Titanium chalcogenides

Very little is known about chalcogenide halides of Group IVB elements. Although the existence of sulfide chlorides (45, 274, 329, 365) and of a selenide chloride (329) of titanium was claimed in early publications, their true composition, and even their existence, remains doubtful. They have usually been obtained by the reaction of titanium chlorides with sulfur and selenium, respectively, or with hydrogen sulfide. The synthesis of a pure compound, TiSClj, was published in 1959 (113). It is an intermediate of the reaction of TiCU with HjS. 

Somasundaram S, Chenthamarakshan CR, Tacconi NR, Ming Y, Rajeshwar K (2004) Photoassisted deposition of chalcogenide semiconductors on the titanium dioxide surface Mechanistic and other aspects. Chem Mater 16 3846-3852... 

In considering photoactivity on metal oxide and metal chalcogenide semiconductor surfaces, we must be aware that multiple sites for adsorption are accessible. On titanium dioxide, for example, there exist acidic, basic, and surface defect sites for adsorption. Adsorption isotherms will differ at each site, so that selective activation on a particular material may indeed depend on photocatalyst preparation, since this may in turn Influence the relative fraction of each type of adsorption site. The number of basic sites can be determined by titration but the total number of acidic sites is difficult to establish because of competitive water adsorption. A rough ratio of acidic to basic binding sites on several commercially available titania samples has been shown by combined surface ir and chemical titration methods to be about 2.4, with a combined acid/base site concentration of about 0.5 mmol/g . 

Chalcogenides. The crystal structures of titanium sulphides have been reviewed.41 Ti3S8 has several structural features in common with TiS2 including trigonal-prismatic co-ordination polyhedra about S atoms and cubic co-ordination polyhedra about Ti atoms. Whereas six cube faces are shared with trigonal prisms in TiS2 only,... 

The overwhelming majority of colloidal semiconductors studied to date are metal oxides and chalcogenides with the greatest interest being shown in the chemically durable titanium dioxide. In turn, most of the research... 

Shi, M., Jiang, J. K. Amendment in Titanium(IV) Chloride and Chalcogenide-Promoted Bayiis-Hiiiman Reaction of Aldehydes with a, 3-Unsaturated Ketones. Tetrahedron 2000, 56,4793-4797. 

Attempts to synthesize Gp titanium complexes with a terminal Ti=Te moiety have met with difficulties. One of the principal factors for this is the particularly weak Ti=Te interaction. Ti=E bond energies for Cp2Ti=0 (152.6 kj mol 1) and Cp2Ti=Te (130.3 kj mol-1) have been calculated. The hydrido titanium(m) complex Gp 2TiH reacts with elemental selenium or tellurium to give mono- and diselenido and tellurido complexes. The possible involvement of monomeric terminal chalcogenides Cp 2Ti(E) (E = O, S, Se, Te) in these reactions has been probed experimentally and computationally by means of DFT calculations. 

With this respect, the work from Atanasoski and coworkers is promising (compare section Transition Metal Carbides, Nitrides and Chalcogenides ) [35], By performing a heat treatment of their sputtered C-N iFe Aims, the activity was drastically enhanced but still much lower compared to macrocycle-based catalysts. However, when titanium carbide was used as support instead of carbon, a high stability was obtained. The fact that by changing the support, an essentially better durability was obtained is an important result as it shows that even for catalysts based on molecular centers, alternative support materials can be utilized and that the interaction between the support and the catalytic centers might be cmcial for the optimization of those catalysts for a fuel cell application. 

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