Organometallics 1989, 8, 2767-2771
2767
Silicon-Carbon Unsaturated Compounds. 25. Synthesis and Photochemical Behavior of Bis(disilanyl) benzenes Mitsuo Ishikawa, Hiromu Sakamoto, and Fuji0 Kanetani Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 724, Japan
Akio Minato Kyoto Pharmaceutical University, Yamashina, Kyoto 607, Japan Received May 2, 1989
The synthesis and photochemical behavior of 1,2-,1,3-,and 1,4-bis(disilanyl)benzeneshave been reported. 1,2-Bis(pentamethyldisilanyl)benzene(1) was prepared by the reaction of bis(pentamethyldisilany1)acetylene with a-pyrone, while 1,3- and 1,4-bis(disilanyl)benzenes were synthesized by condensation of di-Grignard reagents prepared from m- and p-dibromobenzene with the corresponding chlorodisilanes. Irradiation of 1 in the presence of isobutene gave 2-(isobutyldimethylsilyl)-1-(pentamethyldisilany1)-3-(trimethylsi1yl)benzene in 27% yield and its isomers as secondary photoproducts. Similar irradiation of 1,3-bis(pentamethyldisilany1)benzene with isobutene produced 3-(isobutyldimethylsily1)-l-(pentamethyldisilanyl)-4-(trimethylsilyl)benzene,and l,l-dimethyl-6-[l,l-dimethyl-2-(trimethylsilyl)ethyl]-4-(pen~methyldisilany1)silepin in 70 and 9% yields, while 1,3-bis(1-phenyltetramethyldisilany1)benzenegave 3-(isobutylmethylphenylsilyl)-l(l-phenyltetramethyldisilanyl)-4(trimethylsily1)benzenein 80% yield. The photolysis of 1,4-bis(pentamethyldisilanyl)benzene under the same conditions afforded 4-(isobutyldimethylsilyl)-l-(pentamethyldisilany1)-5-(trimethylsilyl)benzeneand 1,l-dimethyl-6-[l,l-dimethyl-2-(trimethylsilyl)ethyl]-3-(pentamethyldisilanyl)silepinin 72 and 14% yields. Similar photolysis of 1,4-bis(1phenyltetramethyldisilany1)benzene yielded 4-(isobutylmethylphenylsilyl)-l-(l-phenyltetramethyldisilanyl)-5-(trimethylsilyl)benzenein 71% yield.
Introduction In 1975, We found that irradiation of a benzene solution of pentamethylphenyldisilane with a low-pressure mercury lamp produces a sliene arising from a 1,3-shift of a trimethylsilyl group to an ortho carbon atom of the phenyl ring.' Further studies from this laboratory showed that the photochemical formation of the silene (rearranged silene) is a remarkable general for various benzenoid aromatic disilanese2 The photochemical reaction of the polymeric system involving a disilanylenephenylene group as repeating units, however, proceeds with a different fashion. In fact, irradiation of a benzene solution of poly@-disilanylenephenylenes) under the same conditions as in the photolysis of the aryldisilanes results in the formation of an another type of a silene (nonrearranged silene) produced from homolytic scission of a silicon-silicon bond, followed by redistribution of the resulting silyl
radical^.^
Ph Ph
Ph
Ph
Ph
tie
Me
Ph
ranged silene, is formed from the photolysis of these compounds. In this paper we report the synthesis of 1,2-, 1,3-, and 1,6bis(disilanyl)benzenes and their photochemical behavior in the presence of isobutene in benzene.
Results and Discussion Synthesis of Bis(disilany1)benzenes. 1,2-Bis(pentamethyldisilany1)benzene (1) was prepared by the Diels-Alder reaction of bis(pentamethyldisilany1)acetylene with a-pyrone, which is the similar method to that reported for the synthesis of 1,2-bis(trimethylsilyl)benzeneby Evnin and S e ~ f e r t h . When ~ a mixture of bis(pentamethy1disilany1)acetylene with an excess of a-pyrone was heated to reflux, gentle extrusion of carbon dioxide was observed. After a 16-h reaction, compound 1 was obtained in 42% yield together with a small amount of 1,3-bis(pentamethyldisilany1)benzene (2) (less than 5%). Compound 1 could be readily isolated by fractional distillation under reduced pressure from the reaction mixture. The amount of byproduct 2 is highly dependent upon the purity of a-pyrone as well as bis(pentamethy1disilany1)acetylene. For example, the reaction using a-pyrone containing a small amount of water and other impurities gave 1 in 20% yield but 2 in 25% yield. In this case, presumably acid-catalyzed isomerization of 1 occurred giving 1,3-isomer 2.5
1
Me
It is interest to us to investigate the photochemical behavior of bis(disilany1)benzenes that are considered to be the least unit of the disilanylenephenylene polymers and to learn which silene, the rearranged silene or nonrear(1) Ishikawa, M.; Fuchikami, T.; Sugaya, T.; Kumada, M. J . Am. Chem. SOC.1975, 97, 5923. (2) Ishikawa, M.; Kumada, M. Adu. Organomet. Chem. 1981,19,51. (3) Nate, K.; Ishikawa, M.; Ni, H.; Watanabe, H.; Saheki, Y. Organometallrcs 1987, 6, 1673.
