Trimethylblei-Lithium in Tetrahydrofuran: Synthese von Trimethyl(trimethylplumbyl)silan und des Trimethylplumbyltrihydridoborat-Anions / Trimethyllead-Lithium in Tetrahydrofuran: Synthesis of Trimethyl(trimethylplumbyl)silane and of the Trimethylplumbyltrihydridoborate Anion

Abstract

Solutions of trimethyllead-lithium, [Me3Pb]Li (1), in tetrahydrofuran (THF) (-0.5 M) can be obtained from trimethyllead bromide and an excess of lithium at –78°C. 1H. 13C and 207Pb NMR are used for monitoring the formation of the reagent. Extensive decomposition into lead and tetramethyllead is observed at –20°C within minutes. The application of this reagent is demonstrated by the synthesis of trimethyl(trimethylplumbyl)silane (2) and by its stoichiometric 1:1 reaction with BH3–THF at –78°C, leading to lithium trimethylplumbyltrihydridoborate [Me3PB–BH3]Li (3). The composition of the products in solution follows conclusively from their 1H, 11B13C, 29B, 13C, 29Si, and 207Pb NMR data. The silane 2 decomposes slowly at ambient temperature into Me4Si, Me4Pb and lead. The borate is even less stable, decomposing at temperatures above –30°C mainly into lead, Me4Pb, [H4B]Li and [Me4B]Li.