1, during
( )
the photolysis of 1-pentamethyldigermanylnaphthalene 1 , the homolytic scission of a germanium–germanium bond
of the photoexcited molecule would take place to give a pair of trimethylgermyl and naphthyldimethylgermyl radicals,
which recombine at the C8 position of the latter in the solvent cage followed by a 1,4-hydrogen shift to give 4. It is
interesting to note that during photolysis of 1 in the presence of 2,3-dimethyl-1,3-butadiene, the formation of 5 was
suppressed with increasing yield of 4. Since the diene is well-known triplet quencher, the results suggest that the
germylene extrusion occurs from the triplet excited state, while the homolytic Ge–Ge bond scission from the singlet
excited state. However, there is possibility of the formation of other products except for germylene from the triplet
excited state of 1.
Whereas rather unusual migration of the terminal germyl group of 1 to C8 position may be explained in line with
the orbital interaction method developed by Ishikawa et al., the radical recombination mechanism may also be
compatible with the results. The latter possibility was proved by ab initio MO UHF calculations of 1-naphthylgermyl
Ž .
radical A using the LANL1MB basis set. The geometry was optimized under the constraint of the planar naphthyl
˚
ring having a fixed C–C bond distance of 1.40 A and a C–C–C bond angle of 1208. As shown in Fig. 2, at the
optimized structure, the sp3-like singly occupied atomic orbital on germanium overlaps well with the naphthyl pp
orbital. The SOMO and spin density distribution of A are shown schematically in Fig. 3. Whereas the largest spin
density of A was observed at the germanium atom as expectedly, the second largest spin density was found at the C5
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.
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y0.555 and C8 q0.562 positions. Recombination of the radical pair would occur favorably at a position having
large spin density such at the C8 position.
Fig. 3. Schematic representation of SOMO and spin density distribution for 1-naphthylgermyl radical calculated at the UHFrLANL1MB level.

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3. Experimental details
1H and 13C NMR spectra were recorded on Bruker 600 MHz, Varian 400 MHz, Hitachi H-90 MHz, and
JNM-MY60 60 MHz NMR spectrometers. GC-MS spectra were obtained with a JEOL JMS-DX 303 mass
spectrometer. Infrared spectra were recorded on a Shimadzu FT IR 4200 spectrometer. UV and UV-Vis spectra were
recorded on a Shimadzu 2200 UV spectrometer. Gas chromatography was performed on Shimadzu GC-8A and Okura
Model 802 instruments with 1 m 20% SE30 and 1 m Apiezon L columns. Liquid chromatography was performed with
a JAI LC-908 with AJ 1H and 2H columns.
3.1. Materials
Chloroform, ethanol, 2-propanol, isobutene, 2,3-dimethyl-1,3-butadiene, 1-methylnaphthalene, and 1-
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boromonaphthalene were commercially obtained. Octamethylcyclotetragermane 43 and pentamethylchlorodigermane
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44 were prepared as described in the literature. Cyclohexane and deuteriocyclohexane as solvents were dried over
sodium wire and purified under argon.
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( )
3.2. Preparation of 1- pentamethyldigermanyl naphthalene 1a
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A solution of 1-naphthylmagnesium bromide prepared from 3.0 g 0.12 mol of magnesium and 27 g 0.13 mol of
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1-bromonaphthalene in a mixed solvent THF–ether–benzene, 13:25:38 ml was added to 20 g 0.078 mol of
pentamethylchlorodigermane in 50 ml of THF at room temperature. The mixture was then refluxed for 3 h and then
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hydrolyzed with dilute hydrochloric acid. After work-up in the usual manner, fractional distillation gave 20.5 g 76%
1
y1
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.
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of 1a: bp 109–1108Cr1 mmHg; H NMR d in CDCl3 0.50 s, 9H , 0.92 s, 6H , 7.3–8.1 m, 7H ; IR neat, cm
4
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.
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.
3072, 2970, 2903, 1504, 1232, 825, 790, 731, 594, 561; UV cyclohexane lmaxrnm e 226 5.44=10 , 285
3
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.
9.91=10 ; mass spectrum mrz 348. Anal. Calcd. for C15 H22Ge2: C, 51.84; H, 6.38%. Found: C, 51.93; H,
6.24%.
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( )
3.3. Preparation of 1- pentamethyldigermanyl perdeuterionaphthalene 1b
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A solution of 1- perdeuterionaphthyl magnesium bromide prepared from 0.9 g 0.037 mol of magnesium and 3.3 g
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0.015 mol of 1-bromo perdeuterionaphthalene in a mixed solvent THF–ether–benzene was added to 3.1 g 0.012
mol of pentamethylchlorodigermane in 10 ml of THF. The mixture was refluxed for 3 h and then hydrolyzed with
.
dilute hydrochloric acid. The organic layer was washed and dried over anhydrous magnesium sulfate. After work-up
1
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.
