GB826557A - Production of aminodiboranes - Google Patents

Abstract

Aminodiboranes R2NB2H5 are prepared by reacting an amine-borine of the formula R2NH : BH3, where R is an alkyl radical or hydrogen, and both R's may be the same or different, and a non-protonic acid of the Lewis type in proportions of 2 mols. of the former to 1 of the latter, and then separating and recovering from the reaction products the aminodiborane thus formed. The amine-borines used may be primary amine-borines, e.g. CH3NH2 : BH3, secondary amine-borines, e.g. (CH3)2NH : BH3, and also diborane diammoniate which may be represented as NH3 : BH3. The preferred Lewis acids are boron trifluoride and aluminium trichloride, but other examples mentioned are silicon tetrachloride, phosphorus pentoxide, sulphur dioxide, thionyl chloride and sulphuryl chloride. The reaction conditions are not critical but it is preferred to effect the reaction under elevated temperature and pressure while avoiding temperatures which would cause decomposition of the product. The amine-borine starting materials may be produced by reacting diborane and an amine at low temperatures. Dimethyl amine-borine may be produced by electrolysing a solution of an ionic borohydride, e.g. sodium borohydride, in dimethyl amine, using an inert anode and a mercury cathode, as described in Specification 826,558. In examples: (1) dimethylamine-borine and BF3 in a 2: 1 mol. ratio are held at 100 DEG C. for 12 hours in a sealed tube and the tube is then opened and the dimethyl aminodiborane separated from other products; (2) aluminium chloride is used to replace BF3 in the above example. A comparative example describing the use of hydrogen chloride shows that no aminodiborane is formed.