Reactivity of a triamidoamine complex of trivalent uranium

Abstract

Reduction of [U(NN′3)I] [NN′3 = N(CH2CH2NSiMe2But)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)].