Alkoxide and Aryloxide Derivatives of a (Triamidoamine)uranium Complex

The (triamidoamine)uranium chloride complex [{U(NN(3))(&mgr;-Cl)}(2)] [NN(3) = N(CH(2)CH(2)NSiMe(3))(3)] reacts with alkali metal alkoxides and aryloxides to give a range of complexes [U(NN(3))(OR)] (R = Bu(t), t-C(4)F(9), Ph, 2,6-Bu(t)(2)-4-MeC(6)H(2)). Crystallographic investigations (including the molecular structure of the perfluoro-tert-butoxido derivative [U(NN(3))(O-t-C(4)F(9))]), molecular weight determinations, and NMR spectroscopic data are consistent with these molecules being monomeric with a 3-fold symmetric arrangement of the triamidoamine fragment. The three turquoise ate complexes [U(NN(3))(OR)(OR')Li(THF)(n)()] (R, R' = Bu(t) or Ph), are prepared by reaction of the corresponding uranium alkoxides with lithium phenoxide or tert-butoxide. The complex with R = Ph, R' = Bu(t), n = 1 is shown by X-ray crystallography to have a capped trigonal bipyramidal structure. A lithium atom is incorporated into the ligand sphere by coordination to an amido nitrogen and a tert-butoxido oxygen. The mixed alkoxide ate complex [U(NN(3))(OBu(t))(OPh)Li(THF)] gives only [U(NN(3))(OBu(t))] on heating in vacuo. The one-electron oxidation of these ate complexes to the three neutral pentavalent compounds [U(NN(3))(OR)(OR')] (R, R' = Bu(t) or Ph) has been characterized by cyclic voltammetric studies and performed on the chemical scale by reaction with [FeCp(2)][PF(6)].