One-step redox route to N-heterocyclic phosphenium ions

One-step reactions of the appropriate N-alkyl-, N-cycloalkyl-, and N-aryl-substituted alpha-diimines with PI3 afforded >80% yields of the triiodide salts of the following N-heterocyclic phosphenium ions, [(R1NC(R2)C(R2)NR1)P]+: 3 (R1 = t-Bu; R2 = H); 4 (R1 = 2,6-i-Pr2C6H3; R2 = H), 5 (R1 = Mes; R2 = H), 6 (R1 = 2,6-i-Pr2C6H3; R2 = H), and 7 (R1 = cyclohexyl; R2 = H). Treatment of 3 and 6 with NaB(C6H5)4 resulted in virtually quantitative yields of the corresponding [B(C6H5)4]- salts 8 and 9, respectively. The X-ray crystal structures of 3 and 5-9 were determined.