Methyl benzenesulfonate: Complexes Synthesis and its Applications in Ethylene Polymerization

General Description

Methyl benzenesulfonate complexes refer to compounds formed by the coordination of methyl benzenesulfonate with metal ions. These complexes exhibit unique physical and chemical properties that make them valuable in various applications. A study describes the synthesis of methyl benzenesulfonate complexes through a single-step process, starting with the creation of imino-methyl benzenesulfonate ligands L1-L6. These ligands were successfully complexed with palladium to form alkyl-palladium(II) complexes C1-C3. The complexes were then evaluated for ethylene polymerization, with C1 showing activity at 80°C and 95°C being the optimal temperature. Complexes 4 and 5 exhibited higher activities than C1-C3, suggesting potential for further enhancement through modifications. Overall, the research demonstrates a straightforward method for complex synthesis and highlights the potential of these complexes in catalysis for polyethylene production.

Figure 1. Methyl benzenesulfonate

Complexes Synthesis

A recent study describes the synthesis of methyl benzenesulfonate complexes through a single-step process. The researchers successfully synthesized six imino-methyl benzenesulfonate ligands, labeled as L1-L6, by condensing various amino-benzoic acids with aldehydes in the presence of an acidic-substituent ortho to the amine. The reaction between sodium 2-formylbenzenesulfonate and different amines, such as aniline, 4-methoxy aniline, 2-methoxy aniline, 2,6-diisopropyl aniline, 2-methylpropan-2-amine, and (3s,5s,7s)-adamantan-1-amine, yielded the desired ligands L1-L6 in good to excellent yields. The identity of these ligands was confirmed using spectroscopic and analytical methods, including proton and carbon NMR, high-resolution mass spectrometry (HRMS), and infrared (IR) spectroscopy. The spectroscopic data showed characteristic shifts in chemical peaks, confirming the formation of imine ligands L1-L6. For example, the imine proton chemical shift ranged from 9.50 ppm for L1 to 9.08 ppm for L4, indicating the influence of electron-donating substituents. Furthermore, the ligands L1-L6 were complexed with palladium to form neutral alkyl-palladium(II) complexes C1-C3. The successful complexation was verified using similar spectroscopic and analytical techniques. The synthetic utility of these imino-methyl benzenesulfonate-ligated palladium complexes was demonstrated by their application in an ethylene polymerization reaction. Overall, the study presents a facile and efficient method for the synthesis of a small library of imino-methyl benzenesulfonate ligands and their subsequent complexation with palladium. The precise characterization of the ligands and complexes provides a solid foundation for further investigations and potential applications in catalysis and materials science. ¹

Applications in Ethylene Polymerization

Methyl benzenesulfonate complexes have shown promising applications in ethylene polymerization, a process used to produce polyethylene. Methyl benzenesulfonate complexes, specifically C1, C2, and C3, were evaluated for their performance in ethylene polymerization. In a study, ethylene polymerization was carried out using a high-pressure reactor charged with C1 in a solvent mixture of DCM and toluene. At a temperature of 80 °C, C1 exhibited the ability to polymerize ethylene, resulting in the formation of polyethylene material. The activity of the catalyst increased with higher temperatures, and 95 °C was found to be the optimal temperature for polymerization. The effect of ethylene pressure on the polymerization process was also investigated. It was observed that the highest activity was achieved at 25 bar ethylene pressure. The polyethylene produced was characterized using various analytical techniques, including NMR, MALDI-ToF-MS, and DSC. Interestingly, the MALDI-ToF-MS analysis revealed that the palladium catalyst remained bound to the polyethylene chain, indicating its effectiveness in the polymerization process. Furthermore, additional Methyl benzenesulfonate complexes, such as complex 4 and complex 5, were also evaluated for ethylene polymerization. Methyl benzenesulfonate complex 4 demonstrated better performance than C1, while Methyl benzenesulfonate complex 5 exhibited significantly higher activity compared to C1. Although Methyl benzenesulfonate complexes C1-C3 showed activity in ethylene polymerization, they underperformed compared to parent complexes 4 and 5. The study suggested that steric and electronic tailoring, along with donor group modifications, may enhance the catalytic performance of these complexes. In summary, methyl benzenesulfonate complexes, specifically C1-C3, have demonstrated the ability to catalyze the polymerization of ethylene to produce polyethylene. Further research and modifications to these complexes may lead to the development of more efficient catalysts for ethylene polymerization in industrial applications. ²

Reference

1. Deshmukh SS, Gaikwad SR, Mote NR, M M, Gonnade RG, Chikkali SH. Neutral Imino-Methyl Benzenesulfonate-Ligated Pd(II) Complexes and Implications in Ethylene Polymerization. ACS Omega. 2019; 4(5): 9502-9511.

2. Johnson LK, Mecking S, Brookhart M. Copolymerization of Ethylene and Propylene with Functionalized Vinyl Monomers by Palladium(II) Catalysts. J Am Chem Soc. 1996; 118: 267–268.

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