The syntheses and structures of two clusters containing 12 Mo-Mo quadruple bonds, [Mo-24(C12H12O4)(24)](C5H5N)(12) and Mo-24(C8H4O4)(24), are reported. The 12 paddlewheel building blocks and 24 ligands self-assemble into cuboctahedral and anticuboctahedral polyhedra, respectively, depending on the manner in which the two halves of the cluster are aligned. These clusters contain twice as many dimolybdenum units as any previously reported cluster. Possible assembly mechanisms are also proposed.