A comparison of the results for various complexes suggests that the bromido ligands are more suitable for the generation of the gold(II) complexes than the chlorido ligands. We have investigated this in a more detail using complexes with the 2,2'bipyridine ligand and we have also included the iodo precursors. The aim was to determine the span of the energies that are sufficient to induce the reduction from [(bipy)Au III X2] + to [(bipy)Au II X] + , but insufficient to induce the second reduction step [a] The experimental values were determined from energy-resolved CID experiments (see Experimental and Supporting information S4, S6, S9, S11, S14, S16, S19, S21, S23, S26, S28 and S30).