[Ag(COD)(2)]PF(6) catalyzes the ring-opening of N-tosylaziridines and -azetidines with alcohols, amines, thiols, and related tethered 1,2-ethane dinucleophiles. Initial rate studies and DFT-based evaluation of stepwise energetics suggest an inverse relationship between the nucleophilic reactivity of a heteroatom donor and its binding affinity to cationic Ag(I).