Organometallics 1995, 14, 567-569
567
Direct Conversion of Hydrosilanes to Fluorosilanes with CuF2*2H20/CC14 Jun-ichi Yoshida,*J Hidekazu Tsujishima, Kazunori Nakano,2 Toshiyuki Teramoto, Keiji Nishiwaki, and Sachihiko hoe* Department of Material Science, Faculty of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi, Osaka 558, Japan Received July 14, 1994@ Summary: The reaction of hydrosilanes with Cu'IF2.2H~O in refluxing CCl4 gave the corresponding fluorosilanes in good yields. In THF hydrosilanes were recovered unchanged. X-ray powder analysis of the solid products indicated the formation of C u U . These results suggests that both cc14 and Cu" act as oxidants for hydrosilanes.
a-Heteroatom-substituted organosilicon compounds have attracted considerable research interest because of their unique properties in electron-transfer reaction^.^ In an attempt to synthesize sila-functional a-heteroatom-substituted organosilicon compounds, we needed a convenient method for the conversion of hydrosilanes t o the corresponding fluorosilanes. Although there are a great number of methods for the synthesis of chlorosilanes from the corresponding hydr~silanes,~ only a few methods for the direct conversion of hydrosilanes to fluorosilanes have been found so far. Tang et al. reported monofluorination of RzSiHz with SbF3,5 but SbF3 is highly toxic6 Olah and co-workers reported ionic fluorination of R3SiH using highly reactive NOBF4 or NOzBF4.' Bulkowski et al. employed Ph3CBF4 to convert RzSiHz to RzSiHF.* Finch et al. used PF5 to fluorinate RSiH3 to give RSiHzF and R S ~ H F ZAnder.~ son also reported the conversion of EtsSiH to EtsSiF by the action of AgF.'O In this paper we wish to report a new convenient method for the conversion of hydrosilanes to fluorosilanes by the action of CuI1Fz*2Hz0in Abstract published in Aduance ACS Abstracts, December 1, 1994. (1) Present address: Department of Synthetic Chemistry & Biological Chemistry, Faculty of Engineering, Kyoto University, Kyoto 606-01, Japan. (2) Undergraduate Research Participant, Osaka Institute of Technology. (3) For example: (a)Yoshida, J.; Maekawa, T.; Murata, T.; Matsu1990,112, 1962. (b) Yoshida, J.; naga, S.; Isoe, S.J.Am. Chem. SOC. Murata, T.; Matsunaga, S.;Maekawa, T.; Shiozawa, S.; Isoe, S. Rev. Heteroat. Chem. 1991,5, 193 and references cited therein. (4) For example: (a) Banovetz, J. P.; Hsiao, Y.-L.; Waymouth, R. 1093,115,2540. (b) Kunai, A.; Kawakami, T.; M. J. Am. Chem. SOC. Toyoda, E.; Ishikawa, M. Organometallics 1092,11, 2708. (c) Nagai, Y.; Matsumoto, H.; Yagihara, T.; Morishita, K. Kogyo Kagaku Zasshi 1968,71,1112. (d) Nagai, Y.; Yamazaki, K.; Shiojima, I.; Kobori, N.; Hayashi, M. J. Organomet. Chem. 1967,9,21. (e) Curtice, J.; Gilman, 1957, 79,4754. (0 Baines, I. H.; Hammond, G. S.J.Am. Chem. SOC. E.; Eabom, C. J. Chem. SOC. 1966, 1436. (g) Russel, G. A. J. Org. Chem. 1966,21, 1190. (h) Jenkins, J. W.; Post, H. W. J. Org. Chem. 1950,15,556. (i) Whitmore, F. C.; Pietrusza, E. W.; Sommer, L. H. J. Am. Chem. SOC. 1947, 69, 2108. ( 5 ) Hong, C. M.; Witt, S. D.; Tang, Y. N. J. Flwrine Chem. 1983, 23, 359. (6) Damrauer, R.; Simon, R. A. Organometallics 1988,7, 1161. (7) Prakash, G. K. S.; Wang, Q.; Li, X.; Olah, G. A. New J. Chem. 1990,14, 791. (8) Bulkowski, J . E.; Stacy,R.; Van Dyke, C. H. J. Organomet. Chem. 1976, 87, 137. (9) Finch, M. A.; Marcus, L. H.; Smirnoff, C.; Van Dyke, C. H.; Viswanathan, N. Synth. Inorg. Met.-Org. Chem. 1971, 103. (10) Anderson, H. H. J. Am. Chem. SOC. 1958,80, 5083.
