Dicarbollides are obtained by base-degradation of 12-vertex dicarboranes.  This degradation of the ortho derivative has been most heavily studied.  The conversion is conducted in two-steps, first "deboronation" and second deprotonation:
:CBH  +  NaOEt  +  2 EtOH  →  NaCBH  +  H  +  B(OEt)
:NaCBH  +  NaH  →  NaCBH  +  H
The dianion derived from dicarboranes, [CBH], are nido clusters.  Three isomers exist.  Most commonly studies is the 7,8-isomer, with two adjacent carbon centers on the rim.  7,9- has non-adjacent carbon centers on the rim.  It is derived by degradation of meta-.  2,9- has only one carbon center on the rim.  It is derived by degradation of para-.