A New Type of N-Heterocyclic Silylene with Ambivalent Reactivity

Abstract

The synthesis of a novel divalent silicon compound by debromination of the corresponding dibromosilyl precursor is reported. The silylene possesses a unique reactivity toward electrophiles of the type R-X (R = H, silyl; X = halogen, triflate) in comparison with the germanium congener. DFT calculations suggest that this is due to a much higher basicity of the silylene versus that of germylene lone-pair electrons. Thus, addition of Me3SiX to the silylene (X = OSO2CF3, triflate) furnishes the corresponding (kinetically favored) 1,4-adduct which subsequently rearranges to the thermodynamically favored 1,1-adduct.

From a Stable Silylene to a Mixed‐Valent Disiloxane and an Isolable Silaformamide–Borane Complex with Considerable Silicon–Oxygen Double‐Bond Character

“…Recently, we prepared the stable zwitterion-like silylene [LSiD] 1, [14] which could be a suitable starting material for the generation of the desired hydroxo silylene (HL)Si(OH) (2) by 1,4-addition of H 2 O ( Figure 2); alternatively, 1,1-addition of water at the divalent Si atom could lead to the tautomer LSiH(OH) (2'; Figure 2). Thus, solutions of 1 in hexane at 4 8C were exposed to oxygen-free water vapor.…”

“…Thus, the 29 Si NMR spectrum shows two singlet resonance signals at d = À7.9 and À9.6 ppm, which can be unequivocally assigned to the silylene, and two doublets at d = À53.7 and À54.2 ppm for the siloxy 29 Si nuclei. [14] One of the two isomeric forms could be enriched by fractional crystallization and was characterized by X-ray diffraction analysis. In the solid state (Figure 3), the two almost-planar C 3 N 2 Si rings in 4 prefer a gauche conformation relative to each other.…”

Synthesis and Reactivity of Functionalized Silicon(II) Compounds: Iminosilylene, Phosphinosilylene, Hydrosilylene, and Related Compounds

“…The characteristic 13 C NMR chemical shifts for the coordinated carbon of NHCs for 71a and 71b were observed at 160.3 ppm and 159.7 ppm as singlets compared with the chemical shift of free NHC observed at 212 ppm. In the 29 Si NMR spectra, compound 71a showed a chemical shift at ¹68.85 ppm whereas 71b displayed a chemical shift at ¹69.50 ppm as singlets.…”

Synthesis of a α-Chlorosilyl Functionalized Donor-Stabilized Chlorogermylene

“…An increasing number of examples show competitive catalytic activity in different organic transformations [8]. As the complexity of the tetrylenes increases with more intricate ligand architectures [9], functionalization protocols in the presence of uncompromised low-valent Group 14 centers conveniently allow for a comparatively straightforward diversification in the final stages of ligand synthesis. While the interconversion of functional groups is just beginning to emerge in the case of heavier multiple bonds [10], numerous examples have been reported for the heavier tetrylenes [11][12][13][14][15].…”