Catalytic deuterium exchange reactions with organics. XXVII. The alkylbenzenes on self-activated Group VIII transition metals

1966 ◽  
Vol 19 (12) ◽  
pp. 2299 ◽  
Author(s):  
BD Fisher ◽  
JL Garnett
Keyword(s):  
Transition Metal Oxides ◽  
Exchange Process ◽  
Kinetic Studies ◽  
Platinum Oxide ◽  
Activation Process ◽  
Group Viii ◽  
Exchange Reactions ◽  
Π Complex ◽  
Cis And Trans ◽  
In Cis

Exchange reactions between heavy water and the alkylbenzenes have been investigated on the following self-activated Group VIII transition metal oxides: PtO2,2H2O; PdO; Rh2O3; IrO2,2H2O; RuO2,H2O; ReO2; and Ni2O3. All oxides except Ni2O3 are self-activated by benzene up to 180�. Order of ease of self-activation is Pt > Pd > Rh, Ru, Ir > Re > Ni. Trends in deuteration rates of the alkylbenzenes on self-activated platinum oxide are generally similar to those obtained on hydrogen prereduced platinum. At 130�, some differences in reactivity are observed and these are attributed to reagent displacement effects from the presence of small percentages of dimer (1%) associated with the self-activation process. Compared with hydrogen prereduced catalysts, significant differences in isotope orientation are observed with certain alkylbenzenes on self-activated catalysts. Multiple deuteration effects which are accentuated on self-activated catalysts have been used to confirm isotope orientation and also the participation of a π-complex mechanism for the exchange process. Isomerization and exchange in cis- and trans-stilbenes on self-activated platinum have also been interpreted by the dissociative n-complex substitution mechanism. The advantages of self-activated catalysts in general deuterium and tritium labelling work have been evaluated. Possible correlations between exchange results and electron spin resonance data for charge-transfer adsorption on the above oxides are discussed. Preliminary kinetic studies with self-activation are also reported.

Catalytic deuterium exchange reactions with organics. XXIV. Electron spin resonance studies of adsorption on platinum oxide

1966 ◽  
Vol 19 (4) ◽  
pp. 529 ◽  
Author(s):  
IT Ernst ◽  
JL Garnett ◽  
WA Sollich-Baumgartner
Keyword(s):  
Transition Metal Oxides ◽  
Hydrogen Exchange ◽  
Platinum Oxide ◽  
Active Species ◽  
Paramagnetic Species ◽  
Charge Transfer Complexes ◽  
Severe Reaction ◽  
Exchange Reactions ◽  
Spin Resonance ◽  
Solid Liquid

The formation of paramagnetic species on catalyst surfaces at room temperature through the interaction of polynuclear aromatics in solid, liquid, or solute form with hydrated platinum oxide (PtO2,2H2O) is reported. The results are attributed to the formation of charge-transfer complexes, where the transferred electrons couple weakly, forming essentially a "diradicaloid" complex with a low-lying, thermally populated, triplet state. The effect of solvent, particle size, oxygen, water of crystallization, and temperature on the generation and stability of these e.s.r. active species has been investigated. The possible importance of these paramagnetic species in catalytic self-activation and hydrogen exchange reactions has been discussed. The following Group VIII transition metal oxides gave no e.s.r. spectra under relatively severe reaction conditions such as 1 hr at 120�: PdO; Ru02,2H20; RuO2; Rh2O3; IrO2,2H2O; ReO2; and NiO.

Catalytic deuterium exchange reactions with organics. XIII. Characteristic reactions of the Group VIII transition metals

1965 ◽  
Vol 18 (7) ◽  
pp. 1003 ◽  
Author(s):  
JL Garnett ◽  
WA Sollich
Keyword(s):  
Transition Metal ◽  
Hydrogen Exchange ◽  
Deuterium Oxide ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Group Viii ◽  
Exchange Reactions ◽  
Substitution Mechanism ◽  
Π Complex ◽  
Complex Adsorption

Activation procedures and hydrogen exchange reactions with six Group VIII transition metal catalysts (Pt, Pd, Ru, Rh, Ir, Ni) are reported for three characteristic reaction systems: (i) deuterium oxide/benzene, (ii) deuterium oxide/naphthalene, and (iii) deuterium oxide/n-octane. Results of these exchange reactions indicate that both π-complex adsorption and the dissociative π-complex substitution mechanism previously established for platinum are applicable to other Group VIII transition metal catalysts. For general catalytic labelling with isotopic hydrogen, platinum was found to be the most efficient of the catalysts investigated.

