DFT calculations at the BP86/TZ2P level have been carried out for the compounds OCBBCO, N2BBN2, and [OBBBBO](2-). The calculations predict very short distances,and large bond dissociation energies for the central B-B bonds. The nature of the bonding situation was investigated with an energy decomposition analysis. It shows that the central boron-boron bonds' are genuine triple bonds. The pi-bonding contributes between 38-40% to the total orbital interactions of the B B bonds. The compounds can be considered as donor-acceptor complexes L-BB-L between the central B-2 moiety in the third [(3)(1)Sigma(+)(g)] excited state and the ligands L = CO, N-2, BO-. The pi-backdonation L-BB-L for L = CO, N-2 is very strong, which suggests that the latter bonds should also be considered as triple bonds. The pi-bonding in [OB <- BB -> BO](2-) is weaker, which makes the latter bonds borderline cases for triple bonds. The triple-bond character explains the very large bond dissociation energies for the LB-BL and L-BB-L bonds.