It looks to me that you're trying to remove the seatback from the seat bottom?
If you are, you need to remove the 2 bolts on the other side (by the reclining motor connected to the seatback). These bolts hold the outboard side of the seatback to the seatbottom frame.
Once you remove those 2 bolts, disconnect the wires, and the hose to the lumbar airbag. Then you just move and rotate the seatback around and that pin will come out of that bracket on the seatbottom. The pin is connected to the seatback frame. You don't remove it, you just separate it from the seatbottom frame. You'll see what I mean when you get it apart.