Systematic B3LYP/6-31G* and B3LYP/6-311+G* calculations have been performed for families of closo-borane, alane, and gallane clusters consisting of A12H122- (A = B, Al, and Ga) cages with endohedral or exohedral Ln+ metal cations (Ln+ = Li+, Na+, Cu+, Be2+, Mg2+, Zn2+, Al+, Al3+, Ga+, and Ga3+). Exohedral structure 1, with tridentate cation coordination at an icosahedron face, is a global minimum for most species; bidentate coordination (structure 2) is the transition state for cation migration around the dianion exterior. Migrational barriers (hmigr), which range from 3 to 5 kcal/mol for monocations and 10−15 kcal/mol for dications, increase with increased cation charge and increased cationic radius. Ln+@B12H122- (Ln+ = Li+, Be2+, Na+, Mg2+, Al3+), Ln+@Al12H122- (Ln+ = Li+, Na+, Mg2+, Al+), and Ln+@Ga12H122- (Ln+ = Li+, Na+, Mg2+, Ga3+) endohedral clusters, with their cations located at the A12H122- cage centers, are local Ih minima (3). Endohedral−exohedral isomer relative energies, Erel(3/1), which are...