PUPP,AND W. E. WHITE 828 J. B. BEAL,JR.,CHRISTIAN
Inorganic Chemistry CONTRIBUTION FROM THE RESEARCH DEPARTMEKT, OZARK-MAHOKING COXPAXY, TrjI.sa, OKLaHonl.4 '74119
The Reaction of Oxygen Difluoride with Some Lewis Acids. The Preparation of Dioxygenyl Salts' BY J. B. REAL, JR., CHRISTIAK PLPP,
AND
TV. E. RHITE
Received June 28, 1968 Both oxygen difluoride and a mixture of oxygen and fluorine react R-ith hsF6 and 8 h F j to give dioxygrnyl salts under moderate pressure and elevated temperature.
Introduction The first detailed investigation of reactions of OF, was made by Ruff., He found that OF, would react so as to introduce either fluorine or oxygen or both into a molecule depending upon the conditions used. I n 1934, Schun-~acher~ studied the kinetics of the thermal decomposition of OF, and concluded that it is decomposed in a first step t o I' and OF * radicals which decoinposed to 02 and F,. I n several photochemical reactions* s it was demonstrated that OF, could react with inorganic compounds as 01: . and F . radicals. Franz and Seuniayr6 investigated similar reactions. Theriiial reactions carried out by Cady' and by Engelbrechts showed that OF2 reacts as a mixture of 02 and F2 a t elevated temperatures. An objective of this work mas to find conditions under which OF, would react as O r + and F- to give products containing an OF+ moiety. The most promising typr of reaction seemed to be that n-hich might be stabilized by some Lewis acids, e.g. OF+ + F- -f BFa
+ OF'BF4-
OF+ salts were not prepared, but dioxygenyl salts were obtained in the AsE', and SbF, reactions. The first dioxygenyl salt was discovered by Bartlett in 1962.9 He found that PtF6was able t o oxidize molecular oxygen to forni OzPtT6. I n 1963, Solomon'" and Young" in indepcndcnt n 01 k rcportcd tho prc paration of OzBF4and OzPF6and 021'T6, 02AsF6,and OzSbI'6, respectively, using 02Fz and the appropriate Lewis acid. (1) This research was supported by the Advmced Research Projects Agency, Washington 25, D. C., and was monitored by t h e Air Force Rocket Propulsion Laboratory, Edwards, Calif., under Contract 40. Al.' 04 (611)-9556. ( 2 ) 0 . Ruff and W. hlenzel, %. A n o ~ y .Aliyem. Chem., 198, 30 (1931). (3j W . Koblita and H. J. Schumacher,2 . Physilc. Chem., 25, 283 (1934). (4) R. Gatti, E , H. Staricco, J. E . Sicrs, and H. J. Schumacher, ibid., 36 (',"), 211 (1963). ( 5 ) R . Gatti, J. E. Ricre, and H. J. Schumacher, abid.,40 ( I l z ) , 127 (1964). (6) G . Frane and 17. Seurnayr, InorQ. Chem., 3, 921 (1964). (7)R. A. Rhein and G . 11. Cady, ibid.,3, 1644 (1964). (8)A . Engelbrecht, E. Xachbaur, and C. Pupp, Monalsh. Chem., 95, 219
(1964:.
(9) 1.Bartlett and D. H. Lohrnann, Proc. Chem. Soc., 115 (1962): J . Chem. Soc., 5 2 5 3 (1963). (10) 1. J . Solomon, R. I. Brabets, R. X. Uenishi, J, N. Keith, and J. hI. hfcDonough, I n o r g . Chem., 3, 457 (1064). (11) A . R. Young, 11, T. Hirata, and S.I. AIorrow, J . Am. Chem. Soc., 86, 20 (1064).
