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SS Bond (ss + bond)

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Chemistry100%

Selected Abstracts

ChemInform Abstract: Characterization of the Weak SS Bonds in the OSSSO and O2SSSO2 Molecules

CHEMINFORM, Issue 39 2009
D. B. Chestnut
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Reactions of Chlorosulfanyl Derivatives of Cyclobutanones with Different Nucleophiles

HELVETICA CHIMICA ACTA, Issue 5 2006
Agnieszka Majchrzak
Abstract The reactions of 3-chloro-3-(chlorosulfanyl)-2,2,4,4-tetramethylcyclobutan-1-one (2) with N, O, S, and P nucleophiles occur by substitution of Cl at the S-atom. Whereas, in the cases of secondary amines, alkanols, phenols, thiols, thiophenols, and di- and trialkyl phosphates, the initially formed substitution products were obtained, the corresponding products with allyl and propargyl alcohols undergo a [2,3]-sigmatropic rearrangement to give allyl and allenyl sulfoxides, respectively. Analogous substitution reactions were observed when 3-chloro-3-(chlorodisulfanyl)-2,2,4,4-tetramethylcyclobutan-1-one (3) was treated with N, O, and S nucleophiles. The reaction of 3 with Et3P led to an unexpected product via cleavage of the SS bond (cf. Scheme,13). In the reactions of 2 with primary amines and H2O, the substitution products react further via elimination of HCl to yield the corresponding thiocarbonyl S -imides and the thiocarbonyl S -oxide, respectively. Whereas the latter could be isolated, the former were not stable but could be intercepted by MeOH (Scheme,4) or adamantanethione (Scheme,5). The structures of some of the substitution products were established by X-ray crystallography. [source]

Antiferromagnetism or Delocalized Spin in a Cu3S2 Core?

CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2010
Santiago Alvarez
Is there a bond or isn,t there? In a further effort to bring light to the debate on the existence of an SS bond in Tolman,s cluster compound (shown here), this correspondence is a reply to the preceeding communication. [source]

Complexation of the Vulcanization Accelerator Tetramethylthiuram Disulfide and Related Molecules with Zinc Compounds Including Zinc Oxide Clusters (Zn4O4)

CHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2008
Ralf Steudel Prof.
Abstract Zinc chemicals are used as activators in the vulcanization of organic polymers with sulfur to produce elastic rubbers. In this work, the reactions of Zn2+, ZnMe2, Zn(OMe)2, Zn(OOCMe)2, and the heterocubane cluster Zn4O4 with the vulcanization accelerator tetramethylthiuram disulfide (TMTD) and with the related radicals and anions Me2NCS2., Me2NCS3., Me2NCS2,, and Me2NCS3, have been studied by quantum chemical methods at the MP2/6-31+G(2df,p)//B3LYP/6-31+G* level of theory. More than 35 zinc complexes have been structurally characterized and the energies of formation from their components calculated for the first time. The binding energy of TMTD as a bidendate ligand increases in the order ZnMe2SS bond on reaction with the Zn4O4 cluster is predicted to be strongly exothermic, in sharp contrast to the endothermic SS bond dissociation of the free molecule. The same holds for tetramethylthiuram trisulfide (TMTT). Surprisingly, the resulting complexes contain ZnS as well as SO bonds. The Zn4O4 nanocluster serves here as a model for bulk zinc oxide used as an activator in rubber vulcanization by sulfur. The further uptake of sulfur atoms by the various complexes from S8 or TMTD with formation of species derived from the radical Me2NCS3. or the trithiocarbamate anion Me2NCS3, is endothermic for mono- and dinuclear zinc dithiocarbamate (dtc) complexes such as [Zn(dtc)2] and [Zn2(dtc)4], but exothermic in the case of polynuclear zinc oxide species containing bridging ligands as in [Zn4O4(,-S2CNMe2)] and [Zn4O4(,-dtc)]. Therefore, zinc oxide as a polynuclear species is predicted to promote the formation of trisulfido complexes, which are generally assumed to serve as catalysts for the transfer of sulfur atoms during rubber vulcanization. This prediction is in accord with the empirical knowledge that ZnO is a better activator in TMTD-accelerated rubber vulcanization than zinc dithiocarbamate. [source]

