Bestimmung der Struktur von Phenylaethinyllithium in Loesung mittels Tieftemperatur-NMR-Spektroskopie

Article abstract of DOI:10.1002/hlca.19830660737

The dimeric and tetrameric 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-(6Li)-<1-13C>-2-phenylethyne in the presence or absence of N,N,N',N'-tetramethylpolymethylenediamines show a pentuplett 13C-NMR signal <δ=140 ppm, J(C,Li)=8.2 Hz> from the labelled C-atom at low temperatures (-95 to -110 deg C).This proves the dimeric structure.When (6Li)BuLi is added, a mixed dimer <(C6H5C<*>CLi)(C4H9Li)> is formed <δ=142 ppm, J(C,Li)=7.8 Hz>.This is converted to a mixed tetramer <(C6H5C<*>CLi)(C4H9Li)3> upon addition of larger amounts of (6Li)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.