Abstract The molecular structures of lithiopentamethyldisilane ([LiSiMe2SiMe3]4, 1a), 2-lithio-1,1,2,3,3-pentamethyl-1,3-diphenyltrisilane ([LiSi(SiMe2Ph)2Me]2, 1b), and 2-lithio-1,1,1,3,3,3-hexamethyl-2-phenyltrisilane ([LiSi(SiMe3)2Ph]2, 1c) have been determined by X-ray diffraction. The silyllithium 1a is a tetramer in the solid state with intramolecular Li···CH3 agostic interactions. The silyllithiums 1b and 1c are dimers with intramolecular lithium-phenyl interactions. The latter adopts a molecular structure with not only an intramolecular Li–Ph interaction, but also an intermolecular Li···CH3 agostic interaction. The structures of these organometallic derivatives show novel features not observed in solvent-coordinated lithiosilanes. These features provide valuable insights into structures that differ markedly from those of lithiosilanes containing coordinated donor solvent molecules.