Group 6 metal halide clusters synthesis

Redox Chemistry and Photophysics of the Group 6 Metal Halide Clusters Molecular and Electronic Structure of the Group 6 Metal Halid Clusters Group 5 Metal Halide Clusters A. Synthesis of Cluster Core... 

Substitution reactions involving silylated chalcogen reagents represent a powerful approach in metal-group-XVI cluster synthesis.Compounds such as E(TMS)2 and RE-TMS react readily with metal salts to form metal chalcogenide or chalcogenolate bonds (Equations (13)-(15)). The driving force for the reaction is the thermodynamically favorable formation of an X—Si bond and elimination of X-TMS (where X = halide, OAc, etc.). 

We have found that the main group metal and metalloid reductants mocury, bismuth, and antimony are highly effective " in reducing WCIe or M0CI5 at surprisingly lower temperatures than commonly used in the solid-state synthesis of early transition metal cluster halides. BorosUicate ampules can be substituted for the more expensive and less easily sealed quartz ampules at these lower temperatures, and the metals and metalloids are not as impacted by oxide coatings that inhibit sohd-state reactions with more active metals. These lower temperatures may allow access to kinetic products, such as trinuclear clusters, instead of thermodynamic products. 

Many reduced (metal-rich) halides of group 4 (especially Zr) and the rare earth metals have been prepared. Most of these compounds are stabilized, by the metals forming Mg octahedral or other clusters having strong metal-metal bonds. The reactions to form these clusters are slow. Other nonmetals, especially oxygen, are undesirable impurities that may form more stable phases. Therefore the reactions are carried out with stoichiometric mixtures of pure halide and metal in degassed Ta or Nb tubes that have been loaded in an inert atmosphere and arc-welded shut. The welded ampule is then sealed in a protective quartz tube and heated to a temperature adequate to achieve a reaction in a week or more ( >600°C) . Yields may be small in some cases individual single crystals are produced as evidence of synthesis of a new material with metal-metal bonds. 

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