If you want to upgrade the host in its current vCenter environment vCenter will need to be upgraded or leave the ESXi host at 4.1 - vmotion the vms to it remove it from the 4.1 vcenter and then add it to the new vCenter 5 environment and then do you upgrade -
I would also spend some time and review VMware's upgrade guide - http://pubs.vmware.com/vsphere-55/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-55-upgrade-guide.pdf