Premium
[{(MeLi) 4 (dem) 1.5 } ∞ ] and [(thf) 3 Li 3 Me{(N t Bu) 3 S}]—How to Reduce Aggregation of Parent Methyllithium
Author(s) -
Walfort Bernhard,
Lameyer Lutz,
Weiss Wilfried,
HerbstIrmer Regine,
Bertermann Rüdiger,
Rocha João,
Stalke Dietmar
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010401)7:7<1417::aid-chem1417>3.0.co;2-q
Subject(s) - methyllithium , diethyl ether , chemistry , ether , dimer , adduct , denticity , reactivity (psychology) , medicinal chemistry , solubility , stereochemistry , organic chemistry , crystal structure , medicine , alternative medicine , pathology
Organolithium compounds play the leading role among the organometallic reagents in synthesis and in industrial processes. Up to date industrial application of methyllithium is limited because it is only soluble in diethyl ether, which amplifies various hazards in large‐scale processes. However, most reactions require polar solvents like diethyl ether or THF to disassemble parent organolithium oligomers. If classical bidentate donor solvents like TMEDA (TMEDA= N , N , N ′, N ′tetramethyl‐1,2‐ethanediamine) or DME (DME=1,2‐dimethoxyethane) are added to methyllithium, tetrameric units are linked to form polymeric arrays that suffer from reduced reactivity and/or solubility. In this paper we present two different approaches to tune methyllithium aggregation. In [{(MeLi) 4 (dem) 1.5 } ∞ ] ( 1 ; DEM=EtOCH 2 OEt, diethoxymethane) a polymeric architecture is maintained that forms microporous soluble aggregates as a result of the rigid bite of the methylene‐bridged bidentate donor base DEM. Wide channels of 720 pm in diameter in the structure maintain full solubility as they are coated with lipophilic ethyl groups and filled with solvent. In compound 1 the long‐range Li 3 CH 3 ⋅⋅⋅Li interactions found in solid [{(MeLi) 4 } ∞ ] are maintained. A different approach was successful in the disassembly of the tetrameric architecture of [{(MeLi) 4 } ∞ ]. In the reaction of dilithium triazasulfite both the parent [(MeLi) 4 ] tetramer and the [{Li 2 [(N t Bu) 3 S]} 2 ] dimer disintegrate and recombine to give an MeLi monomer stabilized in the adduct complex [(thf) 3 Li 3 Me{(N t Bu) 3 S}] ( 2 ). One side of the Li 3 triangle, often found in organolithium chemistry, is shielded by the tripodal triazasulfite, while the other face is μ 3 ‐capped by the methanide anion. This Li 3 structural motif is also present in organolithium tetramers and hexamers. All single‐crystal structures have been confirmed through solid‐state NMR experiments to be the same as in the bulk powder material.