Gold(I) bromide can be formed by synthesis from the elements or partial decomposition of gold(III) bromide by careful control of temperatures and pressures.

Structure

It occurs in two modifications. One (I-AuBr) is isostructural with

gold(I) chloride Gold(I) chloride is a compound of gold and chlorine with the chemical formula AuCl. Preparation Gold(I) chloride is prepared by thermal decomposition of gold(III) chloride Gold(III) chloride, traditionally called auric chloride, is a compou ...

and has a body centered tetragonal unit cell with a = 6.734 Å, c = 8.674 Å, and

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

I4₁/amd. The other (P-AuBr) is isostructural with gold(I) iodide and has a primitive tetragonal cell a = 4.296 Å, c = 12.146 Å, and space group P4₂/ncm. Single crystals of both modifications have been grown by

chemical vapor transport In chemistry, a chemical transport reaction describes a process for purification and crystallization of non- volatile solids. The process is also responsible for certain aspects of mineral growth from the effluent of volcanoes. The technique ...

. Small amounts of

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

, gallium, or

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

were used as catalysts for the transport process to obtain the I-AuBr modification. The two structures both consist of -Br-Au-Br-Au-Br-

polymeric A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic an ...

zigzag chains, but they are stacked in a different arrangement. In the primitive tetragonal I-AuBr, the chains form layers (see figure) in contrast to the body centered P-AuBr, where they are more interwoven. Another difference is that the Au-Br-Au angle is only 77° in the former, but 92.3° in the latter. Density functional calculations on the monohalides of group 11 (Cu, Ag, Au) have tried to shed light on the question why gold halides form rather different, low symmetry structures rather than the cubic zinc blend or rock salt structures of the silver and copper halides. It was shown that this calculation technique accurately predicts which structure type should be stable. The peculiar structures of the gold halides are mostly a result of the relativistic effects that occur for the elements of the later periods of the periodic table.

References

External links

Gold bromide on webelements
{{Bromides Bromides Metal halides Gold(I) compounds Gold–halogen compounds