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Issue 35, 2016
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Synthesis and structural diversity of trivalent rare-earth metal diisopropylamide complexes

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Abstract

A series of rare-earth metal diisopropylamide complexes has been obtained via salt metathesis employing LnCl3(THF)x and lithium (LDA) or sodium diisopropylamide (NDA) in n-hexane. Reactions with AM : Ln ratios ≥3 gave ate complexes (AM)Ln(NiPr2)4(THF)n (n = 1, 2; Ln = Sc, Y, La, Lu; AM = Li, Na) in good yields. For smaller rare-earth metal centres such as scandium and lutetium, a Li : Ln ratio = 2.5 accomplished ate-free tris(amido) complexes Ln(NiPr2)3(THF). The chloro-bridged dimeric derivatives [Ln(NiPr2)2(μ-Cl)(THF)]2 (Ln = Sc, Y, La, Lu) could be obtained in high yields for Li : Ln = 1.6–2. The product resulting from the Li : La = 1 : 1.6 reaction revealed a crystal structure containing two different molecules in the crystal lattice, [La(NiPr2)2(THF)(μ-Cl)]2·La(NiPr2)3(THF)2. Recrystallization of the chloro-bridged dimers led to the formation of the monomeric species Ln(NiPr2)2Cl(THF)2 (Ln = Sc, Lu) and La(NiPr2)3(THF)2. The reaction of YCl3 and LDA with Li : Y = 2 in the absence of THF gave a bimetallic ate complex LiY(NiPr2)4 with a chain-like structure. For scandium, the equimolar reactions with LDA or NDA yielded crystals of tetrametallic mono(amido) species, {[Sc(NiPr2)Cl2(THF)]2(LiCl)}2 and [Sc(NiPr2)Cl2(THF)]4, respectively. Depending on the Ln(III) size, AM, and presence of a donor solvent, ate complexes (AM)Ln(NiPr2)4(THF)n show distinct dynamic behaviour as revealed by variable temperature NMR spectroscopy. The presence of weak Ln⋯CH(iPr) β-agostic interactions, as indicated by Ln–N–C angles <105°, is corroborated by DFT calculations and NBO analysis.

Graphical abstract: Synthesis and structural diversity of trivalent rare-earth metal diisopropylamide complexes

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Publication details

The article was received on 22 Apr 2016, accepted on 08 Jul 2016 and first published on 08 Jul 2016


Article type: Paper
DOI: 10.1039/C6DT01568A
Citation: Dalton Trans., 2016,45, 13750-13765
  • Open access: Creative Commons BY-NC license
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    Synthesis and structural diversity of trivalent rare-earth metal diisopropylamide complexes

    T. Spallek, O. Heß, M. Meermann-Zimmermann, C. Meermann, M. G. Klimpel, F. Estler, D. Schneider, W. Scherer, M. Tafipolsky, K. W. Törnroos, C. Maichle-Mössmer, P. Sirsch and R. Anwander, Dalton Trans., 2016, 45, 13750
    DOI: 10.1039/C6DT01568A

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