Synthesis, Characterization, and Selected Properties of 7‐ and 12‐Ammoniocarba‐<i>closo</i>‐dodecaboranes

Abstract

Abstract The inner salts 12‐H 3 N‐ closo ‐1‐CB 11 H 11 (H 1 ) and 7‐H 3 N‐12‐Hal‐ closo ‐1‐CB 11 H 10 [Hal = F (H 3 ), Cl (H 4 )] were synthesized by a microwave‐assisted Buchwald–Hartwig amination starting from the corresponding monoiodinated { closo ‐1‐CB 11 } clusters and LiN(SiMe 3 ) 2 . H 1 was methylated to result in the zwitterion 12‐Me 3 N‐ closo ‐1‐CB 11 H 11 ( 2 ). All new compounds were characterized by multinuclear NMR spectroscopy, elemental analysis, and mass spectrometry. The crystal structures of H 1· Me 2 CO and 2 were determined. The p K a value of H 1 in aqueous solution was estimated by potentiometric titration and by 11 B{ 1 H} NMR spectroscopic studies. The stepwise deprotonation of H 1 with n BuLi in [D 8 ]THF was studied by multinuclear NMR spectroscopy. In a first step, the amine 1 is obtained and then the amide [12‐HN‐ closo ‐1‐CB 11 H 11 ] 2– and finally the trianion [12‐HN‐ closo ‐1‐CB 11 H 10 ] 3– or more probably lithiated species thereof are formed. The experimental spectroscopic and structural data, as well as the p K a value of H 1 are compared to values derived from DFT and ab initio calculations.