Joshi Hemant, Sharma Kamal Nayan, Sharma Alpesh K, Singh Ajai Kumar
Department of Chemistry, Indian Institute of Technology Delhi, New Delhi 110016, India.
Nanoscale. 2014 May 7;6(9):4588-97. doi: 10.1039/c3nr06586c.
PdP2 and Pd4S nanoparticles (NPs) (size: ∼2-6 and 9-15 nm respectively) have been prepared for the first time from a single source precursor complex [Pd(L)Cl2] (1) by its one pot thermolysis at 200 °C in TOP and OA/ODE (1 : 1) respectively. These NPs were stirred with graphene oxide (GO) at room temperature to prepare NP composites, GO-PdP2 and GO-Pd4S. The GO-PdP2 NPs have been synthesized for the first time. The thioether ligand L prepared by reaction of 1,3-dibromo-2-propanol with the in situ generated PhSNa reacts with [PdCl2(CH3CN)2] in CH3CN at 70 °C resulting in 1. The L and 1 have been characterized by (1)H and (13)C{(1)H} NMR and HR-MS. The single crystal structure of 1 determined by X-ray diffraction reveals nearly square planar geometry around the Pd metal centre. The catalytic activities of two palladium nano-phases having phosphorus and sulphur respectively as a co-constituent for Suzuki-Miyaura coupling have been found to be exceptionally different, as PdP2 nanoparticles (NPs) grafted on graphene oxide (GO-PdP2) are significantly more efficient than Pd4S NPs grafted on GO. Without grafting PdP2 and Pd4S both have low efficiency. This is the first report comparing the influence of P and S on the catalytic activity of Pd NPs. TEM, SEM-EDX and powder-XRD have been used to authenticate all NPs. The GO-PdP2 NPs have been found to be efficient catalysts for Suzuki-Miyaura coupling reactions (yield up to 96% in 30 min) at room temperature to 80 °C. Their recyclability has been found up to 6 cycles. In contrast, GO-Pd4S NPs are little active in comparison with GO-PdP2 NPs. The size of NPs and their distribution on GO appear to be key factors affecting the catalytic efficiency of the composite NPs. Leaching of Pd from GO-PdP2 NPs contributes significantly to the catalysis as evidenced by the three phase test, hot-filtration and recycling experiments. The catalysis is almost homogeneous.
首次分别通过在200℃下于TOP以及OA/ODE（1∶1）中对单源前驱体配合物[Pd(L)Cl₂]（1）进行一锅热解制备了PdP₂和Pd₄S纳米颗粒（NPs）（尺寸分别约为2 - 6纳米和9 - 15纳米）。在室温下将这些纳米颗粒与氧化石墨烯（GO）搅拌以制备NP复合材料，即GO - PdP₂和GO - Pd₄S。首次合成了GO - PdP₂纳米颗粒。由1,3 - 二溴 - 2 - 丙醇与原位生成的PhSNa反应制备的硫醚配体L在70℃下于CH₃CN中与[PdCl₂(CH₃CN)₂]反应生成1。L和1已通过¹H和¹³C{¹H}NMR以及HR - MS进行了表征。通过X射线衍射确定的1的单晶结构揭示了Pd金属中心周围近乎正方形平面的几何结构。已发现分别以磷和硫作为共成分的两种钯纳米相对于铃木 - 宫浦偶联反应的催化活性存在显著差异，因为接枝在氧化石墨烯上的PdP₂纳米颗粒（GO - PdP₂）比接枝在GO上的Pd₄S纳米颗粒效率显著更高。在未接枝的情况下，PdP₂和Pd₄S的效率都很低。这是第一份比较P和S对Pd纳米颗粒催化活性影响的报告。使用TEM、SEM - EDX和粉末XRD对所有纳米颗粒进行了鉴定。已发现GO - PdP₂纳米颗粒在室温至80℃下是铃木 - 宫浦偶联反应的高效催化剂（30分钟内产率高达96%）。已发现它们的可循环性高达6次循环。相比之下，GO - Pd₄S纳米颗粒与GO - PdP₂纳米颗粒相比活性较低。纳米颗粒的尺寸及其在GO上的分布似乎是影响复合纳米颗粒催化效率的关键因素。三相测试、热过滤和循环实验证明，GO - PdP₂纳米颗粒中Pd的浸出对催化作用有显著贡献。催化作用几乎是均相的。
