Reduction–oxidation properties of organotransition-metal complexes. Part 27. Mixed-valence triazenido-bridged di-iridium compounds

Abstract

The complex [{Ir(µ-Cl)(η⁴-cod)}₂](cod = cyclo-octa-1,5-diene) reacts with the triazene RNNNHR (R =p-tolyl) to give [IrCl(RNNNHR)(η⁴-cod)](1) which yields [IrCl(CO)₂(RNNNHR)](2) on treatment with CO gas. Deprotonation of (2) with NEt₃ in CH₂Cl₂ at –10 °C gives the dimer [{Ir(CO)₂(µ-RNNNR)}₂](3), which undergoes thermal substitution with PPh₃ to yield [Ir₂(CO)₃(PPh₃)(µ-RNNNR)₂](4). Complexes (3) and (4) undergo reversible one-electron oxidation at a platinum electrode in CH₂Cl₂. In the presence of PPh₃, (4)[or (3)] reacts with [Fe(η-C₅H₅)₂][PF₆] to give the isolable paramagnetic salt [{Ir(CO)(PPh₃)(µ-RNNNR)}₂][PF₆] which undergoes reversible one-electron reduction and which has been characterised by e.s.r. spectroscopy.