Gregg Lemkau, co-head of Goldman Sachs' investment banking unit, is set to leave the firm in January after more than 28 years, to join tech titan Michael Dell's family office.

Lemkau, a respected name in banking who has worked on some of the biggest ever technology deals, will hand over the reins to his co-head Dan Dees and Jim Esposito, who will move over from leading its global markets unit.