in tetrahydrofuran argon atmosphere, room temperature, passing acetylene into THF, addn. of a soln. of Mg-compound followed by addn. of a soln. of Sn-compound, heating for 2 h, stirring for 1.5 h at 55-60°C; addn. of pentane, decanting liquid layer, removing solvent, distn. (vac.), elem. anal.;