An isolable NHC-stabilized silylene radical cation: synthesis and structural characterization

Area of Science:

• Organometallic Chemistry
• Silicon Chemistry
• Carbene Chemistry

Background:

• N-heterocyclic carbenes (NHCs) are versatile ligands in organometallic chemistry.
• Silylenes, silicon analogs of carbenes, are reactive species with unique electronic properties.
• Stabilization of silylenes by NHC ligands is an active area of research.

Purpose of the Study:

• To synthesize and characterize a novel silyl-substituted silylene-NHC complex.
• To investigate the one-electron oxidation of the silylene-NHC complex.
• To determine the structural and electronic properties of the resulting NHC-stabilized silylene radical cation.

Main Methods:

• Reductive debromination of a dibromosilane using KC(8) in the presence of an NHC.
• One-electron oxidation using a tris(4-tert-butyldimethylsilyl-2,3,5,6-tetrafluorophenyl)borate salt.
• X-ray crystallography and electron paramagnetic resonance (EPR) spectroscopy for structural and electronic characterization.

Main Results:

• Synthesis and isolation of the air- and moisture-sensitive silylene-NHC complex bis(tri-tert-butylsilyl)silylene-(1,3,4,5-tetramethylimidazol-2-ylidene).
• Successful one-electron oxidation to form the NHC-stabilized silylene radical cation.
• Structural characterization revealed a planar structure for the radical cation with a π-radical nature.

Conclusions:

• The study demonstrates the successful synthesis and stabilization of a silylene-NHC complex.
• The NHC ligand effectively stabilizes the silylene moiety, even upon one-electron oxidation.
• The planar, π-radical nature of the silylene radical cation provides insights into the electronic structure of silicon-based radical species.