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in the usual manner, fractional distillation gave 3.4 g 80% of 1b: bp 123 8Cr2 mm Hg. H NMR d in CDCl3 0.37
y1
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.
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.
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.
s, 9H , 0.70 s, 6H ; IR neat, cm 2969, 2905, 2272, 1439, 1410, 1233, 825, 733, 629, 594, 572, 561; UV
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226 4.91=10 , 284 1.78=10 ; mass spectrum mrz 355. Anal. Calcd. for
4
3
.
cyclohexane lmaxrnm
e
C15 H15D7Ge2: C, 51.84; HqD, 6.38%. Found: C, 51.21; HqD, 6.16%.
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)
( )
3.4. Preparation of 1- pentamethyldigermanyl -2-methylnaphthalene 2
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A solution of 2-methyl-1-naphthylmagnesium bromide prepared from 6.1 g 0.25 mol of magnesium and 4.4 g
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0.02 mol of 1-bromonaphthalene in a mixed solvent THF–ether–benzene was added to 4.0 g 0.016 mol of
pentamethylchlorodigermane in 25 ml of THF at room temperature. The mixture was then refluxed for 3 h and then
hydrolyzed with dilute hydrochloric acid. The organic layer was washed and dried over anhydrous magnesium sulfate.
1
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.
After work-up in the usual manner, fractional distillation gave 0.8 g 14% of 2: bp 120–1228Cr2 mm Hg; H NMR
y1
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.
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.
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.
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.
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.
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.
2967, 1506, 1420, 1232, 828,
3
d in CDCl3 0.40 s, 9H , 0.89 s, 6H , 2.70 s, 3H , 7.1–8.1 m, 6H ; IR neat, cm
4
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.
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.
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792, 775, 738, 590; UV cyclohexane lmaxrnm e 231 5.01=10 , 290 7.379=10 ; mass spectrum mrz 362.
Anal. Calcd. for C15 H24Ge2: C, 53.15; H, 6.69%. Found: C, 53.12; H, 6.45%.
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( )
3.5. Preparation of 1- pentamethyldigermanyl -8-methylnaphthalene 3
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A solution of 8-methyl-1-naphthylmagensium bromide prepared from 0.51 g 0.021 mol of magnesium and 3.9 g
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.
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0.017 mol of 8-methyl-1-bromonaphthalene in a mixed solvent THF–ether–benzene, 12:18:29 ml was added to 5.1
g 0.02 mol of pentamethylchlorodigermane in 25 ml of THF. The mixture was refluxed for 1 week and then
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hydrolyzed with dilute hydrochloric acid. The organic layer was washed and dried over anhydrous magnesium sulfate.
1
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After work-up in the usual manner, fractional distillation gave 1.4 g 23% of 3: bp 121–1238Cr1 mm Hg. H NMR

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K. Mochida et al.rJournal of Organometallic Chemistry 553 1998 163–171
169
Ž
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.
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.
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.
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.
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.
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d in CDCl3 0.37 s, 9H , 0.75 s, 6H , 2.90 s, 3H , 7.1–7.9 m, 6H ; UV cyclohexane lmaxrnm e 233
4
4
.
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.
5.61=10 , 293 1.28=10 ; mass spectrum mrz 362. Anal. Calcd. for C16 H24Ge2: C, 53.15; H, 6.69%. Found:
C, 53.86; H, 6.59%.
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( )
3.6. Preparation of 2- pentamethyldigermanyl naphthalene 11
.
A solution of 2-naphthylmagensium bromide prepared from 1.0 g 0.041 mol of magnesium and 8.5 g 0.041 mol
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.
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.
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.
of 2-bromonaphthalene in a mixed solvent THF–ether–benzene, 24:36:58 ml was added to 5.2 g 0.02 mol of
pentamethylchlorodigermane in 10 ml of THF at room temperature. The mixture was then refluxed for 3 h. The
mixture was hydrolyzed with dilute hydrochloric acid. After work-up in the usual manner, fractional distillation gave
1
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.
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.
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.
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.
5.3 g 76% of 11: bp 118–1208Cr2 mm Hg. H NMR d in CDCl3 0.43 s, 9H , 0.70 s, 6H , 7.2–8.2 m, 6H ; IR
y1
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.
Ž
.
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neat, cm
3072, 2970, 2901, 2359, 1498, 1238, 815, 791, 739, 594, 559; UV cyclohexane lmaxrnm e 229
4
3
.
