The present is the first of a series of papers describing new developments in the methods of preparation and in the chemistry of diborane and of the borohydrides. New and practical methods for the preparation of borohydrides (a) from diborane, and (b) without the use of diborane are discussed. As a result of the availability of borohydrides, prepared without the use of diborane, methods, far more satisfactoiy than those hitherto known for the preparation of the latter, have been developed. The investigation has led to the preparation of the hitherto unknown borohydrides of sodium, of potassium and of uranium, and some of their derivatives, as well as of a new type of substance, such as sodium trimethoxyborohydride, NaBH(OCH3)3, formed by the addition of compounds of trivalent boron to alkali metal hydrides. Sodium borohydride, as well as sodium trimethoxyborohydride, are of special interest because of their potential usefulness as reducing agents and sources for the generation of hydrogen; uranium(IV) borohydride and its derivatives are of interest because they are the most volatile compounds of uranium except the hexafluoride. The present paper surveys numerous new observations made and organizes the subject matter in the light of the principle which largely guided the research, namely, the application of the Lewis generalized acid-base concept to the reactions of diborane, of the salt-like hydrides and of the borohydrides. Detailed description of the new preparative methods and data confirming the reaction equations herein presented as well as supporting the composition of new substances are deferred to the remaining papers of the series.vestigations carried out under contracts with the National Defense Research Committee, with the Office of Scientific Research and Development and with the Signal Corps, Ground Signal Agency during the years 1940-1944. They were continued under Navy auspices during [1944][1945][1946]. Most of the results were originally described in the final reports on contracts NDC-rc-56, 9820 and 10,421.
Xenon and fluorine combine readily. Xenon tetrafluoride is a colorless crystalline material, stable at room remperature. The existence of at least one other fluoride and two oxyfluorides has been demonstrated. The heaviest "inert gas," radon, also reacts with fluorine, yielding a compound less volatile than xenon tetrafluoride.
The addition compounds of BrFs with KF or SbFs are found to be excellent high temperature fluorinating agents. Dissociation pressures of KBrFi and BrF2SbF« to 350°have been measured and are of such a magnitude that these reagents can be used even at 500°in closed reaction vessels without developing high pressures. Many inorganic compounds, including refractory oxides, feldspars and oxygen-containing salts which resist fluorination by BrFg itself are readily converted to fluorides and elemental oxygen by KBrFi and BrF2SbFg at elevated temperatures. Apparatus and techniques for carrying out these unusual high temperature fluorination reactions are described and the relative merits of these two reagents compared. on the basis of their acid-base relationship.
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