SiMe,SiMe,
SiMe,SxMe,
I
2
(4) Evnin, A. B.; Seyferth, D. J . Am. Chem. SOC.1967, 89,952.
0276-7333/89/2308-2767$01.50/00 1989 American Chemical Society
2768 Organometallics, Vol. 8, No. 12, 1989
Ishikawa et al.
Scheme I SiMe,SiMe,
Scheme I1 SiMe,SiMe,
SiMe,SiMe,
SIMe,SiMe, hv
CH2=CMe,
b'SiMe2S,Me3
I
SiMe, SMe,
2
SiMe2SiMe,
SiMe,SiMe,
kMe,
6v
6
9
+
Me,SiMe2Si
SiMeSiMe, &SiMe;CH,CHMe,
6-
SiMe, 7
8
All attempts to prepare 1 by other methods, for example, cocondensation of 1,2-bis(chlorodimethylsilyl)benzeneand chlorotrimethylsilane with lithium metal or sodium-potassium alloy and the reaction of o-dibromobenzene with magnesium in the presence of chloropentamethyldisilane, were unsuccessful. In all reactions, no compound 1 was produced. In contrast to the 1,2-isomer 1, compound 2, 1,3-bis(lphenyltetramethyldisilany1)benzene (3), l,Cbis(pentamethyldisilany1)benzene (4), and 1,4-bis(l-phenyltetramethyldisilany1)benzene (5) could readily be synthesized by the reaction of di-Grignard reagents prepared from mand p-dibromobenzene with the corresponding chlorodisilanes. The structures of 1-5 were confiimed by IR, mass, and 'H and 13C NMR spectroscopic analysis as well as elemental analysis. Photolysis of 1,2-Bis(pentamethyldisilanyl)benzene (1). When a benzene solution of 1 in the presence of a 28-fold excess of isobutene was photolyzed with a lowpressure mercury lamp bearing a Vycor filter at ambient temperature for 8 h, 2-(isobutyldimethylsily1)-1-(pentamethyldisilanyl)-3-(trimethylsily1)benzene(6) was obtained in 27% yield in addition to a mixture consisting of two products (23% combined yield) whose mass spectrum shows the parent ion at m / e 394, corresponding to the calculated molecular weight of 6. In this photolysis, 25% of the starting 1 was recovered unchanged. The product 6 could be readily separated from the isomers by preparative GLC. The structure of 6 was confirmed by IR, mass, and lH and 13C NMR spectroscopic analysis (see Experimental Section). The 'H NMR spectrum of the phenyl region for 6 clearly indicates that this compound has a 1,2,3-trisubstituted benzene structure. Furthermore, saturation of the resonance of the dimethylsilyl protons of the isobutyldimethylsilyl group of 6 performed in NOE-FID difference experiments at 500 MHz produced a positive nuclear Overhauser effect of two trimethylsilyl protons and isobutyl protons. Irradiation of trimethylsilyl protons on the C-3 atom of the benzene ring caused a positive NOE of a proton on C-4 as well as isobutyldimethylsilyl protons. These results are consistent with the proposed structure. The formation of 6 can best be understood in terms of the ene reaction of the photochemically generated rearranged silene with isobutene, as shown in Scheme I. This type of product can always be obtained in the photolysis of benzenoid disilanes in the presence of many kinds of trapping agents.6 (5) Seyferth, D.; White, D. L. J. A m . Chem. SOC.1972, 94, 3132. (6) Ishikawa, M.Pure AppE. Chem. 1978, 50, 11.
