2169-38-2Relevant academic research and scientific papers
Trimethyllead-Lithium in Tetrahydrofuran: Synthesis of Trimethyl(trimethylplumbyl)silane and of the Trimethylplumbyltrihydridoborate Anion
Wrackmeyer, Bernd,Horchler, Klaus
, p. 1195 - 1198 (2007/10/02)
Solutions of trimethyllead-lithium Li (1), in tetrahydrofuran (THF) (ca. 0.5 M) can be obtained from trimethyllead bromide and an excess of lithium at -78 deg 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 deg C within minutes.The application of this reagent is demonstrated by the synthesis of trimethyl(trimethylplumbyl)silane (2) and its stoichiometric 1:1 reaction with BH3-THF at -78 deg C, leading to lithium trimethylplumbyltrihydridoborate Li (3).The composition of the products in solution follows conclusively from their 1H, 11B, 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 deg C mainly into lead, Me4Pb, Li and Li. - Keywords: Trimethyllead-Lithium, Trimethyl(trimethylplumbyl)silane, Trimethylplumbyltrihydridoborate Anion, NMR Spectra
Chemistry of boron. 130. The reaction of organolithium compounds with borane donors. Preparation and isolation of lithium monoorganotrihydroborates
Biffar, Werner,N?th, Heinrich,Sedlak, Dieter
, p. 579 - 585 (2008/10/08)
The reactions of a series of organolithium compounds with the borane donors BH3·THF, BH3·SMe2, and BH3·NMe3 have been studied in order to develop a general synthesis of lithium organotrihydroborates, LiRBH3. Starting from RLi and BH3 in THF, all members of the series LiR4-nBHn, are formed irrespective of reaction conditions. Bulky substituents R prevent the formation of LiBR4, with BR3 being produced instead. Much higher proportions of LiRBH3 result from the interaction of RLi and BH3·SMe2, with low temperature favoring their formation. Crystalline LiMe2CHBH3 and LiMe3CBH3 can be obtained by this method in good yield. However, LiBH4 is an inevitable byproduct. Other compounds are also formed in minor quantities. Temperatures of >80°C are required for the reaction of RLi with BH3·NMe3, and LiPhBH3·TMEDA and LiPhCH2BH3·TMEDA were isolated in 35 and 90% yield, respectively. Increasing the bulkiness of R (e.g., CMe3) favors deprotonation of BH3·NMe3 over amine displacement. Either LiMe2NCH2BH3 or [Me2NCH2BH2]2 is formed depending on the reaction conditions.
Contributions to the Chemistry of Boron, 124. Tris(trimethylsilyl)silyl Boranes and Tris(trimethylsilyl)silyl Borates
Biffar, Werner,Noeth, Heinrich
, p. 1509 - 1515 (2007/10/02)
The reactions of several boron halides, methoxides, alkyls and hydrides with tris(trimethylsilyl)silyllithium, which was isolated as the solvate 3SiLi*3C4H8O, 1 (TMSSLi) have been studied. (CH3)2B-Si3 and 9-3Si-9-BBN, were isolated, while 3Si-B(tC4H9)2 could only be detected by 11B NMR.In addition TMSS-B2, (TMSS)2BNMe2 and (TMSS)2BOCH3 were prepared.The methoxyboranes (CH3)3-nB(OCH3)n add to 1 forming silylborates; however, no OCH3/Si3 substitution occurs.The hydrogen bridge in 9-BBN is cleaved symmetrically.The results can be explained by the basicity and the steric requirements of the TMSS group.The TMSS group exhibits a deshielding effect at the boron nucleus relative to the (CH3)3Si group for silylboranes as well as for silylborates. - Keywords: Silylboranes, Silylborates, Steric effects, 11B NMR Spectra
