Nitrogen-Based Lewis Acids Derived from Phosphonium Diazo Cations.

Reaction of PPh3 and [(p-ClC6 H4 )N2 ][BF4 ] affords [(p-ClC6 H4 )N(PPh3 )N(PPh3 )][BF4 ] 1, while reaction with (Ph2 PCH2 )2 gave [(p-ClC6 H4 )(NPh2 PCH2 )2 )][BF4 ] 2. These species confirm the Lewis acidity of [(p-ClC6 H4 )N2 (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-ClC6 H4 )N2 (PtBu3 )]. 5. Combination of 3 and PtBu3 acts as an FLP to effect (SPh)2 cleavage, generating [PhSPtBu3 ]+ and the radical [ArN2 (PR3 )]. . Collectively, these data affirm the ability of the cations [ArN2 (PR3 )]+ to behave as one or two electron acceptors.