A series of carbene-stabilized symmetrical and unsymmetrical dicationic tetraboranes were prepared and fully characterized. Reactions of these tetraboranes with reductants/bases afford a zwitterionic alkylidene borate–borenium species and a 1,3-azaborinine, respectively. The structural relationship of the alkylidene borate–borenium zwitterion and its zwitterionic diborene analogue was investigated