Unfortunately, Fe(NH3)2 is not a correct chemical formula. You may have confused it with some other substances that exist in chemistry. Students may have had difficulties in reading chemical formulas. These are elements that need to be accurately identified to understand a substance in chemistry.
However, I can explain about chemical substances related to iron (Fe) and ammonia (NH3) – such as hexaammineiron(II) [Fe(NH3)6]2+ or tetraamminediaquairon(III) [Fe(NH3)4(H2O)2]3+ which are complex compounds of iron with ammonia.
If you want to know more about a specific chemical substance, please provide the correct formula of that substance.