After a few games i know for sure that the ai need that specefic technologie(giving resources or demand). You need also a good relation with that ai-player.
Also i noticed some other things.
1.The ai receives no penalty when they failed to do the mission i gave them.
2. the ai players sending no missions to other ai- players
3. they only goes up in DP with their diplomatic relation with a human player(bonus/envoys....etc)
4. ai players never reject missions for killing ships/planet etc...., only for resources.. Example "kill 20 ships in 5 minutes
). After this 5 minutes nothing happens..no penalty.
I have to play another few games to know these things are fore sure.