Synthesis of 1,1′-Bis(1-Methyl/Chloro-2,3,4,5-Tetraphenyl-1-Silacyclopentadienyl) [Ph₄C₄Si(Me/Cl)-(Me/Cl)SiC₄Ph₄] from Silole Anion [MeSiC₄Ph₄]⁻•[Li⁺ or Na⁺] and Silole Dianion [SiC₄Ph₄]²⁻•2[Li⁺]; Oxidative Coupling of Silole Anion [MeSiC₄Ph₄]⁻•[Li⁺ or Na⁺] by Ferrous Chloride (FeCl₂) and Oxidative Coupling and Chlorination of Silole Dianion [SiC₄Ph₄]²⁻•2[Li⁺] by Cupric Chloride (CuCl₂)

Abstract

A reaction of silole anion {[MeSiC4Ph4]−•[Li+ or Na+] (1) with anhydrous ferrous chloride (FeCl2) in THF (tetrahydrofuran) gives 1,1′-bis(1-methyl-2,3,4,5-tetraphenyl-1-silacyclopentadienyl) [Ph4C4Si(Me)-(Me)SiC4Ph4] (2) with precipitation of iron metal in high yield. Silole dianion {[SiC4Ph4]2−•2[Li+] (3) is added to anhydrous cupric chloride (CuCl2) in THF at −78 °C, then the dark red solution changes into a greenish solution. From the solution, a green solid is isolated, and stirring it in toluene at room temperature provides quantitatively 1,1′-bis(1-chloro-2,3,4,5-tetraphenyl-1-silacyclopentadienyl) [Ph4C4Si(Cl)-(Cl)SiC4Ph4] (4) with precipitation of copper metal in toluene. The green solid is suggested to be 1,1′-bissilolyl bisradical [Ph4C4Si-SiC4Ph4]2• (8), and lithium cuprous chloride salts {[Li2CuICl2]+•[CuICl2]−}. Both reactions are initiated by single-electron transfer (SET) from the electron-rich anionic silole substrates (1 and 3) to iron(II) and copper(II).

Keywords

• silole
• anion
• dianion
• oxidation
• oxidative-chlorination
• set (single-electron transfer)
• cupric chloride
• ferrous chloride