Structural Characterization and Reactivity of UO 2 (salophen)L and [UO 2 (salophen)] 2 : Dimerization of UO 2 (salophen) Fragments in Noncoordinating Solvents (salophen = N , N ‘-Disalicylidene- o -phenylenediaminate, L = N , N -Dimethylformamide, Dimethyl Sulfoxide)