Effect of temperature on the catalytic activity of new symmetrical tetradentate palladium(II) schiff base complexes in copper-free sonogashira reaction; [Kesan suhu terhadap aktiviti pemangkinan kompleks baru paladium(II) tetradentat bes schiff bersimetri dalam tindak balas sonogashira tanpa kuprum]

• Published in: Malaysian Journal of Analytical Sciences
• Main Author: Shahrul Nizam A.; Bahron H.; Tajuddin A.M.
• Format: Article
• Language: English
• Published: Malaysian Society of Analytical Sciences 2019
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085556789&doi=10.17576%2fmjas-2019-2302-09&partnerID=40&md5=f73fa4c908205b92bfe7ae4e33906811

This paper reports the synthesis of two tetradentate Schiff bases namely 2,2'-(((2,2-dimethylpropane-1,3-diyl) bis(azanylylidene))bis(methanylylidene))bis(4-methoxylphenol), LM, and 2,2'-(((2,2-dimethylpropane-1,3-diyl)bis (azanylylidene))bis(methanylylidene))bis(4-nitrophenol), LN. The Schiff bases were reacted with palladium(II) acetate in 1:1 molar ratio yielding two palladium(II) complexes, PdLN and PdLM. The compounds were characterized through elemental analysis, infrared spectroscopy, 1H and 13C Nuclear Magnetic Resonance (NMR), magnetic susceptibility, molar conductivity and melting point. Complexation was indicated to have occurred by the shifting of the characteristic v(C=N), v(C-O) and δ(HC=N) peaks. This was supported by appearance of new peaks of v(M-N) and v(M-O) as well as disappearance of δ(O-H) peak on the IR and 1H NMR spectra of the palladium(II) complexes. The diamagnetic and non-electrolytic nature of the complexes suggested square planar d8 palladium(II) geometry and absence of counter ions, respectively. The catalytic activity of the palladium(II) complexes was investigated for copper-free Sonogashira reaction between iodobenzene and phenylacetylene in dimethylsulfoxide (DMSO) at 80 °C, 100 °C and 140 °C. The conversion of iodobenzene at 12 h reaction time was monitored by GC-FID. At 100 °C, the most active catalyst was PdLN, indicating that the electron withdrawing substituent -NO2, has the ability to enhance catalytic properties of the complexes. At 140 °C, both palladium(II) complexes successfully converted 100% of iodobenzene. © 2019, Malaysian Society of Analytical Sciences. All rights reserved.