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)(mu-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)(mu-O)] which could also be prepared directly by reaction of trimethylamine N-oxide with [U(NN'(3))]

Uranium triamidoamine chemistry

“…17 Very early on the potential novelty of Tren-uranium complexes was highlighted by the observation that freeze-thaw degassed solutions of 11 placed under an atmosphere of dinitrogen change colour from purple to red. 17 The HMPA molecule in 14 coordinates through the oxygen atom; the NMR and absorption spectra for 13 and 14 are typical of uranium(III) species. 18 Inspection of the characterisation data for 12 initially suggested a U III -N 2 -U III bonding picture with no increase in valency for the uranium centres and a neutral N 2 ligand; however, with advances in computational and spectroscopic techniques it was later suggested that in fact the solid state data for 12 were somewhat misleading and a more likely bonding situation is that of a reduced N 2 unit coordinated to uranium(IV) centres consistent with U -N 2 backbonding.…”

Uranium-mediated oxidative addition and reductive elimination

“…In 2002, Scott and co-workers reported reactions between two equivalents of the U(III) complex [U(NN′ 3 15 The reactions are formally type (b) oxidative additions, whilst the NN′ 3 triamidoamine ligand acts as an inert supporting ligand. In 2009, Boncella and co-workers reported reactions between a U(V) bridging imido dimer (7) and Ph-E-E-Ph (E = S, Se, Te), which produced a series of U(VI) trans-bis-imide products (Scheme 5).…”

Uranium-sulfilimine chemistry. Hydrolysis of Cp*2UCl2 with HNSPh2·H2O and the crystal structure of Cp*2UCl(OH)(HNSPh2), a metallocene terminal hydroxy complex of tetravalent uranium

“…A few actinide metallocene hydroxides have been reported [1,2] and there are a few lanthanide analogues [3][4][5][6][7][8][9][10][11]. For the actinindes several closely related, but not formally organometallic, molecular complexes have been structurally characterized [12,13]. The preparation of f-element hydroxides generally involves controlled hydrolysis of a suitable metal precursor.…”