DISILANYL IODIDE AND BIS-DISILANYL ETHER
May 5, 1960
every detail t o the formation of [(CH3)2PBH2]3from (CH& PH.BH2.4 Proof of the Trimer Formula.-A 43.7 mg. sample of the substance conjectured t o be (C4HsPBH& gave a 0.145’ lowering of the m.p. of 5.1836 g. of benzene, indicating the mol. wt. to be 298 (calcd., 299.8). An analysis by the Simmons-Robertson methods gave 31.1% P (calcd., 31.0).
[CONTRIBUTION FROM
THE JOHN
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These results, taken with knowledge of the source and properties of the compound, leave no doubt of the formula (C4HaPBH~)3. ( 8 ) W. R.Simmons and J. H. Robertson, A n a l . Chem., 22, 294, 1177
(I950).
Los ANGELES7, CALIFORNIA
HARRISON LABORATORY OF CHEMISTRY, UNIVERSITY OF PENNSYLVANIA]
The Preparation and Properties of Disilanyl Iodide and Bis-disilanyl Ether’ B Y LAIRDG. L. WARD AND ALANG. MACDIARMID RECEIVED AUGUST10, 1959 The interaction a t room temperature of SizHs and HI in the presence of aluminum iodide catalyst has yielded disilanyl iodide, SiHaSiHd, which is hydrolyzed instantaneously to give good yields of bis-disilanyl ether, (SiH3SiH2)20. The physical properties and the thermal stability of these compounds have been determined.
During recent years much interest has been shown in simple compounds containing the SiHa or “silyl” group.2-7 These may be regarded as the silicon analogs of methyl compounds. Similarly, compounds containing the SiHSSiH2 or “disilanyl” groupS may be regarded as the silicon analogs of ethyl compounds. The only disilanyl compounds previously reported are SiHISiH,Cl, SiH3SiHzBrg,lo and (SiH&H&O,$ none of which have ever been isolated in the pure state. In the case of the chloride and the bromide, isolation and characterization has not been possible due to the ease with which they so readily disproportionate according to the equation 2SiHaSiH2X -+-SipHX2 SiZHe (1) Stock and Somieski were able to obtain the ether only as a dilute solution in benzene from which final traces of water were not removed. The present paper describes the preparation and properties of pure disilanyl iodide, SiHaSiH21, and pure bis-disilanyl ether, (SiH3SiH2)20.
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Experimental Apparatus.-All work was carried out in a Pyrex glass vacuum system. Stopcocks were lubricated with Apiezon N grease in preference to silicone grease in order to eliminate the possibility of foreign silicon compounds appearing through attack on the grease by the substances handled. Unless otherwise indicated, all pressure readings (as in mol. wt. determinations) were made with a glass bourdon gauge in order t o eliminate contamination and possible reaction of compourids with mercury. Melting points were determined by a magnetic plunger technique.Il (1) This report is based on portions of a thesiw to he submitted by Laird G. L. Ward to the Graduate School of the University of Pennsylvania in partial fulfillment of the requirements for the degree of Doctor of Philosophy. (2) A. G. MacDiarmid, Quart. Reo., X , 208 (1956). (3) B. J. Aylett, J . Inorg. b Nuclear Ckcm , 2, 325 (1956). (4) G. Fritz, Z . anorg. Chem., 280, 332 (1955). ( 5 ) W. A. Kriner, A. G. MacDiarmid and E. C. Evers, THISJOUR80, 1546 (1958). (6) E. C. Evers, W. 0. Freitag, J N . Keith, W. A. Kriner, A. G.
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MacDiarmid and S. Sujishi, ibid., 81, 4493 (1959). (7) E. C. Evers, W. 0. Freitag, W. A. Kriner, A. G. MacDiarmid and S. Sujishi, J . Inorg. 6’Nuclear Chem., in press. (8) “Nomenclature of Silicon Compounds-Committee of the American Chemical Society,” Chem. and Eng. News, 24, 1233 (1946). (9) A. Stock and C. Somieski, Bcr.. 63, 759 (1920). (10) J. M. Gamboa, Analrs real sot. espaii. 5s. y quim , 46B, 699 (1960); Chcm. Abs., 49, 6766 (1955).
