Mixed aggregation between lithium diisopropylamide and lithium chloride: NMR, solid-state structure and ab initio calculations

William Clegg, James C. Greer, Joseph M. Hayes, Francis S. Mair, Philip M. Nolan, Paul A. O'Neil

Research output: Journal PublicationArticlepeer-review

15 Citations (Scopus)

Abstract

An improved synthesis of (Pr1 2NLi)2LiCl(Me2NCH2CH 2NMe2)2 (1) is presented. The structural characterisation of 1 by single crystal X-ray diffraction (C24H60ClLi3N6, M = 489.1, monoctinic P21/n, a = 9.126(3), b = 17.538(6), c = 20.470(7) Å, β = 98.02(4)°, V= 3244.2(19) Å3, Z=4) revealed a three-runged Li-N, Cl-Li, Li-N ladder molecular structure. Cryoscopy in benzene indicated that 1 remained substantially undissociated in that solvent. Multinuclear variable temperature NMR in toluene revealed fluxionality; a mechanism of fluxion in arene solution involving rupture of an R2N-Li bond followed by pseudorotation of all external ligands around a chloride fulcrum is proposed. Semi-empirical (MNDO) and ab initio (HF/6-31G *) calculational studies of the simplified model (LiNH2)2LiCl gave six-membered ring minimum energy geometries. While coordination of four water molecules to the model resulted in only modest changes to the six-membered ring structure at MNDO level, coordination of four dimethyl ether molecules led to a preference for the three-runged ladder structure as predicted by SCF calculations using a 6-31G * basis.

Original languageEnglish
Pages (from-to)1-9
Number of pages9
JournalInorganica Chimica Acta
Volume258
Issue number1
DOIs
Publication statusPublished - 15 May 1997
Externally publishedYes

Keywords

  • Crystal structures
  • Isopropylamide complexes
  • Lithium complexes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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