Hydrogenation of aromatics under mild conditions on transition metal complexes in zeolites. A cooperative effect of molecular sieves

1995 ◽  
Vol 32 (3-4) ◽  
pp. 313-318 ◽  
Author(s):  
A. Corma ◽  
M. Iglesias ◽  
F. S�nchez
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Molecular Sieves ◽  
Cooperative Effect ◽  
Mild Conditions

scholarly journals CATALYTIC FIXATION OF CARBON DIOXIDE TO FORMIC ACID BY TRANSITION-METAL COMPLEXES UNDER MILD CONDITIONS

1976 ◽  
Vol 5 (8) ◽  
pp. 863-864 ◽  
Author(s):  
Yoshio Inoue ◽  
Hitoshi Izumida ◽  
Yoshiyuki Sasaki ◽  
Harukichi Hashimoto
Keyword(s):  
Carbon Dioxide ◽  
Transition Metal ◽  
Formic Acid ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Mild Conditions ◽  
Fixation Of Carbon Dioxide

C-Methylation Of Organic Substrates: A Comprehensive Overview. Part Ii. Methanol As Methylating Agent. A Case Of Catalysis Versatility

2020 ◽  
Vol 17 ◽  
Author(s):  
Saad Moulay
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Molecular Sieves ◽  
Acid Sites ◽  
Lewis Base ◽  
Molar Ratio ◽  
Organic Substrates ◽  
Solid Catalysts ◽  
The Impact

: The present account surveys the results of the myriad of works on C-methylation of organic substrates with methanol as an eco-friendly methylating agent. The innumerable reports on this issue reveal the widespread use of a set of solid catalysts such as molecular sieves, zeolites, metal phosphates, metal oxides and transition metal complexes, to accomplish such methylation. One related facet was the impact of the numbers of Brønstëd acid sites, of Lewis acid sites, and of Lewis base sites present in solid catalysts, such as zeolites, their ratios, and their strengths that affect the distribution of the methylation products and their selectivities. Also, specific surface area and porosity for some solid catalysts such as zeolites play additional roles in the overall reaction. Not only these properties of a catalyst that influence the methylation outcome but also the temperature, space velocity (WHSV, LHSV, GSHV), weight of catalyst per reactant flow rate (W/F), time of stream (TOS), and methanol/substrate molar ratio. The treated substrates herein discussed were aromatic hydrocarbons (benzene, biphenyls, naphthalenes, toluene, xylenes), alkenes, phenolics (phenol, cresols, anisole), N-heteroarenes, carbonyls, alcohols, and nitriles. Methylation of benzene affords not only toluene as main product but also polymethylated benzenes (xylenes, pseudocumene, hexamethylenebenzene, and also ethylbenzene as a sidechain product). Also, toluene is sensitive to the reaction conditions, giving rising to ring methylation and to sidechain one (ethylbenzene and styrene), besides the formation of benzene as a disproportionation product. Wealth of results from the methylation of phenolic compounds bears witness to the interest of different investigators in this special research. As to these phenolics, concurrent O-methylation inevitably parallels the C-methylation, and the selectivity of the latter one remains depended on the above-cited factors; ortho-cresol and 2,6-xylenol have been the main C-ring methylated phenols. Methylation of olefins with methanol over solid catalysts, leading to higher olefins, is of a great interest. The chemistry involved in the methylation of N-heteroarenes such as pyridines, indoles, and pyrroles is significant. Application of the methylation protocols, using methanol as a reagent and transition metal complexes as catalysts, to ketones, esters, aldehydes, nitriles, and alcohols, ends up with some important molecules such as acrylonitrile (a monomer) and isobutanol (a biofuel).

C-methylation of organic substrates: A comprehensive overview. Part iiia. Methanol as a methylating agent. A case of catalysis versatility

2021 ◽  
Vol 18 ◽  
Author(s):  
Saad Moulay
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Molecular Sieves ◽  
Acid Sites ◽  
Lewis Base ◽  
Side Chain ◽  
Organic Substrates ◽  
Solid Catalysts ◽  
The Impact

