I think that it is impossible unless you use a cheat or something. If you want Palkia catch it in Pearl and then use the poke transfer.
NO
You cannot catch Palkia in Pokemon Black and White you much use Poke Transfer on Route 15
you cant
You can't
You can't catch those Pokemon on Pokemon Black. You'll have to either trade for them or transfer them from a DS Series game.
To catch Palkia, you have to get a Lustrous Orb from Pokemon Pearl, and an Adamant Orb from Pokemon Diamond. Then you have to go to Temporial Tower. You will have to catch/defeat Dialga first, then catch Palkia.
Dialga and Palkia are unobtainable in Black 2 (or any other game in Generation 5 (BW, BW2))
To catch palkia you will need to trade him with Pokemon pearl. NOTE: You catch palkia in pearl and dialga in diamond.
You can't catch Palkia in Pokemon Diamond, you'll have to trade with Pokemon Pearl
Palkia
You can't catch Palkia in Diamond. You'll have to trade it from Pearl, Platinum, Black2 or OmegaRuby. You can also trade it from HeartGold/SoulSilver, Black, X/Y or AlphaSapphire, if you've visited an event.
You cannot catch palkia in pokemon diamond!