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.
7.49=10 , 291 4.16=10 ; mass spectrum mrz 348. Anal. Calcd. for C15 H22Ge2: C, 51.84 ; H, 6.38%. Found:
C, 51.95; H, 6.29%.
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)
( )
3.7. Preparation of 1- trimethylgermyl naphthalene 5a
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.
This compound was prepared in 60% yield, according to the method for 1- pentamethyldigermanyl naphthalene.
1
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.
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.
5a: bp 80–828Cr1 mm Hg; H NMR d in CDCl3 0.4 s, 9H , 7.5–8.5 m, 7H ; mass spectrum mrz 246.
(
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( )
3.8. Photolysis of 1- pentamethyldigermanyl naphthalene 1a
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.
A mixture of 12 mg 0.33 mol and n-eicosane as an internal standard in 2 ml of cyclohexane was placed in a
quartz photolysis cell. The cell was degassed in a vacuum and replaced with argon. The sample was irradiated with a
110 W low-pressure Hg arc lamp at room temperature for 30 min. After irradiation, the photoproducts were identified
Ž
by IR, GC-mass, and NMR spectra. Quantitative analysis of the product by GC shows the formation of 1- dimethyl-
.
Ž
.
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. Ž . Ž
.
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.
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.
germyl -8- trimethylgermyl naphthalene 4a 59% , 1- trimethylgermyl naphthalene 5a -1% , and unreacted 1a
1
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.
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.
.
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.
46% were formed. Isomer 4a was isolated by preparative GC. H NMR d in CDCl3 0.394 d, 6H, Js3.1 Hz ,
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.
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.
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.
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0.562 s, 9H , 5.25 sept., 1H, Js3.1 Hz , 7.38 dd, 1H, Js8.3, 7.1 Hz , 7.40 dd, 1H, Js8.3, 6.8 Hz , 7.66 d,
13
.
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.
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.
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.
Ž
1H, Js6.8 Hz , 7.75 d, 1H, Js8.3 Hz , 7.77 d, 1H, Js7.1 Hz , 7.78 d, 1H, Js8.3 Hz ; C NMR d in
y1
.
Ž
.
3050, 2975,
CDCl3 -1.7, 3.6, 124.2, 124.3, 130.2, 130.6, 133.8, 134.3, 135.9, 140.8, 140.9, 142.6; IR neat, cm
2907, 2104, 1489, 1414, 1305, 1237, 831, 816, 777, 700, 692, 599, 582, 569; mass spectrum Mq mrz 348.
3.9. Photolysis of 1a
3.9.1. Photolysis of 1a in the presence of ethanol
A mixture of 16 mg 0.045 mmol of 1a and n-eicosane in 20 ml of cyclohexane containing 11 mg 0.24 mmol of
ethanol was irradiated for 4 h. The compounds 4a 56% and 5a -1% were formed with recovery of 1a 55% .
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
3.9.2. Photolysis of 1a in the presence of 2,3-dimethyl-1,3-butadiene
A mixture of 16 mg 0.041 mmol of 1a and n-eicosane in 20 ml of cyclohexane containing 25 mg 0.3 mmol of
2,3-dimethyl-1,3-butadiene was irradiated for 4 h. The compounds 4a 70% were formed with recovery of 1a 26% .
Ž
.
Ž
.
Ž
.
Ž
.
(
)
( )
3.10. Photolysis of 1- pentamethyldigermanyl heptadeuterionaphthalene 1b
Ž
.
Ž
.
A cyclohexane solution 4 ml of 1b 10 mg, 0.028 mmol was irradiated and analyzed by GC, GC-MASS, and
1
NMR spectra. Isomer 4b was isolated by preparative GC. H NMR d in CDCl3 0.394 s, 6H , 0.562 s, 9H ; 13C
Ž
.
Ž
.
Ž
.
y1
Ž
.
Ž
.
NMR d in CDCl3 y1.7, 3.6, 124.2, 124.3, 130.2, 130.6, 133.8, 134.3, 135.9, 140.8, 140.9, 142.6; IR neat, cm
1237; MS Mq mrz 355.
(
)
( )
3.11. Photolysis of 1- pentamethyldigermanyl -2-methylnaphthalene 2
Ž
.
A mixture of 10 mg 0.03 mmol of 2 and n-eicosane in 20 ml of cyclohexane was irradiated for 1 h. Unreacted 2
Ž
.
Ž
.
Ž
.
Ž . Ž
.
Ž
.
