A comparison of the catalytic activities of oxovanadium(IV) and cobalt(II) complex compounds in the oligomerization of ethylene

Abstract

The polymerization and oligomerization of olefins, especially ethylene, is a process of great industrial and scientific importance in polymer chemistry. Catalysts are an essential part of this reaction, and a new report of a catalyst improving this process is worthy of special attention. During this study, nine complex compounds based on oxovanadium(IV) and cobalt(II) ions in combination with organic ligands, e.g., dipicolinic acid, 2,2′-bipyridine, iminodiacetic acid, diglycolic acid, thiodiacetic acid, 1,10-phenanthroline were synthesized. The compound [VO(tda) · 0.5 H2O] is a new complex not previously reported in the literature, and its synthesis and structure are described in this article. The high catalytic activity values in other oligomerization processes in other olefins led us to use the synthesized compounds as precatalysts in the oligomerization reaction. Subsequently, their catalytic activity was also calculated in this process. The obtained oligomerization products were then analyzed by IR, MALDI-TOF-MS, TG, DSC, and SEM techniques to characterize the obtained products and verify the correctness of the oligomerization reaction. Based on the obtained data, the catalytic activity values were compared and the most active catalyst was selected. The best catalyst was a cobalt(II) compound containing an iminodiacetic acid anion and 2,2′-bipyridine in its structure. However, all complexes can be classified as highly active and active catalysts for ethylene oligomerization. The presented studies show novel catalysts that have in their structure other metal ions than those most commonly used in the literature so far. Additionally, coordination compounds of this type have not been previously used in ethylene oligomerization. Moreover, these studies are a source of knowledge on the correlation between catalyst structure and catalytic activity value, thanks to which they provide essential information necessary for the design of next-generation catalysts used for ethylene oligomerization and polymerization.