Crystal Structures of the Carborane Dianions [1,4‐(PhCB 10 H 10 C) 2 C 6 H 4 ] 2− and [1,4‐(PhCB 10 H 10 C) 2 C 6 F 4 ] 2− and the Stabilizing Role of the para ‐Phenylene Unit on 2 n +3 Skeletal Electron Clusters

While carboranes with 2  n +2 and 2  n +4 ( n =number of skeletal atoms) skeletal electrons (SE) are widely known, little has been reported on carboranes with odd SE numbers. Electrochemical measurements on two‐cage assemblies, where two C‐phenyl‐ ortho ‐carboranyl groups are linked by a para ‐phenylene or a para ‐tetrafluorophenylene bridge, revealed two well separated and reversible two‐electron reduction waves indicating formation of stable dianions and tetraanions. The salts of the dianions were isolated by reduction with sodium metal and their unusual structures were determined by X‐ray crystallography. The diamagnetic dianions contain two 2  n +3 SE clusters where each cluster has a notably long carborane C–carborane C distance of ca 2.4 Å. The π conjugation within the phenylene bridge plays an important role in the stabilization of these carboranes with odd SE counts.