These are the raw data the compound ThCs2, refined as a merohedral twin. The following is the abstract of the corresponding paper. Heterobimetallic tert-butoxides of alkali metal cations and tetravalent actinide centers exhibit two distinctive structural motifs, [AnM2(OtBu)6] and [AnM3(OtBu)7] (AnIV = Th, U and MI = Li, Na, K, Rb, Cs), evidently govern by the size of the alkali metal ions. Both [AnM3(OtBu)7] AnM3 (AnIV = U, MI = Li; AnIV = Th, MI = Li, Na) and [AnM2(OtBu)6] AnM2 (AnIV = U, MI = Na – Cs; AnIV = Th, MI = K - Cs) compounds are obtained in nearly quantitative yields by reacting the actinide and alkali metal silyl amides with excess of tert-butyl alcohol. The AnM3 complexes form a cubane-type coordination motif, whereas the AnM2 complexes display a geometry resembling two face-shared bipyramids. The sodium derivatives of thorium and uranium (ThNa3 and UNa2) allow to determine the structural transition threshold as function of the ratio of the ionic radii, ri(AnIV)/ri(MI). The AnM3 complexes are formed for ratios above 0.92 and the AnM2 type is formed for ratios below 0.87. All compounds are unambiguously characterized in both solution and the solid-state via NMR and IR spectroscopic studies and single crystal X-ray diffraction analyses, respectively.