Citigroup (NYSE:C) executive Deborah McWhinney, who arrived five years ago in a wealth management role and wound up running its enterprise payments division, announced Monday that she is leaving the bank.

The timing of her departure, effective at the end of January, was precipitated by an opportunity to join the board of a Fortune 250 concern. She says the offer to serve as an independent director, which she expects will be formalized in February, required that she step down from Citi, which provides banking or cash management services to many of the country's largest corporations — including, apparently, the one pursuing her as a director. She has declined to identify the company for now.

McWhinney, 58, says she's been working with senior executives at Citi on a transition plan for the enterprise payments group, which essentially will be disbanded as its three major startup projects — a digital wallet, a health care payments platform and an electronic commerce platform geared toward multinationals — get folded into the various business lines they were intended to augment.

"There are some ideas for new revenue plans for Citi, but right now what we need to do most is get these [initial three ventures] working really well and bring them to scale," says McWhinney, who spent three years with the enterprise payments division. She was promoted this fall from chief operating officer of the group to its global head after Paul Galant, who previously ran the division, left to become CEO of payments software company VeriFone Systems.

McWhinney, a former Charles Schwab executive hired by Citi in April 2009 to run its personal wealth management business, made some controversial calls in her first two years with the bank, including a decision to shift the bank's brokers from a commission model to a fee-based system. In February 2011, it was announced that McWhinney would join the company's new enterprise payments group, as head of global digital merchant acquiring. That role drew on McWhinney's payments experience as an executive vice president at Visa International, where she worked prior to Schwab.

The enterprise payments group was recognized this year by American Banker as one of the industry's top innovators for its health care payments platform, called Money2 for Health, which has been in pilot mode this year and is scheduled to be rolled out to a broader audience in 2014. McWhinney also has been recognized for her individual work, appearing for the past two years on American Banker's annual list of the 25 Most Powerful Women in Banking.

In an employee memo announcing McWhinney's departure, Citi CEO Michael Corbat notes that "Debby has long planned to spend the later stage of her career leveraging both her business experience as well as her significant not-for-profit board service. She is now turning her vision into action and has been asked to join the board of a Fortune 250 company."

McWhinney currently serves on the board of trustees for the Institute for Defense Analysis and the California Institute of Technology.

As co-head of Citi Women, the company's networking group for female executives, McWhinney has been a strong proponent of using nonprofit board service as a stepping stone to corporate board appointments. One of the first subcommittees she formed at Citi Women, she says, was focused on getting more women on the boards of top nonprofits.

McWhinney, who has participated on more than 20 nonprofit, for-profit and internal company boards, says that in the past dozen years, her paths had crossed with several members of the corporate board she plans to join in February. She says those relationships were critical to her next opportunity, which she hopes will make further cracks in the glass ceiling for women in the corporate world.

"I think the next frontier for women is going to be on corporate boards," she says.

The increased demand for directors with knowledge befitting an audit committee or an in-depth understanding of a company's financials bodes well for financial services executives who want to parlay their experience into board appointments, she adds.

McWhinney says she expects the next stage of her career might also include investments and mentorship roles with startups - an interest that she says is based at least in part on "how much I have learned being involved in global payments and digital transformation while at Citi."

But for now she is focused on winding down her work with the enterprise payments group and helping her Citi Women co-chair, markets executive Suni Harford, to maintain the program's momentum while identifying its next generation of leadership.