Schlenk's Legacy—Methyllithium Put under Close Scrutiny

Abstract

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(SiMe 3 ) 2 ] as a halide-trapping reagent. The influence of distinct LiCl contaminations on the 7 Li-NMR chemical shift is examined and their quantification demonstrated. The structural parameters of new chloride-free monomeric methyllithium complex [(Me 3 TACN)LiCH 3 ], ligated by an azacrown ether, are assessed by comparison with a halide-contaminated variant and monomeric lithium chloride [(Me 3 TACN)LiCl], further emphasizing the effect of halide impurities.

The quest for organo-alkali metal monomers: unscrambling the structure–reactivity relationship

“…The synthesis of 4 is a part of the Anwander group's effort to pursue high-purity MeLi. 64 While commercial solutions of MeLi are contaminated with lithium chloride, the authors (Anwander and co-workers) designed a route to achieve high-purity MeLi by utilising potassium bis(trimethylsilyl)amide (KN(SiMe 3 ) 2 , i.e. , KHMDS) as a halide-trapping reagent.…”

“…The synthesis of 4 is a part of the Anwander group's effort to pursue high-purity MeLi. 64 While commercial solutions of MeLi are contaminated with lithium chloride, the authors (Anwander and co-workers) designed a route to achieve highpurity MeLi by utilising potassium bis(trimethylsilyl)amide (KN(SiMe 3 ) 2 , i.e., KHMDS) as a halide-trapping reagent. Both the pure and commercial MeLi solutions reacted with Me 3 TACN to form 4, but the compound from the commercial solution resulted in a single-crystal structure with a chloride site occupancy of 9% (at the C10 position in Fig.…”

In Situ Generation of Magnesium‐ and Calcium‐Based Grignard Reagents for Amide Synthesis

“…In alkali metal amide chemistry the analogy to Hauser bases ([A(NR 2 )] ⋅ [AX]) has not been investigated yet in detail. Recent findings in the reactivity of methyllithium shows an increase with (sub‐stoichiometric) amounts of lithium halide [31] . The mixture of alkali metal amides and alkaline‐earth metal bis(amides) leads to formation of so‐called metalates.…”

“…Recent findings in the reactivity of methyllithium shows an increase with (sub-stoichiometric) amounts of lithium halide. [31] The mixture of alkali metal amides and alkaline-earth metal bis(amides) leads to formation of so-called metalates. The generation of these compounds is based on different electronegativity values of the metals.…”

Putting on the Crown: Synthesis and Reactivity of Trimethyltitanium

“…5−10% LiCl, a slight excess of MeLi was used. 12 Performing the synthesis of 1 at low temperature is crucial for two main reasons: first and foremost to prevent the transfer of the azacrown from the titanium center to a lithium center in LiCl or MeLi and second to prevent the target complex from decomposition (via displacement of Me 3 TACN and concomitant methane evolution). Once the methyl complex 1 has been isolated, it is stable at ambient temperature for hours.…”