Three bimetallic platinum/silver nanoclusters, PtAg20(dtp)12 (1), Pt2Ag33(dtp)17 (2), and Pt3Ag44(dtp)22 (3) (dtp: dipropyl dithiophosphate), with cluster electron counts of 8, 16, and 22, respectively, were produced via a one-phase coreduction method. Single-crystal X-ray structures reveal that their inner cores can be visualized as consisting of one, two, and three centered icosahedral Pt@Ag12 units, respectively. In 2 and 3, these units are vertex-sharing and are assembled linearly. Intriguingly, the 22-electron alloy (3) is isolobal to the linear triiodide anion, I3-, and represents the first example of a cluster made of three superatoms whose bonding characteristics are similar to those of a triatomic molecular species.