Shares in 3i bounced into positive territory on Monday after the FTSE 100 investment group named Simon Thompson as its new non-executive chairman, replacing Sir Adrian Montague.Thompson, who joined the board as a non-executive director effective immediately, said the appointment was a "great privilege"."I'm looking forward to joining 3i and helping build on the firm foundations for growth and future success laid down during Sir Adrian's chairmanship," he said.Montague, who is stepping down to concentrate on his other commitments including taking the chair at insurance giant Aviva, will be succeeded at 3i's annual general meeting on 25 June.The group also announced that current director Jonathan Asquith has been appointed as deputy chairman.Montague, who become 3i chairman in 2010, said: "I am sorry to be stepping down from 3i at this exciting time because of my other responsibilities. I am confident that I am leaving the company in very good hands."