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Zur Struktur von 1‐Azapentadienyllithium‐Verbindungen
Author(s) -
Wolf Gerhard,
Würthwein ErnstUlrich
Publication year - 1991
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19911240432
Subject(s) - chemistry , mndo , lithium diisopropylamide , steric effects , deprotonation , conformational isomerism , stereochemistry , nuclear magnetic resonance spectroscopy , crystallography , alkyl , ab initio , computational chemistry , molecule , organic chemistry , ion
On the Structures of 1‐Azapentadienyllithium Compounds 1‐Azapentadienyllithium compounds 2–6 have been prepared by deprotonation of the α,β‐unsaturated imines 1 with lithium diisopropylamide. Their structures in THF solution at various temperatures have been studied by 1 H‐ and 13 C‐NMR spectroscopy. All N ‐alkyl‐substituted derivatives 2 – 5 adopt W conformations of the 1‐azapentadienyl unit. The N‐ tert ‐butylsubstituted compound 2 shows an ( E )‐configurated NC‐ bond, whereas compounds 3 – 5 prefer (Z)‐NC configurations. According to NOE experiments, the triphenyl system 6 has a U‐shape structure, probably because of steric interactions of the phenyl substituents. 13 C‐shifts of the 1‐azapentadienyl carbon atoms are discussed in terms of HOMO coefficients. The experimental structural results are compared with theoretical data obtained by MNDO and ab initio calculations for the corresponding anions. MNDO results are also given for monomeric 1‐azapentadienyllithium conformers 11.