Formation of Dinuclear Au ^{IIII and Au II /Au IIIIII Mixed‐Valence Complexes is Directed by Structural Constraints Imposed by Cyclophane‐NHC Ligands}

摘要

> The oxidation of dinuclear Au I complexes containing cyclophane‐bis(NHC) ligands by SOCl ₂ , Br ₂ and I ₂ has been investigated. The outcome of the oxidation was dependent on the nature of the cyclophane‐NHC framework. The new complexes were fully characterised by X‐ray diffraction and 1 H and 13 C NMR spectroscopy. When the Au I complex contained an ortho ‐cyclophane framework (dictating short intra‐cation Au ··· Au distances), oxidation resulted in dinuclear Au II complexes of the form X–Au II (NHC) ₂ –Au II (NHC) ₂ –X (X = Cl, Br, I), the Au ··· Au distance being in the range 2.6055(3)–2.6501(1) ?. These Au II complexes are strongly luminescent. When the Au I complex contained an meta ‐cyclophane framework (dictating longer intra‐cation Au ··· Au distances), oxidation with SOCl ₂ or Br ₂ resulted in dinuclear complexes containing Au I and Au III centres of the form X–Au III (NHC) ₂ –X–Au I (NHC) ₂ . NMR studies showed that interconversion of the Au I and Au III sites within the complexes occurred at rates comparable to the NMR timescale.