Synthesis and Characterization of 14-Vertex Carboranes

Twelve new 14-vertex closo-carboranes, including CAd (carbon atoms adjacent), CAp (carbon atoms apart), and cage B-substituted species, were synthesized and structurally characterized via either a [13 + 1] or a [12 + 2] polyhedral expansion protocol. Treatment of various 13-vertex nido-carborane dianionic salts with HBBr2 gave the corresponding 14-vertex carboranes. Mono-B-substituted 14-vertex carboranes 1-R-2,3-(CH2)3-2,3-C2B12H11 (R = Ph, Cl, Br, I) were prepared from the reaction of nido-[8,9-(CH2)3-2,3-C2B11H11]2– with the dihaloborane reagents RBX2. CAd 14-vertex closo-carboranes were also synthesized by treatment of 12-vertex arachno-carborane tetraanionic salts with HBBr2 reagent. These new 14-vertex closo-carboranes were fully characterized by 1H, 13C, and 11B NMR spectroscopy as well as high-resolution mass spectrometry. Their structures were further confirmed by single-crystal X-ray analyses.