Alkylation of the [nido-5,6-(R2C2B8H9)-C-1](-) anions (where R-1 = H and Me) with alkyl halides (RX, where R = primary and secondary alkyls) in. boiling tetrahydrofuran (THF) proceeds via unusual H-2 elimination, followed by cage closure to give a series of the neutral closo-1,2-(R2C2B8H7)-C-1-3-R derivatives in similar to 70-80% yields. In contrast, treatment of the unsubstituted [nido-5,6-C2B8H11]- anion with tert-butyl bromide (t-BuBr) led to the formation of the parent closo-1,2-C2B8H10 in >85% yield. The constitution of all compounds isolated has been confirmed unambiguously by multinuclear (B-11, H-1, and C-13) nuclear magnetic resonance measurements and alpha-shift correlation assessments.