Green would be a very difficult fit for salary cap purposes for the Clippers. They are above the luxury tax and pushing the hard cap. They're also short on expirings. Hawes and Barnes, as was mentioned, fits, but I'm not sure Spencer Hawes fits Danny's plan of not taking on salary for next year - he's got two more guaranteed years and a player option after that. And he's got a 15% trade kicker to boot. Barnes is guaranteed a million by himself. They're also short on first-round picks, since they can't trade one until I believe 2019 (which is sort of like Memphis' situation, except Memphis isn't sending back about $20 million in future salary obligations).
Hoenstly, the only thing that the Clips can offer to make sense from the Celtics perspective is Deandre Jordan. I don't think that happens, but there is no way Jeff Green winds up in LA without a third team getting involved.