Issue 16, 2015

Solid state and solution studies of lithium tris(n-butyl)magnesiates stabilised by Lewis donors

Abstract

Several Lewis base adducts of the synthetically important lithium tris(n-butyl)magnesiate LiMg(nBu)3 have been prepared and structurally characterised. The complexes were prepared by a co-complexation approach i.e., by combining the monometallic nBuLi and nBu2Mg reagents in hydrocarbon solution before adding a molar equivalent of a donor molecule (a bidentate amine, tridentate amine or cyclic ether). The lithium magnesiates all adopt variants of the “Weiss motif” structure, i.e., contacted ion pair dimers with a linear arrangement and metals connected by butyl anions, where tetrahedral magnesium ions are in the central positions and the lithiums occupy the outer region, solvated by a neutral Lewis donor [(donor)Li(μ-nBu)2Mg(μ-nBu)2Mg(μ-nBu)2Li(donor)]. When TMPDA, PMDETA or (R,R)-TMCDA [TMPDA = N,N,NN′-tetramethylpropanediamine; PMDETA = N,N,N′,N′′,N′′-pentamethyldiethylenetriamine; and (R,R)-TMCDA = (R,R)-N,N,N′,N′-tetramethylcyclohexane-1,2-diamine], are employed, dimeric tetranuclear lithium magnesiates are produced. Due to the tridentate nature of the ligand, the PMDETA-containing structure (2) has an unusual ‘open’-motif. When TMEDA (TMEDA = N,N,N′,N′-tetramethylethylenediamine) is employed, a n-butoxide-containing complex [(TMEDA)Li(μ-nBu)(μ-OnBu)Mg2(nBu)2(μ-nBu)(μ-OnBu)Li(donor)] has been serendipitously prepared and adopts a ladder conformation which is commonly observed in lithium amide chemistry. This complex has also been prepared using a rational methodology. When 1,4-dioxane is employed, the donor stitches together a polymeric array of tetranuclear dimeric units (6). The hydrocarbon solution structures of the compounds have been characterised by 1H, 7Li, 13C NMR spectroscopy; 2 has been studied by variable temperature and DOSY NMR.

Graphical abstract: Solid state and solution studies of lithium tris(n-butyl)magnesiates stabilised by Lewis donors

Supplementary files

Article information

Article type
Paper
Submitted
30 Jan 2015
Accepted
09 Mar 2015
First published
09 Mar 2015
This article is Open Access
Creative Commons BY license

Dalton Trans., 2015,44, 7258-7267

Solid state and solution studies of lithium tris(n-butyl)magnesiates stabilised by Lewis donors

S. Zaragoza-Calero, J. Francos, A. R. Kennedy and C. T. O'Hara, Dalton Trans., 2015, 44, 7258 DOI: 10.1039/C5DT00435G

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements