The Islamic Society of Boston Cultural Center announced Friday that its first permanent imam is leaving for a new job. Imam William Suhaib Webb, an Oklahoma-born convert to Islam who has tried to bridge the divide between traditional Islam and American culture, will leave Jan. 1, said Yusufi Vali, the cultural center’s executive director. Vali said Webb, 42, has accepted another job out of state, to be announced shortly. Webb was in Washington on Friday to speak at an evening event at MakeSpace, a local Muslim organization focused on youth and young professionals. Webb stepped aside from his role as imam in April to become a “resident scholar” at the cultural center.