Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Chemistry ; 2020 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-32897578

RESUMO

A photochemical route to salts consisting of difluorooxychloronium(V) cations, [ClOF2]+, and hexafluorido(non)metallate(V) anions, [MF6]- (M = V, Nb, Ta, Ru, Os, Ir, P, Sb) is presented. As starting materials, either metals, oxygen and ClF3 or oxides and ClF3 are used. The prepared compounds were characterized by single-crystal X-ray diffraction and Raman spectroscopy. The crystal structures of [ClOF2][MF6] (M = V, Ru, Os, Ir, P, Sb) are layer structures that are isotypic with the previously reported compound [ClOF2][AsF6], whereas for M = Nb and Ta, similar crystal structures with a different stacking variant of the layers are observed. Additionally, partial or full O/F disorder within the [ClOF2]+ cations of the Nb and Ta compounds occurs. In all compounds reported here, a trigonal pyramidal [ClOF2]+ cation with three additional Cl∙∙∙F contacts to neighboring [MF6]- anions is observed, resulting in an pseudo-octahedral coordination sphere around the Cl atom. The Cl-F and Cl-O bond lengths of the [ClOF2]+ cations seem to correlate with the effective ionic radii of the M(V) ions. Quantum-chemical, solid-state calculations well reproduce the experimental Raman spectra and show, as do quantum-chemical gas phase calculations, that the secondary Cl∙∙∙F interactions are ionic in nature. However, both solid-state and gas-phase quantum-chemical calculations fail to reproduce the increases in the Cl-O bond lengths with increasing effective ionic radius of M in [MF6]- and the Cl-O Raman shifts also do not generally follow this trend.

2.
Angew Chem Int Ed Engl ; 59(41): 18116-18119, 2020 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-32608053

RESUMO

Reaction of CsF with ClF3 leads to Cs[Cl3 F10 ]. It contains a molecular, propeller-shaped [Cl3 F10 ]- anion with a central µ3 -F atom and three T-shaped ClF3 molecules coordinated to it. This anion represents the first example of a heteropolyhalide anion of higher ClF3 content than [ClF4 ]- and is the first Cl-containing interhalogen species with a µ-bridging F atom. The chemical bonds to the central µ3 -F atom are highly ionic and quite weak as the bond lengths within the coordinating XF3 units (X = Cl, and also calculated for Br, I) are almost unchanged in comparison to free XF3 molecules. Cs[Cl3 F10 ] crystallizes in a very rarely observed A[5] B[5] structure type, where cations and anions are each pseudohexagonally close packed, and reside, each with coordination number five, in the trigonal bipyramidal voids of the other.

3.
Chemistry ; 25(30): 7366-7374, 2019 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-30912599

RESUMO

A laboratory-scale synthesis of UF4 is presented that utilizes the reduction of UF6 with sulfur in anhydrous hydrogen fluoride. An excess of sulfur can be removed by vacuum sublimation, yielding pure UF4 , as shown by powder X-ray diffraction, micro X-ray fluorescence analysis, infrared and Raman spectroscopy, as well as magnetic measurements. Furthermore, a single-crystalline, high-pressure modification of UF4 was obtained in a multi-anvil press at elevated temperatures. The high-pressure polymorph HP-UF4 was characterized by means of single-crystal and powder X-ray diffraction, as well as by magnetic measurements, and presents a novel crystal structure type. Quantum-chemical calculations show the HP-modification to be 10 kJ mol-1 per formula unit higher in energy compared to UF4 .

