Advances in the chemistry of carboranes and metallacarboranes with more than 12 vertices

Boron clusters with more than 12 vertices showing a very rich and diverse chemistry were confined to the 13- and 14-vertex metallacarboranes until 2003. Very recently, significant progress in the syntheses of 13- and 14-vertex carboranes has been made, leading to the preparation of 15-vertex metallacarboranes. These studies open up new possibilities for the development of polyhedral clusters of extraordinary size. This review summarizes the advances in this growing research field since the successful preparation of the first 13-vertex metallacarborane. Achievements, problems and perspectives are discussed in this article.