The octahedral complex Ag^III(CF₃)₃tpy (2_Ag), attainable from Ag^III(CF₃)₃py (1_Ag) and terpyridine (tpy), has been isolated and characterized using NMR spectroscopy and Sc-XRD. Strikingly, 2_Ag proved to be diamagnetic and showed tridentate coordination of the tpy ligand, thus forging an unprecedented 20-valence-electron Ag^III complex. A comparative structural and theoretical study on the bonding of 2_Ag vs. the coinage metal analogues 2_M has unveiled the preferred six-coordination in the lighter counterparts, 2_Cu and 2_Ag, while five-coordination is favored in 2_Au. A rationale to the unexpected diamagnetism of 2_Ag is also provided..