Vanadium(V) imido chlorides and n-propoxides - Towards a rational design of vanadium imido precatalysts for ethylene polymerization

Vanadium(V) imido complexes are widely used in olefin polymerization and oligomerization. In this report we present the synthesis and the results of ethylene polymerization studies for a series of vanadium(V) imido complexes with various substituents at the imido fragment. All complexes have been prepared in nearly quantitative yields by the interaction of N-sulfinylamines with VOCl3 or VO(OnPr)(3) and characterized using H-1, C-13, V-51 NMR and elemental analysis. The solid-state structure of complex V(=NArOMe)(OnPr)(3) was established using X-ray. Vanadium(V) imido chlorides and npropoxides exhibited similar moderate catalytic activities (320-547 kg(PE).mol(V)(-1).h(-1).atm(-1)). The maximum catalytic activity (547 kg(PE).mol(V)(-1).h(-1).atm(-1)) was achieved for (adamantylimido)vanadium(V) n-propoxide. The molecular weights of the resulting polyethylenes were higher (M-v = 3.7-6.5.10(5) Da) for imido npropoxide complexes as compared to the corresponding imido chlorides (M-v = 2.1-5.5.10(5) Da). The localization of DFT calculated HOMO on imide nitrogen was proposed to favor the reaction between imide ligand and Et2YAlCl used as activator. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study presents the synthesis of a series of vanadium(V) imido complexes with various substituents on the imido fragment, and their results in ethylene polymerization. The complexes were characterized using NMR and elemental analysis, with propoxide complexes showing better catalytic activities and higher molecular weights compared to the corresponding chloride complexes. The study suggests that the DFT calculated HOMO on the imide nitrogen may play a role in the activation of the complexes.