7 Al + 3 KNO3 + 4 KOH + 15 H2O → 7 K[Al(OH)4] + 3 NH2
This is a complexation reaction: K[Al(OH)4] is the formed complex.
This is an oxidation-reduction (redox) reaction:
7 Al0 - 21 e- → 7 AlIII (oxidation)
3 NV + 21 e- → 3 N-II (reduction)
Al is a reducing agent, KNO3 is an oxidizing agent.