Synthesis and crystal structures of organometallic compounds containing the ligands C(SiMe3)2(SiMe2H) and C(SiMe2Ph)2(SiMe2H)

Metallation of (HMe2Si)(Me3Si)2CH (1) by LiMe gave the organolithium compound Li(THF)2C(SiMe3)2(SiMe2H) (2a), which exists in toluene solution as a mixture of covalent species and ion pairs [Li(THF)4][Li{C(SiMe3)2(SiMe2H)}2] (2b). Treatment of a mixture of 1 and LiMe with KOBut gave KC(SiMe3)2(SiMe2H) (3). This reacted with AlMe2Cl in hexane/THF to give Al(THF)Me2{C(SiMe3)2(Si Me2H)} (4). Treatment of (HMe2Si)(PhMe2Si)2CH (5) with LiMe in Et2O/THF gave the THF adduct [Li(THF)2C(SiMe2Ph)2(SiMe2H)] (6); in the presence of KOBut the solvent-free [K][C(SiMe2Ph)2(SiMe2H)] (7) was obtained. Crystal structure determinations showed that 6 crystallizes in a molecular lattice and 7 in an ionic lattice in which the coordination sphere of the potassium comprises phenyl groups and hydrogen atoms attached to silicon, as well as the central carbon of the bulky carbanion. Compound 7 reacted with an excess of AlMe2Cl to give [AlClMe{C(SiMe2Ph)2(SiMe2H)}]2 (8) and AlMe3. A small amount of the methoxo derivative [Al(OMe)Me{C(SiMe2Ph)2(SiMe2H)}]2 (9) was obtained as a byproduct, presumably after the accidental admission of traces of air. X-ray structural determinations showed that 8 forms halogen-bridged dimers, with the bulky ligands in the anti-configuration, and 9 forms methoxo-bridged species in which the bulky ligands are syn.