Secondary Alkene Insertion and Precision Chain-Walking: A New Route to Semicrystalline “Polyethylene” from α‑Olefins by Combining Two Rare Catalytic Events

While
traditional polymerization of linear α-olefins (LAOs)
typically provides amorphous, low Tg polymers,
chain-straightening polymerization represents a route to semicrystalline
materials. A series of α-diimine nickel catalysts were tested
for the polymerization of various LAOs. Although known systems yielded
amorphous or low-melting polymers, the “sandwich” α-diimines 3–6 yielded semicrystalline “polyethylene”
comprised primarily of unbranched repeat units via a combination of
uncommon regioselective 2,1-insertion and precision chain-walking
events.