On the other hand, detail analysis of the reaction mixture in the early stage of the photolysis indicated that two isomers were formed as secondary photoproducts. In fact, irradiation of 6 under the same conditions produced the same mixture of isomers. All attempts to isolate two isomers in a pure form using GLC or LPC were unsuccessful. However, the 'H NMR spectroscopic analysis of the mixture showed that two isomers are present in a ratio of 1:2. The chemical shifts due to the abundant isomer were identical with those of 3-(isobutyldimethylsily1)-1-(pentamethyldisilanyl)-4-(trimethylsilyl)benzene (7) obtained from the photolysis of 2 in the presence of isobutene. As expected the retention time on GLC for this compound was identical with that of 7. Proton resonances in the phenyl region for the other isomer also showed the 1,2,4trisubstituted benzene structure. Therefore, we tentatively assigned this isomer as 2- (isobutyldimethylsilyl)- 1-(pentamethyldisilanyl)-4-(trimethylsilyl)benzene (8). The formation of products 7 and 8 can be explained by the photochemical valence isomerization of 6. Similar isomerization has been reported for the photolysis of o-bis(trimethylsilyl)benzene.' In the photolysis of 1, no products originating from the nonrearranged silene were detected by either GLC or spectrometric analysis. Photolysis of 1,3-Bis(disilanyl)benzenes2 and 3. Irradiation of a benzene solution of 1,3-bis(pentamethyldisilany1)benzene (2) in the presence of isobutene with a low-pressure mercury lamp afforded two products, 3(isobutyldimethylsily1)- 1-(pentamethyldisilany1)-4-( trimethylsily1)benzene (7) produced from the ene reaction of the rearranged silene with isobutene and 1,l-dimethyl-6-[l,l-dimethyl-2-(trimethylsilyl)ethyl]-4-(pentamethyldisilany1)silepin (9) in 70 and 9% yields, respectively, in addition to 6% of the starting material 2 (Scheme 11). In this photolysis trace amounts of three other products were detected by GLC (less than 3% combined yield). The GC-mass spectrometric analysis of these products indicates that two of them have a parent ion peak at m / e 394, corresponding to the calculated molecular weight of 7, while the parent ion of the other is calculated to be m l e 280, which is identical with that of the product formed from extrusion of dimethylsilylene form the starting 2. The extrusion of dimethylsilylene from aryldisilanes has already been reported.8 The structures of 7 and the silepin 9 were verified by IR, mass, and IH and 13CNMR spectroscopic analysis and also by elemental analysis. The 300-MHz 'H NMR spectrum of 7 indicates that the proton on the C-5 position of the benzene ring shows a double doublets due to ortho and para coupling (J = 7.4 and 0.7 Hz),and the proton on the C-6 position reveals ortho and meta coupling (J= 7.4 and 1.4 Hz), while the proton on the C-2 position shows (7) Seyferth, D.; Blank, D. R.; Evnin, A. B. J. Am. Chem. SOC.1967, 89,4793.
(8)Ishikawa, M.; Fuchikami, T.; Kumada, M. J. Organomet. Chem. 1976, 118, 155.
Organometallics, Vol. 8, No.12, 1989 2769
Silicon-Carbon Unsaturated Compounds
Scheme V
Scheme I11 SiMelSiMe,
SiMe2SiMe,
M e , S i M e ( R ) S ioSiMe(R)SiMe,
hv
Me,SiMe(R)Si d z i e ( R )
4 , R-Me S , R-Ph
SiMe,
SiMe2SiMe3 P CH2=CMe2
Me,SrMe(R)Si &Me(RjCH2CHMe, II
, R=Me
I 3 . R=Ph
-
Scheme IV hv
Me2 MqSiMeSiQSiMe,
M e 3 S i M e 2 S i a CMe,CH,SiMe, SiMe
I 2 , R=Me
3
CH,=CMe2 P
IO
meta and para coupling (J = 1.4 and 0.7 Hz). These results show that compound 7 must have a 1,3,4-trisubstituted benzene structure but not a 1,2,3-trisubstituted one. For compound 9, coupling patterns on the silepin ring are wholly consistent with those of a 4,6-disubstituted silepin structure. Thus, protons at 6 5.30 (C,-H) and 6.67 ppm (C,-H) reveal a doublet (J = 14.2 Hz), and the proton at 5.07 ppm ((2,-H) also shows a doublet (J = 1.4 Hz), while the proton at 6.52 (C,-H) shows a broad singlet. As we reported previously:JO the most probable mechanism for the formation of the silepin 9 involves walk rearrangement of an initially formed 7-silabicyclo[4.1.0]heptadiene intermediate from the reaction of the rearranged silene with isobutene to the sterically favored isomer, followed by ring expansion to 9 (Scheme 111). The photolysis of compound 3 is of interest because regiochemistry is involved for the formation of silenes. Irradiation of 3 with isobutene in benzene gave a product identified as 3-(isobutylmethylphenylsily1)-1-(1-phenyltetramethyldisilanyl)-4-(trimethylsilyl)benzene (10) produced by the reaction of the silene arising from migration of a trimethylsilyl group to the phenylene ring, but not to the phenyl ring, with isobutene in 80% yield (Scheme IV). Although three isomers of compound 10 were detected in trace amounts in the photolysis mixture by GC-mass spectrometric analysis (less than 5% combined yield), no products originated from the nonrearranged silene were detected by either GLC or spectroscopic analysis. In this photolysis, even if a silepin derivative was produced, the yield can be estimated to be less than 3%. All spectral data obtained for 10 were consistent with the proposed structure (see Experimental Section). Photolysis of 1,4-Bis(disilanyl)benzenes4 and 5. When a benzene solution of 4 in the presence ofisobutene was photolyzed under the same conditions, two compounds, 4-(isobutyldimethylsily1)-1-(pentamethyldisilanyl)-5-(trimethylsilyl)benzene (11) and 1,l-dimethyl6-[1,l-dimethyl-2-(trimethylsilyl)ethyl]-3-(pentamethyl(9) Ishikawa, M.; Fuchikami,T.;Kumada, M. Tetrahedron Lett. 1976, 1299. ~~. . (10)Ishikawa, M.; Fuchikami, T.; Kumada, M. J.Organomet. Chem. 1978,162, 223.
