126. Reactions of iodine pentafluoride with inorganic substances. Iodine oxytrifluoride and iodyl fluoride

Abstract

The reactions of iodine pentafluoride with typical oxides, salts, and metals are described. They lead to a number of new compounds many of which are of a molecular type. A straightforward method of preparing iodine oxytrifluoride is given and the reactions involved are made clear. Thermal decomposition of this compound gives rise to the new iodyl fluoride, I0,F; this can be reconverted into the oxytrifluoride by heating it with iodine pentafluoride. A study of some of these reactions and the physicochemical properties of iodine pentafluoride is still in progress.IODINE PENTAFLUORIDE was originally prepared by Moissan (Compt. rend., 1902,135,563) who made a cursory and qualitative investigation of its reactions with a large number of metals. Emelkus and Sharpe recently (J., 1949,2206) focused attention on the compound by preparing the polyhalide KIF,, and showing the probable existence of an acid-base system in this solvent similar to that furnished by bromine trifluoride (Woolf and Emelhs, J., 1949, 2865). In the same laboratory, Woolf (J., 1950, 3678) showed that iodine pentafluoride reacts with antimony pentafluoride to give SbIF,,, with sulphur trioxide to give a constant-boiling mixture IF5,1-17S03, and with potassium metaphosphate, persulphate, and iodate to give KP0,,2.31F5, K2S20,,1~021F5, and KI03,0*51F,, respectively.Our interest in the compound arose from a claim by Ruff and Braida (2. anorg. Chem., 1934,42,220 ; Angew. Chem., 1934,47,48) to have obtained iodine oxytrifluoride from iodine pentafluoride in three ways : (a) as a by-product in the preparation of iodine pentafluoride from its elements, provided a little oxygen was present during the reaction, (b) by restricted addition of water to iodine pentafluoride, and (c) by reaction between iodine pentafluoride and iodine pentoxide. The second method did not appear likely to give a unique product or a mixture readily separable, but we gave extended trial to the first method, using, as a source of oxygen, the gas itself and also silica powder mixed with the iodine. I n every case, even when considerable quantities were used, we got iodine pentafluoride which on distillation left a minute, white residue insufficient for identification. The fluorination of iodine pentoxide with fluorine diluted to various extents with nitrogen gave no better results ; but iodine pentoxide dissolved in boiling iodine pentafluoride to a colourless solution which, on cooling to room temperature, deposited white crystals of iodine oxytrifluoride : 1205 + 31F5 + 510F3. This reaction Ruff and Braida believed to be reversible on heating, but this is not the case. It goes smoothly until all the oxide is consumed, the oxy-compound dissolving in the excess of pentafluoride. Actually, on heating the oxytrifluoride at 110" we observed a new reaction leading to the hitherto unrecorded iodyl fluoride, I0,F : 210F3 I/ 10,F + IF,. This is an interesting change because it is reversible. When iodyl fluoride is refluxed with iodine pentafluoride it goes completely into solution, and...

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