In a surprise move, B. Kevin Turner, Microsoft's chief operating officer, is joining the Chicago financial firm Citadel to run its technology-heavy market-making unit.



Turner, 51, plans to start the Citadel job in September, according to a person familiar with the matter. Having spent 10 years at Microsoft, including overseeing the sales and marketing of Office 365, he is well-versed in managing a large global team and launching technology platforms for wide distribution.

Turner will join Citadel as chief executive officer of the company's securities business, which is centered on a multifaceted trading platform that handles orders for everything from stocks to interest rate swaps. He will also be a vice chairman of the firm.

A one-time cashier at Wal-Mart, Turner was named a corporate officer there at age 29, the retailer's youngest ever at the time. He later became CEO of Wal-Mart's Sam's Club division.