Thallide

Thallides are compounds containing anions composed of thallium. There are several thallium atoms in a cluster, and it does not occur as a single Tl− in thallides. They are a subclass of trielides, which also includes gallides and indides. A more general classification is polar intermetallics, as clusters contain delocalized multicentre bonds. Thallides were discovered by Eduard Zintl in 1932.

Mixed anion compounds with thallides include halides (bromides and chlorides), oxides, and tetrelates (silicate, germanate).

Production
Thallide compounds can be produced by melting metals together in a tantalum crucible under an inert argon atmosphere. However if arsenic is included in the mix, it can react with the crucible wall.

A low temperature production route, is to dissolve an alkali metal in liquid ammonia, and use that to reduce a thallium salt, like thallium iodide.

Properties
Thallide compounds are dense, dense to X-rays and usually metallic grey or black in appearance.

Thallide clusters mostly do not follow Wade-Mingos rules or the Zintl–Klemm concept, as they have too small a negative charge. They can be called "hypoelectronic".

Reactions
In liquid ammonia, oxidation occurs yielding metal amides, and thallium metal.

Thallides react with water and air.