Metal-silicon bonded compounds. 16. The structure of (LiSiMe3)2.(Me2NCH2CH2NMe2)3, a highly reactive silylating agent

Abstract

Supplementary Material Available: Listings of the complete crystallographic details, all positional and anisotropic thermal parameters, all bond lengths and angles, and observed and calculated structure factors for both structures (30 pages). Ordering information is given on any current masthead page.

[Bis(Trimethylsilyl)Methyl]Lithium and -Sodium: Solubility in Alkanes and Complexes with O- and N- Donor Ligands

“…The coordination sphere of the sodium is completed to a distorted tetrahedral environment by the three nitrogen atoms of two different TMEDA groups (Na1-N21 2.559(2) Å; Na1-N31 2.569(2) Å; Na1-N32 2.635(2) Å) with one TMEDA group bridging between the two symmetric monomeric units. A similar arrangement was found for TMEDA-coordinated trimethylsilyllithium [30]. The CH(SiMe3)2 unit shows a clear trigonal pyramidal arrangement of the SiMe3 groups and the hydrogen atom (Si-C-Si 120.91(7)°; the sum of the Si-C-Si and two H-C-Si angles: 336.0°).…”

Synthese und Struktur von Lithium‐tris(trimethylsilyl)silanid · 1,5 DME

“…Mit durchschnittlich 104° weisen die Si-Si-Si-Winkel einen gegenüber dem regulären Tetraeder deutlich verkleinerten Wert auf; die C-Si-C-Winkel im (Lithium-trimethylsilanid)-Hexameren 6 [18] und im TMEDA-Addu~t 7 [19] sowie in den Dilithium~tetrasilanomercura)ten 9 und 10 [25] zeigen ähnliche Abweichungen. Offensichtlich wirkt die stark am Siliciumatom lokalisierte, negative Ladung der polaren Li-Si-Bindung im Sinne des GILLESPIE-NYHOLM-Konzeptes [33] verzerrend; den hieraus resultierenden Wechsel wirkungen innerhalb der Tris(trimethylsilyl)silyl-Gruppe weichen dann die nach innen weisenden Methylgruppen Cn2 (n = 2 bis 4) durch Aufweitung der Winkel Sil-Sin-Cn2 auf durchschnittlich 118° aus.…”

Crystal Structures and29Si NMR Calculations of Amino-Functionalized Silyllithium Compounds

“…This is not unusual but is in contrast to (lithiomethyl)amines. [6] Nevertheless the SiϪLi bond length is relatively short [2.627(4) Å ] compared to other silyllithium species [2.732(7) Å in 1·3THF; [5] 2.70 Å in (Me 3 SiLi) 2 ·3 (Me 2 NCH 2 CH 2 NMe 2 ) 3 ; [7] 2.66 Å in (Me 3 Si) 3 SiLi·3THF; [8] 2.67 Å in Ph 3 SiLi·3THF; [9] 2.65 Å in (Me 3 SiLi) 6 ]. [10a,10b] The two nitrogen centres in 4·3THF show an almost planar environment; the deviations from the plane are 0.057 and 0.088 Å .…”

“…Nevertheless, structural information about these dialkylamino-functionalized silyllithium compounds is scarce. [4a,4b,5] Tamao and co-workers were able to prove that dialkylamino-functionalized silyllithiums are monomeric in solution by observation of 29 SiϪ 7 Li coupling (quadruplet) in the 29 Si NMR spectra in the temperature range of Ϫ100 to Ϫ110°C. [5] However, the nature of the unusual 29 Si NMR chemical (4·3THF), 2.682(8) Å (7·3THF) and 2.732(7) Å {tris(tetrahydrofuran)[bis(diphenylamino)phenylsilyl]lithium} (1·3THF).…”

“…The most important questions are: i) What are the structures of bis(diethylamino)phenylsilyllithium (4) or (diethylamino)bisphenylsilyllithium (7) in the solid state? and ii) How can we explain the unusual downfield shifts of the 29 Si NMR resonance signals?…”