Coup de Grace on constructs

[shaggy1987]

I am making a creature with the Clockwork Automaton ‎Template and I am wondering "How effective would a Coup de Grace be against it?". It would only work if it was held or bound. But what would "Coup de Grace" do and what wouldn't it do?

Construct have:
• Immunity to bleed, disease, death effects, necromancy effects, paralysis, poison, sleep effects, and stunning.
• Immunity to any effect that requires a Fortitude save (unless the effect also works on objects, or is harmless).
• No immunity to critical hits(I think)

Can you pleace tell me? Because I don't know and I can't find it.

[RainyDayNinja]

It's still subject to crits, so it should take the full damage, but it's immune to the part that requires a Fort save, so no automatic kills.

[n o 417]

The death effect from coup de grace does not work, as it requires a fortitude save, which constructs are immune to.