Mild C-H activation of activated aromatics with [8,8′-μ-I-3,3′-Co(1,2-C2B9H10)2]: Just mix them

Reactions of the iodonium derivative of cobalt bis(dicarbollide) anion [mu-8,8'-I-3,3'-Co(1,2-C2B9H10)(2)] with activated aromatics were studied. The reactions with ortho-and meta-xylenes result in mild arene C-H activation under ambient conditions, whereas the reaction with para-xylene requires the presence of PPh3 as soft Lewis base. The obtained aryl derivatives [8-Ar-8'-I-3,3'-Co(1,2-C2B9H10)(2)](-) were found to have the transoid conformation both in the solid state and in solution due to intramolecular hydrogen CHcarb center dot center dot center dot IB bonds and aromatic CHcarb center dot center dot center dot pi interactions between the dicarbollide ligands. The Lewis acidity of the quasi-borinium cation formed on the breakage of the iodonium bridge was estimated using Beckett-Gutmann method. According to the Gutmann acceptor number AN = 112 (in CD2Cl2), this quasi-borinium cation belongs to the most strong boron Lewis acids and can be considered as Lewis superacid. (C) 2012 Elsevier B. V. All rights reserved.