Iron, cobalt, and nickel catalysed ethylene oligomerization: recent advances and mechanistic insights

The selective oligomerization of ethylene to linear and branched α-olefins is a key transformation for producing value-added intermediates used in fuels, lubricants, and polymer industries. In this context, late 3d transition metal catalysts, particularly iron, cobalt, and nickel, have gained significant attention due to their earth abundance, cost-effectiveness, and tunable reactivity in homogeneous systems. This review examines the performance of Fe, Co and Ni in ethylene oligomerization. The review presents the principles of ligand design, catalytic performance, and product selectivity. A variety of ligand frameworks, including nitrogen-, phosphorus-, and mixed donor systems, enable control over oligomer distribution from selective dimerization to higher oligomers while suppressing polymer formation. Mechanistically, these systems primarily operate via the Cossee–Arlman pathway involving ethylene insertion and β-hydride elimination, with metal catalysts additionally exhibiting chain-walking behavior. Emerging studies also reveal alternative pathways such as metallacyclic intermediates and cooperative non-classical mechanisms. Overall, this review provides comparative insights into how ligand environment and metal identity govern activity and selectivity, offering guidance for the rational design of next-generation oligomerization catalysts.