Znd. Eng. Chem. Res. 1996,34,1387-1389
1387
Polysilahydrocarbon Synthetic Fluids. 3. Synthesis of Six-Carbon-BridgedTrisilahydrocarbons Kazimiera J. L. Paciorek,* Wen-Huey Lin, and James H. Nakahara Technolube Products Division, Lubricating Specialties Company, 3365 E . Slauson Avenue, Vernon, California 90058
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Trisilahydrocarbons of the general formula R z S ~ ( ~ - C ~ H ~ Z were S~R obtained ~ ) Z by a three-step process starting with ClzSiH2/1,5-hexadiene interaction. The first reaction gave ring compounds C12Si(CH2)4CHCH3and C ~ Z S ~ ( C H Z ) ~ C H inCaddition Z H ~ to the trisilahydrocarbon precursor ClzSi[(CH2)4CH=CHz12. Rigid temperature control was necessary to minimize the cyclics formation and to avoid the double bond isomerization. The C6-bridged trisilahydrocarbons exhibited essentially identical viscosity/molecular weight profiles as the Ce-bridged materials. Attempted preparation of C4-bridged trisilahydrocarbons was unsuccessful due to the predominant cyclization in the first step.
Introduction The early work on monosilahydrocarbons (Rosenberg et al., 1960; Baum and Tamborski, 1961; Tamborski et al., 1983) provided the foundations for polysilahydrocarbon research and the study of trisilahydrocarbons (Paciorek et al., 1990) and tetrasilahydrocarbons (Paciorek et al., 1991). The latter materials based on their wide liquid ranges, low pour points, negligible volatility at elevated temperatures, and ease of structurelproperty (viscosity) tailoring are promising candidates for space lubricants. Since oxidizing atmospheres are not encountered in the envisioned applications, the oxidative stability is not essential. The advantage of silahydrocarbons over perfluoroalkyl ether fluids such as Fomblins (Sianesi et al., 1971) and the Krytox family of materials (Gumprecht, 1967) is their inertness in the presence of metals, which is the major drawback of the perfluoroalkyl ethers (Paciorek and Kratzer, 1994). Silahydrocarbons can be viewed as unbranched hydrocarbons with the silicon atoms acting as plasticizers. The aim of the current investigation was to determine the effect, if any, of the bridge length in R&i[(CH2)&R312 materials on the viscositylmolecular weight profiles. Only the system wherein x = 8 was studied.
Experimental Section General Procedures. Operations were carried out either in an inert-atmosphere enclosure (Vacuum/ Atmospheres Model HE-93B), under nitrogen bypass, or in vacuo. Infrared spectra were recorded on a PerkinElmer Model 1330 infrared spectrophotometer as capillary and 0.5 mm films. Molecular weights were determined in benzene using a Mechrolab Mcdel302 vapor pressure osmometer. The mass spectra (EI) were obtained using a Du Pont Model 21-491B spectrometer attached to a Varian Aerograph Model 2700 gas chromatograph (W)equipped with a flame ionization detector and a Du Pont 21-094 data acquisition and processing system. Gas chromatography was performed by employing either a 10 ft x 118 in. stainless steel column packed with 4% OV-101 on 8Ol100 mesh Chromosorb GAW or a 3 ft x 1/8 in. stainless steel column packed with 3% Dexsil300 on 100/120 mesh Chromosorb WAW and using a programming rate of 8 "Clmin from 35 to 300 "C. Thermal gravimetric analyses (TGA) were carried out under reduced pressure (0.6-0.45 mmHg)
