Catalytic activity of Fe(II) and Cu(II) PNP pincer complexes for Suzuki coupling reaction

Abstract

Iron and copper PNP pincer complexes of the type [Fe(L)SO4] and [Cu(L)OCOCH3] are reported and represented as C-1 and C-2 catalyst. Both the complexes were synthesized using bis(diphenylphosphino)pyridine-2,6-diamine [L], and salts of Fe and Cu by direct coordination method. The as synthesized complexes were characterized using FTIR, UV Vis, mass analysis and TGA. The effect of reaction time, catalyst load, solvent and base on the reaction between phenylboronic acid and para substituted bromobenzenes in the presence of the catalysts were investigated for evaluating the catalytic efficiency of the complexes. The results obtained highlight the enhanced C-C coupling reactions with the use of 0.4 mol% of the catalyst C-1 in 14 h and 0.6 mol% of C-2 in 16 h respectively with Cs2CO3 base and ACN as solvent media. Of the two complexes reported, C-1 with iron as catalytically active metal is more stable and active towards coupling which is reflected in its better coupling yields in lesser reaction time compared to copper bearing C-2 complex. Copyright 2017 John Wiley & Sons, Ltd.