Synthesis, structures and reactivity of lanthanoid(II) formamidinates of varying steric bulk
Journal Publication ResearchOnline@JCUAbstract
New reactive, divalent lanthanoid formamidinates [Yb(Form)₂(thf)₂] (Form=[RNCHNR]; R=o-MeC₆H₄ (o-TolForm; 1), 2,6-Me₂C₆H₃ (XylForm; 2), 2,4,6-Me₃C₆H₂ (MesForm; 3), 2,6-Et₂C₆H₃ (EtForm; 4), o-PhC₆H₄ (o-PhPhForm; 5), 2,6-iPr₂C₆H₃ (DippForm; 6), o-HC₆F₄ (TFForm; 7)) and [Eu(DippForm)₂(thf)₂] (8) have been prepared by redox transmetallation/protolysis reactions between an excess of a lanthanoid metal, Hg(C₆F5)₂ and the corresponding formamidine (HForm). X-ray crystal structures of 2–6 and 8 show them to be monomeric with six-coordinate lanthanoid atoms, chelating N,N′-Form ligands and cis-thf donors. However, [Yb(TFForm)₂(thf)₂] (7) crystallizes from THF as [Yb(TFForm)₂(thf)₃] (7 a), in which ytterbium is seven coordinate and the thf ligands are "pseudo-meridional". Representative complexes undergo C[BOND]X (X=F, Cl, Br) activation reactions with perfluorodecalin, hexachloroethane or 1,2-dichloroethane, and 1-bromo-2,3,4,5-tetrafluorobenzene, giving [Yb(EtForm)₂F]₂ (9), [Yb(o-PhPhForm)₂F]₂ (10), [Yb(o-PhPhForm)₂Cl(thf)₂] (11), [Yb(DippForm)₂Cl(thf)] (12) and [Yb(DippForm)₂Br(thf)] (16). X-ray crystallography has shown 9 to be a six-coordinate, fluoride-bridged dimer, 12 and 16 to be six-coordinate monomers with the halide and thf ligands cis to each other, and 11 to have a seven-coordinate Yb atom with "pseudo-meridional" unidentate ligands and thf donors cis to each other. The analogous terbium compound [Tb(DippForm)₂Cl(thf)₂] (13), prepared by metathesis, has a similar structure to 11. C[BOND]Br activation also accompanies the redox transmetallation/protolysis reactions between La, Nd or Yb metals, Hg(2-BrC₆F₄)₂, and HDippForm, yielding [Ln(DippForm)₂Br(thf)] complexes (Ln=La (14), Nd (15), Yb (16)).
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19
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1521-3765
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4
Pages Count
11
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Wiley-Blackwell
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DOI
10.1002/chem.201202861