All temperatures below 0’ were measured by an ironconstantan thermocouple, standardized by the XationaJ Bureau of Standards. Temperatures betweet 0 and 100 were measured with either a thermometer calibrated by the National Bureau of Standards or with a thermometer standardized in this Laboratory.I2 In the use of these thermometers, stem corrections were applied where they were significant .I2 Disilane.-This was obtained by the reduction of hexachlorodisilane in di-n-butyl ether with lithium aluminum hydrider3 in yields ranging from 30-45y0 based on the amount of hexachlorodisilane used. The purity of the disilane was checked by determining its mol. wt. (found, 62.5; calcd., 62.2) and its vapor pressure a t - 64.0” (found, 66.6 mm.; lit. value,I4 69.0 mm.). Its infrared spectrum was identical to published infrared spectra of the pure compound . l a J 5 Hydrogen Iodide.-This reagent was prepared from red phosphorus, pulverized iodine and water and purified by distillation from a trap a t - 96’. Aluminum Iodide.-This material was prepared from the elements in boiling benzenel6 and after distillation at atmospheric pressure, was purified for use as a catalyst by sublimation in vacuo. Disilanyl Iodide, SiH3SiH21, Synthesis.-This was prepared by thereaction for 2.5 hr. a t room temperature of disilane (0.123 mole) and hydrogen iodide (0.04 mole) in a 5 liter round-bottom flask containing aluminum iodide (0.4 g.) sublimed on t o its inner wall. The hydrogen evolved was pumped away through five traps in series, each a t - 196’. The crude SiH3SiHzI (3.5 g.; 76Y0 yield based on disilane used according to equation 2) was separated from less volatile more highly iodinated materials and from unreacted disilane by condensation in a trap a t - 96’. Purification was effected by repeatedly evaporating the product from a 46’ and condensing it in a trap a t - 78’. The trap a t pure material obtained (mol. wt. found, 192.0;0 calcd., 188.1), exerted a vapor pressure of 9.5 mm. a t 0 , m.p., 86.1 f 0.3’; density, 1.764 g./ml. a t 0”. Disilanyl iodide was stored a t either -78 or -196” in order t o prevent its decomposition. I n the gas phase a t room temperature the rate of disproportionation was SUEciently slow t o permit its manipulation in the vacuum line. Care was taken to exclude traces of mercury or mercury va-
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(11) A. Stock, “The Hydrides of Boron and Silicon,” Cornell University Press, Ithaca, New York, 1933, p. 183. (12) National Bureau of Standards Circular 600, January 8, 1959, “Calibration of Liquid-in-Glass Thermometers,” by James F. Swindells, available from the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D . C. (13) G. W. Bethke and M. K. Wilson, J . Ckcm. Phys., 26, 1107 (1957). (14) A. Stock and C. Somieski, Bcr., 49, 147 (1916); ibid., 62, 726 (1919). (15) H. S. Gutowsky and E. 0. Stejskal, J . Chcm. Phys., 22, 939 (1954). (16) M.G.Voronkov, B. N. Dolgov and N. A. Dmitrieva, Doklady A k a d . N o u k S.S S R . , 84, 959 (1952).
