NH4Cl; silica gel in water; benzene Under Ar, addn. of dry silica gel and a satd. aq. NH4Cl soln. to a benzene soln. of Cp2Hf(C4H8), stirring (ambient temp., 2 h).; Volatile react. products are transferred in vac. with solvent, GC.;

Br2 in benzene-d6 Under Ar, exposing a benzene soln. of Cp2Hf(C4H8) to an atm. containing gaseous bromine, Hf-complex partially pptd.; (1)H NMR.;