Computational studies have led to models to understand some classic and contemporary asymmetric reactions involving organocatalysts. The Hajos−Parrish−Eder−Sauer−Wiechert reaction and intermolecular aldol reactions as well as Mannich reactions and oxyaminations catalyzed by proline and other amino acids, and Diels−Alder reactions catalyzed by MacMillan's chiral amine organocatalysts have been studied with density functional theory. Quantitative predictions for several new catalysts and reactions are provided.

Theory of asymmetric organocatalysis of Aldol and related reactions: rationalizations and predictions.

Molecular inorganic clusters, which are stable under ambient conditions, can be used as convenient single-source precursors for controlled preparation of 2−9-nm CdSe and CdSe/ZnS nanocrystals and 2−5-nm nanocrystals of ZnSe. The use of a cluster-based single-source precursor allows nanomaterial growth to be initiated at low temperature without the pyrolytic step for nucleus formation traditionally required for lyothermal growth processes. The elimination of the pyrolytic step allows greater synthetic control, slow thermodynamic growth at lower temperatures, high crystallinity, and reaction scalability (>50 g/L) while maintaining size dispersity at ∼5%.

Inorganic Clusters as Single-Source Precursors for Preparation of CdSe, ZnSe, and CdSe/ZnS Nanomaterials

Rhenium disulfide (ReS2) is a two-dimensional (2D) group VII transition metal dichalcogenide (TMD). It is attributed with structural and vibrational anisotropy, layer-independent electrical and optical properties, and metal-free magnetism properties. These properties are unusual compared with more widely used group VI-TMDs, e.g., MoS2, MoSe2, WS2 and WSe2. Consequently, it has attracted significant interest in recent years and is now being used for a variety of applications including solid state electronics, catalysis, and, energy harvesting and energy storage. It is anticipated that ReS2 has the potential to be equally used in parallel with isotropic TMDs from group VI for all known applications and beyond. Therefore, a review on ReS2 is very timely. In this first review on ReS2, we critically analyze the available synthesis procedures and their pros/cons, atomic structure and lattice symmetry, crystal structure, and growth mechanisms with an insight into the orientation and architecture of domain and grain boundaries, decoupling of structural and vibrational properties, anisotropic electrical, optical, and magnetic properties impacted by crystal imperfections, doping and adatoms adsorptions, and contemporary applications in different areas.

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Advent of 2D Rhenium Disulfide (ReS2): Fundamentals to Applications

Capture of molybdenum in pyrite-forming sediments: role of ligand-induced reduction by polysulfides

Deep HDS of diesel fuel: chemistry and catalysis

Rhenium sulfides, e.g., ReS{sub 2} and Re{sub 2}S{sub 7}, have long been recognized for their hydrogenation and dehydrogenation reactivity. Periodic trends in catalytic hydrodesulfurization (HDS) reveal rhenium sulfur systems to have high activity. However, discrete, soluble rhenium sulfur species have not received as much attention as have group VI sulfide systems. The tetrathiometalate anions of V, Mo, and W (VS{sub 4}{sup 3{minus}}; MoS{sub 4}{sup 2{minus}}; WS{sub 4}{sup 2{minus}}), which possess fully oxidized (d{sup 0}) metal centers and fully reduced (S{sup 2{minus}}) sulfide ligands, undergo internal redox upon reacting with external oxidants. In these reactions bound sulfide ions (S{sup 2{minus}}) serve as the reductant forming disulfide (S{sub 2}{sup 2{minus}}) concomitant with reduction of the metal center. Conspicuously, ReS{sub 4}{sup {minus}} is the only soluble tetrathiometalate whose chemistry in this regard has not been explored. Here the authors report that tetraalkylthiuram disulfide, acting as an oxidant, induces a dramatic and unprecedented 3e{sup {minus}} reduction of the Re-(VII) center of ReS{sub 4}{sup {minus}}.