disilany1)silepin (12), were obtained in 72 and 14% yields, respectively, as shown in Scheme V. GC-mass spectrometric analysis of the photolysis mixture showed the presence of a compound produced by the extrusion of dimethylsilylene from the starting material 4 (less than 3%). Secondary photoproducts having a parent ion peak at mle 394, corresponding to that of 11, were also detected in trace amounts (3% combined yield), when 90% of 4 was photolyzed. In the early stages of the photolysis, no such products were observed in the photolysis mixture. The structures of 11 and 12 were confirmed by IR,mass, and 'H and I3C NMR spectrometric analysis as well as elemental analysis. The location of the substituents on a benzene ring for 11 and a silepin ring for 12 were established by NOE-FID difference experiments at 300 MHz. Thus, saturation of the trimethylsilyl protons on a benzene ring of 11 produced a positive NOE of a proton at the C-6 position. Irradiation of the dimethylsilyl protons of a pentamethyldisilanyl group caused a positive NOE of protons at the C-2 and C-6 positions of the phenyl ring. Similar irradiation of the resonance of the dimethylsilyl protons of an isobutyldimethylsilylgroup led to the strong enhancement of a proton at the C-3 position of the ring and also methylene protons of the isobutyl group. For 12, irradiation of two methyl protons on a silicon atom on the silepin ring resulted in the enhancement of protons at the C-2 and C-7 positions, while irradiation of the proton at the C-5 position led to a positive NOE of a proton at C-4 in the silepin ring and dimethyl protons of a l,l-dimethyl-2-(trimethylsilyl)ethylgroup. As expected, saturation of dimethyl protons of the 1,l-dimethyl-2(trimethylsily1)ethyl group caused a positive NOE of the protons at the C-5 and C-7 positions and methylene protons. These results are wholly consistent with the proposed structures for 11 and 12. Again, the formation of compound 11 may be understood in terms of the ene reaction of the rearranged silene with isobutene, whereas compound 12 may be explained by the similar mechanism to that described for the silepin 9. In order to check whether or not the present reactions involve energy transfer from the photoexcited benzene to the bis(disilanyl)benzene, we carried out the photolysis of 4 in hexane. Thus, irradiation of a hexane solution of 4 with a low-pressure mercury lamp gave 11 and 12 in 50 and 11% yields, respectively, showing that the direct excitation of the bis(disilany1)benzene occurs in the present photolyses. Similar photolysis of compound 5 gave 4-(isobutylmethylphenylsily1)-1-(l-phenyltetramethyldisilanyl)-5(trimethylsily1)benzene (13) produced from the ene reaction of the rearranged silene arising from a 1,3-trimethylsilyl shift to the phenylene, but not the phenyl ring,
2770 Organometallics, Vol. 8, No. 12, 1989
with isobutene in 71% yield. A trace of an isomer of 13 was produced as a primary photoproduct, but the products from the nonrearranged silene could not be detected in the reaction mixture. That a trimethylsilyl group migrates only to the phenylene ring, but not to the phenyl ring, to give the silene in the photolysis of 3 and 5 is presumably due to the stronger charge-transfer interaction of the disilanyl group with the phenylene ring than that with the phenyl ring in the photoexcited state.ll Product 13 was identified by IR, mass, and 'H and 13C NMR spectrometric analysis. In the 300-MHz 'H NMR spectrum of 13, a proton attached to the C-2 position of the phenylene ring shows ortho and meta coupling ( J = 7.4 and 1.4 Hz), respectively, while a proton on the C-6 position reveals meta and para coupling ( J = 1.4 and -0 Hz). These results indicate that compound 13 must have a 1,4,btrisubstituted benzene structure. In marked contrast to the poly(p-disilanylenephenylenes), the photolysis of the bis(disilany1)benzenes affords no products derived from the nonrearranged silenes arising from homolytic scission of a silicon-silicon bond, followed by redistribution of the resulting silyl radicals.
