The addition compound Cl 3 SiSiCl 3 ·TMEDA was formed quantitatively by treatment of Cl 3 SiSiCl 3 with tetramethylethylenediamine (TMEDA) in pentane at room temperature. The crystal structure of Cl 3 SiSiCl 3 ·TMEDA displays one tetrahedrally and one octahedrally bonded Si atom (monoclinic, P2 1 /n). 29 Si CP/MAS NMR spectroscopy confirms this structure. Density functional theory (DFT) calculations have shown that the structure of the meridional ...