66% , 1- dimethylgermyl -8- trimethylgermyl -2-methylnaphthalene 6 33% , and 1- trimethylgermyl -2-methyl-
Ž . Ž
.
naphthalene 7 45% were observed. Photoproducts 6 and 7 were separated by preparative GC and their structures
1
Ž
.
Ž
were assigned by comparing the NMR and GC data of similar compounds. 6: H NMR d in CCl4 0.40 d, 6H,

(
)
170
K. Mochida et al.rJournal of Organometallic Chemistry 553 1998 163–171
.
Ž
.
Ž
.
Ž
.
Ž
.
Js2.5 Hz , 0.60 s, 9H , 2.70 s, 3H , 5.30 sept., 1H, Js3.0 Hz , 7.2–8.2 m, 5H ; mass spectrum, mrz 362, 345,
1
Ž
.
Ž
.
Ž
.
Ž
.
229, 213, 155, 141, 119, 104, 89. 7: H NMR d in CCl4 0.45 s, 9H , 2.70 s, 3H , 7.2–8.2 m, 6H ; mass spectrum
mrz 260, 245, 213, 155, 141, 115, 87.
3.12. Photolysis of 2 in the presence of 2,3-dimethyl-1,3-butadiene
Ž
.
Ž
.
A cyclohexane solution of 12 mg 0.033 mmol of 5 with 27 mg 0.32 mmol of 2,3-dimethyl-1,3-butadiene was
Ž
.
Ž
.
irradiated for 36 h. Unreacted 2 50% and 6 81% were detected by GC in the reaction mixture.
(
)
( )
3.13. Photolysis of 1- pentamethyldigermanyl -8-methylnaphthalene 3
Ž
.
A mixture of 12 mg 0.033 mmol of 3 and n-eicosane in 20 ml of cyclohexane was irradiated for 2 h.
Ž . Ž Ž . Ž
Ž
.
.
Ž
.
.
1- Trimethylgermyl -8-methylnaphthalene 8 17% , 1- dimethylgermyl -8-methylnaphthalene 9 1% , and oc-
tamethylcyclotetragermane 1% , and 1-methylnaphthalene -1% were formed with recovery of 3 40% . Photo-
Ž
.
Ž
.
Ž
.
products 8 and 9 were separated by preparative GC and assigned by comparing the NMR and GC data of similar
1
Ž
.
Ž
.
Ž
.
Ž
.
compounds. 8: H NMR d in CCl4y10.40 s, 9H , 2.90 s, 3H , 7.2–8.2 m, 6H ; mass spectrum mrz 260, 245, 213,
Ž
.
153, 141, 115, 89. 9: IR neat, cm
2095; mass spectrum mrz 246, 231, 199, 173, 141, 127, 111, 99, 87, 77.
3.14. Photolysis of 3 in the presence of chloroform
Ž
.
Ž
.
Photolysis of 3 in 20 ml of cyclohexane containing 36 mg 0.3 mmol of chloroform for 2 h gave 8 2% ,
Ž
.
Ž
.
Ž
.
1- dimethylchlorogermyl -8-methylnaphthalene 1% , pentamethylchlorodigermane 28% , and 1-methylnaphthalene
-1% with recovery of 3 30% . Mass spectrum of 1- dimethylchlorogermyl -8-methylnaphthalene: mrz 280, 265,
Ž
.
Ž
.
Ž
.
229, 141, 115.
(
)
( )
3.15. Photolysis of 2- pentamethyldigermanyl naphthalene 11
Ž
.
A mixture of 15 mg 0.042 mmol of 11 and n-eicosane as an internal standard in 20 ml of cyclohexane was
Ž
.
obtained for 100 min. A high molecular weight polymer Mws37000, MwrMn s2.5, 25% was obtained with
Ž
.
unreacted starting 11 70% .
3.16. Time-resolÕed optical absorption
Ž
.
The sample 1a 1.9 mmol in cyclohexane was placed in quartz cell with an optical length of 5 mm and was
degassed by four freezed-pump-thaw cycles. Laser flash-photolysis experiments were performed at room temperature
by use of XeCl laser as an excitatory light source. The laser pulse was about 10 ns, and the details of the laser
w
x
photolysis apparatus have been published elsewhere 39 .
3.17. MO calculation
MO calculations were carried out by the ab initio MO using the Gaussian 92 program. The LANL1MB basis set
was employed for the calculations. The calculations were carried out by IBMrRS6000.
Acknowledgements
We thank Prof. Tsutomu Kumagai of Tohoku University for measuring 600 MHz NMR spectra. The authors also
thank Prof. Masahiro Kotani and Dr. Ryuichi Kato of Gakushuin University for measuring laser flash photolysis. This
research was supported in part by the Ministry of Education, Science, and Culture.
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