390 NOTES
Inorganic Chemistry
form iridium disulfide having the orthorhombic crystal structure of iridium d i ~ e l e n i d e , ~ inJ which part of the iridium may be considered to have the + 3 oxidation state. If the ratio of sulfur t o iridium is increased to nearly 3 : 1, then a pyrite structure is formed6 in which the +3 iridiup is balanced with cation vacancies. At GO kbars, a mixture of sulfur and iridium ( 3 : 1 mole ratio) will react a t 1500” to form the same pyrite structure ( I r S a S )observed by Biltz, et aI.6 (a = 5.62 A). If, however, sulfur and iridium in a 2 : l mole ratio react a t GO kbars and 1500”, then a new pyrite phase is found (IrSI.9) with a = 5.68 A. Powder diffraction patterns obtained from samples having an initial composition with a mole ratio between 2 and 3 which were allowed to react under the same conditions showed the presence of both pyrite phases. Nickel diarsenide crystallizes in an “anomalous” marcasite structure’ which differs from the Jahn-Teller marcasite structure by having minimal angular distortion about the cation octahedra. In this sense the “anomalous” marcasites are like the pyrites ; however, they differ from the pyrites in that the marcasite structure is a less dense packing arrangement. These factors suggest that materials having the ‘ianomalous” marcasite structure might be induced to form the pyrite structure when synthesized under pressure. An intimate mixture of powdered nickel and arsenic in a 1:2.2 mole ratio after reaction a t GO kbars and 1400” was cooled a t pressure to room temperature over a period of 0.5 hr. After the release of the pressure a metallic gray material was obtained which gave the X-ray reflections (Table I) of the cubic pyrite structure, a = 5.77 A. The calculated density, 7.21 g ~ m - may ~ , be compared with the pycnometric density of 7.15 =t 0.10 g emu3. These results suggest that other materials possessing the “anomalous” marcasite structure may also be synthesized in the pyrite arrangement under pressure. TABLE I
L. M. Osika in making the X-ray diffraction patterns and analyses and also helpful discussion with Dr. John S. Kasper. Dr. Lester Bronk performed the thermogravimetric measurement.
CONTRIBUTION FROM THE GESERALELECTRIC RESEARCH AXD DEVELOPMENT CENTER, SCIIENECTADY, NEW YORK
The Formation of the Skutterudite Phase in the Cobalt-Phosphorus System BY RONALD A. MIJXSO~.;~ AND
JOTIN
S. KASPRR
Rereioed August 7 , 1967
Relatively fen7 compounds occur in the skutterudite structure (space group Tkl5(1m3)),but the existence of IrP3 and RhP3 as well as CoSbs and CoAs3in this structure strongly suggests that Cop3 ought to have this arrangement also. Biltz and Heimbrecht,2 however, were unsuccessful in preparing cobalt triphosphide with the skutterudite structure a t low pressures. We have been able to prepare the skutterudite phase of cobalt phosphide by allowing po~vderedcobalt to react with phosphorus in a 3 : 1 mole ratio a t a pressure of 60 kbars and 1400”. Homever, this product also contained another unidentified compound of cobalt and phosphorus. The pure skutterudite phase could be obtained only when the ratio of phosphorus to cobalt was in the vicinity of 4. Chemical analysis of the pure skutterudite phase established the empirical formula CoP3.90 (32.8y0 cobalt). X-Ray reflections using cobalt KCYiron-filtered radiation indicated the bodycentered-cubic structure, a = 7.711 A. The calculated - ~ may be density based on Cop4 is 3.97 g ~ m which compared with the pycnometric density of 4.04 =t0.10 g ~ m - ~ Initial . structure factor calculations indicate agreement between the intensities listed in Table I
SPACING AND ISDEXINC OF THE REFLECTION^ OF
-d
hkl
2.86 2.56 2.34 2.03 -1.98 .. 1.73 1.66 1.59 1.54 1.435 1.285 1.255 1.225 1.174 1,.109
200 2 10 211 220 22 1 311 222 230 32 1 400 420 42 1 332 422 511 ~~~
CUBICKICKELDIARSENIDE~ Intensity -d hkl 1.070 432 w 521 440 600 610 611
w w
1.051 1.019 0.961 0.949 0.936 0.911 0.880 0.870 0.860 0.851
M
0.832
LLI
Y
0.800 0.792 0.785
640 641 552
S
s
w
w
vs W M S
w M
M M M
SPACING AND IXDEXING OF T I ~ EREFLECTIONS
w
-d
M
5.4 3.83 3.12 2.71 2.43 2.23 2.06 1.92 1.81 1.72 1.64 1.57 1.51 1.32 1.285 1.219
w
62 . 0 ~ .
w
533 622 630 631
H
. .
TABLE I
Intensit):
w
n H
w
w
s s
a Copper Kcvl nickel-filtered radiation employed with a Norelco camera of diameter 114.6 mm.
Acknowledgments.-The author wishes to acknowledge the able assistance of R. D. Kieft, J. S. Pirog, and (4) L. B. Barricelli, Acta Cryst., 11, 75 (1958). (5) F. Hulliger, Nafaue, a04, 644 (1964). (6) W. Biltz, J. Laar, P. Ehrlich, and K. Meisel, Z. Anoug. Allgem. Chem., 233, 263 (1937). (7) F. Hulliger and E. Mooser, “Progress in Solid State Chemistry,” Vol. 2, 11. Reiss, Ed., Pergainon Press Inc., New York, N. Y., 1966, pp 380-377.
hkl 101 200
211 220 310 222 32 1 400 330 420 332 422 5 10 530 600 620
OF
CUBICCOBALT PHOSPHIDE Intenuity -d hkl MI
n
w M
S
w M
w w
S W Ms
M
w VY
MI
1.190 1.162 1.136 1.113 1.090 1.069 1.049 1.030 1.013 0.980 0.964 0.950 0.935 0.921 0.909 0.896
541 622 631 444 710 640 721 642 730 732 800 741 820 653 822 831
Intensity
w Mw MI MI
w M W
w M M M
w s w S S
and the assumption of random distribution of six cobalt atoms among the eight 8e skutterudite positions. These preparations were carried out in the “belt” (1) Bureau of Mines, Metallurgy Research Center, College Park, Md. 20740. (2) W. Biltz and M . Ileimbrecht, Z.Axorg. AZlgem. Chenz., 241, 349 (1939).
