Two oxo-containing neptunium(IV) tert-butoxides, Np3O(O t Bu)10 (1) and K4Np2O(O t Bu)10 (2), were synthesized using the ligand substitution between neptunium(IV) silylamides and HO t Bu, whereas ...the salt metathesis between NpCl4(DME)2 (DME = dimethoxyethane) and various amounts of LiO t Bu resulted in the formation of oxo-free alkoxides Np(O t Bu)4(py)2 (3; py = pyridine) and Li(THF)2Np(O t Bu)6 (4; THF = tetrahydrofuran). These complexes are the first structurally characterized neptunium(IV) alkoxides using single-crystal X-ray diffraction and solid-state absorption spectroscopy, which provide data for the development of anhydrous metal–organic neptunium chemistry.
Two neptunium(III) mellitates, 237Np2(mell)(H2O)9·1.5H2O (Np-1α) and 237Np2(mell)(H2O)8·2H2O (Np-1β), have been synthesized from 237NpCl4(dme)2 by reduction with KC8 and subsequent reaction with ...an aqueous solution of mellitic acid (H6mell). Characterization by single-crystal X-ray crystallography and UV–vis–NIR spectroscopy confirms that the neptunium is in its +3 oxidation state and both polymorphs are isostructural to the previously reported plutonium mellitates. Of the two morphologies, Np-1α is indefinitely stable in air, while Np-1β slowly oxidizes over several months. This is due to the change in the energy of the metal-ligand charge-transfer absorption exhibited by these compounds attributed to differing numbers of carboxylate bonds to Np(III), where in Np-1β the energy is low enough to result in spontaneous oxidation.
In this manuscript we evaluate the X‐ray structure of five new pertechnetate derivatives of general formula M(H2O)4(TcO4)2, M=Mg, Co, Ni, Cu, Zn (compounds 1–5) and one perrhenate compound ...Zn(H2O)4(ReO4)2 (6). In these complexes the metal center exhibits an octahedral coordination with the pertechnetate units as axial ligands. All compounds exhibit the formation of directional Tc⋅⋅⋅O Matere bonds (MaBs) that propagate the M(H2O)4(TcO4)2, into 1D supramolecular polymers in the solid state. Such 1D polymers are linked, generating 2D layers, by combining additional MaBs and hydrogen bonds (HBs). Such concurrent motifs have been analyzed theoretically, suggesting the noncovalent σ‐hole nature of the MaBs. The interaction energies range from weak (~ −2 kcal/mol) for the MaBs to strong (~ −30 kcal/mol) for the MaB+HB assemblies, where HB dominates. In case of M=Zn, the corresponding perrhenate Zn(H2O)4(ReO4)2 complex, has been also synthesized for comparison purposes, resulting in the formation of an isostructural X‐ray structure, corroborating the structure‐directing role of Matere bonds.
Unveiling the structure of new pertechnetate derivatives: a journey through 1d and 2d supramolecular polymer formation dictated by matere bonds in combination with hydrogen bonds.
The number of crystal structures of pertechnetates derived from aqueous solutions has been expanded from seven to over 30. We report the conversion of NH4TcO4 to aqueous HtcO4 via acidic cation ...exchange. This is followed by the synthesis and structural elucidation of pertechnetate salts of alkaline earth (AE), transition metal I and lanthanoids (Ln) elements. Various degrees of hydration and coordination are discussed. Where possible, a comparison with the perrhenate homologues is made. The described syntheses and materials may be used as novel starting materials for extended technetium research.
The number of pertechnetate salts has been extended for a majority of the elements of the periodic table. A systematic crystallographic study of their coordination and level of hydration gives insight into periodic trends. The picture shows the M−Otc bond lengths of all known pertechnetates.
The Front Cover shows that there are occasions on which chemistry shows its human face. Thorium(IV) and uranium(IV), both of which share a love for chloride, saturate themselves quite literally when ...given the opportunity to take up some alcohol or water, i.e. polar‐protic solvents. When either ThCl4 or UCl4 is treated with methanol or ethanol, the molecular solvent adducts ThCl4(MeOH)4, UCl4(MeOH)4, ThCl4(EtOH)4 and UCl4(EtOH)4 form. The tendency to form the water adduct is so strong that, when a Th adduct is dissolved in hydrochloric acid, two Th−Cl bonds break up and ThCl2(H2O)7(Cl)2(H2O)2, which is isotypic with the already known UCl2(H2O)7(Cl)2(H2O)2, forms. At elevated temperature, the materials decompose to form their respective oxides. More information can be found in the Research Article by M. Zegke and co‐workers.
Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium ...pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH4)2TcO(OTf)5. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, TcO3(OTf), and intermediate TcVI species. 99Tc nuclear magnetic resonance (NMR) has been used to study the TcVII compound and electron paramagnetic resonance (EPR), 99Tc NMR and X‐ray absorption near‐edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH4)2TcO(OTf)5 slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH4)4{TcO(TcO4)4}4 ⋅10 H2O. Single‐crystal X‐ray crystallography was used to determine the solid‐state structures. Additionally, UV/Vis absorption and IR spectra as well as quantum chemical calculations confirm the identity of the species.
Ammonium pertechnetate is reduced to a green technetium(V) complex when left in triflic acid, while yellow pertechnetyl triflate and a purple TcVI species form as intermediates. In the presence of excess pertechnetate, the ammonium salt of a pertechnetato–oxotechnetate, can be isolated.
Thiosemicarbazone Complexes of Uranium(IV) Grödler, Dennis; Haseloer, Alexander; Tobeck, Christian ...
European journal of inorganic chemistry,
March 26, 2021, Letnik:
2021, Številka:
12
Journal Article
Recenzirano
Odprti dostop
The first homoleptic thiosemicarbazone complexes of uranium were isolated by reacting uranium tetrachloride in a salt metathesis or acid‐base reaction with four equivalents of Na(BzTSC) or H(BzTSC) ...(BzTSC=benzylthiosemicarbazone), carrying a non‐methylated (L1), monomethylated (L2) or dimethylated (L3) terminal amino group, in moderate yields. U(BzTSCNH2)4 (1), U(BzTSCNH(CH3))4 (2) and U(BzTSCN(CH3)2)4 (3) show a remarkable stability towards air, with oxidation potentials in THF between +0.43 and +0.53 V and reduction potentials between −2.53 and −2.67 V vs. ferrocene/ferrocenium. The simple methylation of the terminal amino group of the ligand allows for controlled changes in the coordination environments of the complexes. Thermogravimetric analyses indicate that the complexes are stable up to 155 °C.
Uranium changes color. Herein we present the first uranium(IV) thiosemicarbazone complexes. Their coordination is tunable depending on the N‐methylation of the ligand. This results in the inclusion and exclusion of THF solvent, leading to a change in color from yellow to red, but the spectroelectrochemical properties remain the same. The complexes are insensitive to oxidation or reduction within a potential range from +0.4 to −2.50 V in THF.
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