Novel Route to Boron-10 Enriched Pentaborane(9) from Boric Acid and Its Conversion to wV/o-10BıoHı4 and anîi- BısÜ22- Synthetic Advance in Polyhedral Borane Chemistry and in BNCT Research

Boron-10 enriched boric acid, H3B03, was converted to the corresponding sodium borohydride, NaBH4, in essentially quantitative yields, by using slightly modified literature methods involving the formation of butyl borate, (n-OBu)jB, first and then reacting it with NaH in mineral oil. The oxidation reaction of NaBH« with I2 in diglyme and subsequent addition/purification in dioxane gave Na[B3Hg].3(G|H8O2) that reacted further with NİG2 in benzene at 110°C to produce the corresponding BsH9 as the first isolated B-enriched liquid boron hydride in a laboratory environment. Treatment of this BsH9 with NaH or t-BuLi in 2:1 molar ratio underwent a cage expansion reaction to produce the [M] '"BÇH« that undergoes a redox reaction in situ with anhydrous NİCI2 or FeCl3 in n-hexane, or with bromopentane to yield the corresponding fused cage anri-10BigH22 or nidoBn}Hu as the only solid borane product in good yields thus establishing new synthetic routes for the preparation of B-enriched polyhedral boranes.