in tetrahydrofuran; pentane byproducts: (t-BuP)4; to a suspn. of freshly prepared K2(t-BuP)2*0.5THF in n-pentane a soln. of (t-Bu)2SnCl2 in THF is dropwise added with stirring at -78°C, mixt. is stirred for another 30 min at the same temp. (Ar); mixt. is filtered off, solvent of filtrate is evapd. at -30 to -40°C at 1E-3 Torr, ppt. is recrystd. from n-pentane at -78°C, washed twice with cold pentane and dried at 0°C in high vac., elem. anal.;