The solution structure and the aggregation behavior of (E)-2-lithio-l-(2-lithiophenyl)-l-phenylpent-l-ene (1) and (Z)-2-lithio-l-(24ithiophenyl)ethene (2) were investigated by one-and two-dimensional 'H-, I3C-, and 6Li-NMR spectroscopy. In Et@, both systems form diniers which show homonuclear scalar 6Li,6Li spin-spin coupling. In the case of 2, extensive 6Li,'H coupling is observed. In tetrahydrofuran and in the presence of 2 mol of N,N,N',N'-tetramethylethylenediamine (tmeda), the dimeric structure of 1 coexists with a monomer. The activation parameters for intra-aggregate exchange in the diniers of 1 and 2 (1 (Et,O): A H # = 62.6 h 13.9 kJ/mol, AS # = 5.8 * 14.0 J/mol K, A G '(263) = 61.1 kJ/mol; 2 (dimethoxyethane): A H # = 36.9 h 6.5 kJ/mol, AS # = -61 h 25 J/mol K, AG # (263) = 54.0 kJ/mol) and the thermodynamic parameters for the dimer-monomer equilibrium for 1 (AHa = 26.7 f 5.5 kJ/mol, AS" = 63 * 27 J/mol K), where the monomer is favored at low temperature, were determined by dynamic NMR studies. I) 'NMR Spectroscopy of Organolithium Compounds', Part XVIII; Part XVII: [I] ') In the meanlime, 2 was also prepared by lithiation of (Z)-2-]ithiostyrene with BuLi/N,N,N',N'-tetramethylethylenedianiine (ttneda) [2 I].
') h = non-deuteriated ligand; 1 = deuteriated ligand