Synthesis of dinuclear N-heterocyclic dicarbene Au(III)/Au(III) and Au(II)/Au(II) complexes via oxidative addition of chlorine or bromine to Au(I)/Au(I) species

Oxidative addition of chlorine to dinuclear N-heterocyclic dicarbene gold(I) complexes of formula [Au2(RImeYeImR)2](PF6)2 (R ¼ Me, Y ¼ (CH2)1e4; R ¼ Cy, Y ¼ CH2) affords in high yield stable Au(III)/ Au(III) and Au(II)/Au(II) complexes. The nature of the products depends on the bridge between the two carbene moieties. With Y ¼ methylene, ethylene and butylene, Au(III)/Au(III) dinuclear dicarbene complexes are formed. Only in the case of the propylene bridge the main product is an Au(II)/Au(II) complex. The same reaction output is now proposed also in the oxidative addition of bromine, as fully supported by the X-ray structure of complex [Au2Br2(MeIme(CH2)3eImMe)2](PF6)2.