LAIRDG. L. WARDAND ALANG. MACDIARMID
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por with which it reacts readily. Unlike its lower homolog silyl, iodide (SiHJ), SiH3SiHzI is spontaneously inflammable In a n . Analysis.-Disilanyl iodide (0.2282 g.; 1.198 mmole; vapor pressure a t 0", 9.5 mm.), upon hydrolysis in 35y0 aqueous sodium hydroxide, yielded after three days, 160.1 ml. of hydrogen (calcd., 160.8 ml.). The iodine was determined volumetrically by oxidation t o IC1 with KI0317: I found, 67.70%; calcd., 67.600j0. Silicon was determined upon the combined residues, as SiO2'8: Si found, 29.92%; calcd., 29.80%. Another sample (0.2491 g., vapor pressure a t O0,found 9.3 mm.) contained I, 68.25a/,; Si, 29.60%. Thermal Stability. (a) Decomposition at Oo.-The gapor pressure of a sample of SiHSSiHJ, maintained a t 0 , increased steadily from an initial value of 10.0 mm., to a value of 12.7 mm. after 255 minutes. ( b ) Decomposition at Room Temperature .-SiH3SiH$ (0.4148 g.; vapor pressure a t Oo, 10.1 mm.) was stored in the dark in a Pyrex tube (15 ml.) for 57 days. Hydrogen (6.45 ml.) was formed, together with SizHB (0.0532 g., mol. wt. found, 65.6; calcd., 62.2), SiHl (0.01-0.02 g.; identified by infrared spectrum)'S and impure SiH3SiHd (0.0733 g.). A non-volatile viscous liquid remained in the reaction tube. ( c ) Decomposition at 9O0.--SiH3SiH*I (0.330 g.; vapor 1" for 5 hr. pressure a t Oo, 9.5 mm.), was heated a t 90 in a sealed Pyrex tube (15 ml.). The products isolated were hydrogen (6.66 ml.), Si2H6 contaminated with a trace of SiHc (0.0342 g.; mol. wt. found, 61.9, calcd., 62.2; confirmed by infrared ~ p e c t r u m ~ ~SiHSSiHJ ~ ' ~ ) , (0.0806 g.; vapor pressure a t O0, 9.0 mm.) and a considerably less volatile product (0.1214 g.) retained as long clear crystalline needles a t -46". A white involatile product remained in the reaction tube. Vapor Pressure .--An all-glass immersible tensimeter sensitive to h 0 . 2 mm. difference in pressure, involving no ground glass joints or stopcocks, was employed. The constant temDerature bath was controlled t o =k0.05°.20 Vapor presswes in the range 1.3 t o 90.1' are represented by 6.5843 (Table I ) . the equation log E',, = - 1767.9/T
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TABLE I THEVAPORPRESSURE OF DISILANYL IODIDE^ Temp., OC.
Vap. press., cm. Ohsd. Calcd.
Temp., OC.
Vap. press., cm. Obsd. Calcd.
1.3 1.43 1.39 76.9 36.86' 34.25 5.3 1.72 1.72 5i 9 22.04h 17.64 11.2 2.29 2.33 45.9 16.0@ 11.08 20.5 3.i2 3.67 20.8 8.28' 3.72 30.1 5.69 5.69 2.8 5.34* 1.51 39.8 8.70 8 . 6 2 -196.0 0.67* ... 50.0 13.01 12.93 0.0 1.70" 1.30 60.4 19.15 19.27 S0.2 38.21 38.17 90.1 51.83 52.25 a Duration of the determillation, approximately 9 hr. * Pressure observed on decreasing the temperature. e Vapor pressure of the residue a t 0' after removal of the non-condcnsable gas. The extrapolated boiling poiiit is 102.8". The molar heat of vaporization is calculated as 8087 cal. mole-' and A second Trouton's constant as 21.5 cal. deg.-l mole-'. experiment, carried out on an independent sample, gave results which were very closely represented by the same equation, giving an extrapolated boiling point of 102.5". The irreversibility of the vapor pressure curve upon decreasing the temperature indicates that some decomposition of the inaterial had occurred. The fact that the curve is reproducible and that it falls both on prints determined a t low temperatures where decnniposition is not extensive and ; t l v i , on points a t high temperatures, indicates that the de(17) "Scott's Standard Methods of Chemical Analysis," N. H. 1:urman. E d . , Vol. I , 5 t h ed., D. Van Nostrand Co., Inc.. 1939. p. 454. (18) Arthur I. Vogel, "A Textbook of Quantitative Inorganic Analysis, Theory and Practice," 2nd Ed., Longmans, Green and Co., London, 1951, p. 503. (19) J. W. Straley m d H. €I. Nielsen, Phys. Rnu., 62, 151 11042). (200) Sargrut 'lhermunitor, Model S , 1.:. €I. Sargent and C o , ChiCagU.
