(Adds details from memo and information about executives)
By Brenna Hughes Neghaiwi and David Henry
ZURICH/NEW YORK, Sept 4 (Reuters) - Citigroup Inc's longtime Chief Financial Officer John Gerspach will retire in March, to be replaced by Mark Mason, CFO of the institutional clients group, the third-largest U.S. bank told employees on Tuesday.
Gerspach, an accountant, joined Citigroup in 1990 and became CFO in July 2009. He became known for fielding analyst questions about the company's irregular progress in divesting businesses, satisfying new capital rules imposed by regulators and failing to meet financial targets.
He also had to answer for problems that cropped up at far-flung operations around the world, including losing $500 million on fraudulent loans in its Mexican bank.
"He has represented our company exceptionally well, not just in good times but in tough ones as well," Chief Executive Officer Mike Corbat said in the memo seen by Reuters.
Corbat also announced that North America CEO Bill Mills and Europe, Middle East and Africa CEO Jim Cowles would be leaving the bank at year-end, and named Kristine Braden, who is country officer for Switzerland, as his new chief of staff.
The changes follow an executive shuffle a few weeks ago at Citigroup's consumer bank, which has had trouble keeping up with performance expectations on Wall Street.
Mason takes over the CFO role at a time of investor frustration with Citigroup's lagging stock price. Its shares trade for about 1.2 times tangible book value compared with 2.1 times for shares of JPMorgan Chase & Co, the largest U.S. bank by assets.
The institutional clients group where Mason is now finance chief provides trading, lending, treasury and investment banking services to large companies. He is also responsible for submitting Citigroup's capital plans to the U.S. Federal Reserve as part of its annual stress test, a process that determines how much money the bank can return to shareholders through dividends or stock buybacks.
In prior roles, Mason worked closely with Corbat to unload Citigroup's troubled assets following the 2007-2009 financial crisis, and later ran the private bank that caters to ultra-wealthy individuals.
Mason grew up in Queens, New York, and lived in a house overlooking an expressway to John F. Kennedy International Airport, he said in a 2017 podcast interview with the president of Howard University, his alma mater.
He and his younger brother were raised by a single mother with help from family members who lived nearby. He went to public schools until attending Howard for his undergraduate degree, then getting an MBA from Harvard Business School.
"We didn't have much, but we had a lot of family," Mason said. "So, it was a good childhood, but it was one that was short of money in ways, so I learned very early on the importance of hard work and the correlation between that and achievement and money." (Reporting by Brenna Hughes Neghaiwi in Zurich and David Henry in New York Writing by Lauren Tara LaCapra Editing by Edmund Blair and Richard Chang)