Discovery and Optimization of New Chromium Catalysts for Ethylene Oligomerization and Polymerization Aided by High-Throughput Screening

High throughput screening (HTS) of a 205 member Schiff base salicylaldimine ligand library
derived from salicylaldehydes bearing bulky ortho-substituents, i.e., 9-anthracenyl, 1,4,5,8-tetramethylanthracenyl or triptycenyl, reacted in-situ with (p-tolyl)CrCl2(thf)3, identified two new classes of highly active
chromium based systems for the oligomerization and polymerization of ethylene, respectively. The
polymerization system comprises bidentate ortho-substituted anthracenyl Schiff bases bearing small primary
or secondary alkyl imine substituents. The oligomerization catalysts are based upon tridentate ortho-triptycenyl-substituted Schiff bases with pyridylmethyl or quinolyl substituents. Validation tests confirmed
polymerization productivities of up to 3000 g·mmol-1h-1bar-1 for the polymerization catalyst systems while
the oligomerization catalysts gave productivities up to 10 000 g·mmol-1h-1bar-1. Key catalyst precursors
have been characterized by X-ray crystallography.