Experimental Section General Procedure. All reactions were carried out under an atmosphere of dry nitrogen. Ultraviolet spectra were recorded on a Shimadzu Model UV-visible recording spectrophotometer. Infrared spectra were determined on thin liquid films for liquid samples and on KBr disk for crystal samples using a Perkin-Elmer 1600 FT-infrared spectrometer. Gas chromatographic separations were carried out by using a column packed with 30% SE-30 Silicone on Chromosorb P. NMR spectra for compounds 1-5 were determined with a JEOL Model JNM-FX-9OA spectrometer. 'H and 13C NMR spectra for compounds 6-8 were determined with JEOL Model JNM-GX-500 spectrometer, while for compounds 9-13 were measured on a Varian Model XL-300 spectrometer. Mass spectra were determined on a Shimadzu Model GCMS-QP 1000. Materials. 1-Chloropentamethyldisilaneand l-chloro-lphenyltetramethyldiilane were prepared as reported previously.10 a-Pyrone was prepared as reported in the literature! Benzene was dried over lithium aluminum hydride and distilled before use. Preparation of l&Bis(pentamethyldisilanyl)benzene (1). In a 50-mL flask fitted with a condenser was placed 10.6 g (0.11 mol) of a-pyrone and 17.1 g (0.06 mol) of 1,2-bis(pentamethyldisilany1)acetylene. The mixture was heated to reflux for 16 h, and the mixture was distilled under reduced pressure to give 8.4 g (42% yield) of 1: UV (in cyclohexane) A, (e) 216 (14600),231 nm (14100);IR 3065,3044,2950,2894,1924,1446,1410,1246,1109, 1050, 1037 cm-*; MS 338 (M'); 'H NMR (6 in CC4) 0.07 (s, 18 H, Me3Si),0.41 (s, 12 H, Meai), 6.97-7.50 (m, 4 H, aromatic ring protons); 13CNMR (6 in CDC13)-1.35 (Me3.%),0.16 (Meai), 127.1, 136.3, 145.7 (aromatic ring carbons). Anal. Calcd for C16HNSi4: C, 56.72; H, 10.12. Found: C, 56.55; H, 10.11. Preparation of 1,3-Bis(pentamethyldsilanyl)benzene(2). In a 300-mL three-necked flask fitted with a condenser, stirrer, and dropping funnel was placed 5.8 g (0.24 mol) of magnesium and 33.4 g (0.20 mol) of chloropentamethyldisilane in 40 mL of THF. To this was added a solution of 23.9 g (0.10 mol) of mdibromobenzene in 50 mL of T H F a t room temperature over a period of 2 h. The mixture was heated to reflux for 6 h and then hydrolyzed with water. The organic layer was separated, and the aqueous layer was extracted with ether. The organic layer and extracts were combined, washed with water, and dried over magnesium sulfate. The solvents were evaporated, and the residue was distilled under reduced pressure to give 21.9 g (65% yield) of a colorless liquid: bp 116.5-117.5 "C (2 mmHg); UV (in cyclohexane) ,A, (€) 205 (20 600), 231 nm (20 700); IR 3070,3050, ~
~~~
~~
(11) Hiratauka, H.; Mori, Y.; Ishikawa, M.; Okazaki, K.; Shizuka, H. J. Chem. SOC.,Faraday Trans. 1985,81, 1665.
Ishikawa et al. 2950,2900,1400,1360,1240,1120,1100 cm-'; MS 338 (M'); 'H NMR (6 in CC1,) 0.06 (s, 18 H, Me3Si), 0.31 (s, 12 H, Me2Si), 7.07-7.48 (m, 4 H, aromatic ring protons); 13CNMR (6 in CDCl,) -3.98 (Me&), -2.23 (Me3Si),127.1, 133.7, 138.5, 139.4 (aromatic ring carbons). Anal. Calcd for C16HSSi4: c, 56.72; H, 10.12. Found: C, 56.47; H, 10.12. Preparation of 1,3-Bis( 1-phenyltetramethyldisilany1)benzene (3). In a 300-mL three-necked flask was placed 3.4 g (0.14 mol) of magnesium and 40 mL of THF. To this was added a mixture of 30.2 g (0.13 mol) of l-chloro-l-phenyltetramethyldisilane and 17.7 g (0.08 mol) of m-dibromobenzene in 40 mL of THF over a period of 1h. The mixture was heated to reflux for 6 h and hydrolyzed with water. The organic layer was separated, and the aqueous layer was extracted with ether. The organic layer and extracts were combined, washed with water, and dried