Synthesis and crystal structures of organometallic compounds containing the ligands C(SiMe 3) 2(SiMe 2H) and C(SiMe 2Ph) 2(SiMe 2H)

Abstract

Metallation of (HMe 2Si)(Me 3Si) 2CH ( 1) by LiMe gave the organolithium compound Li(THF) 2C(SiMe 3) 2(SiMe 2H) ( 2a), which exists in toluene solution as a mixture of covalent species and ion pairs [Li(THF) 4][Li{C(SiMe 3) 2(SiMe 2H)} 2] ( 2b). Treatment of a mixture of 1 and LiMe with KOBu t gave KC(SiMe 3) 2(SiMe 2H) ( 3). This reacted with AlMe 2Cl in hexane/THF to give Al(THF)Me 2{C(SiMe 3) 2(Si Me 2H)} ( 4). Treatment of (HMe 2Si)(PhMe 2Si) 2CH ( 5) with LiMe in Et 2O/THF gave the THF adduct [Li(THF) 2C(SiMe 2Ph) 2(SiMe 2H)] ( 6); in the presence of KOBu t the solvent-free [K][C(SiMe 2Ph) 2(SiMe 2H)] ( 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 AlMe 2Cl to give [AlClMe{C(SiMe 2Ph) 2(SiMe 2H)}] 2 ( 8) and AlMe 3. A small amount of the methoxo derivative [Al(OMe)Me{C(SiMe 2Ph) 2(SiMe 2H)}] 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.