NMR spectroscopic study of the adduct formation and reactivity of homoleptic rare earth amides with alkali metal benzyl compounds, and the crystal structures of [Li(TMEDA)2][Nd{N(SiMe3)2}3(CH2Ph)] and [{Li(TMP)}2{Li(Ph)}]2.

Rachor, Simon G. and Cleaves, Peter A. and Robertson, Stuart D. and Mansell, Stephen M. (2018) NMR spectroscopic study of the adduct formation and reactivity of homoleptic rare earth amides with alkali metal benzyl compounds, and the crystal structures of [Li(TMEDA)2][Nd{N(SiMe3)2}3(CH2Ph)] and [{Li(TMP)}2{Li(Ph)}]2. Journal of Organometallic Chemistry, 857. pp. 101-109. ISSN 0022-328X (https://doi.org/10.1016/j.jorganchem.2017.10.022)

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Abstract

An NMR spectroscopic study has been conducted into the reactivity of alkali metal benzyls [M(CH2Ph)], (M = Li, Na, K) with lanthanide tris(amide) complexes [Ln(N")3] (Ln = Y, Ce, Nd; N" = N(SiMe3)2) and [Ce(TMP)3] (TMP = 2,2,6,6-tetramethylpiperidide). It was found that for [Ln(N")3], benzyl adducts [M][Ln(N")3(CH2Ph)] were initially formed, and the molecular structure for M = Li(TMEDA)2 and Ln = Nd was determined revealing a distorted tetrahedral [Nd(N")3(CH2Ph)] anion. In all cases, these adduct complexes were unstable, intramolecularly deprotonating a methyl arm of a N" ligand via benzyl basicity and eliminating toluene to prepare cyclometallated complexes of the form [M][Ln(N")2{κ2-CH2Si(Me)2N(SiMe3)}]. In parallel studies, reactions of [Li(Ph)] with [Ln(N")3] (Ln = Ce, Nd) afforded [Li(N")], whilst for (Ln = Y) adduct formation was observed. [Ce(TMP)3] did not generate any characterisable bimetallic adducts. The reaction of [Li(Ph)] with [Li(TMP)] afforded the hexanuclear [{Li(TMP)}2{Li(μ-Ph)}]2, which features lithium in three different coordination environments.

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