Board Thread:Naruto Discussions/@comment-7292165-20140715160041/@comment-1251315-20140716102036

Rokubi was captured by Pain in the anime only Tsuchigumo Kinjutsu Arc, Seelentau. I don't think Nine-Tails was assigned to any particular Akatsuki member, Itachi (most likely) simply claimed that he was assigned to get Naruto, since he always came into contact. The only official assignment of an Akatsuki member to Nine-Tails was Pain / Nagato.