After the failure of a $2.2 billion buyout last fall of electronics company 3Com, Edgar Masri is leaving as chief executive and being replaced by Robert Mao, who served as 3Com"s executive vice president for corporate development from August 2006 to March 2007. The shuffling in 3Com"s executive ranks, announced after markets closed Tuesday, leaves Ronald Sege as president and chief operating officer, effective when he arrives at 3Com on Wednesday. A news release from 3Com did not offer a reason for Masri"s departure as CEO.