Table 1. Conversion of Hydrosilanes to Fluorosilanes with CUF&IzO/CC~ hydrosilane ("01)
CUFZQH~O mmnl
PhoSiH
(5.03) (5.01)
14.9 14.9
(5.03)
14.9
Ph2SiH2
(5.17)
14.8
C,oHz1SiMe2H
(1.93)
6.0
(1.20)
3.9
PhS-SiMepH
(0.98) 3.0 phSYS1Me2H SiMezH
product
yield ("A)
Ph,SiF
EO 45
=
Ob Ph2SiF2
85
C I ~ H Z I S ~ M ~ ~78 F PhS,SiMezF
70
hSY SiMe2F SiMe2F
63
A
A
0:
SiMe2F
(2.10)
6.2
77
SiMe2F
*
,IThe reaction was canied out in refluxing ClCH2CHzCl. The reaction was carried out in refluxing THF.
CC14 under very mild conditions (eq 1).
@
CuF2*2H20
R3SiH cc4,reflux- R3SiF
(1)
Results and Discussion The fluorination reactions of hydrosilanes with copper(I1) fluoride are very simple to perform. In a typical experiment, t o a solution of a hydrosilane (5 mmol) in carbon tetrachloride (15 mL) was added copper(I1)fluoride dihydrate (15 mmol), and the mixture was heated to reflux overnight. The reaction mixture was filtered through Celite, and the filtrate was distilled to obtain the corresponding fluorosilane. The results obtained for several hydrosilanes are shown in Table 1. The present reaction is effective for arylsilanes, alkylsilanes, and a-heteroatom-substituted silanes. It is also noteworthy that organosilanes containing two Si-H bonds can be converted into difluorinated compounds by using the present reaction. It should be pointed out that hydrosilanes are known to be readily converted to the corresponding chlorosilanes by the treatment with metal salts in carbon
0276-733319512314-0567$09.00/0 0 1995 American Chemical Society
Notes
568 Organometallics, Vol. 14,No. I , 1995
tetrachloride which acts as both the oxidant and the chloride source. As a matter of fact, hydrosilanes were converted into the corresponding chlorosilanes in refluxing CC4 in the presence of a catalytic amount of CuF2-2H20. The fact that the treatment of hydrosilanes with a stoichiometric amount of copper(I1) fluoride in THF gave rise to complete recovery of the starting material also indicates the important role played by carbon tetrachloride. The reaction in 1,2-dichloroethane, which is less effective as a chlorine donor in radical reactions, gave fluorosilanes in lower yields. It is also noteworthy that organotrichlorosilanes are easily converted into organotrifluorosilanes by treatment with copper(I1)fluoride.ll On the basis of these facts, we initially proposed the following mechanism. The first step of the reaction involves copper(I1) fluoride catalyzed oxidation of hydrosilanes to chlorosilanes by the action of carbon tetrachloride (eq 2).4a9c9dPresumably the reaction proceeds by a radical-chain mechanism.4d In the second step, chlorosilanes are converted into fluorosilanes by the halogen-exchange reaction with copper(I1) fluoride (eq 3). CuF,cat. + CCl, R,SiCl + CHCl, R,SiC1 + '/,CuF, - R,SiF + '/,CuCl,
R,SiH
R,SiH
+ CCl, + '/,CuF,
-
R,SiF
+ CHC1, + '/,CuCl,
(2)
(3)
(4)
The mechanism of the present reaction, however, was found to be more complicated, because X-ray powder analysis of the solid product indicated the formation of CuCl and CuOHF. Signals of CuClz were not detected at all. These results indicate that copper(I1) was reduced to copper(1) during the course of the reaction. Kunai and Ishikawa et al. reported that the reaction of hydrosilanes with Cu"C12 in the presence of CUI gave the correspondingchlorosilanes and C U I C ~Therefore, .~~ in the case of the present reaction, the initially formed CuI'C12 also seemed to react with hydrosilanes to give Cu'C1 and chlorosilanes (eq 5).
