Rationale: These experiments were conducted to measure the diversity of organo-U(IV) and U(III) ions created using multidimensional tandem MS and collision-induced dissociation of halogen-substituted U ^VIO ₂-phenide complexes [UO ₂(C ₆H ₃FX)] ⁺, X = Cl, Br, or I. Methods: Samples of UO ₂(O ₂C-C ₆H ₃FX) ₂ were prepared by digesting UO ₃ with appropriate halogen-substituted carboxylic acids in deionized water. Solutions for ESI were created by diluting the digested sample in 50:50 H ₂O/CH ₃OH. Precursor ions for multiple-stage tandem MS were generated by electrospray ionization (ESI). Multiple-stage collision-induced dissociation (He collision gas) in a linear quadrupole ion trap mass spectrometer was used to prepare species such as [U ^IVFX(C≡CH)] ⁺ and U ^IIIF(C≡CH)] ⁺ for subsequent study of ion-molecule reactions with adventitious neutrals in the ion trap. Results: Multiple-stage CID of the [UO ₂(C ₆H ₃FX)] ⁺, X= Cl, Br, or I, complexes caused removal of both “yl” oxo ligands from of the UO ₂ ²⁺ moiety to create ions such as [U ^IVFX(C≡CH)] ⁺ and [U ^IIIFX] ⁺. For [U ^IVFXC≡CH] ⁺ and [U ^IIIFC≡CH] ⁺ products, hydrolysis to generate [U ^IVFX(OH)] ⁺ and [U ^IIIF(OH)] ⁺, with concomitant loss of HC≡CH, was observed. When X = Cl and Br, elimination of HX was competitive with loss of HC≡CH. CID of [UO ₂(C ₆H ₃FBr)] ⁺ and [UO ₂(C ₆H ₃FI)] ⁺ caused reductive elimination of the respective halogen radicals to generate interesting organo-U(III) species such as [U ^IIIF(C≡CH)] ⁺ and [U ^IIIC ₂] ⁺. Conclusions: The use of “preparative” tandem mass spectrometry and a suite of halogen substituted benzoic acid ligands can be used to remove both oxo ligands of UO ₂ ²⁺ and generate a group of homologous organo-U(IV) and organo-U(III) ions for studies of intrinsic reactivity.