Alkali metal complexes of silyl-substituted ansa-(Tris)allyl ligands: Metal-, Co-Ligand- and substituent-dependent stereochemistry

Scott A. Sulway, Roman Girshfeld, Sophia A. Solomon, Christopher A. Muryn, Jordi Poater, Miquel Solà, F. Matthias Bickelhaupt, Richard A. Layfield

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    The structures of alkali metal complexes of silyl-substituted ansa-tris(allyl) ligands [RSi(C3H3SiMe3J 3]3- (R = Me, L1; or Ph, L2) are discussed, Triple deprotonation of L1H3 by nBuNa/tmeda affords [L1{Na(tmeda)}3] (4) in which the sodium cations are complexed by ηn-allyl ligands and the silyl substituents adopt [exo,exo][endo,exo]2 stereochemistries in one crystallographically disordered form and [endo,exo]3 in another. Triple deprotonation of L2H3 with nBuLi/tmeda results in the formation of [L2{Li(tmeda)}3] (5), the structure of which features silyl substituents with [exo,exo]2[endo,exo] stereochemistries. The trisodium complex [L2Na{Na(tmeda)} 2]2 (6) consists of a hexa(allylsodium) macrocycle that aggregates as a result of cation-π interactions between the phenyl substituents and the sodium cations. An attempt to prepare the tripotassium complex of L1 resulted in the formation of the bimetallic potassium/lithium, complex [L2{K(OEt2)2} 2KL1(μ4-OtBu)]2 (7), in which the lithium tertbutoxide by-product is incorporated into a hexa(allylpotassium) macrocycle. Triple deprotonation of L1H3 with nBuLi and the terdentate Lewis base pmdeta results in [L1Li(pmdeta)}3] (8), in which the three allyl groups do not μbridge between lithium cations, resulting in an [exo,exo]3 stereochemistry of the silyl substituents, NMR spectroscopic studies reveal complicated solution-phase behaviour for 4, 6 and 7, whereas the solid-state structures of 5 and 8 are preserved in solution. Further insight into the structures and stereochemical preference of the ansa-tris (allyl) ligands in 4 and 5 is provided by detailed density functional theory calculations. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.
    Original languageEnglish
    Pages (from-to)4157-4167
    Number of pages10
    JournalEuropean Journal of Inorganic Chemistry
    Issue number27
    Publication statusPublished - Sept 2009


    • Allyl ligands
    • Lithium
    • Potassium
    • Sodium
    • Stereochemistry


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