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Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity
Author(s) -
Englert Lukas,
Stoy Andreas,
Arrowsmith Merle,
Muessig Jonas H.,
Thaler Melanie,
Deißenberger Andrea,
Häfner Alena,
Böhnke Julian,
Hupp Florian,
Seufert Jens,
Mies Jan,
Damme Alexander,
Dellermann Theresa,
Hammond Kai,
Kupfer Thomas,
Radacki Krzysztof,
Thiess Torsten,
Braunschweig Holger
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201901437
Subject(s) - adduct , chemistry , steric effects , carbene , phosphine , lewis acids and bases , halide , ligand (biochemistry) , frustrated lewis pair , nuclear magnetic resonance spectroscopy , stereochemistry , crystallography , medicinal chemistry , organic chemistry , catalysis , receptor , biochemistry
A series of 22 new bis(phosphine), bis(carbene), and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B 2 X 4 precursors (X=Cl, Br, I) or by ligand exchange at stable B 2 X 4 (SMe 2 ) 2 precursors (X=Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopy, elemental analysis, and, for 20 of these compounds, single‐crystal X‐ray diffraction, revealing an unexpected variation in the bonding motifs. In addition to the classical B 2 X 4 L 2 diborane(4) bis‐adducts, certain more sterically demanding carbene ligands induce a halide displacement which led to the first halide‐bridged monocationic diboron species, [B 2 X 3 L 2 ]A (A=BCl 4 , Br, I). Furthermore, low‐temperature 1:1 reactions of B 2 Cl 4 with sterically demanding N‐heterocyclic carbenes led to the formation of kinetically unstable mono‐adducts, one of which was structurally characterized. A comparison of the NMR spectra and structural data of new and literature‐known bis‐adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed.