| Abstrakt: |
The synthesis, characterization, and reactivity of the homoleptic uranium(IV) alkyls U(CH2C6H5)4(1-Ph), U(CH2-p-CH3C6H4)4(1-p-Me), and U(CH2-m-(CH3)2C6H3)4(1-m-Me2) are reported. The addition of 4 equiv of K(CH2Ar) (Ar = Ph, p-CH3C6H4, m-(CH3)2C6H3) to UCl4at −108 °C produces 1-Phin good yields and 1-p-Meand 1-m-Me2in moderate yields. Further characterization of 1-Phby X-ray crystallography confirmed η4-coordination of each benzyl ligand to the uranium center. Magnetic studies produced an effective magnetic moment of 2.60 μBat 23 °C, which is consistent with a tetravalent uranium 5f2electronic configuration. Addition of 1 equiv of the redox-active α-diimine MesDABMe(MesDABMe= [ArNC(Me)C(Me)NAr]; Ar = 2,4,6-trimethylphenyl (Mes)) to 1-Phresults in reductive elimination of 1 equiv of bibenzyl (PhCH2CH2Ph), affording (MesDABMe)U(CH2C6H5)2(2-Ph). Treating an equimolar mixture of 1-Phand 1-Ph-d28with MesDABMeforms the products from monomolecular reductive elimination, 2-Ph, 2-Ph-d14, bibenzyl, and bibenzyl-d14. This is confirmed by 1H NMR spectroscopy and GC/MS analysis of both organometallic and organic products. Addition of 1 equiv of 1,2-bis(dimethylphosphino)ethane (dmpe) to 1-Phresults in formation of the previously synthesized (dmpe)U(CH2C6H5)4(3-Ph), indicating the redox-innocent chelating phosphine stabilizes the uranium center in 3-Phand prevents reductive elimination of bibenzyl. Full characterization for 3-Ph, including X-ray crystallography, is reported. |
