How to catch entie and raikou?

Okay so heres my predicament I have been trying to catch entie and raikou for ages now I have spent just over 300 pokeballs tryin to get them they are both paralysed and have the health reduced to red and still they are impossible to catch. I even had wobbufet to stop them from running but still nothing and they also roar so I can never seem to have them. I use ultra balls to try and catch them. Has anyone any suggestions on how to get these pokemon thanks