R,SiH
+ 2CuC1, - R,SiC1 + 2CuC1+ HC1
(5)
The combination of eqs 3 and 5 gives eq 6.
R,SiH
+ ,/,CuCl, + '/,CuF,
-
R,SiF
+ 2CuC1+ HC1 (6)
By the combination of eqs 4 and 6, we propose the following stoichiometry of the present reaction (eq 7). 4R3SiH
+ 3CC1, + 2CuF, 4R,SiF + 3CHC1, + 2CuC1+ HC1 (7)
The formation of CuOHF may be explained in terms of the hydrolysis of CuFz under the reaction conditions. (11) (a) Tamao, K.; Yoshida, J.; Yamamoto, H.; Kakui, T.; Matsumob, H.; Takahashi, M.; Kurita, A.; Murata, M.; Kumada, M. Organometallics 1982,1, 355. (b) Shin-Etsu Chemical Industry Co., Ltd. Jpn. Kokai Tokkyo Koho J p 81,167,693; Chem. Abstr. 1980, 96, 199870~.
Although the detailed mechanism of the present reaction is not fully understood, as a consequence of mild reaction conditions, the ready availability of CuFy2H20, and operational simplicity, this method should find extensive use in the chemistry of fluorosilanes.
Experimental Section General Remarks. Glass-support precoated (Merk silica gel 60 Fzu, 0.25 mm) plates were employed for analytical TLC. Vapor-phase chromatography (VPC) was performed on a Shimadzu gas chromatograph equipped with a 2 m x 3 mm column packed with Silicone OV-l(2%) on Chromosorb WAW DMCS. Proton NMR spectra were determined on a Hitachi R-90H spectrometer (90 MHz) or a JEOL JNM-GX-400 spectrometer (400 MHz). Carbon NMR spectra were determined on a JEOL JNM-GX-400 spectrometer. Infrared (IR) spectra were determined on a JASCO A-102 diffraction grating spectrophotometer. Mass spectra were obtained on a JEOL JMSAX500 spectrometer; the ionization potential was 70 eV. Materials. CuF92Hz0 was purchased from Nakarai Tesque, Inc., and used as obtained. ((Pheny1thio)methyl)dimethylsilane was prepared by deprotonation of thioanisole with BuLi in ether followed by the reaction with chlorodimethylsilane.l2 (Phenylthio)bis(dimethylsilyl)methanewas prepared by deprotonation of ((pheny1thio)methyl)dimethylsilane with LDA followed by the addition of dimethylchlorosilane.12 ((Menthylo-)methy1)diphenylsilane was prepared by the transmetalation reaction of ((menthy1oxy)methyl)tributylstannanewith BuLi followed by the treatment with chlorodipheny1silane.l2 o-Bis(dimethylsily1)benzene was prepared according to the literature method.13 Preparation of Triphenylfluorosilane. Typical Procedure for Fluorination Using CuF2*2H~0.To a stirred mixture of CuF2-2H20 (2.052 g, 14.9 mmol) and C c 4 (15 mL) was added triphenylsilane (1.309 g, 5.03 mmol) at room temperature. The mixture was refluxed overnight. Solid materials were separated by filtration, and