Sterically Controlled Self-Assembly of a Robust Multinuclear Palladium Catalyst for Ethylene Polymerization

The self-assembly and reactivity of a robust multinuclear Pd catalyst based on the sterically expanded phosphine-bis-arenesulfonate ligand PPh(2-SO3–-4,5-(OMe)2-Ph)2 (OPO2–, 2) are described. The reaction of Li2[2] with (COD)PdMeCl and 4-(5-nonyl)-pyridine (py′) generates the tetranuclear complex {(OPO-Li)PdMe(py′)}4Li2Cl2 (3) in which four (phosphine-sulfonate)PdMe(py′) units are arranged around the periphery of a Li4S4O12·Li2Cl2 cage. The Pd atoms in 3 are arranged in pairs with a Pd–Pd distance of 6.6 A within each pair. 3 is more resistant to disassembly to Pd1 species than previously studied {(OPO-Li)PdMe(py)}4 compounds based on Li4S4O12 cages. 3 is a single-site catalyst for the polymerization of ethylene to high-molecular weight polyethylene hexanes suspension at 80 °C.