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(RIm–Y–ImR)2](PF6)2 (R = Me, Y = (CH2)1–4; R = Cy, Y = 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 = 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(MeIm–(CH2)3–ImMe)2](PF6)2.