E. D. WHITNEY,R . 0.MACLAREN, T. J. HURLEY,A N D
4340
[CONTRIBUTION FROM
THE
c. E. FOGLE
Vol. 86
ORGAKICS DIVISIOS,O L I S MATHIESON CHEMICAL CORPORATION, NEW HAVEK,COSSECTICUT]
Preparation of Nitrosyl Tetrafluorochlorate' BY E.
DO'#
~VHITNEY, RICHARD 0.MACLAREN, THOMAS J. HURLEY,AND
CHaRLES
E. FOGLE
RECEIVED M A Y7, 1964 i\ new compound, nitrosyl tetrafluorochiorate, SOCIF4, has been prepared from nitrosyl fluoride, O:W, and chlorine trifluoride a t temperatures below 0'. T h e material is a white, crystalline solid and a powerful oxidizing agent, igniting on contact or reacting explosively with a variety of organic materials. Dissociation pressure measurements give for the enthalpy of fortnation of SOClFa a value of J H f " (298'K.I = -68.6 kcal./mole. Reaction between O N F and bromine pentafluoride a t 0" may have produced nitrosyl hexafluorobrotnate, SORrFs. Attempts to prepare nitryl tetrafluorochlorate, K02CIFa, and nitryl hexafluorobromate, K02BrF6, by reaction of nitryl fluoride, OnNF, with ClF3 or BrFj, respectively, were unsuccessful.
Introduction Studies on the interaction of nitrosyl and nitryl fluorides with halogen fluorides have led to the preparation of several new and novel powerful fluorinating agents. Woolfz in 1950 postulated the existence of nitrosyl tetrafluorobromate, NOBrF4, resulting from the reaction between bromine trifluoride and nitrosyl fluoride. Chretien and Bouy3 later prepared the material by reaction of O N F and BrF3,or by the interaction of X O and BrF3 a t 20'. Nitrosyl tetrafluorobromate is a white solid (d 2.85 g., c ~ I . which ~) reacts violently with cold water and forms nitrosyl hexafluorosilicate, (NO)zSiFe, when treated with silicon tetrafluoride. BriOBrF,
+ SiF, --+(S0)zSiFe + 2RrF3
(1)
Woolf and E m e l e ~ sas , ~ well as Aynsley, Hetherington, and Robinson,j observed that when nitryl fluoride, O&F, was passed into bromine trifluoride, the BrF3 became yellow and quite viscous. Although the above investigators were unable to recover a solid product from the BrF3 solution, it was believed that nitryl tetrafluorobrotnate. XOzBrF4, had been formed, the yellow color being due to the presence of the nitryl (NOz+) ion. Xynsley, et a!.,did succeed, however, in synthesizing and isolating nitryl hexafluoroiodate, NOzIF6. T o date, no other nitrosyl or nitryl derivative of the halogen fluorides has been reported in the literature. Bases of the type MC1F4 and MBrF6, where M may be cesium, rubidium, or potassium, have been prepared. The tetrafluorohalates CsCIF4, RbC1F4, and KClF4 have been prepared both through direct reaction of elementary fluorine with the corresponding alkali metal halides6-10 and as the result of solvolysis reactions in chlorine trifluoride." Evidence for the existence of the hexafluorobromate ion, BrF6-, has been presented by Muetterties'* in the apparent synthesis of CsBrFs from CsF and BrF5. In addition to Cs, I ! T h i s work was supported by the Advanced Research Projects Agency and monitored by t h e Bureau of Nyaval Weapons, D e p a r t m e n t of t h e K avy, C o n t r a c t NOrd-18210. (21 A A Wooif, J . Chem. Soc., 1053 (1950). 1 A Chretien a n d P. Bouy, Comfit r e n d . , 246, 2493 (1958!. Woolf a n d H . J . Emeleus, J . Chenr. S O L . ,I050 (1950). A j n s l e y . G. I I e t h e r i n g t o n . and P. L. Robinson, ibid., 1119
