Group 13-group 16 heterocubanes [RM(μ3-E)]4 (R = H, CH3; M = Al, Ga, In; E = O, S, Se, Te) and group 13 cubanes [RM(μ3-M)]4 (R = F, Cl, CH3, NO2; M = Al, Ga, In): A structural study
Twenty-four group 13-group 16 chalcogen heterocubanes [RM(μ3-E)]4 (R = H, CH3; M = Al, Ga, In; E = O, S, Se, Te) and 12 group 13-group 13 pure cubanes [RM(μ3-M)]4 (R = F, Cl, CH3, NO2; M = Al, Ga, In) have been studied using density functional theory. Geometries and thermodynamic properties were computed at the B3LYP/SRLC level. All structures were found to be true minima with at most 0.08 Å and 2.5° deviation from the limited experimental geometries. These chalcogen heterocubanes appear thermodynamically resistant to fragmentation. The M4E4 core for each structure proved to be insensitive to ligand choice for the group 13-group 16 heterocubanes. By contrast, the electron-deficient M8 cores of the pure cubanes were variously affected by the electronegativity of various R groups. The entropically disfavored nature of the synthesis may hold the key to the as-yet-unsynthesized [RAl(μ3-O)]4.
Barden, CJ; Charbonneau, P; Schaefer, HF
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