i was wondering when u use an event card that says:

e.g. "gain 2 marines, 2 zerglings or 1 zealot in empty of friendly area"

can i put those units in empty area of my opponent planet if i dont have a connecting transport?

Of course you can. At least, there is no rule what could forbid such move.

It doesn't matter which planet you choose, you may always place those units unless it contains unit(s), base or instalation of other player.

tx alot,

i was confused when i read one leadership card that says smth like: " put 2 xxx units in friendly or empty area on any planet "

but on event cards it doesnt say on any planet

and we still argue with friends about this

You defintely can. That's the cool thing about this card. You dump some reinforcements in the enemy's unprotected back and even if you don't use them anymore, your enemy needs a whole order just to get them out.