Induced internal electron transfer reactivity of tetrathioperrhenate(VII): synthesis of the interconvertible dimers Re2(.mu.-S)2(S2CNR2)4 and [Re2(.mu.-SS2CNR2)2(S2CNR2)3][O3SCF3] (R = Me, iso-Bu)

This paper demonstrates the proclivity with which high-valent rhenium sulfur complexes undergo internal electron transfer. Specifically, reaction of [Et{sub 4}N][ReS{sub 4}] with 1.5 molar equiv of tetraalkylthiuram disulfide in acetonitrile gives the dinuclear Re(IV) complexes, Re{sub 2}({mu}-S){sub 2}(S{sub 2}CNR{sub 2}), 1, in very high yield. This dimer reacts with an additional equivalent of tetraalkylthiuram disulfide in the presence of excess Lewis acids, or with 0.5 molar equiv of tetraalkylthiuram disulfide and 1 molar equiv of [Cp{sub 2}Fe][PF{sub 6}], to give the dinuclear Re(III) species [Re{sub 2}({mu}-S-S{sub 2}CNR{sub 2}){sub 2}(S{sub 2}CNR{sub 2}){sub 3}]{sup +}, 2, in high yield. The reaction of [ReS{sub 4}]{sup {minus}} with 3 molar equiv of tetraalkylthiuram disulfide in a mixture of dichloromethane and acetonitrile gives the mononuclear Re(V) species [Re(S{sub 2}CN(R){sub 2}){sub 4}]-[Cl], 3, in high yield. Each of these reactions involves induced internal electron transfer in which the formal oxidation state of the metal center is reduced by the addition of an oxidant (i.e., tetraalkylthiuram disulfide). The bound sulfide is the reductant both for the metal and the external oxidant. The reformation of 1 from 2, in which the metal is oxidized, can be effected using reductants such as H{sub 2}. Electrochemical properties and chemical reactivitiesmore » of the complexes are presented.« less

Induced internal electron transfer chemistry in rhenium sulfide systems

Molecules, clusters, solids and catalysts in early transition metal sulphide systems

Bridging Disulfido Complexes of Molybdenum and Tungsten Formed by Reductive Sulfurization of Oxo-Molybdenum(VI) Complexes and Reductive Desulfurization of Thio(disulfido)-Tungsten(VI) Complexes

A method for preparing molybdenum and sulfur containing compounds of the general formula X 2 Mo 2 S 12 .yH 2 O, where X is a cation selected from the group consisting of Na + , K + , R 4 N + , R 3 NH + , R 2 NH 2 + , RNH 3 + , NH 4 + , R 4 P + , R 4 As + ,(R 3 P) 2 N + , R is a C 1 -C 30 alkyl, C 6 -C 30 aryl, C 7 -C 30 aralkyl or C 2 -C 30 alkoxyalkyl group and mixtures thereof, and y is from 0 to 2. The method comprises preparing a sulfide solution that contains from about 9 wt. % to about 13 wt. % sulfide sulfur; contacting the solution with elemental sulfur and a hydroxide; adding a molybdenum compound for a time and at a temperature sufficient to form a reaction mixture and a precipitate; separating the precipitate; and contacting the remaining reaction mixture with additional sulfide solution to form (NH 4 ) 2 Mo 2 S 12 .yH 2 O. When compounds containing cations other than NH 4 + are to be produced, the (NH 4 ) 2 Mo 2 S 12 .yH 2 O is contacted with a cation exchange compound containing a desired substitute cation selected from above and an anion selected from the group consisting of Cl - , Br - , F - , I - , BF 4 - , PF 6 - , OH - , BR 4 - where R is a C 1 -C 30 alkyl, C 6 -C 30 aryl, C 7 -C 30 aralkyl or C 2 -C 30 alkoxyalkyl group, and mixtures thereof, in the presence of a solvent and for a time and at a temperature sufficient to form X 2 Mo 2 S 12 .yH 2 O, where X is other than NH 4 + .

Liwen Wei

Papers

Induced internal electron transfer reactivity of tetrathioperrhenate(VII): synthesis of the interconvertible dimers Re2(.mu.-S)2(S2CNR2)4 and [Re2(.mu.-SS2CNR2)2(S2CNR2)3][O3SCF3] (R = Me, iso-Bu)

Induced internal electron transfer chemistry in rhenium sulfide systems

Molecules, clusters, solids and catalysts in early transition metal sulphide systems

Bridging Disulfido Complexes of Molybdenum and Tungsten Formed by Reductive Sulfurization of Oxo-Molybdenum(VI) Complexes and Reductive Desulfurization of Thio(disulfido)-Tungsten(VI) Complexes

Method for making molybdenum and sulfur containing compounds