690-08-4Relevant articles and documents
Platinum ω-Alkenyl Compounds as Chemical Vapor Deposition Precursors. Mechanistic Studies of the Thermolysis of Pt[CH2CMe2CH2CH= CH2]2in Solution and the Origin of Rapid Nucleation
Liu, Sumeng,Zhang, Zhejun,Abelson, John R.,Girolami, Gregory S.
supporting information, p. 3817 - 3829 (2020/11/13)
The compound cis-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 which 3 reacts upon being heated in solution. In various solvents between 90 and 130 °C, 3 decomposes to generate ～1 equiv of 4,4-dimethylpentenes by addition of a hydrogen atom to the pentenyl ligands in 3. 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 that 3 decomposes 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 ?-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.
Re-based heterogeneous catalysts for olefin metathesis prepared by surface organometallic chemistry: Reactivity and selectivity
Chabanas, Mathieu,Coperet, Christophe,Basset, Jean-Marie
, p. 971 - 975 (2007/10/03)
Herein we describe the catalytic activity of 1, a well-defined Re alkylidene complex supported silica, in the reaction of olefin metathesis. This system is highly active for terminal and internal olefins with initial rates up to 0.7 mol per mol Re per s. It also catalyses the self-metathesis of methyl oleate (MO) without the need of co-catalysts. The turnover numbers can reach up to 900 for MO, which is unprecedented for a heterogeneous Re-based catalyst. Moreover the use of silica as a support can bring major advantages, such as the possibility to use branched olefins like isobutene, which are usually incompatible with alumina-based supports; therefore, the formation of isoamylene from the cross-metathesis of propene and isobutene can be performed. All these results are in sharp contrast to what has been found for other silica- or alumina-supported rhenium oxide systems, which are either completely inactive (silica system) or typically need co-catalysts when functionalised olefins are used. Finally the initiation step corresponds to a cross-metathesis reaction to give a 3:1 mixture of 3,3-dimethylbutene and trans-4,4-dimethylpent-2-ene, and make this catalyst the first generation of well-defined Re-based heterogeneous catalysts.
Isomerisation des radicaux insatures. III. Radicaux α,α,β-, α,β,γ- et α,α,γ-trimethallyles
Deslauriers, Helene,Collin, Guy J.
, p. 3168 - 3173 (2007/10/02)
α,α,β-, α,β,γ-, and α,α,γ-trimethallyl radicals have been generated in the 147.0-nm gas phase photolysis of 2,3,3-trimethyl-1-butene, 3,4-dimethyl-2-pentene, and 2,4-dimethyl-2-pentene, respectively.Under these conditions, the majority of allyl radicals have an internal energy sufficient for further decomposition: they give rise to the formation of various 1,3-dienes and small amounts of either 1,2- or 2,3-dienes.An internal sigmatropic 1,2-hydrogen atom transfer process is part of the proposed mechanism to explain such products.Moreover, the fragmentation of the trimethyl substituted allyl radicals involves the split of one β(C-C) bond, then one β(C-H), and, to a lesser extent, one central C-CH3 bond.
