Synthesis and X-ray Crystal Structures of New Tetrahedral Arylethynyl Substituted Silanes

The tetrakis(arylethynyl)silanes 1–4 of which 2–4 are new compounds have been synthesized and determined by single crystal structure analysis to show their tetrahedral molecular geometries reflected in slightly disturbed S₄ symmetry in the crystal lattices. The lattice structures are mainly determined by close packing effects while the interactions of π-stacking type or C–H···π contacts are rather secondary. A similar behaviour is found for the crystal structure of the comparative compound 5 with reference to 4 which lacks the ethynylene units. It is demonstrated that the given molecular constructions are distinguished by a high degree of tetrahedral persistency governing the packing structures.