Synthesis of hydrophilic palladium complex immobilized on nano magnetic support and its catalytic acitivity in coupling reactions

The development of environmentally more benign and efficient synthetic method continues to be a central goal of current research in chemistry. Along this line, it is better that catalysis be associated with both catalyst reusability and green reaction media [1]. Generally, homogeneous catalysis can provide excellent yield, while heterogeneous catalysis offers the advantages of simplified product separation and recycling of the catalyst [2]. These properties make heterogeneous catalysts as suitable candidates for green chemistry catalysis due to their great stability, durability, cost effectiveness, and diminishing heavy metal environmental contamination [3]. To increase the efficiency of heterogeneous catalysts, additives such as phase transfer agents [4], polymers [5], surfactants [6], cyclodextrins [7], organic co-solvents [8] or ionic liquids [9] have been used. A more desirable approach, which avoids using any additives, is designing hydrophilic heterogeneous catalysts. Along this line, in this work, a new heterogeneous palladium complex of supported on nanomagnetic γ-Fe2O3 (Scheme 1) was synthesized and characterized by HRTEM, SEM, XRD, XPS, ICP, FT-IR, TGA, VSM and elemental analysis. The synthesized catalyst was used successfully as a new Pd catalyst for Suzuki and Hiyama coupling reactions of aryl iodides, bromides and chlorides with phenylboronic acid and phenylsilanes. The true heterogeneous magnetically-recyclable catalyst can be separated easily using a magnetic bar and reused six times without any drastic loss of its catalytic activity. Using water as a green solvent, facile catalyst recovery and reuse, simple work-up and not requiring any additive or promoter make this method favourable from the environmental and economic point of view for the coupling reactions.