from room temperature to 550 "C at 10 "Clmin with a Du Pont 990/951 system. Vacuum line techniques were utilized where applicable. Kinematic viscosities were determined a t 40 and 100 "C per ASTM method D445, using Cannon-Manning Semimicro Viscometers. Materials. Hexachloroplatinic acid (H2PtC16),octylmagnesium bromide, methyllithium, trichlorosilane, 1,3-butadiene, and 1,5-hexadienewere purchased from Aldrich Chemical Company, Milwaukee, WI, and used as received. Dichlorosilane was purchased from Petrarch Systems. Di(6-n-hexenyl)dichlorosilane, ClzSi(C4HsCH=CH&. Dichlorosilane (9.1 g, 90.1 mmol) was condensed in vacuo at -196 "C onto a mixture of 1,5hexadiene (86 g, 1.05 mol) and hexachloroplatinic acid (57 mg, 0.14 mmol) in a 500 mL ampule. After sealing the reaction mixture was kept in an ice bath for 5 h and then at room temperature for 183 h. Subsequently, the excess of 1,5-hexadiene (75 g, 95% expected recovery) was removed and the residue (19.8 g) distilled, giving ClzSi[(CH2)4CH=CHzIz (8.6 g, 36% yield, purity >98%): bp 80-85 "Cl0.001 mmHg; IR (capillary film, cm-') 3078 (m), 2929 (s), 2860 (m), 1640 (m), 1455 (m), 1438 (m), 1400 (w), 1376 (w), 1345 (w), 1255 (w), 1180 (w), 995 (m), 965 (m), 910 (s), 850 (w), 790 (m), 745 (m), 688 (m); mass spectrum (70 eV) mle (relative intensity, ion) (only 35Clions listed) 264 (26.7%,M),194 (16.7%, Si(C6Hl&), 181 (97.5%, M - C6Hll), 153 (40.5%, C12S~CH~CHZCH-CH~), 99 (33.3%, C12SiH), 55 (base, C4H7). The major byproduct was the isomeric mixture of
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C~ZSICHZCH~CH~CH~CHCH~ and C~ZSICHZCH~CH~CHCH2CH3, (7.1 g, 43% yield) produced in the ratio of 3 to 1: IR (capillary film, cm-l) 2951 (s), 2928 (SI, 2871 (s), 1460 (SI, 1380 (w), 1338 (vw), 1310 (vw), 1260 (m), 1200 (vw), 1165 (w), 1096 (m), 1068 (m), 1048 (m), 1020 (m), 1015 (m), 988 (m), 960 (w), 918 (w), 875 (w), 850 (vw),
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800 (m), 760 (m), 698 (SI, 664 (SI, 640 (m). C12SiCH2CH2-
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CHzCH2CHCH3: mass spectrum (70 eV) mle (relative intensity, ion) (only 35Clions listed) 182 (78.9%,M),167 (38.9%,M - CH3), 154 (16.1%,M - C2H4), 140 (99.1%, M - C3H6), 112 (40.2%, SiC121, 55 (base, C4H7). C ~ ~ S I C H ~ C H ~ C H ~ C H C mass H ~ C spectrum H~: (70 eV) mle (relative intensity, ion) (only 35Clions listed) 182 (96.9%, M), 167 (57.6%, M - CH3), 154 (57.9%, M -
Q888-5885/95/2634-1387$09.O0/0 0 1995 American Chemical Society
1388 Ind. Eng. Chem. Res., Vol. 34,No. 4,1995 C2H4), 153 (43.7%,M - C2H5), 112 (43.9%,SiCld, 55 (base, C4H7). Bis[6-(trichlorosilyl)hexylldichlorosilane, ClzSi(10.6g, 40 "01) [ ( c H ~ ) ~ S i c l ~C12Si[(CH2)4CH=CH212 ]2. was sealed in vacuo in a 100 mL ampule with trichlorosilane (22g, 162 mmol) and hexachloroplatinic acid (10 mg, 0.024 mmol). The reaction mixture was kept at room temperature overnight and then a t 55 "C for 26 h. To avoid the initial exothermic reaction, ice cooling was necessary in the beginning. After opening t o the vacuum system HSiCl3 (11.5g, 85 mmol, quantitative recovery) was removed; the residue (20.1g, 94% yield, punty 85%) exhibited a single GC peak showing absence of isomerization. Distillation gave 13.4g (63% yield) of the product: bp 160-165 "Cl0.001 mmHg; IR (capillary film cm-l) 2931 (s), 2860 (m), 1460 (m), 1402 (w), 1380 (w), 1346 (vw), 1260 (vw),1190 (w), 1160 (w), 1085 (w), 1035 (w), 1000 (w), 965 (vw),895 (w),832 (w), 764 (m), 690 (s); mass spectrum (70 eV) mle (relative intensity, ion) (only 35C1 ions listed) 497 (5.1%,M - Cl), 315 (90.3%,M - C13SiC&12), 216 (47.2%,C13SiC6H11). Bis[6-( trimethylsily1)-n-hexylldimethylsilane, ( C H ~ ) ~ S ~ [ ( C H ~ ) S S ~ ( CTo H )methyllithium ~]~. (100 mL, 1.5 M in ether) at 0 "C was added ClzSi[(CH2)6Sic1312 (4.8g, 9.0 mmol). The resulting mixture wae stirred a t room temperature for 21 h and then at 50 "C for 3.5 h. After cooling and hydrolysis with 2 N hydrochloric acid, followed by washing with water, drying over MgS04, and evaporation of ether, the distillation of the residue gave the product (3.0g, 90% yield, purity 99%): bp 110-112 "Cl0.001 mmHg; IR (capillary film, cm-l) 2952 (s), 2920 (s), 2852 (s), 1460 (w), 1410 (w), 1374 (vw), 1337 (vw),1290 (vw),1247 (s), 1185 (vw),1150 (vw),1082 (vw),1040 (vw),1010 (vw), 984 (vw),900 (w), 860 (s), 833 (s), 758 (m),690 (m);mass spectrum (70eV) mle (relative intensity, ion) 372 (5.5%, M), 215 (40.0%,M - C6H12Si(CH3)3),142 (58.2%,CsH12Si(CH&), 127 (base, C6H&iCH3), 73 (95.8%,Si(CH3)3), 59 (68.1%,HSi(CH&; reduced-pressure TGA weight loss onset 40 "C, 50% weight loss 104 "C; viscosity: 40 "C 8.74 cSt, 100 "C 2.46 cSt. Bis[6-(trioctylsilyl)-n-hexylldioctylsilane,(nCeHl7)2Si[(CHz)eSi(n-CsH17)312. At room temperature to n-CsH17MgBr (30mL, 2 M in tetrahydrofuran) was The resultadded ClzSi[(CH2)6SiC1312(2.9g, 5.4"01). ing mixture was refluxed for 7 days under nitrogen bypass. Subsequently, it was cooled in ice-water and hydrochloric acid (60 mL, 2 N) was added. Following extraction with ether, washing with water, and drying over anhydrous MgS04 (after solvent removal) 6.1 g of crude product was obtained. It was filtered through a column (2cm x 23 cm) of basic alumina (23g), heated in vacuo at 220 "C to give 4.0 g (64.5% yield, purity > 99%)of (n-CeH17)2Si[(CH2)sSi(n-CsH17)31~; Mw: calcd 1156,found 1140;IR (capillary film, cm-l) 2950 (s), 2914 (vs), 2848 (s), 1460 (m), 1410 (w), 1376 (w), 1335 (vw), 1300 (vw),1250 (vw),1224 (vw),1200 (w), 1172 (w), 1105 (w), 1075 (vw),1005 (w), 910 (vw),830 (w), 750 (m), 715 (m);reduced-pressure TGA weight loss onset 255 "C, 50% weight loss 334 "C; viscosity: 40 "C 89.7 cSt, 100 "C 14.3 cSt. Di(4-butenyl)dichlorosilane, C12Si(CH2CH2CH=CH&. Into a 200 mL ampule equipped with a Teflodglass stopcock and containing H2PtCl6 (100mg) were condensed at -196 "C (using a vacuum line assembly) HzSiC12 (27.72g, 0.274mol) and 1,3-butadiene (45.3g, 0.833 mol). The ampule was then closed,
removed from the vacuum system, and allowed t o reach room temperature overnight. This was followed by heating at 40-45 "C for 7 days. Subsequently, the ampule was again attached to the vacuum system and cooled to -196 "C and volatiles were distilled from the warming trap through a trap held at -29 "C into a -196 "C cooled trap. The residue left in the original ampule was combined with the -29 "C fraction, giving 38.38g of material. The product was shown by GC to consist
m
mainly of the cyclic compound C ~ ~ S I C H ~ C H ~ C H ~ C H ~ ('60%): mass spectrum (70eV) mle (relative intensity, ion) (only 35Clions listed) 154 (47.3%,M), 126 (base, M - CZH~), 119 (45.2%,M - Cl), 113 (56%,M - C3H5), 98 (61.5%,SiC12). Di(4-buteny1)dichlorosilaneamounted t o
