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Mo(super VI)(S2C6H4) reacts cleanly and completely with H(sub 2)O in THF to afford [H(sub 3)](super +)[Mo(super V)(S2C6H4)3](super -1). The Mo(super VI)(S2C6H4)3 reduction is acceralated by the presence of PPh3 and affords OPP3.

An investigation of the kinetics of the reaction of [Mo.sup.VI]{[S.sub.2][C.sub.6][H.sub.4]}[.sub.3] with organic phosphines to produce the anionic Mo(V) complex, [Mo.sup.VI]{[S.sub.2][C.sub.6][H.sub.4]}[.sub.3][.sup.-], and phosphine oxide is presented. Oxygen isotope tracing confirms that water rather than dioxygen is the source of the oxygen atom which is transferred to the phosphine, a reactivity which parallels oxidase activity of xanthine enzyme with phosphine as oxygen atom acceptor and [Mo.sup.VI]{[S.sub.2][C.sub.6][H.sub.4]}[.sub.3] as electron acceptor.

The 3D perception of the human eye is more impressive in irregular land surfaces than in flat land surfaces. The quantification of this perception would be very useful in many applications. This article presents the first approach to determining the visible volume, which we call the 3D-viewshed, in each and all the points of a DEM (Digital Elevation Model). Most previous visibility algorithms in GIS (Geographic Information Systems) are based on the concept of a 2D-viewshed, which determines the number of points that can be seen from an observer in a DEM. Extending such a 2D-viewshed to 3D space, then to all the DEM-points, is too expensive computationally since the viewshed computation per se is costly. In this work, we propose the first approach to compute a new visibility metric that quantifies the visible volume from every point of a DEM. In particular, we developed an efficient algorithm with a high data and calculation re-utilization. This article presents the first total-3D-viewshed maps together with validation results and comparative analysis. Using our highly scalable parallel algorithm to compute the total-3D-viewshed of a DEM with 4 million points on a Xeon Processor E5-2698 takes only 1.3 minutes. [ABSTRACT FROM AUTHOR]

This paper presents an efficient and highly scalable algorithm, designed from scratch, to calculate total-viewshed in large high-resolution digital elevation models (DEMs) without restrictions as to whether or not the observer is linked to the ground. The keys to the high efficiency of the proposed method are: 1) the selection of a reliable sampling to represent the subareas of study; 2) the use of a compact and stable data structure to store the calculated data; and 3) the high reutilization of data and calculation between the large number of viewpoints. The obtained results demonstrate that the proposed algorithm is the fastest over the most commonly used GIS-software showing very similar numerical accuracy. [ABSTRACT FROM PUBLISHER]

The kinetics of the reaction of neutral [Mo(S2C6H4)3] with hydrogen sulfite to produce the anionic Mo(V) complex, [Mo(S2C6H4)3]-, and sulfate have been investigated. It has been shown that [Mo(S2C6H4)3] acts as the electron—proton sink in the oxygenation reaction of HSO3- by water. Reaction rates, monitored by UV/vis stopped-flow spectrometry, were studied in THF/water media as a function of the concentration of HSO3- and molybdenum complex, pH, ionic strength, and temperature. The reaction exhibits pH-dependent HSO3- saturaiton kinetics, and it is first-order in complex concentration. The kinetic data and MS-ESI spectra are consistent with the formation of [Mo O(S2C6H4)2(S2C6H5)]- (1) adduct as a crucial intermediate that transfers the oxygen atom to HSO3- yielding the Mo(V) species quantitatively. [ABSTRACT FROM AUTHOR]

