If you let the chip actual boil enough water to run a turbine you're going to have a hard time keeping the magic smoke inside. Much better to run at reasonable temps and try to recover energy from the waste heat.
That's basically the principle of binary cycle[1] generators. However for data center waste heat recovery, I'd think you'd want to use a more stable fluid for cooling, and then pump it to a separate closed-loop binary-cycle generator. No reason to make your datacenter cooling system also deal with high pressure fluids, and moving high pressure working fluid from 1000s of chips to a turbine of sufficient size, etc.
There's a bunch of places in Europe that use waste heat from datacenters in district heating systems. Same thing with waste heat from various industrial processes. It's relatively common practice.
If my very stale physics is accurate then even with perfect thermodynamic efficiency you would only recover about a third of the energy that you put into the chips.