Iodination of triazenide-bridged rhodium and iridium complexes: oxidative addition vs. one-electron oxidation

Abstract

The triazenide-bridged tetracarbonyls [(OC)₂Rh(µ-p-MeC₆H₄NNNC₆H₄Me-p)₂M(CO)₂] (M = Rh or Ir) undergo oxidative addition of iodine across the dimetal centre, giving the [RhM]⁴⁺ complexes [I(OC)₂Rh(µ-p-MeC₆H₄NNNC₆H₄Me-p)₂M(CO)₂I], structurally characterised for M = Ir. The anionic tricarbonyl iodide [I(OC)Rh(µ-p-MeC₆H₄NNNC₆H₄Me-p)₂Rh(CO)₂]⁻ forms [I₂(OC)Rh(µ-p-MeC₆H₄NNNC₆H₄Me-p)₂Rh(CO)I]⁻ by initial one-electron transfer whereas the analogous tricarbonyl phosphine complexes [(OC)(Ph₃P)Rh(µ-p-MeC₆H₄NNNC₆H₄Me-p)₂M(CO)₂] (M = Rh or Ir) undergo bridge cleavage, giving mononuclear [Rh(p-MeC₆H₄NNNC₆H₄Me-p)I₂(CO)(PPh₃)] and dimeric [I(OC){RNNN(R)C(O)}M(µ-I)₂M{C(O)N(R)NNR}(CO)I] (M = Rh or Ir, R = C₆H₄Me-p) in which CO has been inserted into a metal–nitrogen bond.