4.
Phys Rev Lett ; 120(9): 093001, 2018 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-29547322

RESUMO

A recent measurement of the hyperfine splitting in the ground state of Li-like ^{208}Bi^{80+} has established a "hyperfine puzzle"-the experimental result exhibits a 7σ deviation from the theoretical prediction [J. Ullmann et al., Nat. Commun. 8, 15484 (2017)NCAOBW2041-172310.1038/ncomms15484; J. P. Karr, Nat. Phys. 13, 533 (2017)NPAHAX1745-247310.1038/nphys4159]. We provide evidence that the discrepancy is caused by an inaccurate value of the tabulated nuclear magnetic moment (µ_{I}) of ^{209}Bi. We perform relativistic density functional theory and relativistic coupled cluster calculations of the shielding constant that should be used to extract the value of µ_{I}(^{209}Bi) and combine it with nuclear magnetic resonance measurements of Bi(NO_{3})_{3} in nitric acid solutions and of the hexafluoridobismuthate(V) BiF_{6}^{-} ion in acetonitrile. The result clearly reveals that µ_{I}(^{209}Bi) is much smaller than the tabulated value used previously. Applying the new magnetic moment shifts the theoretical prediction into agreement with experiment and resolves the hyperfine puzzle.

5.
Angew Chem Int Ed Engl ; 57(11): 2914-2918, 2018 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-29363236

RESUMO

The D2h -symmetric dinuclear complex anion [U2 F12 ]2- of pastel green Sr[U2 F12 ] shows a hitherto unknown structural feature: The coordination polyhedra around the U atoms are edge-linked monocapped trigonal prisms, the UV atoms are therefore seven-coordinated. This leads to a U-U distance of 3.8913(6) Å. A weak UV -UV interaction is observed for the dinuclear [U2 F12 ]2- complex and described by the antiferromagnetic exchange Jexp of circa -29.9 cm-1 . The crystalline compound can be easily prepared from SrF2 and ß-UF5 in anhydrous hydrogen fluoride (aHF) at room temperature. It was studied by means of single crystal X-ray diffraction, IR, Raman and UV/VIS spectroscopy, magnetic measurements, and by molecular as well as by solid-state quantum chemical calculations.

6.
Chemistry ; 23(2): 291-295, 2017 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-27859894

RESUMO

ß-Uranium(V) fluoride was reacted with liquid anhydrous hydrogen cyanide to obtain a 1D coordination polymer with the composition 1∞ [UF5 (HCN)2 ], 1∞ [UF4/1 F2/2 - (HCN)2/1 ], revealed by single-crystal X-ray structure determination. The reaction system was furthermore studied by means of vibrational and NMR spectroscopy, as well as by quantum chemical calculations. The compound presents the first described polymeric HCN Lewis adduct and the first HCN adduct of a uranium fluoride.

7.
Chemistry ; 22(34): 12145-53, 2016 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-27416109

RESUMO

We have synthesized NOUF6 by direct reaction of NO with UF6 in anhydrous HF (aHF). Based on the unit cell volume and powder diffraction data, the compound was previously reported to be isotypic to O2 PtF6 , however, detailed structural data, such as the atom positions and all information that can be derived from those, were unavailable. We have therefore investigated the compound by using single-crystal and powder X-ray diffraction, IR, Raman, NMR, EPR, and photoluminescence spectroscopy, magnetic measurements, as well as chemical analysis, density determination, and quantum chemical calculations.

8.
Inorg Chem ; 54(19): 9568-75, 2015 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-26371537

RESUMO

A high-yield synthesis of the class of (trimethylsilyl)chalcogenolate organic salts [Cat][TMS-E] (E = S, Se, Te; Cat = BMPyr, DMPyr, NMe4, nBu3MeP) is presented. The title compounds have been prepared by the strictly aprotic reaction between the respective bis(trimethylsilyl)chalcogenide (TMS2E) and methylcarbonate ionic liquids (ILs). This constitutes a novel reaction behavior of methylcarbonate ILs, acting as a nucleophilic desilylating agent and a Lewis base instead of as a Brønsted base. Thus prepared silylchalcogenolate salts represent an activated form of the multifunctional TMS2E reactant series. Pyrrolidinium TMS-S salts have proven to be excellent precursors for the synthesis of pyrrolidinium hexasulfides. The scope of the desilylation reaction can be extended to other silyl-bearing synthons such as (trimethylsilyl)azide and (trimethylsilyl)cyanide.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...