From Silylone to an Isolable Monomeric Silicon Disulfide Complex

Area of Science:

• Organosilicon Chemistry
• Main Group Chemistry
• Coordination Chemistry

Background:

• Silicon disulfide (SiS2) typically exists as a polymeric chain.
• Stabilization of monomeric silicon species with bulky ligands is challenging.
• N-heterocyclic carbenes (NHCs) are versatile ligands in inorganic chemistry.

Purpose of the Study:

• To synthesize and characterize the first monomeric silicon disulfide stabilized by a bis-N-heterocyclic carbene (bis-NHC) ligand.
• To explore the reactivity of the monomeric silicon disulfide with Lewis acids.
• To investigate the electronic structure and bonding of the novel silicon-sulfur compounds.

Main Methods:

• Reaction of a zero-valent silicon complex with elemental sulfur.
• Lewis acid-base reactions with gallium trichloride (GaCl3).
• Characterization using elemental analysis, HR-MS, IR, NMR spectroscopy, and X-ray diffraction.
• Density Functional Theory (DFT) calculations for bonding analysis.

Main Results:

• Successful synthesis of the bis-NHC stabilized monomeric silicon disulfide, (bis-NHC)SiS2, in 89% yield.
• Formation of a Lewis acid-base adduct, (bis-NHC)Si(S)S→GaCl3, in 91% yield.
• Structural determination of key adducts and DFT analysis revealing polar Si-S bonds with moderate pπ-pπ character.

Conclusions:

• The first bis-NHC stabilized monomeric silicon disulfide has been synthesized and characterized.
• The reactivity with GaCl3 demonstrates the Lewis basicity of the sulfur atoms.
• The study provides fundamental insights into the bonding of silicon-sulfur compounds.