page_title: Silylone
section_title: Lewis acids
hierarchical_section_title: Silylone / bis-NHC Stabilized Silylones / Reactivity / Lewis acids
caption_attribution_description: English: Reaction schematic of Lewis acid adducts with bis-NHC stabilized silylone species, as described in Figure 4 of Yao et al. (DOI: 10.1021/acs.accounts.7b00285)
context_page_description: Silylones are a class of zero-valent monatomic silicon complexes, characterized as having two lone pairs and two donor-acceptor ligand interactions stabilizing a silicon center. Synthesis of silylones generally involves the use of sterically bulky carbenes to stabilize highly reactive Si centers. For this reason, silylones are sometimes referred to siladicarbenes. To date, silylones have been synthesized with cyclic alkyl amino carbenes and bidentate N-heterocyclic carbenes. They are capable of reactions with a variety of substrates, including chalcogens and carbon dioxide.
context_section_description: bis-NHC stabilized silylones were found to react in a one- and two-fold fashion with Lewis acids. Xiong et al. reported the formation of the monomeric complex (bis-NHC)Si(GaCl₃) from addition of the Lewis acidic GaCl₃ in THF. X-ray diffraction analysis revealed a C-Si-C bond angle of 88.59(9)° similar to that of the parent silylone, though ²⁹Si{¹H}-NMR revealed larger upfield signal (𝛿ₛᵢ = –119.0 ppm). Yao et al. also reported the reactivity of the silylone with two equivalents of ZnCl₂ in THF to form colorless crystals of (bis-NHC)Si(ZnCl₂)₂. The coordination environment of this complex was observed to be tetrahedral around the silicon by XRD. However, the ZnCl₂ was shown to be asymmetrically coordinated, where one is trigonal planar and the other tetrahedral as a result of additional coordination with a molecule of THF.
  These species were also found to act as a reducing agents, as demonstrated by their ability to reduce GeCl₂(dioxane) to Ge⁰ and NHC->SiCl₂ to form Si⁰ and dinuclear silicon.
caption: Reaction schematic of bis-NHC stabilized silylone with Lewis acids to form adducts.[1]
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