GB864616A - A process for the production of alkali metal and alkaline earth metal borohydrides - Google Patents

Abstract

Alkali or alkaline earth metal borohydrides are prepared by reacting alkali or alkaline earth metals or hydrides with a substituted diborane containing up to 4 hydrocarbon radicals or a substituted borine of general formula BRR21 where R is a carbocyclic radical and R1 are saturated aliphatic or carbocyclic radicals, or H. Where the substituted borine contains no H, then H2 must be present for reaction, and in any case reaction may be effected in the presence of H2 under pressure. The mixture may be heated, with, or without, distilling, or filtering off the tri-substituted borine formed with the borohydride, and with a substituted borine the temperature may be 140-220 DEG C., but with a substituted diborane below 140 DEG C. The reaction may be effected in inert organic liquids, e.g. aliphatic or aromatic hydrocarbons, ethers, or tertiary amines, such as hexane, benzene tetrahydrofuran, or diglycoldimethyl or triglycoltrimethyl-ethers. If reactants and products are insoluble in the liquid, reaction may be effected with simultaneous comminution, e.g. in a ball mill. Where ethers are used the borohydride is formed as an etherate, and with tertiary amines the reaction may be under pressure at above 160 DEG C. The trisubstituted borine may be reconverted into the reactant borine by hydrogenation as described in Specification 854,919. Colloidal boron may be formed in the reaction and is washed out with solvent. In examples:- (1) and (3) Na or NaH is reacted with (C2H5)4 B2H2; (2) and (7) K or Ba H2 is reacted with (C2H5)3 B2H3; (5) and (8) Na or CaH2 is reacted with B(C6H5)3 and H2; (6) CaH2 is reacted with (C3H7)4 B2H2.