Novel cyclohexyl‐substituted salicylaldiminato–nickel(II) complex as a catalyst for ethylene homopolymerization and copolymerization

Abstract

AbstractThe cyclohexyl‐substituted salicylaldiminato–Ni(II) complex [O(3‐C6H11)(5‐CH3)C6H2CHN‐2,6‐C6H3iPr2]Ni(PPh3)(Ph) (4) has been synthesized and characterized with 1H NMR and X‐ray structure analysis. In the presence of phosphine scavengers such as bis(1,5‐cyclooctadiene)nickel(0) [Ni(COD)2], triisobutylaluminum (TIBA), and triethylaluminum (TEA), 4 is an active catalyst for ethylene polymerization and copolymerization with the polar monomers tert‐butyl‐10‐undecenoate, methyl‐10‐undecenoate, and 4‐penten‐1‐ol under mild conditions. The polymerization parameters affecting the catalytic activity and viscosity‐average molecular weight of polyethylene, such as the temperature, time, ethylene pressure, and catalyst concentration, are discussed. A polymerization activity of 3.62 × 105 g of PE (mol of Ni h)−1 and a weight‐average molecular weight of polyethylene of 5.73 × 104 g.mol−1 have been found for 10 μmol of 4 and a Ni(COD)2/4 ratio of 3 in a 30‐mL toluene solution at 45 °C and 12 × 105 Pa of ethylene for 20 min. The polydispersity index of the resulting polyethylene is about 2.04. After the addition of tetrahydrofuran and Et2O to the reaction system, 4 exhibits still high activity for ethylene polymerization. Methyl‐10‐undecenoate (0.65 mol %), 0.74 mol % tert‐butyl‐10‐undecenoate, and 0.98 mol % 4‐penten‐1‐ol have been incorporated into the polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6071–6080, 2004