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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Removal of CO ligands from Pt anionic carbonyls in zeolites by heat treatment in vacuum or in a hydrogen atmosphere and following subsequent recarbonylation
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Removal of CO ligands from Pt anionic carbonyls in zeolites by heat treatment in vacuum or in a hydrogen atmosphere and following subsequent recarbonylation

机译：通过在真空中或在氢气氛中进行热处理，然后再进行羰基化反应，从沸石中的Pt阴离子羰基中去除CO配体

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摘要

Pt tetrammine ions in sodium forms of X, Y, dealuminated Y and EMT were carbonylated to [Pt-3(CO)(6)](n)(2-), these primary complexes were decomposed under vacuum at different temperatures and recarbonylated. It appeared that the recarbonylation also yields multinuclear Pt carbonyls (secondary carbonyls); however, they differ from the parent primary complexes. Secondary carbonyls are characterized by a shift of both the linearly and bridge bonded CO ligands to higher wavenumbers, probably due to the formation of larger anionic or neutral complexes. The upward shift of IR wavenumbers concerns all Pt carbonyls in the above zeolites with Si/Al >2. The increasing basicity of zeolitic oxygens hinders these changes, so that in NaX a part of the secondary carbonyls preserves features of the primary carbonyls, and in KX zeolite only the primary carbonyls appear after recarbonylation. While the vacuum decomposition of Pt anionic carbonyls removes simultaneously both linearly and bridge bonded CO ligands, hydrogen reacts preferentially with the bridge bonded COs, as was previously found in the similarly oxidative treatment. Recarbonylation after hydrogen treatment at temperatures below 130 degreesC results in Pt anionic complexes identical with the primary ones. Pt anionic carbonyls in MCM-41, NaM and NaBEA (prepared by carbonylation of these samples impregnated by Et4NCl and H2PtCl6) cannot be recarbonylated to multinuclear Pt complexes after the decomposition neither under vacuum nor in hydrogen. Carbonylation, decarbonylation and recarbonylation processes were examined using IR spectroscopy. Mass spectrometric analysis of gases released during the vacuum decomposition of Pt-CO complexes was used to help in the characterization of the platinum carbonyls. The UV/Vis spectra of primary as well as of secondary carbonyls were also recorded. [References: 46]
机译：钠形式的X，Y，脱铝的Y和EMT的Pt四胺离子被羰基化为[Pt-3（CO）（6）]（n）（2-），这些初级配合物在真空下于不同温度下分解并重新羰基化。看来，再羰基化还会产生多核的Pt羰基（仲羰基）。但是，它们不同于父级主要复合体。仲羰基化合物的特征是线性键合和桥键合的CO配体都向更高的波数移动，这可能是由于形成了较大的阴离子或中性络合物所致。 IR波数的上移涉及上述Si / Al> 2的沸石中的所有Pt羰基。沸石氧的碱性增加，阻碍了这些变化，因此在NaX中一部分仲羰基保留了伯羰基的特征，而在KX沸石中，仅羰基在重羰基化后出现。尽管Pt阴离子羰基的真空分解同时去除了线性键合和桥键合的CO配体，但氢优先与桥键合的COs反应，如先前在类似的氧化处理中所发现的那样。在低于130摄氏度的温度下进行氢处理后，羰基化反应会生成与初级阴离子相同的铂阴离子络合物。 MCM-41，NaM和NaBEA中的Pt阴离子羰基（由这些被Et4NCl和H2PtCl6浸渍的样品进行羰基化制备）在真空和氢气中分解后都不能再羰基化为多核Pt络合物。使用红外光谱检查羰基化，脱羰基和再羰基化过程。 Pt-CO络合物真空分解过程中释放的气体的质谱分析用于帮助表征羰基铂。还记录了伯羰基和仲羰基的UV / Vis光谱。 [参考：46]

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