Synthesis and characterization of anionic polybrominated carboranyl azides

Here we describe the azide functionalization of polybrominated derivatives of the carba-closo-dodecaborate anion. Specifically, treatment of [HCB11Br11] and [HCB11H5Br6] with n-BuLi, followed by subsequent reaction with tosyl azide, yields the novel carboranyl azides [N3CB11Br11] and [N3CB11H5Br6]. In contrast to its perchlorinated congener, the [HCB11Br11] anion does not undergo competitive B-Br activation to produce a carborane-fused triazole; instead, it forms the azide in a perfectly selective manner. These polybrominated carboranyl azides have been characterized by IR, NMR, and HRMS. Additionally, we describe the first single-crystal X-ray diffraction studies of azide derivatives of the carba-closo-dodecaborate anion, as well as a neutral isoelectronic ortho-carborane azide (1-N-3-2-Ph-C2B10H10). (C) 2014 Elsevier B. V. All rights reserved.