Facile synthesis of closo-nido bis(carborane) and its highly regioselective halogenation

1,1'-Bis(ortho-carborane) undergoes mild deboronation in solution in the presence of water with formation of the [7-(1',2'-closo-C2B10H11-1'-)-7,8-nido-C2B9H11](-) (1) anion. The chlorination of 1 with N-chlorosuccinimide in acetonitrile proceeds highly regioselectively to give [7-(1',2'-closo-C2B10H11-1'-)-9- Cl-7,8-nido-C2B9H10](-) (2) as the main product, whereas its bromination and iodination with elemental halogens results exclusively in [7-(1',2'-closo-C2B10H11-1'-)-9-X-7,8-nido-C2B9H10](-), X = Br (3) and I (4), respectively. The structure of [Me3NH][7-(1',2'-closo-C2B10H11-1'-)-9-X-7,8-nido-C2B9H10] was determined by single-crystal X-ray diffraction. (C) 2016 Elsevier B.V. All rights reserved.