Boro have agreed an undisclosed fee for Boateng with Aston Villa, which is thought to be around £5m. Two previous offers of around £4m were rejected by the Midland club who had valued the player at £7m.
Should he sign for the club he may have to sit out the start of the season through suspension. He was charged with misconduct by the FA yesterday after an incident in a game at the end of last season.
Referee Graham Poll has included the incident in his match report, involving a bust-up with Leicester City's Paul Dickov, when Boateng lost his boot in a challenge with Dickov and hurled it towards a crowded stand.