in neat (no solvent) slow heating of a mixt. of Sn-compd. and SnCl4 at 190°C for 2 h under N2, further heating at 205°C for 40 min; dissolution of resulting oil in hexane, removing slight turbidity by filtn., cooling to -78°C, filtn., rapidly washing with cold hexane, evapn. of mother liquor yields second crop, elem. anal.;

in diethyl ether 2 h; Reflux;