Rosenthal joined Morgan Stanley in 2008 from real-estate firm Tishman Speyer, as head of firm-wide technology and operations.

The following year Nides became COO, taking on the role of overseeing IT and operations with Rosenthal named head of corporate strategy and COO at Smith Barney, Morgan Stanley's brokerage joint venture with Citi, overseeing its integration.

In his new role, the COO will have responsibility for operations and technology, human resources, corporate communications, marketing, community affairs and corporate services.