: The present account surveys the results of the myriad of works on the C-methylation of organic substrates with methanol as an eco-friendly methylating agent. The innumerable reports on this issue reveal the widespread use of a set of solid catalysts such as molecular sieves, zeolites, metal phosphates, metal oxides and transition metal complexes to accomplish such methylation. One related facet was the impact of the numbers of Brønstëd acid sites, Lewis acid sites, and Lewis base sites present in solid catalysts, such as zeolites, ratios, and strengths that affect the distribution of the methylation products and their selectivities. Moreover, specific surface area and porosity for some solid catalysts, such as zeolites, play additional roles in the overall reaction. Not only do these catalyst properties influence the methylation outcome, but the temperature, space velocity (WHSV, LHSV, GSHV), weight of catalyst per reactant flow rate (W/F), time of stream (TOS), and methanol/substrate molar ratio also do. The treated substrates herein discussed were aromatic hydrocarbons (benzene, biphenyls, naphthalenes, toluene, xylenes), alkenes, phenolics (phenol, cresols, anisole), N-heteroarenes, carbonyls, alcohols, and nitriles. Methylation of benzene affords not only toluene as the main product but also polymethylated benzenes (xylenes, pseudocumene, hexamethylenebenzene, and also ethylbenzene as a side-chain product). Furthermore, toluene is sensitive to the reaction conditions, giving rise to ring methylation and side-chain one (ethylbenzene and styrene), besides the formation of benzene as a disproportionation product. A number of results from the methylation of phenolic compounds bear witness to the interest of different investigators in this special research. As to these phenolics, concurrent O-methylation inevitably parallels the C-methylation, and the selectivity of the latter one remains dependent on the above-cited factors; ortho-cresol and 2,6-xylenol have been the main C-ring methylated phenols. Methylation of olefins with methanol over solid catalysts, leading to higher olefins, is of great interest. The chemistry involved in the methylation of N-heteroarenes, such as pyridines, indoles, and pyrroles, is significant. Application of the methylation protocols, using methanol as a reagent and transition metal complexes as catalysts to ketones, esters, aldehydes, nitriles, and alcohols, ends up with some important molecules such as acrylonitrile (a monomer) and isobutanol (a biofuel).

Übergangsmetallkomplexe mit Schwefelliganden, LXI / Transition Metal Complexes with Sulfur Ligands, LXI

1991 ◽  
Vol 46 (5) ◽  
pp. 673-681 ◽  
Author(s):  
Dieter Sellmann ◽  
Klaus Höhn ◽  
Matthias Moll
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Unpaired Electron ◽  
Redox Reactions ◽  
Similar Process ◽  
Mild Conditions ◽  
No Release

18 and 19 electron NO complexes with the [Fe'buS5'] moiety ('buS5'2- = dianion of 2,2′-bis-(2-mercapto-3,5-di-tertiary-butylphenylthio)diethylsulfide) have been isolated and converted reversibly into each other. The unpaired electron in meso-[Fe(NO)′buS5'], meso-1, is delocalized over the whole molecule and occupies an orbital that is antibonding with respect to Fe– N and Fe–S bonds. Consequently, the NO ligand is readily substituted under mild conditions. In contrast, the 18 electron complex meso-[Fe(NO)'buS5']PF6, meso-2, is entirely inert towards substitution. To our knowledge the exchange of NO by CO in meso-1 via meso-2 is the first example, in which NO is displaced by CO in an isolable NO complex. The NO release from meso-1 via meso-2 can be considered a model for reversible NO bonding in sulfur coordinated metal centres of nitrogenase. It is shown that one-electron redox reactions make stable Fe–NO bonds labile, and the reversible coordination and decoordination of NO in nitrogenase may be induced by a similar process.

Bor-stabilisierte Ν,Ο-Carbene, II Röntgenstrukturanalyse von (trans-4,5-Dimethyloxazolidin-2-yliden)triphenylbor und N-Alkyliengen / Boron Stabilized Ν,Ο-Carbenes, II X-Ray Structure of (trans-4,5-Dimethyloxazolidin-2-ylidene)triphenylboron and N-Alkylations

1989 ◽  
Vol 44 (8) ◽  
pp. 917-922 ◽  
Author(s):  
Wolf Peter Fehlhammer ◽  
Hans Hoffmeister ◽  
Borislav Boyadjiev ◽  
Thomas Kolrep
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Structure Analysis ◽  
Transition Metal Complexes ◽  
X Ray ◽  
Mild Conditions

The X-ray structure analysis of (trans-4,5-dimethyloxazolidin-2-ylidene)triphenylboron reveals a stereochemistry of the carbene ligand which is almost identical with that in transition metal complexes. Deprotonation of triphenylboron stabilized oxazolidin-2-ylidenes with NaH leads to (oxazolin-2-ato)borates, which have been N-alkylated with [R3O+][BF4~] or RI under mild conditions.

N-Heterocyclic Carbenes: Generation under Mild Conditions and Formation of Group 8–10 Transition Metal Complexes Relevant to Catalysis

1996 ◽  
Vol 2 (7) ◽  
pp. 772-780 ◽  
Author(s):  
Wolfgang A. Herrmann ◽  
Martina Elison ◽  
Jakob Fischer ◽  
Christian Köcher ◽  
Georg R. J. Artus
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Heterocyclic Carbenes ◽  
Mild Conditions
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