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composition products do not seriously interfere T.vit!i t h e vapor pressure values of the cornpound. Bis-disilanyl Ether, (SiHaSiHz)sO, Synthesis.-Tile hpdrolysis vessel consisted of a tube 3 cm. X 26 cm. with a vacuum stopcock and standard taper joint. At an angle of 15-20' to the main body of this tube, 4 cm. from the shoulder, was fused a side arm 1 cm. X 36 cm. terminated with a second vacuum stopcock. The freeze-drying vessel consisted of a tube 1.2 cm. X 21 cm. long, surrounded 6 cm. from one end by a cup 10 cm. deep and 4.5 cm. in diameter, so as to form a stem 15 cm. long, to the ends of which JTere fused a standard taper cone and socket. Crude disilanyl iodide (6.5 g.; vapor pressure a t O " , 15.0 mm.) was distilled on to 10 ml. of degassed distilled water in the main body of the hydrolysis vessel. Upon thawing, an immediate reaction commenced, there being formed 3 mobile, highly refractive liquid floating on the water and in the water, a white precipitate. Some hydrogen evolution was observed. With nitrogen in the vessel, the contents were transferred to the side arm and the lovc.er layer of water was removed. The ether was freed of much water by yepeatedly distilling from room temperature into a trap a t - 196" (much of the water remaining as ice) and by distilling into the stem of the freeze-drying vessel, melting the ether rapidly and permitting it t o flow into a cooled take-off tube. The water which remained as a ring of ice in the stem was pumped away. Final drying of the liquid ether was effected with P 2 0 5 . Prolonged contact with this drying agent resulted in some decomposition of the ether and in the formation of phosphine. Repeated distillation (with pumping) from a trap a t -46" aia traps a t -96" and -196°,0yielded the pure ether which condensed in the trap a t -96 . The pure material obtained (mol. wt. found, 135.0;' calcd., 138.4) exerted a vapor pressure of 11.4 m y . a t 0 ; m.p., -111.7 zt 0.2'; density, 0.876 g./ml. a t 0 . The yield of (SiHaSiH?)*,Oaccording to equation 3 was 96% based on pure SiH3SiH21taken. Storing in the dark for 16 days a t room temperature in a sealed Pyrex tube produced no change in appearance or vapor pressure. I t did not appear to attack mercury. However, unlike its lower homolog, disiloxane, ( SiH3)20, ( SiH3SiH2)Z0 is spontaueously inflammable in air. Analysis.-(SiHaSiHn)20 (0 .OS92 g., 0.046mniole; vapor pressure a t O', found, 11.6 mm.), upon hydrolysis in 3570 aqueous sodium hydroxide, yielded, after 2.5 days, 173.7 ml. of hydrogen (calcd., 174.0 ml.). Silicon was determined as SiOP: Si found, 81.77,; calcd., 81.2%. Thermal Siability.-(a) (SiH&3iH*)?O(0.0896 g.; x-ap"r pressure a t 0 , 11.6 mm.) was heated for 9 hr. a t 70' in a sealed Pyrex tube (15 ml.). The residue, after removal of the hydrogen (0.36 ml.), exerted a vapor pressure of 12.7 mm. a t 0'. ( b ) (SiHaSiHz)20 (1.0 g.; vapor pressure a t O 0 , 11.5 mm.) was heated slowly over mercury during 4 hr. to 90" then cooled during 2 hr. to 0" in a newly constructed glass apparatus. Slightly impure ether (mol. wt. found, 132.5; calcd., 138.4), remaitled after the removal of the hydrogen (approximately 0.8 ml.). I t cxerted a vapor pressure of 16.7 mm. a t O " , but its infrared spectra a t 29.2 mm. and 4.2 mm. were identical with those of the spectra of the pure compound a t comparable pressures. Considerably less hydrogen (
