Chalcogenide exchange reaction of [RGa(μ₃-Te)]₄ with elemental sulfur and selenium: A density functional theory study

Thermodynamic and mechanistic features of the chalcogen exchange reaction between [RGa(μ₃-Te)]₄ and elemental sulfur or selenium have been studied employing density functional theory (DFT) calculations using the BL3YP basis set and Stuttgart pseudopotentials. For [MeGa(μ ₃-E)]₄ (E = S, Se, Te) the correlation between the calculated parameters and diffraction data for their isolable analogs is greater than 98%. Each step of the conversion of [MeGa(μ ₃-Te)]₄ to [MeGa(μ₃-E)]₄ via [Me₄Ga₄(μ₃-Te)_4-x(μ ₃-E)_x] (E = S, Se) is predicted to occur as a series of isolated reactions. The entropy change for each chalcogen exchange is small in magnitude and corresponds to the degree of cage distortion within the cubane molecules. Calculations performed on [MeGa(μ₃-Te)] ₄⋯S₈ and [MeGa(μ₃-Te)]₄-S suggest that an increase in electrophilicity of the gallium next to a surface bound tellurium may result in nucleophilic cage opening for which intermediate structures are calculated.