Intramolekulare Ringerweiterung eines 2‐Lithium‐anilido‐2‐fluoro‐1,3‐diaza‐2‐silacyclopentens zum 1,3,5‐Triaza‐7‐bora‐2‐silacyclohepten – Experimentelle und Quantenchemische Ergebnisse

Abstract

The reaction between the lithiated 2‐diisopropylanilino‐2‐fluoro‐1,3‐diaza‐2‐silacyclopentene, (HCNCMe3)2SiFNLi(2,6‐Me2CH)2C6H3 (I), and BF3·OEt2 in THF afforded in an unknown, intramolecular ring expansion the seven‐membered 1,3,4‐triaza‐7‐bora‐2‐silacycloheptene, (HCNCMe3)2(SiF2)BFN‐2,6‐(Me2CH)2C6H3 (1). Starting with the BF2‐substituted compound A, quantum‐chemical calculations on the thermal isomeration process revealed a two‐step reaction mechanism: First, the bicyclic compound C is formed via transition state TS1, and second, a 1,3‐fluoride ion migration occurs in the seven‐membered transition state TS2 from a BF2‐ to a SiF‐unit. The reaction mechanism and the structures of the transition states are discussed in detail.

From the Lithium‐2‐anilide‐2‐fluoro‐1,3‐diaza‐2‐sila‐cyclopentene‐GaCl3 Adduct to 1,4,6‐Triaza‐5‐gallium‐7‐sila‐cyclo‐3‐heptene ‐ Experimental and Quantum‐chemical Results

“…The five-membered (HC-NCMe 3 ) 2 Si-ring system is planar and N(3) has a planar environment. However, the sum of the angles around N (1) Encouraged by the reported seven-membered ring II [14] and the bicyclic compounds III [15] (Scheme 1), which were obtained in the reaction of the lithium salt I with trifluoroborane (II) or trimethylalane (III), we investigated the thermal reaction behavior of 1 and found that from 80 °C up to 150 °C LiCl elimination and ring expansion occur. LiCl elimination from lithiated aminochlorosilanes led in the past to the formation of iminosilenes; compounds with a Si=N double bond [5,12,16,17] .…”