C(sp3)-H alkenylation promoted by uranyl cation as a visible-light photocatalyst

The alkenylation of cyclic ethers with β-nitroalkenes using uranyl cation as a photocatalyst is reported. Previous studies revealed the feasibility of incorporating organic photocatalyst in the visible light mediated alkenylation, while the uranyl cation serves as an alternative photocatalyst candidate successfully accomplish this transformation through a different pathway. The reaction features the direct hydrogen atom transfer (HAT) process to activate alpha C(sp3)-H of cyclic ether, and consequently cyclic ether is coupled with β-nitroalkene to give the target product with F-selectivity through C-C bond formation.

Uranyl-catalyzed C-H Alkynylation and Olefination

Uranyl cation (UO22+) has been identified as highly oxidizing agent to abstract hydrogen atoms from C-H bonds for the formation of carbon-centered radicals. This work described a photocatalytic strategy to utilize uranyl peroxo complexes for direct alkynylation and olefination of C(sp3) aliphatics. Crystallographic analysis revealed that the in situ generated uranyl peroxide accelerated the reaction.

A chiral uranyl–Kemp’s tricarboxylate cubic framework: structure-directing effect of counterions with three-fold rotational symmetry

In the presence of PPh3Me+ cations, Kemp’s tricarboxylate (kta3–) complexes the uranyl cation to give [PPh3Me][UO2(kta)] (1), a triperiodic framework with cubic symmetry and srs topology. The cation is held...

Uranyl-catalysed C-H Alkynylation and Olefination

This work describes a strategy to utilise uranyl for direct alkynylation and olefination of amides. Uranyl cation (UO22+) has been identified as highly oxidizing agent to abstract hydrogen atoms from...

Supergénne minerály stratiformnej U-Cu mineralizácie pri Spišskej Teplici (hronikum, Kozie chrbty, východné Slovensko)

Occurrence of infiltration, stratiform U-Cu mineralization Spišská Teplica - Vápenica-Vysová is located approximately 7.8 km SW from the district town Poprad and 4.3 km SW from the centre of Spišská Teplica village (Slovak Republic). Primary U-Cu mineralization is bound to arkosic sandstones with abundant coalified fragments of higher plants (Kravany Beds, Upper Permian, Hronicum Unit) and consists of uraninite and pyrite. The chalcopyrite and Cu-S mineral phase (digenite?, roxbyite?) form inclusions in clastic fluorapatite and zircon. Among supergene minerals, malachite and goethite are absolutely dominant, azurite, zálesíite and baryte are less represented. Phosphate, probably of the florencite group, and acanthite were only rarely found. Supergene uranyl minerals were not detected. Their lack, or their weak development in all uranium deposits in Kozie Chrbty Mts. can be explained as follows: during the weathering of primary ores, the cation UO22+ is released from uraninite and coffinite into supergene solutions (uranyl complexes). However, these solutions come into almost immediate contact with fragments of coalified flora (especially in the case of rich U ores), where UO22+ binds to the organic uranyl complexes (complexation). Only a relatively small part of uranyl cation escapes from this geochemical trap, and in that case supergene uranium minerals may precipitate.

Synthesis, Spectroscopic, Thermal and X-Ray Structure of Aminoguanidinium and Hydrazinium Uranyl Trichloroacetates

New aminoguanidinium and hydrazinium uranyl complexes of trichloroacetate with formulae H2(HAgun)2[UO2(Cl3COO)5](NO3 ) (1) and (N2H5)[UO2(Cl3COO)3] (2) where HAgun is aminoguanidinium cation have been prepared in aqueous media and charaterized by analytical, spectral, thermal and X-ray crystallographic studies. The electronic spectra of the complexes confirm the presence of uranyl cation in the molecules. The infrared spectra of the complexes show the N-N stretching frequency of aminoguanidinium in the range of 1100 cm-1 and for hydrazinium in the range of 970 cm-1 conforming their ionic nature. The simultaneous TG-DTA of both the complexes show two step degradation to yield U3O8 as the final residue which was confirmed by X-ray powder diffraction. The structural morphology of U3O8 has been studied by SEM technique. The crystal structure of compound1 reveals seven coordination around uranium with pentagonal bipyramidal geometry. Aminoguanidinium cations and nitrate anion are present outside the coordination sphere as charge compensating species. However, for hydrazine complex hexagonal bipyramidal geometry has been assigned on the basis of analytical and spectral studies.