in dichloromethane under N2, Schlenk techniques; Sn-Si compd. added dropwise to suspn. of TaCl5 in CH2Cl2 at 0°C, mixt. warmed to room temp.; volatiles removed under vac., light petroleum added to residue, cooled to -30°C; elem. anal.;

in dichloromethane byproducts: (CH3)2NC2H4N(CH3)2*HCl; under N2, Schlenk techniques; Sn-Si compd. added dropwise to suspn. of TaCl5 in CH2Cl2 at 0°C, mixt. warmed to room temp., volatiles removed under vac., residue dissolved in light petroleum, Me2NC2H4NMe2 addedat 0°C; crystd. at -30°C; elem. anal.;

in diethyl ether byproducts: KCl; under N2, Schlenk techniques; suspn. of K compd. in Et2O treated with soln. of Sn compd. in Et2O at 0°C, mixt. warmed to room temp.; filtered, extd. with Et2O, condensed to cold trap; elem. anal.;