Synthesis and Characterization of 14-Vertex Carboranes

Twelve new 14-vertex <i>closo</i>-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 <i>nido</i>-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 <i>nido</i>-[8,9-(CH₂)₃-2,3-C₂B₁₁H₁₁]^2– with the dihaloborane reagents RBX₂. CAd 14-vertex <i>closo</i>-carboranes were also synthesized by treatment of 12-vertex <i>arachno</i>-carborane tetraanionic salts with HBBr₂ reagent. These new 14-vertex <i>closo</i>-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