in tetrahydrofuran byproducts: Si(CH2CH2CH2SiMe2CH2Li)4; (N2 or Ar); using Schlenk techniques; treatment of Si(CH2CH2CH2SiMe2CH2SnBu3)4 with 4.0 equiv. of BuLi at 0°C for 30 min; evapn. of solvent, extn. with pentane;