the solvent was removed by evaporation. Recrystallization of the crude produce from hexane gave triphenylfluorosilane (1.111g, 3.99 mmol, 79%): mp 61-63 "C (lit.' mp 61-62 "C); VPC t~ 14.4 min (OV-12% 2 m 100-240 "C, 10 "C/min); 'H NMR (90 MHz, 2250 (w), CDCls) 6 7.26-7.87 (m, 15H); IR 3075 (m), 3020 (w), 1595 (m), 1430 (s), 1190 (w), 1125 (SI, 1000 (w), 890 (s), 840 (m), 695 (8) cm-'; low resolution MS mle 278 (1001, 201 (99), 181 (121, 154 (831, 124 (4). Diphenyldifluorosilane6(bulb-to-bulb distillation 150160 "C/20 mmHg): VPC t~ 7.2 min (OV-1 2% 2 m 100-240 "C, 10 Wmin); TLC Rf 0.29 (hexane/ethyl acetate, 99:l); 'H N M R (90 MHz, CDCls) 6 7.14-7.92 (m, 10 H); low-resolution MS m/e (%) 220 (1001, 199 (191, 154 (66), 143 (231, 77 (281, 51 (4). Dodecyldimethylfluorosilane (bulb-to-bulb distillation 102 "C/19 mmHg); VPC t~ 7.4 min (OV-1 2% 2 m, 100-230 Wmin); TLC Rf 0.85 (hexane); 'H NMR (90 MHz, CDCls) 6 0.22 (d, J = 7.5 Hz, 6 H), 0.50-1.68 (m, 21 H); IR 2930 (s), 2860 (m), 1460 (w), 1260 (m), 1220 (w), 850 (m), 800 (w), 780670 (br, m) cm-'; low-resolution MS mle (%) 218 (0.5), 203 (441, 190 (O.l), 175 (0.2), 161 (O.l), 140 (81, 119 ( 5 ) , 105 (571, 85 (6), 77 (loo), 71 ( 5 ) , 57 (7); high-resolution MS calcd for C12H27SiF 218.1866, found 218.1861. Anal. Calcd for ClzH2,SiF: C, 65.99; H, 12.46. Found: C, 66.13; H, 12.38. ((Menthy1oxy)methyl)dimethylfluorosilane (bulb-tobulb distillation 105-125 "C/30 " H g ) : VPC t~ 6.6 min (OV-1 2% 2 m, 100-240 "C, 10 "C/min); 'H NMR (400 MHz, CDC13) 60.24(d, J=3.67Hz,3H),0.25(d, J=3.05Hz,3H),0.691.00 (m, 12H), 1.13-1.24 (m, lH), 1.24-1.38 (m, lH), 1.51(12) Yoshida, J.; Tsujishima, H.; Nakano, K.; Isoe, S. Inorg. Chim. Acta 1994,220, 129. (13)Fink, W.Helu. Chim. Acta 1974, 57, 1010.
Notes 1.67 (m, 2H), 2.05-2.21 (m, 2H), 2.82-2.94 (m, lH), 2.90 (dd, J = 5.49 and 13.43 Hz, 1H), 3.45 (dd, J = 3.67 and 13.43 Hz, 1H); IR (CDCl3) 2960 (SI, 2920 (81, 2870 (81, 1451 (W), 1370 (w), 1349 (w), 1260 (81,1108 (m), 1088 (m), 1073 (m), 852 (s), 810 (m), 708 (br) cm-'; low-resolution MS (CI) mle (S) 231 (121, 245 (34), 227 (22), 197 (€9,168 (3), 161 (9), 149 (e),140 (loo), 139 (loo), 137 (78), 123 (23), 109 (21); high-resolution MS (M H) calcd for C13H28OSiF 247.1893, found 247.1882. Anal. Calcd for C13HzaOSiF: C, 63.36; H, 11.04. Found: C, 63.07; H, 10.87. ((Pheny1thio)methyl)dimethylfluorosilane (bulb-tobulb distillation 120-140 "C/20" H g ) : TLC Rf0.40 (hexanel ethyl acetate, 39:l); VPC t~ 4.0 min (OV-1 2% 2 m, 100-240 "C, 10 "C/min); lH NMR (90 MHz, CDCl3) 6 0.35 (d, J = 7.5 Hz, 6H), 2.35 (d, J = 4.5 Hz, 2H), 