4 Au + 16 NaCN + 3 O2 + 6 H2O → 4 Na[Au(CN)4] + 12 NaOH
This is a complexation reaction: Na[Au(CN)4] is the formed complex.
This is an oxidation-reduction (redox) reaction:
4 Au0 - 12 e- → 4 AuIII (oxidation)
6 O0 + 12 e- → 6 O-II (reduction)
Au is a reducing agent, O2 is an oxidizing agent.