All the Lanthanides Do It and Even Uranium Does Oxidation State +2

It takes two to tango: The “reduced”, divalent lanthanides M2+ have electronic ground-state configurations of either 4fn+15d0 (blue) or 4fn5d1 (red). The latter may be incorporated in the spacious anions [M(Cp′)3]− and thus the single d1 trapped in a z2 like SOMO. This chemistry has now been transcribed to U2+ (5f36d1), a much sought-after species.