A new and efficient N-heterocyclic carbene (NHC)-palladium(II) complex immobilized on graphene oxide (NHC-Pd@GO) has been successfully designed and synthesized. The prepared NHC-Pd@GO heterogeneous catalyst was fully characterized using a combination of fourier transform infrared spectroscopy (FTIR), inductively coupled plasma-optical emission spectroscopy (ICP-OES), energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller surface area analysis (BET). This new air- and moisture-stable NHC-Pd@GO heterogeneous catalytic system was found to be a highly active catalyst in the Suzuki–Miyaura cross-coupling between phenylboronic acid and various aryl halides (bromides/chlorides/iodides) and in the reduction of nitroarenes. These organic transformations were best performed in an aqueous ethanol and aqueous methanol solvent system respectively with low catalyst loading under mild reaction conditions. Furthermore, NHC-Pd@GO heterogeneous catalyst could be recovered easily and reused at least eleven times in Suzuki–Miyaura cross-coupling and nine times in reduction of nitroarenes without any considerable loss of its catalytic activity. The stability and good selectivity of the NHC-Pd@GO heterogeneous catalyst in recycling experiments signify that it could be useful for practical application in various organic transformations.Graphic Abstract

中文翻译：

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氧化石墨烯上固定的 N-杂环卡宾-钯 (II) 络合物作为 Suzuki-Miyaura 交叉偶联和还原硝基芳烃的高效可回收催化剂

已成功设计并合成了一种新型高效的 N-杂环卡宾 (NHC)-钯 (II) 复合物固定在氧化石墨烯上 (NHC-Pd@GO)。使用傅里叶变换红外光谱 (FTIR)、电感耦合等离子体发射光谱 (ICP-OES)、能量色散 X 射线光谱 (EDS)、场-发射扫描电子显微镜 (FESEM)、透射电子显微镜 (TEM)、X 射线粉末衍射 (XRD)、热重分析 (TGA) 和 Brunauer-Emmett-Teller 表面积分析 (BET)。这种新的空气和湿气稳定的 NHC-Pd@GO 多相催化体系被发现是一种高活性催化剂，用于苯硼酸和各种芳基卤化物（溴化物/氯化物/碘化物）之间的 Suzuki-Miyaura 交叉偶联以及还原反应。硝基芳烃。在温和的反应条件下，这些有机转化分别在低催化剂负载的乙醇水溶液和甲醇水溶液系统中进行。此外，NHC-Pd@GO 多相催化剂可以轻松回收并在 Suzuki-Miyaura 交叉偶联中重复使用至少 11 次，在硝基芳烃的还原中重复使用 9 次，而其催化活性没有任何显着损失。