Silyl- und phosphinosubstituierte Methane: Präparative und strukturelle Untersuchungen zur Steuerung des Reaktionsverhaltens ambidenter Phosphinomethanide / Silyl and Phosphino Substituted M ethanes: Synthetic and Structural Investigations of the Reactivity of Ambidentate Phosphinom ethanides

Abstract

LiCH(PMe2)2 reacts with SiCl4 or with PhR2SiCl (R = Me, Ph) via the carbanion to give silyl substituted phosphino methanes; Cl2Si[CH(PMe2)2]2 (3) or PhR2Si[CH(PMe2)2] (4) (R = Me) and (5) (R = Ph), respectively. 4 and 5 are deprotonated by nBuLi to give trimeric {Li[C(PMe2)2(SiMe2Ph)]}3 (6) and in the precence of TMEDA. monomeric {Li[C(PMe2)2(SiMe2Ph)]·TMEDA (7) or {Li[C(PMe2)2(SiPh3)]} · TMEDA (8), respectively. {Li[C(PMe2)(SiMe3)2]}2·TMEDA reacts with R2SiCl2 (R = Me. Cl) via both the carbanion, thus generating a tetraheteroatom substituted methane moiety and, in a second substitution step, via phosphorus, thus generating an ylidic moiety. The obtained compounds (Me3Si)2(PMe2)C-SiR2-PMe2=C(SiMe3)2 (9) (R = Me) and (10) (R = Cl) are structurally characterized by X-ray crystallography as well as compounds 3, 5, 6 and 7. The observed variations in bond lengths and angles are explained to be mainly due to steric congestion. The ambidentate nature of phosphinomethanides thus clearly can be influenced by the nature of their carbanion substituents.