Lithium, sodium, potassium, caesium and magnesium salts of the dianion of 1,2-di-tert-butyl-3- [bis(trimethylsilyl)methylene]-1,2-diborirane have been synthesized and charactarized by 13C and 11B NMR spectroscopy. X-ray structure analysis of the di-potassium salt proves cyclic derealization of two. π-electrons in the CB2-ring by short C-B (150 pm) and B -B (158 pm) bonds. The exocyclic C-C bond (150 pm) is bridged by two potassium ions. One of them contacts the boron atoms of a neighbouring dianion leading to a helicoidal infinite chain with 41-symmetry along the c direction.