A New Bis-(NHC)-P(II) Complex Supported on Magnetic Mesoporous Silica: An Efficient Pd(II) Catalyst for the Selective Buchwald-Hartwig Monoarylation of Ammonia

We report the synthesis and identification of a new bis(NHC)-Pd(II) catalyst supported on magnetic SBA-15 (Fe3O4@SBA-15). The surface of magnetic SBA-15 was subsequently treated with (3-aminopropyl) triethoxysilane (APTES), cyanuric chloride (CC), imidazole, and 2-bromopyridine. The modified magnetic mesoporous material was then further treated with separately prepared trans-[Pd(Cl)(2)(SMe2)(2)] complex to give Fe3O4@SBA-AP-CC-bis(NHC)-Pd(II) as a supported bis(NHC)-Pd(II) complex. The catalyst was fully characterized by common spectroscopic methods. X-ray photoelectron spectroscopy (XPS) revealed that some imine nitrogens interact with palladium atoms. The supported Pd(II) complex catalyzed the direct monoarylation of ammonia with iodo-, bromo-, and chloroarenes, selectively. The effects of reaction components and parameters were investigated to establish the optimal reaction conditions. The catalyst was separated by a magnet, washed, and applied in the subsequent run. It exhibited noticeable stability and reused over seven catalytic cycles with negligible deactivation. A small Pd leaching (1.04 %) was observed in the first run.