in tetrahydrofuran; toluene T=40°C; 3 h;

in dichloromethane (Ar), Li-salt added to a suspn. of ZrCl4 in CH2Cl2 at -78°C, warmed to 25°C, 15 h; solvent removed in vacuo, dried in vacuo, extd. with toluene, crystd. at -35°C, recrystd. from CH2Cl2 or THF;

methylaluminoxane in benzene-d6 under Ar, standard Schlenk techniques; solid dichloride Zr complex mixedwith 1 equiv. of Cp2ZrClMe; dissolved in benzene-d6; a minute amt. of s olid methylaluminoxane added; equil. reached within several min; not isolated; monitored by (1)H NMR spectra;