Syntheses of 3-DBU-closo-2-CB_6H_6 and [3-Cl-closo-2-CB_6H_6]~- - A first straightforward syntheses of [CB_6]-closo-clusters

摘要

The closo-hydro-borate [B_6H_6]~(2-) reacts with DBU (= 1,8-Diazabicyclo[5.4.0]undec-7-en) in chloroform to give a mixture of two different seven-vertex monocarboranes, 3-DBU-closo-2-CB_6H _6 and [3-Cl-closo-2-CB_6H_6] -. Dichlorocarbene, which is generated in situ by the reaction of DBU with chloroform at elevated temperatures, subsequently inserts into the [B_6H_6]-closo- cluster to result in 3-DBU-closo-2-CB_6H_6 as main product [3-Cl-closo-2-CB_6H_6] - was obtained as a byproduct. Both novel carboranes were isolated and characterized by 1H, 1H{ 11B), 11B, 11B{ 1H} and 13C NMR spectroscopy. The structures of 3-DBU-closo-2-CB_6H _6 as well as [3-Cl-closo-2-CB_6H_6] - were determined by single-crystal X-ray diffraction.