Structure–reactivity relationships in SHOP-type complexes: tunable catalysts for the oligomerisation and polymerisation of ethylene

For over 30 years complexes with the general formula [NiPh(P,O)L] (L = tertiary phosphine; P,O = chelating phosphanylenolato ligand) have been used as highly efficient oligomerisation catalysts suitable for the production of linear alpha-olefins. The same complexes, which are usually referred to as SHOP-type catalysts (SHOP = Shell Higher Olefin Process) can also be used as ethylene polymerisation catalysts, provided they are treated with a phosphine scavenger that selectively removes the tertiary phosphine ligand (L). This Perspective examines the impact of various parameters (influence of the substituents, backbone size, solvent, use of co-catalysts, etc.) on the catalytic outcome of the complexes. Overall, this review shows that the selectivity and activity of the catalyst may be tuned efficiently through directed modification of the P,O chelator.