Catalytic deuterium exchange reactions with organics. XLII. The picolines, lutidines, thiophen, and furan on unsupported Group VIII transition metals

1968 ◽  
Vol 21 (5) ◽  
pp. 1221 ◽  
Author(s):  
GE Calf ◽  
JL Garnett
Keyword(s):  
Transition Metals ◽  
Lone Pair ◽  
Nickel Chloride ◽  
Platinum Oxide ◽  
Transition Metal Catalysts ◽  
The Novel ◽  
Group Viii ◽  
Exchange Reactions ◽  
Alkyl Groups ◽  
Nitrogen Lone Pair

The picolines (methylpyridines), lutidines (dimethylpyridines), thiophen, and furan have been exchanged with heavy water on a variety of Group VIII transition metals. Platinum is the most reactive general labelling catalyst for the picolines and lutidines, whereas cobalt catalyses exchange exclusively in the positions α to the nitrogen atom. The labelling pattern in the picolines and lutidines is similar to that of the alkylbenzenes in that (i)positions ortho to a methyl group are severely deactivated and (ii)positions flanked by two methyl groups are completely deactivated. Compensation effects are observed involving steric hindrance to adsorption from the alkyl groups and enhanced strength of adsorption from the nitrogen lone pair. The compensation effect in this charge-transfer adsorption slightly favours the nitrogen lone pair. Thiophen and furan generally do not exchange appreciably with pre-reduced Group VIII transition metal catalysts. Thiophen exchanges rapidly on self-activated platinum oxide whereas self-activated iridium oxide is the most useful for furan. With nickel chloride, furan exchanges exclusively in the or positions. A theory is proposed to account for the novel exchange in both thiophen and furan.

Catalytic deuterium exchange reactions with organics. XL. Pyridine, the quinolines, azines, and aniline on unsupported Group VIII transition metals

1968 ◽  
Vol 21 (4) ◽  
pp. 961 ◽  
Author(s):  
GE Calf ◽  
JL Garnett ◽  
VA Pickles
Keyword(s):  
Charge Transfer ◽  
Transition Metals ◽  
Heavy Water ◽  
Heterocyclic Compounds ◽  
Group Viii ◽  
Borohydride Reduction ◽  
Exchange Reactions ◽  
Catalyst Activation ◽  
Π Complex ◽  
Sodium Borohydride Reduction

Pyridine, the quinolines, pyridazine, pyrimidine, pyrazine, s-triazine, and aniline have been exchanged with heavy water on the following Group VIII transition metals: Fe, Co, Ni, 0s. Ru, Rh, Pd, Ir, and Pt. Three types of catalyst activation have been used, including self-activation, hydrogen and sodium borohydride reduction of the inorganlo salts. Platinum is the most useful catalyst for general exchange whereas cobalt possesses valuable specificity for selective a exchange in a large number of the heterocyclic compounds. A kinetic study of the deuteration of pyridine on platinum has been performed. The exchange results have been rationalized in terms of charge-transfer adsorbed intermediates. E.s.r. has been used to support this conclusion for the interaction between pyridine and potassium chloropalladite. π-Complex mechanisms have been proposed to explain the observed deuteration behaviour.

