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Heterogeneous reductions of (homohypostrophene)dialkylplatinum(II) complexes provide a useful system for the study of intermediate surface alkyls on platinum [1] (1991)

Lee, T. Randall ; Whitesides, George M.

Springer

Catalysis letters 9 (1991), S. 461-472

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ISSN: 1572-879X

Keywords: Heterogeneous ; hydrogenation ; surface alkyls ; platinum

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract This paper reports a comparison of the ethyl moieties generated on the surface of platinum black during the heterogeneous, platinum-catalyzed hydrogenations of (1,5-cyclooctadiene)diethylplatinum(II) ((COD)PtEt2), of (homohypostrophene)diethylplatinum(II) ((HOP)PtEt2), and of ethylene using D2 in ethyl alcohol-d. In reductions of the platinum complexes, the π-olefin and σ-alkyl organic ligands are converted to alkanes by reaction of the intermediate surface alkyls with surface hydrides, and the platinum(II) becomes part of the platinum(0) surface. These reductions are characterized by two kinetic regimes: one in which the rate of reaction is limited by the mass transport of hydrogen to the surface of the catalyst (the mass transport limited regime, MTL), and one in which the rate is limited by a reaction on the surface of the catalyst (the reaction rate limited regime, RRL). In the RRL regime, the isotopic compositions of the ethanes-d n produced from the reductions of the platinum complexes and of ethylene suggest that the surface ethyls (Et *) generated from each precursor have similar relative rates of isotopic exchange (and thus of C-H bond activation) and of reductive elimination as ethane. In the MTL regime, the Et * derived from each precursor have different reactivities: the Et* generated from (HOP)PtEt2 have reactivities that are more similar to the Et * generated from ethylene than do the Et * generated from (COD)PtEt2.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00764838

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Modeling organic surfaces with self-assembled monolayersThis work was funded in part by the Office of Naval Research, by (DARPA/URI), and by the National Science Foundation through grants to the Harvard University Materials Research Laboratory. (1989)

Bain, Colin D. ; Whitesides, George M.

Weinheim : Wiley-Blackwell

Advanced Materials 1 (1989), S. 110-116

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ISSN: 0935-9648

Keywords: Interfacial Structure ; Wettability ; Long-Chain Thiols ; on Gold ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: The interfacial properties of organic materials are of critical importance in many applications, especially the control of wettability, adhesion, tribology, and corrosion. The relationships between the microscopic structure of an organic surface and its macroscopic physical properties are, however, only poorly understood. This short review presents a model system that has the ease of preparation and the structural definition required to provide a firm understanding of interfacial phenomena. Long-chain thiols, HS(CH2)nX, adsorb from solution onto gold and form densely packed, oriented monolayers. By varying the terminal functional group, X, of the thiol, organic surfaces can be created having a wide range of structures and properties. More, complex systems can be constructed by coadsorbing two or more thiols with different terminal functional groups or with different chain lengths onto a common gold substrate. By these techniques, controlled degrees of disorder can be introduced into model surfaces. We have used these systems to explore the relationships between the microscopic structure of the monolayers on a molecular and supramolecular scale and their macroscopic properties. Wettability is a macroscopic interfacial property that has proven of particular interest.

Additional Material: 6 Ill.