Synthesis and Structure of Lithium Tris (trimethylsilyl) silanide . 1,5 DME Abstract. Lithium tris(trimethylsilyl}silanide' 1,5 DME 2a synthesized from tetrakis(trimethylsilyl)silane 1 [6] and methyllithium in 1,2-dimethoxyethane 1 ), crystaIlizes in the monocIinic space group P2 1 /c with following dimensions of the unit cell determined at a temperature of measurement of -120 ± 2°C: a = 1072.9(3); b = 1408.3(4}; c = 1775.1(5} pm; ß = 107.74(2)°; 4 formula units (Z = 2). An X-ray structure determination (R w = 0.040) shows the compound to be built up from two [lithium tris(trimethylsilyl)silanide] moieties which are connected via a bridging DME moleeule. Two remaining sites of each four-coordinate lithium atom are occupied by a chelating DME ligand. The Li-Si distance of 263 pm is considerably longer than the sum oi covalent radii; further charactcristic mean bond lengths and angles are: Si-Si 234, Li-O 200, O-C 144, 0···0 (bite) 2G4pm; Si-Si--Si 104°, Li--Si-Si 107° to 126°; O-Li-O (inside the chelate ring) 83°. Unfortunately, di(tert-butyl)bis(trimethylsilyl)silane 17 prepared from di(tert-bntyl)dichlorsilane 15, chlorotrimethylsilane and lithium, does not react with alkyllithinm compounds to give the analogons silanide.