Nitrogen-Based Lewis Acids Derived from Phosphonium Diazo Cations

Reaction of PPh3 and [(p-ClC6H4)N-2][BF4] affords [(p-ClC6H4)N(PPh3)N(PPh3)][BF4] 1, while reaction with (Ph2PCH2)(2) gave [(p-ClC6H4)(NPh2PCH2)(2))][BF4] 2. These species confirm the Lewis acidity of [(p-ClC6H4)N-2(PR3)][BF4] cations at N. In contrast, use of bulky phosphines afford the species [ArN2(PR3)][BF4] (R=tBu 3, Mes 4). Compound 3 undergoes one electron reduction to give the stable radical [(p-ClC6H4)N-2(PtBu3)](center dot) 5. Combination of 3 and PtBu3 acts as an FLP to effect (SPh)(2) cleavage, generating [PhSPtBu3](+) and the radical [ArN2(PR3)](center dot). Collectively, these data affirm the ability of the cations [ArN2(PR3)](+) to behave as one or two electron acceptors.