4 NH4OH + MnIICl2 + Br20 2 NH4Br-I + 2 NH4Cl + MnIVO2 + 2 H2O

This is an oxidation-reduction (redox) reaction:

2 Br0 + 2 e- 2 Br-I (reduction)

MnII - 2 e- MnIV (oxidation)

Br2 is an oxidizing agent, MnCl2 is a reducing agent.