Oligo- and polymerization of ethylene by pyrrolide-imine chromium catalysts bearing pendant O-, S- and N-donor groups. Synthesis, characterization and DFT studies

•New set of chromium(III) catalysts supported by pyrrolide-imine ligands with pendant O-, S- and N-donor groups has been synthesized.•Upon activation with MAO, chromium precatalysts generated active species affording a nonselective distribution of α‐olefins along with the production of varied amounts of polymers.•The nature of the donor atom at the pendant group of the pyrrolide-imine ligand has a strong influence on the product distribution.•DFT calculations suggested that the type of donor atom induce the formation of different species in the reactional medium.