BrF6. the bases RbBrF6 and KBrF6 have been prepared by Whitney, P t al , I 1 oza solvolysis reactions of the corresponding alkali metal fluoride in bromine pentafluoride. In this paper are reported the synthesis and isolation of a new nitrosyl polyhalide, nitrosyl terrafluorochlorate, KOClF4.formed vza the solvolysis reaction of O K F in chlorine trifluoride Some thermodynamic data for the compound are also given Experimental Materials.-Chlorine trifluoride and nitric oxide, both of reported 995'; purity, were obtained from the Matheson Co. Purification of CIF3 to remove traces of H F was accomplished by allowing the material to distil under vacuum through a bed of N a F pellets maintained a t 100" in a Monel pipe which was heated by means of a Fisher combustion tube furnace. The ClFl was then fractionated under vacuum to remove traces of F?, (211, and CIF. Fractionation was accomplishetl by a series of trap-to-trap distillations a t - 78" followed by collection of thc C1F3 in a trap a t 0 " . Elemental F?, obtained from Pennsalt Chemicals Corp., was passed through SaF pellets a t 100" prior t o use. Sjtrosyl fluoride was prepared after the method of Rrauer.Ia Elemental F?, a t a rate of 31 tnl./min., and S O , a t a rate of 65 ml./min., were passed into one end of a 1-in. diameter Monel tube. Slight external heating of the metal tube was required to initiate the reaction, after which the formation of O S F was selfsustaining and proceeded smoothly. The nitrosyl fluoride was collected i n nickel traps maintained a t - 120' by inearls of melting ethyl bromide baths. Over a period of 5 h r . , 31.6 g. (O.fi4S mole) of O S F was obtained corresponding to a n 8 0 ' ; yield based upon Fa consumed. Comparison of the infrared spectrum of this material with the spectrum of O S F a5 given by ii'oltz, et d . , I 5 indicated that the product was reasonably pure, containing only small amounts of NO2 and 0 2 S F . Total impurities were estimated to be approximately 2 mole ?>. Kitryl fluoride, O s S F , was coiivenieiitly prepared by the method of Xynsley, ef n1.j A stream of F? a t approximately 4 g./hr. diluted with SZ(1 : 1 by volume) was passed over 50 g. of dry reagent grade S a S O ? in a Pyrex tube a t rnom temperature. As a precautionary measure the tube containing the sodium nitrite was flamed out immediately before use. Good yields of OsNF were obtained a t low F2 flow rates. If the flow of fluorine gas was excessive a yellow flame appeared over the bed of S a x 0 2 and considerable attack on the Pyrex tube occurred. The gaseous product, consisting of nitryl fluoride contaminated with nitrogen dioxide and pxess fluorine, was passed through nickel traps cooled to -119' by means of melting ethyl bromide to collect O ? S F and SO2. Lnreacted F1 passed through the cold traps t o the vent. The product was separated froni SO2by fractionation under vacuum through several traps maintained at - 88' by melting CCI? baths. The nitryl fluoride w a s stored a t Dry Ice temperature in nickel bombs fitted with Monel needle valves for
~9I, B . Asprey, J . L . Margrave. a n d hf. E . Silverthorn, J A m C h e m qiic
. 83, 2g2.5 11961).
, 101 D . H.Kelly,
B . P o s t , a n d K 15' ?irason. t b i d . , 86, 307 (1963). : i i ) E D . W h i t n e y , R 0 . M a c L a r e n . C . E . Fogle, and T. J. Hurley, thzci , 8 6 , ?58X (1964: 8 1 2 , I < , 1; l l u e t t e r t i e s . "Advances in t h e Chemistry of t h e Coordination C o m p o u n d s . ' S Kirschner. Ed , T h e l f a c m i l l a n Co , S e w Yoi-k, S . Y., 1961, p 514
(13) For t h e recal-d, t h e reported preparation of CsBs-P0by Sluettel-tics i n 1961 should be noted. This work super3edes t h e repoi-ted iynthesiq r i l the bases M B r F s described in ref. 11. (14) G. Brauer. "Handbuch der Praparativen .anal-ganischen Chernie," I' E n k e . S t u t t g a r t . 1951. : l i ! P. J . H . \\:oltz, E A . Jones. and A . H . Sielsen, J . L ' h z m . Ph,s , 20, 378 (1952).
