We report the synthesis and use of an easy-to-prepare, bulky, and robust aryloxide ligand starting from inexpensive precursor materials. Based on this aryloxide ligand, two reactive, coordinatively unsaturated U(III) complexes were prepared that are masked by a metal-arene interaction via δ-backbonding. Depending on solvent and uranium starting material, both a tetrahydrofuran (THF)-bound and Lewis-base-free U(III) precursor can easily be prepared on the multigram scale. The reaction of these trivalent uranium species with nitrous oxide, N2O, was studied and an X-ray diffraction (XRD) study on single crystals of the product revealed the formation of a five-coordinate U(V) oxo complex with two different molecular geometries, namely, square pyramidal and trigonal bipyramidal.

An inverse trans influence has been observed in a high-valent U(V) imide complex, [(((Ad)ArO)(3)N)U(NMes)]. A thorough theoretical evaluation has been employed in order to corroborate the ITI in this unusual complex. Computations on the target complex, [(((Ad)ArO)(3)N)U(NMes)], and the model complexes [(((Me)ArO)(3)N)U(NMes)] and [(NMe(3))(OMe(2))(OMe)(3)U(NPh)] are discussed along with synthetic details and supporting spectroscopic data. Additionally, the syntheses and full characterization data of the related U(V) trimethylsilylimide complex [(((Ad)ArO)(3)N)U(NTMS)] and U(IV) azide complex [(((Ad)ArO)(3)N)U(N(3))] are also presented for comparison.

We recently reported the formation of a bridging carbonate complex [{(((Ad)ArO)(3)N)U}(2)(μ-η(1):κ(2)-CO(3))] via reductive cleavage of CO(2), yielding a μ-oxo bridged complex, followed by the insertion of another molecule of CO(2). In a similar strategy, we were able to isolate and characterize a series of mixed carbonate complexes U-CO(2)E-U, U-CS(2)E-U, and even U-OC(S)Se-U, by reacting bridged chalcogenide complexes [{(((Ad)ArO)(3)N)U}(2)(μ-E)] (E = S, Se) with CO(2), CS(2), and COS. These chalcogenido mixed-carbonate complexes represent the first of their kind.

We report the syntheses, electronic properties, and molecular structures of a series of polychalcogenidobridged dinuclear uranium species. These complexes are supported by the sterically encumbering but highly flexible, single N-anchored tris(aryloxide) chelator (Ad ArO) 3 N 3À. Reaction of an appropriate uranium precursor, either the U(III) starting material, [((Ad ArO) 3 N)U(DME)], or the dinuclear monochalcogenido-bridged uranium(IV/IV) compounds [{((Ad ArO) 3 N)U(DME)} 2 (m-E)] (E ¼ S, Se), with elemental sulfur or selenium, yields new complexes with a variety of bridging chalcogenide entities mE m nÀ (E ¼ S, m ¼ 2, n ¼ 1 or 2 and E ¼ Se, m ¼ 2, 4; n ¼ 2). Activation of the heavy chalcogens typically requires either a coordinatively unsaturated, strongly-reducing metal complex or a compound with a metalmetal bond. Since uranium complexes in the +IV oxidation state, are generally considered rather unreactive, the observed reaction of the here employed uranium(IV)/(IV) species with elemental chalcogens is fairly remarkable.

Reductive elimination from U(CH 2 Ph) 4 (1-Ph) mediated by 4,6-di-tert-butyl-2-[(2,6-diisopropylphenyl)imino]quinone ( dipp iq) was observed, resulting in the formation of ( dipp ap) 2 U(CH 2 Ph) 2 (THF) 2 (2) ( dipp ap = 4,6di-tert-butyl-2-[(2,6-diisopropylphenyl)amido]phenolate) and bibenzyl. The crossover experiment with U(CD 2 C 6 D 5 ) 4 showed formation of bibenzyl-d 7 , indicating that reductive elimination occurs in a stepwise fashion via benzyl radical extrusion, presumably through an iminosemiquinone tris-(benzyl) intermediate, ( dipp isq)U(CH 2 Ph) 3 . Synthesis of this intermediate was attempted by addition of the iminoquinone ligand to UI 3 (THF) 4 to form ( dipp isq)UI 3 (3), followed by alkylation with 3 equiv of benzylpotassium. However, this only resulted in the isolation of 2. Reduction of 3 with KC 8 afforded the amidophenolate diiodide species ( dipp ap)UI 2 (THF) 2 ( 4), maintaining the tetravalent oxidation state of the uranium and reducing the ligand. Attempts at the formation of 2 via addition of 2 equiv of benzylpotassium to 4 resulted in decomposition. The uranium mono(alkyl) ( dipp ap)UI(CH 2 Ph)(THF) 2 (5) was observed upon addition of 1 equiv of benzylpotassium to 4. All products have been characterized by 1 H NMR and electronic absorption spectroscopy. X-ray crystallography was employed to ascertain ligand reduction in 2, 3, and 5.

Reaction of [((AdArO)3N)UIII(DME)] with EH2 (E = S, Se, Te) yields a complete series of mono- and dinuclear uranium(iv) hydrochalcogenide complexes.

While uranium hydridoborate complexes containing the [BH4](-) moiety have been well-known in the literature for many years, species with functionalized borate centers remained considerably rare. We were now able to prepare several uranium hydridoborates (1-4) with amino-substituted borate moieties with high selectivity by smooth reaction of [Cp*2UMe2] (Cp* = C5Me5) and [Cp'2UMe2] (Cp' = 1,2,4-tBu3C5H2) with the aminoborane H2BN(SiMe3)2. A combination of nuclear magnetic resonance spectroscopy, deuteration experiments, magnetic SQUID measurements, and X-ray/neutron diffraction studies was used to verify the anticipated molecular structures and oxidation states of 1-4 and helped to establish a linear tridentate coordination mode of the borate anions.