Preparation of Low‐Halide Methyllithium

Lusch, Michael J.; Phillips, William V.; Sieloff, Ronald F.; Nomura, Glenn S.; House, Herbert O.

doi:10.1002/0471264180.os062.13

Cited by 9 publications

(11 citation statements)

References 4 publications

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“…Regardless of whether MeLi is prepared from chloromethane (MeCl) and lithium metal in a direct synthesis as described by Ziegler and Colonius or commercially available "low-halide" solutions in Et 2 O were used, these reagents incorporate up to 5−10 mol% of halide, mainly chloride. 53,54 If treated with a soluble calcium precursor in Et 2 O, the chloride impurities will mostly co-precipitate as inseparable calcium or lithium chloride species, producing contaminated [CaMe 2 ] n (1 con , see Supporting Information). This problem may be solved by employing "halide-free" MeLi, but unfortunately all methods known for the preparation of halide-free MeLi require highly toxic dimethylmercury (Scheme 1, I and II).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Dimethylcalcium

2018

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The salt metathesis reaction between homoleptic calcium bis(trimethylsilyl)amide [Ca{N(SiMe)}] and "halide-free" methyllithium allowed for the isolation of X-ray-amorphous dimethylcalcium [CaMe] in good yields and purities. The formation of [CaMe] was proven by microanalysis and NMR/FTIR spectroscopic methods as well as a series of derivatization reactions. Despite slowly decomposing thf, [CaMe] could be crystallized from chilled thf solutions as the heptametallic adduct [(thf)CaMe]. Reaction of [CaMe] with CaI in thf led to the dimeric complex [(thf)Ca(Me)(I)], whereas in tetrahydropyran (thp) the trinuclear complex [(thp)Ca(Me)(I)] was obtained, both representing the first crystallographically characterized heavy-Grignard compounds with methyl groups as the hydrocarbyl ligand. While protonolysis of [CaMe] with the superbulky proligand HTp in nonpolar solvents gave homoleptic (Tp)Ca, reaction in donor solvents (thf, thp) afforded the monomeric complexes [(Tp)Ca(Me)(thf)] and [(Tp)Ca(Me)(thp)], which are the first examples bearing terminal Ca-CH functionalities. Grignard-type nucleophilic methyl-group transfer to hexamethylacetone gave access to the dimeric alkoxide complexes [(thf)Ca(OCtBuMe)] and [(tBuCO)Ca(μ-OCtBuMe)Ca(OCtBuMe)]. Finally, addition of the Lewis acid GaMe to [CaMe] led to the corresponding tetramethylgallate compound [Ca(GaMe)].

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Section: ■ Results and Discussionmentioning

confidence: 99%

Dimethylcalcium

2018

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“…C 6 H 5 Li and 4-CH 3 C 6 H 4 Li were prepared according to reference [21]. Solvents were dried by standard methods and kept over molecular sieves.…”

Section: Methodsmentioning

confidence: 99%

Homoleptic Organometallic Anions of Ti, Zr, Hf, and Nb

El‐Kurdi

Seppelt

2011

Chemistry A European J

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Reactions of C(6)H(5)Li and 4-CH(3)C(6)H(4)Li with halides of Ti, Ir, Hf, and Nb lead to the formation of homoleptic organometallic anions of these metals. Owing to their thermal instability and their sensitivity towards H(2) O and O(2) , these compounds are characterized by single-crystal structure determinations at low temperature, whereas other physical data could only be obtained occasionally. Three pentacoordinate complex anions [Ti(C(6)H(5))(5)](-), [Ti(4-CH(3)C(6)H(4))(5)](-), and [Zr(C(6)H(5))(5)](-) have square-pyramidal structures that display only slight deviations from the ideal geometry, in contrast to the already known structures of [Ti(CH(5))(5)](-). The hexacoordinate complex anions [Zr(C(6)H(5))(6)](2-), [Zr(4-CH(3)C(6)H(4))(6)](2-), [Nb(C(6)H(5))(6)](2-), and [Nb(4-CH(3)C(6)H(4))(6)](2-) all have trigonal-prismatic structures, in accord with the known hexamethyl complex dianions. In contrast, the hexacoordinate complex anion [Hf(C(6)H(5))(6)](2)(-) has an octahedral or close to octahedral structure, in contrast to the known trigonal-prismatic structures of [Ta(C(6)H(5))(6)](-) and [Ta(4-CH(3)C(6)H(4))(6) (-). A qualitative explanation for this structural variability is given.

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“…In the synthesis of 1 , the appearance of 2 very likely results from small amounts of LiCl present in solutions of methyllithium in diethyl ether. , Measurably different 1 H and 19 F NMR spectra allow identification and quantification of trace amounts of 2 in solutions of 1 .…”

Section: Dicopper Alkyl Complexesmentioning

confidence: 99%

Dicopper Alkyl Complexes: Synthesis, Structure, and Unexpected Persistence

et al. 2018

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Cationic μ-alkyl dicopper complexes [Cu2(μ-η 1 :η 1 -R)DPFN]NTf2 (R = CH3, CH2CH3, CH2C(CH3)3; DPFN = 2,7-bis(fluorodi(2-pyridyl)-methyl)-1,8-naphthyridine; NTf2 -= N(SO2CF3)2 -) were synthesized by treatment of an acetonitrile-bridged dicopper complex [Cu2(μ-η 1 :η 1 -NCCH3)DPFN](NTf2)2 with LiR or MgR2. Structural characterization by X-ray crystallography and NMR spectroscopy revealed that the alkyl ligands symmetrically bridge the two copper centers, and the complexes persist in room temperature solution. Notably, the μ-methyl complex showed less than 20% decomposition after 34 days in room temperature THF solution. Treatment of the μ-methyl complex with acids allows installation of a range of monoanionic bridging ligands. However, surprisingly insertion into the dicopper-carbon bond was not observed upon addition of a variety of reagents, suggesting that these complexes exhibit a fundamentally new reactivity profile for alkylcopper species. Electrochemical characterization revealed oxidation-reduction events that evidence putative mixed-valence dicopper alkyl complexes. Computational studies suggest that the dicopper-carbon bonds are highly covalent, possibly explaining their remarkable stability.

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Preparation of Low‐Halide Methyllithium

Abstract: Preparation of Low‐Halide Methyllithium reactant: methyl chloride product: methyllithium unknown: 1.0 mL of freshly distilled 1,2‐dibromoethane

Cited by 9 publications

References 4 publications

Dimethylcalcium

Dimethylcalcium

Homoleptic Organometallic Anions of Ti, Zr, Hf, and Nb

Dicopper Alkyl Complexes: Synthesis, Structure, and Unexpected Persistence

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