Platinum with six chlorine atoms bound to it, overall charge of -2. Two potassium counterions are associated.
ransition metals are found in the middle of the periodic table. In addition to being found in the metallic state, they also form a range of compounds with different properties. Many of these compounds are ionic or network solids, but there are also some molecular compounds, in which different atoms are arranged around a metal ion. These compounds are called transition metal complexes or coordination complexes. They are often brightly-colored compounds and they sometimes play very useful roles as catalysts or even as pharmaceuticals.
Because of their relatively low electronegativity, transition metals are frequently found as positively-charged ions, or cations. These metal ions are not found by themselves, instead, they attract other ions or molecules to themselves. These species bind to the metal ions, forming coordination complexes.
Hexaamminecobalt(III) chloride, [Co(NH3)6]Cl3, is an example of a coordination complex. It is a yellow compound. The "complex" part refers to the fact that the compound has a bunch of different pieces. There is a cationic part, which itself is a moderately complicated structure, plus three chloride anions.