Single Electron Delivery to Lewis Pairs: An Avenue to Anions by Small Molecule Activation

Single electron transfer (SET) reactions are effected by the combination of a Lewis acid (e.g., E­(C6F5)3 E = B or Al) with a small molecule substrate and decamethylferrocene (Cp*2Fe). Initially, the corresponding reactions of (PhS)2 and (PhTe)2 were shown to give the species [Cp*2Fe]­[PhSB­(C6F5)3] 1 and [Cp*2Fe]­[(μ-PhS)­(Al­(C6F5)3)2] 2 and [Cp*2Fe]­[(μ-PhTe)­(Al­(C6F5)3)2] 3, respectively. Analogous reactions with di-tert-butyl peroxide yielded [Cp*2Fe]­[(μ-HO)­(B­(C6F5)3)2] 4 with isobutene while with benzoyl peroxide afforded [Cp*2Fe]­[PhC­(O)­OE­(C6F5)3] (E = B 5, Al 6). Evidence for a radical pathway was provided by the reaction of Ph3SnH and p-quinone afforded [Cp*2Fe]­[HB­(C6F5)3] 7 and [Cp*2Fe]2[(μ-O2C6H4)­(E­(C6F5)3)2] (E = B 8, Al 9). In addition, the reaction of TEMPO with Lewis acid and Cp*2Fe afforded [Cp*2Fe]­[(C5H6Me4NOE­(C6F5)3] (E = B 10, Al 11). Finally, reactions with O2, Se, Te and S8 gave [Cp*2Fe]2[((C6F5)2Al­(μ-O)­Al­(C6F5)3)2]2 12, [Cp*2Fe]2[((C6F5)2Al­(μ-Se)­Al­(C6F5)3)2]2 13, [Cp*2Fe]­[(μ-Te)2(Al­(C6F5)2)3] 14 and [Cp*2Fe]2[(μ-S7)­B­(C6F5)3)2] 15, respectively. The mechanisms of these SET reactions are discussed, and the ramifications are considered.