It crystallizes as a tetrameric cubane-type cluster. It crystallises from tetrahydrofuran/pentane at −20°C as [tBuOK·tBuOH], which consists of straight chains linked by hydrogen bonding. Sublimation of [tBuOK·tBuOH] affords the tetramer [tBuOK], which adopts a cubane-like structure. Mild Lewis basic solvents such as THF and diethyl ether do not break up the tetrameric structure, which persists in the solid, in solution and even in the gas phase.