Homocyclic Selenium Molecules and Related Cations

Steudel, Ralf; Strauss, Eva‐Maria

doi:10.1016/s0898-8838(08)60207-x

Cited by 53 publications

(23 citation statements)

References 70 publications

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“…34 The Se 4 2+ ions are examples of six-π -electron systems, and they are thus examples of inorganic aromatic compounds (1b). Their π -bond order is 0.25; accordingly, the overall Se-Se bond length of 2.283Å in Se 4 (HS 2 O 7 ) 2 32 is significantly shorter than the Se-Se distance of 2.34Å in the Se 8 molecule. The intense yellow -orange color of the Se 4 2+ ion (λ max 410 nm, ε8000) is to be expected from the dipole-allowed excitation of an electron from the highest filled π -orbital which is of symmetry e g and almost nonbonding, to the lowest empty π -orbital (b 2u ).…”

Section: Se 4 2+ Cationmentioning

confidence: 94%

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Selenium: Inorganic ChemistryBased in part on the article Selenium: Inorganic Chemistry by Bernt Krebs, Stefan Bonmann, & Illenora Eidenschink which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Atwood

2005

Encyclopedia of Inorganic Chemistry

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Selenium is the first member of the group 16 elements O, S, Se, Te, and Po that shows some metallic character. The increasing metallic character in the series O, S, Se, Te, Po is reflected also in the lower electronegativity, in the less acid character of the oxides, and in the lower stability of the oxidation number +VI for selenium compared to sulfur. There is a large variety of compounds of SeII, SeIV, and SeVI with the electronegative elements N, O, F, Cl, and Br. Thus, there are six general types of compounds, and these will comprise the main sections in the article. They are cations, halides, oxides, haloselenates, oxohaloselenates, and the related compounds that form when both selenium and nitrogen are present in the molecule.

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Section: Se 4 2+ Cationmentioning

confidence: 94%

“…All are somewhat less stable than the corresponding sulfur compounds. The tendency to form double bonds is smaller in selenium than sulfur, although the existence of strong Se=O bonds in oxo -halo selenium compounds such as SeOCl 2 …”

Section: Introductionmentioning

confidence: 99%

Selenium: Inorganic ChemistryBased in part on the article Selenium: Inorganic Chemistry by Bernt Krebs, Stefan Bonmann, & Illenora Eidenschink which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Atwood

2005

Encyclopedia of Inorganic Chemistry

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“…However, storage of an oily reaction product for three months at ambient temperature yielded large yellow-orange cubes of 1 (X-ray structure). We were unable to prepare 1 directly from selenium and Ag[Sb(OTeF 5 ) 6 ], but always observed the formation of Se cations in SO 2 solution by 77 Se-NMR spectroscopy (Se 10 2+ , and upon cooling to -70…”

Section: -8 Hexagonal Tementioning

confidence: 99%

“…Previously, those were synthesized by reactions of strong oxidation agents, e.g. MF 5 (M = As, Sb) and S 2 O 6 F 2 , with the corresponding element or via solid state methods. However the experimental findings and an analysis of the energetics of the system showed that in the solid state the Ag-Se 6 complexes were favoured over the pure selenium cations.…”

Section: -77mentioning

confidence: 99%

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Metastable Se6 as a ligand for Ag+: from isolated molecular to polymeric 1D and 2D structures

et al. 2011

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• cations. Overall 1-4 are new members of the rare class of metal complexes of neutral main group elemental clusters, in which the main group element is positively polarized due to coordination to a metal ion. Notably, 1 to 4 include the commonly metastable Se 6 molecule as a ligand. The structure, bonding and thermodynamics of 1 to 4 were investigated with the help of quantum chemical calculations (PBE0/TZVPP and (RI-)MP2/TZVPP, in part including COSMO solvation) and Born-Fajans-Haber-cycle calculations. From an analysis of all the available data it appears that the formation of the usually metastable Se 6 molecule from grey selenium is thermodynamically driven by the coordination to the Ag + ions.

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Does the Interconversion of Polysulfur Compounds Proceed Via Hypervalent Intermediates?—An Ab Initio MO Study

Steudel

Mia̧skiewicz

2001

Chem. Eur. J.

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Ab initio MO calculations at the CCSD(T)/6-311++G(2df,p)//MP2/6-311++G** level have been carried out to determine the reaction energies and Gibbs energies of the homolytic dissociation of the S-S bonds in the chainlike sulfanes H2Sn (n = 2-4). Good agreement with the experimental data is observed. At the same level of theory, the formation of the hypothetical sulfuranes H2S(SH)2, H2S(SSH)2, and S(SH)4 from H2S and the mentioned sulfanes has been studied. Species of this type had been proposed as intermediates in the interconversion reactions of polysulfur compounds (e.g., formation of S7 from S8 and vice versa). The three sulfuranes serve here as model compounds. On the basis of the Gibbs energies and activation energies at 298 K, it is shown that the formation of the three sulfuranes from sulfanes requires too much energy and activation energy to successfully compete with homolytic dissociation reactions. In addition, the formation of the methylsubstituted sulfurane S(SMe)4 from the sulfanes Me2S2 and Me2S3 was studied to elucidate the mechanism of the formal exchange of sulfur atoms between polysulfane molecules. However, both the reaction energy of 199 kJ mol(-1) and the activation energy of 287 kJ mol(-1), calculated at the MP2/6-31G* level, are much higher than the homolytic dissociation energy of the S-S bonds in chain- and ringlike polysulfur compounds, such as Me2S4 (140 kJ mol(-1)) and sulfur homocycles (150 kJ mol(-1)). Therefore, it is concluded that the observed interconversion reactions of sulfur rings and of chainlike polysulfanes do not proceed via sulfurane-type intermediates. Instead, these reactions will take place by a radical chain mechanism at high temperatures, while at temperatures below 100 degrees C they are most probably initiated either by traces of nucleophiles that are present as impurities or by the polar surface groups usually present on the walls of the vessels used.

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Homocyclic Selenium Molecules and Related Cations

Cited by 53 publications

References 70 publications

Selenium: Inorganic ChemistryBased in part on the article Selenium: Inorganic Chemistry by Bernt Krebs, Stefan Bonmann, & Illenora Eidenschink which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Selenium: Inorganic ChemistryBased in part on the article Selenium: Inorganic Chemistry by Bernt Krebs, Stefan Bonmann, & Illenora Eidenschink which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Metastable Se6 as a ligand for Ag+: from isolated molecular to polymeric 1D and 2D structures

Does the Interconversion of Polysulfur Compounds Proceed Via Hypervalent Intermediates?—An Ab Initio MO Study

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