Synthesis and Reactivity of Trivalent Tp*U(CH2Ph)2(THF): Insertion vs Oxidation at Low-Valent Uranium-Carbon Bonds

The synthesis of a rare uranium(III) bis(benzyl), Tp*U(CH2Ph)(2)(THF) (2), was achieved by salt metathesis of Tp*UI2(THF)(2) with 2 equiv of KCH2Ph at low temperature. This was characterized by H-1 NMR, infrared, and electronic absorption spectroscopy as well as X-ray crystallography. Addition of benzophenone to 2 forms the uranium(IV) radical coupling product Tp*U(CH2Ph)(2)(OC(Ph)(2)CH2Ph) (3), whereas N(3)Mes produces the imido derivative Tp*U(NMes)(CH2Ph)(THF) (4). Adding a further 1 equiv of N(3)Mes to tetravalent 4 results in U-C insertion to form the U(IV) triazenido species Tp*U(NMes)-[(CH2Ph)N-3(Mes)-kappa N-2(1,2)](THF) (5). Compound 2 also reacts with the redox-active 4,6-di-tert-butyl-2-[(2,6-diisopropylphenyl)-imino]quinone ((DIPP)iq) to form the oxidized amido(phenolate) Tp*U(CH2Ph)((DIPP)ap) (6).