Complex sentence: The Institute's Director General Rajendra K. Pachauri was replaced by Ajay Mathur on 23 July 2015 because currently he is fighting a case of sexual harassment against a junior female colleague.
Split into simpler sentences: The Institute's Director General Rajendra K. Pachauri was succeeded by Ajay Mathur on 23 July 2015. Dr. Rajendra Pachauri is has been accused of sexual harassment against a junior female colleague.