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Bestimmung der Struktur von Phenyläthinyllithium in Lösung mittels Tieftemperatur‐NMR‐Spektroskopie
Author(s) -
Hässig Robert,
Seebach Dieter
Publication year - 1983
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19830660737
Subject(s) - chemistry , tetramer , dimer , tetrahydrofuran , multiplicity (mathematics) , crystallography , solid state , nuclear magnetic resonance spectroscopy , stereochemistry , organic chemistry , mathematical analysis , mathematics , solvent , enzyme
The dimeric and tetrametic structures of complexes of phenylethinyllithium, as recently discovered by X‐ray analysis in the solid state, were also found to be present in solution. Tetrahydrofuran solutions of 1‐( 6 Li)‐[1‐ 13 C]‐2‐phenylethyne in the presence or absence of N , N , N ′, N ′‐tetramethylpolymethylenediamines show a pentuplett 13 C‐NMR signal [δ=140 ppm, J (C,Li)=8.2 Hz] from the labelled C‐atom at low temperatures (−95 to −110°). This proves the dimeric structure. When ( 6 Li)BuLi is added, a mixed dimer [(C 6 H 5 CCLi)(C 4 H 9 Li)] is formed [δ=142 ppm, J (C,Li) = 7.8 Hz]. This is converted to a mixed tetramer [(C 6 H 5 CCLi)(C 4 H 9 Li) 3 ] upon addition of larger amounts of ( 6 Li)BuLi, as concluded from a signal at δ = 133.5 ppm, J (C,Li) = 5.6 Hz. The multiplicity of this signal suggests that a static tetramer is present, in which the C‐atoms couple only with three next Li‐neighbors.