Since it appeared that OF,was behaving as though it were a mixture of oxygen and fluorine, fluorineoxygen mixtures were iiiade to react with AsFj and SbF,. By this simple and convenient route the dioxygenyl salts have been obtained in high yields and purities. These salts have been identified by chemical, infrared, and X-ray analysx. Xtteinpts to prepare dioxygenyl salts from BF3, PF,, SiF4,BrF3, BrFs, and IF5m r e unsuccessful. Discussion Dioxygenyl Hexafluoroarsenate and -antimonate.The first evidence for the formation of a dioxygenyl salt from OF, came from a high-pressure reaction. I n this experiment, OF,and AsFj were allowed to react in an autoclave (3 cm3) a t 200" and 717 atiii. (Pressures were calculated assuining ideality.) The major products were those formed by the reaction of the gases with the reactor. There was a small amount of a material, however, vhich behaved as an oxidizer and reacted vigorously with water with evolution of ozone. The reaction was repeated in a larger reactor (30 cni3) a t 100" and 200 atm. The niole ratio was 1: 1. There was no detectable reaction after 3 days. The temperature was raised t o 200" for a lilic period, when a salt Tyas formed, in a yield of about 40% based on AsFj. The gaseous products were fractionated and found to be O,, F2, and AsF5. The ratio of reactants mas changed to 2 :1 (OF2 : AsFj) and the experiment repeated a t 200" and 200 atm. The yield of salt in this case was approximately SOYc,. Again the gaseous products were fractionated and identified by infrared spectra, iiiolecular weights, or both, as 02,r2.and AsF5,Material balances were determined by P V T relationships and weight differences. The data indicate that the reaction occurred as 40F2
+ 2AsFb
---t
202AsFs
+ 3Fz
I n an attempt to gain an insight as t o the reaction mechanism and in view of the fact that the temperature of 200" was above the decomposition temperature for OFz, an experiment was made using fluorine, oxygen, and AsF; ( l / z : l : l j a t a pressure of about 150 atm. After 5 days a t 200" it was found that 0&FG had formed in 97% yield. A similar yield was obtained a t
Vol. 8, No. 4, April 1969
REACTION OF OXYGEN DIFLUORIDE WITH SOME LEWISACIDS 829
130"; however, a t room temperature only a trace of OzAsFs had formed in 10 days. Similar findings were obtained with SbFs in place of AsFS. It seems that the dioxygenyl salt formation in these reactions involves, primarily, molecular oxygen, fluorine, and the Lewis acid. The following mechanism is consistent with the findings
-OzF *
+
Fz42F. 0 2 F * -+O& * AsF6 -i OzF * AsF6 -iOz'AsFs-
+
The existence of the OzF. radical in OzFz a t low temperatures has been demonstrated by Arkell.12 Thus, the presence of OzF * in OzF, must be significant in the formation of dioxygenyl salts. The i n ~ t a b i l i t y ' ~ of OzFz a t temperature above -80" precludes it as a likely intermediate in the mechanism. Attempts to Prepare Other Dioxygenyl Salts.Attempts were made to extend this reaction to other compounds, particularly SiFd, BF3, PF5, and IF5, and the findings are summarized in Table I. TABLEI REACTIONS OF OF, WITH VARIOUS LEWISACIDS Reactants
+ BF3 OFz + IFK OF, + BrF8 OFz
+ BrFK OFz + SiFa OFz + PFK OF2 + AsFS OF, + SbFs OFn
Temp, O C
Results
L320
OFz decomposed,
L 150
IF? produced
L 200 L 200 150 L 200 b 200 L 200
BrF6 produced No reaction No reaction Small amount of a white solid OzAsFs obtained 02SbFe obtained
no combination with BF8
Infrared Spectra.-The
only absorption observed for
OzAsFs in the range 2-25 p is a t 14.2 p which is characteristic for the AsF6- ion. l 4 , I 5 Spectra of the antimony salt showed absorption a t 15 SbFg.15*16
p,
characteristic of
X-Ray Data.-The X-ray diffraction powder pattern for OnAsFs is in accord with that reported by Young, et al.; however, the pattern obtained for OzSbF6 is significantly different from theirs. Since it appeared likely that OzSbF6and NOSbF6 would be isomorphous, X-ray diffraction powder patterns were made for both salts. These data appear in Table I1 and Table 111. The observed pattern of 02SbF6 agrees quite well with that calculated for a face-centered cubic unit cell, a0 = 10.13 A. The differences in the cell parameters that were reported by Young and by us cannot be explained either by minor impurities or by X-ray technique. The product of Young must have been highly contaminated as was suggested by them. (12) (13) (1959) (14) (15) (16)
A Arkell, J Am Chem Soc , 87, 4057 (1965) A D Kirshenbaum, A V Grosse, and J G Aston, z b z d , SI, 6398
D W A Sharp and A G Sharpe, J Chem SCC, 1855 (1956) L Kolditz and J Wendt, 2 C'lem, 3, 312 (1963) R D. Peacock and D W A Sharp, J . Chem SOC, 2762 (1959)
TABLE I1 DIFFRACTION PATTERN OF OzSbFsa hkl 200 220 222 400
...
420 422 440
600 620 622 444 640 642 820 660
-dv Calcd 5.065 3.581 2.924 2.532
...
2.265 2.068 1.791 1.688 1.602 1.527 1.462 1.405 1.354 1.228 1.194
A---
-4
Obsd 5.092 3.593 2.934 2.533 2.405 2.268 2.067 1.798 1.685 1.600 1.524 1.460 1.402 1.352 1.227 1.193
Ill0 2
8 2
1 1 4 10 6 8 7 7 2 6 9 6 5
hkl 662 840 842 664 844 10,0,0
10,2,0 666 10,4,0 10,4,2 10,4,4
10,6,0 10,6,2 884 12,2,2
Calcd 1.162 1.133 1.105 1.080 1.034 1.013 0.993 0.975 0.941 0.925 0.882 0.869 0.856 0.844 0.822
AObsd 1.160 1.131 1.103 1.077 1.032 1.011 0.992 0.974 0.940 0.924 0.881 0.868 0.856 0.844 0.821
Ill0 2
2 5 2
2 2 7 3 6 4 3 4
8 5 5
"Face-centered cubic unit cell, a, = 10.130A&.
