Arachno-6,9-C2B8H14 dicarbaborane and its 1- and 5-monohalogenated derivatives

Abstract

Reduction of nido-5,6-C2B8H12 with sodium tetrahydroborate in ethanolic sodium hydroxide as a new method for preparing arachno-6,9-C2B8H14 is reported. Electrophilic halogenation of 6,9-C2B8H14 occurs at the B(1) site to give a series of 1-X-6,9-C2B8H13 (X = Cl, Br, and I) derivatives. Stereoselective addition of hydrogen halides to the B(5)-C(6) bond in the [6,9-C2B8H10]2- anion results in the formation of 5-X-6,9-C2B8H13 (X = F, Cl, Br, I and 5'-0-6,9-C2B8H13) compounds. Constitution of all compounds isolated is suggested on the basis of their 1H and 11B NMR data and the effects of halogen substituents on the 11B NMR shielding of individual cage boron atoms are discussed in terms of Δδ and k2 values.