SOLUTION-STRUCTURE AND AGGREGATION BEHAVIOR OF 2 DILITHIOSTYRENE DERIVATIVES

The solution structure and the aggregation behavior of (E)-2-lithio-1- (2-lithiophenyl)-1-phenylpent-1-ene (1) and (Z)-2-lithio-1-(2-lithioph enyl)ethene (2) were investigated by one- and two-dimensional H-1-,C-1 3-, and Li-6-NMR spectroscopy. In Et(2)O, both systems form dimers whi ch show homonuclear scalar Li-6,6Li spin-spin coupling. In the case of 2, extensive Li-6,H-1 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 p arameters for intra-aggregate exchange in the dimers of 1 and 2 (1 (Et (2)O): Delta H-not equal = 62.6 +/- 13.9 kJ/mol, Delta S-not equal = 5 .8 +/- 14.0 J/mol K, Delta G(not equal) (263) = 61.1 kJ/mol; 2 (dimeth oxyethane): Delta H-not equal = 36.9 +/- 6.5 kJ/mol, Delta S-not equal = -61 +/- 25 J/mol K, Delta G(not equal) (263) = 54.0 kJ/mol) and the thermodynamic parameters for the dimer-monomer equilibrium for 1 (Del ta H-degrees = 26.7 +/- 5.5 kJ/mol, Delta S-degrees = 63 +/- 27 J/mol K), where the monomer is favored at low temperature, were determined b y dynamic NMR studies.