PREPARATION OF NITROSYL TETRAFLUOROCHLORATE
Oct. 20, 1964
use in the exploratory synthesis experiments discussed a t the conclusion of this paper. Apparatus.-Due to the reactive nature of the compounds handled in this work, experiments were conducted in a general purpose vacuum system in order t o exclude air and moisture. T h e system consisted of both Pyrex and metal sections, the sections being joined by means of a copper to Pyrex N o . 774 (Housekeeper) seal. The glass portion of the apparatus consisted of a nitrogen gas drying column, a mercury manometer, a three-way stopcock which was used for either opening the system t o the vacuum pump or introducing nitrogen into the apparatus, and a liquid nitrogen cooled trap. The trap served to protect the mercury manometer and Duo-Seal pump from accidental attack by halogen fluoride vapors. The metal portion of the equipment was constructed of 0.25-in. 0.d. copper tubing, Hoke miniature forged Monel needle valves equipped with Teflon packing, and Monel traps. Silver-soldered connections were used on the traps and reactors, and flared connections in the rest of the apparatus. Steel cylinders containing C1F3 were attached to the system through the H F absorber. A thin layer of Teflon “T-Film” thread compound16was used on all threaded connections. Pressures were measured on Helicoid gauges equipped with stainless steel Bourdon tubes operating in the range 30 in. to 30 p.s.i. pressure. Each part of the apparatus was rigorously cleaned and carefully dried before assembly. In the production of O S F , F? and S O gas flows were measured with calibrated Fisher-Porter precision bore Flowrators with stainless steel floats. Polyethylene tubing was used for all metal t o glass connections. OlVF was stored in Hoke Type 304 stainless steel cylinders equipped with Monel needle valves. Synthesis of KOC1F4 was conducted in 500-ml. polyethylene reactors fitted with threaded caps, Monel needle valves, and flared connections. Thermal decomposition studies were performed in nickel tubes, 22-mm. diameter, 150 m m . long, threaded a t the top, and connected through Hoke Monel needle valves t o the general purpose metal vacuum line. Dissociation pressures were measured with the Helicoid gauges described above. A special infrared cell was constructed for this work. The cell body was machined from nickel bar stock. The cell windows were calcium fluoride disks obtained from the Perkin-Elmer Corp. The windows were sealed to the cell body by means of carefully machined Teflon “0” rings and a paste prepared from “T-Film,” Teflon thread compound, and Kel-F grease. Hoke Monel needle valves and Imperial brass flared fittings were used in filling and evacuating the cell. Infrared data were’obtained on a Perkin-Elmer double beam Model 21 infrared spectrophotometer equipped with sodium chloride optics. Procedure.-Sitrosyl tetrafluorochlorate was very conveniently prepared by condensing CIFBand O N F directly into the 500ml. polyethylene reactor a t -78”. The amount of ClFI and O N F employed in the synthesis reaction was determined from the measured volume and known density of the reactants. Kitrosy1 fluoride was always employed in a slight molar excess. Allowing the reactor and its contents to reach -25’ under vacuum was found sufficient to remove unreacted O S F . Material remaining in the reactor a t -25’ was a white crystalline solid, stable only a t low temperatures (see Table I ) .
TABLE I DISSOCIATION VAPORPRESSURES FOR NOClF, Pressure, a t m . Increasing t e m p . Decreasing t e m p .
7 -
Temp.,
O K .
213 223 233 243 253 263 2 73 283
0.020 0.044 0 088 0.173 0.340
0.092 0.177 0.347
0.701 1.37 3.10
In spite of the relative instability of this material, it could be analyzed by quickly transferring a portion of the solid t o a small polyethylene container, then into a Parr bomb for sodium peroxide fusion, followed by standard analytical techniques. The above operations were performed in a drybox under a NS atmosphere with the S O C l F 4 ,polyethylene containers, and miscellaneous handling equipment cooled t o -78 by means of Dry Ice. (16) Eco Engineering Co.. Newark, ? J i ,
4341
O r
I
-3.0
-
L
4.0 3.40
I
I
3.60
3.80
I 4.00 IO’IT
I 4.20
I 4.40
Ih
J
4.60 , 4.80
(OK-’)
Fig. 1.-Equilibrium dissociation pressures for NOClFd vs. reciprocal temperature: open circles, increasing temperature measurements; closed circles, decreasing temperature measurements.
