Ammonium diamminetetrathiocyanatochromate(III) is a coordination complex with the chemical formula [Cr(NH3)2(NCS)4]NH4. It is composed of a chromium(III) ion coordinated to two ammine ligands (NH3) and four thiocyanate ligands (NCS^-). An ammonium ion (NH4+) is also associated with the complex as a counterion to balance the charge.

The complex has a distinctive purple color and is commonly used as a reagent in coordination chemistry and analytical chemistry. Some of its key properties and uses include:

1. Coordination Chemistry: Ammonium diamminetetrathiocyanatochromate(III) is a common example of a coordination complex, where the central metal ion (chromium in this case) is coordinated to specific ligands in a specific geometry.
2. Analytical Reagent: It is used as an analytical reagent for detecting the presence of certain metal ions. The complex forms characteristic colored precipitates with some metal cations, which helps identify the presence of those metals in a sample.
3. Chemical Education: Ammonium diamminetetrathiocyanatochromate(III) is sometimes used as a teaching tool in chemical education to demonstrate coordination chemistry principles and color changes in chemical reactions.

It’s essential to note that this complex and its solutions are not commonly used in practical applications due to its limited stability and availability. Like many coordination complexes, it has niche applications in chemical research and educational settings, but its use in practical applications is relatively limited.