UPDATE 2-Citigroup names McGuire sole investment bank CEO

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NEW YORK, July 8 (Reuters) - Citigroup Inc (C.N) has named Raymond McGuire sole head of global investment banking, a role he had shared for the last four years.

The announcement came after Citigroup named Alberto Verme, who had shared investment banking oversight with McGuire, as co-chief executive of Europe, the Middle East and Africa, along with Bill Mills.

McGuire's appointment was announced in an internal memo by John Havens, head of the New York-based bank's institutional clients group. Citigroup confirmed the memo's contents.

Vikram Pandit, the bank's chief executive, is trying to retain top executives as the government prepares to take a 34 percent equity stake in Citigroup, which lost $36 billion in the six quarters ended March 31.

The latest announced top departure came last month when Ajay Banga, head of Citigroup's Asia-Pacific business, left to become president of MasterCard Inc (MA.N), putting him in line to become chief executive of the credit card network.

Citigroup on Monday named Shirish Apte and Stephen Bird to replace Banga.

McGuire joined Citigroup in 2005 from Morgan Stanley (MS.N), where he was co-head of mergers and acquisitions. He was previously a managing director at Merrill Lynch & Co and an original member of Wasserstein Perella & Co.

"Ray's priorities include attracting and retaining the best talent, providing first-class advice to our platinum and core clients and growing our revenue, profit and market shares," Havens said in the memo.

In the first six months, Citigroup ranked fourth worldwide in debt and equity underwriting and first in providing merger advice, based on announced transaction volumes, Thomson Reuters data show. (Reporting by Jonathan Stempel; Editing by Steve Orlofsky)