Structural and spectroscopic characterization of a charge-separated uranium benzophenone ketyl radical complex

The reaction of [((t-BuArO)(3)tacn)U-III (1) with 4,4'-di-tert-butylbenzophenone affords a unique isolable U(IV) ketyl radical species [((t-BuArO)(3)tacn)U-IV(OC center dot(t-Bu) Ph-2)] (2) supported by XRD data, magnetization measurements, and DFT calculations. Isolation and full characterization of the corresponding diphenyl methoxide complex [((t-BuArO)(3)tacn)U-IV(OCHt-BuPh2)] (3) is also presented. The one-electron reduction of benzophenone by [(((ArO)-Ar-Ad)(3)tacn)U-III] (4) leads to a purple U(IV) ketyl radical intermediate [(((ArO)-Ar-Ad)(3)-tacn)U-IV(OC center dot Ph-2)] (5). This species is highly reactive, and attempts at isolation were unsuccessful and resulted in methoxide complex [(((ArO)-Ar-Ad)(3)tacn)U-IV(OCHPh2)] (6) from H abstraction and dinuclear para-coupled complex [(((ArO)-Ar-Ad)(3)tacn)U-IV(OCPhPh-CPh2O)U-IV(((ArO)-Ar-Ad)(3)tacn)] (7).