You can look up the IP Domain itemid by going to http://DA:8581/rest/ipdomains. With the ID of the IP Domain to change to..
Do a PUT to http://DA:8581/genericWS/dcm/<ITEMID of DC>
Body:
<DCM><IP_DOMAIN_ID>ipDomainItemId</IP_DOMAIN_ID></DCM>
It will assign the DC to the IP Domain and Tenant the IP Domain belongs to.
NOTE: the DC needs to be empty (except for the DC's own device, if there) to assign to a diff domain/tenant.