over magnesium sulfate. The solvents were evaporated, and the residue was distilled under reduced pressure to give 16 g (46% yield) of a colorless liquid bp 200-201 "C (0.8 mmHg); UV (in cyclohexane) A, ( e ) 213 (44100),232 nm (sh); IR 3080,3020,2955,2900,1430, 1410,1360,1250,1100 cm-'; MS 462 (M'); 'H NMR (6 in CC4) 0.09 (s, 18 H, Me3Si), 0.55 (s, 6 H, MeSi), 6.92-7.60 (m, 14 H, aromatic ring protons); 13CNMR (6 in CDClJ -4.96 (MeSi),-1.69 (Me3Si), 127.4, 127.8, 128.6, 134.8, 135.0, 136.6, 137.5, 141.7 (aromatic ring carbons). Anal. Calcd for CBHsSi4: C, 67.46; H, 8.27. Found: C, 67.65; H, 8.20. Preparation of 1,4-Bis(pentamethyldsilanyl)benzene (4). In a 200-mL three-necked flask was placed 2.43 g (0.10 mol) of magnesium and 30 mL of THF. To this was added a mixture of 16.7 g (0.10 mol) of chloropentamethyldisilane and 11.8 g (0.05 mol) of p-dibromobenzene dissolved in 50 mL of THF over a period of 1.5 h. The reaction mixture was heated to reflux for 1h, and then it was allowed to stand overnight. The mixture was hydrolyzed and worked up as usual. Distillation under reduced pressure gave 12.7 g (75% yield) of 4 bp 111-113 "C (1mmHg); mp 80-80.5 "C (after recrystallization from ethanol); UV (in cyclohexane) k- ( e ) 211 (17500),248 nm (23400);IR 3050,2950, 2900,1400,1380,1245,1130 cm-'; MS 338 (M+);'H NMR (6 in CDC13) 0.12 (s, 18 H, Me3Si),0.36 (s, 12 H, Me2Si),7.28 (s, 4 H, aromatic ring protons);'% NMR (6 in CDC13)-3.93 (MGi), -2.15 (Me3Si),133.1, 139.5 (aromatic ring carbons). Anal. Calcd for C16HSSi4: C, 56.72; H, 10.12. Found: C, 56.62; H, 10.03. Preparation of 1,4-Bis(l-phenyltetramethyldisilanyl)benzene ( 5 ) . In a 100-mL three-necked flask was placed 2.5 g (0.10 mol) of magnesium and 20 mL of THF. To this was added a mixture of 22.9 g (0.10 mol) of l-chloro-l-phenyltetramethyldisilane and 11.8 g (0.05 mol) of p-dibromobenzene in 20 mL of THF over a period of 2 h. The mixture was heated to reflux for 4 h. The mixture was hydrolyzed with a water. The organic layer was separated, and the aqueous layer was extracted with ether. The organic layer and extracts were combined, washed with water, and dried over magnesium sulfate. The solvents were distilled off, and the residue of the flask was distilled under reduced pressure to give a crystalline compound boiled over a range of 205-215 "C at 3 mmHg. Recrystallizationfrom ethanol gave 13.5 g (58% yield) of 5: mp 112.5-113.5 "C; UV (in cyclohexane) A, (e) 212 (44 loo), 238 nm (28100);IR 3050,2950,2900,1480,1430, 1420,1380,1240, 1120,1100 cm-'; MS 462 (M'); 'H NMR (6 in CC14)0.14 (s, 18 H, Me3%),0.57 (s, 6 H, MeSi), 7.04-7.57 (m, 14 H, aromatic ring protons); 13CNMR (6 in CDC13)-4.96 (MeSi), -1.59 (Me3Si),127.9, 128.7, 134.1, 134.8, 137.4, 137.8 (aromatic ring carbons). Anal. Calcd for C&&4: C, 67.46, H, 8.27. Found C, 67.43; H, 8.27. Photolysis of 1. A solution 0.763 g (2.26 mmol) of 1, 3.53 g (63.0 mmol) of isobutene, and 0.063 g (0.220 mmol) of docosane as an internal standard in 90 mL of benzene was placed in a 1WmL reaction vessel, fitted with a low-pressuremercury lamp bearing a Vycor filter. The mixture was irradiated a t room temperature for 8 h with a slow stream of nitrogen bubbling through the mixture. The reaction mixture was analyzed by GLC as being 2-(isobutyldimethylsilyl)-l-(pentamethyldisilanyl)-3(trimethylsily1)benzene (6) (27% yield), a mixture of 3-(isobutyldimethylsilyl)-l-(pentamethyldisilanyl)-4-(trimethylsilyl)benzene (7) and 2-(isobutyldimethylsilyl)-l-(pentamethyldisilanyl)-4-(trimethylsilyl)benzene (8) (23% combined yield), and the starting material 1 (25%). The product 6 and a mixture of 7 and 8 were isolated by preparative GLC. For compound 6: IR
