After 24 h at 200 o C under 1 atm H2, 1 forms an oil in 62 % yield, Entry 1. Analysis of the gas phase before extraction of the oil shows that only 2 % of the polymer is converted to light gases form in this reaction (1.5 CH4 Hf -1 , 0.01 C2H6 Hf -1 , 0.11 C3H6 Hf -1 and 1.1 C4H10 Hf -1 , 1.2 C5H10 Hf -1 ). Increasing H2:Hf ratio to ~1500 results in near complete conversion of iPP to oil (83 %) and light gas (12 %), Entry 2. The zirconium derivative of 1 is also active in this reaction but produces less oil (38 %) and light gas (7 %) than hafnium, Entry 3. High H2 pressures also result in good yields of oil with minimal volatile gas formation (Entries 4 -5). However, at 2 or 5 atm with H2 supplied on demand, conditions that prevent recovery of volatile gases, yields of extracted oils drop (Table , Entries 6 -7). The 1 H NMR data for the extracted oils is largely uninformative, but these spectra contain signals for internal olefins. The intensity of these signals range from ~1:50 to ~1:2000 olefin:C3H6 unit, depending on the conditions (see the SI).