The electronic spectra and magnetic susceptibilities of the complexes [UCl6]2–, [UCl4Br2]2–, [UBr6]2–, [UCl4(Ph3PO)2], [UCl4(Et3PO)2], and [UBr4(Ph3PO)2] have been measured. Relative values for the nephelauxetic effects, and the ligand fields, of the ligands have been derived. The possibility of spin-pairing in uranium(IV) is discussed and shown to be unlikely.