(City A.M. (UK) Via Acquire Media NewsEdge) ? THOMAS Montag has been appointed the sole chief operating officer at Bank of America Merrill Lynch following the departure of co-chief David Darnell, who leaves to become vice-chairman. Montag joined the bank in 2009, before which he was a trading executive at Goldman Sachs. Montag and Darnell were appointed joint COOs in 2011 by the bank's chief executive Brian Moynihan. Montag is widely tipped as a possible successor to Moynihan.