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Synthesis, Characterization, and Selected Properties of 7‐ and 12‐Ammoniocarba‐ closo ‐dodecaboranes
Author(s) -
Konieczka Szymon Z.,
Himmelspach Alexander,
Hailmann Michael,
Finze Maik
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201200969
Subject(s) - chemistry , deprotonation , nuclear magnetic resonance spectroscopy , amine gas treating , zwitterion , amide , crystallography , spectroscopy , medicinal chemistry , stereochemistry , molecule , organic chemistry , ion , physics , quantum mechanics
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.