ion. The oxidative addition mechanism was originally proposed22i because of the lack of a strong rate dependence on polar factors and on the acidity of the medium. Later, however, the electrophilic substitution mechanism also was proposed. Recently, the oxidative addition mechanism was confirmed by investigations into the decomposition and protonolysis of alkylplatinum complexes, which are the reverse of alkane activation. There are two routes which operate in the decomposition of the dimethylplatinum(IV) complex Cs2Pt(CH3)2Cl4. The first route leads to chloride-induced reductive elimination and produces methyl chloride and methane. The second route leads to the formation of ethane. There is strong kinetic evidence that the ethane is produced by the decomposition of an ethylhydridoplatinum(IV) complex formed from the initial dimethylplatinum(IV) complex. In D2O-DCl, the ethane which is formed contains several D atoms and has practically the same multiple exchange parameter and distribution as does an ethane which has undergone platinum(II)-catalyzed H-D exchange with D2O. Moreover, ethyl chloride is formed competitively with H-D exchange in the presence of platinum(IV). From the principle of microscopic reversibility it follows that the same ethylhydridoplatinum(IV) complex is the intermediate in the reaction of ethane with platinum(II). Important results were obtained by Labinger and Bercaw62c in the investigation of the protonolysis mechanism of several alkylplatinum(II) complexes at low temperatures. These reactions are important because they could model the microscopic reverse of C-H activation by platinum(II) complexes. Alkylhydridoplatinum(IV) complexes were observed as intermediates in certain cases, such as when the complex (tmeda)Pt(CH2Ph)Cl or (tmeda)PtMe2 (tmeda ) N,N,N′,N′-tetramethylenediamine) was treated with HCl in CD2Cl2 or CD3OD, respectively. In some cases H-D exchange took place between the methyl groups on platinum and the, CD3OD prior to methane loss. On the basis of the kinetic results, a common mechanism was proposed to operate in all the reactions: (1) protonation of Pt(II) to generate an alkylhydridoplatinum(IV) intermediate, (2) dissociation of solvent or chloride to generate a cationic, fivecoordinate platinum(IV) species, (3) reductive C-H bond formation, producing a platinum(II) alkane σ-complex, and (4) loss of the alkane either through an associative or dissociative substitution pathway. These results implicate the presence of both alkane σ-complexes and alkylhydridoplatinum(IV) complexes as intermediates in the Pt(II)-induced C-H activation reactions. Thus, the first step in the alkane activation reaction is formation of a σ-complex with the alkane, which then undergoes oxidative addition to produce an alkylhydrido complex. Reversible interconversion of these intermediates, together with reversible deprotonation of the alkylhydridoplatinum(IV) complexes, leads to multiple H-D exchange

Activation of c-h bonds by metal complexes

A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors, such as the specific nature of the active sites, as well as the effect of support, promoters, and reaction feed on catalyst performance and lifetime, are discussed for each catalytic Material. The study compares different catalysts in terms of the reaction mechanism and deactivation pathways and catalytic performance. The duration of the dehydrogenation step depends on the heat content of the catalyst bed, which decreases rapidly due to the endothermic nature of the reaction. Part of the heat required for the reaction is introduced to the reactors by preheating the reaction feed, additional heat being provided by adjacent reactors that are regenerating the coked catalysts.

Catalytic dehydrogenation of light alkanes on metals and metal oxides.

Catalytic removal of NO

Recent developments in transition metal carbides and nitrides as hydrogen evolution electrocatalysts

Hydrogen Spillover. Facts and Fiction

The phenomenon of hydrogen spillover (interphase diffusion of adsorbed hydrogen), the methods for its detection, and the factors influencing it are examined. The common occurrence of the spillover and its role in various adsorption and catalytic processes, particularly in reactions involving hydrogen on multiphase catalysts, are demonstrated. The possible mechanisms of the spillover are analysed. The bibliography includes 189 references.

https://iopscience.iop.org/article/10.1070/RC1997v066n02ABEH000308/pdf

Hydrogen spillover in heterogeneous catalysis

In situ IR spectroscopy of intermediates in heterogeneous oxidative catalysis

The data on various aspects of oxidative conversion of methane published in 1998–2004 are considered.

https://iopscience.iop.org/article/10.1070/RC2005v074n12ABEH001199/pdf

Oxidative conversion of methane

The great interest displayed lately in heterogeneous catalytic reactions of carbon dioxide is caused by two reasons: (1) the necessity to fight the greenhouse effect and (2) the exhaust of carbon raw material sources. Reactions of oxidative transformation of organic compounds of different classes (alkanes, alkenes, and alcohols) with a nontraditional oxidant, carbon dioxide, were studied on oxide catalysts Fe-O, Cr-O, Mn-O and on multicomponent systems based on manganese oxide. The supported manganese oxide catalysts are active, selective, and stable in conversion of the CH[sub 4] + CO[sub 2] mixture into synthesis gas and in oxidative dehydrogenation of C[sub 2] [minus] C[sub 7] hydrocarbons and the lower alcohols. Unlike metal catalysts manganese oxide based catalysts do not form a carbon layer during the reaction.

O. V. Krylov

Papers

Hydrogen spillover in heterogeneous catalysis

In situ IR spectroscopy of intermediates in heterogeneous oxidative catalysis

Oxidative conversion of methane

Catalytic oxidation of hydrocarbons and alcohols by carbon dioxide on oxide catalysts

The regularities in the interaction of alkanes with CO2 on oxide catalysts