in toluene byproducts: (CH3)2SnCl2; (N2); using Schlenk techniques; addn. of Me2Sn(C5H4SiMe3-1)2 to ZrCl4 intoluene; stirring under reflux for 24 h; evapn.; addn. of hexane; filtration, concn.; cooling; crystn., elem. anal.;