Speciation and Thermodynamics of Sulfur Vapor

Wong

2005

Chemistry A European J

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Complex formation between gaseous Li+ ions and sulfur-containing neutral ligands, such as H2S, Me2Sn (n = 1-5; Me = CH3) and various isomers of hexasulfur (S6), has been studied by ab initio MO calculations at the G3X(MP2) level of theory. Generally, the formation of LiS(n) heterocycles and clusters is preferred in these reactions. The binding energies of the cation in the 29 complexes investigated range from -88 kJ mol(-1) for [H2SLi]+ to -189 kJ mol(-1) for the most stable isomer of [Me2S5Li]+ which contains three-coordinate Li+. Of the various S6 ligands (chair, boat, prism, branched ring, and triplet chain structures), two isomeric complexes containing the S5==S ligand have the highest binding energies (-163+/-1 kJ mol(-1)). However, the global minimum structure of [LiS6]+ is of C(3v) symmetry with the six-membered S(6) homocycle in the well-known chair conformation and three Li--S bonds with a length of 256 pm (binding energy: -134 kJ mol(-1)). Relatively unstable isomers of S6 are stabilized by complex formation with Li+. The interaction between the cation and the S6 ligands is mainly attributed to ion-dipole attraction with a little charge transfer, except in cations containing the six sulfur atoms in the form of separated neutral S2, S3, or S4 units, as in [Li(S3)2]+ and [Li(S2)(S4)]+. In the two most stable isomers of the [LiS6]+ complexes, the number of S--S bonds is at maximum and the coordination number of Li+ is either 3 or 4. A topological analysis of all investigated complexes revealed that the Li--S bonds of lengths below 280 pm are characterized by a maximum electron-density path and closed-shell interaction.

mentioning

confidence: 99%

Electrophilic Attack on Sulfur–Sulfur Bonds: Coordination of Lithium Cations to Sulfur‐Rich Molecules Studied by Ab Initio MO Methods

Wong

2005

Chemistry A European J

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“…More than 30 crystalline allotropes have been prepared and characterized by X-ray diffraction, most of which are composed of homocyclic rings. 48 In the small allotropes, the structures of S 2 (D¨h), 48 S 3 (open C 2v ), 48 and S 5 (ring C s ) 20,49 are known, but that of S 4 has been not identified for many years. Recent theoretical study, however, is leading to clarification of the structure: S 4 has planar C 2v structure in the ground state and rectangular D 2h structure is in a low lying transition state as mentioned before.…”

Section: ç Conclusion and Outlookmentioning

confidence: 99%

Chemistry of Tetrasulfur Including Mysterious Rectangular S4 Metal Complexes

Isobe¹

2011

Chemistry Letters

Of eleven possible isomers for neutral S 4 , rectangular S 4 has been proposed theoretically as one of the most stable forms. There has, however, been no consensus as to the S 4 ground-state geometric structure despite much effort over recent years, because of the lack of direct structural information from experimental work due to lack of preparation in a pure state. The principal question is whether the ground-state geometry is rectangular D 2h or open planar C 2v . Our group found first rectangular S 4 in coordination compounds of Rh and Ir tetranuclear complexes as a ligand and disclosed mysterious rectangular S 4 by X-ray analysis and theoretical studies. Here, the newly developed chemistry of rectangular S 4 complexes together with the related tetrasulfur species is introduced both from experimental and theoretical view points. In addition, more accurate argument of the principal question mentioned above is also described using results obtained from recent high-level theoretical calculations.

“…The highly reactive molecule S 3 is a component of hightemperature sulfur vapors, [18] although S 3 has been isolated in inert matrices at low temperatures and characterized by vibrational and UV/Vis spectroscopy. [19] The structure of S 3 has been determined by microwave spectroscopy.…”

Section: Adducts Of Smentioning

confidence: 99%

Charge‐Transfer Complexes between the Sulfur Molecules SO₂, S₂O, S₃, SONH, and SOCl₂ and the Amine Donors NH₃ and NMe₃ – A Theoretical Study

2007

Eur J Inorg Chem

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The formation of adducts between the acceptor molecules SO2, S2O, S3, and SOCl2 and the donor molecules ammonia and trimethylamine has been studied by high‐level G3X(MP2) theory, in most cases for the first time. Minimum energy structures with a 1:1 composition and with sulfur–nitrogen bonds have been located for all complexes. The thermodynamic properties, vibrational spectra, and atomic charges of these molecules have been calculated. Of the 10 investigated complexes, only SO2·NMe3 (2) and S2O·NMe3 (4) are predicted to be thermodynamically stable in the gas phase under standard conditions (ΔG°298 < 0). However, all adducts except S3·NH3 (5), SOCl2·NH3 (7), and SOCl2·NMe3 (8) are stable thermodynamically at 77 K. In a polar continuum with a dielectric constant (ϵ) of 40, complexes 2, 4, and S3·NMe3 (6) are stable even at 25 °C. However, if the adducts are formed in the polar continuum from the gaseous components, all adducts except S3·NH3 are formed not only exothermally but also exergonically. Complexes 2, 4, and 8 are the only species known in the solid state so far. The charge transfer from donor to acceptor in the various complexes in the gas phase ranges from 0.08 to 0.39 electrostatic units and correlates inversely with the S–N bond length, which ranges from 198 to 295 pm. In general, the charge transfer weakens the bonds within the acceptor molecule, which therefore may be considered to become activated. The formation of thionyl imide (SONH) from SOCl2 and NH3 is exergonic in the gas phase and the interaction between SONH and NH3 is very weak. In the case of SO2, the 1:2 complexes SO2·2NH3 (1a) and SO2·2NMe3 (2a), which contain two S–N bonds, are unstable with respect to their three‐component molecules both in the gas phase and in a polar medium at 25 °C, but they are stable in the polar phase with respect to the gaseous components.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)