Tungsten pentacarbonyl complexes of cis- and trans-1,2-dimethyldiazene and 1,2-dimethylhydrazine. Preferential oxidation of the coordinated hydrazine to the cis-diazene complex.

Ackermann, Martin N.; Dobmeyer, David J.; Hardy, L.

doi:10.1016/s0022-328x(00)83945-5

Cited by 12 publications

(5 citation statements)

References 19 publications

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“…Half an equivalent of H 2 O is formed per azomethane at 245 K during temperature-programmed reaction, leading support for this argument and ruling out an assignment in terms of intact azomethane (Figure ). Tautomerization of azomethane to formaldehyde methyl hydrazone occurs on Mo(110) 3 and on Pt(111) 6 as well as in transition metal complexes . However, the absence of a ν(N−H) mode near 3300 cm -1 3 indicates that, if formed, the N−H bond is cleaved on Rh(111)-p(2×1)-O.…”

Section: Resultsmentioning

confidence: 99%

“…Tautomerization of azomethane to formaldehyde methyl hydrazone occurs on Mo(110) 3 and on Pt(111) 6 as well as in transition metal complexes. 10 However, the absence of a ν(N-H) mode near 3300 cm -1 3 indicates that, if formed, the N-H bond is cleaved on Rh(111)-p(2×1)-O. All the modes in the spectrum collected after heating a saturation coverage of azomethane on Rh(111)-p(2×1)-O to 300 K can be assigned to CH 2 dNsNCH 3 and atomic oxygen on the surface, based on comparison to the spectra of formaldehyde methyl hydrazone adsorbed on Pt(111) 6 and on Mo(110) 3 and on infrared and Raman data of formaldehyde dimethyl hydrazone.…”

Section: Resultsmentioning

confidence: 99%

“…As on Pt(111), the thermal decomposition of azomethane on Mo(110) was shown to proceed in part through tautomerization to formaldehyde methyl hydrazone (CH 2 NNHCH 3 ). The tautomerization of cis -azomethane to formaldehyde methyl hydrazone has also been observed in both gas-phase and transition metal complex chemistry …”

Section: Introductionmentioning

confidence: 94%

“…The tautomerization of cis-azomethane to formaldehyde methyl hydrazone has also been observed in both gas-phase 9 and transition metal complex chemistry. 10 Herein we report the thermal decomposition of azomethane on Rh(111) and the influence of surface oxygen on the decomposition pathway. On clean Rh(111) azomethane decomposes above 250 K by nitrogen-nitrogen bond scission, yielding H 2 , HCN, C 2 N 2 , N 2 , and C a , similar to reaction on Pd(111) 5 and Pt(111).…”

Section: Introductionmentioning

confidence: 99%

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Control of Reaction Selectivity via Surface Oxygen Coverage: Thermal Decomposition of Azomethane on Rh(111)

et al. 1997

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The thermal decomposition of azomethane on clean and oxygen-covered Rh(111) has been investigated using a combination of temperature-programmed reaction, high-resolution electron energy loss and Fourier transform infrared spectroscopies. On clean Rh(111), azomethane adsorbs molecularly in the trans conformation and is stable on the surface up to 250 K. Above 300 K azomethane reacts exclusively by nitrogen-nitrogen bond scission, yielding gaseous HCN, H 2 , N 2 , and C 2 N 2 . HCN is evolved in four peaks between 300 and 600 K. Adsorbed CN reacts via two competing pathways: recombination to cyanogen and dissociation to adsorbed N, which recombines to gaseous N 2 above 600 K. Adsorbed oxygen inhibits NdN bond breaking, leading to the carbon-nitrogen bond dissociation products CO, CO 2 , and formaldehyde. On Rh(111)-p(2×1)-O (θ O ) 0.5 monolayers), ∼77% of the azomethane reacts via carbon-nitrogen bond scission. The C-N bond breaking is proposed to occur via adsorbed CH 2 dNsNsCH 3 , based on vibrational and temperatureprogrammed reaction data. Subsequent carbon-nitrogen bond cleavage yields gaseous N 2 and is proposed to be accompanied by formation of transient CH 2 and CH 3 , which add to surface oxygen. Methyl would add to oxygen to form methoxy, which rapidly dehydrogenates to produce CO, CO 2 , and H 2 O. Gaseous formaldehyde is proposed to form from addition of CH 2 to oxygen followed by rapid desorption. The variation in the product distributions with oxygen coverage indicates a subtle interplay between the inhibition of nitrogen-nitrogen and C-H bond cleavage by oxygen and is cast in a general framework for hydrocarbon oxidation on Rh surfaces.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Control of Reaction Selectivity via Surface Oxygen Coverage: Thermal Decomposition of Azomethane on Rh(111)

et al. 1997

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“…However, notice that in the gas-phase IR spectrum a N−H stretch band assigned to the tautomer appears as a weak feature; this is not detected when azomethane is adsorbed on Pt(111) , whereas tautomerization on the Pt(111) surface would be energetically more costly . Yet another important surface-dependent route is C−N bond cleavage, which, as revealed by low annealing temperature experiments carried out on the Cu(110) surface, may compete with the NN bond scission .…”

Section: Introductionmentioning

confidence: 99%

Azomethane Decomposition Catalyzed by Pt(111): An Example of Anti-Brönsted−Evans−Polanyi Behavior

2008

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The molecular mechanism of azomethane decomposition on a clean Pt(111) surface has been studied by means of a periodic density functional theory (DFT) approach. Three main elementary steps have been considered, which imply either N-N or C-N scission. The thermodynamic order of stabilities suggests that the most favored reaction involves N-N scission into two methylnitrene NCH 3 adsorbed species. However, it is found that kinetic effects play a crucial role and the most favored reaction appears to be that leading precisely to the less stable reaction product. A similar trend is found for the other two explored reaction pathways: the less the stability of the resulting product, the lower the corresponding energy barrier. Therefore, the reaction mechanism is found to obey an anti-Bro ¨nsted-Evans-Polanyi relationship. Implications for surface-catalyzed reactions are discussed.

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The Coordination Chemistry of Tungsten

Dori

1981

Progress in Inorganic Chemistry

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Tungsten pentacarbonyl complexes of cis- and trans-1,2-dimethyldiazene and 1,2-dimethylhydrazine. Preferential oxidation of the coordinated hydrazine to the cis-diazene complex.

Cited by 12 publications

References 19 publications

Control of Reaction Selectivity via Surface Oxygen Coverage: Thermal Decomposition of Azomethane on Rh(111)

Control of Reaction Selectivity via Surface Oxygen Coverage: Thermal Decomposition of Azomethane on Rh(111)

Azomethane Decomposition Catalyzed by Pt(111): An Example of Anti-Brönsted−Evans−Polanyi Behavior

The Coordination Chemistry of Tungsten

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