Homogeneous models for hydrodenitrogenation catalysis

Weller, Keith J.; Fox, Peter A.; Gray, Steven D.; Wigley, David E.

doi:10.1016/s0277-5387(96)00610-9

Cited by 74 publications

(71 citation statements)

References 136 publications

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“…The bond length of the Re(1)-Re(2) edge (3.115(1) Å), which is additionally bridged by the pyridazine ligand, is similar to those found for analogous Re( -H)( -2 -X)Re interactions (see for example the value of 3.116(1) Å in the orthometallated pyridine derivative [Re 3 ( -H) 3 ( -2 -NC 5 H 4 )(CO) 10 ] − 2 [19]). …”

Section: Description Of the Structure Of Anionsupporting

confidence: 73%

“…The mean Re-N bond length in 3 (2.171(12) Å) can not be compared with other Re-pyridazine bond lengths, however it falls in the range observed for analogous complexes in which sp 2 nitrogen atoms are involved in a -2 bridge between two rhenium atoms (see for example the values of 2.168(3), 2.178(9), and 2.18(2) Å found in [Re 3 ( -H) 3 ( -2 -pz)(CO) 9 …”

Section: Description Of the Structure Of Anionmentioning

confidence: 86%

“…3). These compounds have been tentatively formulated as two isomers of the [Re 3 ( -H) 3 ( -2 -N 2 C 4 H 3 )(pymd)(CO) 9 ] − anion (see Scheme 4), on the bases of their hydridic δ values (see Table 1), quite similar to those of the previously known derivative [Re 3 ( -H) 3 ( -2 -NC 5 H 4 )(py)-(CO) 9 ] − , containing a pyridine terminally coordinated on the vertex of the cluster [19]. The two isomers 7a and 7b have been obtained in higher amounts by heating 1 in pyrimidine at 85 • C for 2 h, thus allowing their complete NMR characterisation.…”

Section: Reaction Of 1 With 13-diazinementioning

confidence: 93%

“…(1)) at room temperature giving the anion [Re 3 ( -H) 3 ( -2 -NC 5 H 4 )(CO) 10 ] − (2) containing an orthometallated pyridine molecule bridging a cluster edge.…”

Section: Methodsmentioning

confidence: 99%

“…The study of the reactivity of the six-member aromatic nitrogen heterocycles (azines) with transition metal clusters is an active area of research, due to the possibility of understanding and then optimising the catalytic hydrodenitrification processes [1][2][3][4]. It is known in fact that stable organometallic compounds can provide good models of the reactive intermediates in both homogeneous and heterogeneous catalytic processes.…”

Section: Introductionmentioning

confidence: 99%

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Competition studies on the activation of the C_H bond of diazines by the unsaturated triangular cluster anion [Re3(μ-H)4(CO)10]−

Beringhelli¹

2003

Journal of Molecular Catalysis A: Chemical

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The reactions of the unsaturated cluster anion [Re 3 ( -H) 4 ]1 with 1,3-diazine at room temperature gives two orthometallated isomers 6, corresponding to the metallation of carbon C2 (6a) and C6 (6b), respectively (6b/6a ratio ca. 1.2). Differently from what previously found for the analogous cluster anion containing orthometallated pyridine, the metallation reaction of diazines showed little reversibility, and poor conversion of 5 and 6 to the starting anion 1 was observed after several days under 100 atm of H 2 . Competition experiments, performed by dissolving [NEt 4 ]1 in equimolar mixtures of pyridine/pyrazine or pyridine/pyrimidine, showed that the anion with metallated pyridine was the kinetically preferred product and that at longer times it slowly converted to the derivatives with metallated diazines (5 or 6).

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Section: Description Of the Structure Of Anionsupporting

confidence: 73%

Section: Description Of the Structure Of Anionmentioning

confidence: 86%

Section: Reaction Of 1 With 13-diazinementioning

confidence: 93%

“…(1)) at room temperature giving the anion [Re 3 ( -H) 3 ( -2 -NC 5 H 4 )(CO) 10 ] − (2) containing an orthometallated pyridine molecule bridging a cluster edge.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Competition studies on the activation of the C_H bond of diazines by the unsaturated triangular cluster anion [Re3(μ-H)4(CO)10]−

Beringhelli¹

2003

Journal of Molecular Catalysis A: Chemical

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Hydrodesulfurization & Hydrodenitrogenation

Angelici

2005

Encyclopedia of Inorganic Chemistry

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Hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) are large‐scale commercial processes that occur when petroleum feedstocks are treated with hydrogen (H 2 ) at moderately high pressures and temperatures. During the reactions, the organosulfur and organonitrogen molecules liberate H 2 S and NH 3 . The process results in the production of hydrocarbon fuels with low levels of sulfur and nitrogen. Such fuels are necessary in order to prevent pollution of the atmosphere by sulfur and nitrogen oxides. The HDS and HDN processes are catalyzed by heterogeneous catalysts consisting of molybdenum and cobalt sulfides supported on alumina. Because it is experimentally impossible to determine details of the HDS and HDN processes as they occur on catalyst surfaces, detailed transformations that may occur on the catalyst are modeled by reactions that occur in transition metal complexes that can be fully characterized. As models for the adsorption of thiophenes, benzothiophenes, indoles, and quinolines on metal sites of the catalyst surface, these organosulfur and organonitrogen compounds are coordinated to metals in a variety of complexes. This coordination occurs through the sulfur or nitrogen atom or through π‐bonds in the hydrocarbon portion of the molecules and depends on the electronic state of the metal center. Once coordinated to a metal center, the organosulfur or organonitrogen compound is activated in ways that lead to the cleavage of CS and CN bonds, which are also reactions that occur in the heterogeneous HDS and HDN reactions. Patterns of reactivity of organosulfur and organonitrogen compounds in their metal complexes are used to propose detailed mechanisms for the steps that lead to the formation of H 2 S and NH 3 in the catalytic processes. The validity of these mechanisms has been tested in a range of isotopic labeling, spectroscopic, and reactivity investigations on the heterogeneous catalysts. Not only have the studies of organosulfur and organonitrogen complexes provided a basis for understanding and potentially improving the HDS and HDN processes, they have led to new approaches to the removal of sulfur and nitrogen and to new transformations of organosulfur and organonitrogen compounds.

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Niobium & Tantalum: Organometallic ChemistryBased in part on the article Niobium & Tantalum: Organometallic Chemistry by David E. Wigley which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Xue

2005

Encyclopedia of Inorganic Chemistry

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Homogeneous models for hydrodenitrogenation catalysis

Cited by 74 publications

References 136 publications

Competition studies on the activation of the C_H bond of diazines by the unsaturated triangular cluster anion [Re3(μ-H)4(CO)10]−

Competition studies on the activation of the C_H bond of diazines by the unsaturated triangular cluster anion [Re3(μ-H)4(CO)10]−

Hydrodesulfurization & Hydrodenitrogenation

Niobium & Tantalum: Organometallic ChemistryBased in part on the article Niobium & Tantalum: Organometallic Chemistry by David E. Wigley which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

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