Stabilization of Au NPs on symmetrical tridentate NNN-Pincer ligand grafted on magnetic support as water dispersible and recyclable catalyst for coupling reaction of terminal alkyne

A symmetrical tridentate NNN-pincer ligand derived from 2-aminopyridine/cyanuric chloride was covalently grafted onto the surface of modified magnetic support to stabilize Au nanoparticles. Spectroscopic evidence (IR, XRD, EDX, TEM, and XRF) and other analyses (TGA, VSM, and H₂-TPR) confirmed successful immobilization and desired catalyst structure. Catalyst loading of 0.07–0.1 mol% was shown to be very effective in the synthesis of propargylamines through addition of terminal alkynes to amine/aldehyde adduct (A³-coupling). The water-dispersible catalyst allows the use of water as an inexpensive solvent. The high accessibility and robustness of the catalyst enhanced reusability so that no deactivation of catalyst or aggregation of supported Au NPs is observed after seven repeated recycling. Control experiments also showed the true heterogeneous nature of the catalyst in the reaction without significant leaching. All experiments showed that the catalyst is comparable to or even more active than the corresponding species in solution.