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.