effect of cation and solvent on the reactivity of saline borohydrides for reduction of carboxylic esters - improved procedures for the conversion of esters to alcohols by metal borohydrides.
Light metal borohydrides and especially lithium borohydride (LiBH4) has attracted a great deal of attention in recent years because of its large gravimetric and volumetric hydrogen density.
Such enhanced diffusivity was found to be effective in the formation of solid solution and co-confinement with other metal borohydrides.
To elucidate this issue, we investigate the properties of a number of metal borohydrides with the same problem and find that the electronegativity of the metal cation is not the best descriptor of diborane production.
The experimental results indicate that the combination of appropriate cations is an effective method to adjust the thermodynamical stabilities of metal borohydrides, similar to the conventional "alloying" method for hydrogen storage alloys.
We conclude that diborane production is sufficiently suppressed for formation enthalpies of −80 kJ/mol BH4 or lower, providing specific design guidelines to tune existing metal borohydrides or synthesize new ones.
The boron orbitals are hybridized to either the sp2 (when boron forms bonds with three other atoms, for example, in borazine) or the sp3 (when boron forms bonds with four atoms, as in metal borohydrides) configuration (see chemical bonding: Valence bond theory: Hybridization).
Mass spectrometry, thermogravimetry and temperature-programmed desorption studies of metal cation-modified aluminum-based borohydride ammoniates using the reactions of various metal borohydrides M BH4 n (M = Na, Li, Ca, Mg) and chlorides MCln (M = Sc, Ni, Cu, Zn, Mg, Ca, Li) reveal that their dehydrogenation properties are strongly dependent on the polarizing power of the added metal cations.
The present study aims at investigating, for the first time, a quinary mixture of light-metals borohydrides.
