Synthesis of the First Example of the 12-Vertex-closo/12-Vertex-nido Biscarborane Cluster by a Metal-Free B-H Activation at a Phosphorus(III) Center

An unusual 12-vertex-closo-C2B10/12-vertex-nido-C2B10 biscarborane cluster was synthesized through an unprecedented regioselective metal-free B-H activation by a sterically hindered P-III center under mild conditions accompanied by cage-opening rearrangement. A combination of the electron-accepting properties of a carborane cage and steric enforcement of close interatomic contacts represent a new synthetic strategy for the activation of strong B-H bonds in carboranes.