The role of the ionic radius in the ethylene polymerization catalyzed by new group 3 and lanthanide scorpionate complexes

A series of new monomeric group 3 and lanthanide [N,N,N]-heteroscorpionate triflate-complexes [Ln(OTf)2(cybpamd)(THF)] {Ln = Sc (2), Y (3), La (4), Nd (5), Sm (6), Dy (7), Yb (8); OTf = SO3CF3; cybpamd = N,N′-dicyclohexyl-2,2-bis-(3,5-dimethyl-pyrazol-1-yl)-acetamidinate} has been synthesized and characterized. The behavior of 2–8 as catalysts in olefin polymerization was investigated after proper activation with methylaluminoxane and the comparative results are reported. The activity of the catalytic systems towards ethylene polymerization is affected by the nature of the metal center and linearly grows with the ionic radius, with the exception of the scandium derivative. From DFT calculations it was possible to correlate the activity data with computed properties of the metal–alkyl bonds of the catalytically active species. The very narrow polydispersivities showed that all the considered systems act as single-site catalysts and high-weight linear polyethylene polymers were always obtained.

Graphical abstractNew group 3 and lanthanide [N,N,N]-heteroscorpionate triflate-complexes [Ln(OTf)2(cybpamd)(THF)] have been synthesized. The behavior as polymerization catalysts was investigated and the comparative results are reported.Figure optionsDownload full-size imageDownload high-quality image (78 K)Download as PowerPoint slide