A Radical Mechanism for Frustrated Lewis Pair Reactivity

The frustrated Lewis pairs (FLPs) derived from tBu(3)P and E(C6F5)(3) (E = B, Al) react with pO(2)C(6)Cl(4) and Ph3SnH to give [tBu(3)POC(6)Cl(4)OE(C6F5)(3)] (E = B 1, Al 2), [tBu(3)PSnPh(3)][HB(C6F5)(3)](3), and [tBu(3)PSnPh(3)][(m-H)(Al(C6F5)(3))(2)] 4. These products form via the accepted two-electron process involving a transient encounter complex.'' In contrast, the corresponding reactions of Mes(3)P and E(C6F5)(3) (E = B, Al) with pO(2)C(6)Cl(4) give [(Mes(3)POC(6)Cl(4)OE(C6F5)(3)] (E = B 8, Al 9); however, the identification of the intermediates [Mes(3)P center dot](2) [(C6F5)(3)EOC6Cl4OE(C6F5)(3)] (E = B 5, Al 6) supports a mechanism that proceeds via a single-electron transfer process. This is further supported by the reactions of Mes(3)P and E(C6F5)(3) (E = B, Al) with Ph3SnH, which yielded [Mes(3)PH] [HB(C6F5)(3)] 10 and [Mes(3)PH][(m-H)(Al(C6F5)(3))(2)] 11, respectively, with the concurrent formation of Ph3SnSnPh3.