Ancillary Ligands Impact Branching Microstructure in Late-Transition-Metal Polymerization Catalysis

The influence of the labile ligand on the rate of β-hydride elimination (BHE) for salicylaldiminato Ni(II) complexes is shown using a series of precatalysts which differ only in the labile ligand but produce polyethylenes with a range of molecular weights (Mn = 466 to 100 kg mol-1), degrees of branching (1.7 to 7.3 branches/1000 C), and melting temperatures (from 132 to 123 °C) under the same conditions. The use of a weakly coordinating solvent (diethyl ether) was able to suppress this increase in BHE. DFT studies on a related salicylaldiminato Ni(II) complex show that BHE can feasibly occur following recombination of the labile ligand with the catalyst.