Dimerisation of alpha-olefins by a catalyst system comprising of a bis(imido) tungsten compound and a Lewis acid component has been investigated by density functional theory employing a catalyst model that closely mimics the real system together with ethylene chosen as a prototypical substrate. This study disclosed that the Lewis acid preferably forms four-membered chelates by bridging across t...

This short review article covers some useful applications of alkynyltungsten compounds to the syntheses of complex lactones. Two types of cyclizations will be emphasized: (1) cycloalkenylation of tungsten-alkynol compounds with aldehydes to give α-alkylidene oxacarbeniums, further leading to α-alkylidene lactones and (2) intramolecular [3+2]-cycloaddition of epoxides to give bicyclic lactones. ...

two new heterogenized epoxidation nanocatalysts based on molybdenum and tungsten compounds were prepared withcovalent grafting of mcm-41 with 3-aminoropropyl trimethoxysilane and subsequent reaction with diphenylphosphinobenzaldehyde and complexation with m (mo, w)o2(acac)2. x-ray diffraction and nitrogen sorption analyses revealed the preservation of the textural properties of the support as w...

Chapter 1 Reaction of W(CCMe 3)Cl 3(dme) with one equivalent of (3,5-Me 2C6H3NCH 2CH 2)3N)Li3 affords yellow, crystalline W(CCMe 3)(N3N) in good yield. The reactivity of this new alkylidyne complex towards terminal alkynes was investigated. Two other new tungsten alkylidynes, W(CCMe 3)(pyr) 3 (pyr = 2,5-dimethylpyrrolide) and W(CCMe3)(Ph 2N)3 were prepared by the addition of three equivalents o...

This reaction allows for new olefins to be synthesized and used as raw materials in polymers, perfumes, drugs and agrochemical industrial products, also serving as the starting point for more complex organic molecules. Catalytic systems are based mainly on the metals W, Mo, Re and Ru. The metal-alkylidenes synthesized by Schrock, [Mo(CHR)(NAr)(OR f ) 2 ], Grubbs, [Ru(CHR)(PCy 3 ) 2 Cl 2 ], Herr...

Hydrogenation of unsaturated organosulfur compounds is an essential process through which these species are converted into cleaner and more useful compounds. Hydrogen bronze materials have been demonstrated to be efficient catalysts in hydrogenation of simple unsaturated compounds. Herein, we performed density functional theory calculations to investigate hydrogenation of thiophene on hydrogen ...

The increasing use of tungsten in the production green energy aerospace and military industries, many other hi-tech applications, may increase content this element soil. This overview examines some aspects behavior soil, such as importance characteristics soils relation to bioavailability processes, chemical approaches evaluate mobility soil environment adsorption desorption processes. Tungsten...

The meso-tetrakis (4-N, N, N-trimethylanilinium) porphyrin and its zinc compound deposited on glass slide at high temperature and at a pressure of 15 PSI were used as photo-inactivation surface. Also, the effect of two porphyrin compounds irradiated with tungsten lamp, on a Gram negative bacterium, Pseudomonas aeruginosa, and a Gram positive bacterium, Bacillus subtilis was investigated.