Ethylene Oligomerization and Polymerization by Palladium(II) Methyl Complexes Supported by Phosphines Bearing a Perchlorinated 10-Vertex closo-Carborane Anion Substituent

The synthesis and ethylene reactivity of the zwitterionic Pd methyl complexes (κ2-P,Cl-PR2CB9Cl9)PdMe(THF) (7, R = iPr; 8, R = Ph) and (κ2-P,O-P(o-OMe-Ph)2CB9Cl9)PdMe(THF) (9), which contain the first phosphines appended with anionic 10-vertex perchlorinated closo-carboranes, are described. Complexes 7 and 8 oligomerize ethylene (23 °C, 2 atm) to a Schulz–Flory distribution of C4–C10 olefins with TOFs of ca. 8000 and 1800 t.o./h, respectively. 8 is ca. 4 times more active than the analogous (κ2-P,F-ortho-PPh2C6H4BF3)PdMe(L) (L = pyridine or collidine) system reported by Jordan and Piers, which produces butenes. Complex 9 reacts with ethylene to yield polyethylene wax (Mn ca. 1000, Đ ca. 1.5) that is similar to commercial Fischer–Tropsch waxes. The activities of 7–9 are independent of ethylene pressure and the presence of B(C6F5)3, suggesting that the catalyst resting state is the corresponding (PR2CB9Cl9)PdR(H2C═CH2) adduct. The molecular weights of the oligomer/polymer products are independent of ethylen...