Iron(II) and cobalt(II) complexes bearing 8-(1-aryliminoethylidene) quinaldines: Synthesis, characterization and ethylene dimerization behavior

The series of bidentate N^N iron(II) and cobalt(II) complexes containing 8-(1-aryliminoethylidene) quinaldine derived ligands, 8-[2,6-(R1)2-4-R2-C6H2NC (Me)]-2-Me-C10H5N, were synthesized and characterized by elemental and spectroscopic techniques. The molecular structures of Co1 (R1 = Me, R2 = H), Co3 (R1 = iPr, R2 = H) and Co4 (R1 = R2 = Me) were confirmed as the distorted tetrahedral by single crystal X-ray diffraction. On treatment with modified methylaluminoxane (MMAO), these complexes exhibited good catalytic activities of up to 5.71 × 105 g mol−1(Fe) h−1 for the ethylene dimerization at 30 °C under 10 atm of ethylene, in which iron pre-catalysts produced butenes with a high selectivity for α-butene. The correlation between metal complexes, catalytic activities and the product formed were investigated under various reaction parameters.

Graphical abstractThe series of iron(II) and cobalt(II) complexes containing 8- (1-aryliminoethylidene)quinaldine derived ligands was synthesized and characterized; upon activation with MMAO, the iron pro-catalysts showed good activities for ethylene dimerization, whereas the cobalt pro-catalysts showed moderate activities.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Iron and cobalt complexes containing 8-(1-aryliminoethylidene)quinaldine derivatives. ► Pre-catalysts, upon treatment with MMAO, exhibit good catalytic activity. ► Major products are butenes, with good selectivity for α-C4.