Synthesis and crystal structure of an assembly of three ortho‐carborane cages linked via para‐phenylene units: effect of aryl orientation on cage CC bond lengths in C‐aryl‐ortho‐carboranes

The synthesis and crystal and molecular structure are described of (C 2 B 10 H 11 )C 6 H 4 (C 2 B 10 H 10 )C 6 H 4 (C 2 B 10 H 11 ) ( 4 ), an acyclic assembly of three ortho ‐carborane units connected through their carbon atoms by two para ‐phenylene units. For this compound, and published structures of other aryl‐ ortho ‐carboranes, correlations are noted between the orientations of aryl substituents and cage carbon–carbon distances (C1C2). Ab initio RHF/6‐31G * and MP2/6‐31G * studies on 1‐phenyl‐ ortho ‐carborane, PhC 2 B 10 H 11 , and other model systems have been used to explore the variations in their energies, C1C2 bond lengths, and C2C1C aryl bond angles with the orientation of their aryl groups, variations believed to reflect weak interactions between the aryl substituents' π systems and the carborane cages. The synthesis of a pentafluorophenyl derivative of 4 , (C 2 B 10 H 11 )C 6 H 4 (C 2 B 10 H 10 )C 6 H 4 (C 2 B 10 H 10 )C 6 F 5 , is also described.