American Chemical Society
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Pinwheel-Shaped Heterobimetallic Lanthanide Alkali Metal Binaphtholates:  Ionic Size Matters!

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posted on 2000-11-14, 00:00 authored by Helen C. Aspinall, Jamie F. Bickley, Jennifer L. M. Dwyer, Nicholas Greeves, Richard V. Kelly, Alexander Steiner
Anhydrous alkali metal lanthanide binaphtholates M3[Ln(binol)3] (M = Li, Na; Ln = lanthanide or yttrium; H2binol = binaphthol) are prepared by reaction of [Ln{N(SiMe3)2}3] with 3 equiv of MHbinol. Reaction of [Ln{N(SiMe3)2}3] (Ln = Y or Yb) with 3 equiv of rac-LiHbinol gives a racemic mixture of RRS- and SSR-Li3[Ln(binol)3] 2 as the only product. In contrast, reaction of [Ln{N(SiMe3)2}3] with 3 equiv of rac-NaHbinol gives a racemic mixture of RRR- and SSS-Na3[Ln(binol)3] when Ln = Y. When Ln = Yb, a 3:1 mixture of RRR-/SSS- and RRS-/SSR-Na3[Ln(binol)3] is formed. Complexes have been characterized in solution by NMR spectroscopy. The 3-proton of the unique binol ligand in RRS- and SSR-Li3[Y(binol)3] is shifted upfield by interaction with the π-system of a neighboring naphthyl ring. Analysis of paramagnetically induced 1H NMR shifts of Yb complexes shows them to be entirely dipolar in origin. X-ray crystal structures have been determined for the following compounds:  rac-[Li(THF)2]3[Y(binol)3]·THF, 2a; rac-[Na(THF)2]3[Y(binol)3], 3; [Li(OEt2)]3[Eu(S-binol)3]·[Li(OEt2)]3[Eu(S-binol)3(H2O)]·2Et2O, 4; [Li(THF)2]2[Li(OEt2)][Yb(S-binol)3]·THF, 5; [Na(THF)2]3[Yb(S-binol)3], 6; [Na(THF)2]3[La(S-binol)3(H2O)], 7.