The Transfer Hydrogenation of Cinnamaldehyde Using Homogeneous Cobalt(II) and Nickel(II) (E)-1-(Pyridin-2-yl)-N-(3-(triethoxysilyl)propyl)methanimine and the Complexes Anchored on Fe₃O₄ Support as Pre-Catalysts: An Experimental and In Silico Approach

• Published in: Molecules
• Main Authors: Fortunate P. Sejie, Olayinka A. Oyetunji, James Darkwa, Isaac N. Beas, Banothile C. E. Makhubela, Nelson Y. Dzade, Nora H. de Leeuw
• Format: Article
• Language: English
• Published: MDPI AG 2023-01-01
• Subjects: Fe₃O₄-immobilised pre-catalysts; transfer hydrogenation; cinnamaldehyde
• Online Access: https://www.mdpi.com/1420-3049/28/2/659
• ISSN: 1420-3049

The imino pyridine Schiff base cobalt(II) and nickel(II) complexes (<b>C1</b> and <b>C2</b>) and their functionalised γ-Fe₃O₄ counterparts (<b>Fe₃O₄@C1</b> and <b>Fe₃O₄@C2</b>) were synthesised and characterised using IR, elemental analysis, and ESI-MS for <b>C1</b> and <b>C2</b>, and single crystal X-ray diffraction for <b>C1</b>, while the functionalised materials <b>Fe₃O₄@C1</b> and <b>Fe₃O₄@C2</b> were characterized using IR, XRD, SEM, TEM, EDS, ICP-OES, XPS and TGA. Complexes <b>C1</b>, <b>C2</b> and the functionalised materials <b>Fe₃O₄@C1</b> and <b>Fe₃O₄@C2</b> were tested as catalysts for the selective transfer hydrogenation of cinnamaldehyde and all four pre-catalysts showed excellent catalytic activity. Complexes <b>C1</b> and <b>C2</b> acted as homogeneous catalysts with high selectivity towards the formation of hydrocinnamaldehyde (88.7% and 92.6%, respectively) while <b>Fe₃O₄@C1</b> and <b>Fe₃O₄@C2</b> acted as heterogeneous catalysts with high selectivity towards cinnamyl alcohol (89.7% and 87.7%, respectively). Through in silico studies of the adsorption energies, we were able to account for the different products formed using the homogeneous and the heterogeneous catalysts which we attribute to the preferred interaction of the C=C moiety in the substrate with the Ni centre in <b>C2</b> (−0.79 eV) rather than the C=O (−0.58 eV).