One thing that is easy to trade to the AI... is star system charts. About 100 to 200 of the same one... all at once. It is very cheap and takes advantage of the AI. I wouldn't do it but I have tested it out and it works. Also when trading techs try offering other techs with an equal or greater research point value and then through in a few thousand resources as extra.
As for Xenophobes... the best way to deal with them is to get them before they get you.
Of course the real strength of the SE4 diplomacy engine is in playing other people. The AI just won't take advantage of most of what it can do.
For instance if you demand it leave from a system or abanadon a colony it may very well agree to do so. And then never do it. Same with breaking treaties etc.
The AI in diplomatic relations is weak. There are tons of ways to trade with it that take advanatage of that weakness, ala lots of the same system chart and others.