in not given low temps.;;

in benzene 15 min at 50 °C, under N2;

in diethyl ether soln. of Mg compd. added to soln. of Zr complex at -78 °C, stirred for 2 h, under N2; evapd. in vac., sublimed for 10 h at 60 °C, identified by NMR;