An Acyclic Imino‐Substituted Silylene: Synthesis, Isolation, and its Facile Conversion into a Zwitterionic Silaimine

Abstract

Auf zwei unterschiedlichen Wegen wurde ein neuartiges Silylen hergestellt, das von einem Cp*‐ und einem Imidazolin‐2‐iminato‐Liganden stabilisiert wird. In der Röntgenkristallstruktur wird das Silicium(II)‐Zentrum von einem η2‐Cp*‐Liganden und dem Stickstoffatom eines Imidazolin‐2‐iminato‐Liganden koordiniert. Das Silylen reagiert leicht mit B(C6F5)3 zu einem stabilen Boranaddukt, das eine zwitterionische Resonanzstruktur aufweist.

Facile Access to Stable Silylium Ions Stabilized by N-Heterocyclic Imines

“…Single crystal X-ray diffraction analysis of 8 reveals that it crystallizes as a contact ion pair with the triflate anion in the solid state to form a tetrahedral silicon center with an Si-O bond distance of 1.7696(17) Å ( Figure 5). The bond angle of Si-N-C is 158.77 (17) • , which falls in the range of the mono-imino-substituted tetravalent silanes [27,29]. Furthermore, the Si-N imino bond distance (1.6231(18) Å) is comparable to those reported for tetravalent silane bearing an imino ligand and indicative of a negligible Si=N double bond character.…”

“…Moreover, the bond angle of C NHC -N-Si (139.63 • ) shows a remarkably bent structure. This value is much larger than that in the iminosilylene-borane adduct having a significant silaimine character [29], indicating the π-electron interaction between the imino-nitrogen towards the silylium center can be neglected. The signals at −32.0 and 13.1 ppm are well reproduced by gauge-independent atomic orbitals (GIAO) calculation of the optimized structure of 4 and confirmed the assignment (−33.1 and 12.6 ppm).…”

“…A signal was observed in the 29 Si-NMR spectrum at δ = 17.3 ppm, which is significant low-field shifted compared to that of the precursor 1 (−22.3) [37]. This value is very similar to that of phosphinoimino complex of the silylium ion (δ( 29 Si) = 7.9 ppm) [36], illustrating the existence of dimer 2[MeB(C 6 Herein we describe the facile synthesis of novel imino-substituted silylium ions by the abstraction of methyl group of the trimethylsilyl ligand.…”

“…A signal was observed in the 29 Si-NMR spectrum at δ = 17.3 ppm, which is significant low-field shifted compared to that of the precursor 1 (−22.3) [37]. This value is very similar to that of phosphinoimino complex of the silylium ion (δ( 29 Si) = 7.9 ppm) [36] In order to gain deeper insight into the electronic nature of the structure of 2, we performed a Natural Resonance Theory (NRT) analysis.…”

“…During the last years, N-heterocyclic imines (NHIs) have been exploited for the syntheses of various unique main group compounds [28]. In Group 14, several metallylenes were synthesized by using NHIs as ligand [29][30][31][32], and two-coordinated metallyliumylidenes III (Figure 1) were also successfully isolated owing to stabilization of the NHI ligand by its high σ-donation together with delocalization of a positive charge around the imino fragment [31,32]. Shortly after, it was also demonstrated the NHIs effectively stabilize a spacer-separated bis(germyliumylidene) IV (Figure 1) [33].…”