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Commercially available stock solutions of organolithium reagents are well‐implemented tools in organic and organometallic chemistry. However, such solutions are inherently contaminated with lithium halide salts, which can complicate certain synthesis protocols and purification processes. Here, we report the isolation of chloride‐free methyllithium employing K[N(SiMe3)2] as a halide‐trapping reagent. The influence of distinct LiCl contaminations on the 7Li‐NMR chemical shift is examined and their quantification demonstrated. The structural parameters of new chloride‐free monomeric methyllithium complex [(Me3TACN)LiCH3], ligated by an azacrown ether, are assessed by comparison with a halide‐contaminated variant and monomeric lithium chloride [(Me3TACN)LiCl], further emphasizing the effect of halide impurities. [ABSTRACT FROM AUTHOR]

Kommerziell erhältliche Stammlösungen von Organolithiumverbindungen sind vielfach eingesetzte Reagenzien in der Organischen und Metallorganischen Chemie. Solche Lösungen sind jedoch von "Natur aus" mit Lithiumhalogenidsalzen verunreinigt, die viele Syntheseprotokolle und Aufreinigungsprozesse erheblich einschränken. In dieser Arbeit beschreiben wir die Isolierung von chloridfreiem Methyllithium mithilfe von K[N(SiMe3)2] als Halogenidfällungsreagenz. Der Einfluss von definierten LiCl‐Verunreinigungen auf die 7Li‐NMR chemische Verschiebung wurde systematisch untersucht und quantifiziert. Die strukturellen Parameter des neuen chloridfreien Methyllithiumkomplexes [(Me3TACN)LiCH3] wurden mit der halogenidverunreinigten Variante und monomerem Lithiumchlorid [(Me3TACN)LiCl] verglichen. [ABSTRACT FROM AUTHOR]

The yttrium gallabenzene complex [(1-Me-3,5-tBu 2 -C 5 H 3 Ga)(μ-Me)Y(2,4-dtbp)] is accessible from Y(GaMe 4 ) 3 and K(2,4-dtbp) via a tandem salt metathesis/methane elimination (2,4-dtbp=2,4-di-tert-butyl-pentadienyl). The pentadienyl ligand in [(1-Me-3,5-tBu 2 -C 5 H 3 E)(μ-Me)Y(2,4-dtbp)] (E=Al, Ga) is easily displaced by salt metathesis with KC 5 Me 5 and KTp Me,Me (Tp Me,Me =tris(pyrazolyl-Me 2 -3,5)borato) affording [(1-Me-3,5-tBu 2 -C 5 H 3 E)(μ-Me)Y(Tp Me,Me )] and [(1-Me-3,5-tBu 2 -C 5 H 3 E)(μ-Me)Y(C 5 Me 5 )]. The yttrium center in [(1-Me-3,5-tBu 2 -C 5 H 3 E)(μ-Me)Y(2,4-dtbp)] readily forms adducts with neutral Lewis bases like 4-DMAP (4-dimethylaminopyridine), PMe 3 , DMPE (1,2-bis(dimethylphosphino)ethane), and DME (1,2-dimethoxyethane). In stark contrast, addition of TMEDA (N,N,N',N'-tetramethylethylenediamine) results in methyl/pentadienyl exchange between aluminum and yttrium resulting in [(1-(2,4-dtbp)-1-Me-3,5-tBu 2 -C 5 H 3 Al)Y(Me)(tmeda)]. The bonding features of the newly synthesized complexes are analyzed by single-crystal X-ray diffraction (SCXRD) and heteronuclear ( 89 Y, 31 P) NMR spectroscopy., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

En route to putative rare-earth-metal alkylidene complex Li[Lu(CH 2 SiMe 3 ) 2 (CHSiMe 3 )], according to Schumann's original protocol, the reaction of YCl 3 with LiCH 2 SiMe 3 in a mixture of diethyl ether and n -pentane afforded a neosilyl ate complex of composition Li 3 Y(CH 2 SiMe 3 ) 6 . Tetrametallic complex Li 3 Y(CH 2 SiMe 3 ) 6 shows an unprecedented structural motif in the solid state and was further characterized by heteronuclear 1 H/ 13 C/ 7 Li/ 29 Si/ 89 Y, as well as VT NMR and DRIFT spectroscopies. Analysis of the thermolysis product via heteronuclear NMR spectroscopy and its reactivity towards benzophenone gave strong evidence for an alkylidene formation upon decomposition. Application of a similar protocol for the smallest rare-earth-metal scandium led to the isolation of ate complex [Li(thf) 4 ][LiSc 2 (CH 2 SiMe 3 ) 8 ] as the preferred crystallized product. Here, the reaction of adduct ScCl 3 (thf) 3 and LiCH 2 SiMe 3 was performed in Et 2 O/ n -hexane, in the absence of additional THF. The reaction of LaCl 3 (thf) with 3 equiv. of LiCH 2 SiMe 3 in THF/Et 2 O at -40 °C yielded the ate complex [Li(thf) 4 ][La(CH 2 SiMe 3 ) 4 (thf)], which is the first of its kind.