A New Bis(NHC)-Pd(II) Complex Supported on Magnetic Mesoporous Silica forSelective Amination of Aryl Halides With Ammonia

Synthesis and identification of a new magnetic SBA-AP-CC-bis(NHC)-Pd(II) catalyst were performed. Thesurface of magnetic SBA-۱۵ was subsequently treated with (۳-aminopropyl) triethoxysilane (APTES), cyanuricchloride (CC), imidazole, and ۲-Bromopyridine. The modified magnetic SBA-۱۵ was then further reacted withseparated prepared trans-[Pd(Cl)۲(SMe۲)۲] complex to give Fe۳O۴@SiO۲-SBA-AP-CC-bis(NHC)-Pd(II) as asupported bis(NHC) complex (Fig. ۱). The obtained catalyst was characterized using Fourier transforminfrared spectroscopy (FTIR), solid ۱۳CNMR, scanning electron microscopy (SEM), X-ray diffractionspectroscopy (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), energydispersiveX-ray analysis (EDS), and Brunauer-Emmett-Teller surface area measurement (BET). Also, X-rayphotoelectron spectroscopy (XPS) confirmed the presence of the Pd(II) complex on the magnetic support.Atomic absorption revealed that the Pd content of the product is ۲.۸۳%wt. (۰.۲۶۶ mmol/g). The supportedcomplex was used as an effective catalyst in the direct monoarylation of ammonia with aryl halides (Fig. ۲).The reaction parameters such as solvent, base, ammonia concentration, and catalyst dosage were optimized.The catalyst was then magnetically separated, washed, and reused several times. The catalyst exhibitednoticeable stability and reusability over six runs without significant loss of catalyst reactivity. The aminationof aryl halides with ammonia catalyzed by magnetic bis(NHC)-Pd(II) does not require a strong base, ligands,and additives. Primary amines are formed as the exclusive products, and di- or tri aryl amines were not formedeven at elevated temperatures.

Keywords:

Heterogeneous catalyst , Supported complex , Monoarylation