Tetramers aryllithiums

PrLi)6], " and unsolvated lithium aryls are tetramers. cx-Ethoxyvinyllithium [CH2=C(OEt)Li] shows a polymeric structure with tetrameric subunits.Ami-nomethyl aryllithium reagents have been shown to be chelated and dimeric in solvents such as... 

A distorted butterfly CU4 unit with Cu-Cu distances less than 240 pm is found for (4-methyl-2-cupriobenzyl)dimethylamine tetramers . Copper aryl complexes stabilized by the amine nitrogen lone pair are prepared from CuBr and the appropriate aryllithium reagent in ether in 40-60% yields... 

Yet another variety of self-association via r-interactions was discovered in the solid-state structure of imsolvated 2,4,6-triisopropylphenyllithium. In the crystal this compound forms the tetramer [Li(2,4,6-Pr 3C6H2)]4, 63. This structure has not been observed for other aryllithium species. It consists of an almost planar arrangement of four lithium atoms, each n-bonded to just one phenyl ring (average Li-C distance 2.12 A). In addition, each Li interacts with the 7t-electron system of a... 

There are also tetramer units (EtLi) in crystalline ethyllithium, although they associate in linear fashion rather than in three dimensions. These tetrameric clusters are retained in complexes of alkyl and aryllithiums with donor molecules. 

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