Solid state and solution studies of lithium tris(n-butyl)magnesiates stabilised by Lewis donors12. Issue 16 (20th March 2015)

• Record Type: Journal Article
• Authors: Zaragoza-Calero, Silvia; Francos, Javier; Kennedy, Alan R.; O'Hara, Charles T.
• Is Part Of: Dalton transactions. Volume 44:Issue 16(2015)
• Page Start: 7258
• Page End: 7267
• Publication Date: 2015-03-20
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c5dt00435g
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Donor complexes of the synthetically important lithium magnesiate LiMg( n Bu)3 have been prepared and characterised. Abstract : Several Lewis base adducts of the synthetically important lithium tris( n -butyl)magnesiate LiMg( n Bu)3 have been prepared and structurally characterised. The complexes were prepared by a co-complexation approach i.e., by combining the monometallic n BuLi and n Bu2 Mg 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- n Bu)2 Mg(μ- n Bu)2 Mg(μ- n Bu)2 Li(donor)]. When TMPDA, PMDETA or ( R, R )-TMCDA [TMPDA = N, N, N ′ N ′-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- n Bu)(μ-O n Bu)Mg2 ( n Bu)2 (μ- n Bu)(μ-O n Bu)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 1 H, 7 Li, 13 C NMR spectroscopy;2 has been studied by variable temperature and DOSY NMR.