Bear in mind that both Storage vMotion and vMotion restrictions apply. You say difference vCenter cluster. Does this mean you have one vCenter but two clusters or two vCenters ?
Assuming you got one vCenter, two clusters, one with two hosts and one with a single host, you have to meet all requirements in order to (s)vMotion the VMs between clusters. This includes networking, storage and even CPU / EVS
It all depends on your setup so I think we'd need to see more of your environment to be able to help properly (especially versions used)