That won't do it, it only extends 24" from the wall at the furthest point, so a 50" TV won't go 90 degrees, not even close.
OP, you're unlikely to find something that will do what you want, mainly because the size of the TV... just a question though, couldn't you face the other way in bed and instead have it mounted flat to the other wall? and use an extension/multi-plug if you need to.