Towards Understanding the Reactivity and Optical Properties of Organosilicon Sulfide Clusters

We report the extension of the class of organotetrel sulfide clusters with further examples of the still rare silicon-based species, synthesized from RSiCl₃ with R=phenyl (Ph, I), naphthyl (Np, II), and styryl (Sty, III) with Na₂ S. Besides known [(PhSi)₄ S₆ ] (IV), new compounds [(NpSi)₄ S₆ ] (1) and [(StySi)₄ S₆ ] (2) were obtained, the first two of which underwent reactions with [AuCl(PPh₃ )] to form ternary complexes. DFT studies of cluster dimers helped us understand the differences between the habit of {Si₄ S₆ }- and {Sn₄ S₆ }-based compounds. Crystalline 1 showed a pronounced nonlinear optical response, while for intrinsically amorphous 2, the chemical damage threshold seems to inhibit a corresponding observation. Calculations within the independent particle approximation served to rationalize and compare electronic and optical excitations of [(RSi)₄ S₆ ] clusters (R=Ph, Np). The calculations reproduced the measured data and allowed for the interpretation of the main spectroscopic features.