Electron Transfer to Sulfides and Disulfides: Intrinsic Barriers and Relationship between Heterogeneous and Homogeneous Electron-Transfer Kinetics

CHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2007
Belèn Meneses
Abstract The electron-acceptor properties of series of related sulfides and disulfides were investigated in N,N -dimethylformamide with homogeneous (redox catalysis) and/or heterogeneous (cyclic voltammetry and convolution analysis) electrochemical techniques. The electron-transfer rate constants were determined as a function of the reaction free energy and the corresponding intrinsic barriers were determined. The dependence of relevant thermodynamic and kinetic parameters on substituents was assessed. The kinetic data were also analyzed in relation to corresponding data pertaining to reduction of diaryl disulfides. All investigated reductions take place by stepwise dissociative electron transfer (DET) which causes cleavage of the CalkylS or SS bond. A generalized picture of how the intrinsic electron-transfer barrier depends on molecular features, ring substituents, and the presence of spacers between the frangible bond and aromatic groups was established. The reduction mechanism was found to undergo a progressive (and now predictable) transition between common stepwise DET and DET proceeding through formation of loose radical anions. The intrinsic barriers were compared with available results for ET to several classes of dissociative- and nondissociative-type acceptors, and this led to verification that the heterogeneous and the homogeneous data correlate as predicted by the Hush theory. [source]

Fourier transform Raman spectroscopic study of pressure-induced ligand bond activation in a molybdenum,sulfur cluster,

JOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2002
Ian S. Butler
Fourier transform Raman spectra of the prototype, triangular, transition metal,sulfur cluster anion [Mo3(S2)6S]2, were recorded at pressures up to 60 kbar with the aid of a diamond-anvil cell (DAC). The pressure dependences (,,/,p) of the Raman bands indicate a structural change at around 10,15 kbar. The SS stretching mode for the bridging disulfide ligands exhibits a slightly negative ,,/,p value (,0.08), suggesting that SS bonds are weakened, i.e. activated, at high pressures. This pressure-induced activity parallels the observed nucleophilic substitution reactivity of the S2 groups in this molybdenum cluster anion. In view of this, a preliminary investigation of the reaction between [Mo3(S2)6S]2, and CN, was undertaken in the solid state in the DAC under high pressure. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Structures and Vibrational Spectra of the Sulfur-Rich Oxides SnO (n = 4,9): The Importance of ,*,,* Interactions

CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2007
Wah Wong Prof.
Abstract The structures of a large number of isomers of the sulfur oxides SnO with n = 4,9 have been calculated at the G3X(MP2) level of theory. In most cases, homocyclic molecules with exocyclic oxygen atoms in an axial position are the global minimum structures. Perfect agreement is obtained with experimentally determined structures of S7O and S8O. The most stable S4O isomer as well as some less stable isomers of S5O and S6O are characterized by a strong ,*,,* interaction between SO and SS groups, which results in relatively long SS bonds with internuclear distances of 244,262,pm. Heterocyclic isomers are less stable than the global minimum structures, and this energy difference approximately increases with the ring size: 17 (S4O), 40 (S5O), 32 (S6O), 28 (S7O), 45 (S8O), and 54,kJ,mol,1 (S9O). Owing to a favorable ,*,,* interaction, preference for an axial (or endo) conformation is calculated for the global energy minima of S7O, S8O, and S9O. Vapor-phase decomposition of SnO molecules to SO2 and S8 is strongly exothermic, whereas the formation of S2O and S8 is exothermic if n<7, but slightly endothermic for S7O, S8O, and S9O. The calculated vibrational spectra of the most stable isomers of S6O, S7O, and S8O are in excellent agreement with the observed data. [source]

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

CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2005
Yana Steudel Dr.
Abstract 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 LiSn 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 S5S ligand have the highest binding energies (,163±1 kJ,mol,1). However, the global minimum structure of [LiS6]+ is of C3v symmetry with the six-membered S6 homocycle in the well-known chair conformation and three LiS 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 SS 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 LiS bonds of lengths below 280 pm are characterized by a maximum electron-density path and closed-shell interaction. [source]