Structural Characterization of Lithium and Sodium Bulky Bis(silyl)amide Complexes.

ABSTRACT: Alkali metal amides are vital reagents in synthetic chemistry and the bis(silyl)amide {N(SiMe?)?} (N′′) is one of the most widely-utilized examples. Given that N′′ has provided landmark complexes, we have investigated synthetic routes to lithium and sodium bis(silyl)amides with increased steric bulk to analyse the effects of R-group substitution on structural features. To perform this study, the bulky bis(silyl)amines {HN(SitBuMe?)(SiMe?)}, {HN(SiiPr?)(SiMe?)}, {HN(SitBuMe?)?}, {HN(SiiPr?)(SitBuMe?)} and {HN(SiiPr?)?} (1) were prepared by literature procedures as colourless oils; on one occasion crystals of 1 were obtained. These were treated separately with nBuLi to afford the respective lithium bis(silyl)amides [Li{μ-N(SitBuMe?)(SiMe?)}]? (2), [Li{μ-N(SiiPr?)(SiMe?)}]? (3), [Li{N(SitBuMe?)?}{μ-N(SitBuMe?)?}Li(THF)] (4), [Li{N(SiiPr?)(SitBuMe?)}(DME)] (6) and [Li{N(SiiPr?)?}(THF)] (7) following workup and recrystallization. On one occasion during the synthesis of 4 several crystals of the ‘ate’ complex [Li?{μ-N(SitBuMe?)?}(μ-nBu)]? (5) formed and a trace amount of [Li{N(SiiPr?)?}(THF)?] (8) was identified during the recrystallization of 7. The reaction of {HN(SitBuMe?)?} with NaH in the presence of 2 mol % of NaOtBu gave crystals of [Na{μ-N(SitBuMe?)?}(THF)]? (9-THF), whilst [Na{N(SiiPr?)?}(C?H?)] (10) was prepared by deprotonation of 1 with nBuNa. The solid-state structures of 1?10 were determined by single crystal X-ray crystallography, whilst 2?4, 7, 9 and 10 were additionally characterized by NMR and FTIR spectroscopy and elemental microanalysis.

SUBMITTER: Nicholas HM 

PROVIDER: S-EPMC6100173 | biostudies-other | 2018 May

REPOSITORIES: biostudies-other