in toluene A pressure vessel is filled with a soln. of (C5Me5)Hf(COT)Cl in toluene and charged with 95 atm of H2, the reaction mixture is heated to 70°C and stirred for 4 days under N2.; Excess H2 is released, hot soln. is transferred into a Schlenk vessel, cooling of the soln. to room temp., a bright yellow ppt. is formed, solvent is decanted, ppt. is redissolved (hot toluene), slow cooling to -30°C.;