A Radical Mechanism for Frustrated Lewis Pair Reactivity

Abstract

Summary The frustrated Lewis pairs (FLPs) derived from t Bu 3 P and E(C 6 F 5 ) 3 (E = B, Al) react with p O 2 C 6 Cl 4 and Ph 3 SnH to give [ t Bu 3 POC 6 Cl 4 OE(C 6 F 5 ) 3 ] (E = B 1 , Al 2 ), [ t Bu 3 PSnPh 3 ][HB(C 6 F 5 ) 3 ] 3 , and [ t Bu 3 PSnPh 3 ][(μ-H)(Al(C 6 F 5 ) 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(C 6 F 5 ) 3 (E = B, Al) with p O 2 C 6 Cl 4 give [(Mes 3 POC 6 Cl 4 OE(C 6 F 5 ) 3 ] (E = B 8 , Al 9 ); however, the identification of the intermediates [Mes 3 P·] 2 [(C 6 F 5 ) 3 EOC 6 Cl 4 OE(C 6 F 5 ) 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(C 6 F 5 ) 3 (E = B, Al) with Ph 3 SnH, which yielded [Mes 3 PH][HB(C 6 F 5 ) 3 ] 10 and [Mes 3 PH][(μ-H)(Al(C 6 F 5 ) 3 ) 2 ] 11 , respectively, with the concurrent formation of Ph 3 SnSnPh 3 .