A Supported Ziegler-Type Organohafnium Site Metabolizes Polypropylene

Cp₂Hf(CH₃)₂ reacts with silica containing strong aluminum Lewis sites to form Cp₂Hf–¹³CH₃⁺ paired with aluminate anions. Solid-state NMR studies show that this reaction also forms neutral organohafnium and hafnium sites lacking methyl groups. Cp₂Hf–¹³CH₃⁺ reacts with isotatic polypropylene (iPP, M_n = 13.3 kDa; Đ = 2.4; mmmm = 94%; ∼110 C₃H₆/Hf) and H₂ to form oils with moderate molecular weights (M_n = 290–1200 Da) in good yields. The aliphatic oils show characteristic ¹³C{¹H} NMR properties consistent with complete loss of diastereoselectivity and formation of regioirregular errors under 1 atm H₂. These results show that a Ziegler–Natta-type active site is compatible in a common reaction used to digest waste plastic into smaller aliphatic fragments.