Alkoxide and Aryloxide Derivatives of a (Triamidoamine)uranium Complex

The (triamidoamine)uranium chloride complex
[{U(NN3)(μ-Cl)}2]
[NN3 =
N(CH2CH2NSiMe3)3]
reacts with alkali
metal alkoxides and aryloxides to give a range of complexes
[U(NN3)(OR)] (R = But,
t-C4F9, Ph,
2,6-But2-4-MeC6H2). Crystallographic investigations
(including the molecular structure of the
perfluoro-tert-butoxido
derivative
[U(NN3)(O-t-C4F9)]),
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(NN3)(OR)(OR‘)Li(THF)n]
(R, R‘ = But or Ph), are prepared by reaction
of
the corresponding uranium alkoxides with lithium phenoxide or
tert-butoxide. The complex with R = Ph, R‘
=
But, 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(NN3)(OBut)(OPh)Li(THF)]
gives only [U(NN3)(OBut)] on heating
in vacuo.
The one-electron oxidation of these ate complexes to
the three neutral pentavalent compounds
[U(NN3)(OR)(OR‘)] (R, R‘ = But or Ph) has been characterized by
cyclic voltammetric studies and performed on the chemical
scale by reaction with
[FeCp2][PF6].