Silicon-Carbon Unsaturated Compounds 2953, 2895, 1876, 1406, 1248, 1088, 1039 cm-'; 'H NMR (6 in CDCl,) 0.09 (s, 9 H, Me3Si), 0.37 (s, 9 H, Me3%), 0.40 (s, 6 H, Me2Si),0.44 (s, 6 H, Me2Si),0.93 (d, 2 H, CH2,J = 6.0 Hz), 0.94 (d, 6 H, Me&, J = 6.3 Hz), 1.85 (m, 1 H, CH), 7.14 (t, 1H, Ar-H, Jofiho = 7.1 Hz), 7.43 (dd, 1 H, Ar-H, Jofiho = 7.1 Hz, JneU= 1.1 Hz), 7.53 (dd, 1 H, Ar-H, Joho= 7.1 Hz, Jneb= 1.1Hz); '3C NMR (6 in CDC13)-1.16 (Me3Si),1.48 (Me2Si),3.00 (Me,Si), 3.07 (Me3Si), 25.46 (Me2C),26.21 (CH,), 28.32 (CH), 124.1, 134.6, 135.6, 147.9, 148.4,154.2(aromatic ring carbons);exact mass calcd for C&,$i4 394.2364, found 394.2375. Chemical shifts for 7 in the 'H NMR spectrum were identical with those of the authentic sample. For 8: 'H NMR (6 in CDC13)0.11 (s, 9 H, Me3Si),0.27 (s, 9 H, Me3Si), 0.38 (9, 6 H, Me,Si), 0.39 (s, 6 H, Me,Si), 0.84 (d, 2 H, CH2,J = 6.7 Hz), 0.94 (d, 6 H, MeC, J = 6.7 Hz), 1.81 (m, 1 H, HC), 7.44 (dd, 1H, Ar-H, Joho = 7.3 Hz, Jmeh= 1.2 Hz), 7.55 (d, 1H, Ar-H, Jofiho = 7.3 Hz), 7.79 (br s, 1 H, Ar-H); exact mass calcd for C20H4zSi4394.2364, found 394.2340. Photolysis of 2. A mixture of 0.994 g (2.94 mmol) of 2, 7.48 g (133.6 "01) of isobutene, and 0.1565 g (0.505 mmol) of docosane as an internal standard in 115 mL of benzene was placed in a 120-mL reaction vessel. The mixture was irradiated with a lowpressure mercury lamp for 1.5 h. The mixture was analyzed by GLC as being 7 (70% yield) and 9 (9% yield). After the solvent and isobutene were evaporated off, the residue was distilled under reduced pressure (1mmHg) to give volatile products. Pure 7 and 9 were isolated by preparative GLC. For compound 7: IR 1460, 1410,1250,1150,1095 cm-'; MS 394 (M'); 'H NMR (6 in CDC1,) 0.09 (s, 9 H, Me3Si),0.33 (s, 6 H, Me,%), 0.38 (s,9 H, Me3Si),0.41 (s,6 H, Me2Si),0.84 (d, 2 H, CH2,J = 6.9 Hz), 0.90 (d, 6 H, Me2C, J = 6.6 Hz), 1.79 (m, 1 H, HC), 7.41 (dd, 1 H, CB-H,Jofiho = 7.4 Hz, JmeU = 1.4 Hz), 7.62 (dd, 1 H, Cb-H, Jofiho = 7.4 Hz, J lva = 0.7 Hz), 7.76 (dd, 1 H, C2-H,JmeU = 1.4 Hz, J,, = 0.7 Hz!; 13C NMR (6 in CDCl,) -4.08 (Meai),-2.19 (Me3Si),1.18 (Me,Si), 2.06 (Me3Si),25.18 (CH), 26.33 (MeC), 28.18 (CH,), 133.0, 134.4, 138.4, 140.9, 144.4, 145.8 (aromatic ring carbons). Anal. Calcd for C20H42Si4:C, 60.83; H, 10.72. Found: C, 60.70; H, 10.72. For 9: IR 1570,1410,1250,1020cm-'; MS 394 (M'); 'H NMR ( 6 in CDCl,) 0.00 (s, 6 H, Me&), 0.11 (s, 9 H, Me3Si),0.12 (s, 9 H, Me3&),0.14 (s,6 H, Me,Si), 0.72 (s, 2 H, CH,), 1.23 (s, 6 H, MeC), 5.07 (d, 1 H, C,-H, J = 1.4 Hz), 5.30 (d, 1 H, CZ-H, J = 14.2 Hz), 6.52 (br s, 1 H, C,-H), 6.67 (d, 1 H, C3-H,J = 14.2 Hz); 13CNMR (6 in CDCl,) -4.26 (Me,&), -1.82 (Me3&),0.16 (Me,Si), 1.86 (Me3%),32.03 (Me2C),33.12 (CH,), 39.18 (CMe,), 123.8, 126.9, 142.7, 145.4, 147.4, 165.7 (silepin ring carbons). Anal. Calcd for C20H42Si4:C, 60.83; H, 10.72. Found: C, 60.87; H, 10.77. Photolysis of 3. A solution of 0.910 g (1.97 mmol) of 3, 5.76 g (103 mmol) of isobutene, and 0.1192 g (0.384 mmol) of docosane in 100 mL of benzene was photolyzed for 2.5 h at room temperature. After evaporation of the solvent, the residue was analyzed by GLC as being 10 (80% yield). The residue was then distilled under reduced pressure to give 10. Pure 10 was isolated by preparative GLC: IR 1580, 1430,1250,1140, 1100 cm-'; MS 518 (M'); 'H NMR (6 in CDC1,) 0.096, 0.104 (two s, 9 H, Me3Si), 0.155, 0.165 (two s, 9 H, Me3Si),0.563, 0.567 (two s, 3 H, MeSi), 0.623,0.630(twos, 3 H, MeSi), 0.85-0.88 (m, 6 H, MeC), 1.07-1.20 (m, 2 H, CH,), 1.73-1.85 (m, 1 H, HC), 7.27-7.81 (m, 13 H, aromatic ring protons); 13C NMR (6 in CDC13)-5.26 and -5.20 (MeSi),-1.69 (Me3%),0.11 and 0.16 (MeSi), 1.88 (Me3Si),22.67 (CH), 26.21 (CH,), 26.40 (MeC), 127.7, 127.8, 128.6, 128.7, 134.13, 134.17, 134.6, 134.8, 134.9, 136.17, 136.22, 137.22, 137.30, 140.03,
