2 Al (s) + 6 C2H2 (g) + 9 H2 (g) → 2 (C2H5)3Al (l)
This is an oxidation-reduction (redox) reaction:
12 C-I + 24 e- → 12 C-III (reduction)
18 H0 - 18 e- → 18 HI (oxidation)
2 Al0 - 6 e- → 2 AlIII (oxidation)
C2H2 is an oxidizing agent, H2 is a reducing agent, Al is a reducing agent.