in hexane byproducts: KCl; addn. of a soln. of (i-Pr)2NBCl2 to a suspn. of K2(t(-BuP)4) at -78.degrree.C, warming to 10°C within 12 h; filtn., washing with n-hexane, removal of the solvent, cooling to -20°C, filtn., elem. anal.;