Unbridged Rh(ii)–Rh(ii) complexes of N-heterocyclic carbenes and reactions with O2 to form dirhodium(μ–η1:η1-O2) complexes

Abstract

Dimeric rhodium(II) complexes and rhodium(III) peroxide complexes supported by N-heterocyclic carbenes were synthesized. The treatment of [Ag₃(L)₂](PF₆)₃ (L = bis(N-pyridylimidazolylidenyl)methane) with [Rh(COD)Cl] afforded [Rh(L)(CH₃CN)]₂(PF₆)₄ in which two [Rh(L)] moieties are bound together via an unsupported Rh–Rh bond. The substitution of axial acetonitrile by phosphines led to the insertion of O₂ into the Rh–Rh bond and the isolation of [Rh(L)(PPh₃)]₂(μ–η¹:η¹-O₂)(PF₆)₄ and [Rh(L)(PCy₃)]₂(μ–η¹:η¹-O₂) (PF₆)₄.