Platinum ω-Alkenyl Compounds as Chemical Vapor Deposition Precursors. Mechanistic Studies of the Thermolysis of Pt[CH 2 CMe 2 CH 2 CH═CH 2 ] 2 in Solution and the Origin of Rapid Nucleation
Platinum ω-Alkenyl Compounds as Chemical Vapor Deposition Precursors. Mechanistic Studies of the Thermolysis of Pt[CH 2 CMe 2 CH 2 CH═CH 2 ] 2 in Solution and the Origin of Rapid Nucleation
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作为化学气相沉积前体的铂α-烯基化合物。
DOI：
10.1021/acs.organomet.0c00542
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发表时间：
2020
期刊：
影响因子：
2.8
通讯作者：
Girolami, Gregory S.
中科院分区：
文献类型：
--
作者：
Liu, Sumeng;Zhang, Zhejun;Abelson, John R.;Girolami, Gregory S.
化合物顺式-双（η1，η2- 2，2-二甲基-4-烯-1-基）铂，Pt[CH 2CMe 2CH 2CH <$CH2]2（3），是最近发现的化学气相沉积（CVD）前体，用于在各种基底上沉积高度光滑的铂薄膜而没有成核延迟。本文介绍了详细的机理研究的途径，其中3反应后，在溶液中被加热。在90 - 130 °C的各种溶剂中，3通过在3中的戊烯基配体上加成一个氢原子而分解生成101当量的4，4-二甲基戊烯。“额外的”氢原子由其他戊烯基配体脱氢产生;这些脱氢配体中的一些作为甲基取代的亚甲基环丁烷和环丁烯释放。结合同位素标记和动力学研究表明，3分解的烯丙基和烯属C-H键的C-H活化，得到短暂的铂氢化物中间体，然后通过还原消除步骤，形成戊烯产品，但确切的机制是溶剂依赖性的。在C_6F_6中，溶剂缔合发生在C-H键活化之前，而催化反应的速率决定步骤很可能是Pt σ络合物的形成。在烃类溶剂中，C-H键活化前溶剂参与很少，γ-C-H和ε-C-H键活化的速率控制步骤很可能是Pt σ络合物的形成，而δ-C-H键活化的速率控制步骤则是C-H键的裂解或形成。CVD条件下和溶液中的热反应的比较表明，CVD生长的薄膜的高平滑度部分是由于快速成核（这是一个后果的低势垒C → C键解离途径的可用性），部分是由于形成的含碳物种钝化的Pt表面。
The compoundcis-bis(η1,η2-2,2-dimethylpent-4-en-1-yl)platinum, Pt[CH2CMe2CH2CH═CH2]2(3), is a recently discovered chemical vapor deposition (CVD) precursor for the deposition of highly smooth platinum thin films without nucleation delays on a variety of substrates. This paper describes detailed mechanistic studies of the pathway by which3reacts upon being heated in solution. In various solvents between 90 and 130 °C,3decomposes to generate ∼1 equiv of 4,4-dimethylpentenes by addition of a hydrogen atom to the pentenyl ligands in3. The “extra” hydrogen atoms arise by dehydrogenation of other pentenyl ligands; some of these dehydrogenated ligands are released as methyl-substituted methylenecyclobutanes and cyclobutenes. A combination of isotope labeling and kinetic studies suggests that3decomposes by C–H activation of both allylic and olefinic C–H bonds to give transient platinum hydride intermediates, followed by reductive elimination steps to form the pentene products, but that the exact mechanism is solvent-dependent. In C6F6, solvent association occurs before C–H bond activation, and the rate-determining step for thermolysis is most likely the formation of a Pt σ complex. In hydrocarbon solvents, the solvent is little involved before C–H bond activation, and the rate-determining step is most likely the formation of a Pt σ complex only for γ-C–H and ε-C–H bond activation, but cleavage or formation of a C–H bond for δ-C–H bond activation. A comparison of the thermolysis reactions under CVD conditions and in solution suggests that the high smoothness of the CVD-grown films is due in part to rapid nucleation (which is a consequence of the availability of low-barrier C═C bond dissociation pathways) and in part to the formation of carbon-containing species that passivate the Pt surface.