Abstract: Ever since Lappert and coworkers isolated the first examples of crystallographically characterizable La(II) and Ce(II) complexes in 2008, molecular complexes containing rare-earth metals in the +2 oxidation state have been isolated for the rest of the series, except for radioactive Pm. The +2 oxidation state has also been identified for the actinide metals Th, U, Np, and Pu as well. Although there are now several different ligand environments that support these low-oxidation state metal ions, the factors that influence the isolation and properties of these ions remain unclear.  The research described in this Dissertation details a series of exploratory synthetic studies aimed at understanding the role that steric and electronic effects play in the isolation and properties of reduced rare-earth metal and actinide metal coordination complexes.  Specifically, ancillary ligand effects will be studied through subtle variations in the ligands employed to evaluate how these systematic changes affect the thermal stability, reactivity, and structures of the resulting compounds.