[{(MeLi)(4)(dem)(1.5)}(infinity)] and [(thf)(3)Li3Me{(NtBu)(3)S}] - How toreduce aggregation of parent methyllithium

Organolithium compounds play the leading role among the organometallic reag ents in synthesis and in industrial processes. Up to date industrial applic ation of methyllithium is limited because it is only soluble in diethyl eth er, which amplifies various hazards in large-scale processes. However, most reactions require polar solvents like diethyl ether or TI-IF to disassembl e parent organolithium oligomers. If classical bidentate donor solvents lik e TMEDA (TMEDA = N,N,N,N'tetramethyl- 1,2-ethanediamine) or DME (DME=1,2-di methoxyethane) are added to methyllithium, tetrameric units are linked to f orm polymeric arrays that suffer from reduced reactivity and/or solubility. In this paper we present two different approaches to tune methyllithium ag gregation. In [((MeLi)(4)(dem)(1.5)}(infinity)] (1; DEM - EtOCH2OEt, dietho xymethane) a polymeric architecture is maintained that forms microporous so luble aggregates as a result of the rigid bite of the methylene-bridged bid entate donor base DEM. Wide channels of 720 pm in diameter in the structure maintain full solubility as they are coated with lipophilic ethyl groups a nd filled with solvent. In compound 1 the long-range Li3CH3. . . Li interac tions found in solid [{(MeLi)(4)}(infinity)] are maintained. A different ap proach was successful in the disassembly of the tetrameric architecture of [{(MeLi)(4)}(infinity)]. In the reaction of dilithium triazasulfite both th e parent [(MeLi)(4)] tetramer and the [(Li-2[(NtBu)(3)S]}(2)] dimer disinte grate and recombine to give an MeLi monomer stabilized in the adduct comple x [(thf)(3)Li3Me{(NtBu)(3)S}] (2). One side of the Lit triangle, often foun d in organolithium chemistry, is shielded by the tripodal triazasulfite, wh ile the other face is mu (3)-capped by the methanide anion. This Li-3 struc tural motif is also present in organolithium tetramers and hexamers. All si ngle-crystal structures have been confirmed through solid-state NMR experim ents to be the same as in the bulk powder material.