Pseudohalide Tectons within the Coordination Sphere of the Uranyl Ion: Experimental and Theoretical Study of C–H···O, C–H···S, and Chalcogenide Noncovalent Interactions

Abstract

A series of uranyl thiocyanate and selenocyanate of the type [RN][UO(NCS)] (R = Bu, MeBz, EtBz), [PhP][UO(NCS)(NO)] and [RN][UO(NCSe)] (R = Me, Pr, EtBz) have been prepared and structurally characterized. The resulting noncovalent interactions have been examined and compared to other examples in the literature. The nature of these interactions is determined by the cation so that when the alkyl groups are small, chalcogenide···chalcogenide interactions are present, but this "switches off" when R = Pr and charge assisted U═O···H-C and S(e)···H-C hydrogen bonding remain the dominant interaction. Increasing the size of the chain toBu results in only S···H-C interactions. The spectroscopic implications of these chalcogenide interactions have been explored in the vibrational and photophysical properties of the series [RN][UO(NCS)] (R = Me, Et, Pr, Bu, MeBz, EtBz), [RN][UO(NCSe)] (R = Me, Pr, EtBz) and [EtN][UO(NCSe)][NCSe]. The data suggest that U═O···H-C interactions are weak and do not perturb the uranyl moiety. While the chalcogenide interactions do not influence the photophysical properties, a coupling of the U═O and δ(NCS) or δ(NCSe) vibrational modes is observed in the 77 K solid state emission spectra. A theoretical examination of representative examples of Se···Se, C-H···Se, and C-H···O═U by molecular electrostatic potentials and NBO and AIM methodologies gives a deeper understanding of these weak interactions. C-H···Se are individually weak but C-H···O═U interactions are even weaker, supporting the idea that the -yl oxo's are weak Lewis bases. An Atoms in Molecules study suggests that the chalcogenide interaction is similar to lone pair···π or fluorine···fluorine interactions. An oxidation of the NCS ligands to form [(UO)(SO)(HO)]·3HO was also noted.

Speciation of Ionic Uranyl-Containing Complexes in in Situ Formed Dicyanonitrosomethanide-Based Ionic Liquids

“…The UO bond lengths are found to be 1.774(2) Å. The U–O and U–N bond lengths are in the range of 2.370(2)–2.4171(19) Å and 2.495(2)–2.496(2) Å (see Table S1), respectively, which are all comparable to those of other uranyl compounds. ,,− The O–U–O, O–U–N, and N–U–N bond angles are in the range of 31.15(8)–180° (Table S2). The sum of U bond valence in compound 1 is estimated to be 6.21, which is close to U­(VI). , Some intermolecular N–H···O interactions are formed between the carbonyl oxygen and nitrous oxygen atoms with the N···O distances being in the range of 2.8858–2.9277 Å (see Table S3 and Figure a).…”

“…Different from compounds 1 and 2 , in the asymmetric unit, there is one lattice water molecule which is also involved in the formation of N–H···O interactions. The average U–O bond lengths at the equatorial planes of compounds 2 and 3 are 2.434(3) and 2.413(3), respectively, which are all comparable to those of other ionic U-containing complexes. ,,− The sums of U bond valence in compounds 2 and 3 are 6.16 and 6.25, respectively.…”

Targeting Diverse Bridging Motifs within Actinide Borosulfates and Establishing an Unconventional Structural Hierarchy

“…Sulfate tetrahedra that are not part of the borosulfate unit each bridge three uranyl pentagonal bipyramids, giving a chain that extends along [010] (Figure 1d), which also occurs in the uranyl sulfate mineral shumwayite 15 as well as other synthetic compounds. 16,17 The structure of TSUBOS-1 also contains a previously reported infinite loop-branched borosulfate chain (Figure 1b). 5,18−20 These are vierer ring chains according to Liebau because they have four-membered rings.…”

A fivefold UO22+ node is a path to dodecagonal quasicrystal approximants in coordination polymers

“…A minor fraction of the solvent is protonated to compensate for the overall negative charge of the U O 2 2+ layers. Although uranyl complexes with five equatorial ligands are commonly observed (21), like in [UO 2 (NCS) 5 ] 3− salts (22), none have ever been reported in which all five ligands are bridging metal centers that would give a pentagonal tiling.…”