Phosphenium Hydride Reduction of [(cod)MX2] (M = Pd, Pt; X = Cl, Br): Snapshots on the Way to Phosphenium Metal(0) Halides and Synthesis of Metal Nanoparticles.
Phosphenium Hydride Reduction of [(cod)MX2] (M = Pd, Pt; X = Cl, Br): Snapshots on the Way to Phosphenium Metal(0) Halides and Synthesis of Metal Nanoparticles.
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DOI：
10.1021/acs.inorgchem.7b00022
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发表时间：
2017-02
影响因子：
4.6
通讯作者：
J. Nickolaus;Dominik A. Imbrich;S. H. Schlindwein;Adrian H. Geyer;M. Nieger;D. Gudat
中科院分区：
文献类型：
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作者：
J. Nickolaus;Dominik A. Imbrich;S. H. Schlindwein;Adrian H. Geyer;M. Nieger;D. Gudat
用 N-杂环鏻氢化物 RNHP-H 还原 [(cod)PtX2]（X = Cl、Br；cod = 1,5-环辛二烯）的结果在很大程度上取决于 N-芳基 R 的空间需求和 X 的性质。 [(cod)PtCl2] 与具有庞大 N-Dipp 基团的 DippNHP-H 反应产生了前所未有的单体鏻金属 (0)由单一膦配体稳定的卤化物 [(DippNHP)(DippNHP-H)PtCl]。鏻单元在磷原子上表现出金字塔配位几何形状，并且根据DFT计算可以被归类为Z型配体。相比之下，[(cod)PtBr2]与空间保护较少的MesNHP-H反应得到了不含供体配体的寡核络合物[{(MesNHP)PtBr}n] (n = 2, 3)的混合物，其是具有μ2-桥接鏻单元的已知钯络合物的结构类似物。研究的所有还原反应都是通过光谱可检测的中间体进行的，其中一些中间体可以通过多核（1H、31P、195Pt）NMR 光谱和计算研究来明确识别。实验结果表明，这些多步过程中的氢化鏻具有配体和氢化物转移试剂的双重功能。与看似简单的配体交换过程相比，对观察到的复杂途径的偏好可能是由于动力学原因。尝试用 Me3P 交换 [(DippNHP)(DippNHP-H)PtCl] 中的大膦配体，通过氯化物从铂迁移到磷，意外异构化为铂 (0) 氯膦络合物，这增强了鏻配体的亲电性质。铂的锍金属(0)卤化物进一步表现出令人惊讶的热稳定性，而钯配合物在二甲基亚砜中温和加热时很容易分解，产生金属纳米颗粒，通过 TEM 和 XRD 研究对其进行了表征。
The outcome of the reduction of [(cod)PtX2] (X = Cl, Br; cod = 1,5-cyclooctadiene) with N-heterocyclic phosphenium hydrides RNHP-H depends strongly on the steric demand of the N-aryl group R and the nature of X. Reaction of [(cod)PtCl2] with DippNHP-H featuring bulky N-Dipp groups produced an unprecedented monomeric phosphenium metal(0) halide [(DippNHP)(DippNHP-H)PtCl] stabilized by a single phosphine ligand. The phosphenium unit exhibits a pyramidal coordination geometry at the phosphorus atom and may according to DFT calculations be classified as a Z-type ligand. In contrast, reaction of [(cod)PtBr2] with the sterically less protected MesNHP-H afforded a mixture of donor-ligand free oligonuclear complexes [{(MesNHP)PtBr}n] (n = 2, 3), which are structural analogues of known palladium complexes with μ2-bridging phosphenium units. All reductions studied proceed via spectroscopically detectable intermediates, several of which could be unambiguously identified by means of multinuclear (1H, 31P, 195Pt) NMR spectroscopy and computational studies. The experimental findings reveal that the phosphenium hydrides in these multistep processes adopt a dual function as ligands and hydride transfer reagents. The preference for the observed intricate pathways over seemingly simpler ligand exchange processes is presumably due to kinetic reasons. The attempt to exchange the bulky phosphine ligand in [(DippNHP)(DippNHP-H)PtCl] by Me3P resulted in an unexpected isomerization to a platinum(0) chlorophosphine complex via a formal chloride migration from platinum to phosphorus, which accentuates the electrophilic nature of the phosphenium ligand. Phosphenium metal(0) halides of platinum further show a surprising thermal stability, whereas the palladium complexes easily disintegrate upon gentle heating in dimethyl sulfoxide to yield metal nanoparticles, which were characterized by TEM and XRD studies.