As I was informed vCenter 5.5 database no longer supports SQl 2005 so I need to move vCenter database from one server to another.
Any particular thing that needs to be done I was under impression that it is just backup database on SQL 2005 and then restore it on SQl 2012 server and change ODBC connection in vCenter
Anything else is needed
Depending on the security model you might need to map the user back to the database as DB owner if you are using AD authentication.
As you are only moving the database you will not move the jobs, so these might need to be recreated as well, you can find them as .sql files in the installation directory of vCenter Server.
This KB explains how to migrate from 2005 express to 2008 full, but it should do the trick!
Yes it will work. Please make sure that when the migration is complete, that you have some new SQL Agent jobs that are created to handle the statistic rollups.