Complexes featuring a linear [N≡U≡N] core isoelectronic to the uranyl cation

Abstract

The aqueous chemistry of uranium is dominated by the linear uranyl cation [UO2] 2+ , yet the isoelectronic nitrogen-based analogue of this ubiquitous cation, molecular [UN2], has so far only been observed in an argon matrix. Here, we present three different complexes of [UN2] obtained by the reaction of the uranium pentahalides UCl5 or UBr5 with anhydrous liquid ammonia. The [UN2] moieties are linear, with the U atoms coordinated by five additional ligands (ammonia, chloride or bromide), resulting in a pentagonal bipyramidal coordination sphere that is also commonly adopted by the uranyl cation [UO2(L)5] 2+ . In all three cases, the nitrido ligands are further coordinated through their lone pairs by the Lewis acidic ligands [U(NH3)8] 4+ to form almost linear, trinuclear complex cations. Those were characterized by single crystal X-ray diffraction, Raman and IR spectroscopy, 14 N/ 15 N isotope studies, and quantum chemical calculations which support the presence of U≡N triple bonds within the [UN2] moieties.

Reactions of ThX4 (X=F, Cl, Br, I) with Liquid Ammonia‐Crystal Structures and a Theoretical Study of Ammine Thorium(IV) Halide Ammoniates

“…In case of the U complex an already tested and published reference basis set was used leading to similar results compared with the Th complex [40] . The IBOs are shown in Figure 6.…”

“…The scaling factor of harmonic frequencies was set to 1. The published U [40] reference basis set was used for the IBO analysis. For more details on the IBO reference basis set for Th, please see the SI.…”

Synthesis, structure, and reactivity of uranium(vi) nitrides

“…15 f An asymmetric binding mode is also found in the only two reported polynuclear U( vi ) nitrides. 14,8 c In the trinuclear [(NH 3 ) 8 U IV (μ-N)(NH 3 ) 5 U VI (μ-N)U IV (NH 3 ) 8 ]Br 8 ·26NH 3 a U VI N 2 fragment binds two [(NH 3 ) 8 U IV ] 4+ moieties through the bridging nitrides with U VI N bond distances of 1.853(3) and 1.854(3) Å and U IV –N distances of 2.304(3) and 2.300(3) Å. 14 In the dinuclear [Na(DME) 2 ][(NR 2 ) 2 (O)U(μ-N)(CH 2 SiMe 2 NR)U(NR 2 ) 2 ], the NU VI O fragment binds the [U IV (CH 2 SiMe 2 NR)U(NR 2 ) 2 ] moiety trough a bridging nitride with a U VI N bond distance of 1.818(9) Å and a U IV –N distance of 2.284(8) Å.…”

Filling the equatorial garland of uranyl ion: its content and limitations

“…The high oxophilicity [1] of uranium(VI), reflected basically in the nature of its wellknown form as that of uranyl ion, UO2 2+ [2], as well as in the difficulty of obtaining the simple aza-analogue of this cation [3], remains operative in the secondary coordination interactions which give rise to the array of donor atoms lying close to one plane perpendicular to the linear O-U-O unit and found almost universally in compounds regarded formally as containing the uranyl cation [2,4]. X-ray crystallographic studies, especially numerous in the case of carboxylate species [5,6,7], have shown that in the solid state this "equatorial garland" may contain different numbers of donor atoms varying between three (e.g.…”

“…X-ray crystallographic studies, especially numerous in the case of carboxylate species [5,6,7], have shown that in the solid state this "equatorial garland" may contain different numbers of donor atoms varying between three (e.g. [HNEt3][UO2(hexahomotrioxacalix [3]arene -3H)] and related species [8,9] and [Na(thf)2][UO2{N(SiMe3)2}3] [10]) and six (e.g. Na[UO2(OAc)3] [11]), though with five or six being most frequent.…”