Mechanochemical reactions in the chemistry of boranes

Major concepts, experimental methods and applied aspects of mechanochemistry are reviewed in this paper. Mechanochemical reactions involved in the consideration include syntheses of diborane(6), borane adducts (L . BH3) with organic nitrogen-containing Lewis bases, borazine, tetrahydroborates of transition metals M(BH4)(n) where M = Ti(III), Zr(IV), Hf(IV), U(IV), formation of metal-carborane close-cluster SnC2B9H11 and some other cluster systems. The listed solid-phase reactions were performed under mechanical activation of the mixture of starting compounds in hermetic rotational and vibratory ball mills. The usage of solvents as a medium is excluded from mechanochemical syntheses of this kind. Volatile boron-containing compounds are isolated from the reaction medium by evaporation. Composition of initial mixtures, as well as conditions of mechanical activation, temperature regimes, and activation time affecting results of mechanochemical reactions under consideration are described and discussed in comparison with conventional synthesis methods. (C) 1999 Elsevier Science S.A. All rights reserved.