Results and Discussion The reaction between ONF and C1F3at‘ low temperatures led to the formation of a white solid product. Anal. Calcd. for NOC1F4: N , 9.90; C1, 25.1; F, 53.7. Found: N , 9.44 0.24; C1, 21.5 f 0.1; F, 54.2 f 0.1. The white solid was found to be a powerful oxidizing agent, reacting violently with water and explosively with organic solvents such as ether and ethanol. The material ignited paper on contact. I n Table I are given some equilibrium dissociation pressures for NOClF,. In Fig. 1, equilibrium dissociation pressures for NOClF, are plotted vs. reciprocal temperature. From the slope of this curve, a heat of reaction of AH = 15.8 kcal./mole was determined for the reaction
*
hTOClFi(c)
CIFdg)
+ OKF(g)
At the conclusion of a typical decomposition study, the decomposition products were again cooled to - 78” and the resulting solid analyzed. Found: N , 9.03 + 0.23 ; C1, 20.7 f 0.1 ; F, 54.7 f 0.2. This is considered a good demonstration of the reversibility of reaction 2. The heat of formation of ClF3(g) is AHfo298 = -37.0 kcal./mole. l7 The standard enthalpy of formation of ONF has been given by Johnston and BertinIs as AHfo2ss = -15.8 kcal./mole. Accepting the above figures the following standard enthalpy of formation of nitrosyl tetrafluorochlorate was obtained : AHfo298 = -68.6 kcal./mole or -485 cal./g. The following Born-Haber cycle was used to determine the lattice energy of nitrosyl tetrafluorochlorate. (17) National Bureau bf Standards Circular 500, U. S Government Printing Office, Washington, D. C., Feb. 1, 1952. (18) H. S. Johnston and H . J. B e r t h , J r . , J . A m . Chem. S O L . ,81, 6402
(1059).
E.D. WHITNEY,R. 0. MACLAREN, T. J. HURLEY, AND C. E. FOGLE
4342
kF
F (9)
- A HfoNOCIF4(c)
-AHf'NO(g)
1.
AHf'ClFdg)
V
1
-AHf'F(g)
Vol. 86
From the above, A F = 0 at 200°K. Considering the several assumptions made in the above calculations, the thermodynamically predicted spontaneity of the reaction at temperatures below -73" is in good agreement with the equilibrium dissociation vapor pressure of NOClF, shown in Table I . I t is, of course, possible that nitrosyl tetrafluorochlorate may be a molecular complex, F3Cl.ONF, a covalent compound, or (we presume) an ionic nitrosyl salt of the hypothetical acid, HC1F4, ;.e., NOfCIF*-. The following proposed scheme for the reaction between O K F and CIF3 is similar to the mechanism proposed by Rogers and Katz2j for the exchange of fluorine between C1F3 and H F , i.e.
.It
+I
ON
The proposed intermediate molecular complex (I) in the formation of NOClF: is consistent with the ON
l7
I
II
8i . F- 1-F & F'
hypothesis put forward by Rogers and Katz that the exchange of fluorine atoms between CIFa and H F proceeds through formation of intermediate complexes of type 11. Attempted Preparation of Nitrosyl Hexafluorobromate (NOBrF6), Nitryl Tetrafluorochlorate (N02C1F4), and Nitryl Hexafluorobromate (N02BrF6).-Following the experimental procedure outlined above for the formation of nitrosyl tetrafluorochlorate, attempts were made to form NOBrF6 from ONF and BrFj, and N0zClF4 and X02BrF6 from OzNF and C1F3 or BrF5, respectively. When pure O X F and BrFj were mixed a t -23') no reaction was observed. Interestingly enough, however, when the experiment was repeated in the presence of a small amount of KOCIF?, a white solid product was formed. The material was found to be very stable, however, and chemical analyses and dissociation pressure measurements did not yield reproducible results. Attempts to cause nitryl fluoride to react with either bromine pentafluoride or chlorine trifluoride a t low temperatures were unsuccessful. Indeed, it was observed t h a t the combined vapor pressures of the systems OzNF CIFB and 0 2 N F -I- BrFj always exhibited positive deviations from Raoult's law.
+
(26) M. T. Rogers a n d J . J. K a t z , J. A m . Chem. Soc., 74, 1375 (19523