7.00-7.50 (m, 5H); IR (neat) 2960 (m), 2890 (w),1585 (81,1485 (s),1440 (s), 1390 3060 (w), (m), 1255 (SI, 1135 (m), 1090 (m), 1070 (w), 1025 (m), 840 (br, s), 735 (s), 685 (s) cm-1; low-resolution MS (EI)mle (%) 200 (97), 185 (26), 165 (13), 154 ( 1 9 , 139 (50), 123 (251, 109 (121, calcd 91 (931, 77 (100),65 (6),51(4); high-resolution MS (M+) for CgH13SiSF 200.0492, found 200.0482. Anal. Calcd for CgH13SiSF: H, 53.96; H, 6.54. Found: C, 53.97; H, 6.55. (Phenylthio)bis(dimethylfluomsilyl)meth (bulb-tobulb distillation 123 "Cl15 mmHg): VPC t~ 9.2 min (OV-1 2% 2 m, 100-240 "C, 10 "C/min); 'H NMR (CDCl3) 6 0.27 (d, 5.4 Hz,6H), 0.38 (d, 5.4 Hz, 6H), 1.82 (t, 4.5 Hz, lH), 6.93-7.63 (m, 5H); IR (neat) 3100 (w), 3000 (m), 2930 (w), 1595 (s), 1490 (s), 1450 (m), 1410 (w), 1270 (s),llOO (m), 1035 (m), 1020 (m), 870 (br), 765 (s), 750 (s), 700 (s) cm-'; low-resolution MS (EI) m/e (%) 276 (491, 261 (91, 245 (41, 217 (21, 199 (30), 180 (261, 165 (loo), 151 ( l l ) , 135 (531, 122 (5), 103 (4), 91 (6), 77 (241,
+
Organometallics, Vol. 14, No. 1, 1995 569 59 (6); high-resolution MS (M+)calcd for C~&&Siflz 276.0636, found 276.0648. Anal. Calcd for C11HlaSSizF2: C, 47.78; H, 6.56. Found C, 47.84; H, 6.37. o-Bis(dimethylfluorosily1)benzene (bulb-to-bulb distillation 120-140 "Cl20 "Hg):VPC t~ 5.8 min (OV-l2%,100240 "C, 10 "C/min); lH N M R (CDCl3) 6 0.46-0.52 (m, 6H), 7.40-7.46 (m, 2H), 7.64-7.69 (m, 2H); IR (neat) 3120 (w), 3070 (m), 3050 (m), 2960 (s), 2900 (m), 1580 (w), 1560 (w), 1415 (s), 1260 (s), 1125 (s), 1065 (s), 1040 (s), 840 (9, br), 800 (s), 750 ( 8 ) cm-l; low-resolution MS (EI) mle (%) 230 (M+, 2), 217 (111, 216 (22), 215 (loo), 199 ( l l ) , 119 (18), 77 (13); high-resolution MS (M+)calcd for CloHl&F2 230.0758, found 230.0758. Anal. Calcd for C ~ O H ~ ~ SC,~ 52.13; ~ F Z :H, 7.00. Found: 52.15; H, 6.92. X-ray Powder Analysis. After the reaction of triphenylfluorosilane with CuFz.2HzO in refluxing CCL, solid materials were separated by filtration and dried. X-ray analysis of the solid products with a Rigaku RAD-IA diffractometer (copper) showed signals for CuCl and CuOHF together with those of unchanged CuF2-2H20, which were assigned by comparison with the literature data.14
Acknowledgment. We thank Prof. Nobuyuki Aikawa, Osaka City University, for the use of powder X-ray diffractometer, and valuable discussions. We also thank the Ministry of Education, Science, and Culture of Japan for the Grant-in-Aid for Scientific Research. OM940561X (14) Smith, J. V., Ed.Powder DiTfraction File 1967;American Society for Testing and Materials: York, PA, 1967.