The kinetics of the reaction of MoVI(S2C6H4)3 with organic phosphines to produce the anionic Mo(V) complex, MoV(S2C6H4)3, and phosphine oxide have been investigated. Reaction rates, monitored by UV-vis stopped-flow spectrophotometry, were studied in THF/H2O media as a function of the concentration of phosphine, molybdenum complex, pH, and water concentration. The reaction exhibits pH-dependent phosphine saturation kinetics and is first-order in complex concentration. The water concentration strongly enhances the reaction rate, which is consistent with the formation of MoVI(S2C6H4)3(H2O) adduct as a crucial intermediate. The observed pH dependence of the reaction rate would arise from the distribution between acid and basic forms of this adduct. Apparently, the electrophilic attack by the phosphine at the oxygen requires the coordinated water to be in the unprotonated hydroxide form, MoVI(S2C6H4)3(HO)-. This is followed by the concerted abstraction of 2e-, H+ by the Mo(Vl) center to give MoVI(S2C6H4)32-, H+, and the corresponding phosphine oxide. However, this Mo(IV) complex product is oxidized rapidly to MoV(S2C6H4)3 via comproportionation with unreacted MoVI(S2C6H4)3. The Mo(V) complex thus formed can be oxidized to the starting Mo(Vl) complex upon admission of O2. Consequently, MoVI(S2C6H4)3 is a catalyst for the autoxidation of phosphines in the presence of water. Additionally, there was a detectable variation in the reactivity for a series of tertiary phosphines. The rate of Mo(Vl) complex reduction increases as does the phosphine basicity: (p-CH3C6H4)3P > (C6H5)3P > (p-CIC6H4)3P. Oxygen isotope tracing confirms that water rather than dioxygen is the source of the oxygen atom which is transferred to the phosphine. Such reactivity parallels oxidase activity of xanthine enzyme with phosphine as oxygen atom acceptor and MoVI(S2C6H4)3 as electron acceptor. [ABSTRACT FROM AUTHOR]

Examines the correlation between trigonal-prismatic (TP) and octahedral coordination in tris(1,2-benzenedithiolate) complexes. Role of molybdenum (Mo) in stabilizing TP tris(dithiolene) complexes; Characteristics of Mo; Determination of the terabutylammonium salts of anionic Mo.

MoVI (S2C6H4)3 reacts cleanly and completely with H2O in THF to afford [H3O] + [MoV (S2C6H4)3]-. Kinetic data were fit by the rate equation —d[MoVI (S2C6H4)3]/dt = κ[MoVI (S2C6H4)3]/[H3O+], which is consistent with a coupled electron—proton transfer mechanism involving a coordinated H2O molecule. The MoVI (S2C6H4)3 reduction is accelerated by the presence of PPh3 and affords OPPh3. 18O isotope tracing shows that H2O is the source of oxygen transferred to PPh3. [ABSTRACT FROM AUTHOR]

Discusses reduction of nitrobenzene to aniline catalyzed by a molybdenum-mediated oxygen atom transfer reaction. Features of enzyme behavior.

Describes the chemical properties of the molybdenum-based catalyst, MoVIO2-2,2-diphenyl-2-mercaptoethanoate ligand within a layered double hydroxide (LDH) system. Promise as a material of direct application to the elimination of contaminant thiols under ambient conditions.

The kinetic study of the spontaneous reduction of some neutral tris-dithiolene complexes [ML3] of molybdenum(VI) and tungsten(VI), (L = S2C6H4(2-), S2C6H3CH3(2-) and S2C2(CH3)2(2-); M = Mo or W) by tetrabutylammonium hydroxide in tetrahydrofuran-water solutions demonstrates that OH- is an effective reductant. Their reduction is fast, clean and quantitative. Depending upon both the molar ratio in which the reagents are mixed and the amount of water present, one- or two-electron reductions of these tris-dithiolene complexes were observed. If Bu4NOH is present in low concentration or/and at high concentrations of water, the total transformation of the neutral M(VI) complex into the monoanionic M(V) complex is the only observed process. Stopped-flow kinetic data for this reaction are consistent with the rate law: -d[ML3]/dt = d[ML3-]/dt = k[ML3][Bu4NOH]. The proposed mechanism involves nucleophilic attack of OH- to form a mono-anionic seven-coordinate intermediate [ML3OH]-, which interacts with another molecule of [ML3] to generate the monoanionic complex [ML3]- transfering the oxygen from coordinated OH- to water. Hydrogen peroxide was identified as the reaction product. The molybdenum complexes are more difficult to reduce than their corresponding tungsten complexes, and the values of k obtained for the molybdenum and tungsten series of complexes increase as the ene-1,2-dithiolate ligand becomes more electron-withdrawing (S2C6H4(2-) > S2C6H3CH3(2-) > S2C2(CH3)2(2-)). This investigation constitutes the only well-established interaction between hydroxide ion and a tris(dithiolene) complex, and supports a highly covalent bonding interaction between the metal and the hydroxide ion that modulates electron transfer reactions within these complexes.