Two-Coordinate Gallium Ion [tBu3Si-Ga-SitBu3]+ and the Halonium Ions [tBu3Si-X-SitBu3]+ (X = Br, I): Sources of the Supersilyl Cation [tBu3Si]

The ion pair [tBu3Si-Ga-SitBu3][Al(OC(CF3)3)4] was formed quantitatively by treatment of (tBu3Si)2GaCl with Ag[Al(OC(CF3)3)4] in methylene chloride. Single crystals of yellow [tBu3Si-Ga-SitBu3][Al(OC(CF3)3)4] were available from the filtered reaction solution at ambient temperature (space group P21/c). The isolated [tBu3Si-Ga-SitBu3]+ cation is isostructural with isoelectronic [tBu3Si-Zn-SitBu3] and [tBu3Si-Cu-SitBu3]−, respectively. Additionally, the reactions of tBu3SiX (X = Br, I) with Ag[Al(OC(CF3)3)4] are described by which the halonium ions [tBu3Si-X-SitBu3]+ were formed. We found that the two-coordinate Ga cation [tBu3Si-Ga-SitBu3]+ and the halonium ions [tBu3Si-X-SitBu3]+ (X = Br, I) are highly reactive. The salts [tBu3Si-X-SitBu3][Al(OC(CF3)3)4] (X = Ga, Br, I) decompose in CH2Cl2 at room temperature to give tBu3SiF and tBu3SiCl. It is worth mentioning that the ratio of tBu3SiF to tBu3SiCl in these decomposition reactions is the same. We concluded that the same reactive intermediate, the supersilyl cation [tBu3Si]+, was thereby formed.