Multisite with separate logins

I have set up a multisite wordpress with 4 sites. I want to use one site as a main landing site with a few pages and a login. I am looking for a way to, based on the user credentials, redirect and log them into a separate site that is all member only protected. Does anyone know of a good plugin that could help me with this? I have googled and searched the forums but havent found anything that can do this. I have tried s2member, wp-members, members, paid memberships pro, and a few others but none of them seem to be able to do it. s2member has had the best results for me so far but it still isn’t working the way I’d like it to. Am I missing something?