Anion stability in stannylium, oxonium, and silylium salts of the weakly coordinating anion [C6F4-1,2-{B(C6F5)2}2(μ-OCH3)]-

Reaction of [Ph3C](+)[C6F4-1,2-{B(C6F5)(2)}(2)(mu-OCH3)](-), 1, with Bu3SnH gives the solvated stannylium ion [Bu3Sn(arene)](+)[C6F4-1,2-{B(C6F5)(2)}(2)(mu-OCH3)](-), 2, as a light brown oil (delta(119)Sn = 434 ppm). This material is thermodynamically stable toward transfer of the chelated OMe- anion to "Bu3Sn4" as evidenced by the reaction of free diborane C6F4-1,2-[B(C6F5)(2)](2) with 2 equiv of Bu3SnOMe. This reaction produces the stannyloxonium complex [(Bu3Sn)(2)OCH3](+)[C6F4-1,2-{B(C6F5)(2)}(2)(mu-OCH3)](-), 3 (delta(119)Sn = 277 ppm), which is stable at -60 degreesC. Upon warming, the cation in 3 undergoes decomposition to unidentified products, while the anion remains intact. Ion pair 2 reacts rapidly with ethereal HCl in CH2Cl2 to generate Bu3SnCl and the oxonium acid [(Et2O)(2)H](+)[C6F4-1,2-{B(C6F5)(2)}(2)(mu-OCH3)](-), 4, isolated in 76% yield as a white, crystalline solid. Acid 4 is thermally stable in solution and was characterized crystallographically. The C2B2OMe core of the anion in 4 deviates from planarity due to intermolecular interactions in the crystal, in contrast to the structures found in other ion pairs with this anion. Reaction of 2 with anhydrous HCl gives the unsymmetrical MeOH adduct of C6F4-1,2-[B(C6F5)(2)](2), 5, which was separately synthesized by direct reaction of methanol with the free diborane. The anion [C6F4-1,2-{B(C6F5)(2)}(2)(mu-OCH3)](-) is not stable in the presence of the triethylsilylium ion, generated from 1 and Et3SiH.