Vol. 7 , No. 2, February 1968
NOTES 391
SiF4. The CFaSFO was purified by vacuum-line fractionation and identified by its gaseous molecular weight, 19Fnmr spectrum, mass spectrum, and an infrared spectrum, Figure 1, which is consistent with the proposed structure. The C F S F O is a white solid and colorless liquid or gas having a boiling point of approximately -9". It appeared to be thermally stable in stainless steel a t 135" and was unreactive with Acknowledgment.-The authors wish to acknowledge mercury a t 25". Gaseous CF3SFO was stored in dry the able assistance of R. D. Kieft and M. J. Moore in glass for 2 weeks without noticeable decomposition, making the X-ray diffraction patterns and analyses. but after 3 months in normal laboratory light all of the W. T. Doyle made the cobalt analysis. C F S F O was destroyed. Instability of sulfinyl fluo(3) H. T. Hall, Rev. Sci. Instr., 31, 125 (1960). rides in glass was previously noteda2 The C F S F O is (4) NOTEADDEDIN PROOF.-S. Rundqvist and E. Larsson, Acta Chent. slowly hydrolyzed by water vapor a t 25' with destrucScand., 13, 551 (1959), report that Cop3 (a = 7.706 %.) is isostructural with CoAss. tion of the CFa group. No reaction was observed between CsF and CF3SF0 a t 120 or 135" and no complex which was stable a t room temperature was formed when CF3SFO and AsF5were held a t - 78". The addition of Fz to CF3SFO a t 25" produced a number of CONTRIBUTION FROM MIDWEST RESEARCH INSTITUTE, degradation products, but CF3S02Fand CF4 were the KANSAS C I T Y , MISSOURI 64110 major products observed from the reaction a t - 78".
superpressure apparatus3 using a cell constructed of sodium chloride with a graphite heater. The cell was calibrated a t room temperature with the bismuth 25.5and 27-kbar and the barium 58-kbar transformations. Temperatures, uncorrected for pressure, were determined from a calibration of the high-pressure cell with a Pt-Pt-lO% R h thermocouple.4
Trifluoromethylsulfiny1 Fluoride'
,
I
I
I
7/
I
I
I
, 8I
I
,
I
I
WAVELENGTH IN MICRONS 9 IO /I 12 I3 ,
I
T-T-"-'rjjITTmT
I4 15 16
18 20
25
BY EDWARD W. LAWLESS A N D LUEDRIC D. HARMAN Received September 11, 1967
Trifluoromethylsulfinyl fluoride and other alkyl- or arylsulfinyl fluorides were reported2 as minor by-products in the synthesis of the corresponding RSFa compounds, as a result of reaction with the glass apparatus or traces of moisture. Supporting data were given for benzenesulfinyl fluoride which was obtained2 in good yield by the reaction of phenylsulfur trifluoride and benzaldehyde. The CF3SF3 was synthesized2 by the reaction of gaseous CS2 or (CF,S),CS with AgF2. Both reactions were exothermic and gave a mixture of products: SF4, CF3SF3, CF3SF5, and SFe from CS2; and CF3SF3, (CF3)2S2, CF3SF0, and CF3SF5from (CF3S)2CS. We wish to report improved syntheses of C F ~ S F Z and ~ - ~ CF3SFO and some properties of the latter. I n the present investigation, we have found that liquid bis(trifluoromethy1) disulfide will, in fact, readily react further with AgF2. The products are CF3SF3, CF3SF5, and CFSFO. The formation of CF3SF5can be minimized by allowing the reactants to warm from - 10 to 25" over several hours and by avoiding a large excess of AgF2.j The formation of CF3SFO can be minimized by using rigorously anhydrous conditions and passivated, glass-free apparatus. Trifluoromethylsulfinyl fluoride was obtained in good yield b y simply storing small quantities of the product mixture in a glass bulb until all of the reactive CF3SF3 was eliminated by conversion to CF3SFO and (1) This work was supported by the United States Air Force under Contract AF 33(615)-3954. (2) W. A. Sheppard, J. Am. Chew. Soc., 84, 3058 (1962). (3) E. A. Tyczkowski and L. A. Bigelow, ibid., 1 6 , 3523 (1953). (4) R. Dresdner, ibid., 79, 69 (1957). (5) Once formed CFsSFa is resistant t o further fluorination by AgFl a t
350.
WAVENUMBER C M - '
Figure 1.--Infrared
spectrum of trifluoromethylsulfinyl fliioride.
Experimental Section Preparation.-Silver difluoride (Alfa Inorganics, Inc.) and (CF3)& (Peninsular ChemResearch, Inc.) were allowed to per run. react in a series of 11 runs utilizing 1-2 g of (CF3)%S2 The mole ratio of AgFz to (CF,)& was varied from 12: 1 to 2: 1. A valved 75-ml stainless steel cylinder was charged with AgFz in a drybox and the (CFa)& was condensed in a t - 196" in a vacuum line. Each reactant mixture was then held a t a selected temperature in the range - 78-50' for a time in the range 116-0.5 hr. Products were fractionated or transferred in either a glass or an all-metal and Kel-F vacuum line operating a t
