Stabilization of iridium(IV) by monoanionic dialkyldiarylguanidinato ligands

Electron-rich tris(guanidinato) complexes of Ir(III), [Ir{ArNC(NR(2))NAr}(3)] (where R = Me or Et; Ar = Ph or 4-MeC(6)H(4)), were synthesized from the respective [Ir{ArNC(NR(2))NAr}(C(8)H(14))(2)] precursors (C(8)H(14) = cis-cyclooctene), are air-sensitive, and can be electrochemically oxidized in two one-electron transfer steps. The first electron transfer is reversible and occurs at much lower potentials than typical for Ir(III). Chemical oxidation by [FeCp(2)]PF(6) afforded isolable, paramagnetic Ir(IV) compounds, [Ir{ArNC(NR(2))NAr}(3)]PF(6), which were characterized by analytical and spectroscopic methods and a single-crystal structure determination, demonstrating that Ir(IV) is accessible in a nitrogen-donor ligand environment.