| The acid-catalysed ammonolysis of hydroborate ion has been studied in warm liquid ammonia solution, in the ammonium ion concentration range 0.001-0.8 M. The reaction of BH(,4)('-) with NH(,4)('+) to yield NH(,3)BH(,3) was found to be first order in both ions. The second order rate constant in a solution of ionic strength 0.2 at 30(DEGREES) is 1.94 x 10('-4)M('-1)sec('-1). Varying the ionic strength at 30(DEGREES) gave rate constants that followed the Bronsted-Bjerrum relationship below an ionic strength of 0.9. The rate was studied in the range 25-45(DEGREES), and the activation energy was determined to be 38.5 kcal/mol.; The preparation of NH(,3)BH(,3) by the above reaction in warm, dilute liquid ammonia solution (in a pressure vessel) was found to yield a very pure product. Pure NH(,3)BH(,3) was also prepared by a new synthesis in which ammonium sulfamate reacts with sodium hydroborate in a concentrated ammonia solution at room pressure.; A new compound, diaminoborane, HB(NH(,2))(,2), was discovered in the products from the pyrolysis of HN(,3)BH(,3) in an atmosphere of ammonia. This molecule was characterized by chemical analysis, mass spectra, boron-11 nmr, infrared spectra, and microwave spectra. In liquid ammonia solutions of ammonium iodide (0.1-1.0 M NH(,4)('+)) diaminoborane reacts to produce two new species in labile equilibrium. Boron-11 nmr data allow identification of one of these species as the triamminehydroboron ion, HB(NH(,3))3('2+), and suggest that the other is diaminoborane ammine, HB(NH(,2))(,2)NH(,3). |
