Stabilization of Iridium(IV) by Monoanionic Dialkyldiarylguanidinato Ligands

Etectron-rich tris(guanidinato) complexes of Ir-III, [Ir{ArNC(NR2)NAr}(3)] (where R = Me or Et; Ar = Ph or 4-Me6CH4),were synthesized from the respective [Ir{ArNC(NR2)NAr}(C8H14)(2)] precursors (C8H14 = 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 [FeCp2]PF6 afforded isolable, paramagnetic Ir-IV compounds, [Ir{ArNC(NR2)NAr}(3)]PF6, 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.