A bit of musical chairs is taking place on Wall Street, with NYSE chief John Thain taking over at Merrill Lynch & Co. Inc., and his deputy stepping into his job.

Merrill Lynch announced that Thain, CEO of NYSE Euronext, Inc. and former president and chief operating officer of Goldman Sachs Group, has been appointed chairman and CEO, effective December 1.

Thain, 52, joined the NYSE on January 15, 2004. Prior to joining the NYSE he was with Goldman in various roles. He is a member of The MIT Corporation, the Dean’s Advisory Council – MIT/Sloan School of Management, INSEAD – U.S. National Advisory Board, the James Madison Council of the Library of Congress and the Federal Reserve Bank of New York’s International Capital Markets Advisory Committee. He is also a member of the Board of Managers of The New York Botanical Garden, a member of the Board of Directors of the French-American Foundation, a trustee of New York-Presbyterian Hospital and a General Trustee of Howard University.

Thain received an MBA from Harvard University in 1979, and a B.S. degree from Massachusetts Institute of Technology in 1977.

He replaces Stan O’Neal who resigned in the wake of Merrill’s large losses due to the credit crunch.

To replace Thain, the NYSE Euronext board of directors appointed Duncan Niederauer as CEO. He is currently president and co-COO of the exchange. Niederauer, 48, joined NYSE Euronext on April 9 of this year. He was formerly with Goldman too, starting there in 1985. In 2000, he relocated to the headquarters of Spear, Leeds & Kellogg, managing the firms’ global clearing and execution business. He earned an MBA from Emory University and a BA from Colgate University, where he currently serves on the Board of Trustees.

“In Duncan, we move forward with an outstanding individual who has contributed to our global business strategy and has in-depth knowledge and experience in securities trading and the rapidly evolving exchange landscape,” said Jan-Michiel Hessels, chairman, NYSE Euronext. “On behalf of the NYSE Euronext Board of Directors, I look forward to working with Duncan on producing value for our customers and shareholders and building upon the growth and success realized in recent years.

As per the NYSE Group-Euronext merger agreement, the appointment of Niederauer is subject to the non-objection of the European College of Regulators. Following confirmation, he will become a member of the NYSE Euronext board.

Alberto Cribiore, Merrill Lynch’s interim non-executive chairman and chairman of the company’s search committee commented, “John Thain is the right person to become the new chairman and CEO of Merrill Lynch. He brings unparalleled leadership experience and knowledge of the complexities of global capital markets as well as the skills required to operate a large financial services company. John will be adept at balancing the focus on risk management and controls while taking the steps necessary to ensure the company evolves and grows. He understands both the company’s challenges, and as his track record shows, he appreciates the value associated with the Merrill global brand. We are delighted to welcome him aboard.”