Work

Cobalt (II) and Nickel (II) Complexes of Substituted (Pyrazolyl)amine Ligands: Structural Characterization and Ethylene Oligomerization Studies

Year: 2025

Type: article

Abstract: ABSTRACT The cobalt (II) and nickel (II) complexes of the general formula [Co(L1)Cl2] (Co1), [Co(L2)Cl2] (Co2), [Co(L3)Cl2] (Co3), [Ni(L1)Br2] (Ni1), and [Ni(L2)Br2] (Ni2) were prepared by the reaction of either CoCl2 or [NiBr2(DME)] metal salts with the (pyrazolyl)amine ligands, N‐benzyl‐2‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)ethan‐1‐amine (L1), 2‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐N‐(2‐methyl‐benzyl)ethan‐1‐amine (L2) and 2‐(3,5‐diphenyl‐1H‐pyrazol‐1‐yl)‐N‐(2‐methylbenzyl)ethan‐1‐amine (L3). The new compounds were characterized using NMR spectroscopy (for ligands), IR spectroscopy, mass spectrometry, elemental analysis and single crystal X‐ray crystallography. The bidentate coordination modes of ligands L1‐L3 to form monometallic complexes was confirmed by the solid‐state structures of Co1, Co2, Co3, and Ni1. Activation of these complexes with either EtAlCl2 or MAO resulted in the formation of highly active ethylene oligomerization catalysts (up to 103 kg [oligomers] mol−1[catalyst]·h−1), to afford predominantly C4 and C6 oligomers. The nature and coordination chemistry of the complexes was found to influence the catalytic performance. In general, nickel (II) complexes were more active than the corresponding cobalt (II) analogues. Significantly, cobalt (II) complexes were highly selective (99%) towards the formation of C4 oligomers.

Source: Applied Organometallic Chemistry

DOI: 10.1002/aoc.70171

Authors: Francis K. Migwi, Ayanda Madlala, George S. Nyamato, Stephen O. Ojwach

Institutions: University of KwaZulu-Natal, University of Embu

Language: English

Topic: Organometallic Complex Synthesis and Catalysis

Subfield: Organic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,430

Funders: National Research Foundation, Inyuvesi Yakwazulu-Natali