Neodymium tri-iodide reacts with Group 12 metal (M; M = Zn, Cd, Hg) iodides to form heterometallic compounds. These Lewis acidic M cleave Nd-I bonds to give either ionic {[(THF)(5)NdI2][MI3THF]; M = Zn, Cd} or charge-neutral {(THF)(5)NdI(mu(2)I)HgI3} compounds. Differences in structure are interpreted primarily in terms of M-L bond strengths, rather than Nd-L bond strengths. Experiments with Yb indicate that if there is any excess iodide present in these syntheses then the most readily isolated product is a triiodide salt, i.e., [(THF)(5)Yb-2][I-3]. In conventional solvents the presence of Lewis acid is not required for iodide displacement-from pyridine, "YbI3" crystallizes as [(py)(5)YbI2][I]. These compounds are potentially useful as heterometallic sources of lanthanide-doped iodide matrixes, they illustrate the ease with which iodides are displaced from lanthanide coordination spheres, and they underscore the complexity associated with using lanthanide iodides as Lewis acid catalysts.