Reactivity of a triamidoamine complex of trivalent uranium

Abstract

Reduction of [U(NN′₃)I] [NN′₃ = N(CH₂CH₂NSiMe₂Bu^t)₃] with potassium in pentane gives the purple trivalent monomer [U(NN′₃)] in good yield, this compound having previously been synthesised via fractional vacuum sublimation of mixed-valent [{U(NN′₃)}₂(μ-Cl)]. The magnetic susceptibility of this compound is consistent with the presence of U(III) centres, and this is confirmed by a characteristic near IR spectrum. Its reactions with Lewis bases to give e.g. [U(NN′₃)(Py)] and [U(NN′₃)(HMPA)] are reported, along with the molecular structure of the latter. The complex [U(NN′₃)] is readily oxidised, imido and hydrazido complexes being formed readily by reaction with trimethylsilyl-azide and -diazomethane, respectively. The reaction with methylene trimethylphosproane however led to the formation of an addition compound [U(NN′₃)(CH₂PMe₃)]. Reaction of this latter complex with air gave a few crystals of the unusual hydroxo complex [U(NN′₃)(OH)(CH₂PMe₃)] which was structurally characterised. Reaction of [U(NN′₃)(CH₂PMe₃)] with trimethylamine N-oxide gave pentavalent [U(NN′₃)(O)], or perhaps a dimer thereof. The latter complex reacted with [U(NN′₃)] to give the bridging oxo complex [{U(NN′₃)}₂(μ-O)] which could also be prepared directly by reaction of trimethylamine N-oxide with [U(NN′₃)].