Organometallics, Vol. 8, No. 12, 1989 2771 140.05, 141.9, 143.28, 143.34, 147.3 (aromatic ring carbons). Anal. Calcd for C30H46Si4:C, 69.42; H, 8.93. Found: C, 69.28 H, 9.04. Photolysis of 4. A solution of 1.019 g (3.01 mmol) of 4, 5.68 g (101.4 mmol) of isobutene, and 0.145 g (0.468 mmol) of docosane in 115 mL of benzene was photolyzed for 2 h. The solvent and isobutene were evaporated off, and the residue was analyzed by GLC as being 11 (72% yield) and 12 (14% yield). Products 11 and 12 were separated by preparative GLC. For 11: IR 1460, 1410,1250,1150,1090cm-'; MS 394 (M'); 'H NMR (6 in CDClJ 0.08 (s,9 H, Me3%),0.34 (s, 6 H, Me2Si),0.38 (s, 9 H, Me3Si),0.41 (s,6 H, Me,Si), 0.83 (d, 2 H, CH2,J = 6.9 Hz), 0.92 (d, 6 H, Me2C, J = 6.6 Hz), 1.81 (m, 1H, CH), 7.41 (dd, 1 H, Ar-H, Jofiho = 7.4 = 1.4 Hz), 7.61 (dd, 1 H, Ar-€3, Jofiho = 7.4 Hz, J = Hz, JmeU 0.7 Hz), 7.77 (dd, 1 H, Ar-H, Jmeh = 1.4 Hz, Jp,, = 0.7 Hz!; 13C NMR (6 in CDC13)-4.05 (Me2&),-2.15 (Me3Si),0.94 (Meai),2.22 (Me3Si),25.17 (CH), 26.36 (MeC), 28.02 (CH,), 133.0, 134.5, 138.4, 140.8, 144.6, 145.6 (aromatic ring carbons). Anal. Calcd for C20H42Si4:C, 60.83; H, 10.72. Found: C, 60.72; H, 10.67. For 12: IR 1580, 1400, 1360, 1240 cm-'; MS 394 (M'); 'H NMR (6 in CDC13)0.02 (s, 6 H, Me2&),0.08 (s, 9 H, SiMeJ, 0.11 (s, 9 H, SiMe,), 0.13 (s,6 H, SiMe,), 0.74 (s, 2 H, CH,), 1.21 (s,6 H, MeC), 5.13 (d, 1H, HC, J = 1.5 Hz), 5.86 (d, 1H, HC, J = 0.8 Hz), 6.04 (dd, 1 H, HC, J = 11.5,0.8 Hz), 6.21 (dd, 1 H, HC, J = 11.5, 1.5 Hz); 13C NMR (6 in CDCl, -4.03 (Me2%),-1.94 (Me3%), 0.10 (Me,Si), 1.90 (Me,Si), 32.03 (MeC), 33.65 (CH,), 39.25 (CMe), 123.9, 133.1, 134.9, 141.4, 161.1, 164.4 (aromatic ring carbons). Anal. Calcd for C20H42Si4:C, 60.83; H, 10.72. Found: C, 60.84; H, 11.01. Photolysis of 4 in Hexane. A solution of 1.009 g (2.98 mmol) of 4, 1.35 g (24.1 mmol) of isobutene, and 0.211 g (0.932 mmol) of cetane as an internal standard in 120 mL of hexane was photolyzed for 2 h. The solvent and isobutene were distilled off, and the residue was analyzed by GLC as being 11 (50% yield) and 12 (11%yield). Products 11 and 12 were separated by preparative GLC. All spectral data obtained for 11 and 12 were identical with those of authentic samples. Photolysis of 5. A solution of 1.005 g (2.18 mmol) of 5, 6.1 g (109 mmol) of isobutene, and 0.109 g (0.331 mmol) of docosane in 100 mL of benzene was photolyzed for 2.5 h. GLC analysis of the reaction mixture showed that 13 was formed in 71% yield. The solvent was evaporated, and the residue was distilled under reduced pressure to give 13. Pure 13 was isolated by preparative GLC: IR 1580, 1430, 1250, 1140, 1100 cm-'; MS 518 (M'); 'H NMR (6 in CDClJ 0.13 (s, 9 H, Me3Si),0.17 (s, 9 H, Me3&),0.62 (s, 3 H, MeSi), 0.65 (s, 3 H, MeSi), 0.88 (d, 6 H, MeC, J = 6.5 Hz), 1.13-1.17 (m, 2 H, CH,), 1.82 (m, 1 H, HC), 7.27-7.87 (m, 13 H, aromatic ring protons); 13C: NMR (6 in CDC13)-5.11 (MeSi), -1.62 (Me3&),-0.26 (MeSi),2.04 (Me3Si),24.98 (CH), 26.19 (CH,), 26.50 (MeC), 127.6, 127.8, 128.7, 128.8, 133.8, 134.6, 134.8, 135.8, 136.6, 137.2, 139.8, 142.1, 143.3, 145.8 (aromatic ring carbons). Anal. Calcd for C3,,H4&,: C, 69.42; H, 8.93. Found: 69.24; H, 9.03.
Acknowledgment. This research was supported in part by a Grant-in-Aid for Scientific Research by the Ministry of Education to which the authors' thanks are due. We also express our appreciation to shin-etsu Chemical Co. Ltd., Nitto Electric Industrial Co. Ltd., and Dow Corning Japan Ltd. for financial support.
