Dissolving metal reductions
Is there a goal here? If you wanted to react aluminium with concentrated aq ammonia, you would get hydrogen but the rate would be proportional to temperature.  However, this would be quite a poor way to create a reductive environment and as someone has already alluded, aluminium and sodium hydroxide or a strong mineral acid is better. From what I've seen, if you use alkali, a catalyst is needed.
Ethylamine can be more conveniently used in place of ammonia. 
Calcium can also be used in reductions.I think I've also seen Indium, but that seems a bit expensive.