Towards Understanding the Reactivity and Optical Properties of Organosilicon Sulfide Clusters.

We report about the successful extension of the class of organogtetrel sulfide clusters by further examples of the still rare silicon-based species, synthesized from RSiCl 3 with R = phenyl (Ph, I ), naphthyl (Np, II ), and styryl (Sty, III ) with Na 2 S. Besides known [(PhSi) 4 S 6 ] ( IV ), new compounds [(NpSi) 4 S 6 ] ( 1 ) and [(StySi) 4 S 6 ] ( 2 ) were obtained, the first two of which underwent follow-up reactions with [AuCl(PPh 3 )] to form ternary complexes. Density functional theory (DFT) studies of cluster dimers helped to understand fundamental differences between the habitus of {Si 4 S 6 }-based vs. {Sn 4 S 6 }-based compounds. Investigations of the optical properties of crystalline compound 1 and intrinsically amorphous 2 indicated the former to show a pronounced nonlinear optical response, i.e. , second-harmonic generation, while for the latter, the chemical damage threshold seems to inhibit a corresponding observation that can be clearly put down to nonlinear optical effects. Calculations within the independent particle approximation (IPA) served to rationalize and compare electronic and optical excitations of [(RSi) 4 S 6 ] clusters (R = Ph, Np). The calculations reproduced the measured data and allowed for the interpretation of the main spectroscopic features.