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A Quest for Ligand‐Unsupported Li + –π Interactions in Mono‐, Di‐, and Tritopic Lithium Arylborates
Author(s) -
Franz Daniel,
Haghiri Ilkhechi Alireza,
Bolte Michael,
Lerner HansWolfram,
Wagner Matthias
Publication year - 2011
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.201100824
Subject(s) - chemistry , aryl , crystal structure , crystallography , lithium (medication) , lithium atom , ligand (biochemistry) , hydride , dimethoxyethane , stereochemistry , solvent , medicinal chemistry , ion , metal , organic chemistry , medicine , biochemistry , alkyl , receptor , electrode , ionization , electrolyte , endocrinology
Abstract The lithium salts of selected mono‐, di‐, and tritopic arylborates have been synthesized and their solid‐state structures have been analyzed by X‐ray crystallography with focus on the occurrence of Li + –aryl π interactions. The solvated salts of the monotopic arylborate [Li(thf) 4 ][( p ‐BrC 6 H 4 )BPh 3 ] as well as the ditopic borates [Li(12‐crown‐4) 2 ] 2 [ p ‐C 6 H 4 (BMe 3 ) 2 ] and [Li(tetraglyme)] 2 [ p ‐C 6 H 4 (BPh 3 ) 2 ] exist as solvent‐separated ion pairs in the crystal lattice. The attachment of two moderately coordinating monohydridoborate functionalities on a benzene ring leads to Li + –hydride interactions. In the case of [Li(thf) 3 ] 2 [ p ‐C 6 H 4 {9‐BBN(H)} 2 ] [9‐BBN(H) = 9‐borabicyclo[3.3.1]nonane], this additional attractive force is not sufficient to promote Li + –aryl π interactions, however, the 1,2‐dimethoxyethane (DME) solvate [Li(dme) 2 ] 2 [ p ‐C 6 H 4 {9‐BBN(H)} 2 ] shows a remarkably short contact between the Li + cation and the adjacent phenylene ipso carbon atom [Li–C 2.366(2) Å]. The targeted structural motif ofLi + –arene η 6 coordination was finally observed in the solid‐state structures of the tritopic borates [{Li(12‐crown‐4) 2 } 2 Li(thf)][1,3,5‐C 6 H 3 (BMe 3 ) 3 ] and [{Li(thf) 2 } 2 Li][1,3,5‐C 6 H 3 (BH 3 ) 3 ]. In the latter complex, an extensive network of Li–H–B bonds is observed in addition to the Li + –π interaction.