Examining the effect of base, solvent and temperature in heck reaction with the presence of palladium(II)-hydrazone complexes

Palladium(II) chloride is used as a catalyst in various carbon-carbon (C-C) coupling reactions such as the Heck, Sonogashira, Stille, Negishi and Suzuki reactions. This study involved two palladium(II)-hydrazine complexes with different functions namely dichloro-4-methoxy-N’-(3-nitrobenzylidene)benzohydrazide palladium(II) (Pd-L1) and di-4-methoxy-N’-(4-chlorobenzylidene) benzohydrazide palladium(II) (Pd-L2) as catalysts in the Heck reaction. The catalytic activity study of both catalysts in the Heck reaction between 1-bromo-4-nitrobenzene and styrene were investigated. Previously only 50% conversion rate of Heck reaction product can be observed using a similar catalyst. To enhance the catalytic performance as well as to reduce cost and time, an optimised reaction condition is needed. Several parameters have been selected, i.e., the effect of base, solvent and temperature. The excellent catalytic activity of Pd-L1 as a catalyst with 99.87% conversion rate can be achieved using 0.5 mmol % catalyst loading, Na2CO3 as the base, and DMA as the solvent at 50 °C within a 60 min reaction time.