in hexane byproducts: LiCl, Me2NC2H4NMe2; (Ar); standard Schlenk technique; soln. of Sn compd. in hexane was addeddropwise to soln. of Li compd. in hexane at -78°C; mixt. was war med to room temp. over 6 h; stirred overnight; satd. aq. soln. of NH4Cl added at 0°C; septd.; aq. phase extd. (Et2O); combined org. phases washed (H2O); dried (Na2SO4); solvent removed(vac.); residue fractionated; elem. anal.;