Neue Synthesewege zu B4H10 und B5H9 / New Synthetic Routes to B4H10 and B5H9

Abstract

The boron hydride B4H10 is prepared in high yields (90%) through hydride-ion abstraction reactions when a mixture of BH4 -/B4H8 - is treated with CH3I or I2 respectively. A high yield (96%) method for the conversion of B3H8 to B4H10 is the reaction of B3H8 - with AICl3 solvents which do not have any Lewis base character. The solvents are assumed to react as electron acceptors with the intermediate [B2H5 -] to form B4H10, R- and H2 (R-H = solvent). A 1:1 mixture of B4H10, and B5H9 is obtained when B3H8 - is treated with CH3I or I2. The reaction can be viewed to involve an initial step in which unstable “B3H7” is generated which immediately undergoes decomposition to give B4H10, B5H9 and H2. Treatment of B4H10 with (n-Bu)4NBr results in the formation of B4H7Br- which decomposes slowly at 0 °C to form B5H9. An alternative synthesis of B5H9, via hydride-ion abstraction is possible through the reaction of (n-Bu)2O-BF4 with B3H8 - in ether solvents.