Catalytic deuterium exchange reactions with organics. XXXI. Accelerative effects of ionizing radiation and ultraviolet light on self-activated platinum oxide

1967 ◽  
Vol 20 (11) ◽  
pp. 2415
Author(s):  
JL Garnett ◽  
A Rains ◽  
PK Wong
Keyword(s):  
Ultraviolet Light ◽  
Diphenyl Ether ◽  
Platinum Oxide ◽  
Exchange Reactions ◽  
Pressure Source ◽  
Exchange Processes ◽  
Radiation Sources ◽  
Π Complex ◽  
Radiation Induced ◽  
Γ Rays

The effect of preirradiation with γ-rays from cobalt-60 and ultraviolet light from a low-pressure source on the exchange between benzene and heavy water in the presence of self-activated platinum oxide has been studied. Both rates of multiple and stepwise exchange processes are accelerated under these conditions. Of 14 oxides examined, including the Group VIII transition metals, platinum is the only one to catalyse exchange up to 130�. Preliminary experiments indicate that radiation-induced oxygen desorption from the surface of the oxide is responsible for the accelerative effect. Internal radiation sources such as tritium oxide also increase initial exchange rates. Cholesterol, naphthalene, dibenzyl, diphenyl, benzoic acid, and diphenyl ether have been studied with tritium oxide. The results can be rationalized in terms of π- complex mechanisms for exchange. A catalytic model for the mechanism of the radiation-induced effect is proposed.

Catalytic deuterium exchange reactions with organics. XII. Further studies in platinum catalyst preparation-the process of self-activation

1965 ◽  
Vol 18 (7) ◽  
pp. 993 ◽  
Author(s):  
JL Garnett ◽  
WA Sollich
Keyword(s):  
Active Sites ◽  
Catalyst Deactivation ◽  
Platinum Catalyst ◽  
Platinum Oxide ◽  
Deuterium Exchange ◽  
Hydrogen Gas ◽  
Distribution Data ◽  
Exchange Reactions ◽  
Π Complex ◽  
Distribution Studies

A new process for the activation of platinum oxide, termed self-activation, is described. This procedure involves the reduction of platinic oxide with an organic compound such as benzene, naphthalene, or n-octane. The potential of the resulting catalyst in deuterium exchange reactions has been evaluated with three characteristic organic compounds, n-octane, naphthalene, and benzene. A comparison has been made in the properties of prereduced catalysts prepared by a self-activation procedure and catalysts activated conventionally with hydrogen gas. For high-temperature exchange reactions ( >90�), the former catalysts are to be preferred since higher final activities of up to 300% may be achieved. The kinetics of self-activation suggest that catalyst deactivation by reagents may be due to modification of active sites. With aromatic compounds, it is proposed that this deactivation occurs through a π-complex interaction. Isotope distribution studies in the labelled benzenes indicate that self-activated, prereduced catalysts, by comparison with hydrogen-activated catalysts, exhibit relatively low M values in relation to their activities. Distribution data are consistent with the explanation that catalyst deactivation by benzene is a process involving the generation of new types of active sites which are more numerous but of lower activity than the original sites. Attempts to stabilize prereduced catalysts by chemical methods were unsuccessful.

scholarly journals Hydrogen Peroxide Oxidation of Coordinated Thiocyanate Ion in cis- and trans-[Coen2NH3NCS]2+: The Preparation and Properties of trans-[Coen2NH3CN]2+

1973 ◽  
Vol 51 (24) ◽  
pp. 4152-4158 ◽  
Author(s):  
Albert Richard Norris ◽  
James William Lennox Wilson
Keyword(s):  
Hydrogen Peroxide ◽  
Spectral Properties ◽  
Peroxide Oxidation ◽  
Reaction Conditions ◽  
Thiocyanate Ion ◽  
Hydrogen Peroxide Oxidation ◽  
Percent Conversion ◽  
Cis And Trans ◽  
In Cis

The hydrogen peroxide oxidation of thiocyanate ion in cis- and trans-[Coen2NH3NCS]2+ leads to the formation of the corresponding cis- and trans-cyanoammine- and diamminebis(ethylenediamine)cobalt-(III) complexes. The spectral properties of the previously unreported trans-[Coe2NH3CN]2+ are reported and compared to the spectral properties of the cis-isomer.Observations are made concerning the reaction conditions which favor a high percent conversion of trans-[Coen2NH3NCS]2+ to trans-[Coen2NH3CN]2+.

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