Structure and thermal decomposition of methylamine borane

The crystal structure of methylamine borane has been determined and contains parallel chains of dihydrogen-bonded CH(3)NH(2)BH(3) molecules. Thermal decomposition takes place from the melt (Delta H(fusion) = 8.5 kJ mol(-1)) and begins with the formation of an ionic borohydride. Hydrogen is liberated in two stages, at ca. 100 and 190 degrees C, with the observed rates during the first stage (Delta H = -25 kJ mol (-1), E(a) = 115 kJ mol(-1)) strongly dependent on temperature and time. cis- and trans-N-trimethylcyclotriborazane are formed during the first stage and subsequently cross-link to yield a non-volatile solid. Before this cross-linking, the system exhibited a high degree of volatility, with weight losses in excess of 80% observed in TG experiments using flowing gas. (C) 2007 Elsevier B.V. All rights reserved.