TABLE I11 DIFFRACTION PATTERN OF XOSbFoa -& hkl 200 220 222 400 (41 1) 420 (332) 422 (510) 440
600 620 622 444 640 642 (732) 800
Caicd 5.095 3.603 2.942 2.547 (2.402) 2.279 (2.173) 2.080 (1.999) 1.801 1.698 1.611 1.536 1.471 1.413 1.359 (1.294) 1.274
A-Obsd 5.092 3.598 2.942 2.536 2.402 2.272 2.165 2.074 1.994 1.796 1.693 1.607 1.533 1.469 1.409 1,362 1,290 1.272
-d.
Ill0 2 8 2 1 1 5 2 10 1 7 8 7 6 2 7 9 1 1
GFace-centered cubic unit cell, a,
hkl 820 660 662 840 842 664 844 10.0,o 10,2,0 666 10,4,0 10,4,2 10,4,4 10,6,0
10,8,2 884 12,2,0 12,2,2 =
Calcd1.236 1.201 1.169 1.139 1.112 1.086 1.040 1.019 0,999 0.981 0.946 0.930 0.887 0.874 0.861 0.849 0.838 0.827
A-Obsd 1.234 1.198 1.167 1.138 1.111 1.086 1.039 1.018 0.999 0.980 0.946 0.930 0.887 0.873 0.861 0.849 0838 0.826
IIID 7 6 2 3 3 2 3 3 7 3 7 6 6 7 7 5 4 7
10.190Lh.
Bartlett has reportedg Tc'OSbF6 as having a cubic cell, a0 = 10.193A. This value was in a table comparing cell dimensions of several salts of the general formula A+[BFe-] for which diffraction patterns were not given. We now present the powder pattern in Table I11 which shows NOSbF6 to be a face-centered cubic unit cell in which a0 = 10.19 A. Attempts have been made t o fit the data t o more primitive cells but without success. The extra lines in Table 111, which are identified by parenthetical enclosure, are attributed t o NOzSbFs which is present as an impurity (unpublished data). Experimental Section Pressure Reactions. (a) With OFz.-The least volatile reactant was charged first to the reactor, which was a Hoke 4 HSM-30 Rfonel cylinder rated a t 5000 psi. Then OF, was added by condensing with liquid nitrogen N,(l). (OF, is a highly toxic gas and should be handled in a n adequate fume hood. Before undertaking experiments with OF, it is recommended that one become familiar with the safety precautions described in the product data sheet of the Industrial Chemical Division of Allied Chemical Corp.) The materials were in mole ratios of 1:l or 2 : l (0Fs:Lewis acid). The quantities used were those calculated to give the desired pressure a t a given temperature;
830 STECK,PRESSLEY, STAFFORD, DOBSOA-, ASD SCHAEFFER OF, and AsFb (1:1) a t 200 atin and 200' the cylinder would be charged x5th -0.061 mol of OF, and -0.064 mol of AsFs. The reactor \vas then placed in an oven. After the reaction period the remaining gases were pumped off through traps in Xz(l)folloived by a scrubber containing a KaOH-CaO mixture to protect the pump. The white solid products were removed and handled in a drybox. Yiclds (based on AsFb) varied from 40Yc in the 1 : 1 case to SlyGin the 2 : 1 case a t 200" for 6 days. xere charged to (b) With Oxygen and Fluorine.-Reactants the cylinder as above in the Lewis a c i d : 0 2 : F pratio of l:l:l/,. After 1 week at temperatures in the range of 130-200", a yield of 97-987; of the salt m s realized. Anal. Calcd for 0,AsF8: As, 33.91; F, 51.6. Found: As, 33.56; F, 51.8. Calcd for 02SbF6: Sb, 15.47; F, 42.59. Found: Sb, 45.8; F, 41.3. Analytical Methods. (1) Fluoride.-This ivas steam dist'illed from sulfuric acid at 155". The distillate was buffered to p H 3.1 and titrated with Th(KO:)a using alizarin red S as the indicator. The procedure used was a niodification of that of Killard and \Vinter.17-20 e.g., for
Inorganic Chemistry
elements were reduced t o (2) Antimony and Arsenic.-These the $3 oxidation state vith sulfur and then determined by titration with KBr03.z1,2 2 (3) Infrared Spectra.--A Perkin-Elmer 337 spectrophotometer n as used to recoid ir spectra in the range 2.5-25 p. Spectra of solids were made by using mulls of Kel-F oil between AgCl disks or by using KC1 pellets. Spectra of gases mere made using a 5-em length cell made from 1-in. nickel pipe fitted with a valve. Kindows were 25-mm diameter rolled AgCl and were sealed to the cell with Kel-F 200 wax. (4) X-Ray Powder Patterns.-Samples were transferred to Pyrex capillary tubes and sealed. These operations were made in a drybox. The photographs were made using a GE 143.2-mm camera and Cu KC^ irradiation through a nickel filter.
