Here's why:

* Manganese (Mn) typically forms stable cations with a +2 or +4 charge.

* Bromine (Br) forms anions with a -1 charge.

To achieve a neutral compound, the charges of the ions must balance. MnBr₅ would require Mn to have a +5 charge, which is not a common oxidation state for manganese.

Possible Compounds:

* MnBr₂ (Manganese(II) bromide): This is a stable compound where manganese has a +2 charge.

* MnBr₄ (Manganese(IV) bromide): This compound is less common but can be formed under specific conditions.

Important Note: It's crucial to consider the oxidation states and charge balance when determining the formula of an ionic compound.