Fig. shows the electrospray ionization (ESI) mass spectra of 20•(Cl -)3 (Fig. , Fig. )) and the product obtained by mixing 20•(Cl -)3 with Fe(BF4)2. The mass spectrum of the product featured peaks corresponding to [Au13(dppe)5(PA)2-xClx](BF4)3 (x = 0-2). This finding indicates that during the reaction, ligand exchange occurred between the counteranion Cl -of the Au13 cluster and PA (Equation ). Thus, (1) the Cl -changes its role from a counteranion to a ligand depending on the reaction conditions and (2) under conditions where Cl -ions are present, ligand exchange occurs from the acetylide ligand to Cl -.