Acknowledgment.-We acknowledge t,he help of Mr. Karl Schmidt in the experimental work and Dr. V. G. Neadors for consultation and suggestions. Also, we thank Dr. C. Maddin and Mr. R. Van Nordstrand for their help with the X-ray powder patterns.
(17) H . H. Willard and 0. B. Winter, I n d . Eng. Chem., Anal. Ed., 5 , 7 (1933).
(18) K, B. Estill and L. C. Mosier. Anal. Chem., 27, 1669 (1055). (19) H. H. Willard, and C. A. Horton, ibid.,22, 1190 (1950). (20) R. J. Rowley and H.V. Churchill, I n d . Eng. Chem., A n d . E d . , 9, 551 (1937).
CONTRIBUTION FROM CONTRIBUTION No. 1643 FROM
THE
(21) W. F. Hillebrand, G. E. F. Lundell, H . A. Bright, and J. I. Hoffman, Ed., "Applied InoIganic Analysis," 2nd ed, John Wiley & Sons, Inc., New P o r k , S . Y., 1953, pp 273-276. (22) I. hl. Kolthoff and R. Belchtr, E d . , "Volumetric Analysis," Vol 111, Interscienoe Publisheis, Inc., New York, h-.Y . , 1957, pp 501-516.
DEPARTMEKT O F CHEMISTRY A S D THE hI.4TERIALS RESEARCH CENTER, NORTHWESTERN UNIVERSITY, ETANSTOS, ILLINOIS 60201, ABD 47405 DEPARTMENT OF CHEMISTRY, IKDIANA UBIVERSITY,BLOOMINGTON, INDIANA THE
Molecular Beam Mass Spectrum, Pyrolysis, and Structure of Octaborane( 1S)l BY SARA J. STECK,2 GEORGE A. PRESSLEY, JR., F R E D E. STAFFORD, J E R R Y DOBSOS,
BND
RILEY SCHAEFFER
Received June 20, 1968 The molecular beam mass spectrum of octaborane(l8) and the appearance potential of the ion BaHB+ were measured. These measurements support a proposed structure for the compound in which two tetraborane fragments are joined by ri single B-B bond. I n addition, a p) rolysifi study \\as made to determine the nature of the thermal decomposition of this unusual boron hydride; both tetraborane(8) and tetraborane(l0) appear to be formed in the initial steps of the decomposition.
Introduction Reaction of the unstable boron hydride octaborane(18) with hydrogen and with ca,rbon monoxide results in cleavage to tetraborane(l0) and tetraborane carbonyl, r e s p e c t i ~ e l y . ~Formation of these compounds is suggestiye that octaborane(l8) is comprised of two tetraborane(9) units connect,ed by a B-B bond. This structure is one of t w o which are compatible with observed nmr data for the conipound. The second structure is a belt-line icosahedral fragment. (1) Supported by the Atomic Energy Commission, Document S o . C00-114725 (at Northwestern University), and the Kational Science Foundation, Giant KO. G P 4944 (at Indiana University!. (2) Recipient of Public Health Service Fellowship 1-F1-Ghf-29, 815-01A1 from the National Institute of General hIedioal Sciences, 1066-1968. ( 3 ) J. Dobson, D. Gaines, and R. Schaeffer, J. A m . Ciiem. SOC.,87, 4072 (1965).
Neither a crystal structure nor a mass spectrum for octaborane(l8) has been published. Since the ion fragmentation patterns of the two diverse struct'ures that have been proposed for this boron hydride should be distinctly different,,4t6'6the mass spectrum of octaborane(l8) is expected to give evidence for it's structure. Because of the thermal instability of the boron hydrides, pyrolysis of a compound in the roomtemperature inlet or on the hot-ion source of a conven(4) F. 'cv. McLafferty, "Interpretation of Mass Spectra," W. A. Benjamin, Inc., New York, N. Y., 1966. ( 5 ) I. Shapiro, C. 0.Wilson, J. F, Uittei, and Vi.J. Lehmann, Advances in Cheniistry Series, KO.32, AmeIican Chemical Society, Washington, D. C., 1961, p 127. (6) J. F. Ditter, F. J. Gerhart, and R . E. Williams, Advances in Chemistry Series, No. 72, American Chemical Society, Washington, D. C., 1968, p 191.
