Natixis Global Asset Management has reached an agreement to acquire McDonnell Investment Management LLC, an Oak Brook, Illinois-based registered investment advisor with approximately $13.5 billion in assets under management, company officials announced today.

Financial terms of the deal were not disclosed.

McDonnell provides investment management services to institutions, private clients and mutual fund companies. The firm manages several investment disciplines for portfolios of taxable securities (U.S. government and agency bonds, structured securities and corporate bonds) and municipal bonds.

McDonnell will expand the NGAM products it distributes through its global distribution network. NGAM expects to launch a new municipal bond product in early 2013. McDonnell will continue to operate autonomously with no change in management or staff, NGAM officials said. And it will also retain its brand name and its suburban Chicago headquarters.

McDonnell was founded as a 100 percent employee-owned company on November 1, 2001, by former employees of Van Kampen Management Inc. Dennis McDonnell, chairman, and Edward Treichel formed a fixed-income team in 1987 at Van Kampen, growing it for more than a decade until they acquired the business from Van Kampen Investments Inc.

Boston-based NGAM is a subsidiary of Natixis Global Asset Management, S.A. Headquartered in Paris and Boston, Natixis Global Asset Management, S.A.'s assets under management totaled $711 billion as of June 30.