Octahedral Hexatantalum Halide Clusters

Inorganic Syntheses, Volume 36, First Edition. Edited by Gregory S. Girolami and Alfred P. Sattelberger. 

Ta6Bri4 was first prepared in 1910 by sodium amalgam reduction of TaBrs. It has since been preparedby using thereductants aluminum and excess tantalum and can be isolated by aqueous extraefion as the discrete clusto Ta6(p-Br)i2Br2(OH2)4  

There is considerable interest in the coordination and catalytic chemistries of these discrete clusters. Because of its high electron count, the hexaaquo ion [Ta6(p-Br)i2(OH2)6] has been used frequently for phase determination of isomorphous protein derivatives by SIR, MIR, SIRAS/MIRAS, and SAD/MAD methods in biomacromolecular crystallography. This use is growing as larger biomacromolecular structures and assemblies (e.g., membrane proteins, ribosomes, proteasomes) are studied. 

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. 

TaXs (X = Cl, Br Materion Advanced Chemicals, Milwaukee, WI), hydrochloric acid (12M, Fisher Scientific), Ga (99.99%, Atlantic Equipment Engineers, Bergenfield, NJ), NaCl (Fisher), KBr (Aldrich Chemical), SnCl2 2H2O (Fisher), SnBr2 (99.5%, Alfa Aesar), HBr (48%, Fisher), and diethyl ether (anhydrous, Fisher) are used as received. Ga GaCLt is purchased and used as received from 

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