Efficient Suppression of Chain Transfer and Branching via C (s)‐Type Shielding in a Neutral Nickel(II) Catalyst

An effective shielding of both apical positions of a neutral Ni(II) active site is achieved by dibenzosuberyl groups, both attached via the same donors’ N‐aryl group in a C (s)‐type arrangement. The key aniline building block is accessible in a single step from commercially available dibenzosuberol. This shielding approach suppresses chain transfer and branch formation to such an extent that ultrahigh molecular weight polyethylenes (5×10(6) g mol(−1)) are accessible, with a strictly linear microstructure (<0.1 branches/1000C). Key features of this highly active (4.3×10(5) turnovers h(−1)) catalyst are an exceptionally facile preparation, thermal robustness (up to 90 °C polymerization temperature), ability for living polymerization and compatibility with THF as a polar reaction medium.