Stabilization of Iridium(IV) by Monoanionic Dialkyldiarylguanidinato Ligands

Abstract

Electron-rich tris(guanidinato) complexes of IrIII, [Ir{ArNC(NR2)NAr}3] (where R = Me or Et; Ar = Ph or 4-MeC6H4), 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 IrIII. Chemical oxidation by [FeCp2]PF6 afforded isolable, paramagnetic IrIV compounds, [Ir{ArNC(NR2)NAr}3]PF6, which were characterized by analytical and spectroscopic methods and a single-crystal structure determination, demonstrating that IrIV is accessible in a nitrogen-donor ligand environment.