In the course of structurally characterizing previously reported complexes based on the 1,2-bis(dimethylphosphino)ethane)) (dmpe) ligand ([(dmpe)(2)UCl4] (1) and [(dmpe)(2)UMe4] (2)), we find that adjusting the U/dmpe ratio leads to an unprecedented species. Whereas the use of two or three equivalents of dmpe relative to UCl4 produces 1 as a blue-green solid, the use of a 1:1 dmpe/UCl4 stoichiometry yields [(dmpe)(4)U4Cl16]center dot CH2Cl2 center dot(3 center dot 2CH(2)Cl(2)) as a green solid. In turn, 3 is used to prepare a mixed-chelating ligand complex featuring the bidentate ligand 4,4'-dimethyl-2,2'-bipyridine (dmbpy), [(dmpe)(dmbpy)UCl4] (4). The measured magnetic susceptibilities for 1-4 trend toward nonmagnetic ground states at low temperatures.