in pentane (argon); stirring (-30°C, 30 min); standing (-78°C, 1-2 d), decantation, concn. at -30°C, standing (-78°C, 24 h), decantation, evapn. (high vac., -20°C);

T=13°C; 1) 1 h, -40 deg C, 2) 2 h, r. t.;

phosphorus trichoride in tetrahydrofuran byproducts: (CH3)3SnCl; stirring at -78°C for 30 min; stirring at -78°C for 1 h; heating to -30°C; removing of the solvent; residue dissolved in n-pentane; cooling to -78°C;; filtration;;