n-butyllithium in tetrahydrofuran; hexane under Ar; hexane soln. of n-BuLi added to soln. of CH2(C3N2Me2Et)2 in THF at -78 °C; mixt. stirred for 1 h at that temp.; soln. of Ph3SnCl in THF added; mixt. stirred at -78 °C for 1 h, warmed to room temp., and stirred overnight; solvent removed under reduced pressure; residual solid recrystd. from hexane; elem. anal.;